DEFF Research Database (Denmark)
Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans
2009-01-01
Current models to predict heat, air and moisture (HAM) conditions in buildings assume constant boundary conditions for the temperature and relative humidity of the neighbouring air and for the surface heat and moisture transfer coefficients. These assumptions may introduce errors in the predicted HAM conditions. The paper focuses on the influence of the interior surface heat and moisture transfer coefficients, and investigates its effect on the hygrothermal performance. The parameter study showed that the magnitude of the convective surface transfer coefficients have a relatively large influence on the predicted hygrothermal conditions at the surface of a building component and on the heat and vapour exchange with the indoor environment.
Critical thickness of an optimum extended surface characterized by uniform heat transfer coefficient
Leontiou, Theodoros
2015-01-01
We consider the heat transfer problem associated with a periodic array of extended surfaces (fins) subjected to convection heat transfer with a uniform heat transfer coefficient. Our analysis differs from the classical approach as (i) we consider two-dimensional heat conduction and (ii) the base of the fin is included in the heat transfer process. The problem is modeled as an arbitrary two-dimensional channel whose upper surface is flat and isothermal, while the lower surface has a periodic array of extensions/fins which are subjected to heat convection with a uniform heat transfer coefficient. Using the generalized Schwarz-Christoffel transformation the domain is mapped onto a straight channel where the heat conduction problem is solved using the boundary element method. The boundary element solution is subsequently used to pose a shape optimization problem, i.e. an inverse problem, where the objective function is the normalized Shape Factor and the variables of the optimization are the parameters of the Sch...
PCB mass transfer coefficients determined by application of a water surface sampler.
Tasdemir, Yücel; Odabasi, Mustafa; Holsen, Thomas M
2007-01-01
A water surface sampler (WSS) was employed in combination with greased surface deposition plates (GSDPs) to measure the particulate dry deposition and gas exchange of polychlorinated biphenyls (PCBs) in Chicago, IL. Vapor phase PCB fluxes were calculated by subtracting the particulate fluxes obtained from GSDPs from total (particulate+gas) fluxes obtained from the WSS. Vapor phase PCB fluxes were divided by ambient air concentrations measured with a high volume sampler to calculate overall gas phase PCB mass transfer coefficients (K(G)). The calculated average PCB MTC was 0.54+/-0.47 cm s(-1). This experimentally determined average gas phase overall mass transfer coefficient, K(G), agreed well with the ones reported from studies using similar techniques and agreed well with modeled values obtained using MTC correlations developed for the WSS. PMID:16997350
International Nuclear Information System (INIS)
Convective heat transfer at exterior building surfaces has an impact on the design and performance of building components such as double-skin facades, solar collectors, solar chimneys and ventilated photovoltaic arrays, and also affects the thermal climate and cooling load in urban areas. In this study, an overview is given of existing correlations of the exterior convective heat transfer coefficient (CHTC) with the wind speed, indicating significant differences between these correlations. As an alternative to using existing correlations, the applicability of CFD to obtain forced CHTC correlations is evaluated, by considering a cubic building in an atmospheric boundary layer. Steady Reynolds-averaged Navier-Stokes simulations are performed and, instead of the commonly used wall functions, low-Reynolds number modelling (LRNM) is used to model the boundary-layer region for reasons of improved accuracy. The flow field is found to become quasi independent of the Reynolds number at Reynolds numbers of about 105. This allows limiting the wind speed at which the CHTC is evaluated and thus the grid resolution in the near-wall region, which significantly reduces the computational expense. The distribution of the power-law CHTC-U10 correlation over the windward and leeward surfaces is presented (U10 = reference wind speed at 10 m height). It is shown that these correlations can be accurately determined by simulations with relatively low wind speed values, which avoids the use of excessively fine grids for LRNM, and by using only two or three discrete wind speed values, which limits the required number of CFD simulations.
Kumar, Varun; Kumar, Manoj; Shakher, Chandra
2014-09-20
In this paper, the local convective heat transfer coefficient (h) is measured along the surface of an electrically heated vertical wire using digital holographic interferometry (DHI). Experiments are conducted on wires of different diameters. The experimentally measured values are within the range as given in the literature. DHI is expected to provide a more accurate local convective heat transfer coefficient (h) as the value of the temperature gradient required for the calculation of "h" can be obtained more accurately than by other existing optical interferometric techniques without the use of a phase shifting technique. This is because in digital holography phase measurement accuracy is expected to be higher. PMID:25322139
International Nuclear Information System (INIS)
This paper describes a non-invasive, non-destructive, transient inverse measurement technique that allows one to determine internal heat transfer coefficients and rib positions of real gas turbine blades from outer surface temperature measurements after a sudden flow heating. The determination of internal heat transfer coefficients is important during the design process to adjust local heat transfer to spatial thermal load. The detection of rib positions is important during production to fulfill design and quality requirements. For the analysis the one-dimensional transient heat transfer problem inside of the turbine blade's wall was solved. This solution was combined with the Levenberg-Marquardt method to estimate the unknown boundary condition by an inverse technique. The method was tested with artificial data to determine uncertainties with positive results. Then experimental testing with a reference model was carried out. Based on the results, it is concluded that the presented inverse technique could be used to determine internal heat transfer coefficients and to detect rib positions of real turbine blades.
International Nuclear Information System (INIS)
HTPGB1 calculates from experimental data the variation in heat transfer coefficient round a cyclindrical surface. The structure within the cylindrical surface is assumed to consist of a series of concentric annuli for any one of which the physical properties and volume generation of heat remain constant, but may vary from one annulus to another. Conduction of heat along the cylinder is assumed negligible. However, an adjustment for the localised longitudinal conduction effects associated with ribbed surfaces may be included. The information provided by the program can be used in the prediction of round pin temperature variations in a reactor from out-of-pile tests. It is essential for obtaining the correct interpretation of experimental data when the reduction of temperature differences by thermal conduction within the surface is different in the reactor and the experiment. (author)
Odabasi, Mustafa; Sofuoglu, Aysun; Holsen, Thomas M.
A sampling program was conducted between June and October 1995 in Chicago, IL using a modified water surface sampler (WSS) and dry deposition plates to measure the particulate dry deposition and gas exchange of PAHs. Oxygen transfer experiments were also conducted to evaluate the collection properties of the WSS for gas-phase compounds. Gas-phase fluxes were determined by subtracting the dry deposition plate fluxes (particulate) from WSS fluxes (particulate+gas). These fluxes were divided by concurrently measured ambient concentrations to obtain overall gas phase mass transfer coefficients. Two different two-film models, one developed based on experiments performed with the WSS and, one previously published, were compared to these results. Experimentally determined average gas phase overall mass transfer coefficient ( Kg) for seven PAHs was 0.74±0.52 cm s -1. Experimental Kg values agreed well with those predicted by the model developed for WSS. The values predicted by previously proposed models were within a factor of 3 of the experimental ones.
Wang, Binbin; Liao, Qian; Fillingham, Joseph H.; Bootsma, Harvey A.
2015-03-01
Recent studies suggested that under low to moderate wind conditions without bubble entraining wave breaking, the air-water gas transfer velocity k+ can be mechanistically parameterized by the near-surface turbulence, following the small eddy model (SEM). Field measurements have supported this model in a variety of environmental forcing systems. Alternatively, surface divergence model (SDM) has also been shown to predict the gas transfer velocity across the air-water interface in laboratory settings. However, the empirically determined model coefficients (? in SEM and c1 in SDM) scattered over a wide range. Here we present the first field measurement of the near-surface turbulence with a novel floating PIV system on Lake Michigan, which allows us to evaluate the SEM and SDM in situ in the natural environment. k+ was derived from the CO2 flux that was measured simultaneously with a floating gas chamber. Measured results indicate that ? and c1 are not universal constants. Regression analysis showed that ?˜log>(?>) while the near-surface turbulence dissipation rate ? is approximately greater than 10-6 m2 s-3 according to data measured for this study as well as from other published results measured in similar environments or in laboratory settings. It also showed that ? scales linearly with the turbulent Reynolds number. Similarly, coefficient c1 in the SDM was found to linearly scale with the Reynolds number. These findings suggest that larger eddies are also important parameters, and the dissipation rate in the SEM or the surface divergence ?' in the SDM alone may not be adequate to determine k+ completely.
Amano, Ken; Haga, Ryoichi; Murakami, Sei
2008-06-01
For mammalian cell culture, getting a continuous supply of oxygen and extracting carbon dioxide are primary challenges even in the most modern biopharmaceutical manufacturing plants, due to the low oxygen solubility and excessive carbon dioxide accumulation. In addition, various independent flow and mass transfer characteristics in the culture tanks vessel make scale-up extremely difficult. One method for overcoming these and providing rational optimization is solving the fluid and mass transport equations by numerical simulation. To develop a simulation program, it is decisively important to know mass transfer coefficients of gaseous species in the culture tank. In this study, oxygen mass transfer coefficients are measured using a beaker with a sparger and impellers. In order to investigate the formulation of the mass transfer coefficients, the turbulent flow statistics is calculated by a CFD code for all cases, and the expressions of the mass transfer coefficients are established as functions of the statistics. Until now, the expression by Kawase is known in this field. This expression becomes a function only of energy dissipation rate epsilon. It does not coincide with the conventional experimental fact that mass transfer coefficient is proportional power 0.5 of impeller rotation speed. The new mass transfer coefficient is dependent on both of energy dissipation rate epsilon and turbulent flow energy k. It satisfies the relation of power of 0.5 of impeller rotation speed. PMID:18347829
International Nuclear Information System (INIS)
A critical review of the assumptions, theoretical foundations, and supporting experimental evidence for the analytical procedures in current use for evaluation of the effects of artificial surface roughening on friction factor and Stanton number is provided. Recommendations are given concerning the application of these procedures to rough rod bundles. A new method is demonstrated for determination of the slope and intercept of the universal logarithmic dimensionless velocity distribution law for fully rough flow past roughened surfaces without the need for experimental measurement of the velocity profile. The slope is shown to vary with the nature of the roughened surface and to deviate significantly from the slope for turbulent flow past smooth walls in some cases. It is further shown that the intercept, which is a boundary condition equivalent to the roughness parameter for friction, is independent of the width of the velocity profile. A similar method is developed for determination of the slope and intercept of the temperature distribution law, but additional experimental investigation is required before the efficacy of this application can be conclusively established
International Nuclear Information System (INIS)
In fire engineering analysis, one of the open problem is the transfer of thermal parameters obtained by fire CFD model to FEM models for structural analysis. In this study the new useful concept of “Adiabatic Surface Temperature” or more commonly known as AST, introduced by Wickström, is investigated. The adiabatic surface temperature offers the opportunity to transfer both thermal information of the gas and the net heat flux to the solid phase model, obtained by CFD analysis. In this study two CFD analyses are carried out in order to evaluate the effect of emissivity and of convective heat transfer coefficient to determine the AST. First one CFD analysis simulating a fire scenario, “conjugate heat transfer”, with a square steel beam exposed to hot surface is carried out to calculate AST, heat convective coefficient and temperature field in the beam. Second one, a conductive analysis is carried out on “standalone beam” imposing a third type boundary condition on its boundaries assuming the AST, evaluated in the conjugate analysis, as external temperature. Different heat convective coefficients are imposed on the beam walls. The comparison between results obtained by means of the two proposed analyses shows the use of AST as transfer thermal parameter between CFD (Computational Fluid Dynamic) and FEM (Finite Element Method) models is appropriate when the convective heat transfer coefficient is properly evaluated. -- Highlights: ? An open problem is to transfer parameters obtained by thermal to structural models. ? The useful concept of “Adiabatic Surface Temperature” (AST) is investigated. ? The AST use is right for properly evaluated convective heat transfer coefficient
Hippensteele, Steven A.; Russell, Louis M.; Torres, Felix J.
1987-01-01
Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.
International Nuclear Information System (INIS)
Of the major radioactive selenium isotopes, Se-79, a beta emitter with a half-life of about 1.1 million years, is of special interest because it is one of the most important radionuclides for the long-term dose assessment of radioactive waste disposal. This radionuclide can reach human beings through several transfer paths in the environment. To predict Se-79 behavior from the environment to human beings, it would be useful to obtain the following information: stable Se concentration in environmental samples; soil-soil solution distribution coefficient (Kd); and soil-to-plant transfer factor (TF). In the present study, stable Se concentrations in river water, soil and crop samples collected in Japan, Kds and TFs were obtained. The results showed that geometric mean (GM) concentrations of river water, soil and crops were 0.057 ?g/L (range: ds for paddy field soil and upland field soil samples were 116 and 67, respectively, whereas GMs of TFs for brown rice and upland field crops were 0.066 and 0.024, respectively. Probably due to longer growing period and different water management in the paddy fields for brown rice compared to those for upland field crops, the TF would be high in brown rice. (authors)
Heat transfer coefficient for boiling carbon dioxide.
DEFF Research Database (Denmark)
Knudsen, Hans JØrgen HØgaard; Jensen, Per Henrik
1998-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has not been compared with correlation's.
Wind heat transfer coefficient in solar collectors in outdoor conditions
Energy Technology Data Exchange (ETDEWEB)
Kumar, Suresh; Mullick, S.C. [Centre for Energy Studies, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016 (India)
2010-06-15
Knowledge of wind heat transfer coefficient, h{sub w}, is required for estimation of upward losses from the outer surface of flat plate solar collectors/solar cookers. In present study, an attempt has been made to estimate the wind induced convective heat transfer coefficient by employing unglazed test plate (of size about 0.9 m square) in outdoor conditions. Experiments, for measurement of h{sub w}, have been conducted on rooftop of a building in the Institute campus in summer season for 2 years. The estimated wind heat transfer coefficient has been correlated against wind speed by linear regression and power regression. Experimental values of wind heat transfer coefficient estimated in present work have been compared with studies of other researchers after normalizing for plate length. (author)
Transfer coefficients in elliptical tubes and plate fin heat exchangers
International Nuclear Information System (INIS)
Mean transfer coefficients in elliptical tubes and plate fin heat exchangers were determined by application of heat and mass transfer analogy in conjunction with the naphthalene sublimation technique. The transfer coefficients are presented in a dimensionless form as functions of the Reynolds number. By using the least squares method analytical expressions for the transfer coefficients were determined with low scattering. (E.G.)
Hippensteele, S. A.; Russell, L. M.; Torres, F. J.
1987-01-01
Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.
Radionuclide transfer to animal products: revised recommended transfer coefficient values
Energy Technology Data Exchange (ETDEWEB)
Howard, B.J. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LAI 4AP (United Kingdom)], E-mail: bjho@ceh.ac.uk; Beresford, N.A.; Barnett, C.L. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LAI 4AP (United Kingdom); Fesenko, S. [International Atomic Energy Agency, 1400 Vienna (Austria)
2009-03-15
A compilation has been undertaken of data which can be used to derive animal product transfer coefficients for radionuclides, including an extensive review of Russian language information. The resultant database has been used to provide recommended transfer coefficient values for a range of radionuclides to (i) cow, sheep and goat milk, (ii) meat (muscle) of cattle, sheep, goats, pigs and poultry and (iii) eggs. The values are used in a new IAEA handbook on transfer parameters which replaces that referred to as 'TRS 364'. The paper outlines the approaches and procedures used to identify and collate data, and assumptions used. There are notable differences between the TRS 364 'expected' values and the recommended values in the revised Handbook from the new database. Of the recommended values, three milk values are at least an order of magnitude higher than the TRS 364 values (Cr, Pu (cow) Pu (sheep)) and one milk value is lower (Ni (cow)). For meat, four values (Am, Cd, Sb (beef) I (pork)) are at least an order of magnitude higher than the TRS 364 values and eight values are at least an order of magnitude lower (Ru, Pu (beef), Ru, Sr, Zn (sheep), Ru, Sr (pork), Mn (poultry)). Many data gaps remain.
Radionuclide transfer to animal products: revised recommended transfer coefficient values
International Nuclear Information System (INIS)
A compilation has been undertaken of data which can be used to derive animal product transfer coefficients for radionuclides, including an extensive review of Russian language information. The resultant database has been used to provide recommended transfer coefficient values for a range of radionuclides to (i) cow, sheep and goat milk, (ii) meat (muscle) of cattle, sheep, goats, pigs and poultry and (iii) eggs. The values are used in a new IAEA handbook on transfer parameters which replaces that referred to as 'TRS 364'. The paper outlines the approaches and procedures used to identify and collate data, and assumptions used. There are notable differences between the TRS 364 'expected' values and the recommended values in the revised Handbook from the new database. Of the recommended values, three milk values are at least an order of magnitude higher than the TRS 364 values (Cr, Pu (cow) Pu (sheep)) and one milk value is lower (Ni (cow)). For meat, four values (Am, Cd, Sb (beef) I (pork)) are at least an order of magnitude higher than the TRS 364 values and eight values are at least an order of magnitude lower (Ru, Pu (beef), Ru, Sr, Zn (sheep), Ru, Sr (pork), Mn (poultry)). Many data gaps remain
Analysis of the heat transfer coefficient during potato frying
Costa, Rui M; Oliveira, Fernanda A. R.; Delaneya, Olivia; Gekas, Vassilis
2001-01-01
The objective of this work was to study the dependence of the heat transfer coefficient (h) on the water loss rate of potato during frying. An indirect method was used where a metal piece with the same geometry of the potato pieces was placed on top of various potato samples at different frying times, and its temperature was recorded for 20–30 s. Another method consisted of direct recording of the temperature within a potato slice, close to the surface. Water loss rate was estimated by image ...
Humble, Leroy V; Lowdermilk, Warren H; Desmon, Leland G
1951-01-01
An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through smooth tubes for an over-all range of surface temperature from 535 degrees to 3050 degrees r, inlet-air temperature from 535 degrees to 1500 degrees r, Reynolds number up to 500,000, exit Mach number up to 1, heat flux up to 150,000 btu per hour per square foot, length-diameter ratio from 30 to 120, and three entrance configurations. Most of the data are for heat addition to the air; a few results are included for cooling of the air. The over-all range of surface-to-air temperature ratio was from 0.46 to 3.5.
International Nuclear Information System (INIS)
Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained
Local heat transfer coefficient for turbulent flow in rod bundles
International Nuclear Information System (INIS)
The correlation of the local heat transfer coefficients in heated triangular array of rod bundles, in terms of the flow hydrodynamic parameters is presented. The analysis is made first for fluid with Prandtl numbers varying from moderated to high (Pr>0.2), and then extended to fluids with low Prandtl numbers (0.004< Pr<0.2). Results of temperature and velocity fields distribution of slip coefficients and local heat transfer coefficients are obtained. (E.G.)
Correlation of heat transfer coefficient for quench front
International Nuclear Information System (INIS)
The heat transfer coefficient at the quench front during quenching is one of the important parameters for researching the quenching processes, one of the main variables for the movement velocity of quenching front, too. A transient hot-patch test technique and unsteady state two-dimensional numerical technique is adopted to investigate the heat transfer coefficient at the quench front under the top-quenching, low pressure and low mass flux in a tube. Based on a suitable physical model, a multi-variables nonlinear regression method is used to analysis the effect of relevant parameters on the heat transfer coefficient and obtained the final empirical correlation under the experimental condition
Determination of the surface drag coefficient
DEFF Research Database (Denmark)
Mahrt, L.; Vickers, D.
2001-01-01
This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches. The roughness length corresponding to the usual Monin-Obukhov stability functions decreases with increasing wind speed. This dependence on wind speed cannot be eliminated by adjusting the stability functions. If physical, the decrease of the roughness length with increasing wind speed might be due to the decreasing role of viscous effects and streamlining of the vegetation, although these effects cannot be isolated from existing atmospheric data. For weak winds, both the mean flow and the stress vector often meander significantly in response to mesoscale motions. The relationship between meandering of the stress and wind vectors is examined. For weak winds, the drag coefficient can be sensitive to the method of calculation, partly due to meandering of the stress vector.
International Nuclear Information System (INIS)
In this study, we aimed to realize a parametric determination of the convective heat transfer coefficient of a gasoline engine on both the in-cylinder and jacket sides. The combustion products have been determined as a function of excess air coefficient. Cylinder temperature and pressure have been calculated with a simplistic model based on the First Law of Thermodynamics. The in-cylinder heat transfer coefficient is evaluated by using two different expressions; one a specific form of Annand's equation and the other the Woschni equation. Newton's convective heat transfer equation has been utilized to obtain the heat transfer coefficient between the engine block and the cooling water. This process is based on some temperature measurements at various locations in the cooling space, as the distance between the tip of the temperature sensor and the inner cylinder surface is varied for each location. We determined values of both coefficients for various engine parameters
A study on the evaporative heat transfer coefficient in PCCS
International Nuclear Information System (INIS)
In advanced nuclear reactors, the passive containment cooling has been suggested in AP600 to enhance the safety. The passive cooling has two mechanisms, air natural convection and water cooling with evaporation. To conform the coolability of PCCS, many works have been performed experimentally and numerically. In this study, the water cooling test was performed in scaled down segment type PCCS facility, which have the same configuration with AP600 prototype containment, to obtain the evaporative heat transfer coefficients. In the experiment air-steam mixture temperature and velocity, relative humidity and wall heat flux are measured. The local heat transfer coefficients are calculated and averaged through the vertical plate part of the facility. To convince the measured heat transfer coefficients, an analytical model for the local evaporative heat transfer is developed and compared with experimental data. From the comparison, the predicted coefficients are quite well agreed with measured values
Evaluation of heat transfer and drag coefficients for iron meteorites
International Nuclear Information System (INIS)
According to the observed deceleration of 15 superschmidt meteors generated by iron meteoroids of heat transfer coefficients ? and drag coefficients ? were evaluated assuming the quasi-continuous fragmentation. It is shown that for meteoroid initial masses M1 g ? strongly decreases by M increase reaching values ? ? 0,1 at M ? 10 g. The square dependence of the reactive part of drag coefficient on the velocity instead of linear lows is obtained
Subcooled boiling heat transfer on a finned surface
International Nuclear Information System (INIS)
Experimental and numerical studies have been performed to determine the heat transfer coefficients from a finned cylindrical surface to subcooled boiling water. The heat transfer rates were measured in an annular test section consisting of an electrically heated fuel element simulator (FES) with eight longitudinal, rectangular fins enclosed in a glass tube. A two-dimensional finite-element heat transfer model using the Galerkin method was employed to determine the heat transfer coefficients along the periphery of the FES surface. An empirical correlation was developed to predict the heat transfer coefficients during subcooled boiling. The correlation agrees well with the measured data. (6 figures) (Author)
DEFF Research Database (Denmark)
Rong, Li; Nielsen, Peter V.
2010-01-01
This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 × 104 to 5.43 × 104 (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.
Heat transfer coefficient in serpentine coolant passage for CCDTL
Energy Technology Data Exchange (ETDEWEB)
Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.
1998-12-31
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
3D measurements and numerical computations of heat transfer coefficients on spheres in an array
International Nuclear Information System (INIS)
The focus of this paper is to investigate the heat transfer coefficient distributions on the spheres in a three-dimensional (3-D) array. This arrangement is an essential geometry in pebble bed reactors (PBRs) that are generally adopted in the chemical and the nuclear engineering. Understanding the thermal-hydraulic characteristics of the pebbles is important for the design of reactors. Using the transient liquid crystal technique, an experimental device is set up to measure the transient wall temperature on the surface of spheres arranged in an array, as heated air flows across. Based on the measured temperature distributions on the sphere surfaces, the heat transfer coefficient can be derived. A 3-D transient computational fluid dynamics (CFD) model with different turbulence models is also developed and assessed using the measured heat transfer coefficient distributions. Five turbulence models are considered in this study: the standard k-? low-Re, AKN k-? low-Re, standard k-? two-layer, realizable k-? two-layer, and v2-bar-f turbulence models, respectively. Comparisons of the predicted heat transfer coefficient distributions and those in the experimental data reveal that the v2-bar-f turbulence model is more suitable for simulating flow and heat transfer characteristics in a sphere array. In addition, the beneficial effect of Rein on the heat transfer coefficient distribution is captured by both experimental measurements and CFD predictions. (authors)
Determination of the wall heat transfer coefficient in pebble beds
International Nuclear Information System (INIS)
The prediction of the temperature distribution in a packed bed requires the knowledge of the effective thermal conductivity in the core and the wall heat transfer coefficient. Empirical correlations published previously yield strongly differing results varying by a factor of ten at low Reynolds numbers. Very high Reynolds numbers had not yet been investigated. Wall heat transfer coefficients in pebble beds were achieved by applying the analogy between heat and mass transfer on sublimation of napthalene into air. The use of mass transfer instead of heat transfer techniques provides some advantages concerning secondary effects. Two series of tests applying napthalene mass transfer were performed in the ranges of Reynolds number 5x101 ? Re ? 6x103 and 2x103 ? Re ? 2x104. Moreover, the mass transfer in the inlet section was investigated. The results of both test series match well. A good agreement is observed with earlier published data, which were not affected by entrance effects. The data are correlated for the range of Reynolds numbers 5x101 ? Re ? 2x104. The transition effect observed at Re ? 4x103 is explained by a change of the flow structure. A correlation is given for the mass and heat transfer in the entrance section. (orig.)
Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models
Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...
Estimation of bulk transfer coefficient for latent heat flux (Ce)
Digital Repository Service at National Institute of Oceanography (India)
Sadhuram, Y.
1991-01-01
The bulk transfer coefficient for latent heat flux (Ce) has been estimated over the Arabian Sea from the moisture budget during the pre-monsoon season of 1988. The computations have been made over two regions (A: 0-8 degrees N: 60-68 degrees E: B: 0...
The mass energy transfer and mass absorption coefficients
International Nuclear Information System (INIS)
The calculation of the mass energy transfer and the mass absorption coefficients is presented and data for their change by energy, in range from 0,01 MeV to 10 MeV, are given. Data are numerically and graphically presented for following materials: air, water, polyethylene, lucite and polystyrene (author)
Inverse estimation of the local heat transfer coefficient in curved tubes: a numerical validation
International Nuclear Information System (INIS)
Wall curvature represents one of the most used passive techniques to enhance convective heat transfer. The effectiveness of wall curvature is due to the fact that it gives origin to the centrifugal force: this phenomenon induces local maxima in the velocity distribution that locally increase the temperature gradients at the wall by then maximizing the heat transfer. This fact brings to a significant variation of the wall temperature and of the wall heat flux along the circumferential coordinate. The convective heat transfer coefficient is consequently not uniformly distributed along the tube's perimeter and is characterized by higher values at the extrados wall surface in comparison to the ones at the intrados wall surface. Therefore, for predicting the overall performance of heat transfer apparatuses that involve the use of curved tubes, it becomes important to know the local distribution of the convective heat transfer coefficient not only along the axis of the heat transfer section, but also on the internal tube's surface along the cross section circumference. The present paper is intended to the assessment of a procedure developed to evaluate the local convective heat transfer coefficient, along the circumferential coordinate, at the internal wall of a coiled pipe.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Energy Technology Data Exchange (ETDEWEB)
Bell, J H; Hand, L A
2005-04-21
The growth rate of a crystal in a supersaturated solution is limited by both reaction kinetics and the local concentration of solute. If the local mass transfer coefficient is too low, concentration of solute at the crystal-solution interface will drop below saturation, leading to a defect in the growing crystal. Here, mass transfer coefficients are calculated for a rotating crystal growing in a supersaturated solution of potassium diphosphate (KDP) in water. Since mass transfer is difficult to measure directly, the heat transfer coefficient of a scale model crystal in water is measured using temperature-sensitive paint (TSP). To the authors' knowledge this is the first use of TSP to measure temperatures in water. The corresponding mass transfer coefficient is then calculated using the Chilton- Colburn analogy. Measurements were made for three crystal sizes at two running conditions each. Running conditions include periodic reversals of rotation direction. Heat transfer coefficients were found to vary significantly both across the crystal faces and over the course of a rotation cycle, but not from one face to another. Mean heat transfer coefficients increased with both crystal size and rotation rate. Computed mass transfer coefficients were broadly in line with expectations from the full-scale crystal growth experiments. Additional experiments show that continuous rotation of the crystal results in about a 30% lower heat transfer compared to rotation with periodic reversals. The continuous rotation case also shows a periodic variation in heat transfer coefficient of about 15%, with a period about 1/20th of the rotation rate.
The prediction of heat transfer coefficient in circulating fluidized bed combustors
Energy Technology Data Exchange (ETDEWEB)
Hamdan, M.A.; Al-Qaq, A.M. [Jordan Univ., Amman (Jordan). Dept. of Mechanical Engineering
2007-07-01
The growing interest in circulating fluidized bed boilers can be attributed to its efficient combustion of low-grade fuels. However, in order to design circulating fluidized beds, it is important to know the underlying mechanisms involved in the heat transfer between gas-solid suspensions and immersed cooling surfaces. The heat transfer coefficient in circulating fluidized bed combustors involves particle and gas convective heat transfer and radiative heat transfer, whose contribution becomes significant at elevated bed temperatures. This paper reviewed several studies that have been conducted to evaluate heat transfer coefficient in circulating fluidized bed combustors. It then presented results of a theoretical study that was performed to modify an existing model that was used to predict the heat transfer coefficient. Certain parameters in the existing model were given constant values, which resulted in an error in the obtained value of the heat transfer coefficient. As a first step, that model was thoroughly studied and values for certain parameters were changed. The modified model was tested against previous experimental and theoretical data available in literature. It was concluded that the accuracy of the model improved significantly when the parameters of terminal velocity (Ut), cluster voidage (ec), cluster time (c) and wall emissivity (ew) were not treated as fixed values. 7 refs., 5 figs.
Curvature dependence of the interfacial heat and mass transfer coefficients
Glavatskiy, K. S.; Bedeaux, D.
2013-01-01
Nucleation is often accompanied by heat transfer between the surroundings and a nucleus of a new phase. The interface between two phases gives an additional resistance to this transfer. For small nuclei the interfacial curvature is high, which affects not only equilibrium quantities such as surface tension, but also the transport properties. In particular, high curvature affects the interfacial resistance to heat and mass transfer. We develop a framework for determining the ...
Heat transfer coefficient for lead matrixing in disposal containers for used reactor fuel
International Nuclear Information System (INIS)
In the Canadian Nuclear Fuel Waste Management Program, metal matrices with low melting points are being evaluated for their potential to provide support for the shell of disposal containers for used fuel, and to act as an additional barrier to the release of radionuclides. The metal matrix would be incorporated into the container by casting. To study the heat transfer processes during solidification, a steady-state technique was used, involving lead as the cast metal, to determine the overall heat transfer coefficient between the lead and some of the candidate container materials. The existence of an air gap between the cast lead and the container material appeared to control the overall heat transfer coefficient. The experimental observations indicated that the surface topography of the container material influences the heat transfer and that a smoother surface results in a greater heat transfer than a rough surface. The experimental results also showed an increasing heat transfer coefficient with increasing temperature difference across the container base plates; a model developed to base-plate bending can explain the observed results
Heat/Mass Transfer Coefficients of an Absorber in Absorption Refrigeration System
Fujita, Isamu; Hihara, Eiji
This paper presents a new method to calculate heat and mass transfer coefficients applicable to the vertical tube or plate type absorber of absorption refrigeration system. Conventional method for calculating the coefficients using logarithmic mean temperature/ concentration differences is criticized for its lacking in the theoretical rationality and usually giving untrue values except some limited situations such that temperature of the solution can be assumed to change linearly along the heat transfer surface. The newly introduced method, which is intended to overcome this difficulty, is verified by numerical simulation and is accompanied by an example applied to the experimental results.
Transfer coefficients of radionuclides from feed to livestock products
International Nuclear Information System (INIS)
The accumulation of data on radionuclide transfer are poor in Japan and those are limited to 90Sr, 137Cs and 131I released from the previous atomic bomb experiments. However, in Europe, intensive studies on environment RI level which affects the restriction of the intake for meats and milk products have been made as the measures against the environment radioactivity due to Chernobyl accident. The transfer coefficients of radionuclides to meats and milk products were estimated on a basis of the data published in the Science of the Total Environment vol.85(1989), Oxford University and CEC Radiation Protection, EUR 12608 EN, Luxembourg, 1990 in addition to the data on Exclusion of Radioactivity from foods, Environment Parameter, series No. 4. On the other hand, the transfer coefficients for Japanese were estimated using the concerned data from published reports and the environment radioactivity data reported by national and local government bodies. In this book, many new data of transfer coefficient are presented in tables along with the previous data collected by international nuclear energy agencies and respective national facilities concerned. (M.N.)
Determining Overall Heat Transfer Coefficient and Shading Coefficient of Doubleskin Facade
Mulyadi, Rosady
2011-01-01
The overall heat transfer coefficient (U?value) and the shading coefficient (SC?value) are substantial properties of double?skin façade. They are importantly required for energy?use estimation, particularly for heat load calculation of the air?conditioning system. The determination of the U?value and the SC?value of double?skin façade was done by numerical simulation employing FORTRAN for the one?year duration. By utilizing the least square method, the equation of U?value and S...
Directory of Open Access Journals (Sweden)
Heung-Kyu Kim
2015-04-01
Full Text Available Using an inverse analysis technique, the heat transfer coefficient on the die-workpiece contact surface of a hot stamping process was evaluated as a power law function of contact pressure. This evaluation was to determine whether the heat transfer coefficient on the contact surface could be used for finite element analysis of the entire hot stamping process. By comparing results of the finite element analysis and experimental measurements of the phase transformation, an evaluation was performed to determine whether the obtained heat transfer coefficient function could provide reasonable finite element prediction for workpiece properties affected by the hot stamping process.
Water mist effect on heat transfer coefficient in cooling of casting die
Directory of Open Access Journals (Sweden)
R. W?adysiak
2008-10-01
Full Text Available This project is showing investigation results of heat transfer process between cast iron die and environment during cooling of die in the temperature range 600÷100 C with compressed air, spray water and water mist streamed under pressure 0.35 0.45 MPa in air jet0.3 0.4 MPa .At the paper are shown results of cooling die’s flat wall using open cooling system. The temperature gradient was presented at die’s wallthickness and calculated thermal curve for cooling surface. The calculation results of heat transfer coefficient ? were presented between die and researched cooling factors and also mathematical models of ? coefficient depending on surface temperature. Revealed that coefficient ? has the biggest value’s range for die cooling with water mist under pressure 0.3/0.35 MPa.
INFLTB, Dosimetric Mass Energy Transfer and Absorption Coefficient
International Nuclear Information System (INIS)
1 - Description of program or function: INFLTB calculates mass energy transfer and mass energy absorption coefficients between 1 keV and 100 MeV for 29 elements and 14 mixtures and compounds of general dosimetric interest. Elements: hydrogen, helium, lithium, beryllium, carbon, graphite, nitrogen, oxygen, fluorine, neon, aluminum, silicon, sulfur, argon, calcium, titanium, iron, copper, germanium, krypton, molybdenum, tin, iodine, barium, gadolinium, tungsten, platinum, uranium, silver, lead. Mixtures and compounds: A-150 tissue-equivalent plastic, adipose tissue (ICRP), adipose tissue (ICRU, 1986), air, dry (near sea level), bone, compact (ICRU), bone, cortical (ICRP), bone, cortical (ICRU, 1986), calcium fluoride, calcium fluoride, ferrous sulfate (standard Fricke) dosimeter solution, ferrous sulfate ('super' Fricke) dosimeter solution, glass, borosilicate ('Pyrex', corning 7740), lithium fluoride, muscle, skeletal (ICRP), muscle, skeletal (ICRU, 1986), muscle, striated (ICRU), polyethylene, polymethyl methacrylate, 'Lucite', 'Perspex', 'Plexiglas', polystyrene, polytetrafluoroethylene, 'Teflon', water, liquid, water vapor, Te gas(methane). 2 - Method of solution: The mass energy transfer coefficient is calculated from the sum of the interaction cross sections (atomic photo effect, Compton scattering, and pair plus triplet production) multiplied by their respective average fractions of energy transferred to electrons and positrons. The mass energy absorption coefficitrons. The mass energy absorption coefficient is the product of the mass energy transfer coefficient and 1 - G, where G is the average fraction of the secondary electron (or positron) kinetic energy that is spent in Bremsstrahlung production and in-flight positron annihilation. 3 - Restrictions on the complexity of the problem: Photon source energies are limited to values between 1 keV and 100 MeV. Radiation yield files are available only for 29 element and 14 compounds and mixtures
Saponification reaction system: a detailed mass transfer coefficient determination.
Pe?ar, Darja; Goršek, Andreja
2015-01-01
The saponification of an aromatic ester with an aqueous sodium hydroxide was studied within a heterogeneous reaction medium in order to determine the overall kinetics of the selected system. The extended thermo-kinetic model was developed compared to the previously used simple one. The reaction rate within a heterogeneous liquid-liquid system incorporates a chemical kinetics term as well as mass transfer between both phases. Chemical rate constant was obtained from experiments within a homogeneous medium, whilst the mass-transfer coefficient was determined separately. The measured thermal profiles were then the bases for determining the overall reaction-rate. This study presents the development of an extended kinetic model for considering mass transfer regarding the saponification of ethyl benzoate with sodium hydroxide within a heterogeneous reaction medium. The time-dependences are presented for the mass transfer coefficient and the interfacial areas at different heterogeneous stages and temperatures. The results indicated an important role of reliable kinetic model, as significant difference in k(L)a product was obtained with extended and simple approach. PMID:25830982
Energy Technology Data Exchange (ETDEWEB)
Burch, D.M.; Licitra, B.A.; Zarr, R.R. (National Inst. of Standards and Tech., Gaithersburg, MD (United States))
1990-02-01
This paper experimentally verifies and compares two dynamic test methods for a calibrated hot box to characterize the transient thermal performance of complex walls. In these methods, a wall specimen is sandwiched between the two conditioning chambers of a calibrated hot box. The exterior surface of the wall specimen is subjected to a time-varying excitation function in air temperature. At the interior surface, the air temperature is maintained steady, and the heat transfer response is measured. Conduction transfer function coefficients that relate the measured heat transfer response to the excitation function are derived. The two dynamic test methods were applied to an insulated hollow concrete block wall that contained significant thermal bridges and lateral heat flows. Empirical transfer function coefficients derived by the test methods predicted with good agreement the heat transfer response of this wall specimen when its exterior surface was subjected to excitation functions that differed markedly from those used to derive the coefficients.
Energy Technology Data Exchange (ETDEWEB)
Castell, Albert; Sole, Cristian; Medrano, Marc; Roca, Joan; Cabeza, Luisa F. [Departament d' Informatica i Enginyeria Industrial, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain); Garcia, Daniel [Departament Projectes d' Enginyeria, Universitat Politecnica de Catalunya, Colom 11, 08222 Terrassa (Spain)
2008-09-15
To determine the heat transfer coefficient by natural convection for specific geometries, experimental correlations are used. No correlations were found in the literature for the geometries studied in this work. These geometries consisted of a cylindrical module of 88 mm of diameter and 315 mm height with external vertical fins of 310 mm height and 20 and 40 mm length. To determine the heat transfer coefficient by natural convection, experimental work was done. This module, containing PCM (sodium acetate trihydrate), was situated in the middle upper part of a cylindrical water tank of 440 mm of diameter and 450 mm height. The calculated heat transfer coefficient changed by using external fins, as the heat transfer surface was increased. The temperature variation of the PCM and the water are presented as a function of time, and the heat transfer coefficient for different fins is presented as a function of the temperature difference. Experimental correlations were obtained, presenting the Nusselt number as a function of different dimensionless numbers. Different correlations were analysed to find which one fit better to the experimental data. (author)
Resonant charge transfer at dielectric surfaces
Marbach, Johannes; Fehske, Holger
2012-01-01
We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable nitrogen molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance and subsequent electron emission by decay of this ion, either due to its natural life time or its interaction with the surface. The electron capture is modeled using the Keldysh Green's function technique and the negative ion decay is described by a combination of the Keldysh technique and a rate equation approach. We find the resonant capture of electrons to be very efficient and the natural decay to be clearly dominating over the surface-induced decay. Secondary electron emission coefficients are calculated for aluminum oxide, magnesium oxide, silicon oxide, and diamond at several kinetic energies of the projectile. With the exception of magnesium oxide the coefficients turn out to be of the order of...
Interfacial mass transfer and mass transfer coefficient in aqua ammonia packed bed absorber
Energy Technology Data Exchange (ETDEWEB)
Selim, A.M. [College of Technology, Jeddah (Saudi Arabia); Elsayed, M.M. [Kuwait Univ., Mechanical Engineering Dept., Safat (Kuwait)
1999-06-01
A mathematical model was given to predict the mass transfer between flow of a mixture of ammonia vapor and water vapor and a flow of aqua ammonia solution at any interface within a packed bed absorber (PBA). The model used the molal mass and heat transfer coefficients in both the liquid and gas phases, the interface molal solution concentration, interface molal vapor mixture concentration, interface temperature, and the heat transfer coefficients in the liquid and gas phases in both sides of the interface. The heat transfer coefficient was corrected to account for the mass transfer. The model was also used to derive a convenient mass transfer coefficient which was based on the bulk mass concentration, not on the molal concentration,and not directly dependent on the concentration at the interface. To complete the model, mathematical correlations were derived for several thermodynamic and physical properties of aqua ammonia solution and vapor mixture. A computer program was developed to demonstrate the use of the model to predict the rate of absorption of ammonia vapor at an interface within the packed bed at various operating conditions. (Author)
Local heat transfer coefficient in a fluidized bed
International Nuclear Information System (INIS)
This paper presents an experimental study for the local heat transfer coefficient. The experiments was conducted inside a reactor with inner diameter (I D = 142mm) at atmospheric conditions (temperature mean value = 29 deg.) The bed was heated by means of a parochial electric heater with a diameter of (dh = 29 mm) and a constant power of 5W. The following factors varied: particles type and diameter, fluid velocity, bed height and heater position inside the reactor. The results were presented and discussed. (author). 15 refs., 7 figs
Thermal properties and heat transfer coefficients in cryogenic cooling
Biddulph, M. W.; Burford, R. P.
This paper considers two aspects of the design of the cooling stage of the process known as cryogenic recycling. This process uses liquid nitrogen to embrittle certain materials before grinding and subsequent separation. It is being increasingly used in materials recycling. A simple method of establishing thermal diffusivity values of materials of interest by using cooling curves is described. These values are important for effective cooler design. In addition values of convective heat transfer coefficient have been determined in an operating inclined, rotating cylindrical cooler operating on scrap car tyres. These will also be useful for cooler design methods.
DEFF Research Database (Denmark)
Ratkovich, Nicolas Rios; Berube, P.R.
2011-01-01
One of the operational challenges associated with membrane bioreactors (MBRs) is the fouling of the membranes. In tubular side-stream MBRs, fouling reduction can be achieved through controlling the hydrodynamics of the two-phase slug flow near the membrane surface. The two-phase slug flow induces higher shear stresses near the membrane surface, which generate high mass transfer coefficients from the surface to the bulk region. However, measuring the mass transfer coefficient is difficult in complex heterogeneous mixtures like activated sludge and existing techniques (e.g. electrochemical methods) cannot be applied directly. As an alternative, in this work, a multidisciplinary approach was selected, by exploiting dimensionless analysis using the Sherwood number. Mass transfer coefficients were measured at various superficial velocities of gas and liquid flow in a tubular system. Due to the variability of the mass transfer coefficient obtained for each experimental condition, the results were compiled into, mass transfer coefficient histograms (MTH) for analysis. A bimodal MTH was observed, with one peak corresponding to the mass transfer induced by the liquid flow, and the other peak induced by the gas flow. It was noted that coalescence of bubbles affects the MTH. Coalescence increased the “width” of the peaks (i.e. the estimate of the variability of the mass transfer coefficient) and the height of the peak (i.e. amount of time that a mass transfer coefficient of a given value is maintained). A semi-empirical relationship based on the Lévêque relationship for the Sherwood number (mass transfer coefficient) was formulated for the laminar regime. A test case comparison between water and activated sludge was performed based on full-scale airlift MBR operational conditions. It was found that the Sherwood number in the non-Newtonian case is 8% higher than that in the Newtonian case.
Efficiency analysis of straight fin with variable heat transfer coefficient and thermal conductivity
Energy Technology Data Exchange (ETDEWEB)
Sadri, Somayyeh; Raveshi, Mohammad Reza; Amiri, Shayan [K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)
2012-04-15
In this study, one type of applicable analytical method, differential transformation method (DTM), is used to evaluate the efficiency and behavior of a straight fin with variable thermal conductivity and heat transfer coefficient. Fins are widely used to enhance heat transfer between primary surface and the environment in many industrial applications. The performance of such a surface is significantly affected by variable thermal conductivity and heat transfer coefficient, particularly for large temperature differences. General heat transfer equation related to the fin is derived and dimensionalized. The concept of differential transformation is briefly introduced, and then this method is employed to derive solutions of nonlinear equations. Results are evaluated for several cases such as: laminar film boiling or condensation, forced convection, laminar natural convection, turbulent natural convection, nucleate boiling, and radiation. The obtained results from DTM are compared with the numerical solution to verify the accuracy of the proposed method. The effects of design parameters on temperature and efficiency are evaluated by some figures. The major aim of the present study, which is exclusive for this article, is to find the effect of the modes of heat transfer on fin efficiency. It has been shown that for radiation heat transfer, thermal efficiency reaches its maximum value.
Li, Huiping; He, Lianfang; Zhang, Chunzhi; Cui, Hongzhi
2015-06-01
The thermal physical parameters have significant effects on the calculation accuracy of physical fields, and the boundary heat transfer coefficient between the die and water is one of the most important thermal physical parameters in the hot stamping. In order to attain the boundary heat transfer coefficient, the testing devices and test procedures are designed according to the characteristic of heat transfer in the hot stamping die. A method of estimating the temperature-dependent boundary heat transfer coefficient is presented, and an inverse heat conduction software is developed based on finite element method, advance-retreat method and golden section method. The software is used to calculate the boundary heat transfer coefficient according to the temperatures measured by NiCr-NiSi thermocouples in the experiment. The research results show that, the convergence of the method given in the paper is well, the surface temperature of sample has a significant effect on the boundary heat transfer coefficient between the die and water. The boundary heat transfer coefficient increases as the surface temperature of sample reduces, and the variation is nonlinear.
Carneiro, O.S.; Nóbrega, J. M.; Mota, Armando R.; Silva, Carolina, 1983-
2013-01-01
The extrusion of technical thermoplastics profiles generally uses a dry calibration/cooling system, composed by one or several calibrators in series. One of the major difficulties to be faced when modelling this important stage is an adequate prescription of the heat transfer coefficient, hinterface, between the plastic profile surface and the cooling medium, which must include the effect of the interface contact resistance. This is the motivation that led the present research ...
Determining convective heat transfer coefficient using phoenics software package
Energy Technology Data Exchange (ETDEWEB)
Kostikov, A.; Matsevity, Y. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine, Kharkov (Ukraine)
1997-12-31
The two methods of determination of such important quantity of heat exchange on a body surface using PHOENICS are suggested in the presentation. The first method consists in a post-processing of results of conjugate heat transfer problem solved by PHOENICS. The second one is solving an inverse heat conduction problem for solid body using PHOENICS. Comparative characteristic of these two methods is represented. (author) 4 refs.
Stojanovic, B.; J. Janevski; M. Stojiljkovic
2009-01-01
The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their us...
Estimation of Extract Yield and Mass Transfer Coefficient in Solvent Extraction of Lubricating Oil
Hussain K. Hussain
2010-01-01
An investigation was conducted to suggest relations for estimating yield and properties of the improved light lubricating oil fraction produced from furfural extraction process by using specified regression.Mass transfer in mixer-settler has been studied. Mass transfer coefficient of continuous phase, mass transfer coefficient of dispersed phase and the overall mass transfer coefficient extraction of light lubes oil distillate fraction by furfural are calculated in addition to all physical pr...
Confirmation of selected milk and meat radionuclide-transfer coefficients
International Nuclear Information System (INIS)
The elements selected for study of their transfer coefficients to eggs, poultry meat, milk and beef were Mo, Tc, Te, and Ba. The radionuclides used in the study were the gamma-emitting radionuclides 99Mo, /sup 123m/Te and 133Ba. 133Ba was selected because 140Ba-140La is produced infrequently and availability was uncertain. 133Ba has a great advantage for our type of experiment because of its longer physical half-life. 99Tc is a pure beta-emitter and was used in the first three animal experiments because we could not obtain the gamma-emitting /sup 95m/Tc. A supply of this nuclide was recently obtained, however, for the second cow experiment
Meromorphic differentials with twisted coefficients on compact Riemann surfaces
Yang, Yi-Hu
2007-01-01
This note is to concern a generalization to the case of twisted coefficients of the classical theory of Abelian differentials on a compact Riemann surface. We apply the Dirichlet's principle to a modified energy functional to show the existence of differentials with twisted coefficients of the second and third kinds under a suitable assumption on residues.
International Nuclear Information System (INIS)
The effect of the heat transfer coefficient at the casting-mold interface is of prime importance to improve the casting quality, especially for castings in metal molds. However, it is difficult to determine the values of heat transfer coefficient from experiments due to the influence of various factors, such as contacting pressure, oxides on surfaces, roughness of surfaces, coating material, coating thickness and gap formation caused by the deformation of casting and mold, etc. In the present paper, the interfacial heat transfer coefficient (IHTC) between the casting and metal mold is identified by using the method of inverse analysis based on measured temperatures, neural network with back-propagation algorithm and numerical simulation. Then, by applying the identified IHTC in finite element analysis, the comparison between numerical calculated and experimental results is made to verify the correctness of method. The results show that the numerical calculated temperatures are in good agreement with experimental ones. These demonstrate that the method of inverse analysis is a feasible and effective tool for determination of the casting-mold IHTC. In addition, it is found that the identified IHTC varies with time during the casting solidification and varies in the range of about 100-3200 Wm-2K-1. The characteristics of the time-varying IHTC have also been discussed.
Modeling the Effect of Internal Convection Currents on Heat Transfer Coefficient of Liquid Foods
Directory of Open Access Journals (Sweden)
SAJID ALI
2013-04-01
Full Text Available The internal convection currents generated during the cooling process affect convective heat transfer coefficient from the surface of the container, these convection currents may increase the effective value of the surface film conductance (h. Therefore, in such situation the Nu-Re correlations, which are generally used to predict h-values, may not yield realistic results. In the present work, this effect has been investigated by using the empirical correlation developed through Temperature-Time measurements at the centre of liquid food containers during cooling .The main concern of the present work is about considering the heat transfer behaviour for liquid foods for which a cylindrical shape container of brass metal have taken, in this work the transient Time-Temperature relation is utilized to calculate the value of convection heat transfer coefficient (h for each measured temperature at the centre of the cylinder (r¬¬o=0. Then after plotting the graph between ‘h’ and ‘T’ an expression between h and T is obtained, which is fed back in the programme developed with the help of finite difference method by which Time-Temperature variation is obtained. Experimental procedure was used to determine surface film conductance of cylindrical Apple and Orange juice container, calculated temperatures have been compared with the experimental results when the measured surface film conductance were used to solve the transient heat conduction equation in cylindrical coordinates. A consistently excellent agreement was observed.
FEROZ, Shaik
2006-01-01
This paper presents experimental results for the mass transfer coefficients in the impingement region of a multi-jet flow. A disc distributor containing `N' nozzles produces multi-jets that interact in a complex manner before they reach the target surface where mass transfer occurs. In particular, the size of the distributor disc, together with its height from the target surface, and the nozzle hole diameters and arrangements are varied in the experiments to find their effects o...
Determining heat transfer coefficients in radial flow through a polyethylene packed
Directory of Open Access Journals (Sweden)
Luís Patiño
2010-07-01
Full Text Available A numerical-experimental methodology was used for determining interstitial heat transfer coefficients in water flowing through po-rous media where it was not in heat balance with the solid phase. Heat transfer coefficients were obtained through the single blow transient test method, combining experimental test equipment results with a mathematical model’s numerical solution. The partial differential equation system produced by the mathematical model was resolved by a numerical finite volume method-ba-sed methodology. Experimental tests and numerical solutions were satisfactorily carried out for different values from the fluid’s surface speed from the entrance to the bed and for different porosity values, finding that Nusselt numbers increased when Reynolds numbers also increased and that Nusselt numbers increased when porosity decreased. A 650 Reynolds number and 0.375 porosity gave a Nusselt number of up to 2.8.
DMS gas transfer coefficients from algal blooms in the Southern Ocean
Directory of Open Access Journals (Sweden)
T. G. Bell
2014-11-01
Full Text Available Air/sea dimethylsulfide (DMS fluxes and bulk air/sea gradients were measured over the Southern Ocean in February/March 2012 during the Surface Ocean Aerosol Production (SOAP study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (>15 nM. Gas transfer coefficients were considerably scattered at wind speeds above 5 m s?1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A~flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data shows no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.
Boiling Heat Transfer on Superhydrophilic, Superhydrophobic, and Superbiphilic Surfaces
Betz, Amy Rachel; Kim, Chang-Jin 'CJ'; Attinger, Daniel
2012-01-01
With recent advances in micro- and nanofabrication, superhydrophilic and superhydrophobic surfaces have been developed. The statics and dynamics of fluids on these surfaces have been well characterized. However, few investigations have been made into the potential of these surfaces to control and enhance other transport phenomena. In this article, we characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic, and provide nucleation measurements. The most interesting result of our measurements is that the largest heat transfer coefficients are reached not on surfaces with spatially uniform wettability, but on biphilic surfaces, which juxtapose hydrophilic and hydrophobic regions. We develop an analytical model that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coefficient. Finally, we manufacture and test the first superbiphilic surfaces (juxtaposing superhydrophobic ...
International Nuclear Information System (INIS)
A study to measure the transfer of radiocaesium to adult female sheep through a breeding cycle is described. The transfer of radiocaesium from the diet to muscle (estimated as the equilibrium transfer coefficient) was significantly lower to pregnant, and especially lactating, animals compared to non-lactating and barren animals. High dry matter intake rates were also associated with significantly lower transfer coefficients. Known relationships between dry matter intake rates and protein turnover could credibly explain some of these differences. However, when described as the concentration ratio, radiocaesium transfer to meat was apparently highest during lactation. The apparent difference in results obtained by the two approaches of determining transfer is the consequence of daily dry matter intake being a denominator within the estimation of transfer coefficient. A wider discussion of transfer coefficients and concentration ratios leads us to suggest that the concentration ratio is the more robust and potentially generic parameter
Gladden, H. J.; Proctor, M. P.
1985-01-01
A transient technique was used to measure heat transfer coefficients on stator airfoils in a high-temperature annular cascade at real engine conditions. The transient response of thin film thermocouples on the airfoil surface to step changes in the gas stream temperature was used to determine these coefficients. In addition, gardon gages and paired thermocouples were also utilized to measure heat flux on the airfoil pressure surface at steady state conditions. The tests were conducted at exit gas stream Reynolds numbers of one-half to 1.9 million based on true chord. The results from the transient technique show good comparison with the steady-state results in both trend and magnitude. In addition, comparison is made with the STAN5 boundary layer code and shows good comparison with the trends. However, the magnitude of the experimental data is consistently higher than the analysis.
Experimentally Determined Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments
Bue, Grant; Watts, Carly; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vonau, Walt; Vogel, Matt; Conger, Bruce
2015-01-01
A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flowrate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.
International Nuclear Information System (INIS)
Processes of heat transfer with periodically varying intensity on the surface of heated bodies of three typical geometries (plate, cylinder, sphere) are considered. The true heat transfer coefficient, which varies in time by the law of a periodic step function having two free parameters - amplitude and asymmetry, is specified on the heat transfer surface. Resultant relations are obtained for calculating the experimental heat transfer coefficient, which is the quantity measured in a traditional heat transfer experiment and used in applied calculations
Estimation of grass to cow's milk transfer coefficients for emergency situations
International Nuclear Information System (INIS)
Several studies have been reported on soil to grass equilibrium transfer factors and grass to cow's milk transfer coefficients for 137Cs for the environs of different nuclear power plants of both India and other parts of the world. In such studies, the activity concentration of 137Cs is measured in grass collected from different places. Cow's milk samples are collected from nearby localities or from milk dairies and analyzed for 137Cs and the grass to cow's milk transfer coefficient is estimated. In situation where 137Cs is not present in measurable activity concentrations, its stable counterpart (Cs) is measured for the estimation of transfer coefficients. These transfer coefficient values are generally used in theoretical models to estimate the dose to the population for hypothetical situation of emergency. It should be noted that the transfer coefficients obtained for equilibrium conditions may not be totally applicable for emergency situation. However, studies aimed at evaluating transfer coefficients for emergency situations are sparse because nuclear power plants do not release 137Cs during normal operating situations and therefore simulating situation of emergency release is not possible. Hence, the only method to estimate the grass to milk transfer coefficient for emergency situation is to spike the grass with small quantity of stable Cs. This paper reports the results of grass to milk transfer coefficients for stable isotope of Cesium (Cs) for emergency situation
Estimating the workpiece-backingplate heat transfer coefficient in friction stirwelding
DEFF Research Database (Denmark)
Larsen, Anders; Stolpe, Mathias
2012-01-01
Purpose - The purpose of this paper is to determine the magnitude and spatial distribution of the heat transfer coefficient between the workpiece and the backingplate in a friction stir welding process using inverse modelling. Design/methodology/approach - The magnitude and distribution of the heat transfer coefficient are the variables in an optimisation problem. The objective is to minimise the difference between experimentally measured temperatures and temperatures obtained using a 3D finite element model. The optimisation problem is solved using a gradient based optimisation method. This approach yields optimal values for the magnitude and distribution of the heat transfer coefficient. Findings - It is found that the heat transfer coefficient between the workpiece and the backingplate is non-uniform and takes its maximum value in a region below the welding tool. Four different parameterisations of the spatial distribution of the heat transfer coefficient are analysed and a simple, two parameter distribution is found to give good results. Originality/value - The heat transfer from workpiece to backingplate is important for the temperature field in the workpiece, and in turn the mechanical properties of the welded plate. Accurate modelling of the magnitude and distribution of the heat transfer coefficient is therefore an essential step towards improved models of the process. This is the first study using a gradient based optimisation method and a non-uniform parameterisation of the heat transfer coefficient in an inverse modeling approach to determine the heat transfer coefficient in friction stir welding. © Emerald Group Publishing Limited.
Turbulent transfer coefficient and roughness length in a high-altitude lake, Tibetan Plateau
Li, Zhaoguo; Lyu, Shihua; Zhao, Lin; Wen, Lijuan; Ao, Yinhuan; Wang, Shaoying
2015-04-01
A persistent unstable atmospheric boundary layer was observed over Lake Ngoring, caused by higher temperature on the water surface compared with the overlying air. Against this background, the eddy covariance flux data collected from Lake Ngoring were used to analyse the variation of transfer coefficients and roughness lengths for momentum, heat and moisture. Results are discussed and compared with parameterization schemes in a lake model. The drag coefficient and momentum roughness length rapidly decreased with increasing wind velocity, reached a minimum value in the moderate wind velocity and then increased slowly as wind velocity increased further. Under weak wind conditions, the surface tension or small scale capillary wave becomes more important and increases the surface roughness. The scalar roughness length ratio was much larger than unity under weak wind conditions, and it decreased to values near unity as wind velocity exceeded 4.0 m s-1. The lake model could not reproduce well the variation of drag coefficient, or momentum roughness length, versus wind velocity in Lake Ngoring, but it did simulate well the sensible heat and latent heat fluxes, as a result of complementary opposite errors.
The surface collective diffusion coefficient and diffuse phase transformations.
Czech Academy of Sciences Publication Activity Database
Chvoj, Zden?k
SISSA, - (2008), P08002/1-P08002/12. ISSN 1742-5468 Institutional research plan: CEZ:AV0Z10100521 Keywords : surface effects (theory) * surface diffusion (theory) * transport processes/heat transfer (theory) Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.758, year: 2008
Calculating the heat transfer coefficient of frame profiles with internal cavities
DEFF Research Database (Denmark)
Noyé, Peter Anders; Laustsen, Jacob Birck
2004-01-01
Determining the energy performance of windows requires detailed knowledge of the thermal properties of their different elements. A series of standards and guidelines exist in this area. The thermal properties of the frame can be determined either by detailed two-dimensional numerical methods or by measurements in accordance to European or international standards. Comparing measured and calculated heat transfer coefficients for two typical frame profiles with cavities shows considerable differences. This investigation considers two typical frame profiles in aluminium and PVC with internal cavities. The heat transfer coefficient is determined by two-dimensional numerical calculations and by measurements. Calculations are performed in Therm (LBNL (2001)), which is developed at Lawrence Berkeley National Laboratory, USA. The calculations are performed in accordance with the future European standards and measurements have been performed at two German research institutes. The internal cavities have a large influence on the overall thermal performance of the frame profiles and the investigation shows that the applied method for modelling the heat transfer by radiation exchange in the internal cavities of the profiles is critical. The simple radiation model described in the pre European standard (prEN ISO 10077-2) does not yield valid results compared to measured values. Applying a more detailed, viewfactor based, grey surfaces enclosure model as described in the ISO standard (ISO/DIS 15099) gives a better correspondence between measured and calculated values. Hence, when determining the heat transfer coefficient of frame profiles with internal cavities by calculations, it is necessary to apply a more detailed radiation exchange model than described in the prEN ISO 10077-2 standard. The ISO-standard offers such an alternative.
Energy Technology Data Exchange (ETDEWEB)
Banerjee, S.; Hassan, Y.A. [Texas A& M Univ., College Station, TX (United States)
1995-09-01
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.
International Nuclear Information System (INIS)
Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology's (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values
EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT OVER THE DIMPLED SURFACE
Directory of Open Access Journals (Sweden)
Dr. Sachin L. Borse
2012-08-01
Full Text Available Over the past couple of years the focus on using concavities or dimples provides enhanced heat transfer has been documented by a number of researchers. Dimples are used on the surface of internal flow passages because they produce substantial heat transfer augmentation. This project work is concerned with experimentalinvestigation of the forced convection heat transfer over the dimpled surface. The objective of the experiment is to find out the heat transfer and air flow distribution on dimpled surfaces and all the results obtained are compared with those from a flat surface. The varying parameters were i Dimple arrangement on the plate i.e.staggered and inline arrangement and ii Heat input iiiDimple density on the plate. Heat transfer coefficients and Nusselt number were measured in a channel with one side dimpled surface. Thespherical type dimples were fabricated, and the diameter and the depth of dimple were 6 mm and 3 mm, respectively. Channel height is 25.4mm, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 5000 to 15000.Study shown that thermal performance is increasing with Reynolds number. With the inline and staggered dimple arrangement, the heat transfer coefficients, Nusselt number and the thermal performance factors were higher for the staggered arrangement.
International Nuclear Information System (INIS)
Two-phase flow heat transfer has been exhaustively studied over recent years. However, in this field several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling have been studied using different approaches, numerical, analytical and experimental. In this work, an experimental analysis, data representation and heat transfer coefficient prediction on two-phase heat transfer on nucleate and convective boiling are presented. An empirical correlation is obtained based on genetic algorithms search engine over a dimensional analysis of the two-phase flow heat transfer problem. (author)
The usage of transfer coefficients to describe radionuclide transport from a cow's diet to its milk
International Nuclear Information System (INIS)
The terms 'transfer coefficient', 'transfer function' and 'transfer rate' are used to describe the transport of radionuclides from a cow's diet to her milk. Simple derivation of these parameters, their interpretations and interrelationships are given, and possible misinterpretations of published values due to imprecise definitions or incorrectly supplied or omitted units are reviewed. (author)
Convective Heat Transfer Coefficients of the Human Body under Forced Convection from Ceiling
DEFF Research Database (Denmark)
Kurazumi, Yoshihito; Rezgals, Lauris
2014-01-01
The average convective heat transfer coefficient for a seated human body exposed to downward flow from above was determined. Thermal manikin with complex body shape and size of an average Scandinavian female was used. The surface temperature distribution of the manikin’s body was as the skin temperature distribution of an average person. The measurements were performed in a room with controlled thermal environment. Air temperature was set at 26ºC for cooling and at 20ºC for heating. The radiant temperature asymmetry in horizontal and vertical direction was close to zero, i.e. mean radiant temperature was equal to the air temperature. The air velocity of the isothermal downward flow from the ceiling at height of 1.5 m above the floor (above the top of the head) was set in a range between still air and 0.73 m/s. Based on the analyses of the results relationships for determination of the convective heat transfer coefficient of the whole body (hc [W/(m2•K)]) was proposed: hc=4.088+6.592V1.715 for a seated naked body at 20ºC and hc=2.874+7.427V1.345 for a seated naked body at 26ºC. Differences in the convective heat transfer coefficient of the whole body in low air velocity range, V<0.3 m/s, due to the natural convection were found. The results may be useful during design of air distribution in rooms, e.g. low impulse ventilation, diffuse ventilation, etc.
Scientific Electronic Library Online (English)
B., Stojanovic; J., Janevski; M., Stojiljkovic.
2009-06-01
Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were perfo [...] rmed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.
Directory of Open Access Journals (Sweden)
B. Stojanovic
2009-06-01
Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.
Prediction of gas-liquid mass transfer coefficient in sparged stirred tank bioreactors.
Garcia-Ochoa, Felix; Gomez, Emilio
2005-12-20
Oxygen mass transfer in sparged stirred tank bioreactors has been studied. The rate of oxygen mass transfer into a culture in a bioreactor is affected by operational conditions and geometrical parameters as well as the physicochemical properties of the medium (nutrients, substances excreted by the micro-organism, and surface active agents that are often added to the medium) and the presence of the micro-organism. Thus, oxygen mass transfer coefficient values in fermentation broths often differ substantially from values estimated for simple aqueous solutions. The influence of liquid phase physicochemical properties on kLa must be divided into the influence on k(L) and a, because they are affected in different ways. The presence of micro-organisms (cells, bacteria, or yeasts) can affect the mass transfer rate, and thus kLa values, due to the consumption of oxygen for both cell growth and metabolite production. In this work, theoretical equations for kLa prediction, developed for sparged and stirred tanks, taking into account the possible oxygen mass transfer enhancement due to the consumption by biochemical reactions, are proposed. The estimation of kLa is carried out taking into account a strong increase of viscosity broth, changes in surface tension and different oxygen uptake rates (OURs), and the biological enhancement factor, E, is also estimated. These different operational conditions and changes in several variables are performed using different systems and cultures (xanthan aqueous solutions, xanthan production cultures by Xanthomonas campestris, sophorolipids production by Candida bombicola, etc.). Experimental and theoretical results are presented and compared, with very good results. PMID:16155951
Experimental study of convective coefficient of mass transfer of avocado (Persia americana Mill.)
Energy Technology Data Exchange (ETDEWEB)
Alves, Suerda Bezerra; Luiz, Marcia Ramos; Amorim, Joselma Araujo de; Gusmao, Rennam Pereira de; Gurgel, Jose Mauricio [Universidade Federal da Paraiba (LES/UFPB), Joao Pessoa, PB (Brazil). Lab. de Energia Solar
2010-07-01
Most of all energy consumed worldwide comes from fossil fuels derived from petroleum. With the petroleum crisis in the 70 were sought new energy sources, among them renewable. One such source is biodiesel energy, organic matter originated from animal and/or vegetable. Among the various plant species is the avocado (Persia americana Mill.) showing great potential in the production of petroleum extracted from the pulp and the alcohol removed from the seed. The main obstacle for obtaining the petroleum is the high humidity found in the pulp, being necessary to the drying process, which involves the transfer of heat and mass. The aim of this study was to use the mathematical model represented by Newton's Law of Cooling to simulate the mass transfer on the surface of the avocado pulp during the drying process. The equation of the mathematical model was solved numerically and the method of least squares was identified convective coefficient of Mass Transfer. The dryer used in the experimental process was operated with air flow in the vertical, air flow average fixed 3m/s and temperatures of 50, 60 and 70 deg C. The scheme of the dryer used in the research is composed of the following equipment: centrifugal fan, which drives the air-drying; valve, which allows control of airflow; electrical resistance, used for heating air; the drying chamber, where enables measurement of temperature and relative humidity; support for smaller trays; trays smaller, where the samples of the pulp of the avocado are placed; exit of the air of drying for the environment. The result presented shows the ratio of moisture content as a function of temperature over time, where it is possible to also observe that how much bigger the temperature of drying, greater will be the convective coefficient of mass transfer of the avocado. (author)
Vacca, Santiago; Martorano, Marcelo A.; Heringer, Romulo; Boccalini, Mário
2015-05-01
The heat transfer coefficient at the metal-mold interface ( h MM) has been determined for the first time during the centrifugal casting of a Fe-C alloy tube using the inverse solution method. To apply this method, a centrifugal casting experiment was carried out to measure cooling curves within the tube wall under a mold rotation speed of 900 rpm, imposing a centrifugal force 106 times as large as the gravity force (106 G). As part of the solution method, a comprehensive heat transfer model of the centrifugal casting was also developed and coupled to an optimization algorithm. Finally, the evolution of h MM with time that gives the minimum squared error between measured and calculated cooling curves was obtained. The determined h MM is approximately 870 W m-2 K-1 immediately after melt pouring, decreasing to about 50 W m-2 K-1 when the average temperature of the tube is ~973 K (700 °C), after the end of solidification. Despite the existence of a centrifugal force that could enhance the metal-mold contact, these values are lower than those generally reported for static molds with or without an insulating coating at the mold inner surface. The implemented model shows that the heat loss by radiation is dominant over that by convection at the tube inner surface, causing the formation of a solidification front that meets another front coming from the outer surface of the tube.
EMILA ŽIVKOVI?; STEPHAN KABELAC; SLOBODAN ŠERBANOVI?
2009-01-01
The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution ...
Pool boiling heat transfer enhancement on porous surface tube
International Nuclear Information System (INIS)
The passive residual heat removal exchanger (PRHR HX), which is a key equipment of the passive residual heat removal system, is installed in an elevated pool. Its heat transfer performance affects security and economics of the reactor, and boiling heat transfer in the liquid surrounding the exchanger occurs when the liquid saturation temperature exceeded. The smooth tubes, which are widely used as heat transfer tubes in PRHR HX, can be replaced by some enhanced tubes to improve the boiling heat transfer capability. In this paper, the pool boiling heat transfer characteristics of smooth tube and a machined porous surface tube are investigated by using high-pressure steam condensing inside tube as heating source. Compared with smooth tube,the porous surface tube considerably enhances the boiling heat transfer, and shortens the time significantly before reaching the liquid saturation temperature. Its boiling heat transfer coefficient increases from 68% to 75%, and the wall superheat decreases by 1.5 degree C. Combining effect of condensation inside tube with boiling outside tube, the axial wall temperatures of heat transfer tube are neither uniform nor linear distribution. Based on these investigations, enhance mechanism of the porous surface tube is analyzed. (authors)
Determination and correlation of mass transfer coefficients in a stirred cell
International Nuclear Information System (INIS)
In the proposed Molten Salt Breeder Reactor flowsheet, a fraction of the rare earth fission products is removed from the fuel salt in mass transfer cells. To obtain design parameters for this extraction, the effect of cell size, blade diameter, phase volume, and agitation rate on the mass transfer for a high density ratio system (mercury/water) in nondispersing square cross section contactors was determined. Aqueous side mass transfer coefficients were measured by polarography over a wide range of operating conditions. Correlations for the experimental mass transfer coefficients as functions of the operating parameters are presented. Several techniques for measuring mercury-side mass transfer coefficients were evaluated and a new one is recommended
International Nuclear Information System (INIS)
Transfer coefficients have become virtually indispensible in the study of the fate of radioisotopes released from nuclear installations. These coefficients are used in equilibrium assessment models where they specify the degree of transfer in food chains of individual radioisotopes from soil to plant products and from feed or forage and drinking water to animal products and ultimately to man. Information on transfer coefficients for terrestrial food chain models is very piecemeal and occurs in a wide variety of journals and reports. To enable us to choose or determine suitable values for assessments, we have addressed the following aspects of transfer coefficients on a very broad scale: (1) definitions, (2) equilibrium assumption, which stipulates that transfer coefficients be restricted to equilibrium or steady rate conditions, (3) assumption of linearity, that is the idea that radioisotope concentrations in food products increase linearly with contamination levels in the soil or animal feed, (4) methods of determination, (5) variability, (6) generic versus site-specific values, (7) statistical aspects, (8) use, (9) sources of currently used values, (10) criteria for revising values, (11) establishment and maintenance of files on transfer coefficients, and (12) future developments. (auth)
Measurement of heat transfer coefficient using termoanemometry methods.
Czech Academy of Sciences Publication Activity Database
Dan?ová, Petra; Sitek, P.; Vít, T.
Liberec : Technical University of Liberec, 2013 - (Vít, T.; Dan?ová, P.; Novotný, P.), s. 152-155 ISBN 978-80-260-5375-0. [Experimental Fluid Mechanics 2013. Kutná hora (CZ), 19.11.2013-22.11.2013] Institutional support: RVO:61388998 Keywords : syntetic jet * thermoanemometry * heat transfer Subject RIV: BJ - Thermodynamics
Measurement of the Convective Heat-Transfer Coefficient
Conti, Rosaria; Gallitto, Aurelio Agliolo; Fiordilino, Emilio
2014-01-01
We propose an experiment for investigating how objects cool down toward the thermal equilibrium with their surroundings. We describe the time dependence of the temperature difference of the cooling objects and the environment with an exponential decay function. By measuring the thermal constant t, we determine the convective heat-transfer…
DEFF Research Database (Denmark)
Henningsen, Poul; Hattel, Jesper Henri
1998-01-01
Temperature is measured during backward can extrusion of steel. The process is characterised by large deformations and very high surface pressure. In the experiments, a can in low carbon steel with a lubrication layer of phosphate soap is formed. The temperature is measured by thermocouples in the die insert. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface.All of the temperature measurements in the tool and the workpiece are compared with a number of FEM simulations computed with different heat transfer coefficients. The current heat transfer coefficient is determined from the simulations.
137Cs transfer coefficients from fodder to cow milk
International Nuclear Information System (INIS)
The transfer of 137Cs from the components of cows' diets to milk was followed in detail on 10 farms in the north-eastern region of Italy (Friuli-Venezia Giulia) from June to July 1988. Samples of milk, grass and other components of the cows' diet were collected regularly and analysed for radiocaesium content. The transfer factors, calculated for 137Cs after a four-week feeding period with contaminated silage, were higher (0.0064) than those calculated in 1987 in the same area (0.0030). This may be attributable to the fact that the 137Cs associated to the forage administrated to cows in 1988 was completely incorporated in the plant and thus more assimilable to the cattle. (Author)
Determining the surface roughness coefficient by 3D Scanner
Directory of Open Access Journals (Sweden)
Karmen Fifer Bizjak
2010-12-01
Full Text Available Currently, several test methods can be used in the laboratory to determine the roughness of rock joint surfaces.However, true roughness can be distorted and underestimated by the differences in the sampling interval of themeasurement methods. Thus, these measurement methods produce a dead zone and distorted roughness profiles.In this paper a new rock joint surface roughness measurement method is presented, with the use of a camera-typethree-dimensional (3D scanner as an alternative to current methods. For this study, the surfaces of ten samples oftuff were digitized by means of a 3D scanner, and the results were compared with the corresponding Rock JointCoefficient (JRC values. Up until now such 3D scanner have been mostly used in the automotive industry, whereastheir use for comparison with obtained JRC coefficient values in rock mechanics is presented here for the first time.The proposed new method is a faster, more precise and more accurate than other existing test methods, and is apromising technique for use in this area of study in the future.
A new interpretation of internal heat transfer coefficients of porous media
Dybbs, A.; Kar, K.; Groeneweg, M.; Ling, J. X.; Naraghi, M.
1984-01-01
The results of laser anemometer and flow visualization based fluid mechanics studies of porous media are used to obtain heat transfer coefficients for porous materials. Average pore flow Re ranging from 0.16-700 were examined. Darcy, inertial steady laminar, unsteady laminar and turbulent flow regimes were detected. A passage length model was devised to derive the heat transfer coefficient. Sample data from flows through porous metals composed of powders and fibers validated the passage length for Darcy and inertial flow regimes. Unsteady laminar and turbulent flow coefficients require the identification of new parameters.
Modeling of the substrate and product transfer coefficients for ethanol fermentation
International Nuclear Information System (INIS)
The transfer phenomena of the substrate and product for ethanol fermentation with immobilized biocatalyst were investigated. Fermentation was carried out with a biocatalyst consisting of Ca-alginate gel in the form of two-layer spherical beads in anaerobic conditions. The determination of kinetic parameters was achieved by fitting bioreaction progress curves to the experimental data. The calculation of the diffusion coefficients was performed by numerical methods for experimental conditions. Finally, the glucose and ethanol transfer coefficients are defined and determined, using the effective diffusion coefficients. (Abstract Copyright [2008], Wiley Periodicals, Inc.)
Measuring convective heat transfer coefficient around a heated fine wire in cross flow of nanofluids
International Nuclear Information System (INIS)
Recent researches on nanofluids have mainly focused on the increase of thermal conductivity of nanofluids under static condition. The ultimate goal of using nanofluids, however, is to enhance the heat transfer performance under fluid flow. So it has been highly necessary to devise a simple and accurate measuring apparatus which effectively compares the heat transfer capability between the base and nanofluids. Though the convective heat transfer coefficient is not the complete index for the heat transfer capability, it might be one of useful indications of heat transfer enhancement. In this article, the working principles of experimental system for convective heat transfer coefficient around a heated fine wire in cross flow of nanofluids and its application example to three samples of nano lubrication oils are explained in detail
Study on heat transfer coefficients during cooling of PET bottles for food beverages
Liga, Antonio; Montesanto, Salvatore; Mannella, Gianluca A.; La Carrubba, Vincenzo; Brucato, Valerio; Cammalleri, Marco
2015-08-01
The heat transfer properties of different cooling systems dealing with Poly-Ethylene-Terephthalate (PET) bottles were investigated. The heat transfer coefficient (Ug) was measured in various fluid dynamic conditions. Cooling media were either air or water. It was shown that heat transfer coefficients are strongly affected by fluid dynamics conditions, and range from 10 W/m2 K to nearly 400 W/m2 K. PET bottle thickness effect on Ug was shown to become relevant under faster fluid dynamics regimes.
Prediction of overall heat transfer coefficient for RMI insulation using the test and analysis
International Nuclear Information System (INIS)
Both parts of shell and layers have different thermal transfer flow; shell-part is conductivity loss, layer is convective and radiative loss that would contribute to calculate the total heat value with difficulty. We developed the new method about prediction of RMI's total value by separating the shell and layer as a function of heat resistivity. Whereas heat transfer value at the insulation shell is calculated by CFD analysis according to various insulation sizes, multi-layer would be done by thermal test. These predicted models are compared with final insulation sample of overall heat transfer value for the validation. RMI insulation was investigated by GHP (guarded hot plate) measuring instrument (inner-layer) and thermal analysis simulation(CFD method) to predict the approximate value of overall heat transfer. The results are as follows. - Thickness of out-shell as same meaning of outshell ratio is determined very carefully at RMI design. Because it can lead to very large changes in heat transfer. For example, whereas thickness of out-shell with 0.1mm(0.13%) shows 0.16 W/m2K through surface of out-shell, that of 0.4mm(0.53%) thickness is 0.49 W/m2K which is increased nonlinearly. - Inner-layer and out-shell of RMI is arranged in parallel, so that overall heat transfer coefficient would be written with sum of each part. For example, at the condition of 70 .deg. C, inner-layer part(0.06mm) is 0.56 W/m2K and out-shell part(0.7mm) is 0.72 W/m2K, and overall value is 1.28 W/m2K. - We could expect that heat transfer value is changed according to out-shell ratio, because out-shell ratio as conductivity loss is connected with insulation size and inner-layer as radiation blocking is independent
Heat Transfer Variation on Protuberances and Surface Roughness Elements
Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.
1995-01-01
In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.
Pandey, P.; De Ridder, K.; Gillotay, D.
2011-12-01
In the present study, we consider the effect of remotely sensed COT on surface UV irradiance and photolysis rate coefficients. These coefficients and the effect of cloud there on, play a crucial role in atmospheric chemistry, in particular the formation of ozone. The COT for this study is retrieved from the Spinning Enhanced Visible infrared Imager (SEVIRI) by implementing semi-analytical cloud retrieval algorithm for the month of June 2006. A simple parameterization of the effect of cloud on surface UV-A and UV-B irradiance, based on a series of simulations performed with the Tropospheric Ultraviolet and Visible (TUV) radiative transfer model, is developed. The required columnar ozone concentration is set to 335 DU that is obtained from multi sensor Re-analysis data set for June 2006 near the centre of our study domain (Belgium) and the surface albedo is set to 5% for the radiative transfer calculations. For the purpose of validation, measurements of UV-A and UV-B irradiance from two Belgian stations, Ostend and Redu, are used. The time series of the modeled UV-A and UV-B irradiance against the measurements shows a good agreement. This is apparent from the model versus measurement error statistics. The mean absolute error, correlation coefficient and index of agreement for UV-A irradiance for both stations are found to be ~5.6 W/m2, ~0.92 and ~0.93 respectively; whereas, for the UV-B irradiance they are ~0.58 W/m2, ~0.93 and ~0.86, respectively. The effect of COT on photolysis rate coefficients of different photolytic reactions is also presented along with simple parameterizations to account for the effect of cloud. The maximum error associated with the parameterization is found to be of the order of few percent or less, with the highest error of 9%.
Estimation of grass to milk transfer coefficient for Strontium for emergency situations
International Nuclear Information System (INIS)
The grass to milk transfer coefficient is usually represented as Fm values. This paper reports the results of grass to cow milk transfer coefficients (Fm) for Strontium for emergency situation. An experimental grass field was developed in Kaiga region and 2 cows were adopted for collecting milk samples regularly. Grass was cut from the field and spiked with very low concentration of stable Strontium, taken in the form of Sr(No3)2, to simulate a sudden deposition of Strontium on grass and fed to the adopted cows. The milk samples were collected during normal milking periods (morning and evening) for several days and analyzed. The peak concentration of Sr in milk was observed during time period 12-36 hrs after the intake of spiked grass. The mean value of transfer coefficient was found to be 1.4 x 10-3 d L-1. The grass to milk transfer coefficient values observed under spiked conditions were similar to that observed for equilibrium transfer coefficient for Kaiga region. (author)
Heat Transfer Coefficient Analysis for Coolant Channels in a VHTR
International Nuclear Information System (INIS)
A very high temperature reactor (VHTR) is graphite moderated and helium cooled reactor and selected as a next generation nuclear reactor for its ultimate safety among various advantages. This type reactor has become of great interest in terms of using a process heat. To utilize VHTR safely and practically, optimized heat flux analysis is necessary. Empirical correlations for a Nusselt number have widely been applied to predict the convective heat transfer in coolant channels of a prismatic VHTR. This approach has advantages of fast computation. However, there has been no in-depth study on their applicability to the thermo-fluid conditions of coolant channels of a prismatic VHTR. Therefore, this paper investigates the applicability of well-known empirical correlations to the coolant channels of a prismatic VHTR by using the detailed numerical results obtained from the 3-D computational fluid dynamics (CFD) analysis. In particular, the effect of two different wall heating condition on the applicability of empirical correlations is focused in this paper
Charge transfer kinetics from surface plasmon resonance voltammetry.
Lu, Jin; Li, Jinghong
2014-04-15
On the basis of a quantitative relationship between surface plasmon resonance signal and electrochemical current in the electrochemical surface plasmon resonance (EC-SPR), EC-SPR signal measures the semi-integral of faradaic current. We theoretically discussed the electrode potential and charge transfer kinetics to be determined from surface plasmon resonance voltammetry (or potential sweep EC-SPR) signals for the fully reversible, quasi-reversible, and irreversible redox reactions. The results indicated that the electroanalysis of EC-SPR signal is more straightforward than conventional electrochemical current. Then, we studied two model redox reactions of hexaammineruthenium chloride and 4-nitrotoluene, to obtain half wave potential of quasi-reversible redox reaction, transfer coefficient, and standard rate constant of irreversible redox reaction from EC-SPR signals. PMID:24654883
Local Mass Transfer Coefficient for Idealized 2D Urban Street Canyon Models
Leung, Ka Kit; Liu, Chun-Ho
2011-09-01
Human activities in urban areas is one of the major sources of anthropogenic releases in the atmospheric boundary layer (ABL). The mechanism of urban morphology for the heat and mass transfer in built environment is thus an attractive topic in the research community. In this paper, a series of laboratory measurements is conducted to elucidate the mass transfer from hypothetical urban roughness constructed by idealized 2D street canyons. The experiments are carried out in the wind tunnel in the University of Hong Kong. The urban ABL structure inside the wind tunnel is controlled by placing small cubic Styrofoam blocks upstream of the test section. The street canyons are fabricated by movable rectangular acrylic blocks so that different building height to street width (aspect) ratios are examined. The height of building blocks is kept minimum to make sure that the urban ABL over the street canyons is high enough for fully developed turbulent flows. The prevailing wind is normal to the street axis, demonstrating the scenario of least pollutant removal from the street canyons to the urban ABL. The sample street canyon is covered by soaked filter papers to represent uniform mass concentrations on the building facades and ground surface. The wet bulb temperature of the filter papers is continuously monitored to ensure saturated conditions. Their weight before and after an experiment is used to measure the amount of water evaporated. Preliminary results illustrate the local mass transfer coefficient distribution for aspect ratios 1/4, 1/2, 1, and 2, which are comparable with those available in literuatre.
International Nuclear Information System (INIS)
Hydrogen is expected to serve as a clean secondary energy, because it can be manufactured from water, used in a variety of energy end-use sectors as fuel, and returned to water after burning. For the realization of hydrogen energy system, development of efficient and economical hydrogen production methods is required to meet the future huge demand of hydrogen. The Iodine-Sulfur (IS) process is a promising candidate of such hydrogen production methods, in which water reacts with iodine and sulfur dioxide to produce hydrogen iodide and sulfuric acid (Bunsen reaction) and the produced acids are then decomposed to produce hydrogen and oxygen, respectively. This study is concerned with the development of IS process equipment named direct contact sulfuric acid concentrator, in which gaseous mixture produced by thermal decomposition of sulfuric acid contacts directly with sulfuric acid solution. In the concentrator, the high temperature heat of the decomposed gas is recovered and used to concentrate sulfuric acid solution and, at the same time, the undecomposed sulfuric acid is condensed and separated from the decomposition products of sulfur dioxide and oxygen. Although the concept is very attractive from the viewpoint of the development of compact and efficient sulfuric acid concentrator, little is known on the heat and mass transfer relevant to the concentrator. Therefore, experimental methods were discussed to acquire the gas-phase mass transfer coefficient required for the optimal design of the concentrator. Assuming the use of wetted-wall column and also of the sulfuric acid of azeotropic composition as the test solution which could eliminate the liquid-phase mass transfer resistance, the column specification and the measurement conditions were determined by which flooding could be avoided and surface wetting could be assured, as well. (author)
Transfer coefficient study of Sr-90 in the soil-grass-milk chain for Cuba
International Nuclear Information System (INIS)
One of the most important problems in modern radioecology is the lack of able information about the features of radionuclide migration in tropical and subtropical environment. The development of nuclear energy and the enhancing in the applications of nuclear techniques in those latitudes indicate that studies in this area are necessary. Cuba is carrying out studies on radioecological characterization of the principal food chains in the country. One of the objectives of these studies is to define the values of the transfer coefficients to be used in the evaluation programs for the assessment of the radiological impact of practices which involve ionizing radiation. This paper shows the results obtained in the determination of Sr-90 transfer coefficients in soil-grass-milk food chain in 'La Quebrada', a place near the Havana City where an important part of the milk that the citizens consume is produced. Transfer coefficients for Sr-90 were calculated on the basis of data collected during 5 years in the region. Soil-grass transfer coefficients are in the range 0.18-5 while grass-milk coefficients are in the range of 1.2x10-4 - 6x10-3 day/L. These values are in accordance with values reported by other authors in the literature. (authors). 4 refs., 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Lee, Shinpyo [Kyonggi Univ., Suwon (Korea, Republic of)
2012-01-15
This paper describes a measuring apparatus that can be used to appraise the effectiveness of nanofluids as new heat transfer enhancing fluids. A couple of apparatuses using fine hot wires as sensors have been proposed for this purpose; however, they have a technical weakness related to the uncertain working conditions of the sensor. The present method used the convective heat transfer coefficient from a hot wire as an indication of the heat transfer effectiveness of the nanofluid, where the temperature of the wire remains constant during the experiment. The operating principle and experimental procedure are explained in detail, and the validity of the system is tested with pure base fluids. The effects of particle concentration, velocity, and temperature on the heat transfer coefficients of the nanofluids are discussed comprehensively using the experimental data for graphite nanolubrication oil.
Energy Technology Data Exchange (ETDEWEB)
Donne, M.D.; Piazza, G. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik; Goraieb, A.; Sordon, G.
1998-01-01
The four ITER partners propose to use binary beryllium pebble bed as neutron multiplier. Recently this solution has been adopted for the ITER blanket as well. In order to study the heat transfer in the blanket the effective thermal conductivity and the wall heat transfer coefficient of the bed have to be known. Therefore at Forschungszentrum Karlsruhe heat transfer experiments have been performed with a binary bed of beryllium pebbles and the results have been correlated expressing thermal conductivity and wall heat transfer coefficients as a function of temperature in the bed and of the difference between the thermal expansion of the bed and of that of the confinement walls. The comparison of the obtained correlations with the data available from the literature show a quite good agreement. (author)
Time dependence of the 137Cs and 90Sr transfer coefficient in a Mediterranean ecosystem
International Nuclear Information System (INIS)
The soil-plant transfer of 137Cs and 90Sr was studied in a low turnover rate Mediterranean ecosystem. The available activities of the two radionuclides in the soil and their stable chemical analogues, K and Ca, respectively, evolve periodically over time due to the marked dry and wet seasons existing in this type of climate. This seriously restricts the validity of using constant transfer and discrimination coefficients
Raseelo J. Moitsheki
2008-01-01
Lie point symmetry analysis is performed for an unsteady nonlinear heat diffusion problem modeling thermal energy storage in a medium with a temperature-dependent power law thermal conductivity and subjected to a convective heat transfer to the surrounding environment at the boundary through a variable heat transfer coefficient. Large symmetry groups are admitted even for special choices of the constants appearing in the governing equation. We construct one-dimensional optimal systems for the...
International Nuclear Information System (INIS)
Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. In this study, the heat transfer performance of the automobile radiator is evaluated experimentally by calculating the overall heat transfer coefficient (U) according to the conventional ?-NTU technique. Copper oxide (CuO) and Iron oxide (Fe2O3) nanoparticles are added to the water at three concentrations 0.15, 0.4, and 0.65 vol.% with considering the best pH for longer stability. In these experiments, the liquid side Reynolds number is varied in the range of 50–1000 and the inlet liquid to the radiator has a constant temperature which is changed at 50, 65 and 80 °C. The ambient air for cooling of the hot liquid is used at constant temperature and the air Reynolds number is varied between 500 and 700. However, the effects of these variables on the overall heat transfer coefficient are deeply investigated. Results demonstrate that both nanofluids show greater overall heat transfer coefficient in comparison with water up to 9%. Furthermore, increasing the nanoparticle concentration, air velocity, and nanofluid velocity enhances the overall heat transfer coefficient. In contrast, increasing the nanofluid inlet temperature, lower overall heat transfer coefficient was recorded. -- Highlights: ? Overall heat transfer coefficient in the car radiator measured experimentally. ? Nanofluids showed greater heat transfer performance comparing with water. ? Increasing liquid and air Re increases the overall heat transfer coefficient. ? Increasing the inlet liquid temperature decreases the overall heat transfer coefficient
Czech Academy of Sciences Publication Activity Database
Heyrovská, Rajalakshmi
Brno : P?írodov?decká fakulta MU, 2002. s. 24. [Pracovní setkání fyzikálních chemik? a elektrochemik? /3./. 06.02.2002, Brno] Institutional research plan: CEZ:AV0Z4040901 Keywords : transfer coefficient * hydration Subject RIV: CG - Electrochemistry
Evaluation of convective heat transfer coefficient of various crops in cyclone type dryer
International Nuclear Information System (INIS)
In this paper, an attempt was made to evaluate the convective heat transfer coefficient during drying of various crops and to investigate the influences of drying air velocity and temperature on the convective heat transfer coefficient. Drying was conducted in a convective cyclone type dryer at drying air temperatures of 60, 70 and 80 deg. C and velocities of 1 and 1.5 m/s using rectangle shaped potato and apple slices (12.5 x 12.5 x 25 mm) and cylindrical shaped pumpkin slices (35 x 5 mm). The temperature changes of the dried crops and the temperature of the drying air were measured during the drying process. It was found that the values of convective heat transfer coefficient varied from crop to crop with a range 30.21406 and 20.65470 W/m2 C for the crops studied, and it was observed that the convective heat transfer coefficient increased in large amounts with the increase of the drying air velocity but increased in small amounts with the rise of the drying air temperature
Evaluation of convective heat transfer coefficient of various crops in cyclone type dryer
Energy Technology Data Exchange (ETDEWEB)
Akpinar, E. Kavak [Mechanical Engineering Department, Firat University, 23279 Elazig (Turkey)]. E-mail: eakpinar@firat.edu.tr
2005-09-15
In this paper, an attempt was made to evaluate the convective heat transfer coefficient during drying of various crops and to investigate the influences of drying air velocity and temperature on the convective heat transfer coefficient. Drying was conducted in a convective cyclone type dryer at drying air temperatures of 60, 70 and 80 deg. C and velocities of 1 and 1.5 m/s using rectangle shaped potato and apple slices (12.5 x 12.5 x 25 mm) and cylindrical shaped pumpkin slices (35 x 5 mm). The temperature changes of the dried crops and the temperature of the drying air were measured during the drying process. It was found that the values of convective heat transfer coefficient varied from crop to crop with a range 30.21406 and 20.65470 W/m{sup 2} C for the crops studied, and it was observed that the convective heat transfer coefficient increased in large amounts with the increase of the drying air velocity but increased in small amounts with the rise of the drying air temperature.
Busuttil, M; Lin, YP; Gebelin, JC; Reed, RC
2013-01-01
The influence of glass coating thickness on the interfacial heat transfer coefficient has been examined using numerical modeling. Temperature and heat flux during working of a Inconel 718 work-piece and colder H13 dies have been simulated. The thickness of the glass coating is found to have a significant influence on the forming characteristic. © (2013) Trans Tech Publications, Switzerland.
An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s pen...
Czech Academy of Sciences Publication Activity Database
Kárászová, Magda; Šim?ík, Miroslav; Friess, K.; Lísal, Martin; Jansen, J. C.; Sedláková, Zuzana; R?ži?ka, Marek; Izák, Pavel
Prague : -, 2013, s. 1. ISBN N. [Annual Meeting NAMS 2013 /23/. Boise, Idaho (US), 08.06.2013-12.06.2013] R&D Projects: GA ?R GAP106/10/1194 Institutional support: RVO:67985858 Keywords : mass transfer coefficients * ionic liquid membranes * permeability and selectivity Subject RIV: CI - Industrial Chemistry, Chemical Engineering
The prediction of heat transfer coefficient in circulating fluidized bed combustors
Energy Technology Data Exchange (ETDEWEB)
Hamdan, M.A.; Al-qaq, A.M. [Department of Mechanical Engineering, University of Jordan Amman, Qween Rania Street, Amman, AL Jbeeha 11942 (Jordan)
2008-11-15
In the present work, a theoretical study is performed to modify an existing model that is used to predict the heat transfer coefficient in circulating fluidized bed combustors. In the model, certain parameters were used as being of constant values, which leads to an error in the obtained value of the heat transfer coefficient. In this study and as a first step, the model is thoroughly studied and then the variation of the coefficient with these parameters is presented. Having done that, correlation for these parameters are obtained and then used in the model. Finally the modified model was tested against previously experimental and theoretical data that is available in literature. It was found that the accuracy of the model has been improved after it has been modified. (author)
The prediction of heat transfer coefficient in circulating fluidized bed combustors
International Nuclear Information System (INIS)
In the present work, a theoretical study is performed to modify an existing model that is used to predict the heat transfer coefficient in circulating fluidized bed combustors. In the model, certain parameters were used as being of constant values, which leads to an error in the obtained value of the heat transfer coefficient. In this study and as a first step, the model is thoroughly studied and then the variation of the coefficient with these parameters is presented. Having done that, correlation for these parameters are obtained and then used in the model. Finally the modified model was tested against previously experimental and theoretical data that is available in literature. It was found that the accuracy of the model has been improved after it has been modified
Evaluation of the heat transfer coefficient at the metal-mould interface during flow
Directory of Open Access Journals (Sweden)
Z. Konopka
2007-12-01
Full Text Available Calculation results concerning the heat transfer coefficient at the metal-mould interface during flow of the AlMg10 alloy in the channel-like cavity of the spiral castability test mould. The experimental cooling curve as well as changes of metal flow velocity have been determined on the basis of the measured metal temperature during flow. The cooling curve equation for the examined alloy, derived from the heat balance condition in a casting-mould system and taking into account experimental data concerning changes in metal temperature and its flow velocity, has enabled evaluation of the heat transfer coefficient at a chosen point of a metal stream along the mould channel. Graphic representations of changes of this coefficient against time and the channel length have been shown.
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from: inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. The work presented under this task uses the first-principles based Computational Fluid Dynamics (CFD) technique to compute heat transfer from tank wall to the cryogenic fluids, and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between tank wall and cryogenic propellant, and that between tank wall and ullage gas were then simulated. The results showed that commonly used heat transfer correlations for either vertical or horizontal plate over predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
International Nuclear Information System (INIS)
An experimental test to study natural convection heat transfer to air within a trapezoidal channel area was carried out, heating one of its faces. The temperature in different points along the heated face, inlet and outlet air temperature, environment temperature, the current and voltage supplied to the heater were measured. From the measures, the power applied and the average heat transfer coefficient in the channel were determined. During the experimental test the power applied, channel inclination and the air entrance and exit position, were changed. The values obtained from the different test modes show that the heat transfer coefficient is independent of the power and strongly dependent of the channel inclination and channel position. (author)
International Nuclear Information System (INIS)
The present work is to improve our understanding and analysis of direct contact condensation on the gravity injection of CMTs and to measure the heat transfer coefficients around steam bubbles using the holographic interferometry and the high speed camera. The condensation regime map associated with the downward injection of steam into water through the steam pipe is investigated to understand the mechanism of the direct contact condensation. The present map shows that the boundary of chugging and subsonic jetting with the larger diameter pipe is shifted to the larger steam mass flux. Steam cavity mode, ever not found in the literature and the unique mode of downward injection for the present geometry, is observed at the low subcooled water temperature. With the holographic interferometry and the high speed camera, the heat transfer mechanism for the direct contact condensation in CMTs is understood and the heat transfer coefficients are measured
International Nuclear Information System (INIS)
In this work, the response of a double volume transmission ionisation chamber, developed at the Instituto de Pesquisas Energéticas e Nucleares, was compared to that of a commercial transmission chamber. Both ionisation chambers were tested in different X-ray beam qualities using secondary standard ionisation chambers as reference dosimeters. These standard ionisation chambers were a parallel-plate and a cylindrical ionisation chambers, used for diagnostic radiology and mammography beam qualities, respectively. The response of both transmission chambers was compared to that of the secondary standard chambers to obtain coefficients of equivalence. These coefficients allow the transmission chambers to be used as reference equipment. - Highlights: ? Calibration coefficients of standard ionisation chambers were transferred to transmission chambers. ? Coefficients of equivalence were obtained. ? Transmission chambers presented good response stability. ? Transmission chambers can be used as reference equipment considering their response variation.
International Nuclear Information System (INIS)
This paper is concerned with the development of an experimental setup and Finite Element (FE) modeling of dry sliding of metals to estimate interface heat transfer coefficient. Heat transfer between the chip, the tool, and the environment during the metal machining process has an impact on temperatures, wear mechanisms and hence on tool-life and on the accuracy of the machined component. For modeling of the metal machining process, the interface heat transfer coefficient is an important input parameter to quantify the transfer of heat between the chip and the tool and to accurately predict the temperature distribution within the cutting tool. In previous studies involving FE analysis of metal machining process, the heat transfer coefficient has been assumed to be between 10-500 kW/m/sup 2/ deg. C (0.49-24.5 BTU/sec/ft/sup 2//degree F), with a background from metal forming processes (especially forging). Based on the operating characteristics, metal forming and machining processes are different in nature. Hence there was a need to develop a procedure close to metal machining process, to estimate this parameter in order to increase the reliability of FE models. To this end, an experimental setup was developed, in which an uncoated cemented carbide pin was rubbed against a steel work piece while the later was rotated at speeds similar to the cutting tests. This modified pin-on-disc set-up was equipped with temperature and force monitoring equipment. A FE model was constructed for heat generation and frictional contact. The experimental and modeling results of the dry sliding process yield the interface heat transfer coefficient for a range of rubbing speeds. (author)
International Nuclear Information System (INIS)
A recent VAMP (Validation of Environmental Model Predictions) report collated values for aggregated transfer coefficients (Tag) which can describe the integrated transfer of radiocaesium to food products from semi-natural ecosystems. Further Tag data are presented for sheep and mushrooms which suggest that subdivision of Tag values to take soil type and seasonal variation into account is potentially valuable. For sheep, Tag values for organic soils are generally one to two orders of magnitude higher than those for sandy and clay soils. For most other semi-natural foodstuffs there are currently inadequate data to make such subdivisions. (author). 19 refs, 1 fig., 4 tabs
Lüpkes, Christof; Gryanik, Vladimir M.
2015-01-01
The interaction between sea ice and atmosphere depends strongly on the near-surface transfer coefficients for momentum and heat. A parametrization of these coefficients is developed on the basis of an existing parametrization of drag coefficients for neutral stratification that accounts for form drag caused by the edges of ice floes and melt ponds. This scheme is extended to better account for the dependence of surface wind on limiting cases of high and low ice concentration and to include near-surface stability effects over open water and ice on form drag. The stability correction is formulated on the basis of stability functions from Monin-Obukhov similarity theory and also using the Louis concept with stability functions depending on the bulk Richardson numbers. Furthermore, a parametrization is proposed that includes the effect of edge-related turbulence also on heat transfer coefficients. The parametrizations are available in different levels of complexity. The lowest level only needs sea ice concentration and surface temperature as input, while the more complex level needs additional sea ice characteristics. An important property of our parametrization is that form drag caused by ice edges depends on the stability over both ice and water which is in contrast to the skin drag over ice. Results of the parametrization show that stability has a large impact on form drag and, thereby, determines the value of sea ice concentration for which the transfer coefficients reach their maxima. Depending on the stratification, these maxima can occur anywhere between ice concentrations of 20 and 80%.
Directory of Open Access Journals (Sweden)
Nikoli? Z.S.
2007-01-01
Full Text Available In this paper a numerical model will be adopted to analyze the heat transfer process during rapid solidification of a spherical sample placed on a metallic substrate cooled by water. The interfacial heat transfer coefficient between the sample and the substrate will be evaluated by matching model calculations with the surface temperature history recorded by a digital camera during solidification of a sample melted in an Arc-image furnace. .
Condensation heat transfer on superhydrophobic surfaces
Miljkovic, Nenad; Wang, Evelyn N.
2013-01-01
Condensation is a phase change phenomenon often encountered in nature, as well as used in industry for applications including power generation, thermal management, desalination, and environmental control. For the past eight decades, researchers have focused on creating surfaces allowing condensed droplets to be easily removed by gravity for enhanced heat transfer performance. Recent advancements in nanofabrication have enabled increased control of surface structuring for the development of su...
Study for transfer coefficient of iodine from grass to cow milk
International Nuclear Information System (INIS)
Radioiodine (131I) is one of the radio nuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. During the short initial phase of accidental release of radioactivity, 131I is transferred through grass-cow milk pathway, leading to significant thyroid dose to those consuming milk, especially infant and children. Transfer coefficients are important for quick evaluation of environmental contamination, during both normal and abnormal operational phases of a nuclear facility. Transfer coefficient of iodine from grass to milk is defined as ratio of iodine concentration in milk (Bq.L-1) obtained at equilibrium for a constant rate of intake of iodine in (Bq.D-1). During normal operation conditions of nuclear power reactor, the release of radioactive iodine isotopes is are too low that they are not present in measurable concentrations in the environment. Hence, studies are to be performed using stable iodine to estimate the transfer coefficient. A method has been developed based on thermal neutron activation analysis (NAA) to estimate the stable iodine concentration present in grass and cow milk. The method involves pre-concentration from matrix, neutron activation and gamma spectrometry and these were standardized
Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element
International Nuclear Information System (INIS)
Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication...). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance
Directory of Open Access Journals (Sweden)
EMILA ŽIVKOVI?
2009-04-01
Full Text Available The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux, heat flux, pressure of system and the flow configuration on the heat transfer coefficient were also taken into account and a comparison with literature data was performed.
International Nuclear Information System (INIS)
Graphical abstract: - Highlights: • Application of enhanced surfaces in boiling heat transfer. • Flow and pool boiling heat transfer on the heating surfaces with mini-recesses. • Minichannel (horizontal) with the enhanced heating wall. • Determination of heat transfer coefficients and boiling curves. • Comparative experimental data analysis for flow and pool boiling heat transfer. - Abstract: The paper focuses on the analysis of the enhanced surfaces in such applications as boiling heat transfer. The surfaces have similar geometric parameters for the surface development. Two testing measurement modules with enhanced heating surfaces are used independently, one for flow boiling and the other – for pool boiling research. The heating surfaces with mini-recesses which contact boiling liquid are made by spark erosion. Flow boiling is studied when FC-72 flows through a horizontally positioned minichannel and its bottom wall is heated. These experiments were carried out during under a pressure slightly higher than the atmospheric one. Pool boiling experiments were conducted with FC-72 at atmospheric pressure in the vessel using enhanced sample as the bottom heating surface. Comparison of results for flow and pool boiling indicates that obtained heat transfer coefficients are a few times higher for pool boiling in the boiling incipience conditions. There are basic differences in the local heat transfer coefficients during the development of flow boiling in a minichannel, depending on the location along the flow in the channel. In the subcooled boiling area, heat transfer coefficients are low. In developed boiling, they are high, but they decrease when the amount of vapour in the liquid–vapour mixture rises
Study of the average heat transfer coefficient at different distances between wind tunnel models
Gnyrya, A.; Korobkov, S.; Mokshin, D.; Koshin, A.
2015-01-01
The paper presents investigations of physical and climatic factors with regard to design and process variables having effect on heat transfer in the building model system at different distances between them in the airflow direction. The aim of this work is to improve energy efficiency of exterior walls of buildings. A method of physical simulation was used in experiments. Experimental results on the average values of the heat transfer coefficient in the building model system are presented herein. A series of experiments was carried out on a specific aerodynamic test bench including a subsonic wind tunnel, heat models and devices for giving thermal boundary conditions, transducers, and the record system equipment. The paper contains diagrams of the average heat transfer distribution at fixed Reynolds number and the airflow angle of attack; the average values of the heat transfer coefficient for each face and wind tunnel models as a whole at maximum, medium, and large distances between them. Intensification of the average heat transfer was observed on the downstream model faces depending on the distance between models.
A look-up table for film-boiling heat-transfer coefficients in tubes with vertical upward flow
International Nuclear Information System (INIS)
A look-up table of film-boiling heat-transfer coefficients has been developed for steam-water flow inside vertical tubes, using a methodology similar to that for the look-up table of critical heat flux. The film-boiling look-up table provides heat-transfer coefficients at discrete values of pressure, mass flux, heat flux and thermodynamic quality, covering both the inverted annular-flow film-boiling (IAFB) and the dispersed-flow film-boiling (DFFB) regions. The table values are established using 14 687 film-boiling heat-transfer data points for tubes compiled in the AECL film-boiling data bank. At conditions where no data are available, these values are calculated using the Groeneveld-Delorme correlation (for the DFFB region) and the Hammouda model (for the IAFB region). The film-boiling look-up table and other leading film-boiling prediction methods have been assessed using the available data base. The look-up table predicts the surface-temperature data with a root-mean-square error of 6.73% and an average error of 1.2%, which is an improvement over that of other prediction methods. In addition, the film-boiling look-up table covers a wide range of flow conditions, provides a smooth transition between IAFB and DFFB regions, requires little computing time, and exhibits correct asymptotic and parametric trends. (author)
The impact of air flow to the distribution of heat transfer coefficient on circular cylinder.
Czech Academy of Sciences Publication Activity Database
Beran, Pavel
Vol. 1648. Melville, NY : AIP Publishing, 2015 - (Simos, T.; Tsitouras, C.), 090006 ISBN 978-0-7354-1287-3. ISSN 0094-243X. - (AIP Conference Proceedings. 1648). [ International Conference on Numerical Analysis and Applied Mathematics 2014. ICNAAM-2014. Rhodes (GR), 22.09.2014-28.09.2015] R&D Projects: GA ?R(CZ) GBP105/12/G059 Keywords : transient heat transfer * heat transfer coefficient * air flow * finite element method * Reynolds number * climatic tunnel Subject RIV: JN - Civil Engineering http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4912394
Determination of heat transfer coefficient for cooling devices in permanent mould
Energy Technology Data Exchange (ETDEWEB)
Potiron, A.; Gerometta, C.; Plun, J.M. [ENSAM, Angers (France); Caratini, Y. [Pechiney CRV, Voreppe (France); Rigaut, C. [Aluminium Pechiney, Voreppe (France)
1995-12-31
Simulation of casting processes is now industrially available with different softwares proposed to foundrymen. Yet, it is always difficult to provide the boundary conditions as correct as possible to represent accurately the environment of the mould. The knowledge of heat transfer coefficient used to modelize the cooling devices in permanent moulds is very important, as well as the acquisition of accurate data regarding die coatings or physical properties. After having conducted a sample survey with French foundries, the experiment conditions have been defined. Two main types of cooling device have been studied: water running in a pipe and air flowing in a special shape to provide localized cooling. Some of the heat transfer coefficients have been simply calculated using Colburn`s law, others have been determined using a 1D or 2D inverse method. Auto-validation results obtained on the experimental device simulated with SIMULOR, a 3D finite volume software, are encouraging.
Estimations of the coefficient of vertical turbulent transfer in the lower thermosphere
Chunchuzov, E. P.; Shagaev, M. V.
1984-02-01
An important parameter of the turbopause, the coefficient of vertical turbulent exchange transfer, may be evaluated in terms of the turbulent energy generation rate, the horizontal gradient of the mean temperature, and a constant (g/Coriolus parameter for middle latitudes). For a determination of the horizontal gradient, a series of temperature measurements were made in three different regions of the night sky. Simultaneous temperature measurements were made across two OH bands. Standard spectral analysis was used to determine the other properties. Individual values of the gradients were significantly large (on the average 0.052 K/km with a dispersion 0.019 K/km), as was the isotropic distribution. This is in part due to internal-gravity-wave dissipation at the hydroxyl layer altitudes. The calculated coefficients of vertical turbulent transfer agree well with a value obtained by rocket methods.
DEFF Research Database (Denmark)
Henningsen, Poul; Hattel, Jesper Henri
1998-01-01
The large deformations in backward can extrusion result in a rise of temperature of more than 200 oC. In the experiments, cans in low carbon steel are formed with a lubrication layer of phosphate soap. The temperature is measured by thermocouples in the die insert and the punch. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface. The punch is equipped with three thermocouples mounted at a distance of 0.2 mm from the surface. The thermocouples are welded to the end of grooves milled in a small plug, which is pressed into a hold in the punch nose. All the temperature measurements in the tool and the workpiece are compared with a number of finite element (FE) simulations computed with different heat transfer coefficients. The current heat transfer coefficient (HTC) is then determined by the least square method
DEFF Research Database (Denmark)
Henningsen, Poul; Hattel, Jesper Henri
1998-01-01
The large deformations in backward can extrusion result in a rise of temperature of more than 200 degrees Centigrade. In the experiments cans in low carbon steel are formed, with a lubrication layer of phosphate soap. The temperature is measured by thermocouples in the die insert and the punch. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface.The punch is equipped with three thermocouples mounted at a distance of 0.2 mm from the surface. The thermocouples are welded to the end of grooves milled in a small plug, Which is pressed into a hold in the punch nose. All the temperature measurements in the tool and the workpiece are compared with a number of FEM simulations computed with different heat transfer coefficients. The current heat transfer coefficient is determined as the one resulting in the best agreement between measurements and the simulations.
Correlations for the Prediction of NTU and Mass Transfer Coefficient for a VPE.
Czech Academy of Sciences Publication Activity Database
Rathilal, S.; ?árský, M.; Heyberger, Aleš; Rousková, Milena
Praha : Process Engineering Publisher, 2010, s. 411. ISBN 978-80-02-02247-3. [International Congress of Chemical and Process Engineering CHISA 2010 and 7th European Congress of Chemical Engineering ECCE-7 /19./. Prague (CZ), 28.08.2010-01.09.2010] Institutional research plan: CEZ:AV0Z40720504 Keywords : mass transfer coefficient * liquid-liquid extraction * acetone-toluene-water system Subject RIV: CI - Industrial Chemistry, Chemical Engineering www.chisa.cz/2010, www.ecce7.com
Measurement of Mass Transfer Coefficient in Three Airlift Reactors of Different Scale.
Czech Academy of Sciences Publication Activity Database
Blažej, M.; Juraš?ík, M.; Markoš, J.; Drahoš, Ji?í
Bratislava : Slovak University of Technology , 2004 - (Markoš, J.; Štefuca, V.), s. 198 ISBN 80-227-2052-6. [International Conference of Slovak Society of Chemical Engineering /31./. Tatranské Matliare (SK), 24.05.2004-28.05.2004] Grant ostatní: GA SR(SK) VEGA 1/0066/03 Institutional research plan: CEZ:AV0Z4072921 Keywords : mass transfer coefficient * scale-up * internal loop airlift reactor Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Surface initiated atom transfer radical polymerization on gold surface.
Czech Academy of Sciences Publication Activity Database
Rodriguez-Emmenegger, Cesar; Vlasov, P. S.; Sedláková, Zde?ka; Brynda, Eduard; Houska, Milan; Bologna Alles, A.
Saint Petersburg : Institute of Macromolecular Compounds of Russian Academy of Sciences, 2008. 048. [International Symposium on Molecular Order and Mobility in Polymer Systems /6./. 02.06.2008-06.06.2008, Saint Petersburg] R&D Projects: GA AV ?R KAN200670701 Institutional research plan: CEZ:AV0Z40500505 Keywords : surface initiated atom transfer radical polymerization * zwitterionic polymers * antifouling surfaces Subject RIV: CD - Macromolecular Chemistry
Transfer coefficients of selected radionuclides to animal products. II. Hen eggs and meat
International Nuclear Information System (INIS)
Transfer coefficients to eggs and meat were determined after acute oral doses of /sup 95m/Tc, 99Mo, /sup 123m/Te, 133Ba, 131I, 95Zr and 95Nb to laying hens. The mean values (in units of d kg-1) to eggs and hen meat were, respectively, 3.0 and 0.03 for Tc, 0.87 and 0.18 for Mo, 5.1 and 0.60 for Te, 0.87 and 9.2 x 10(-3) for Ba, 3.2 and 0.01 for I, 2 x 10(-4) and 6 x 10(-5) for Zr, and 1 x 10(-3) and 3 x 10(-4) for Nb. For the same radionuclides administered in the same chemical form, transfer coefficients for eggs are about one to two orders of magnitude higher than for cow's milk, while the transfer coefficients for hen meat are several orders of magnitude higher than for beef
Mirmanto, M.
2015-09-01
Experiments to investigate local pressure distribution and local heat transfer coefficients during flow boiling of water in a microchannel were performed. The hydraulic diameter of the channel was 0.635 mm. The nominal mass fluxes used were varied from 200 to 700 kg/m2 s and heat fluxes ranging from 171 to 685 kW/m2 were applied. An inlet fluid temperature of 98 °C and pressure of 125 kPa were maintained at the microchannel entrance. There were six pressure tappings inserted into the channel to measure the local pressures and six thermocouple inserted into the channel block with equally distances to measure the wall local temperatures. The local pressure measurements during flow boiling show a non linear line connecting each local pressure, especially at higher heat fluxes or pressure drops. The non linear local pressure influences the value of the estimated local heat transfer coefficient. The effects of mass flux and heat flux on local heat transfer coefficient are also discussed.
International Nuclear Information System (INIS)
Program FREG series calculate temperature distribution in a fuel rod and the stored energy based on the distribution. The temperature distribution is calculated accordance with the fuel rod irradiation history. The temperature in the fuel rod is severely influenced with gap heat transfer coefficients between fuel pellet surface and cladding inner surface. Enphasis is placed on how to find the gap heat transfer coefficients. FREG-4 is a version-up program of FREG-3. Major modification from FREG-3 is handlings of fission product gas release, which have influences on the gap heat transfer. FREG-4 distingushed fission-product isotopes remained in pellets and fission-product gaseous isotopes released from the pellets, and considers that the released isotopes are transported for plenums to balance whole fuel rod internal pressure and transformed into another isotopes due to decay and the nuetron absorptions. The present report describes modified models from FREG-3 and user's manual for FREG-4. (author)
Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake
Directory of Open Access Journals (Sweden)
Jouni J. Heiskanen
2014-05-01
Full Text Available Lakes and other inland waters contribute significantly to regional and global carbon budgets. Emissions from lakes are often computed as the product of a gas transfer coefficient, k 600 , and the difference in concentration across the diffusive boundary layer at the air–water interface. Eddy covariance (EC techniques are increasingly being used in lacustrine gas flux studies and tend to report higher values for derived k 600 than other approaches. Using results from an EC study of a small, boreal lake, we modelled k 600 using a boundary-layer approach that included wind shear and cooling. During stratification, fluxes estimated by EC occasionally were higher than those obtained by our models. The high fluxes co-occurred with winds strong enough to induce deflections of the thermocline. We attribute the higher measured fluxes to upwelling-induced spatial variability in surface concentrations of CO2 within the EC footprint. We modelled the increased gas concentrations due to the upwelling and corrected our k 600 values using these higher CO2 concentrations. This approach led to greater congruence between measured and modelled k values during the stratified period. k 600 has a well-resolved and ~cubic relationship with wind speed when the water column is unstratified and the dissolved gases well mixed. During stratification and using the corrected k 600 , the same pattern is evident at higher winds, but k 600 has a median value of ~7 cm h?1 when winds are less than 6 m s?1, similar to observations in recent oceanographic studies. Our models for k 600 provide estimates of gas evasion at least 200% higher than earlier wind-based models. Our improved k 600 estimates emphasize the need for integrating within lake physics into models of greenhouse gas evasion.
The influence of a heat transfer coefficient probe on fluid flow near wall
Directory of Open Access Journals (Sweden)
Mareš Martin
2012-04-01
Full Text Available Good knowledge of the convective boundary condition is necessary for finite element analysis of thermal deformation behavior in machine tools. There are a number of correlation equations for natural and forced convection and several correlations for mixed convection. Due to a relatively wide range of dimensions, temperatures and speeds, all regimes of convective heat transfer can be observed in machine tools, including the transition region between laminar and turbulent free convection, characterized by Rayleigh number values ranging between Ra = 108 – 109. Since convection in machine tools is highly influenced by external and internal factors, the heat transfer coefficient characterizing convective heat transfer and its changes has to be evaluated experimentally. An experimental technique for evaluating the heat transfer coefficient on the wall and its changes between the wall and the ambient air, based on an active sensor, is being developed. Since the probe dimensions are not negligible, given the fluid motion structures near the wall which are induced by buoyancy or by forced flow, the influence of the probe has to be considered. Paper deals with latest experimental results and summarizes previous work.
Evaluation of Heat and Mass Transfer Coefficients for R134a/DMF Bubble Absorber
Directory of Open Access Journals (Sweden)
M. Suresh
2011-01-01
Full Text Available The Vapour Absorption Refrigeration System (VARS has generated renewed interest and is being viewed as one of the alternatives for vapour compression refrigeration due to its potential for waste heat utilization. To improve the efficiency of these systems, it is necessary to study heat and mass transfer processes in absorption system components. The absorber, one of the crucial components in VARS is considered for study. Experimental investigation is carried out to study heat and mass transfer characteristics in a glass absorber. A new combination of R134a/DMF is used as the working fluid to overcome the limitations of well known working pairs, ammonia-water and lithium bromide-water. The effects of parameters viz., gas flow rate, solution initial concentration, solution pressure and solution temperature on absorber performance are analyzed. Heat and mass transfer coefficients evaluated from the experiments are compared with the numerical model and it is found that agreement is good. Heat and mass transfer coefficients increase as the gas flow rate, solution initial concentration and solution temperature increase whereas they decrease as the solution pressure increases. Sherwood number and Nusselt number evaluated from the experimental data are compared with those obtained from the numerical correlations developed earlier by the authors.
Comparison of boiling heat transfer coefficient and pressure drop correlations for evaporators
International Nuclear Information System (INIS)
Evaporator design is an important aspect for the HVAC industry. As the demand for more efficient and compact heat exchangers increase, researches on estimation of two-phase flow heat transfer and pressure drop gain importance. Due to complexity of the hydrodynamic and heat transfer of the two-phase flow, there are many experimental studies available for refrigerants int he literature. In this study, a model for boiling heat transfer in a horizontal tube has been developed and the simulation results are compared with experimental ones published in the literature. In these comparisons, heat transfer coefficient is calculated by using Kattan-Thome-Favrat (1998), Shah (1982), Kandilikar (1990), Chaddock and Brunemann (1967) correlations under different operational conditions such as saturation pressure, mass flux, the type of refrigerant and two phase flow pattern. Besides that flow pattern has also been considered in the simulation by using Thome and El Hajal (2002) model. For pressure drop Lockhart-Martinelli (1949), Mueller-Steinhagen-Hack (1986) and Groennerund (1979) correlations are used in simulations. Local vapor quality change at each experimental condition through the model is determined. Roughness is an important parameter for frictional pressure drop. Friction coefficient is determined by using Churchill (1977) model. (author)
Neeman, Binyamin U.; Ohring, George; Joseph, Joachim H.
1989-01-01
This paper examines a parameterization of a quasi-geostrophic eddy transport that takes into account the time variation of eddy transfer coefficients according to Green's (1970) theory. It was found that, in the original eddy transfer relationship of Green, connecting the integral of the northward eddy entropy flux through midlatitudes with the second power of the difference in 500-mb entropy across the region of baroclinic activity, a value of 4 for the exponent is obtained when the temperature gradients at 500 mb are used. When the gradients at 1000 mb are used, an exponent of 1.5 is obtained. The differences in the powers in the eddy transfer relation were explored in a two-level zonally averaged model. It was found that an appropriate choice of power may be of special importance if the model is devised to simulate the seasonal climate cycle or to test astronomical changes inducing different seasonalities.
Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe
International Nuclear Information System (INIS)
In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results.
Immersion condensation on oil-infused heterogeneous surfaces for enhanced heat transfer.
Xiao, Rong; Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N
2013-01-01
Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer. PMID:23759735
Comparison of the Friction-Loss Coefficient for the Gap of Two Contact Surfaces and a Crack
International Nuclear Information System (INIS)
A leak-detection method has been developed by measuring the pressure variation between the inner and outer heat transfer tubes of a double-wall tube steam generator. An experiment was carried out to measure the leak rate in the gap between two surfaces pressed with a hydraulic press in order to simulate the phenomena, and a correlation was determined for the leak rate in a micro gap. However, in the correlation, the gap width and friction coefficient were coupled with the surface roughness, which affects the two parameters. The two parameters were separated using a surface-contact model to develop a correlation for the friction coefficient. The correlation was compared with the existing correlations used for crack analysis. Although the applied ranges of Reynolds numbers were different, the developed correlation for Reynolds numbers of 0.1.0.35 showed similar tendencies to existing correlations used for higher Reynolds numbers
Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy
DEFF Research Database (Denmark)
Fardi Ilkhchy, A.; Jabbari, Masoud
2012-01-01
The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented for correlation between external pressure and heat transfer coefficient. Acceptable agreement with data in literature shows the accuracy of the proposed formula.
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Christensen, Martin Gram
2015-01-01
This paper presents and demonstrates a novel idea of using spherical potatoes as a dispensable, cheap device for determining the fluid-to-particle heat transfer coefficient, hfp in vessel cooking processes. The transmission of heat through the potato can be traced by measuring the distance from the surface to the gelatinization front, which is easy to identify visually. Knowing this distance, the gelatinization temperature, the period of immersion, and the average radius of the potato, the heat transfer coefficient can be calculated. Either a numerical model based on the Finite Element Method (FEM) or an analytical solution of the Fourier equation can be applied for the calculation. The gelatinization temperature of the potatoes used was determined to be 67°C by a direct temperature measurement and by visual inspection of the progression of the gelatinization front. A sensitivity analysis demonstrates that the method is rather precise at relevant values of hfp in vessel cooking (100–300 [W/m2K]), allowing a prediction of the centre temperature within ±0.6°C.
Energy Technology Data Exchange (ETDEWEB)
Sotelo, S.S.; Romero, R.J. [Univ. Autonoma del Estado de Morelos, Cuernavaca Morelos (Mexico). Centro di Investigacion en Ingeneria y Ciencias Aplicadas; Best, R. [Univ. Autonoma de Mexico, Temixco, Morelos (Mexico). Centro de Investigacion en Energie
2009-07-01
A mathematical model was used to characterize the thermal behaviour of a steam generator in an alternative energy upgrade system. A thermodynamic cycle was used to increase the temperatures produced by solar, geothermal, and waste heat from industrial processes. The absorption heat transformer (AHT) process can be used in industrial processes where low temperature heat flows occur. Alternative energy was supplied to the generator where the working fluid was condensed and then transported to the evaporator through an expansion valve. Vapor was then transported to the absorber in order to deliver heat at a higher temperature. The solution was then returned to the generator in order to start the cycle again. A heat exchanger was placed between the absorber and the generator in order to preheat incoming solutions from the generator. The mathematical model was used to simulate heat transfer in the generator in order to determine optimal operating conditions. Heat transfer coefficients were calculated using equations reported for single phase flow. It was concluded that the highest heat transfer coefficients were obtained for a Reynolds number of 2300 with an alternative energy source of 90 degrees C at mass flows of 4 L/m. 33 refs., 14 figs.
Transient measurement of dual channel CICC heat transfer coefficients on a full size ITER conductor
International Nuclear Information System (INIS)
Dual channel Cable-In-Conduit Conductors (CICC) provide low hydraulic resistance and faster central channel circulation, limiting superconductors temperature rise. The Poloidal Field Insert Sample (PFIS) was tested in the SULTAN facility to evaluate the thermal coupling between the CICC channels upon an experimental heat transfer coefficient assessment. Simple assumptions on the flow homogeneous central and annular temperatures, no jacket conduction, no steel inertia and diffusivity lead to a one-dimensional thermal model fully solved in its transient response to a Heavy-side temperature evolution at the inlet, using a Laplace transformation. Transient temperature step data fitted with the analytical resolution provide heat transfer coefficients as a function of mass flow rate, compared to crude predictions and steady state evaluations, where annular and central temperatures are homogenized in compliance with the CICC heat transfer characteristic length. The transient measurements are subject to the inertia and diffusivity of the conductor, whereas comparable steady state measures suffer from annular isothermal assumption. Recommendations are made for the thermohydraulic instrumentation of future conductor samples. (authors)
International Nuclear Information System (INIS)
In the Loss-of-RHR accident during mid-loop operation reflux condensation in U-tube riser is experimentally studied. The present experimental study handles with the reflux condensation in the presence of noncondensable gas in a vertical tube. The main interest is to investigate the parametric effects such as inlet air mass fraction, system pressure and inlet steam flow rate on reflux condensation heat transfer. The test facility is mainly composed of two parts: an air-steam mixture generation part and a reflux condensation part(test section). Air is used as a noncondensable gas. Experiments are performed under the system pressure of 1 ? 2.5bar, inlet steam flow rate of 1.04 ? 2.15kg/hr and inlet air mass fraction of 0 ? 57.9%. From experimental results, several characteristics of parametric effects are confirmed. The presence of air causes a decrease in heat transfer coefficients and, as a result, increases the active condensation length. As the inlet steam flow rate increases, the active length slightly increases during reflux condensation. As the system pressure increases, the active condensation length somehow decreases with an increase in heat transfer coefficients in that zone. And the flooding limit for inlet mixture flow rate is much less than that of Wallis' flooding formula
Radiative transfer through arrays of discrete surfaces
International Nuclear Information System (INIS)
Radiant transport involving arrays of discrete surfaces constitutes one of the major unresolved problems in the field of radiation heat transfer. This paper discusses the requirements for experimental validation of a general Monte Carlo solution to this class of problems. This work is a collaborative effort between Oregon State University, where the experimental portion is being accomplished, and the Pacific Northwest Laboratory, which is responsible for the Monte Carlo simulation. The design and calibration of a simple, compact, and flexible instrument for direct measurement of bidirectional reflectance are presented in some detail. The capability to measure full bidirectional reflectance, as provided by this instrument, is essential to an accurate portrayal of surface properties in a Monte Carlo simulation. Measured data for a common flat white paint are presented and clearly demonstrate the need for accurate and complete surface property information. Applications include volumetric air heating solar central receivers, ceramic fabrics, and fibrous insulation
Mechanistic model of iodine mass transfer at pool surfaces
International Nuclear Information System (INIS)
Mass transfer of molecular iodine (I2) at the water pool–gas interface can be modeled by means of a water surface film renewal model superimposed to the established two-film theory, where the water-side I2 mass transfer coefficient kw is related to the I2 molecular diffusivity in water D and the air–water contact time a according to The present paper describes a mechanistic approach to determine the contact time from the water flow distribution. The method makes use of a numerical simulation of the poolwater flow, and a numerical evaluation of the contact time distribution at the pool surface. Owing to the numerical treatment it can be applied to pool geometries of any kind, which makes it applicable for nuclear reactor safety studies in general kw=?(D/?a) The present paper describes a mechanistic approach to determine the contact time from the water flow distribution. The method makes use of a numerical simulation of the poolwater flow, and a numerical evaluation of the contact time distribution at the pool surface. Owing to the numerical treatment it can be applied to pool geometries of any kind, which makes it applicable for nuclear reactor safety studies in general
Marinucci, C; Bruzzone, P; Stepanov, B
2007-01-01
This paper describes a new method to determine the equivalent heat transfer coefficients, i.e., radial and azimuthal, in CICC’s with parallel cooling channels. The method is based on the measurement of the steady state temperature response to a step heating. The experiment is modelled by a set of transport equations for the temperature distribution that contain explicitly the parametric dependence on the transverse heat transfer coefficients. The equations are solved analytically and the values of the equivalent transverse heat transfer coefficients are obtained as the best fit of the experimental temperature distributions. We show the results obtained with the method by application to a short length sample experiment in the SULTAN test facility using an ITER-type CICC with special instrumentation, and with heaters to generate a variety of heat slugs. The values of heat transfer coefficient are consistent with expected values, based in particular on the theory of dispersion in porous media.
Mass Transfer Coefficient During Cathodic Protectionof Low Carbon Steel in Seawater
Ameel Mohammed Rahman; Anees Abdullah Khadom; Khalid W. Hameed
2009-01-01
The aim of this research is to calculate mass transfer coefficient, kd, during cathodic protection of low carbon steel in neutral seawater (3.5% W/V NaCl in distilled water with pH = 7). Two types of cathodic protection were used:First: Sacrificial anode cathodic protection (SACP) were a pipeline of steel carrying seawater using zinc as a sacrificial anode and with variable temperatures ranged (0 ? 45oC) and volumetric flow rate ranged (5 ? 900 lit/hr). It was found that the kd increases with...
Czech Academy of Sciences Publication Activity Database
Kárászová, Magda; Šim?ík, Miroslav; Friess, K.; Randová, A.; Jansen, J. C.; R?ži?ka, Marek; Sedláková, Zuzana; Izák, Pavel
2013-01-01
Ro?. 118, 30 OCT (2013), s. 255-263. ISSN 1383-5866 R&D Projects: GA ?R GAP106/10/1194; GA MŠk(CZ) 7C11009 Grant ostatní: RFCS(XE) RFCR-CT-2010-00009; INP(IT) PON01_01840; HA MŠk(CZ) CZ.1.05/2.1.00/03.0071 Institutional support: RVO:67985858 Keywords : biogas purification * supported ionic liquid membranes * mass transfer coefficients Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.065, year: 2013
Experimental apparatus for measuring heat transfer coefficients by the Wilson plot method
Energy Technology Data Exchange (ETDEWEB)
Fernandez-Seara, Jose [Area de Maquinas y Motores Termicos, Escuela Superior de Ingenieros Industriales, Campus Lagoas-Marcosende, No 9, 36200 Vigo (Spain); UhIa, Francisco Jose [Area de Maquinas y Motores Termicos, Escuela Superior de Ingenieros Industriales, Campus Lagoas-Marcosende, No 9, 36200 Vigo (Spain); Sieres, Jaime [Area de Maquinas y Motores Termicos, Escuela Superior de Ingenieros Industriales, Campus Lagoas-Marcosende, No 9, 36200 Vigo (Spain); Campo, Antonio [Mechanical Engineering Department, University of Vermont, Burlington, VT 05405 (United States)
2005-05-01
The Wilson plot is a technique to estimate the film coefficients in several types of heat transfer processes and to obtain general heat transfer correlations. This method is an outstanding tool in practical applications and in laboratory research activities that involve analysis of heat exchangers. Moreover, the application of this method is simple enough to be taught in laboratory practices for students at university and doctoral level of physics and engineering. Therefore, an experimental apparatus has been designed and built in our laboratory that allows the students to carry out experiments based on the application of the Wilson plot method. In this note, the principles of the method are explained, the experimental apparatus is described and representative results of the experimental data taken from the apparatus and the application of the Wilson plot method are shown. (note)
Experimental apparatus for measuring heat transfer coefficients by the Wilson plot method
International Nuclear Information System (INIS)
The Wilson plot is a technique to estimate the film coefficients in several types of heat transfer processes and to obtain general heat transfer correlations. This method is an outstanding tool in practical applications and in laboratory research activities that involve analysis of heat exchangers. Moreover, the application of this method is simple enough to be taught in laboratory practices for students at university and doctoral level of physics and engineering. Therefore, an experimental apparatus has been designed and built in our laboratory that allows the students to carry out experiments based on the application of the Wilson plot method. In this note, the principles of the method are explained, the experimental apparatus is described and representative results of the experimental data taken from the apparatus and the application of the Wilson plot method are shown. (note)
Leblay, P.; Henry, J. F.; Caron, D; Leducq, D.; Bontemps, A.; Fournaison, L.
2012-01-01
A methodology has been developed based on periodic excitation by Joule effect and infrared thermography measurement. It has been applied to measure heat transfer coefficients of water flowing in a round tube and in a multiport-flat tube. Models were developed to deduce heat transfer coefficient from wall temperature amplitude and heat flux measurement. For the round tube and for the multiport flat tubes, Reynolds number investigated ranges respectively from 2000 to 14000 and from 800 to 10000...
Heat and mass transfer rates during flow of dissociated hydrogen gas over graphite surface
Nema, V. K.; Sharma, O. P.
1986-01-01
To improve upon the performance of chemical rockets, the nuclear reactor has been applied to a rocket propulsion system using hydrogen gas as working fluid and a graphite-composite forming a part of the structure. Under the boundary layer approximation, theoretical predictions of skin friction coefficient, surface heat transfer rate and surface regression rate have been made for laminar/turbulent dissociated hydrogen gas flowing over a flat graphite surface. The external stream is assumed to be frozen. The analysis is restricted to Mach numbers low enough to deal with the situation of only surface-reaction between hydrogen and graphite. Empirical correlations of displacement thickness, local skin friction coefficient, local Nusselt number and local non-dimensional heat transfer rate have been obtained. The magnitude of the surface regression rate is found low enough to ensure the use of graphite as a linear or a component of the system over an extended period without loss of performance.
International Nuclear Information System (INIS)
Extensive studies on transfer of 131I through grass-cow-milk pathway after the Chernobyl accident were reported. But, under nor mal operational conditions of a power reactor, 131I is not present in measurable concentration in environmental matrices around a nuclear power generating station. Hence, database on 131I transfer coefficients for grass-cow-milk pathway in equilibrium conditions in the environment of a nuclear power plant are sparse. One of method to estimate the equilibrium transfer coefficient is to use stable iodine, which is present naturally in very low levels in the environmental matrices. By measuring the concentration of stable iodine concentration in grass and cow milk, the grass-to-milk transfer coefficient of iodine can be estimated. Since the metabolism of stable and radioiodine is same, the data obtained for transfer coefficient of stable iodine could be used for predicting the transfer for radioiodine to cow milk. The measurement of stable iodine in the environmental sample is very challenging because of its extremely low concentration. Neutron Activation Analysis (NAA) can be used to estimate stable iodine in the environment matrices after suitably optimizing the condition to minimize interferences. This paper presents the results of a systematic study on the transfer coefficients for grass-cow milk pathway of iodine in normal (equilibrium) situations as well as for a postulated (simulated) emergency condition in Kaiga region
Heat Transfer and Pressure Drop with Rough Surfaces, a Literature Survey
International Nuclear Information System (INIS)
This literature survey deals with changes in heat transfer coefficient and friction factor with varying nature and degree of roughness. Experimental data cover mainly the turbulent flow region for both air and water as flow mediums. Semiempirical analysis about changes in heat transfer coefficient due to roughness has been included. An example of how to use these data to design a heat exchanger surface is also cited. The extreme case of large fins has not been considered. Available literature between 1933 - 1963 has been covered
Sargison, J E; Guo, S M; Oldfield, M L; Rawlinson, A J
2001-05-01
The heat transfer coefficient and adiabatic effectiveness of cylindrical, fan shaped holes and a slot are presented for the region zero to 50 diameters downstream of the holes. Narrow-band liquid crystals were used on a heated flat plate with heated air coolant. These parameters have been measured in a steady state, low speed facility at engine representative Reynolds number based on hole diameter and pressure difference ratio (ideal momentum flux ratio). The aerodynamic loss due to each of the film cooling geometries has been measured using a traverse of the boundary layer far downstream of the film cooling holes. Compared to the cylindrical holes, the fan shaped hole case showed an improvement in the uniformity of cooling downstream of the holes and in the level of laterally averaged film cooling effectiveness. The fan effectiveness approached the slot level and both the fan and cylindrical hole cases show lower heat transfer coefficients than the slot and non film cooled cases based on the laterally averaged results. The drawback to the fan shaped hole was that the aerodynamic loss was significantly higher than both the slot and cylindrical hole values due to inefficient diffusion in the hole exit expansion. PMID:11460648
Transfer coefficient of 137Cs from feed to cow milk in tropical region Kaiga (India)
International Nuclear Information System (INIS)
In the transport model for the prediction of the concentration of 137Cs in milk, the transfer coefficient from feed to milk, Fm, is an important parameter. Site-specific transfer coefficient from feed to cow's milk, for 137Cs in the Kaiga environment, a nuclear power station site in India, determined over a period of 10 y is presented in this paper. The value is determined from 137Cs concentration in milk and grass samples of the Kaiga region and the result ranged from 6.43 E-03 to 1.09 E-02 d l-1 with a geometric mean value of 8.0 E-03 d l-1. The result is compared with that for 40K, determined concurrently at the same region and ranged from 3.06 E-03 to 3.48 E-03 d l-1 with a geometric mean value of 3.26 E-03 d l-1. This parameter is quite useful in decision-making for implementing countermeasures during a large area contamination with 137Cs in tropical areas like Kaiga. (authors)
Wan, Zhengming; Dozier, Jeff
1992-01-01
The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.
A time-domain estimation of wall conduction transfer function coefficients
Energy Technology Data Exchange (ETDEWEB)
Davies, M.G. [Univ. of Liverpool (United Kingdom). School of Architecture and Building Engineering
1996-11-01
The wall and roof transfer function coefficients, b{sub n} and d{sub n}, listed in the 1993 ASHRAE Fundamentals Handbook, have up to now been derived using laplace and Z-transform methods. This paper shows that they can be readily evaluated using straightforward time-domain solutions of the Fourier continuity equation. These include the response of a wall to a ramp increase in temperature and its transient response. The values of d{sub n} can be found from the first few terms in the series of wall decay times in the transient solution. The solutions are combined using a form of Fourier analysis. Appropriate layer transmission matrices enable one to find the wall`s overall characteristics readily. The wall response factors {phi}{sub j} can thus be found. The b{sub n} transfer coefficients are related to the {phi}{sub j} and d{sub n} values. The approach is illustrated using the data for wall group 6. Allowing for conversion from I-P to SI units, the present approach gives results that are almost identical to those listed. It shows, however, that the performance of the coefficients is very specific to the wall from which they were derived. The b{sub n} and d{sub n} values listed in the Handbook permit an estimate to be made of the wall response factors, including the time of peak flow and the first decay time. For heavy walls, however, values beyond d{sub 6} may be needed.
Distribution coefficient Kd in surface soils collected in Aomori prefecture
International Nuclear Information System (INIS)
Soil-solution distribution coefficients (Kds), which are the ratio of an element concentration in a soil solid phase to that in a solution phase, for 32 elements in Andosols, Wet Andosols and Gleyed Andosols collected throughout Aomori Prefecture were determined. A dried soil sample was mixed with a 10-fold amount of pure water in a PPCO centrifuge tube, and then gently shaken for 24 h. The Kd values were obtained by measurement of element concentrations in solid and solution phases (batch method). The Kd values in this work were up to three orders of magnitude higher than the IAEA reported values, and their 95% confidence intervals were within two orders of magnitude. Most Kd values of elements were decreasing with increasing electrical conductivity of the solution phase. The Kd of Ca had a good correlation with that of Sr. However, the correlation between the Kds of K and Cs was not good. The Kd values were also determined by another method. The soil solutions were separated from the fresh soil samples by means of high speed centrifuging. The Kd values were calculated from the element concentration in solid phase and soil solution (centrifugation method). The Kd values obtained by the centrifugation method agreed within one order of magnitude with those by the batch method, and both variation patterns in elements correlated well. (author)
Connection coefficients for cold plasma wave propagation near metallic surfaces
International Nuclear Information System (INIS)
Sheaths tend to form when immersing metallic objects in plasmas. As it avoids the need to capture the sheath details, which occur on the Debye length scale while antennas are typically various orders of magnitude larger, the sheath boundary condition due to D'Ippolito and Myra (2006 Phys. Plasmas 13 102508, 2008 Phys. Plasmas 15 102501) offers antenna designers a major reduction in the numerical problem size they face. The sheath boundary condition was derived by making a number of simplifying assumptions to enable finding an analytical approximation of the conditions rapidly oscillating waves have to satisfy beyond the sheath that forms close to such objects. This paper discusses the solution of the cold plasma wave equation for sheath relevant density profiles, e.g. highlighting the role of the orientation of the static magnetic field and of oblique incidence, and underlining the impact the density profile has on the wave physics. It illustrates that the cross-talk between the waves impinging on and those excited at the wall and in the sheath sensitively depends on a number of parameters. The 2 × 2 connection coefficient matrix that is numerically obtained captures the sheath region fast time scale wave physics for a given density profile. When supplemented with a satisfactory model for the slow time scale variation it is a numerical tool that permits upgrading the realism of the fast time scale wave physics contained in the sheath boundary condition and that can help delimiting the range of applicability of simplified models, and assessing if a sufficiently general set of boundary conditions to describe the effect of the sheath can at all be constructed. (paper)
THE EFFECT OF THE ALUMINIUM ALLOY SURFACE ROUGHNESS ON THE RESTITUTION COEFFICIENT
Directory of Open Access Journals (Sweden)
Stanis?aw B?awucki
2015-08-01
Full Text Available The paper presents the results of research on the effect of the surface roughness of aluminum alloy on its coefficient of restitution. It describes the current method of finishing the workpiece surface layer after cutting and innovative measuring device which was used in the research. The material used in the research was aluminium alloy EN AW 7075. The paper also presents a relationship between the coefficient of restitution and surface roughness of the milled samples as well as impressions left by bead in function of velocity and a sample surface roughness.
Heat transfer coefficient calculation for analysis of ITER shield block using CFX and ANSYS
International Nuclear Information System (INIS)
Highlights: ? Benchmark HTC modeling in CFX and compare this modeling with empirical formulas. ? Given the error formulas derived from theory. ? Benchmark HTC modeling in ANSYS and the results is consistent with the conclusion of error estimate from theory. - Abstract: In thermal-mechanical analysis of ITER shield block using ANSYS code, it needs the real heat transfer coefficient (HTC) values which are computed by CFX. Because two kinds of HTC values can be gotten from CFX and which has some difference with ANSYS, so it is necessary to estimate the error caused by HTC transferred from CFX to ANSYS. In this paper, HTC values got from CFX was firstly benchmarked with the results got from empirical formulas, then estimated the error caused by HTC transferred from theory and gave the expressions of the error, thirdly benchmark work of ANSYS results in 4 cases was done, then compared the error with former error estimated formula derived from theory. In the end, conclusions will be given based on above benchmark works.
With the cost of water quality research at the watershed level, modeling has become an important tool for researchers. When modeling nitrate transport within drainage networks, denitrification within the sediments needs to be accounted for. Birgand et al. developed an equation using a term called a ...
Electron transfer in gas surface collisions
International Nuclear Information System (INIS)
In this thesis electron transfer between atoms and metal surfaces in general is discussed and the negative ionization of hydrogen by scattering protons at a cesiated crystalline tungsten (110) surface in particular. Experimental results and a novel theoretical analysis are presented. In Chapter I a theoretical overview of resonant electron transitions between atoms and metals is given. In the first part of chapter II atom-metal electron transitions at a fixed atom-metal distance are described on the basis of a model developed by Gadzuk. In the second part the influence of the motion of the atom on the atomic charge state is incorporated. Measurements presented in chapter III show a strong dependence of the fraction of negatively charged H atoms scattered at cesiated tungsten, on the normal as well as the parallel velocity component. In chapter IV the proposed mechanism for the parallel velocity effect is incorporated in the amplitude method. The scattering process of protons incident under grazing angles on a cesium covered surface is studied in chapter V. (Auth.)
Computer Simulation of Electron Transfer at Hematite Surfaces
International Nuclear Information System (INIS)
Molecular dynamics simulations in combination with ab initio calculations were carried out to determine the rate of electron transfer in bulk hematite (?-Fe2O3) and at two low-index surfaces, namely the (012) and (001) surfaces. The electron transfer reactions considered here involve the II/III valence interchange between nearest-neighbor iron atoms. Two electron transfer directions were investigated namely the basal plane and c direction charge transfers. Electron transfer rates obtained in bulk hematite were in good agreement with ab initio electronic structure calculations thus validating the potential model. The surfaces were considered both in vacuum and in contact with an equilibrated aqueous solution. The reorganization energy is found to increase significantly at the first surface layer and this value is little affected by the presence of water. In addition, in the case of the (012) surface, the electronic coupling matrix element for the topmost basal plane transfer was calculated at the Hartree-Fock level and was found to be weak compared to the corresponding charge transfer in the bulk. Therefore, most surfaces show a decrease in the rate of charge transfer at the surface. However, where iron atoms involved in the charge transfer reaction are directly coordinated to water molecules, water lowers the free energy of activation to a great extent and provides a large driving force for electrons to diffuse toward the bulk thus opposing the intrinsic surface effect. The surfaces considered in this work show different charge transfer properties. Hematite has been shown to exhibit anisotropic conductivity and thus different surfaces will show different intra- and inter-layer rates depending on their orientation. Moreover, the calculations of charge transfers at the hydroxyl- and iron-terminated (001) surfaces revealed that surface termination has a significant effect on the charge transfer parameters in the vicinity of the surface. Finally, our findings indicate that undercoordinated terminal iron atoms could act as electron traps at the surface
Numerical study of turbulent fluid flow and heat transfer in lateral perforated extended surfaces
International Nuclear Information System (INIS)
Numerical study has been performed in this study to investigate the turbulent convection heat transfer on a rectangular plate mounted over a flat surface. Thermal and fluid dynamic performances of extended surfaces having various types of lateral perforations with square, circular, triangular and hexagonal cross sections are investigated. RANS (Reynolds averaged Navier–Stokes) based modified k–? turbulence model is used to calculate the fluid flow and heat transfer parameters. Numerical results are compared with the results of previously published experimental data and obtained results are in reasonable agreement. Flow and heat transfer parameters are presented for Reynolds numbers from 2000 to 5000 based on the fin thickness. - Highlights: • Lateral perforation shape has significant effects on fin thermal performance. • Solid fins have higher skin friction coefficient value than the perforated ones. • Triangular perforated fins have the lowest skin friction coefficient value. • Hexagonal perforated fins show better thermal and fluid dynamic performances
Distribution coefficient and transfer factor of stable iodine in agricultural soils in Aomori, Japan
International Nuclear Information System (INIS)
Soil-to-solution distribution coefficient (Kd) and soil-to-plant transfer factor (TF) were determined for agricultural soils and selected plants in Aomori Prefecture, Japan, by means of analysis of stable I in soil and plant samples. The concentration of I in the soil samples varied between 0.52 and 82.8 mg kg-1 (geometric mean of 4.4 mg kg-1). The Kd, which was defined as the ratio of I concentration in soil to that in water extracted from the soil, was 1.5 x 103 in geometric mean (L/kg). The TF value was defined as the ratio of I concentration in plant to that in soil. Geometric means of the TF on dry weight base obtained in this study were 3.2 x 10-2 for komatsuna, 2.0 x 10-2 for Japanese radish and 2.3 x 10-2 for pasture grass. (author)
Local heat transfer coefficients for condensation in stratified countercurrent steam-water flows
International Nuclear Information System (INIS)
A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel inclined 33 deg to the horizontal. The variables in this experiment were the inlet water and steam flow rates, and the inlet water temperature. Condensation heat transfer coefficients were determined as functions of local steam and water flow rates, and the degree of subcooling. Correlations are given for the local Nusselt number for the smooth and for the rough interface regimes, and also for the dimensionless wave amplitude. A turbulence-centered model is also developed. It is shown that better agreement with the data can be obtained if the characteristic scales in the turbulent Nusselt number and Reynolds numbers are related to measured interfacial parameters rather than the bulk flow parameters. The important effect of interfacial shear, missing in previous eddy-transport models, is thus implicitly included
Effect factors of heat transfer coefficient between hollow glass microsphere and furnace atmosphere
International Nuclear Information System (INIS)
In order to achieve an effective control of the heat transfer coefficient (hq) between microsphere and furnace atmosphere in the fabrication of hollow glass micro-sphere by sol-gel technology, the effects of component percentage, temperature and total pressure of gas mixture on hq are studied. Further, the influences of diameter and wall thickness of hollow glass microsphere on hq are also investigated. The results show that in the range of component percentage, temperature and pressure of gas mixture commonly used in the fabrication of hollow glass microsphere by sol-gel technology, the temperature and total pressure of gas mixture and the wall thickness of hollow glass microsphere have little influence on hq, but hq significantly increases with the volume fraction of helium in the furnace atmosphere and significantly decreases with increasing of microsphere diameter. (authors)
Determination of the interfacial heat transfer coefficient in the hot stamping of AA7075
Directory of Open Access Journals (Sweden)
Liu Xiaochuan
2015-01-01
Full Text Available The interfacial heat transfer coefficient (IHTC is a key parameter in hot stamping processes, in which a hot blank is formed and quenched by cold dies simultaneously. The IHTC should therefore be identified and used in FE models to improve the accuracy of simulation results of hot stamping processes. In this work, a hot stamping simulator was designed and assembled in a Gleeble 3800 thermo-mechanical testing system and a FE model was built in PAM-STAMP to determine the IHTC value between a hot aluminium alloy 7075 blank and cold dies. The IHTC was determined at different contact pressures under both dry and lubricated (Omega-35 conditions. In addition, a model to calculate the IHTC value at different contact pressures and area densities of lubricant was developed for the hot stamping process.
DEFF Research Database (Denmark)
Nielsen, Anders Michael; Nielsen, Lars Peter
2009-01-01
A membrane inlet mass spectrometer (MIMS) was used in combination with a developed computer model to study and improve management of a biofilter (BF) treating malodorous ventilation air from a meat rendering facility. The MIMS was used to determine percentage removal efficiencies (REs) of selected sulfur gases and to provide toluene retention profiles for the model to determine the air velocity and overall mass-transfer coefficient of toluene. The mass-transfer coefficient of toluene was used as a reference for determining the mass transfer of sulfur gases. By presenting the model to scenarios of a filter bed with a consortium of effective sulfur oxidizers, the most likely mechanism for incomplete removal of sulfur compounds from the exhaust air was elucidated. This was found to be insufficient mass transfer and not inadequate bacterial activity as anticipated by the manager of the BF. Thus, knowing the relationship between mass-transfer coefficients and air velocity for a given type of BF allows for an improved dimensioning and managing of this and similar BFs. This research demonstrates that it is possible to estimate mass-transfer coefficients and air velocity in BFs using MIMS in combination with computer modeling. Udgivelsesdato: February
SAFARI 2000 Surface Atmospheric Radiative Transfer (SMART), Dry Season 2000
National Aeronautics and Space Administration — ABSTRACT: Surface-sensing Measurements for Radiative Transfer (SMART) and Chemical, Optical, and Microphysical Measurements of In-situ Troposphere (COMMIT) consist...
Simulation of Convective Heat-Transfer Coefficient in a Buried Exchanger
Directory of Open Access Journals (Sweden)
Taoufik Mnasri
2008-01-01
Full Text Available This study presents analytical models allowing to study a forced convection laminar flow in non-established dynamic and thermic regimes. We treated a flow in a bitubular exchanger in permanent thermal contact with a semi-infinite medium, such as the ground. The wall temperature as well as the wall heat flux evolve in the course of time until a quasi-steady mode. The theoretical method is original because it uses Green's functions method to determine the analytical solutions of the heat propagation equation on the wall during the heating phase. These analytical solutions allow to identify the temperature distribution versus time. The complexity of the system geometry as well as the infinity of the medium surrounding the exchanger make the traditional methods of numerical resolution unable to solve the problem. We used, to solve it, the finite volume method coupled with the finite element method at the boundary. We studied the effect of Reynolds number, the fluid entry temperature and the transfer duration on the axial evolution of the heat transfer coefficient. We illustrated also the profile of the temperature field in the fluid medium.
Experimental study on convective heat transfer coefficient around a vertical hexagonal rod bundle
Makhmalbaf, M. H. M.
2012-06-01
Research on convective heat transfer coefficient around a rod bundle has many diverse applications in industry. So far, many studies have been conducted in correlations related to internal and turbulent fully-developed flow. Comparison shows that Dittus-Boelter, Sieder-Tate and Petukhov have so far been the most practical correlations in fully-developed turbulent fluid flow heat transfer. The present study conducts an experimental examination of the validity of these frequently-applied correlations and introduces a manufactured test facility as well. Due to its generalizibility, the unique geometry of this test facility (hexagonal arranged, 7 vertical rods in a hexagonal tube) can fulfil extensive applications. The paper also studies the major deviation sources in data measurements, calibrations and turbulence of fluid flow in this. Finally, regarding to sufficient number of experiments in a vast fluid mean velocity range (3,800 < Re < 40,000), a new curve and correlation are presented and the results are compared with the above mentioned commonly-applied correlations.
Convective Heat Transfer from Castings of Ice Roughened Surfaces in Horizontal Flight
Dukhan, Nihad; Vanfossen, G. James, Jr.; Masiulaniec, K. Cyril; Dewitt, Kenneth J.
1995-01-01
A technique was developed to cast frozen ice shapes that had been grown on a metal surface. This technique was applied to a series of ice shapes that were grown in the NASA Lewis Icing Research Tunnel on flat plates. Eight different types of ice growths, characterizing different types of roughness, were obtained from these plates, from which aluminum castings were made. Test strips taken from these castings were outfitted with heat flux gages, such that when placed in a dry wind tunnel, they could be used to experimentally map out the convective heat transfer coefficient in the direction of flow from the roughened surfaces. The effects on the heat transfer coefficient for parallel flow, which simulates horizontal flight, were studied. The results of this investigation can be used to help size heaters for wings, helicopter rotor blades, jet engine intakes, etc., or de-icing for anti-icing applications where the flow is parallel to the iced surface.
Directory of Open Access Journals (Sweden)
N. Parsafar
2014-02-01
Full Text Available In this study, a completely randomized experiment was designed with five irrigation treatments and three replicates. The irrigation programs were raw wastewater (T1, treated wastewater (T2, a combination of 50% raw wastewater and 50% fresh water (T3, a combination of 50% treated wastewater and 50% fresh water (T4, and fresh water (T5. The experiments were run within a greenhouse. The lysimeters were built up in September 2009 and they were filled with a two layer soil. The upper (30 cm and lower (40 cm layers were sandy loam and sandy clay loam, respectively. The results showed that the effects of watering treatments on transfer coefficients of heavy metals from soil to shoots (except Cd and tubers of potato (except Zn and Cu were significant (p <0.01. Maximum and minimum transfer coefficients of heavy metals were observed in the (T1 and (T5 treatments, respectively. Also, the transfer coefficients of Cd from soil to shoots were lower than tubers. In the case of Zn, Cu and Pb, transfer coefficients from soil to tubers were lower than shoots. In this study, the maximum transfer coefficients to shoots were Cd (0.331-0.463, Zn (0.383-0.230, Cu (0.173-0.386 and Pb (0.003-0.057, respectively. Maximum transfer coefficients toward tubers (except T5 were Cd (0.439-0.572, Cu (0.081-0.138, Zn (0.170-0.217 and Pb (0-0.017, respectively. The combination of wastewater and fresh water use in short-term irrigation might be feasible, but a heavy metal monitoring program is necessary.
Ultrasonic Heat Transfer Enhancement with Obstacle in Front of Heating Surface
Nomura, Shinfuku; Nakagawa, Masafumi; Mukasa, Shinobu; Toyota, Hiromichi; Murakami, Koichi; Kobayashi, Ryousuke
2005-06-01
Heat transfer enhancement using a horn-type transducer was carried out in the natural convection region while a flat plate was used as a wall-like obstacle in front of the heating surface. Three types of plate were used as obstacles: acrylic, aluminum, and Styrofoam. A horn tip of 6 mm diameter and 60.7 kHz was used as the ultrasonic transducer. The acoustic cavitation jet induced by the ultrasonic vibration exhibited the same tendency as the axisymmetric free jet. The acoustic jet from the horn tip was shut out by the flat plate; however, the ultrasound passed through the flat plate and transferred the flow effect and agitation effect to the area behind the plate. By applying ultrasonic vibration, the heat transfer coefficient of the heating surface behind the flat plate was increased by up to threefold. The heat transfer coefficient decreased as the thickness of the flat plate increased. The heat transfer coefficient was the highest for the acrylic plate, then the aluminum plate, and lowest for the Styrofoam plate.
International Nuclear Information System (INIS)
Recent studies into droplet impingement heat transfer have demonstrated that it has great potential for providing high heat flux cooling in areas such as thermal management of electronics. The wettability of the surface affects the flow dynamics of the impingement process and the resulting heat transfer. In this study, the effect of surface wettability on carbon nanotube water-based nanofluid droplet impingement heat transfer has been studied and compared with water. Superhydrophobic or hydrophilic coatings are applied on one face of monocrystalline silicon wafers (the drop impinges on this face) while the other face is painted matt black to permit infrared thermography. The silicon wafer is preheated to 40 °C and a single droplet impinges normally on the top facing coated surface of the monocrystalline silicon wafer. The inverse heat conduction problem has been solved using the measured black face temperature. For both the water and nanofluid droplets, the convective heat transfer coefficient reduces with the decrease in surface wettability. It is found that the nanofluid produce a significantly higher convective heat transfer coefficient during droplet impingement than water, with the enhancement increasing with increasing wettability.
Relation between the temperature coefficient of surface tension and phase diagrams
Koliverdov, V. F.
2010-08-01
An equation determining the relation between the temperature coefficient of surface tension and crystallization temperature was obtained. The equation was substantiated experimentally for solutions of NaOH and ZnCl2. The rule governing the alternation of structures in phase diagrams was found. A relation between phase diagram structures and structures in adsorbed surface layers of liquid solutions at microconcentrations of surface-active components was derived.
International Nuclear Information System (INIS)
Authors performed post-CHF experiments under wider pressure ranges of 2 MPa - 18 MPa, wider mass flux ranges of 33 kg/m2s - 1651 kg/m2s and wider superheat of heaters up to 500 K in comparison to experimental ranges at previous post-CHF experiments. Data on boiling transition, critical heat flux and post-CHF heat transfer coefficient were obtained. Used test section was 4x4-rod bundle with heaters, which diameter and length were the same as those of BWR nuclear fuels. As the result of the experiments, it was found that the boiling transition occurred just below several grid spacers, and that the fronts of the boiling transition region proceeded lower with increase of heated power. Heat transfer was due to nucleate boiling above grid spacers, while it was due to film boiling below grid spacers. Consequently, critical heat flux is affected on the distance from the grid spacers. Critical heat flux above the grid spacers was about 15% higher than that below the grid spacers, by comparing them under the same local condition. Heat transfer by steam turbulent flow was dominant to post-CHF heat transfer, when superheat of heaters was sufficiently high. Then, post-CHF heat transfer coefficient was predicted with heat transfer correlations for single-phase flow. On the other hand, when superhead of heaters was not sufficiently high, post-CHF heat transfer coefficient was higher than the prediction with heat transfer correlations for single-phase flow. Mass flux effect on post-CHF heat transfer coefficient was described by standardization of post-CHF heat transfer coefficient with the prediction for single-phase flow. However, pressure effect, superheat effect and effect of position were not described. Authors clarified that those effects could be described with functions of heater temperature and position. Post-CHF heat transfer coefficient was lowest just blow the grid spacers, and it increased with the lower positions. It increased by about 30% in one span of the grid spacers, which length was about 50 cm. (author)
Energy Technology Data Exchange (ETDEWEB)
Iguchi, Tadashi; Anoda, Yoshinari [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Iwaki, Chikako [Toshiba Corp., Tokyo (Japan)
2002-02-01
Authors performed post-CHF experiments under wider pressure ranges of 2 MPa - 18 MPa, wider mass flux ranges of 33 kg/m{sup 2}s - 1651 kg/m{sup 2}s and wider superheat of heaters up to 500 K in comparison to experimental ranges at previous post-CHF experiments. Data on boiling transition, critical heat flux and post-CHF heat transfer coefficient were obtained. Used test section was 4x4-rod bundle with heaters, which diameter and length were the same as those of BWR nuclear fuels. As the result of the experiments, it was found that the boiling transition occurred just below several grid spacers, and that the fronts of the boiling transition region proceeded lower with increase of heated power. Heat transfer was due to nucleate boiling above grid spacers, while it was due to film boiling below grid spacers. Consequently, critical heat flux is affected on the distance from the grid spacers. Critical heat flux above the grid spacers was about 15% higher than that below the grid spacers, by comparing them under the same local condition. Heat transfer by steam turbulent flow was dominant to post-CHF heat transfer, when superheat of heaters was sufficiently high. Then, post-CHF heat transfer coefficient was predicted with heat transfer correlations for single-phase flow. On the other hand, when superhead of heaters was not sufficiently high, post-CHF heat transfer coefficient was higher than the prediction with heat transfer correlations for single-phase flow. Mass flux effect on post-CHF heat transfer coefficient was described by standardization of post-CHF heat transfer coefficient with the prediction for single-phase flow. However, pressure effect, superheat effect and effect of position were not described. Authors clarified that those effects could be described with functions of heater temperature and position. Post-CHF heat transfer coefficient was lowest just blow the grid spacers, and it increased with the lower positions. It increased by about 30% in one span of the grid spacers, which length was about 50 cm. (author)
International Nuclear Information System (INIS)
In safety evaluation of a fuel rod, estimation of the stored energy in the fuel rod is indispensable. For this estimation, the temperature distribution in the fuel rod is calculated. Most important in determination of the temperature distribution is the gap heat transfer coefficient (gap conductance) between pellet surface and cladding inner surface. Under fuel rod operating condition, the mixed gas in the gap is composed of He, Xe and Kr. He is initial seald gas. Xe and Kr are fission-product gases, of which the quantities depend on the fuel burn-up. In program GAPCON series (GAPCON and GAPCON-THERMAL-1 and -2) and FREG-3, these quantities are given as a function of the irradiation time, power rating and neutron flux in estimation of the thermal conductivity of the mixed gas. The methods of calculating the quantities of Xe and Kr in the programs have been examined. Input of the neutron flux which influences F.P. gas production rates is better than the determination from the fuel-rod power rating. (auth.)
International Nuclear Information System (INIS)
The effects of liquid sprayed density on the pressure drop and mass transfer coefficient were discussed in a hydrogen-water liquid phase catalytic bed of ?24 mm x 1000 mm, which was filled with the mixture of hydrophobic catalyst and packing. The pressure drop (?p) increases obviously with the liquid sprayed density (l) in higher gas velocity and slightly with l in lower gas velocity. When the gas velocity is lower, l and entrained liquid (?) have little effect on the mass transfer coefficient (Kya). While the gas velocity is higher, Kya increases with l, ? has effect on Kya. (authors)
Water mist effect on heat transfer coefficient in cooling of casting die
R.W?adysiak
2008-01-01
This project is showing investigation results of heat transfer process between cast iron die and environment during cooling of die in the temperature range 600÷100 C with compressed air, spray water and water mist streamed under pressure 0.35 0.45 MPa in air jet0.3 0.4 MPa .At the paper are shown results of cooling die’s flat wall using open cooling system. The temperature gradient was presented at die’s wallthickness and calculated thermal curve for cooling surface. The calculation results o...
Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes
Taler, Jan; Taler, Dawid; Kowal, Andrzej
2011-04-01
The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surfaces of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.
International Nuclear Information System (INIS)
A mathematical model is presented to study the Soret and Dufour effects on the convective heat and mass transfer in stagnation-point flow of viscous incompressible fluid towards a shrinking surface. Suitable similarity transformations are used to convert the governing partial differential equations into self-similarity ordinary differential equations that are then numerically solved by shooting method. Dual solutions for temperature and concentration are obtained in the presence of Soret and Dufour effects. Graphical representations of the heat and mass transfer coefficients, the dimensionless thermal and solute profiles for various values of Prandtl number, Lewis number, Soret number and Dufour number are demonstrated. With Soret number the mass transfer coefficient which is related to mass transfer rate increases for both solutions and the heat transfer coefficient (related to heat transfer rate) for both solutions becomes larger with Dufour number. The Prandtl number causes reduction in heat and the mass transfer coefficients and similarly with the Lewis number mass transfer coefficient decreases. Also, double crossing over is found in dual dimensionless temperature profiles for increasing Soret number and in dual dimensionless concentration profiles for the increase in Dufour number. Due to the larger values of Dufour number the thermal boundary layer increases and for Prandtl number increment it decreases; whereas, the solute boundary layer thickness reduces with increasing values of Prandtl number and Lewis number. (paper)
Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere
International Nuclear Information System (INIS)
The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface. 24 references
EMILA DJORDJEVIC; STEPHAN KABELAC; SLOBODAN SERBANOVIC
2007-01-01
In this study the transfer coefficient of evaporation heat of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger was experimentally investigated. The results are presented as the dependancy of the mean heat transfer coefficient for the whole heat exchanger on the mean vapor quality. The influences of mass flux, heat flux and flow configuration on the heat transfer coefficient were also taken into account and a comparison with previously published experimenta...
Estimation of the friction coefficient between wheel and rail surface using traction motor behaviour
International Nuclear Information System (INIS)
The friction coefficient between a railway wheel and rail surface is a crucial factor in maintaining high acceleration and braking performance of railway vehicles thus monitoring this friction coefficient is important. Restricted by the difficulty in directly measuring the friction coefficient, the creep force or creepage, indirect methods using state observers are used more frequently. This paper presents an approach using a Kalman filter to estimate the creep force and creepage between the wheel and rail and then to identify the friction coefficient using the estimated creep force-creepage relationship. A mathematic model including an AC motor, wheel and roller is built to simulate the driving system. The parameters are based on a test rig at Manchester Metropolitan University. The Kalman filter is designed to estimate the friction coefficient based on the measurements of the simulation model. Series of residuals are calculated through the comparison between the estimated creep force and theoretical values of different friction coefficient. Root mean square values of the residuals are used in the friction coefficient identification.
Li, Chengwei; Zhan, Liwei
2015-08-01
To estimate the coefficient of friction between tire and runway surface during airplane touchdowns, we designed an experimental rig to simulate such events and to record the impact and friction forces being executed. Because of noise in the measured signals, we developed a filtering method that is based on the ensemble empirical mode decomposition and the bandwidth of probability density function of each intrinsic mode function to extract friction and impact force signals. We can quantify the coefficient of friction by calculating the maximum values of the filtered force signals. Signal measurements are recorded for different drop heights and tire rotational speeds, and the corresponding coefficient of friction is calculated. The result shows that the values of the coefficient of friction change only slightly. The random noise and experimental artifact are the major reason of the change.
Hamasaiid, A.; Dour, G.; Dargusch, M. S.; Loulou, T.; Davidson, C.; Savage, G.
2008-04-01
The present article deals with the application of a new measurement method to determine the heat-transfer coefficient (HTC) and the heat flux density at the casting-die interface during high-pressure die casting (HPDC) and solidification of the magnesium AZ91D alloy. The main measurements during the trial included velocity and the position of the piston that delivers the metal into the die, the pressure in the die cavity and at the tip of the piston, the alloy surface temperature, and the die temperature at different depths from the surface of the die. The temperature data were analyzed using an inverse method to determine the HTC at the casting-die interface during solidification. This article examines in detail the influence of the piston velocity and in-cavity pressure on heat transfer at the casting-die interface during casting and solidification of the magnesium AZ91D alloy.
Directory of Open Access Journals (Sweden)
Pinheiro Cleber
2008-07-01
Full Text Available Abstract Background One of the current shortcomings of radiofrequency (RF tumor ablation is its limited performance in regions close to large blood vessels, resulting in high recurrence rates at these locations. Computer models have been used to determine tissue temperatures during tumor ablation procedures. To simulate large vessels, either constant wall temperature or constant convective heat transfer coefficient (h have been assumed at the vessel surface to simulate convection. However, the actual distribution of the temperature on the vessel wall is non-uniform and time-varying, and this feature makes the convective coefficient variable. Methods This paper presents a realistic time-varying model in which h is a function of the temperature distribution at the vessel wall. The finite-element method (FEM was employed in order to model RF hepatic ablation. Two geometrical configurations were investigated. The RF electrode was placed at distances of 1 and 5 mm from a large vessel (10 mm diameter. Results When the ablation procedure takes longer than 1–2 min, the attained coagulation zone obtained with both time-varying h and constant h does not differ significantly. However, for short duration ablation (5–10 s and when the electrode is 1 mm away from the vessel, the use of constant h can lead to errors as high as 20% in the estimation of the coagulation zone. Conclusion For tumor ablation procedures typically lasting at least 5 min, this study shows that modeling the heat sink effect of large vessels by applying constant h as a boundary condition will yield precise results while reducing computational complexity. However, for other thermal therapies with shorter treatment using a time-varying h may be necessary.
Mass Transfer Coefficient During Cathodic Protectionof Low Carbon Steel in Seawater
Directory of Open Access Journals (Sweden)
Ameel Mohammed Rahman
2009-01-01
Full Text Available The aim of this research is to calculate mass transfer coefficient, kd, during cathodic protection of low carbon steel in neutral seawater (3.5% W/V NaCl in distilled water with pH = 7. Two types of cathodic protection were used:First: Sacrificial anode cathodic protection (SACP were a pipeline of steel carrying seawater using zinc as a sacrificial anode and with variable temperatures ranged (0 ? 45oC and volumetric flow rate ranged (5 ? 900 lit/hr. It was found that the kd increases with increasing temperature and volumetric flow rate of seawater, where kd ranged (0.24×10-6 ? 41.6×10-6 m/s.Second: Impressed current cathodic protection (ICCP technique adopting a rotating vertical steel cylinder in seawater with variable temperatures ranged (0 ? 45oC and rotating velocity ranged (0 ? 400 rpm. It was found that the kd increases with increasing temperature and rotating velocity, where kd ranged (7.25×10-6 ? 36.82×10-6 m/s.
Experimentally Determined Overall Heat Transfer Coefficients for Spacesuit Liquid Cooled Garments
Bue, Grant; Rhodes, Richard; Anchondo, Ian; Westheimer, David; Campbell, Colin; Vogel, Matt; Vonaue, Walt; Conger, Bruce; Stein, James
2015-01-01
A Human-In-The-Loop (HITL) Portable Life Support System 2.0 (PLSS 2.0) test has been conducted at NASA Johnson Space Center in the PLSS Development Laboratory from October 27, 2014 to December 19, 2014. These closed-loop tests of the PLSS 2.0 system integrated with human subjects in the Mark III Suit at 3.7 psi to 4.3 psi above ambient pressure performing treadmill exercise at various metabolic rates from standing rest to 3000 BTU/hr (880 W). The bulk of the PLSS 2.0 was at ambient pressure but effluent water vapor from the Spacesuit Water Membrane Evaporator (SWME) and the Auxiliary Membrane Evaporator (Mini-ME), and effluent carbon dioxide from the Rapid Cycle Amine (RCA) were ported to vacuum to test performance of these components in flight-like conditions. One of the objectives of this test was to determine the overall heat transfer coefficient (UA) of the Liquid Cooling Garment (LCG). The UA, an important factor for modeling the heat rejection of an LCG, was determined in a variety of conditions by varying inlet water temperature, flow rate, and metabolic rate. Three LCG configurations were tested: the Extravehicular Mobility Unit (EMU) LCG, the Oceaneering Space Systems (OSS) LCG, and the OSS auxiliary LCG. Other factors influencing accurate UA determination, such as overall heat balance, LCG fit, and the skin temperature measurement, will also be discussed.
An Experimental Investigation of Heat Transfer Coefficients for Spiral Plate Heat Exchanger
Directory of Open Access Journals (Sweden)
Kaliannan Saravanan
2009-02-01
Full Text Available Spiral plate heat exchangers play a vital role in cooling high density and high viscous fluids. This paper presents an experimental investigation of convective heat transfer co-efficient for electrolytes using spiral plate heat exchanger. The test section consists of a Plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot fluid is varying from 0.4 kg sec-1 to 0.8 kg sec-1 and the mass flow rate of cold fluid varies from 0.3 kg sec-1 to 0.8 kg sec-1. Experiments have been conducted by varying the mass flow rate, temperature and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the nusselt number that can be used for practical applications is proposed.
Effect of Lubricant Viscosity and Surface Roughness on Coefficient of Friction in Rolling Contact
Directory of Open Access Journals (Sweden)
S.G. Ghalme
2013-12-01
Full Text Available The main objective of this paper is to investigate the effect of surface roughness and lubricant viscosity on coefficient of friction in silicon nitride- steel rolling contact. Two samples of silicon nitride with two different values of surface roughness were tested against steel counter face. The test was performed on four ball tester in presence of lubricant with two different values of viscosity. Taguchi technique a methodology in design of experiment implemented to plan the experimentation and same is utilized to evaluate the interacting effect of surface roughness and lubricant viscosity. Analysis of experimental results presents a strong interaction between surface roughness and lubricant viscosity on coefficient of friction in rolling contact.
International Nuclear Information System (INIS)
Electron-impact transfer rate coefficients, from Ar(1s5) to Ar(1s4) and from Ar(1s3) to Ar(1s2), are obtained in the afterglow of a capacitive discharge. The discharge is generated by a pulsed 13.56?MHz rf power source with 20?mTorr argon. The densities of the four argon 1s states are measured by diode laser absorption, the electron temperature (Te) is measured by a Langmuir probe and the electron density is measured by both the probe and a microwave interferometer. Using the measured parameters and a kinetic model for Ar metastable states in the afterglow, the electron-impact transfer rate coefficients are determined in a Te range of 0.25?1.0?eV. It is found that the obtained rate coefficients agree well with those from the R-matrix calculation. (paper)
International Nuclear Information System (INIS)
Highlights: ? Partition coefficients octanol/buffer of new drug-like spiro-derivatives were determined. ? Thermodynamic functions of transfer were calculated. ? The correlations partition coefficients and molecular descriptors are discussed. -- Abstract: Temperature dependences of partition coefficient for 11 drug-like spiro-derivatives of 1,3-thiazine in the system aqueous phosphate buffer/organic phase (hexane, octanol) have been determined over the temperature range (293.15 to 315.15) K by the isothermal saturation method. The effects of aliphatic chain substituent structure and introduction of oxygen, chlorine, bromine and fluorine atoms on the partitioning processes of the substances studied were examined. It has been established that among the substances investigated halogen derivatives possess the lowest partition coefficients in buffer/hexane system and the highest ones in buffer/octanol system. Regularities between the partition coefficients and the descriptors reflecting the capability of the solutes to undergo specific and nonspecific interactions with solvent molecules were revealed. The thermodynamic functions describing the partitioning process were calculated. It was found that differences in the partition coefficients depend on the enthalpies of transfer
Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...
International Nuclear Information System (INIS)
Absolute measurement of activity implies a determination of effective depths and effective attenuation coefficients. In order to define restoration filters, it is necessary to measure the transfer function, i.e. position a line source at an effective depth for the specific measurement situation. A phantom was designed which can simulate an organ with a certain thickness at a certain depth. The phantom was used to measure transfer functions and a comparison was made with transfer functions from a line source to determine effective depths. Effective attenuation coefficients were calculated for 99mTc, 111In and 201Tl for different organ thicknesses and depths of simulated organs. The effective attenuation coefficient for 99mTc was found to be 0.124±0.006 cm-1, in good agreement with previously published values. For 111In, the attenuation coefficient decreased with the depth of an organ due to the use of two energy windows in the measurements and a corresponding change in mean photon energy by depth. For 201Tl, the attenuation coefficient decreased with increasing organ thickness due to the increasing fraction of scattered radiation in the 40% energy window used. Using attenuation coefficients of 0.124, 0.184 and 0.11 cm-1 for 99mTc, 201Tl and 111In respectively, the derived equations can be used to calculate the position of a conventional line source e position of a conventional line source for measurements of transfer functions for a specific organ with a certain thickness at a certain depth for definition of different types of restoration filter. (author)
International Nuclear Information System (INIS)
The purpose has been to describe an approach suggested for constructing generalized closure relationships for local and subchannel wall friction, heat and mass transfer coefficients, with not only axial and transversal parameters taken into account, but azimuthal substance transfer effects as well. These constitutive relations that are primary for description of one- and two-phase one-dimensional flow models can be derived from the initial 3-D drift flux formulation. The approach is based on the Reynolds flux, boundary layer and generalized coefficient of substance transfer. One more task has been to illustrate the validity of the 'conformity principle' for the limiting cases. The method proposed is based on the similarity theory, boundary layer model, and a phenomenological description of the regularities of the substance transfer (momentum, heat, and mass), as well as on an adequate simulation of the forms of flow structure by a generalized approach to build (an integrated in form and semi-empirical in maintenance structure) analytical relationships for wall friction, heat and mass transfer coefficients. (author)
Nikkhou, Fatemeh; Keshavarz, Peyman; Ayatollahi, Shahab; Jahromi, Iman Raoofi; Zolghadr, Ali
2015-04-01
CO2 gas injection is known as one of the most popular enhanced oil recovery techniques for light and medium oil reservoirs, therefore providing an acceptable mass transfer mechanism for CO2-oil systems seems necessary. In this study, interfacial mass transfer coefficient has been evaluated for CO2-normal heptane and CO2-normal hexadecane systems using equilibrium and dynamic interfacial tension data, which have been measured using the pendant drop method. Interface mass transfer coefficient has been calculated as a function of temperature and pressure in the range of 313-393 K and 1.7-8.6 MPa, respectively. The results showed that the interfacial resistance is a parameter that can control the mass transfer process for some CO2-normal alkane systems, and cannot be neglected. Additionally, it was found that interface mass transfer coefficient increased with pressure. However, the variation of this parameter with temperature did not show a clear trend and it was strongly dependent on the variation of diffusivity and solubility of CO2 in the liquid phase.
Zhang, Liqiang; Tan, Wenfang; Hu, Hao
2015-07-01
For modeling solidification process of casting accurately, a reliable heat transfer boundary condition data is required. In this paper, an inverse conduction model was established to determine the heat flux and heat transfer coefficient at the metal-sand mold interface for cylindrical casting in the lost foam process. The numerically calculated temperature was compared with analytic solution and simulation solution obtained by commercial software ProCAST to investigate the accuracy of heat conduction model. The instantaneous cast and sand mold temperatures were measured experimentally and these values were used to determine the interfacial heat transfer coefficient (IHTC). The IHTC values during lost foam casting were shown to vary from 20 to 800 W m-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed in this study.
International Nuclear Information System (INIS)
For a steam generator with straight double-walled heat transfer tubes that will be used in sodium cooled faster breeder reactor, clarification of flow instability in heat transfer tubes is one of the most important research themes. As the first step of the research, thermal hydraulics experiments with water were performed under high pressure condition in JAEA with using a circular tube. Pressure drop, heat transfer coefficients and void fraction data were derived. This paper summarizes the heat transfer characteristics under 15-18 MPa. Saturated boiling heat transfer was discussed with four most famous general heat transfer correlations (Chen, Shah, Steiner-Taborek and Gungor-Winterton) being verified. Under present high pressure condition, it was found that the Shah correlation gave good agreement with data at low mass flow rate and the Chen correlation gave good agreement at high mass flow rate condition. For the nominate flow rate of w=110 g/s, both Chen and Shah correlations can be used. As a result, under present high pressure condition, we recommend that the smaller one of the Chen and Shah correlations be used for the calculation of heat transfer coefficient. (author)
Energy Technology Data Exchange (ETDEWEB)
Yuen, C.H.N.; Martinez-Botas, R.F. [Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, London (United Kingdom)
2005-11-01
Measurements of heat transfer coefficient (h) are presented for rows of round holes at streamwise angles of 30{sup o}, 60{sup o} and 90{sup o} with a short but engine representative hole length (L/D=4). The study began with a single row of holes with pitch-to-diameter ratios of 3 and 6, followed by two inline and staggered rows for each hole spacing and streamwise inclination, which amount to 105 different test cases in addition to the 21 test cases presented on the single hole [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single round hole at various angles in a crossflow: Part I. Effectiveness, Int. J. Heat Mass Transfer, in press; C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single round hole at various angles in a crossflow: Part II. Heat transfer coefficients, Int. J. Heat Mass Transfer, in press]. The present investigation is a continuation of the previous work [Yuen and Martinez-Botas, Parts I and II, in press] with the same test facility, operating conditions (freestream Reynolds number, Re{sub D} of 8563, and blowing ratio, 0.33=
Chiu, Rong-Shi Paul (Glenmont, NY); Hasz, Wayne Charles (Pownal, VT); Johnson, Robert Alan (Simpsonville, SC); Lee, Ching-Pang (Cincinnati, OH); Abuaf, Nesim (Lincoln City, OR)
2002-01-01
An annular turbine shroud separates a hot gas path from a cooling plenum containing a cooling medium. Bumps are cast in the surface on the cooling side of the shroud. A surface coating overlies the cooling side surface of the shroud, including the bumps, and contains cooling enhancement material. The surface area ratio of the cooling side of the shroud with the bumps and coating is in excess of a surface area ratio of the cooling side surface with bumps without the coating to afford increased heat transfer across the element relative to the heat transfer across the element without the coating.
Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C
2015-09-01
In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies. PMID:25996756
Energy Technology Data Exchange (ETDEWEB)
Yan, W.M.; Mei, S.C. [Department of Mechatronic Engineering, Huafan University, Shih Ting, Taipei 22305, Taiwan (China)
2006-01-15
The objective of the present study is to examine the detailed heat transfer coefficient distributions over a ribbed-surface under impingement of elliptic jet arrays using a liquid crystal thermograph technique. Both continuous and broken V-shaped-rib configurations with different exit flow orientations were considered. To examine the angled rib effects, three angled ribs were discussed under jet-to-plate spacing Z=3 for different Reynolds numbers. Measured results show that the local heat transfer rates over the ribbed-surface are characterized by obvious periodic-type variation of Nusselt number distributions. The downstream peaks are diminished for increasing crossflow effect. Compared to the results without ribs, the heat transfer over the ribbed-surface may be enhanced or retarded. Whereas, among the test angled-rib arrangements, the best heat transfer performance is obtained with a surface with 45{sup o} V-shape ribs. In addition, the surface with continuous ribs provides a better impingement heat transfer than that with broken ribs. (author)
Experimental study on augmentation of nucleate boiling heat transfer on nano porous surfaces
International Nuclear Information System (INIS)
Nucleate boiling broadly occurs in thermal hydraulic and safety systems of nuclear power plant (NPP). Heat transfer performance of nucleate boiling is closely related to efficiency and safety of NPPs. Hence, there have been numerous researches to effectively enhance nucleate boiling heat transfer performance. A number of recent studies have reported significant enhancements in nucleate boiling heat transfer coefficient (NBHTC) and critical heat flux (CHF) by fabricating nano/microscale structures on a boiling surface. Wei et al. showed that both NBHTC and CHF can be significantly enhanced with micro pin finned structures. They explained enhancement of NBHTC and CHF that occurred by increase in effective heat transfer area due to micro pin finned structures. Ahn et al. reported 100% enhancement in CHF on a boiling surface with nano/micro hybrid structures. They analyzed CHF enhancement that was caused by improvement of surface wettability on Nano/micro hybrid structures. In this study, an ordered nano porous surface was prepared using anodized aluminum oxide (AAO) technique and nucleate boiling heat transfer performance was examined in a pool with FC 72. Furthermore, the pool boiling result on the nano porous surface was interpreted based on heterogeneous bubble nucleation theory from a cavity
Experimental study on augmentation of nucleate boiling heat transfer on nano porous surfaces
Energy Technology Data Exchange (ETDEWEB)
Park, Young Jae; Kim, Hyung Dae [Kyung Hee Univ., Seoul (Korea, Republic of)
2012-10-15
Nucleate boiling broadly occurs in thermal hydraulic and safety systems of nuclear power plant (NPP). Heat transfer performance of nucleate boiling is closely related to efficiency and safety of NPPs. Hence, there have been numerous researches to effectively enhance nucleate boiling heat transfer performance. A number of recent studies have reported significant enhancements in nucleate boiling heat transfer coefficient (NBHTC) and critical heat flux (CHF) by fabricating nano/microscale structures on a boiling surface. Wei et al. showed that both NBHTC and CHF can be significantly enhanced with micro pin finned structures. They explained enhancement of NBHTC and CHF that occurred by increase in effective heat transfer area due to micro pin finned structures. Ahn et al. reported 100% enhancement in CHF on a boiling surface with nano/micro hybrid structures. They analyzed CHF enhancement that was caused by improvement of surface wettability on Nano/micro hybrid structures. In this study, an ordered nano porous surface was prepared using anodized aluminum oxide (AAO) technique and nucleate boiling heat transfer performance was examined in a pool with FC 72. Furthermore, the pool boiling result on the nano porous surface was interpreted based on heterogeneous bubble nucleation theory from a cavity.
ASED-MO study of activation energies and diffusion coefficients of Cu on Pt surfaces
International Nuclear Information System (INIS)
The chemisorption and surface diffusion of Cu on Pt(111), (100), (110) are studied by using the ASED-MO method. The activation energies and the diffusion coefficients at 300 K of Cu atoms on these three Pt surfaces are 0.167 eV, 0.162 eV, 0.667 eV and 3.04 x 10 -10 m2/s, 3.69 x 10-10 m2/s, 2.42 x 10-18 m2/s respectively. It is shown that, the activation energies are rather small and Cu atoms have a high mobility on Pt(111) and (100) surfaces; but on Pt(110), the activation energy is comparatively higher and the diffusion coefficient is small
MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS
International Nuclear Information System (INIS)
Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels
MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS
Energy Technology Data Exchange (ETDEWEB)
Leishear, R.
2009-09-09
Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.
International Nuclear Information System (INIS)
Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10?1 and 1.8 × 10?1 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9 × 10?2 d L?1 and 4.6 × 10?2 d L?1, respectively, for adopted Cows 1 and 2; 1.7 × 10?2 d L?1 for the cows of local farmers, and 4.0 × 10?3 d L?1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 ?Sv y?1 and 0.04 ?Sv y?1,while that to an adult were 0.39 ?Sv y?1 and 0.05 ?Sv y?1, respectively. -- Highlights: • This is a detailed study on Fv and Fm for 137Cs and stable Cs around the Kaiga nuclear power plant, India. • The geometric mean values of Fv were found to be 1.1 × 10?1 and 1.8 × 10?1 for 137Cs and stable Cs, respectively. • The Fm value for 137Cs for the local breed cows was estimated to be 2.4 × 10?2 d L?1. • The Fm value for dairy farm cows (4.0 × 10?3 d L?1) was an order of magnitude lower than those for local breed cows. • The reasons for the higher Fm values for 137Cs for the local breed cows are identified
Grass to cow milk transfer coefficient (Fm) of iodine for equilibrium and emergency situations
International Nuclear Information System (INIS)
Radioiodine (131I) is one of the radionuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. If released to the environment during an accident, 131I may enter the grass?cow?cow milk pathway, leading to increased thyroid dose to those consuming milk, especially infants and children. The estimation of site-specific grass to milk transfer coefficient (Fm) for iodine is essential for an accurate assessment of the radiological hazard to the population in the region surrounding a nuclear power plant. In this study, a method based on the chemical separation of iodine present in grass and cow milk, and subsequent neutron activation analysis (NAA) has been optimized for the determination of stable iodine concentration in grass and cow milk. The method involves preconcentration of iodine from the sample matrix, and determination of iodine by NAA. The detection limit of stable iodine in milk was found to be 1 ng/mL. For the validation of the result, iodine concentration in NIST reference materials was determined simultaneously. The present study has yielded a Fm value of 5.6 x 10-3 d/L for dairy farm cows and 6.3 x 10-3 d/L for local breed cows under equilibrium conditions. These results are similar to the values given in International Atomic Energy Agency report (TRS-472). To simulate a rapid deposition of iodine on grass and for the estimation of Fm value for an emergency situation, grass grown in the experimental field was sprayed with stable potassium iodide solution and fed to the adopted cows, and the milk samples were collected regularly and analyzed. The Fm value for the simulated accidental situation was found to be 3.9 x 10-3 d/L. (author)
Data Qualification Report For DTN: MO0012RIB00065.002, Parameter Values For Transfer Coefficients
International Nuclear Information System (INIS)
A data-qualification evaluation was conducted on Reference Information Base (RIB) data set MOO0 12RIB00065.002, ''Parameter Values for Transfer Coefficients''. The corroborating data method was used to evaluate the data. This method was selected because it closely matches the literature-review method followed to select parameter values. Five criteria were considered when the corroborating method was used: adequacy of the corroborative literature, sufficiency of value-selection criteria, implementation of the selection criteria, documentation of the process, and whether the analysis was conducted in accordance with applicable quality assurance (QA) procedures. Three criteria were used when a literature review was not conducted: appropriate logic used to select parameters, documentation of the process, and whether the analysis was conducted in accordance with applicable QA procedures. The RIB data item, the associated Analysis and Model Report (AMR), the corroborative literature, and the results of an audit revision O/ICN--0 of the AMR were examined. All calculations and the selection process for all values were repeated and confirmed. The qualification team concluded: (1) A sufficient quantity of corroborative literature was reviewed and no additional literature was identified that should have been considered. (2) The selection criteria were sufficient and resulted in valid parameter values. (3) The process was well defined, adequately documented in the AMR, and correctly followed. (4) The analysis was developed in accordance with applicable QA procedures. No negative findings were documented that resulted in questions about the quality of the data. The qualification team therefore recommends that the qualification status of RIB data set MO0012RIB00065.002 be changed to qualified
Energy Technology Data Exchange (ETDEWEB)
Hirahaya, Kunio; Nagano, Toshiyuki; Fujita, Yasunobu
1988-07-25
It has been known that during the direct contact evaporation process, when the flow phase forms a vapor column, the maximum heat transfer performance is shown. In order to explain the above heat transfer mechanism, the flow was modeled and with regard to R113 liquid which was dropped onto a flowing water surface, its behavior and evaporation characteristics were investigated. The contacting form between R113 liquid and the water surface took any one of forms of spheroidal drop, lens and continuous thin film. As the angle of incident and the flow rate of R113 liquid against the water surface were decreased, and as the temperature difference between the saturation temperature of R113 liquid and the pouring temperature of R113 liquid as well as the water temperature was increased, the probability of forming the respective form above in the order of continuous thin film, lens and spheroidal drop was increased. The heat transfer coefficient was decreased by several times in the above order of forms and when the temperature difference was increased, the thickness of the liquid film was increased and the heat transfer coefficient was decreased. Because of the above synergetic effect, the heat transfer coefficient in the form of vapor column was affected to have a big negative gradient against the temperature difference. (12 figs, 1 tab, 11 refs)
DEFF Research Database (Denmark)
Matteoni, G.; Georgakis, C.T.
2012-01-01
Theoretical and experimental investigations to date have assumed that bridge cables can be modeled as ideal circular cylinders and the associated aerodynamic coefficients are invariant with the wind angle-of-attack. On the other hand, bridge cables are normally characterized by local alterations of their inherent surface roughness and shape, which might present a significant disturbance for the surrounding wind flow. The present study focuses on the experimental determination, based on static wind tunnel tests, of the aerodynamic coefficients of full-scale bridge cable section models both perpendicular and inclined to the flow, for varying wind angles-of-attack. The wind tunnel test results demonstrate that the aerodynamic coefficients of bridge cables can be significantly affected by the wind angle-of-attack.
International Nuclear Information System (INIS)
A physical model for analyzing the radiative and convective heat transfer in a fog cooled, naturally ventilated greenhouse was developed for estimating the overall heat transmission coefficient based on the conduction, convection and thermal radiation heat transfer coefficients and for predicting the soil heat flux. The contribution of the water vapor of the inside air to the emission and absorption of thermal radiation was determined. Measurements of the outside and inside greenhouse environments to be used in the analysis were conducted around solar noon (12:19-13:00) on a hot sunny day to provide the maximum solar radiation transmission into the greenhouse. The net solar radiation flux measured at the greenhouse floor showed a reasonable agreement with the predicted value. The net fluxes were estimated around noon. The average net radiation (solar and thermal) at the soil surface was 220.0 W m-2, the average soil heat flux was 155.0 W m-2 and the average contribution of the water vapor of the inside air to the thermal radiation was 22.0 W m-2. The average overall heat transmission coefficient was 4.0 W m-2 C-1 and was in the range between 3.0 W m-2 C-1 and 6.0 W m-2 C-1 under the different hot summer conditions between the inside and outside of the naturally ventilated, fog cooled greenhouse
Heat transfer characteristics of large superconductors with different surface conditions
International Nuclear Information System (INIS)
For the development of large current, high current density superconductors, steady-state boiling helium heat transfer characteristics of the model conductors having different cooling surfaces were measured. This reports describes example conditions, experimental conditions, measurement means and results. (author)
SAFARI 2000 Surface Atmospheric Radiative Transfer (SMART), Dry Season 2000
National Aeronautics and Space Administration — Surface-sensing Measurements for Radiative Transfer (SMART) and Chemical, Optical, and Microphysical Measurements of In-situ Troposphere (COMMIT) consist of a suite...
Filtering Non-Linear Transfer Functions on Surfaces
Heitz, Eric; Nowrouzezahrai, Derek; Poulin, Pierre; Neyret, Fabrice
2014-01-01
Applying non-linear transfer functions and look-up tables to procedural functions (such as noise), surface attributes, or even surface geometry are common strategies used to enhance visual detail. Their simplicity and ability to mimic a wide range of realistic appearances have led to their adoption in many rendering problems. As with any textured or geometric detail, proper filtering is needed to reduce aliasing when viewed across a range of distances, but accurate and efficient transfer func...
Surface heat transfer due to sliding bubble motion
Donnelly, Brian; O'Donovan, Tadhg S.; Murray, Darina B.
2009-01-01
The presence of a rising bubble in a fluid can greatly enhance heat transfer from adjacent heated surfaces such as in shell and tube heat exchangers and chemical reactors. One specific case of this is when a bubble impacts and slides along the surface. The result is heat transfer enhancement by two main mechanisms: first, the bubble itself acting as a bluff body, and second, the wake generated behind the bubble leads to increasing mixing. The current research is concerned with mea...
Improvement of dropwise condensation heat transfer using hydrophobic nano porous surfaces
International Nuclear Information System (INIS)
Recently interest of passive system in thermal hydraulic safety system of nuclear power plants has been increased. Passive residual heat removal system (PRHRS) is applied to SMART and APR+ for providing the sufficient cooling capacity against accident conditions. PRHRS is a device for removing the decay heat that cools steam through condensation heat transfer in emergency tank. Condensation is one of most important heat transfer methods in almost industry including the PRHRS. Condensation is classified, according to shape of condensate, into drop-wise condensation and film wise condensation. Drop-wise condensation (DWC) exhibits a significantly higher heat transfer coefficient than film wise condensation (FWC). Whether DWC or FWC occurs in a heat transfer surface is strongly affected by wettability of a surface. It is known that DWC is appears on low wettability surfaces while FWC is appears on high wettability one. In this study, nano-porous hydrophobic surfaces were prepared and tested for the improvement of dropwise condensation heat transfer performance
Energy Technology Data Exchange (ETDEWEB)
Rocha, Alan Carlos Bueno da
1997-07-01
A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the form of dimensionless parameters as Nusselt, Rayleigh, Grashof and Prandtl numbers, and dimensional parameters of the convection. The results showed that the highest heat transfer value occurred when both a specific position and a specific channel opening were used. The experiments pointed out that the radiation contribution must be considered in heat transfer calculations. The conclusions showed that different channel openings can improve the heat transfer coefficient in this heat transfer exchanger. (author)
Transfer coefficients of 137Cs via the forage-cow-milk pathway in Aomori Prefecture of Japan
International Nuclear Information System (INIS)
The transfer of radiocesium to foodstuff of cattle is very serious, because it contributes significantly to internal exposure resulting from the intake of 137Cs through the feed-cow-milk pathway. The transfer coefficient from feed to milk (Fm) is widely used to predict the dose to man from the radioactivity released to the biosphere. A commercial fuel reprocessing plant is under construction in Rokkasho-mura/Aomori Prefecture, the northeastern district of Japan. To figure out Fm under conventional farming conditions, therefore, transfer of 137Cs deposited in the environment in cooperation with two daily farms in this region. Transfer factors for 137Cs from feed to cow's milk have been obtained from data acquired from biweekly routine monitoring program under the two dissimilar farming conditions. The one dairy farm condition is mainly composed of high hay ration and the other is high concentrate ration. As a result of the experiments, 137Cs activity of milk correlated significantly with that of feed. The mean transfer coefficients of 137Cs to milk were calculated to be 0.0037 and 0.0063 (d/l), respectively. (author)
The coefficient of friction between boron carbide (B4C) surfaces in air and ultrahigh vacuum (UHV)
International Nuclear Information System (INIS)
Friction measurements between two contacting B4C surfaces in air and UHV at room temperature using 0.10-0.13N loads are reported. A pin (radius = 0.005m) on flat device allowing for interchange in UHV is used. The tribological surfaces can be examined using scanning Auger and XPS in the same UHV system. The coefficient of friction for air exposed surfaces is found to vary between air (0.20-0.25) and UHV (1.2-1.8). Stick-slip behavior, indicating strong adhesion, is observed in UHV while only a smooth friction value is measured in air. Air pressures 100Pa are necessary to reduce the friction from the high value in UHV. The friction between the clean surfaces in UHV initially is 0.8-1.3, but following mechanical conditioning at a higher velocity the friction drops to 0.17-0.25. In situ mechanical conditioning is necessary to obtain reproducible friction values for the clean surface. Exposing the clean surfaces to oxygen (10-3Pa) while conditioning results in an increase in friction (1.0-1.2). Auger line scans through the scar made using the clean surfaces show enhanced B and reduced C. Similar Auger scans for oxygen exposed surfaces indicate that tearing of the oxide layer may be the reason for the high friction. The friction for a clean pin and an in situ nitrogen-implanted flat (10keV, saturation dose) is 0.70-0.80. Film transfer to the pin is observed
Jeffers, N; Punch, J; Walsh, E.
2009-01-01
Contemporary electronic systems generate high component-level heat fluxes. Impingement cooling is an effective way to induce high heat transfer coefficients in order to meet thermal constraints. The objective of this paper was to experimentally investigate the heat transfer from five novel target surface structures to a normally-impinging, submerged and confined water jet. The five target structures were: a 90° vane; a 4x4 pin fin array; and three geometries which turn the flow away from, and...
Bozzoli, F.; Cattani, L.; Pagliarini, G.; Rainieri, S.
2015-03-01
This paper presents and assesses an inverse heat conduction problem (IHCP) solution procedure which was developed to determine the local convective heat transfer coefficient along the circumferential coordinate at the inner wall of a coiled pipe by applying the filtering technique approach to infrared temperature maps acquired on the outer tube's wall. The data-processing procedure filters out the unwanted noise from the raw temperature data to enable the direct calculation of its Laplacian which is embedded in the formulation of the inverse heat conduction problem. The presented technique is experimentally verified using data that were acquired in the laminar flow regime that is frequently found in coiled-tube heat-exchanger applications. The estimated convective heat transfer coefficient distributions are substantially consistent with the available numerical results in the scientific literature.
International Nuclear Information System (INIS)
The computation and analysis of the heat transfer coefficient correction factor the shell and tube type of the Kartini reactor's heat exchanger (HE) has been carried out. The computation of the correction factor was done by measuring of the actual dimension of HE. As known that the shell and tube type of the Kartini reactor's has been opera-ted for more than 15 years. Due to the scraping and rusting occur at the buffle, the total heat transfer coefficient correction factor Ft was decrease. At the later computation, it is found that it's value is 0,4669 or differ of 0,1331 compared to the prediction standard value. So far, if the rusting and scraping of the secondary water coolant to the buffle is linear to the earlier HE's operation time, it is predicted that the function of the buffle will crisis approximately in the year of 2002/2003 or 7,5 years again
International Nuclear Information System (INIS)
It is proposed the model of potential field near solid surface, which allows to get the analytical solution of Schroedinger equations and calculate the coefficient of beams reflection by solid surface. It is obtained the oscillations of the reflection coefficient when changing the field characteristics
Miranda, Marco
2014-01-01
This Thesis presents a dissertation about an experimental method, and a subsequent numerical data post processing, having as goal the heat transfer coefficient and adiabatic effectiveness measurement in gas turbine film cooling problems. The present work has been developed starting from an aerodynamic characterization of a linear nozzle vane cascade, cooled at the trailing edge by a cutback geometry, mounted in a suction-type wind tunnel at University of Bergamo turbomachinery laboratory. ...
Zhang, Zhiqiang; Gao, Peng; Liu, Chaoyang; Li, Xiangji
2015-09-01
An optimization-based numerical procedure was developed to determine the pressure-dependent heat transfer coefficient (HTC) between the blank and tools during the hot stamping of boron steel. During the quenching period, HTC increased with the contact pressure between blank and lower tool. There is no obvious linear relationship between them. The maximum value of 1500 W/m2 K was achieved at contact pressure 18 MPa.
Sustained frictional instabilities on nanodomed surfaces: Stick-slip amplitude coefficient
DEFF Research Database (Denmark)
Quignon, Benoit; Pilkington, Georgia A.
2013-01-01
Understanding the frictional properties of nanostructured surfaces is important because of their increasing application in modern miniaturized devices. In this work, lateral force microscopy was used to study the frictional properties between an AFM nanotip and surfaces bearing well-defined nanodomes comprising densely packed prolate spheroids, of diameters ranging from tens to hundreds of nanometers. Our results show that the average lateral force varied linearly with applied load, as described by Amontons' first law of friction, although no direct correlation between the sample topographic properties and their measured friction coefficients was identified. Furthermore, all the nanodomed textures exhibited pronounced oscillations in the shear traces, similar to the classic stick-slip behavior, under all the shear velocities and load regimes studied. That is, the nanotextured topography led to sustained frictional instabilities, effectively with no contact frictional sliding. The amplitude of the stick-slip oscillations, ?f, was found to correlate with the topographic properties of the surfaces and scale linearly with the applied load. In line with the friction coefficient, we define the slope of this linear plot as the stick-slip amplitude coefficient (SSAC). We suggest that such stick-slip behaviors are characteristics of surfaces with nanotextures and that such local frictional instabilities have important implications to surface damage and wear. We thus propose that the shear characteristics of the nanodomed surfaces cannot be fully described by the framework of Amontons' laws of friction and that additional parameters (e.g., ?f and SSAC) are required, when their friction, lubrication, and wear properties are important considerations in related nanodevices. © 2013 American Chemical Society.
Sustained frictional instabilities on nanodomed surfaces: stick-slip amplitude coefficient.
Quignon, Benoit; Pilkington, Georgia A; Thormann, Esben; Claesson, Per M; Ashfold, Michael N R; Mattia, Davide; Leese, Hannah; Davis, Sean A; Briscoe, Wuge H
2013-12-23
Understanding the frictional properties of nanostructured surfaces is important because of their increasing application in modern miniaturized devices. In this work, lateral force microscopy was used to study the frictional properties between an AFM nanotip and surfaces bearing well-defined nanodomes comprising densely packed prolate spheroids, of diameters ranging from tens to hundreds of nanometers. Our results show that the average lateral force varied linearly with applied load, as described by Amontons' first law of friction, although no direct correlation between the sample topographic properties and their measured friction coefficients was identified. Furthermore, all the nanodomed textures exhibited pronounced oscillations in the shear traces, similar to the classic stick-slip behavior, under all the shear velocities and load regimes studied. That is, the nanotextured topography led to sustained frictional instabilities, effectively with no contact frictional sliding. The amplitude of the stick-slip oscillations, ?f, was found to correlate with the topographic properties of the surfaces and scale linearly with the applied load. In line with the friction coefficient, we define the slope of this linear plot as the stick-slip amplitude coefficient (SSAC). We suggest that such stick-slip behaviors are characteristics of surfaces with nanotextures and that such local frictional instabilities have important implications to surface damage and wear. We thus propose that the shear characteristics of the nanodomed surfaces cannot be fully described by the framework of Amontons' laws of friction and that additional parameters (e.g., ?f and SSAC) are required, when their friction, lubrication, and wear properties are important considerations in related nanodevices. PMID:24219790
DEFF Research Database (Denmark)
Frederiksen, Jens Mejer; Geiker, Mette Rica
2008-01-01
Prediction of chloride ingress into concrete is an important part of durability design of reinforced concrete structures exposed to chloride containing environment. This paper presents the state-of-the art: an analytical model which describes chloride profiles in concrete as function of depth and time, and where both the surface chloride concentration and the diffusion coefficient are allowed to vary in time; the Mejlbro-Poulsen model is the general solution to Fick’s 2nd law. The paper also presents conversion formulas for the four decisive but rather abstract parameters to parameters, which makes physical sense for the design engineer, i.e. the achieved chloride diffusion coefficients at 1 year and 100 years, D1 and D100 respectively, and the corresponding achieved chloride concentrations at the exposed concrete surface, C1 and C100. Data from field exposure supports the assumption of time dependent surface chloride concentrations and the diffusion coefficients. Model parameters for Portland cement concretes with and without silica fume and fly ash in marine atmospheric and submerged South Scandinavian environment are suggested in a companion paper based on 10 years field exposure data.
Leblay, P.; Henry, J. F.; Caron, D; Leducq, D.; Bontemps, A.; Fournaison, L.
2012-01-01
A new methodology has been developed to characterize the loss of efficiency of heat exchangers due to a maldistribution of the two-phase flow. The approach consists to measure the distribution of the local heat transfer coefficients with a non-intrusive and fast measurement method, based on a periodic excitation by Joule effect and infrared thermography measurement. An analytical model of the heat transfer is used to deduce heat transfer coefficients from the amplitude of the outside tube tem...
Directory of Open Access Journals (Sweden)
Trumi? B.
2009-01-01
Full Text Available In order to increase the active surface of platinum catalysts for ammonia oxidation and on the basis of theoretic considerations and tests in industrial environment, we have finally decided on their specific design. Efficiency on the newly designed catalyst was checked in industrial circumstances. A comparative analysis of the total ammonia recovery coefficient between the mentioned new catalysts and previously applied platinum catalysts was carried out. All advantages of catalysts with increased active surfaces were confirmed and a new method of their manufacturing process was selected.
Directory of Open Access Journals (Sweden)
Reinaldo Sanchez Arriagada
2007-01-01
Full Text Available Una correlación matemática para determinar el coeficiente convectivo de materia durante la evaporación de agua desde la superficie húmeda, fue desarrollada para su aplicación con aire húmedo con bajas diferencias sicrométricas y temperaturas del aire sobre los 60°C. La teoría clásica para determinar coeficientes convectivos de calor y de materia, a través de parámetros adimensionales y de las analogías fenomenológicas difusivas, tienen validez sólo para aire seco. En el secado de sólidos, donde se requiere controlar las tasas de secado para evitar un daño físico en el producto, se impone la necesidad de operar con temperaturas bulbo húmedo por sobre los 40°C o diferencias sicrométricas moderadas. En esos rangos, las expresiones que relacionan los coeficientes convectivos de calor y materia, presentan errores que varían entre 26% y 113% para temperatura de bulbo húmedo entre 30°C y 70°C con diferencia sicrométrica de 10°C. La expresión formulada para esta aplicación, se plantea como una función de: el coeficiente convectivo de transferencia de calor, la temperatura bulbo húmedo y la diferencia sicrométrica. Los resultados obtenidos permiten establecer que, para las condiciones extremas de temperatura de bulbo húmedo y diferencia sicrométrica antes señalada el error se sitúa entre -1.4% a 2.14%, respecto del obtenido a partir de la metodología clásica La correlación obtenida es de forma polinomial, de fácil operación y viable de ser incorporada a cualquier modelo de simulación para la predicción de la dinámica del secadoA mathematical correlation to determine the mass coefficient, during the evaporation of water from a wet surface, was developed for their application in wet air with low psychometric differential and with air temperature above 60°C. The classic theory that has been used in order to get heat and mass convective coefficients, through non-dimensional parameters and phenomenological analogies, turns out to be valid only for dry air. In the particular case of solids drying, where operation requires to be performed under controlled drying rates, in order to prevent physical damage from affecting the product, is necessary to operate on a wet bulb temperature above 40ºC or at moderate psychometric differential. When we work under those ranges of temperature, the expressions that relate heat and mass convective coefficients show errors between 26% and 113% for wet temperature between 30°C and 70°C and psychometric difference of 30°C The expression that has been given for this application is stated as a function of the following: heat transfer coefficient, wet bulb temperature, and psychometric differential. The obtained results allow to settle down that, for the extreme conditions of wet bulb temperature and psychometric differences assigned before, the error is located among -1.4% to 2.14%, regarding the obtained through the classic methodology. The obtained correlation has polynomial form, of easy operation and viable of being incorporate to any simulation pattern for the prediction of the dynamics of the drying
Scientific Electronic Library Online (English)
Reinaldo, Sanchez Arriagada.
Full Text Available Una correlación matemática para determinar el coeficiente convectivo de materia durante la evaporación de agua desde la superficie húmeda, fue desarrollada para su aplicación con aire húmedo con bajas diferencias sicrométricas y temperaturas del aire sobre los 60°C. La teoría clásica para determinar [...] coeficientes convectivos de calor y de materia, a través de parámetros adimensionales y de las analogías fenomenológicas difusivas, tienen validez sólo para aire seco. En el secado de sólidos, donde se requiere controlar las tasas de secado para evitar un daño físico en el producto, se impone la necesidad de operar con temperaturas bulbo húmedo por sobre los 40°C o diferencias sicrométricas moderadas. En esos rangos, las expresiones que relacionan los coeficientes convectivos de calor y materia, presentan errores que varían entre 26% y 113% para temperatura de bulbo húmedo entre 30°C y 70°C con diferencia sicrométrica de 10°C. La expresión formulada para esta aplicación, se plantea como una función de: el coeficiente convectivo de transferencia de calor, la temperatura bulbo húmedo y la diferencia sicrométrica. Los resultados obtenidos permiten establecer que, para las condiciones extremas de temperatura de bulbo húmedo y diferencia sicrométrica antes señalada el error se sitúa entre -1.4% a 2.14%, respecto del obtenido a partir de la metodología clásica La correlación obtenida es de forma polinomial, de fácil operación y viable de ser incorporada a cualquier modelo de simulación para la predicción de la dinámica del secado Abstract in english A mathematical correlation to determine the mass coefficient, during the evaporation of water from a wet surface, was developed for their application in wet air with low psychometric differential and with air temperature above 60°C. The classic theory that has been used in order to get heat and mass [...] convective coefficients, through non-dimensional parameters and phenomenological analogies, turns out to be valid only for dry air. In the particular case of solids drying, where operation requires to be performed under controlled drying rates, in order to prevent physical damage from affecting the product, is necessary to operate on a wet bulb temperature above 40ºC or at moderate psychometric differential. When we work under those ranges of temperature, the expressions that relate heat and mass convective coefficients show errors between 26% and 113% for wet temperature between 30°C and 70°C and psychometric difference of 30°C The expression that has been given for this application is stated as a function of the following: heat transfer coefficient, wet bulb temperature, and psychometric differential. The obtained results allow to settle down that, for the extreme conditions of wet bulb temperature and psychometric differences assigned before, the error is located among -1.4% to 2.14%, regarding the obtained through the classic methodology. The obtained correlation has polynomial form, of easy operation and viable of being incorporate to any simulation pattern for the prediction of the dynamics of the drying
Alkali halide solutions under thermal gradients: soret coefficients and heat transfer mechanisms.
Römer, Frank; Wang, Zilin; Wiegand, Simone; Bresme, Fernando
2013-07-11
We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na(+)/K(+)-Cl(-)) to thermal gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret coefficient is of the order of 10(-3) K(-1) for a wide range of concentrations. These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T ? 315 K), whereas it increases at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight on the heat transport mechanism and the behavior of the Soret coefficient in aqueous solutions. The models employed in this work reproduce the magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish a correlation between the sign and magnitude of the Soret coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided. PMID:23758489
Haddag, B.; Atlati, S.; Nouari, M.; Zenasni, M.
2015-10-01
This paper deals with the modelling and identification of the heat exchange at the tool-workpiece interface in machining. A thermomechanical modelling has been established including heat balance equations of the tool-workpiece interface which take into account the heat generated by friction and the heat transfer by conduction due to the thermal contact resistance. The interface heat balance equations involve two coefficients: heat generation coefficient (HGC) of the frictional heat and heat transfer coefficient (HTC) of the heat conduction (inverse of the thermal contact resistance coefficient). Using experimental average heat flux in the tool, estimated for several cutting speeds, an identification procedure of the HGC-HTC couple, involved in the established thermomechanical FE-based modelling of the cutting process, has been proposed, which gives the numerical heat flux equal the measured one for each cutting speed. Using identified values of the HGC-HTC couple, evolution laws are proposed for the HGC as function of cutting speed, and then as function of sliding velocity at the tool-workpiece interface. Such laws can be implemented for instance in a Finite Element code for machining simulations.
Correlation of the surface layer stress coefficient and stress corrosion cracking. I
International Nuclear Information System (INIS)
The time to failure, the crack propagation velocity, and the surface layer stress of titanium (6Al--4V) and a 4130 steel were measured as a function of applied potential and concentration in solutions of HCl-CH3OH and NaCl. Compact tension specimens were used in the SCC tests. It is shown that a direct correlation, independent of the applied potential or solution concentration, exists between the surface layer stress and SCC. The data show that the resistance to stress corrosion cracking (SCC) decreases under conditions that enhance the strength of the surface layer. It appears that SCC occurs when the environmenal conditions raise the surface layer stress coefficient above a critical value
Fouling of roughened stainless steel surfaces during convective heat transfer to aqueous solutions
International Nuclear Information System (INIS)
The deterioration of heat transfer performance due to fouling is the prime cause for higher energy consumption and inefficiency in many industrial heat exchangers such as those in power plants, refineries, food and dairy industries. Fouling is also a very complex process in which many geometrical, physical and operating parameters are involved with poorly understood interaction. Among them, the surface roughness is an important surface characteristic that would greatly influence crystallisation fouling mechanisms and hence deposition morphology and stickability to the surface. In this work, the effect of the surface roughness of AISI 304 BA stainless steel surfaces on fouling of an aqueous solution with inverse solubility behaviour has been investigated under convective heat transfer. Several experiments have been performed on roughened surfaces ranging from 0.18 to 1.55 ?m for different bulk concentrations and heat fluxes. The EDTA titration method was used to measure the concentration of the calcium sulphate salt in order to maintain it at constant value during each fouling run. Experimental results show that the heat transfer coefficient of very rough surfaces (1.55 ?m) decreases more rapidly than that of 0.54 ?m. Several facts contribute to this behaviour notably (1) increased of primary heterogeneous nucleation rate on the surfaces; (2) reduction of local shear stress in the valleys and (3) reduced removal rate of the crystals from the surfaces where the roughness elements protrude out of the viscous sub-layer. The results also show linear and proportional variation of the fouling rate and heat flux within the range of operating conditions. In addition, the deposition process in terms of fouling rate could only be affected at lower surface contact angles. Such results would particularly be of interest for new surface treatment technologies which aim at altering the surface texture
International Nuclear Information System (INIS)
Highlights: • Infra-red thermographic study of Taylor bubble train flow in square mini-channel. • Design of experiments for measurement of local streamwise Nusselt number. • Minimizing conjugate heat transfer effects and resulting errors in data reduction. • Benchmarking against single-phase flow and three-dimensional computations. • Local heat transfer enhancement up to two times due to Taylor bubble train flow. -- Abstract: In mini/micro confined internal flow systems, Taylor bubble train flow takes place within specific range of respective volume flow ratios, wherein the liquid slugs get separated by elongated Taylor bubbles, resulting in an intermittent flow situation. This unique flow characteristic requires understanding of transport phenomena on global, as well as on local spatio-temporal scales. In this context, an experimental design methodology and its validation are presented in this work, with an aim of measuring the local heat transfer coefficient by employing high-resolution InfraRed Thermography. The effect of conjugate heat transfer on the true estimate of local transport coefficients, and subsequent data reduction technique, is discerned. Local heat transfer coefficient for (i) hydrodynamically fully developed and thermally developing single-phase flow in three-side heated channel and, (ii) non-boiling, air–water Taylor bubble train flow is measured and compared in a mini-channel of square cross-section (5 mm × 5 mm; Dh = 5 mm, Bo ? 3.4) machined on a stainless steel substrate (300 mm × 25 mm × 11 mm). The design of the setup ensures near uniform heat flux condition at the solid–fluid interface; the conjugate effects arising from the axial back conduction in the substrate are thus minimized. For benchmarking, the data from single-phase flow is also compared with three-dimensional computational simulations. Depending on the employed volume flow ratio, it is concluded that enhancement of nearly 1.2–2.0 times in time-averaged local streamwise Nusselt number can be obtained by Taylor bubble train flow, as compared to fully developed single-phase flow. This enhancement is attributed to the intermittent intrusion of Taylor bubbles in the liquid flow which drastically changes the local fluid temperature profiles. It is important to maintain proper boundary conditions during the experiment while estimating local heat transfer coefficient, especially in mini-micro systems
Chen, Shi; Zhang, Yinhong; Lin, Shuyu; Fu, Zhiqiang
2014-02-01
The electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices is investigated by the transfer matrix method. Research results show the high electromechanical coupling coefficient can be obtained in these systems. The optimization design of it is also discussed fully. It is significantly influenced by electrical boundary conditions on interfaces, thickness ratios of piezoelectric and non-piezoelectric layers, and material parameters (such as velocities of pure longitudinal and transversal bulk waves in non-piezoelectric layers). In order to obtain higher electromechanical coupling coefficient, shorted interfaces, non-piezoelectric materials with large velocities of longitudinal and transversal bulk waves, and proper thickness ratios should be chosen. PMID:24035609
Gillespie, DRH; Byerley, AR; Ireland, PT; Wang, Z; Jones, TV; Kohler, ST
1994-01-01
The local heat transfer inside the entrance to large scale models of film cooling holes has been measured using the transient heat transfer technique. The method employs temperature sensitive liquid crystals to measure the surface temperature of large scale perspex models. Full distributions of local Nusselt number were calculated based on the cooling passage centreline gas temperature ahead of the cooling hole. The circumferentially averaged Nusselt number was also calculated based on the lo...
Momentum transfer in a Brillouin surface scattering
International Nuclear Information System (INIS)
The theory of acoustic excitation scattering in the surface of Brilloiun of opaque materials, is related to the question of momentum transfexed from radiation fields to the material when the incident eight is scattered in a measurable spectrum. (A.C.A.S.)
Subcooled flow boiling heat transfer from microporous surfaces in a small channel
International Nuclear Information System (INIS)
The continuously increasing requirement for high heat transfer rate in a compact space can be met by combining the small channel/microchannel and heat transfer enhancement methods during fluid subcooled flow boiling. In this paper, the sintered microporous coating, as an efficient means of enhancing nucleate boiling, was applied to a horizontal, rectangular small channel. Water flow boiling heat transfer characteristics from the small channel with/without the microporous coating were experimentally investigated. The small channel, even without the coating, presented flow boiling heat transfer enhancement at low vapor quality due to size effects of the channel. This enhancement was also verified by under-predictions from macro-scale correlations. In addition to the enhancement from the channel size, all six microporous coatings with various structural parameters were found to further enhance nucleate boiling significantly. Effects of the coating structural parameters, fluid mass flux and inlet subcooling were also investigated to identify the optimum condition for heat transfer enhancement. Under the optimum condition, the microporous coating could produce the heat transfer coefficients 2.7 times the smooth surface value in subcooled flow boiling and 3 times in saturated flow boiling. The combination of the microporous coating and small channel led to excellent heat transfer performance, and therefore was deemed to have promising application prospects in many areas such as air conditioning, chip cooling, refrigeration systems, and many others involving compact heat exchangers. (authors)
Cushing, G W; Navin, J K; Valadez, L; Johánek, V; Harrison, I
2011-04-01
An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(T(g), T(s); ?), on metal surfaces for which the impinging gas temperature, T(g), and surface temperature, T(s), can be independently varied, along with the angle of incidence, ?, of the impinging gas. Effusive beam experiments with T(g) = T(s) = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ?), which when averaged over the cos?(?)/? angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(T(g), T(s); ?) measurements for which T(g) ? T(s) provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the T(g) of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111). PMID:21529024
Enhanced surface friction coefficient and hydrophobicity of TPE substrates using an APPJ system
Sainz-García, Elisa; Alba-Elías, Fernando; Múgica-Vidal, Rodolfo; González-Marcos, Ana
2015-02-01
An APPJ system was used to deposit a coating that combines a low friction coefficient with a high water contact angle (WCA) on a thermoplastic elastomer substrate (TPE) that is used in automotive profiling. The main drawback of this research is that groups that improve the hydrophobicity of the surface worsen its tribological properties. To overcome this, this study explored the use of various mixtures of differing proportions of two precursors. They were a siloxane, aminopropyltriethoxysilane (APTES) that was used to reduce the friction coefficient by its content of SiOx and a fluorinated compound, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FLUSI) that was used to improve the water-repellency characteristics, due to the presence of CF2 long chains. The coatings were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), dynamic Water Contact Angle (WCA), stability tests and tribological tests. It was found that an increase of the absorbance area under the SiOSi peak and inorganic groups is related to lower friction coefficients. On the other hand, the higher the CF2 percentage is, the higher the WCA is. The sample that was coated with 25% of FLUSI and 75% of APTES combined the improvements of both functional properties, the friction coefficient and the WCA. It has an average friction coefficient that is (0.530 ± 0.050) 51.5% lower and a WCA that is (?adv = 119.8° ± 4.75) 4.4% higher than the uncoated TPE sample. A satisfactory stability in humid ambient for twelve months showed a slight decrease of WCA (4.4%) for this sample. The results of this study permit one to realize the effectiveness of using fluorinated precursors to avoid a significant decrease in the WCA when applying a precursor to anti-friction improvement.
Surface heat transfer due to sliding bubble motion
Energy Technology Data Exchange (ETDEWEB)
Donnelly, Brian [Mechanical and Manufacturing Engineering, Trinity College Dublin, College Green Dublin 2 (Ireland)], E-mail: donnelbg@tcd.ie; O' Donovan, Tadhg S. [School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh (United Kingdom); Murray, Darina B. [Mechanical and Manufacturing Engineering, Trinity College Dublin, College Green Dublin 2 (Ireland)
2009-05-15
The presence of a rising bubble in a fluid can greatly enhance heat transfer from adjacent heated surfaces such as in shell and tube heat exchangers and chemical reactors. One specific case of this is when a bubble impacts and slides along the surface. The result is heat transfer enhancement by two main mechanisms: first, the bubble itself acting as a bluff body, and second, the wake generated behind the bubble leads to increasing mixing. The current research is concerned with measuring the heat transfer from a submerged heated surface that is subject to a sliding bubble flow. An ohmically heated 25 {mu}m thick stainless steel foil, submerged in a water tank, forms the test surface. An air bubble is injected onto the lower surface of the test plate, it slides along its length and the effects are monitored by two methods. Thermochromic liquid crystals (TLC's) are used in conjunction with a high speed camera to obtain a time varying 2D temperature map of the test surface. A second synchronised camera mounted below the foil records the bubble motion. Tests are performed at angles of 10 deg., 20 deg. and 30 deg. to the horizontal. This paper reports on the enhancement of the heat transfer due to the bubble. It has been found that the angle made between the heated surface and the horizontal influences heat transfer by changing the bubble's motion. In general, a steeper angle leads to a higher bubble velocity, which results in greater heat transfer enhancement.
International Nuclear Information System (INIS)
Physical sputtering yields from the carbon surface irradiated by the boundary plasma are obtained with the use of the Monte Carlo simulation code ACAT. The yields are calculated for many random initial energy and angle values of incident protons or deuterons with a Maxwellian velocity distribution, and then averaged. Here the temperature of the boundary plasma, the sheath potential and the angle ? between the magnetic field line and the surface normal are taken into account. A new fitting formula for an arrangement of the numerical data of sputtering yield is introduced, in which six fitting parameters are determined from the numerical results and listed. These results provide a way to estimate the erosion of carbon materials irradiated by the boundary plasma. The particle reflection coefficients for deuterons and their neutrals from a carbon surface are also calculated by the same code and presented together with, for comparison, that for the case of monoenergetic normal incidence. ((orig.))
International Nuclear Information System (INIS)
This document presents tables of diet-to-milk transfer coefficients for radioactive and stable isotopes in the cow. The values are based on an extensive literature review of the secretion of radioisotopes in milk and the concentrations of radioactive or stable isotopes in milk and feed. Transfer coefficients were compiled and tabulated for isotopes of more than 70 elements. The values are summarized in a table of elemental transfer coefficients and also organized into separate tables that reveal their elemental systematics and the effects of physical and chemical form
Rate coefficients for charge transfer between hydrogen and the first 30 elements
International Nuclear Information System (INIS)
We present analytic fits to charge exchange rate coefficients over the full range of temperatures which occurs in photoionized or shock-heated plasmas. We consider reactions between neutral hydrogen and all elements with parent ion charge q=1-4 up to Z=30. Many rates were obtained from various sources in the literature. For reactions for which no data were available, we calculated rates using the Landau-Zener formalism. For these new reactions, we tabulate both total and state-specific rate coefficients. All are fitted with a consistent, accurate formula. These fits may be incorporated easily into spectral synthesis codes, and we make available an electronic form of our results. We draw attention to the most important reactions without high-quality rate coefficients to encourage further work. copyright 1996 The American Astronomical Society
Rate coefficients for charge transfer between hydrogen and the first 30 elements
Energy Technology Data Exchange (ETDEWEB)
Kingdon, J.B.; Ferland, G.J. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)
1996-09-01
We present analytic fits to charge exchange rate coefficients over the full range of temperatures which occurs in photoionized or shock-heated plasmas. We consider reactions between neutral hydrogen and all elements with parent ion charge {ital q}=1{minus}4 up to {ital Z}=30. Many rates were obtained from various sources in the literature. For reactions for which no data were available, we calculated rates using the Landau-Zener formalism. For these new reactions, we tabulate both total and state-specific rate coefficients. All are fitted with a consistent, accurate formula. These fits may be incorporated easily into spectral synthesis codes, and we make available an electronic form of our results. We draw attention to the most important reactions without high-quality rate coefficients to encourage further work. {copyright} {ital 1996 The American Astronomical Society.}
Rate Coefficients for Charge Transfer between Hydrogen and the First 30 Elements
Kingdon, J. B.; Ferland, G. J.
1996-09-01
We present analytic fits to charge exchange rate coefficients over the full range of temperatures which occurs in photoionized or shock-heated plasmas. We consider reactions between neutral hydrogen and all elements with parent ion charge q = 1-4 up to Z = 30. Many rates were obtained from various sources in the literature. For reactions for which no data were available, we calculated rates using the Landau-Zener formalism. For these new reactions, we tabulate both total and state-specific rate coefficients. Ml are fitted with a consistent, accurate formula. These fits may be incorporated easily into spectral synthesis codes, and we make available an electronic form of our results. We draw attention to the most important reactions without high-quality rate coefficients to encourage further work.
Wang, Tao; Jiang, Yu-Yan; Jiang, Hai-Chang; Guo, Cong; Guo, Chao-Hong; Tang, Da-Wei; Rong, Li-Jian
2015-07-01
A number of technologies have been developed to enhance boiling heat transfer (BHT). The enhancements of BHT depend on the size and geometry of the micro/mini structures and it seems difficult to design a structure that is optimum for all heat transfer conditions. This letter reports a study on adaptive control and enhancement of BHT by shape-memory alloy (SMA) structures. The experimental results of BHT on structured porous surfaces show that the SMA surface with recoverable structures has advantages for heat transfer both in the improvement of heat transfer coefficient and in the extending of operating range. The potential applications of such enhancement structures in diverse heat transfer devices are perhaps the most exciting.
International Nuclear Information System (INIS)
The paper presents a new heat transfer correlation of water at supercritical pressure after review on existing heat transfer correlations. The new correlation is optimized by genetic algorithms based on existing test data. Based on current results, we conclude that genetic algorithms are effective to search a global optimized correlation but it is important to carefully select representative and authentic test data to reach an optimized solution and special attention needs to be paid on the deteriorated heat transfer region in the design of supercritical water reactor because it can not be predicted well by any correlations reviewed. (orig.)
Directory of Open Access Journals (Sweden)
Mr.M Basavaraju
2013-09-01
Full Text Available The morphological features of the surface in both micro and macro levels are important factors governing the tribological behavior of the contacting surfaces. Surface hardness is also an important factor which governs the friction and wear behaviors of the contacting surfaces. Surface morphology of a tool is an important factor as it primarily controls the tribological behavior at the interface which in turn controls the surface finish of products. In the present investigation a pin-on-plate sliding tester was used to identify the effect of surface morphology and hardness on co-efficient of friction and transfer layer which characterizes the tribological behavior. The morphology of mild steel (EN8 plate surfaces were modified by employing three different surface modification methods like grinding (silicon carbide wheel polishing, shot blasting and electric discharge machining methods. Surface roughness parameters which characterize the morphology of the steel plates were measured using a three dimensional optical profilometer. Role of hardness is studied by employing lead, copper and Aluminum (Al6082 pins which were slid against steel plates. Experiments were conducted for plate inclination angles of 1, 1.5,2 and 2.5 degrees. Normal load was varied from 1 to 150N during the tests. Experiments were conducted under dry condition in ambient environment. Scanning electron microscope was used to study the formation of transfer layer on plate and pin surfaces. It was observed that the co-efficient of friction and transfer layer formation were found to depend on the surface morphology of the harder surface. The quantum of transfer layer formation on the surfaces is found to increase with increase in surface roughness
Zhu, Jie; Luo, Yuting; Tian, Jian; Li, Juan; Gao, Xuefeng
2015-05-27
We report that the dropwise condensation heat transfer (DCHT) effectiveness of copper surfaces can be dramatically enhanced by in situ grown clustered ribbed-nanoneedles. Combined experiments and theoretical analyses reveal that, due to the microscopically rugged and low-adhesive nature of building blocks, the nanosamples can not only realize high-density nucleation but constrain growing condensates into suspended microdrops via the self-transport and/or self-expansion mode for subsequently self-propelled jumping, powered by coalescence-released excess surface energy. Consequently, our nanosample exhibits over 125% enhancement in DCHT coefficient. This work helps develop advanced heat-transfer materials and devices for efficient thermal management and energy utilization. PMID:25966966
Liu, Xiaomo; Lin, Jiuxiang; Ding, Peng
2013-01-01
In this study, we tested the surface roughness of bracket slots and the friction coefficient between the bracket and the stainless steel archwire before and after orthodontic treatment. There were four experimental groups: groups 1 and 2 were 3M new and retrieved brackets, respectively, and groups 3 and 4 were BioQuick new and retrieved brackets, respectively. All retrieved brackets were taken from patients with the first premolar extraction and using sliding mechanics to close the extraction space. The surface roughness of specimens was evaluated using an optical interferometry profilometer, which is faster and nondestructive compared with a stylus profilometer, and provided a larger field, needing no sample preparation, compared with atomic force microscopy. Orthodontic treatment resulted in significant increases in surface roughness and coefficient of friction for both brands of brackets. However, there was no significant difference by brand for new or retrieved brackets. These retrieval analysis results highlight the necessity of reevaluating the properties and clinical behavior of brackets during treatment to make appropriate treatment decisions. PMID:23086715
Directory of Open Access Journals (Sweden)
Sundus Hussein Abd
2012-01-01
Full Text Available In this research, an experimental study was conducted to high light the impact of the exterior shape of a cylindrical body on the forced and free convection heat transfer coefficients when the body is hold in the entrance of an air duct. The impact of changing the body location within the air duct and the air speed are also demonstrated. The cylinders were manufactured with circular, triangular and square sections of copper for its high thermal conductivity with appropriate dimensions, while maintaining the surface area of all shapes to be the same. Each cylinder was heated to a certain temperature and put inside the duct at certain locations. The temperature of the cylinder was then monitored. The heat transfer coefficient were then calculated for forced convection for several Reynolds number (4555-18222.The study covered free convection impact for values of Rayleigh number ranging between (1069-3321. Imperical relationships were obtained for all cases of forced and free convection and compared with equations of circular cylindrical shapes found in literature. These imperical equations were found to be in good comparison with that of other sources.
Effect of Contaminants on Mass Transfer Coefficients in Bubble Column and Airlift Contactors.
Czech Academy of Sciences Publication Activity Database
Vasconcelos, J.M.T.; Rodrigues, J.L.M.; Orvalho, Sandra Petronilho; Alves, S. S.; Mendes, R.L.; Reis, A.
2003-01-01
Ro?. 58, 8 (2003) , s. 1431-1440. ISSN 0009-2509 Institutional research plan: CEZ:AV0Z4072921 Keywords : mass transfer * bubble * surfactant Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.562, year: 2003
International Nuclear Information System (INIS)
Reflection coefficients for carbon and hydrocarbon atoms/molecules on carbon-based surfaces are critically needed for plasma-surface interaction analysis in fusion devices, as carbon will continue to be used in next step devices like ITER. These have been calculated at different energies and angles with a molecular dynamics code using the Brenner hydrocarbon potential. Hydrogen saturated graphite was prepared by bombarding a graphite lattice with hydrogen, until a saturation at ?0.42 H/C. Carbon at 45 deg has a reflection coefficient (R) of 0.64±0.01 at thermal energy, decreasing to 0.19±0.01 at 10 eV. Carbon dimers (Rthermal=0.51,R>1eV?0.10) tend to stick more readily than carbon trimers (Rthermal=0.63,R10eV=0.16). Hydrocarbons reflect as molecules at thermal energies and break up at higher energies. The total reflection via these fragments decreases with energy, the number of unpaired electrons, and changing hybridization from sp3 to sp2 to sp. The results compare reasonably well with binary collision modeling for higher energies and experimental sticking data at thermal energies. A second surface, representing a 'soft' redeposited carbon layer formed by the deposition of hydrocarbons onto a graphite surface, is also analyzed. In general, reflection is lower from the 'soft' surface by 0.1-0.2. This reflection data can and has been incorporated in erosion/redeposition codes to allow improved modeling of chemically eroded carbon transport in fusion devices
Directory of Open Access Journals (Sweden)
Dr.S Ranganatha
2013-09-01
Full Text Available Hot and cold forming of metals is carried out in industry for manufacturing engineering components. Such manufacturing processes employ dies, whose surface condition is one of the factors which characterize the surface finish of engineering components. The surface finish of engineering components is largely influenced by the tribological phenomenon at die and components interface. Lubrication, morphology and hardness of die surface are found to control surface finish of the products. In the present investigation a pin-on-plate sliding tester was used to identify the effect of surface morphology, lubrication and hardness on co-efficient of friction and transfer layer which characterizes the tribological behaviour. The morphology of mild steel (EN8 plate surfaces were modified by employing three different surface modification methods like grinding (silicon carbide wheel polishing, shot blasting and electric discharge machining methods. Surface roughness parameters which characterize the morphology of the steel plates were measured using a three dimensional optical profilometer. Role of hardness is studied by employing lead, copper and Aluminum (Al6082 pins which were slid against steel plates. Experiments were conducted for plate inclination angles of 1, 1.5,2 and 2.5 degrees. Normal load was varied from 1 to 150N during the tests. Experiments were conducted under lubricated condition in ambient environment. Scanning electron microscope was used to study the formation of transfer layer on plate and pin surfaces. It was observed that the co-efficient of friction and transfer layer formation were found to depend on the surface morphology of the harder surface under lubricated condition. The quantum of transfer layer formation on the surfaces is found to increase with increase in surface roughness.
Surface and Volume Symmetry Energy Coefficients of a Neutron-Rich Nucleus
International Nuclear Information System (INIS)
Using an isobaric method, the symmetry-energy coefficient (asym) of a neutron-rich nucleus is obtained from experimental binding energies. The shell effects are shown in a*sym/A ? 4asym/A of nuclei. A (sub)magic neutron magic number N = 40 is suggested in a very neutron-rich nucleus, and a*sym/A of a nucleus is found to decrease when its mass increases. The a*sym/A of a very neutron-rich nucleus with large mass saturates. The volume-symmetry coefficients (bv) and surface-symmetry coefficients (bs) of a neutron-rich nucleus are extracted from a*sym/A by a correlation a*sym/A = bv/A ? bs/A4/3. It is found that bv and bs decrease when the nucleus becomes more neutron-rich, and tend to saturate in the very neutron-rich nucleus. A linear correlation between bv and bs is obtained in nuclei with different neutron-excess I, and bv of I > 7 nuclei is found to coincide with the results of infinite nuclear matter asym = 32 ± 4 MeV, and bs/bv of the nucleus is found to coincide with the results of the finite-range liquid-drop model results
Some observations on boiling heat transfer with surface oscillation
International Nuclear Information System (INIS)
The effects of surface oscillation on pool boiling heat transfer are experimentally studied. Experiments were performed in saturated ethanol and distilled water, covering the range from nucleate to film boiling except in the transition region. Two different geometries were employed as the heating surface with the same wetting area, stainless steel pipe and molybdenum ribbon. The results confirm earlier work on the effect of surface oscillation especially in lower heat flux region of nucleate boiling. Interesting boiling behavior during surface oscillation is observed, which was not referred to in previous work. (2 figures) (Author)
Flow boiling heat transfer on nanowire-coated surfaces with highly wetting liquid
International Nuclear Information System (INIS)
Owing to the recent advances in nanotechnology, one significant progress in energy technology is increased cooling ability. It has recently been shown that nanowires can improve pool boiling heat transfer due to the unique features such as enhanced wetting and enlarged nucleation sites. Applying such nanowires on a flow boiling, which is another major class of boiling phenomenon that is associated with forced convection, is yet immature and scarce despite its importance in various applications such as liquid cooling of energy, electronics and refrigeration systems. Here, we investigate flow boiling heat transfer on surfaces that are coated with SiNWs (silicon nanowires). Also, we use highly-wetting dielectric liquid, FC-72, as a working fluid. An interesting wetting behavior is observed where the presence of SiNWs reduces wetting and wicking that in turn leads to significant decrease of CHF (critical heat flux) compared to the plain surface, which opposes the current consensus. Also, the effects of nanowire length and Reynolds number on the boiling heat transfer are shown to be highly nonmonotonic. We attempt to explain such an unusual behavior on the basis of wetting, nucleation and forced convection, and we show that such factors are highly coupled in a way that lead to unusual behavior. - Highlights: • Observation of suppressed wettability in the presence of surface roughness (nanowires). • Significant reduction of critical heat flux in the presence of nanowires. • Nonmonotonic behavior of heat transfer coefficient vs. nanowire length and Reynolds number
de Gracia, A.; David, Damien; Castell, Albert; Cabeza, Luisa F.; Virgone, Joseph
2013-01-01
This paper provides a new correlation to determine the heat transfer coefficient between an air flow and a plate made of phase change material (PCM ). This correlation was built for the simulation of heat storage units containing PCM plates subjected to an inlet temperature step. The presented correlation has the following form: View the MathML sourceNux,tPCM=NuPSM*fPCM. The first term NuPSM is for a plate made of traditional material. The term fPCM is a perturbation due to the phase change i...
Directory of Open Access Journals (Sweden)
Zhihui Wang
2013-01-01
Full Text Available This study investigates the frequency bifurcation phenomena of a typical voltage-fed resonant converter based on mutual induction model. It is found that the Zero Current Switching (ZCS operating frequency has the bifurcation region as the coupling coefficient varies due to the distance. The expression for the bifurcation boundary is derived and analyzed. Such results are very useful for guiding the design of practical Inductively Coupled Power Transfer (ICPT systems especially in applications which have the requirement of the position flexibility. Analytical results are verified both via MATLAB simulations and experimental prototype.
Directory of Open Access Journals (Sweden)
Yu. I. Troitskaya
2013-10-01
Full Text Available The surface-drag and mass-transfer coefficients are determined within a self-consistent problem of wave-induced perturbations and mean fields of velocity and density in the air, using a quasi-linear model based on the Reynolds equations with down-gradient turbulence closure. Investigation of a harmonic wave propagating along the wind has disclosed that the surface drag is generally larger for shorter waves. This effect is more pronounced in the unstable and neutral stratification. The stable stratification suppresses turbulence, which leads to weakening of the momentum and mass transfer.
International Nuclear Information System (INIS)
Heat transfer from a high temperature surface of copper which is 100 mm in diameter to liquid-sodium argon mist flow has been investigated experimentally in the ranges of surface temperature from 450 K to 850 K and sodium mass flux density up to 2 [kg/m2s]. In experiments, a quench method is adopted and a new needle type spray nozzle is used to atomize liquid sodium. It is clarified that heat transfer coefficient increases proportionally with sodium mass flux density and is enhanced with increase of argon gas volumetric flow rate. (author)
Scientific Electronic Library Online (English)
Enrique, Torres-Tamayo; Yoalbys, Retirado-Medianeja; Ever, Góngora-Leyva.
2014-04-01
Full Text Available La pérdida de eficiencia del proceso de enfriamiento del licor amoniacal, mediante el uso de intercambiadores de calor de placas, está asociada a imprecisiones en la estimación de los coeficientes de transferencia de calor y la acumulación de incrustaciones en la superficie de intercambio. El objeti [...] vo de la investigación es determinar los coeficientes de transferencia de calor y la influencia de las incrustaciones en la pérdida de eficiencia de la instalación. Mediante un procedimiento iterativo se estableció la ecuación del número de Nusselt y su relación con el número de Reynolds y Prandtl. Se utilizó un diseño experimental multifactorial. Los resultados predicen el conocimiento de los coeficientes para el cálculo del número de Nusselt en ambos fluidos. Los valores de los coeficientes del licor amoniacal son inferiores, ello se debe a la presencia de componentes gaseosos. La ecuación obtenida muestra correspondencia con el modelo de Buonapane, el error comparativo es del 3,55 %. Abstract in english The loss of efficiency of the ammonia liquor cooling process, by means of the plate heat exchanger, is associated to the incorrect estimate of the heat transfer coefficients and the accumulation of inlays in the exchange surface. The objective of the investigation is to determine the transfer coeffi [...] cients and the influence of the inlays in the efficiency loss of the installation. By means of an iterative procedure was obtained the Nusselt number equation and the relationship with the Reynolds and Prandtl number, for it was used it a design experimental multifactorial. The results predict the knowledge of the coefficients for the calculation of the Nusselt number for both fluids. The ammonia liquor coefficients values are inferior, due to the presence of gassy components. The obtained equation shows correspondence with the Buonapane pattern, the comparative error is 3,55 %.
Alman, D. A.; Ruzic, D. N.; Brooks, J. N.
2001-10-01
Reflection coefficients of carbon and hydrocarbon molecules have been calculated with a molecular dynamics code. The code uses the Brenner hydrocarbon potential, an empirical many-body potential that can model the chemical bonding in small hydrocarbon molecules and graphite surfaces. A variety of incident energies and angles have been studied. Typical results for carbon show reflection coefficients 0.4 at thermal energy, decreasing to a minimum of 0.15 at 10-20 eV, and then increasing again. Distributed computing is used to distribute the work among 10-20 desktop PCs in the laboratory. The system consists of a client application run on all of the PCs and a single server machine that distributes work and compiles the results sent back from the clients. The client-server software is written in Java and requires no commercial software packages. Thus, the MD code benefits from multiprocessor-like speed-up at no additional cost by using the idle CPU cycles that would otherwise be wasted. These calculations represent an important improvement to the WBC code, which has been used to model surface erosion, core plasma contamination, and tritium codeposition in many fusion design studies and experiments.
Czech Academy of Sciences Publication Activity Database
Izák, Pavel; Kárászová, Magda; Šim?ík, Miroslav; Friess, K.; Sedláková, Zuzana; R?ži?ka, Marek; Šolcová, Olga
Bratislava : AXIMA Graphics Design & Printing Services, 2014, s. 91 ISBN 978-80-89475-13-1. [International Conference of Slovak Society of Chemical Engineering /41./. Tatranské Matliare (SK), 26.05.2014-30.05.2014] R&D Projects: GA TA ?R TE01020080; GA ?R GA14-12695S Institutional support: RVO:67985858 Keywords : ionic liquid membrane * transport properties * trafer coefficients Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Volumetric mass transfer coefficients characterising VOC absorption in water/silicone oil mixtures
Dumont, Eric; Darracq, Guillaume; Couvert, Annabelle; Couriol, Catherine; Amrane, Abdeltif; Thomas, Diane; Andres, Yves; Le Cloirec, Pierre
2013-01-01
The physical absorption of three Volatile Organic Compounds (dimethyldisulphide (DMDS), dimethylsulphide (DMS) and toluene) in "water/silicone oil" systems at a constant flow rate for mixtures of different compositions (f = 0, 5, 10, 15, 20 and 100%) was investigated using a dynamic absorption method. The results indicate that silicone oil addition leads to a dramatic decrease in KLa which can be related to the change in the partition coefficient (Hmix). They confirm the results obtained for ...
Directory of Open Access Journals (Sweden)
Russell P. Rioux
2014-11-01
Full Text Available An experimental study has been conducted to examine the effects of macroscale, microscale, and nanoscale surface modifications in water pool boiling heat transfer and to determine the different heat transfer enhancing mechanisms at different scales. Nanostructured surfaces are created by acid etching, while microscale and macroscale structured surfaces are synthesized through a sintering process. Six structures are studied as individual and collectively integrated surfaces from nanoscale through microscale to macroscale: polished plain, flat nanostructured, flat porous, modulated porous, nanostructured flat porous, and nanostructured modulated porous. Boiling performance is measured in terms of critical heat flux (CHF and heat transfer coefficient (HTC. Both HTC and CHF have been greatly improved on all modified surfaces compared to the polished baseline. Hierarchical multiscale surfaces of integrated nanoscale, microscale, and macroscale structures have been proven to have the most significant improvements on HTC and CHF. The CHF and HTC of the hierarchical multiscale modulated porous surface have achieved the most significant improvements of 350% and 200% over the polished plain surface, respectively. Experimental results are compared to the predictions of a variety of theoretical models with an attempt to reveal the different heat transfer enhancing mechanisms at different scales. It is concluded that models for the structured surfaces at all scales need to be further developed to be able to have good quantitative predictions of CHFs on structured surfaces.
Exploring the potential energy surface for proton transfer in acetylacetone
International Nuclear Information System (INIS)
The portion of the potential energy surface (PES) of acetylacetone relevant for the intramolecular proton transfer reaction is studied using ab initio and DFT methods. The best estimate of the barrier governing proton transfer was found to be 3.4 kcal mol-1 at the MP4(FC)/6-311 + G(2d,2p)//MP2(FC)/6-311 + G(2d,2p) level of theory. Six stationary points on the PES were characterized as well as the reaction paths connecting these points. Special attention paid to the pathway of intramolecular proton transfer reveals that the internal rotation of the methyl group adjacent to the carbonyl group and the proton transfer reaction are consecutive processes
Nucleate pool-boiling heat transfer - I. Review of parametric effects of boiling surface
International Nuclear Information System (INIS)
The objective of this paper is to assess the state-of-the-art of heat transfer in nucleate pool-boiling. Therefore, the paper consists of two parts: part I reviews and examines the effects of major boiling surface parameters affecting nucleate-boiling heat transfer, and part II reviews and examines the existing prediction methods to calculate the nucleate pool-boiling heat transfer coefficient (HTC). A literature review of the parametric trends points out that the major parameters affecting the HTC under nucleate pool-boiling conditions are heat flux, saturation pressure, and thermophysical properties of a working fluid. Therefore, these effects on the HTC under nucleate pool-boiling conditions have been the most investigated and are quite well established. On the other hand, the effects of surface characteristics such as thermophysical properties of the material, dimensions, thickness, surface finish, microstructure, etc., still cannot be quantified, and further investigations are needed. Particular attention has to be paid to the characteristics of boiling surfaces. (author)
International Nuclear Information System (INIS)
Adsorption of radionuclides on soils and sediments is commonly quantified by distribution coefficients (Kd values). This paper examines the relationship between Kd values for uranium(VI) adsorption and the specific surface area (SSA) of geologic materials. We then investigate the potential applicability of normalising uranium (U) Kd measurements using the SSA, to produce 'Ka values' as a generic expression of the affinity of U for the surface. The data for U provide a reasonably coherent set of Ka values on various solid phases, both with and without ligands. The Ka representation provides a way of harmonising datasets obtained for materials having different specific surface areas, and accounting for the effects of ligands in different systems. In addition, this representation may assist in developing U sorption models for complex materials. However, a significant limitation of the Ka concept is that sorption of radionuclides at trace levels can be dominated by interactions with specific surface sites, whose abundances are not reflected by the SSA. Therefore, calculated Ka values should be interpreted cautiously.
International Nuclear Information System (INIS)
The diet-milk transfer coefficient, Fm (Bq L-1 output in milk divided by Bq d-1 intake to the animal) was studied for eight radionuclides that previously had been given little attention. The Fm values for cows and goats, respectively, were: 2.3 x 10(-5) and 1.5 x 10(-4) for /sup 99m/Tc, 1.4 x 10(-4) and 8.5 x 10(-4) for /sup 95m/Tc, 1.1 x 10(-2) for 99Tc (goats only); 1.7 x 10(-3) and 9 x 10(-3) for 99Mo; 4.8 x 10(-4) and 4.4 x 10(-3) for /sup 123m/Te; 4.8 x 10(-4) and 4.6 x 10(-3) for 133Ba; 5.5 x 10(-7) and 5.5 x 10(-6) for 95Zr; and 4.1 x 10(-7) and 6.4 x 10(-6) for 95Nb. The goat/cow transfer coefficient ratios for milk were approximately 10, but the goat/cow ratios for meat varied by three orders of magnitude
Directory of Open Access Journals (Sweden)
Kongdej LIMPAIBOON
2013-12-01
Full Text Available The objective of this research was to study the effects of process variables on the volumetric mass transfer coefficient of oxygen, KLa, in a stirred bioreactor using the static gassing-out method. In this study, various process conditions were chosen, including 3 parameters, namely, concentration of glucose in medium (10, 15 and 20 g/l, air flow rate (1, 1.25, 1.5 and 1.75 vvm, and agitation rate (300, 400, 500 and 600 rpm. From the results, it was found that the KLa increased with increasing air flow rate and/or speed of agitation, but decreased with increasing concentration of glucose in medium. The maximum KLa occurred when the concentration of glucose in medium was the least (10 g/l, with an air flow rate of 1.75 vvm, and an agitation rate of 600 rpm. Correlations have been developed for the estimation of volumetric mass transfer coefficients at various process conditions for medium with different glucose concentrations. The exponent values representing dependence of KLa on the process conditions were then compared with literature values.
Consideration of the loss of activity in the soil for large transfer coefficients in the food chain
International Nuclear Information System (INIS)
The studies have shown that in the case of large transfer coefficients there will result a considerable overestimation of the ingestion dose if nonradioactive depletion effects are neglected. This overestimation may, depending on nuclide, vegetation and transfer coefficient, amount to two orders of magnitude. There will result e.g. for the bone exposure of a grown-up person, caused by 90Sr taken up by the consumption of root vegetables, a dose overestimation up to a factor of 50. For the dose to the kidneys of adults by 137Cs through consumption of beef there will result an overestimation by a factor of up to 60. And for 129I there will be obtained an infant thyroid dose from the pasture-cow-milk pathway being too large by a factor of up to 100. In order to be able to cover these cases by a sufficiently generalized formalism, too, it appears necessary therefore to modify or extend the 'Allgemeine Berechnungsgrundlagen' (German reg. guide for evaluating the exposure from environmental contamination) in the manner proposed in the paper. (orig./HP) 891 HP/orig.- 892 MB
Scientific Electronic Library Online (English)
Araí A. Bernárdez, Pécora; Maria Regina, Parise.
2006-09-01
Full Text Available This work shows the experimental study of a continuous gas-solid fluidized bed with an immersed tube where cold water is heated by fluidized solid particles presenting inlet temperature from 450 to 700°C. Experiments were carried out in order to verify the influence of solid particle flow rate and d [...] istance between baffles immersed in a shallow fluidized bed. The solid material was 254µm diameter silica sand particles, fluidized by air in a 0.90m long and 0.15m wide heat exchanger. The measurements were taken at steady state conditions for solid mass flow rate from 10 to 100 kg/h, in a heat exchanger with the presence of 5 or 8 baffles. Bed temperature measurements along the length of the heat exchanger were experimentally obtained and heat balances for differential control volumes of the heat exchanger were made in order to obtain the axial profile of the bed-to-tube heat transfer coefficient. The results showed that heat transfer coefficient increases with the solid particle mass flow rate and with the presence of baffles, suggesting that these are important factors to be considered in the design of such heat exchanger.
Rajesh Ghosh* and Sounak Bhattacherjee
2013-01-01
An adequate supply of oxygen in aqueous solution becomes the focal point of interest when it comes to the growth and maintenance of most aerobic microbial and tissue cultures used for biochemical and pharmaceutical production. Unfortunately, oxygen mass transfer to the growth medium serves as a major growth limiting factor owing to it’s low solubility in aqueous solutions. (Approximately 10 ppm at ambient temperature and pressure). The reaction rate is such that as oxygen enters the liquid ph...
Evaluation of Heat and Mass Transfer Coefficients for R134a/DMF Bubble Absorber
M Suresh; Mani, A.
2011-01-01
The Vapour Absorption Refrigeration System (VARS) has generated renewed interest and is being viewed as one of the alternatives for vapour compression refrigeration due to its potential for waste heat utilization. To improve the efficiency of these systems, it is necessary to study heat and mass transfer processes in absorption system components. The absorber, one of the crucial components in VARS is considered for study. Experimental investigation is carried out to study heat and mass transf...
DEFF Research Database (Denmark)
Le Dreau, Jerome; Heiselberg, Per
2013-01-01
Night-time ventilation is a promising approach to reduce the energy needed for cooling buildings without reducing thermal comfort. Nevertheless actual building simulation tools have showed their limits in predicting accurately the efficiency of night-time ventilation, mainly due to inappropriate models for convection. In a full-scale test room, the heat transfer was investigated during 12 h of discharge by night-time ventilation. A total of 34 experiments have been performed, with different ventilation types (mixing and displacement), air change rates, temperature differences between the inlet air and the room, and floor emissivities. This extensive experimental study enabled a detailed analysis of the convective and radiative flow at the different surfaces of the room. The experimentally derived convective heat transfer coefficients (CHTC) have been compared to existing correlations. For mixing ventilation, existing correlations did not predict accurately the convective heat transfer at the ceiling due to differences in the experimental conditions. But the use of local parameters of the air flow showed interesting results to obtain more adaptive CHTC correlations. For displacement ventilation, the convective heat transfer was well predicted by existing correlations. Nevertheless the change of floor emissivity influenced the CHTC at the surface of interest.
A Survey of Ballistic Transfers to the Lunar Surface
Anderson, Rodney L.; Parker, Jeffrey S.
2011-01-01
In this study techniques are developed which allow an analysis of a range of different types of transfer trajectories from the Earth to the lunar surface. Trajectories ranging from those obtained using the invariant manifolds of unstable orbits to those derived from collision orbits are analyzed. These techniques allow the computation of trajectories encompassing low-energy trajectories as well as more direct transfers. The range of possible trajectory options is summarized, and a broad range of trajectories that exist as a result of the Sun's influence are computed and analyzed. The results are then classified by type, and trades between different measures of cost are discussed.
International Nuclear Information System (INIS)
In general sorption coefficients, Kd, cat ion exchange capacity, CEC, and BET surface areas are measured on crushed rock samples because it is very time consuming to measure Kd and CEC on larger rock pieces as it takes a long time for the sorbing species to penetrate into and equilibrate a large sample. Also conventional sample holders for BET measurements are too small to hold a large sample. We have manufactured large sample holders for BET measurements and modified the equipment so that it is possible to measure BET surface areas on samples with 50 mm diameter and up to 100 mm length. Results are presented for intact pieces and compared to results on crushed material from the same drillcore. For Kd and CEC measurements we have developed a technique and equipment by which ions can be made to rapidly intrude into and equilibrate the internal surfaces of the same size samples as mentioned above. The method is based on electro-migration where the sample is placed between two vessels one with an anode and other with a cathode. The electric potential gradient drives the ions into and through the sample very much faster than molecular diffusion does. With Cs as the sorbing ion a few weeks were sufficient to equilibrate the 50 mm long sample. In previous diffusion experiments it took more than a year to equilibrate a 15 mm thick sample. A special mixing technique eliminates the development of low and high pH in the electrode compartments. Kd high pH in the electrode compartments. Kd results from measurements on an intact drillcore are presented and comparison is made with results obtained on crushed material from the same bore core. The results from the sorption experiments are compared with the results from the BET surface area determinations in an attempt to evaluate the use of the BET surface area as a proxy for sorption behaviour. (orig.)
Quantum Oscillations, Thermoelectric Coefficients, and the Fermi Surface of Semimetallic WTe2.
Zhu, Zengwei; Lin, Xiao; Liu, Juan; Fauqué, Benoît; Tao, Qian; Yang, Chongli; Shi, Youguo; Behnia, Kamran
2015-05-01
We present a study of angle-resolved quantum oscillations of electric and thermoelectric transport coefficients in semimetallic WTe2, which has the particularity of displaying a large B(2) magnetoresistance. The Fermi surface consists of two pairs of electronlike and holelike pockets of equal volumes in a "Russian doll" structure. The carrier density, Fermi energy, mobility, and the mean-free path of the system are quantified. An additional frequency is observed above a threshold field and attributed to the magnetic breakdown across two orbits. In contrast to all other dilute metals, the Nernst signal remains linear in the magnetic field even in the high-field (?c??1) regime. Surprisingly, none of the pockets extend across the c axis of the first Brillouin zone, making the system a three-dimensional metal with moderate anisotropy in Fermi velocity, yet a large anisotropy in the mean-free path. PMID:25978245
Flow patterns and corresponding local heat transfer coefficients in a pulsating heat pipe
MAMELI, MAURO; MARENGO, MARCO; Khandekar, Sameer
2011-01-01
A Pulsating Heat Pipe (PHP) is a passive two-phase heat transfer device for handling moderate to high heat fluxes, typically suited for power electronics and similar applications. It usually consists of a meandering capillary tube, closed end-to-end in a loop, evacuated and then partially filled with a working fluid. The internal flow patterns in a PHP are a function of the applied heat flux. At low heat flux levels, an oscillating slug flow pattern is prevalent but once the heat power increa...
International Nuclear Information System (INIS)
Heat transfer is a crucial aspect for hot stamping process, the fully austenitized boron steel blank with temperature about 900°C is transferred to the tool, then formed rapidly and quenched in the cooled tool. The desired fully martensitic transformation will happen only if the cooling rate exceeds a critical value approximately 27 K/s. During such process, the heat transfer coefficient (abbreviated as HTC) between the tool and blank plays a decisive role for the variation of the blank temperature. In this work, a theoretical formula based on the joint-roughness model is presented to describe the law of HTC, which relies on the roughness, hardness, and other material parameters of the tool and blank. Moreover, a non-contact temperature measuring system based on the infrared thermal camera is built to catch the temperature change course, and then the HTC value is derived through the inverse analysis. Based on the theoretical and experimental results, the change rule of HTC especially its dependence on the process pressure will be discussed in detail
Directory of Open Access Journals (Sweden)
Ameel Mohammed Rahman Al-Mayah
2014-06-01
Full Text Available The study of oxygen mass transfer was conducted in a laboratory scale 5 liter stirred bioreactor equipped with one Rushton turbine impeller. The effects of superficial gas velocity, impeller speed, power input and liquid viscosity on the oxygen mass transfer were considered. Air/ water and air/CMC systems were used as a liquid media for this study. The concentration of CMC was ranging from 0.5 to 3 w/v. The experimental results show that volumetric oxygen mass transfer coefficient increases with the increase in the superficial gas velocity and impeller speed and decreases with increasing liquid viscosity. The experimental results of kla were correlated with a mathematical correlation describing the influences of the considered factors (the overall power input and the superficial gas velocity over the studied rages. The predicted kla values give acceptable results compared with the experimental values. The following correlations were obtained: Air/water system Air/CMC system (0.5w/v Air/CMC system (1w/v Air/CMC system (2w/v Air/CMC system (3w/v
Najeeb, Umair
This thesis experimentally investigates the enhancement of single-phase heat transfer, frictional loss and pressure drop characteristics in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for Pressurized Nuclear reactor. In this experimental investigation, the effect of the outer surface roughness of a simulated nuclear rod bundle was studied. The outer surface of a simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The angle of corrugation for each diamond was 45 degrees. The length of each side of a diamond block is 1 mm. The depth of each diamond block was 0.3 mm. The pitch of the pattern was 1.614 mm. The simulated fuel rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm and was placed in a test-section made of 38.1 mm inner diameter, wall thickness 6.35 mm aluminum pipe. The Simulated fuel rod was made of Nickel 200 and Inconel 625 materials. The fuel rod was connected to 10 KW DC power supply. The Inconel 625 material of the rod with an electrical resistance of 32.3 kO was used to generate heat inside the test-section. The heat energy dissipated from the Inconel tube due to the flow of electrical current flows into the working fluid across the rod at constant heat flux conditions. The DI water was employed as working fluid for this experimental investigation. The temperature and pressure readings for both smooth and rough regions of the fuel rod were recorded and compared later to find enhancement in heat transfer coefficient and increment in the pressure drops. Tests were conducted for Reynold's Numbers ranging from 10e4 to 10e5. Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer co-efficient enhancement recorded was 86% at Re = 4.18e5. It was also observed that the pressure drop and friction factor increased by 14.7% due to the increased surface roughness.
Matsuzaki, Ryosuke; Kamai, Kazuto; Seki, Ryosuke
2015-02-01
Intelligent tires equipped with sensors as well as the monitoring of the tire/road contact conditions are in demand for improving vehicle control and safety. With the aim of identifying the coefficient of friction of tire/road contact surfaces during driving, including during cornering, we develop an identification scheme for the coefficient of friction that involves estimation of the slip angle and applied force by using a single lightweight three-axis accelerometer attached on the inner surface of the tire. To validate the developed scheme, we conduct tire-rolling tests using an accelerometer-equipped tire with various slip angles on various types of road surfaces, including dry and wet surfaces. The results of these tests confirm that the estimated slip angle and applied force are reasonable. Furthermore, the identified coefficient of friction by the developed scheme agreed with that measured by standardized tests.
Infrared Low Temperature Turbine Vane Rough Surface Heat Transfer Measurements
Boyle, R. J.; Spuckler, C. M.; Lucci, B. L.; Camperchioli, W. P.
2000-01-01
Turbine vane heat transfer distributions obtained using an infrared camera technique are described. Infrared thermography was used because noncontact surface temperature measurements were desired. Surface temperatures were 80 C or less. Tests were conducted in a three vane linear cascade, with inlet pressures between 0.14 and 1.02 atm., and exit Mach numbers of 0.3, 0.7, and 0.9, for turbulence intensities of approximately 1 and 10%. Measurements were taken on the vane suction side, and on the pressure side leading edge region. The designs for both the vane and test facility are discussed. The approach used to account for conduction within the vane is described. Midspan heat transfer distributions are given for the range of test conditions.
International Nuclear Information System (INIS)
The diverter surface of the ITER Fusion Engineering Reactor is exposed to strong radiation locally up to 20MW/m2. We have proposed a diverter cooling system which consists of concave surfaces cooled by two-dimensional liquid jets. Experiments are conducted to investigate local heat transfer coefficient and critical heat flux on flat and concave surfaces under various cooling conditions. Based on photographic study, a critical heat flux model was derived by modifying a Haramura's model to take account of the subcooling effect. The proposed correlation based on this model was in good agreement with the experimental data. (author)
Anisotropic excitation transfer to acceptors randomly distributed on surfaces.
Kellerer, H; BLUMEN, A
1984-01-01
We presented exact expressions for the ensemble averaged decay of the excitation of a donor molecule due to the energy transfer via anisotropic dipolar interactions to acceptors distributed randomly on a surface. The disorder extended both over the positions of the acceptors and over the orientations of their transition dipoles with respect to that of the donor molecule. Several cases were considered explicitly (a) random orientations of the acceptors in space, with the donor being (a1) perpe...
Gas/surface heat transfer in spray deposition processes
International Nuclear Information System (INIS)
A numerical investigation of heat transfer dynamics between gas and solid surfaces during droplet spray impingement is presented. Aim of the work is to derive knowledge for control of spray deposition processes like spray painting or spray forming, analysing how the heat exchanged from the surface to the flowing gas is affected by the presence of impinging droplets. The investigation is carried on a macro- and a micro-scale, analysing velocity and temperature profiles close to a surface cooled by a spray on a scale of the whole spray and on a scale comparable to the droplet diameter, respectively. In the former case an Euler-Lagrange approach is used to reproduce the multiphase jet/spray for different nozzle geometries, gas conditions and droplets properties, as drop diameter and concentration. In the latter case, the gas flow close to the surface is studied during the collision of single and multiple droplets for different impact velocities superposed by different perpendicular gas boundary layer configurations. The 'volume of fluid' (VOF) technique is utilized for the determination of the transient shape of the gas-liquid interface during droplet impact. From the data of the numerical case studies, a quantitative consideration about the global increase of surface/gas heat transfer in impinging dilute sprays as a function of the number flux of particles approaching the wall is derived
Das, Sudev; Bhaumik, Swapan
2015-04-01
The influence of coating thickness and surface roughness on pool boiling heat transfer is experimentally studied over a range of surface roughness values with varied coating thickness with water at atmospheric pressure. Test surfaces used in this experiment are namely, untreated surface (Ra = 0.0899 µm), polished surface (Ra = 0.0493 µm), TiO2 nanoparticle coated surface with a roughness (Ra) ranging from 0.0338 to 0.289 µm. The surfaces were characterized with respect to contact angle, surface roughness and coating thickness. The contact angle, surface roughness and coating thickness were measured by sessile drop method, optical surface profiler and instrument thickness monitor respectively. Heat fluxes observed ranged from 52.63 to 144.73 W/cm2. Different trends were observed in the Heat Transfer Coefficient (HTC) with respect to the surface roughness and coating thickness values on the same set of heat flux. The HTC was found to increase with increasing the roughness values for untreated and polish surface but nanoparticle coated surfaces displayed different trend in HTCs. The HTC was found to increase with increasing coating thickness with all wall superheat.
Improvement of Reactor Fuel Element Heat Transfer by Surface Roughness
International Nuclear Information System (INIS)
In heat exchangers with a limited surface temperature such as reactor fuel elements, rough heat transfer surfaces may give lower pumping power than smooth. To obtain data for choice of the most advantageous roughness for the superheater elements in the Marviken reactor, measurements were made of heat transfer and pressure drop in an annular channel with a smooth or rough test rod in a smooth adiabatic shroud. 24 different roughness geometries were tested. The results were transformed to rod cluster geometry by the method of W B Hall, and correlated by the friction and heat transfer similarity laws as suggested by D F Dipprey and R H Sabersky with RMS errors of 12.5 % in the friction factor and 8.1 % in the Stanton number. The relation between the Stanton number and the friction factor could be described by a relation of the type suggested by W Nunner, with a mean error of 3.1 % and an RMS error of 11.6 %. Application of the results to fuel element calculations is discussed, and the great gains in economy which can be obtained with rough surfaces are demonstrated by two examples
International Nuclear Information System (INIS)
The main correlations likely to be suitable for describing heat transfers between the fluid and wall during decompression are analyzed. The most important experimental work on the boiling crisis in the transient regime is presented. Experimental studies are then treated. The test installation (OMEGA experiment), the instumentation used and the experiments realized are described. The purpose of these experiments was to establish heat exchange laws for decompression conditions. Local and instantaneous exchange coefficients were determined in a heated test section together with the thermohydraulic parameters of the flow. The methods used to investigate the measurements made and to analyze their validity are described. Finally, the test results are presented and discussed. It is shown that under certain conditions, the boiling crisis can be determined with a permanent regime correlation. An attempt is made to establish a correlation for the transition boiling zone from these results. A test reconstitution calculation based on a two-fluid model is presented
Estimation of site specific transfer coefficient from feed to cow milk for 137Cs at Kaiga region
International Nuclear Information System (INIS)
Site specific transfer coefficient from feed to cow milk (Fm), for 137Cs at Kaiga environment determined over a period of ten years (2000-2009) is presented in this paper. 137Cs concentrations reported in this paper are of fallout origin. Fm values ranged from 3.47E-03 to 1.38E-02 d. L-1 with geometric mean value is 6.4E-03 d. L-1. These values are comparable with IAEA value for 137Cs (4.6E-03). The site-specific parameter is useful in estimation of dose to man due to ingestion of milk in an accidental condition. The ingestion dose from fallout 137Cs through milk intake for adult and child is also estimated. (author)
Polarization transfer coefficients for 3He(p,p)3He elastic scattering below 11 MeV
International Nuclear Information System (INIS)
The polarization transfer coefficients Ksub(x)sup(x'), Ksub(Z)sup(x'), and Ksub(y)sup(y') for 3He(p,p) elastic scattering (Wolfenstein parameters R, A, and D) were measured at incident energies of 6.82, 8.82 and 10.77 MeV at up to four angles. Polarized protons scattered by a liquid nitrogen cooled 3He cell were focussed by a magnetic quadrupole lens into a high pressure polarimeter filled with 4He. The measured values compared satisfactorily with values calculated from previously determined phase shifts, from an R-matrix analysis of p-3He scattering and from microscopic calculations based on an approximate nucleon-nucleon potential. (Auth.)
Directory of Open Access Journals (Sweden)
Armando Alvis
2010-01-01
Full Text Available Se describe un procedimiento de evaluación del coeficiente de transferencia de calor en operaciones industriales. Se presenta un modelo matemático sencillo de determinación del coeficiente convectivo de transferencia de calor usando el software DCAL (Determinación de Coeficiente de Transferencia de Calor durante un Calentamiento. Para validar el modelo se usaron datos experimentales de muestras procesadas por tratamiento térmico, utilizando diferentes temperaturas y tiempos de proceso. Los datos experimentales fueron procesados automáticamente por el software, para la generación de gráficas y determinación de un coeficiente de transferencia de calor optimizado. Se concluye que la metodología descrita sirve para el cálculo del coeficiente convectivo cuando no hay resistencia interna a la transferencia de calor.The evaluation of the heat transfer coefficient for its use in industrial operations is described. A simple mathematical model to determine the heat transfer convective coefficient using the DCAL software (Determination of Heat Transfer Coefficient during a Heating. To valídate the model experimental data of samples processed by thermal treatment using different temperatures and process time were used. The experimental data was automatically processed by the software, to genérate graphs and to determine an optimum heat transfer coefficient. The main conclusión was that the methodology described is useful to the compute of convective coefficient when there is no inside heat transfer resistance.
Scientific Electronic Library Online (English)
Armando, Alvis; Isaac, Caicedo; Pierre, Peña.
Full Text Available Se describe un procedimiento de evaluación del coeficiente de transferencia de calor en operaciones industriales. Se presenta un modelo matemático sencillo de determinación del coeficiente convectivo de transferencia de calor usando el software DCAL (Determinación de Coeficiente de Transferencia de [...] Calor durante un Calentamiento). Para validar el modelo se usaron datos experimentales de muestras procesadas por tratamiento térmico, utilizando diferentes temperaturas y tiempos de proceso. Los datos experimentales fueron procesados automáticamente por el software, para la generación de gráficas y determinación de un coeficiente de transferencia de calor optimizado. Se concluye que la metodología descrita sirve para el cálculo del coeficiente convectivo cuando no hay resistencia interna a la transferencia de calor. Abstract in english The evaluation of the heat transfer coefficient for its use in industrial operations is described. A simple mathematical model to determine the heat transfer convective coefficient using the DCAL software (Determination of Heat Transfer Coefficient during a Heating). To valídate the model experiment [...] al data of samples processed by thermal treatment using different temperatures and process time were used. The experimental data was automatically processed by the software, to genérate graphs and to determine an optimum heat transfer coefficient. The main conclusión was that the methodology described is useful to the compute of convective coefficient when there is no inside heat transfer resistance.
Shitzer, Avraham
2006-03-01
The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published "new" WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a "gold standard" for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized. PMID:16397760
Energy Technology Data Exchange (ETDEWEB)
Rozati, Ali [Mechanical Engineering Department, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail code 0238, Blacksburg, VA 24061 (United States); Tafti, Danesh K. [Mechanical Engineering Department, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail code 0238, Blacksburg, VA 24061 (United States)], E-mail: dtafti@vt.edu
2008-02-15
A numerical investigation is conducted to study leading edge film cooling with large eddy simulation (LES). The domain geometry is adopted from an experimental setup of [Ekkad, S.V., Han, J.C., Du, H., 1998. Detailed film cooling measurement on a cylindrical leading edge model: Effect of free-stream turbulence and coolant density. Journal of Turbomachinery 120, 799-807.] where turbine blade leading edge is represented by a semi-cylindrical blunt body with compound angle of injection. At blowing ratio of 0.4 and coolant to mainstream density ratio of unity, a laminar constant velocity and fully-turbulent coolant jet are studied. In both cases, the results show the existence of an asymmetric counter-rotating vortex pair in the immediate wake of the coolant jet. In addition to these primary structures, vortex tubes on the windward side of the jet are convected downstream over and to the aft- and fore-side of the counter-rotating vortex pair. All these structures play a role in the mixing of mainstream fluid with the coolant. The fully-turbulent coolant jet increases mixing with the mainstream in the outer shear layer but does not directly influence the flow dynamics in the turbulent boundary layer which forms within two coolant hole diameters of injection. As a result, the turbulent jet decreases adiabatic effectiveness but does not have a substantial effect on the heat transfer coefficient. The span-wise averaged adiabatic effectiveness agrees well with experiments for a turbulent coolant jet, without which the calculated effectiveness is over-predicted. On the other hand, the heat transfer coefficient which is only a function of near wall turbulence, shows good agreement with experiments for both coolant jet inlet conditions.
International Nuclear Information System (INIS)
When performing transient analysis with license codes of Nuclear Power Plants, the reactor core is modelled using a few representative fuel elements of large regions containing many fuel bundles. The properties of these fuel bundles must be averaged in order to obtain the thermal-hydraulics characteristics of the typical fuel bundle belonging to that region. One of the most important magnitudes that must be averaged is the heat transfer coefficient of the gap hgap, which can have large variations from one fuel bundles to others, especially if they belong to different fuel vendors. This paper presents a methodology to obtain the axial variation of the average heat transfer coefficient of different fuel bundles. To check the consistency of the proposed averaging methodology, especially for LOCA analysis applications, we have performed calculations of the peak clad temperature evolution, and the fuel temperature evolution, for the core loaded with two different fuel types that have different axial hgap values, and we have compared the results of the following cases: I) The core is loaded with all fuel elements of type 1. II) The core is loaded with all fuel elements of type 2. III) The core is loaded with an average fuel channel with an hgap value computed with the new methodology, that we call harmonic averaging. IV) The core is loaded with an average fuel channel with an hgap value computed by averaging with the arithmetic average. The evolution of the peak clad temperature and the fuel temperature with time obtained with the harmonic averaging shows an evolution that lies between the temperatures obtained with both fuel types i.e. cases I and II, and that is therefore more consistent than the arithmetic averaging, that gives a temperature evolution closer to the less conservative case. (authors)
Energy Technology Data Exchange (ETDEWEB)
Baeza, A. [Department of Physics, Faculty of Veterinary, University of Extremadura, Avda. Universidad s/n, Caceres 10071 (Spain)]. E-mail: ymiralle@unex.es; Guillen, J. [Department of Physics, Faculty of Veterinary, University of Extremadura, Avda. Universidad s/n, Caceres 10071 (Spain); Bernedo, J.M. [Department of Industrial Chemistry, University of Alcala, Alcala de Henares, Madrid 28871 (Spain)
2005-07-01
Soil-fungus transfer coefficients are usually defined as the ratio between the content of the fruiting bodies and that of the soil. Since, however, the methodology of how to determine the soil content is not firmly established, there exist a variety of definitions in the literature. We analyzed the {sup 137}Cs, {sup 90}Sr, {sup 40}K, and {sup 226}Ra content of mushroom and soil samples from two pine-wood ecosystems in Spain. The location of the mycelium in the soil profiles of these ecosystems was determined by means of the ergosterol concentration. The results showed the mycelium to generally be localized in the surface layer of soil (0-5 cm). We also carried out a speciation procedure for this layer of soil to determine the different degrees of association of the radionuclides in the soil. The results led us to propose some variations to the traditional definition used in quantifying radionuclide transfer. With these modifications, we were able to analyze Cs-K competition in several species of mycorrhizal and saprophytic fungi.
Bolton, J. S.; Gold, E.
1984-03-01
A free field transient technique is described in which cepstral analysis is used to remove the restriction that the direct and reflected signals be nonoverlapping, thus allowing in situ measurements to be made with a single microphone in one position. To facilitate the development of analysis and extraction software and general experimental technique, the acoustical reflector was simulated by a passive filter network. The approach chosen for the determination of H(omega) is a simple extraction of h(t) from the power cepstrum. Good quality cepstra in which the reflector response appears as an isolated feature are produced by careful selection of the incident signal, anti-aliasing filter, sampling frequency, and echo delay in relation to the total sampling time, and by the use of signal processing techniques such as time domain averaging, recursive filtering in the cepstral domain, and zero padding. Results are presented for a flat transfer function; RC lowpass, bandpass, and highpass circuits; and LRC lowpass, bandpass, and highpass circuits.
Free surface deformation and heat transfer by thermocapillary convection
Fuhrmann, Eckart; Dreyer, Michael; Basting, Steffen; Bänsch, Eberhard
2015-06-01
Knowing the location of the free liquid/gas surface and the heat transfer from the wall towards the fluid is of paramount importance in the design and the optimization of cryogenic upper stage tanks for launchers with ballistic phases, where residual accelerations are smaller by up to four orders of magnitude compared to the gravity acceleration on earth. This changes the driving forces drastically: free surfaces become capillary dominated and natural or free convection is replaced by thermocapillary convection if a non-condensable gas is present. In this paper we report on a sounding rocket experiment that provided data of a liquid free surface with a nonisothermal boundary condition, i.e. a preheated test cell was filled with a cold but storable liquid in low gravity. The corresponding thermocapillary convection (driven by the temperature dependence of the surface tension) created a velocity field directed away from the hot wall towards the colder liquid and then in turn back at the bottom towards the wall. A deformation of the free surface resulting in an apparent contact angle rather different from the microscopic one could be observed. The thermocapillary flow convected the heat from the wall to the liquid and increased the heat transfer compared to pure conduction significantly. The paper presents results of the apparent contact angle as a function of the dimensionless numbers (Weber-Marangoni and Reynolds-Marangoni number) as well as heat transfer data in the form of a Nusselt number. Experimental results are complemented by corresponding numerical simulations with the commercial software Flow3D and the inhouse code Navier.
Improvement of heat transfer by the use of corrugated surfaces
International Nuclear Information System (INIS)
This experimental work is designed to determine the friction coefficient and the Margoulis number of internally or externally corrugated cans cooled by air or CO2 under forced convection, when the Reynolds' number is between 1.5 * 104 and 3.5 * 106 Different corrugation profiles have been examined; they are made up of variously shaped threading, of rings, of transverse fins, of very small 'herring-bone fins, of undulations. Two types of test have been carried out: 1. tests in annular spaces using CO2 or air, where the gas circulates between an electrically heated corrugated nucleus having a constant flux and a smooth exterior channel. 2. tests on internally corrugated tubes heated by an external water current and cooled by an internal current of pressurized CO2. The first type of test requires probe-measurement of the speeds and the temperatures in the fluid in order to obtain a friction coefficient and a Margoulis' number which are characteristic of the corrugated surface. These coefficients, on the other hand, are given directly by the second, type of test. This work shows the role and the importance of the various geometric and aerodynamic parameters such as relative roughness, the reduced pitch (ratio of the pitches at the height of the corrugation) and the Reynolds' number. (authors)
Influence of the surface drag coefficient (young waves) on the current structure of the Berre lagoon
Alekseenko, Elena; Roux, Bernard; Kharif, Christian; Sukhinov, Alexander; Kotarba, Richard; Fougere, Dominique; Chen, Paul Gang
2013-04-01
Due to the shallowness, currents and hydrodynamics of Berre lagoon (South of France) are closely conditioned by the bottom topography, and wind affects the entire water column, as for many other Mediterranean lagoons (Perez-Ruzafa, 2011). Wind stress, which is caused by moving atmospheric disturbance, is known to have a major influence in lagoon water circulation. According to the numerical simulation for the main directions of the wind: N-NW, S-SE and W (wind speed of 80 km/h) it is observed that the current is maximal alongshore in the wind direction; the bottom nearshore current being larger in shallower area. This fact is coherent with fundamental principle of wind-driven flows in closed or partially closed basins which states that in shallow water the dominant force balance is between surface wind stress and bottom friction, yielding a current in the direction of the wind (Mathieu et al, 2002, Hunter and Hearn, 1987; Hearn and Hunter,1990). A uniform wind stress applied at the surface of a basin of variable depth sets up a circulation pattern characterized by relatively strong barotropic coastal currents in the direction of the wind, with return flow occurring over the deeper regions (Csanady, 1967; Csanady, 1971). One of the key parameters characterizing the wind stress formulation is a surface drag coefficient (Cds). Thus, an effect of a surface drag coefficient, in the range 0.0016 - 0.0032, will be analyzed in this work. The value of surface drag coefficient Cds = 0.0016 used in our previous studies (Alekseenko et al., 2012), would correspond to mature waves (open sea). But, in the case of semi-closed lagoonal ecosystem, it would be more appropriate to consider "young waves" mechanism. A dependency of this coefficient in terms of the wind speed is given by Young (1999) in both cases of mature waves and young waves. For "young waves" generated at a wind speed of 80 km/h, Cds = 0.0032. So, the influence of Cds on the vertical profile of the velocity in the water column is analyzed in the range 0.0016 - 0.0032. For the three main wind directions considered in this work, for a wind speed of 80 km/h, the complex current structure of the Berre lagoon is analysed. In the nearshore zones, strong alongshore downwind currents are generated, reaching values of the order of 1m/s (up to 1.5 m/s) at the free surface, and 0.5 - 0.6 m/s at the bottom. References Alekseenko E., B. Roux, A. Sukhinov, R. Kotarba, D. Fougere. Coastal hydrodynamics in a windy lagoon; submitted to Computers and Fluids, oct. 2012 Csanady G. T.: Large-scale motion in the Great Lakes, Journal of Geophysical Research, 72(16), 4151-4161, 1967. Csanady G. T. : Baroclinic boundary currents and long edge-waves in basins with sloping shores. J. Physical Oceanography 1(2):92-104, 1971. Hunter, J.R. and Hearn, C.J.: Lateral and vertical variations in the wind-driven circulations in long, shallow lakes, Journal of Geophysical Research, 92 (C12), 1987. Hearn, C.J. and Hunter, J.R.: A note on the equivalence of some two- and three-dimensional models of wind-driven barotropic flow in shallow seas, Applied Mathematical Modelling, 14, 553-556, 1990. Mathieu P.P., Deleersnijder E., Cushman-Roisin B., Beckers J.M. and Bolding K.: The role of topography in small well-mixed bays, with application to the lagoon of Mururoa. Continental Shelf research, 22(9), 1379-1395, 2002. A. Pérez-Ruzafa, C. Marcos, I.M. Pérez-Ruzafa (2011). Mediterranean coastal lagoons in an ecosystem and aquatic resources management context//Physics and Chemistry of the Earth, Parts A/B/C, Volume 36, Issues 5-6, 2011, Pages 160-166 Young I.R., Wind generated ocean waves. Ocean Engineering Series Editors. Elsevier, 1999, ISBN: 0-08-043317-0.
Charge transfer and electronic relaxation in ion-surface scattering
International Nuclear Information System (INIS)
The purpose of this work is to investigate theoretically a widely studied process at the gas-surface interface, namely the transfer of one electron from a surface to an impinging ion and the subsequent electronic relaxation of the possibly excited neutralized atom. The theoretical techniques used are reviewed in Chapter 1, where the concepts of density matrix theory and field theory strictly related to the rest of the work are presented. The necessity of using a density matrix to describe the quantum state of a system that interacts with another unobserved system, is stressed in Chapter 1.A. In Chapter 1.B., after reviewing how the quantization procedure is performed for both a classical particle and a classical field, second quantization is presented as the quantum theory that correctly describes a system of many particles whose total number is not conserved. In Chapter 2, second quantization techniques are applied to ion-neutralization at surfaces. The experimental and theoretical state of the art is reviewed in Chapter 2.A., while in Chapter 2.B. is presented a perturbative treatment of the Fano-Anderson effective potential to model the charge transfer process. The theory is applied to proton neutralization at alkali-halide surfaces, which are systems for which the perturbative expansion converges quickly. The qualitative behavior of the calculated dependence of the neutralization probability on the ion collision velocity is found to be in agreement with experimental measurements
Pongcharoenkiat, Nongnuch; Narsimhan, Ganesan; Lyons, Robert T; Hem, Stanley L
2002-02-01
Methylparaben (MP) was the model solute used to study the effect of surface charge on the rate of degradation in oil-in-water emulsions. The surface charge was varied by adding small amounts of phosphatidylglycerol (anionic) or stearylamine (cationic) to a standard intravenous lipid emulsion stabilized by egg phospholipid. The rates of hydrolysis at pH 8.0 in the water phase, oil phase, interface, and aqueous micellar phase were determined by application of a four-phase kinetic model. The rate of hydrolysis in the aqueous phase was dependent on the zeta potential. This was attributed to the effect of surface charge on the pH of the microenvironment of the oil drops through the phenomena known as surface acidity. MP in the aqueous phase hydrolyzed at a rate associated with the pH of the microenvironment, not the pH of the bulk. The effect of the partition coefficient of the solute was studied by substituting ethylparaben (EP), propylparaben (PP), and butylparaben (BP) for MP in the emulsions used to study the effect of surface charge. The rate of hydrolysis was inversely related to the partition coefficient. The effect of surface charge on the rate of hydrolysis was evident in the emulsions containing MP and EP. Partitioning had the greatest effect on the emulsions containing PP and BP. In general, the effect of surface charge predominated when the partition coefficient was small. The partition coefficient had a greater effect than surface charge when the partition coefficient was large. PMID:11835213
Information Exchange via Surface Modified Resonance Energy Transfer
Boström, Mathias; Huang, Dan; Ninham, Barry W; Sernelius, Bo E
2013-01-01
The theory is presented for resonance interaction between two atoms in an excited configuration: one atom, the "receptor" of information (i.e. energy), adsorbed on a phospholipid surface and the other atom, the "emitter" of information (i.e. energy), a long distance away. The dielectric function for a specific phospholipid membrane is obtained from density functional theory calculations. We present numerical results comparing the range and magnitude of non-specific Casimir-Polder interactions with the much more long-ranged, and highly specific, resonance interaction. A study of the resonance interaction with one or both atoms adsorbed on a phospholipid membrane surface reveals a possibility to have a cross over from attraction to repulsion or from repulsion to attraction at separations between receptor and emitter atoms exceeding several hundred {\\AA}ngstr\\"oms. The energy transfer and the observed transitions in the sign of the interaction energies near surfaces provide potential new ways to start recognitio...
Ali Abdul-Rahman N. Jasim
2009-01-01
The bubble columns are widely used as a two or three phase reactor in industrial chemical process such as absorption, biochemical reactions, coal liquefaction, etc. To design such a column, two main parameters should be taken in consideration, the gas hold-up ( ), and the liquid phase mass transfer coefficient KLa. The study includes the effect of gas velocity and the addition of alcohols on gas hold-up and mass transfer coefficient in bubble column with draught tube when the length of the co...
Scientific Electronic Library Online (English)
Diego F., Tirado; Diofanor, Acevedo; Plinio, Puello.
Full Text Available Se describe la elaboración de un software para la determinación de propiedades termofísicas y coeficientes convectivos de transferencia de calor en alimentos y que se ha denominado CTCIA (Coeficientes de Transferencia de Calor en Ingeniería de Alimentos). Para validar los modelos incluidos en el sof [...] tware, se usaron datos experimentales de tilapia frescas y procesadas, a diferentes temperaturas y tiempos de proceso. Los datos experimentales fueron procesados automáticamente por el software, generando las propiedades termofísicas y el coeficiente de transferencia de calor. Se concluye que la metodología descrita sirve para el cálculo de propiedades termofísicas y el coeficiente convectivo cuando no hay resistencia interna a la transferencia de calor. Abstract in english The development of a computer program for the determination of thermophysical properties and convective heat transfer coefficients in foods is presented. The software has been named CTCIA (Heat Transfer Coefficients in Food Engineering). To validate the models included in the software, experimental [...] data of fresh and processed tilapia at different temperatures and process times. The experimental data were processed automatically by the software, thereby generating values for the thermophysical properties and the heat transfer coefficient. In is concluded that the method described in this study is useful for calculating the thermophysical properties and the convective heat transfer coefficient when there is no internal resistance to heat transfer.
International Nuclear Information System (INIS)
Measurements of soil-to-plant transfer of 134Cs, 85Sr and 65Zn from two tropical red earth soils ('Blain' and 'Tippera') to sorghum and mung crops have been undertaken in the north of Australia. The aim of the study was to identify factors that control bioaccumulation of these radionuclides in tropical regions, for which few previous data are available. Batch sorption experiments were conducted to determine the distribution coefficient (Kd) of the selected radionuclides at pH values similar to natural pH values, which ranged from about 5.5 to 6.7. In addition, Kd values were obtained at one pH unit above and below the soil-water equilibrium pH values to determine the effect of pH. The adsorption of Cs showed no pH dependence, but the Kd values for the Tippera soils (2300-4100 ml/g) exceeded those for the Blain soils (800-1200 ml/g) at equilibrium pH. This was related to the greater clay content of the Tippera soil. Both Sr and Zn were more strongly adsorbed at higher pH values, but the Kd values showed less dependence on the soil type. Strontium Kds were 30-60 ml/g whilst Zn ranged from 160 to 1630 ml/g for the two soils at equilibrium pH. With the possible exception of Sr, there was no evidence for downward movement of radionuclides through the soils during the course of the growing season. There was some evidence of surface movement of labelled soil particles. Soil-to-plant transbelled soil particles. Soil-to-plant transfer factors varied slightly between the soils. The average results for sorghum were 0.1-0.3 g/g for Cs, 0.4-0.8 g/g for Sr and 18-26 g/g for Zn (dry weight) with the initial values relating to Blain and the following values to Tippera. Similar values were observed for the mung bean samples. The transfer factors for Cs and Sr were not substantially different from the typical values observed in temperate studies. However, Zn transfer factors for plants grown on both these tropical soils were greater than for soils in temperate climates (by more than an order of magnitude). This may be related to trace nutrient deficiency and/or the growth of fungal populations in these soils. The results indicate that transfer factors depend on climatic region together with soil type and chemistry and underline the value of specific bioaccumulation data for radionuclides in tropical soils
Chung, Juyeon; Hagishima, Aya; Ikegaya, Naoki; Tanimoto, Jun
2015-07-01
We report the result of a wind-tunnel experiment to measure the scalar transfer efficiency of three types of surfaces, wet street surfaces of cube arrays, wet smooth surfaces with dry patches, and fully wet smooth surfaces, to examine the effects of roughness topography and scalar source allocation. Scalar transfer coefficients defined by the source area {C}_{E wet} for an underlying wet street surface of dry block arrays show a convex trend against the block density ? _p . Comparison with past data, and results for wet smooth surfaces including dry patches, reveal that the positive peak of {C}_{E wet} with increasing ? _p is caused by reduced horizontal advection due to block roughness and enhanced evaporation due to a heterogeneous scalar source distribution. In contrast, scalar transfer coefficients defined by a lot-area including wet and dry areas {C}_{E lot} for smooth surfaces with dry patches indicate enhanced evaporation compared to the fully wet smooth surface (the oasis effect) for all three conditions of dry plan-area ratio up to 31 %. Relationships between the local Sherwood and Reynolds numbers derived from experimental data suggest that attenuation of {C}_{E wet} for a wet street of cube arrays against streamwise distance is weaker than for a wet smooth surface because of canopy flow around the blocks. Relevant parameters of ratio of roughness length for momentum to scalar {B}^{-1} were calculated from observational data. The result implies that {B}^{-1} possibly increases with block roughness, and decreases with the partitioning of the scalar boundary layer because of dry patches.
International Nuclear Information System (INIS)
In nuclear fuel fabrication facilities, fine particles of UO2 deposit on the surfaces of walls, equipment, ventilation filters, etc. which may finally become uranium-bearing wastes when these items are removed or replaced. Radon is one progeny of uranium and emanates from those wastes. It is very difficult to experimentally simulate such radon emanation, which means it is difficult to measure radon emanation co-efficients for those wastes. The present paper theoretically calculated radon emanation coefficients for them assuming UO2 particles remain on the surfaces of such wastes in the distant future when radon is formed in these particles. The calculated average radon emanation coefficient was 0.03. With more complete information about particle size distribution from fuel manufactures, this method would be able to provide better predictions. (author)
Three Dimensional Surface Topography Using LCD Pattern Transfer Method
Gatabi, Javad R.; Geerts, Wilhelmus; Aaron, Bryant; Tamir, Dan; Pandey, R. K.
2012-03-01
Laser lithography on curved surfaces has recently been researched due to its applicability in production processes for devices that combine integrated optical, mechanical, magnetic, and/or electronic technologies. Several laser lithography methods have been reported for pattern transfer to convex and cylindrical surfaces, but there is not a general methodology for arbitrary 3D surface lithography. This project implements an optical method for laser lithography on arbitrary 3D surfaces. An illumination pattern generated by a transparent LCD is projected through an optical microscope on top of a 3D surface and recorded by a camera. The focus quality and the distortion of the observed image depend on the local topography of the sample. The effect of the local sample topography on the projected pattern is theoretically investigated using Zemax ray-tracing software. Analysis are made for amplitude and phase modulation LCDs with different resolutions and compared with preliminary experimental results. The authors acknowledge financial support from NSF through an MRI-grant (grant: 0923506).
Nucleate Boiling Heat Transfer of Nanofluids with Carbon Nanotubes on Plain and Low Fin Surfaces
Energy Technology Data Exchange (ETDEWEB)
Park, Ki Jung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Jung, Dongsoo [Inha Univ., Incheon (Korea, Republic of)
2013-10-15
Nuclear power generation is being discussed in many countries as an alternative method to solving the world's energy crisis. For the safe operation of nuclear power plants, ways for increasing the critical heat flux (CHF) related to a loss of coolant accident are being investigated. In the event that the local heat flux exceeds the CHF, there is an abrupt shift in the boiling curve such that the nucleate boiling ceases and transition boiling and ultimately film boiling occur, finally resulting in a physical break down of the surface. Therefore, it is essential to maximize the CHF for the protection of nuclear power plants with maximum system performance. For the past decade, as a lot of research has been carried out for an improvement of the boiling heat transfer coefficients (HTCs) and CHF, new methods employing nano particles have been proposed. The objectives of this study are to measure the pool boiling HTCs of the water without and with carbon nanotubes (CNTs) on plain and low fin surfaces up to the CHF, and to analyze the effect of CNTs on both nucleate boiling HTCs and CHF. Pool boiling HTCs on all surfaces tested in water without and with CNTs increased as the heat flux increased, which is a typical trend in the pool boiling of pure fluids. For nanofluid with CNTs on low fin surfaces, the surface geometry and nano particles produced a double effect of increasing the CHFs.
International Nuclear Information System (INIS)
Various methods are available to enhance heat exchanger performance with evaporative cooling. In this study, evaporative mist precooling, deluge cooling, and combined cooling schemes are examined experimentally and compared to model predictions. A flexible model of a compact, finned-tube heat exchanger with a wetted surface is developed by applying the governing conservation and rate equations and invoking the heat and mass transfer analogy. The model is applicable for dry, partially wet, or fully wet surface conditions and capable of predicting local heat/mass transfer, wetness condition, and pressure drop of the heat exchanger. Experimental data are obtained from wind tunnel experiments using a louver-fin flat-tube heat exchanger with single-phase tube-side flow. Total capacity, pressure drop, and water drainage behavior under various water usage rates and air face velocities are analyzed and compared to data for dry-surface conditions. A heat exchanger partitioning method for evaporative cooling is introduced to study partially wet surface conditions, as part of a consistent and general method for interpreting wet-surface performance data. The heat exchanger is partitioned into dry and wet portions by introducing a wet surface factor. For the wet part, the enthalpy potential method is used to determine the air-side sensible heat transfer coefficient. Thermal and hydraulic performance is compared to empirical correlations. Total capacity predictions from the model agree with the experimental results with an average deviation of 12.6%. The model is also exercised for four water augmentation schemes; results support operating under a combined mist precooling and deluge cooling scheme. -- Highlights: • A new spray-cooled heat exchanger model is presented and is validated with data. • Heat duty is shown to be asymptotic with spray flow rate. • Meaningful heat transfer coefficients for partially wet conditions are obtained. • Colburn jwet is lower than jdry but no significant change in f was observed. • Simulations suggest using combined precooling and deluge cooling scheme
Xue, Chao-Hua; Guo, Xiao-Jing; Ma, Jian-Zhong; Jia, Shun-Tian
2015-04-22
Superhydrophobic surfaces were fabricated via surface-initiated atom transfer radical polymerization of fluorinated methacrylates on poly(ethylene terephthalate) (PET) fabrics. The hydrophobicity of the PET fabric was systematically tunable by controlling the polymerization time. The obtained superhydrophobic fabrics showed excellent chemical robustness even after exposure to different chemicals, such as acid, base, salt, acetone, and toluene. Importantly, the fabrics maintained superhydrophobicity after 2500 abrasion cycles, 100 laundering cycles, and long time exposure to UV irradiation. Also, the surface of the superhydrophobic fabrics showed excellent antifouling properties. PMID:25832484
International Nuclear Information System (INIS)
A study of the heat transfer processes between an over-bed burner flame and a fluidized bed during start-up as been conducted. Owing to the difficulty of estimating the flame to bed convection coefficient in an industrial boiler, convection coefficients were determined using a laboratory bench scale unit. Such convection heat transfer coefficients are obtained for 3 kg, 4 kg and 5.5 kg initial bed inventories by combining measured temperatures and flow rates with a mathematical model representing the complex energy exchange in the system. Results show that the height of the fluidized bed and its distance to the flame are an important factor in the overall heat transfer process, both by convection and radiation. For 5.5 kg, 4 kg and 3 kg initial bed inventories, the convection coefficients obtained, at the end of start-up, are 180 ± 30 W/m2 K, 150 ± 20 W/m2 K and 95 ± 10 W/m2 K respectively. The determined convection coefficients can be utilized in the future as guides in the design of start-up systems for BFB boilers. The energy analysis performed also identified the major sources of heat losses in the bubbling fluidized bed.
Heat transfer augmentation due to surface radiative exchange effect of internal fins in an annulus
International Nuclear Information System (INIS)
Heat transfer augmentation due to surface radiation in an annulus with fins was investigated both theoretically and experimentally for fully developed laminar flow. The system considered in the present study was an array of axially internal and straight fins attached to the outer tube wall. Analytical solutions were given for 4, 8, 16, 24, 32 fins and for the ratios of the fin height to the passage clearance, 0, 0.2, 0.4, 0.5, 0.6, 0.8. The experiments were performed with air as the working fluid for radius ratio of 1.45, 16 fins and for Reynolds numbers ranging from 500 to 2000. The numerically predicted results of the convective/radiative heat transfer for the present case were in good agreement with the experimental data. It was found that the heat transfer augmentation coefficient attained a maximum value of 1.45 for 32 fins and for a dimensionless fin height of 0.65
Directory of Open Access Journals (Sweden)
N. Parsafar
2013-07-01
Full Text Available Whenever good quality water is scarce, treated municipal wastewater will be considered for using in agriculture. In this research, raw and treated wastewater from Serkan Wastewater Treatment Plant, Hamadan province, Iran, were used to determine the transfer coefficient of Fe, Ni and Mn from soil to plant and some soil properties in potato cultivation under lysimetric conditions. Irrigation treatments were: raw wastewater, treated wastewater, tap water, combination of 50% raw wastewater and 50% tap water and combination of 50% treated wastewater and 50% tap water. Results showed that the effect of irrigation water quality on pH and EC was significant (P<0.01. The effect of soil depth on EC and pH was significant (P<0.01 and non-significant, respectively. The interaction on these parameters was not significant. pH was decreased and EC was decreased as soil depth increased. Maximum amounts of EC and pH of soil belonged to raw wastewater and tap water treatments, respectively. Higher EC in raw wastewater and pH in tap water was the reason for these high values in soil. The effect of treatments on transfer coefficient of Mn and Fe from soil to shoots was significant. In potato tubers, this effect was significant only for Mn. Maximum transfer coefficients from soil to potato shoots and tubers belonged to Ni, Fe and Mn, respectively. Also, coefficients of heavy metals transfer from soil to shoots were more than tubers.
Czech Academy of Sciences Publication Activity Database
Linek, V.; Korda?, M.; Zedníková, Mária; Moucha, T.
2004-01-01
Ro?. 43, ?. 12 (2004), s. 1511-1517. ISSN 0255-2701 Institutional research plan: CEZ:AV0Z4072921 Keywords : mass transfer coefficient * bubble * dynamic pressure method Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.033, year: 2004
Patorski, Jacek A.; Gindrat, Malko
2009-05-01
The proton beam passing through the wall area of a liquid metal (LM) target container, called entrance window, is causing deposition of maximum high heat flux amount 140 W/cm2.Previous experimental thermo-hydraulics investigations for the MEGAPIE LM-target at the SINQ facility of Heat- Transfer-Coefficient (HTC) using InfraRed-Thermography (IRT) have been presented at Thermosense 2006 and 2007 [1], [2] and references therein. During these investigations the IRT active sensors with applied heat fluxes of the small and low range from 2.5 to 15.2 W/cm2 are used. The heating shell foil of the sensor has been connected to steel dish enclosing LM target container by using electrical insulation ceramic glue. A higher, then achieved 15 W/cm2, heat flux has lead to delaminating of the heater. Because of interest to determinate the HTC-chart under real heat flux conditions and investigate some positive effect of heat flux buoyancy on cooling, the idea for the High Heat Flux (HHF) IRT Sensors, using of the Low Pressure Plasma Spraying - Thin Film (LPPS-TF) technology of the Sulzer Metco Company has been created. The paper presents the idea of multilayer thermal sprayed construction of HHF-IRT-Sensor, few realizations and some results of the first pre-test performed at the PSI LBE Double Pump Loop using the new sensor and the 2DD IRT methodology presented in [1].
International Nuclear Information System (INIS)
Following the Chernobyl accident in April 1986, the transfer of 131I and 137Cs from feed to milk was studied under experimental and common agricultural conditions. From measurements in different dairy farms in Southern Bavaria, equilibrium transfer coefficients for cow's milk were calculated to be 0.003 d L-1 (range 0.0015 to 0.005) for 131I and 0.003 d L-1 (range 0.0025 to 0.004) for 137Cs. In feeding experiments with cows and sheep under more controlled conditions, milk transfer coefficients of 0.007 d L-1 (range 0.0055 to 0.0081) for 131I and 0.003 d L-1 (range 0.0023 to 0.0053) for 137Cs were obtained for cows, while for sheep the 137Cs transfer coefficient was higher: 0.06 d L-1. The kinetics of the Cs transfer from fodder to cow's milk can be described by two exponential terms assuming biological half-lives in milk of 1-2 d and 10-20 d. The use of a fast component with 1.5 d and a fraction of 0.8, and a slow component with 15 d, gives a good approximation to the kinetics for all cows in this experiment
Condensation heat transfer on micro and nano structured super hydrophobic surface
Energy Technology Data Exchange (ETDEWEB)
Kim, Donghyun; Hwang, Kyung Won; Park, Hyun Sun; Kim, Moo Hwan [POSTECH, Pohang (Korea, Republic of)
2014-05-15
Condensation phenomena occur during the PCCS operation cooling the containment through phase change heat transfer. Accordingly it is important to enhance the condensation heat transfer performance. Condensation mode is commonly classified as filmwise condensation (FWC) and dropwise condensation (DWC). DWC heat transfer performance has an order of magnitude higher than FWC heat transfer performance. In DWC process, condensed liquid droplets attach to the surface and prevent transfer of heat to the cooled surface. Generally the condensate is removed by gravity. When removal rate of condensate is high, DWC heat transfer performance will be enhanced. In terms of removal rate, superhydrophobic surface, which is recently in the spotlight, is expected to have capability to enhance the DWC heat transfer efficiency by reducing droplet size. In this study, we investigated condensation heat transfer performance on micro and nano structured superhydrophobic surface. Condensation experiments on the micro and nano structured superhydrophobic surface were carried out and compared with those on the smooth hydrophobic surface in terms of heat transfer performance and condensed droplet morphologies. Through the experiments, we found that superhydrophobicity disappeared under the condensation circumstance. As a result, heat transfer performance on the superhydro-phobic structured surface decreased compared with that on the smooth hydrophobic surface. In order to enhance the condensation heat transfer performance with superhydrophobic property, condensation mechanism on superhydrophobic surface and the conditions for sustaining superhydrophobicity should be studied more.
Energy Technology Data Exchange (ETDEWEB)
Thiagarajan, S. J.; Wang, W.; Yang, R.; Narumanchi, S.; King, C.
2010-09-01
The DOE National Renewable Energy Laboratory (NREL) is leading a national effort to develop next-generation cooling technologies for hybrid vehicle electronics. The goal is to reduce the size, weight, and cost of power electronic modules that convert direct current from batteries to alternating current for the motor, and vice versa. Aggressive thermal management techniques help to increase power density and reduce weight and volume, while keeping chip temperatures within acceptable limits. The viability of aggressive cooling schemes such as spray and jet impingement in conjunction with enhanced surfaces is being explored. Here, we present results from a series of experiments with pool and spray boiling on enhanced surfaces, such as a microporous layer of copper and copper nanowires, using HFE-7100 as the working fluid. Spray impingement on the microporous coated surface showed an enhancement of 100%-300% in the heat transfer coefficient at a given wall superheat with respect to spray impingement on a plain surface under similar operating conditions. Critical heat flux also increased by 7%-20%, depending on flow rates.
Directory of Open Access Journals (Sweden)
Li-Hua Yu
2015-09-01
Full Text Available In recent years, water (R718 as a kind of natural refrigerant—which is environmentally-friendly, safe and cheap—has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important issue. There are many research papers on the evaporation of water, but there is a lack of data on the characteristics at sub-atmospheric pressures, especially lower than 3 kPa (the saturation temperature is 24 °C. In this paper, the experimental research on water boiling heat transfer on a horizontal copper rod surface at 1.8–3.3 kPa is presented. Regression equations of the boiling heat transfer coefficient are obtained based on the experimental data, which are convenient for practical application.
Khaiyer, Mandana M.; Doelling, David R.; Chan, Pui K.; Nordeen, MIchele L.; Palikonda, Rabindra; Yi, Yuhong; Minnis, Patrick
2006-01-01
Satellites can provide global coverage of a number of climatically important radiative parameters, including broadband (BB) shortwave (SW) and longwave (LW) fluxes at the top of the atmosphere (TOA) and surface. These parameters can be estimated from narrowband (NB) Geostationary Operational Environmental Satellite (GOES) data, but their accuracy is highly dependent on the validity of the narrowband-to-broadband (NB-BB) conversion formulas that are used to convert the NB fluxes to broadband values. The formula coefficients have historically been derived by regressing matched polarorbiting satellite BB fluxes or radiances with their NB counterparts from GOES (e.g., Minnis et al., 1984). More recently, the coefficients have been based on matched Earth Radiation Budget Experiment (ERBE) and GOES-6 data (Minnis and Smith, 1998). The Clouds and the Earth's Radiant Energy Budget (CERES see Wielicki et al. 1998)) project has recently developed much improved Angular Distribution Models (ADM; Loeb et al., 2003) and has higher resolution data compared to ERBE. A limited set of coefficients was also derived from matched GOES-8 and CERES data taken on Topical Rainfall Measuring Mission (TRMM) satellite (Chakrapani et al., 2003; Doelling et al., 2003). The NB-BB coefficients derived from CERES and the GOES suite should yield more accurate BB fluxes than from ERBE, but are limited spatially and seasonally. With CERES data taken from Terra and Aqua, it is now possible to derive more reliable NB-BB coefficients for any given area. Better TOA fluxes should translate to improved surface radiation fluxes derived using various algorithms. As part of an ongoing effort to provide accurate BB flux estimates for the Atmospheric Radiation Measurement (ARM) Program, this paper documents the derivation of new NB-BB coefficients for the ARM Southern Great Plains (SGP) domain and for the Darwin region of the Tropical Western Pacific (DTWP) domain.
Global surface temperature/heat transfer measurements using infrared imaging
Daryabeigi, Kamran
1992-01-01
A series of studies were conducted to evaluate the use of scanning radiometric infrared imaging systems for providing global surface temperature/heat transfer measurements in support of hypersonic wind tunnel testing. The in situ precision of the technique with narrow temperature span setting over the temperature range of 20 to 200 C was investigated. The precision of the technique over wider temperature span settings was also determined. The accuracy of technique for providing aerodynamic heating rates was investigated by performing measurements on a 10.2-centimeter hemisphere model in the Langley 31-inch Mach 10 tunnel, and comparing the results with theoretical predictions. Data from tests conducted on a generic orbiter model in this tunnel are also presented.
Scientific Electronic Library Online (English)
Cláudia R., Andrade; Edson L., Zaparoli.
Full Text Available This work studies the forced convection problem in internal flow between concentric annular ducts, with radial fins at the internal tube surface. The finned surface heat transfer is analyzed by two different approaches. In the first one, it is assumed one-dimensional heat conduction along the intern [...] al tube wall and fins, with the convection heat transfer coefficient being a known parameter, determined by an uncoupled solution. In the other way, named conjugated approach, the mathematical model (continuity, momentum, energy and K-epsilon equations) applied to tube annuli problem was numerically solved using finite element technique in a coupled formulation. At first time, a comparison was made between results obtained for the conjugated problem and experimental data, showing good agreement. Then, the temperature profiles under these two approaches were compared to each other to analyze the validity of the one-dimensional classical formulation that has been utilized in the heat exchanger design.
Energy Technology Data Exchange (ETDEWEB)
McEwen, Gerald D.; Chen Fan [Biological Engineering Program, Department of Biological and Irrigation Engineering, Utah State University, 4105 Old Main Hill, Logan, UT 84322-4105 (United States); Zhou Anhong, E-mail: Anhong.Zhou@usu.edu [Biological Engineering Program, Department of Biological and Irrigation Engineering, Utah State University, 4105 Old Main Hill, Logan, UT 84322-4105 (United States)
2009-06-08
Fundamental understanding of interfacial electron transfer (ET) among electrolyte/DNA/solid-surface will facilitate the design for electrical detection of DNA molecules. In this report, the electron transfer characteristics of synthetic DNA (sequence from pathogenic Cryptosporidium parvum) self-assembled on a gold surface was electrochemically studied. The effects of immobilization order on the interface ET related parameters such as diffusion coefficient (D{sub 0}), surface coverage ({theta}{sub R}), and monolayer thickness (d{sub i}) were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DNA surface density ({Gamma}{sub DNA}) was determined by the integration of the charge of the electro-oxidation current peaks during the initial cyclic voltammetry scans. It was found that the DNA surface densities at different modifications followed the order: {Gamma}{sub DNA} (dsS-DNA/Au) > {Gamma}{sub DNA} (MCH/dsS-DNA/Au) > {Gamma}{sub DNA} (dsS-DNA/MCH/Au). It was also revealed that the electro-oxidation of the DNA modified gold surface would involve the oxidation of nucleotides (guanine and adenine) with a 5.51 electron transfer mechanism and the oxidative desorption of DNA and MCH molecules by a 3 electron transfer mechanism. STM topography and current image analysis indicated that the surface conductivity after each surface modification followed the order: dsS-DNA/Au < MCH/dsS-DNA/Au < oxidized MCH/dsS-DNA/Au < Hoechst/oxidized MCH/dsS-DNA/Au. The results from this study suggested a combination of variations in immobilization order may provide an alternative approach for the optimization of DNA hybridization and the further development for electrical detection of DNA.
DEFF Research Database (Denmark)
Sing, M.; Schwingenschlögl, U.
2003-01-01
We have thoroughly characterized the surfaces of the organic charge-transfer salts TTF-TCNQ and (TMTSF)(2)PF6 which are generally acknowledged as prototypical examples of one-dimensional conductors. In particular x-ray-induced photoemission spectroscopy turns out to be a valuable nondestructive diagnostic tool. We show that the observation of generic one-dimensional signatures in photoemission spectra of the valence band close to the Fermi level can be strongly affected by surface effects. Especially, great care must be exercised taking evidence for an unusual one-dimensional many-body state exclusively from the observation of a pseudogap.
Precise determination of the spin-transfer coefficient KNN' for n->p elastic scattering at 187 MeV
Yang, Haichuan
IUCF experiment E401 determined the normal component spin-transfer coefficient KNN' for n->p elastic scattering at 187 MeV to an accuracy approaching ~+/-0.014 at 12 angles in the far-backward region (110° 14 obtained in earlier partial wave analyses or in fits to static few- body properties. Precise determination of np spin observables at intermediate energies may play an important role in resolving this discrepancy. The measurement was carried out at IUCF using the upgraded Polarized Neutron Facility (PNF). The polarized neutron beam was produced via the D(p->, n->) 2p reaction by bombarding a liquid deuterium target with polarized protons. After collimation, neutron fluxes of up to 5 × 106 n/s, with typical polarization Pn ~= 0.6, impinged on a solid CH2 target. Detection of both the proton and neutron from the second scattering, p(n->,p-> )n , provides event identification. Energy, angle, and timing information was collected for both outgoing nucleons on an event-by-event basis. An array of plastic scintillators comprised a neutron hodoscope, with angle segmentation of ?? = +/-2° and ?? = +/-2° in the lab frame. Effective n - ? discrimination was based on the correlation between neutron flight time and proton scattering angle. The forward-going protons were tracked with four planes each of vertical and horizontal drift chambers, and their polarization analyzed with a carbon-block polarimeter, containing two X-Y pairs of multi-wire proportional chambers and ?E - E detectors (plastic scintillator), similar to that used on the IUCF K600 spectrometer. Free-scattering correlations, imposed in software, reduced quasi-free contributions to less than 1% of the measured yields. Results for KNN' are compared to predictions of several partial wave analyses and potential models. The implication of these data for the magnitude of g2c is examined.
International Nuclear Information System (INIS)
In this paper, manner in defining the effective coefficient of diffusion of the radionuclide 137Cs, immobilized in cement matrix, due to the level of the matrix surface, open to contact leachant medium, is presented. Experimental is related to the radioactive waste-mortar mixture samples, completely immersed in the distilled water, as well as in distilled water with glass beds, as drainage system. Series of samples were prepared in manner to have different levels of the open surfaces, that are gradually increased. Effective coefficients of diffusion were calculated on the basis of the known cumulative leached fractions of the prospected radionuclide. Results of the mathematical modelling of the performed leaching processes, are implemented in the safety analysis of the solidified radioactive waste from impact with the environment, in the prolonged periods of disposal. (author)
International Nuclear Information System (INIS)
In the heat transfer studies by forced convection, we have few data about behavior of the fluids in an annular channel heated by a concentric pipe, such date is necessary to know the heat transfer coefficient that establish the interchange of energy and the thermic properties of the fluid with the geometry of the flow. In this work the objective, was to compare some empirical correlations that we needed for determinate the heat transfer coefficient for annular channels, where we obtained similar at the theoretical results of an experiment made by Miller and Benforado. It is important to know such coefficients because we can determinate the heat quantity transmitted to a probe zone, in which we simulate a nuclear fuel element that developed huge heat quantity that must be dispersed in short time. We give theoretical data of the heat forced transfer convection and we analyzed the phenomena in annular channels given some empirical correlations employed by some investigators and we analyzed each one. (Author)
Energy Technology Data Exchange (ETDEWEB)
1976-03-01
A compilation is presented of heat transfer and pressure drop data which were collected from literature reports on extended surface heat exchangers. The type of extended surfaces considered are tubular finned tubes as distinct from compact heat exchangers. These surfaces have a base tube to which additional surface was added by mechanical means. This additional surface is in the form of fins attached to the outside surface of the tube. These tubes are normally employed for heat transfer between a liquid and a gas. The liquid flows inside the tubes and the gas, normally air, flows outside the tubes. The fins are oriented so that their surface is transverse to the axis of the tubes. The gas flows across the tubes in a direction parallel to the fin surface.
International Nuclear Information System (INIS)
The transfer in cattle of the radionuclides 137Cs, 60Co, 54Mn, 22Na, 131I and 95mTc was studied experimentally to determine transfer coefficients from feed to milk and meat. Special interest was kept on normal feeding and maintenance conditions used in Germany. The radionuclides were incorporated into fodder plants through root uptake and thus available in a chemical form resulting from the contamination of agricultural soil. This permitted realistic simulation of the soil-plant-animal food chain. The equilibrium transfer coefficients for milk were calculated to be 22Na: 0.016±0.002 d/l, 60Co: ? 0.0002 d/l, 54Mn: ? 0.0005 d/l, and 137Cs: 0.0022±0.0002 d/l. The equilibrium transfer coefficients for meat were calculated to be 22Na: 0.01±0.002 d/kg, 60Co: ? 0.00013 d/kg, 54Mn: ? 0.0005 d/kg, and 137Cs: 0.0062±0.0006 d/kg. A single dose of 131I was orally administered three times in the chemical form of iodide. Models were applied to obtain parameters for a quantitative description of the iodine metabolism. The equilibrium transfer factor for 131I in this chemical form to milk was calculated to be 0.009±0.0014 d/l. For 95mTc only an upper limit of the transfer factor of 1.7 . 10-4 d/l could be estimated because of the small amount of radioactivity available. (orig.)
Directory of Open Access Journals (Sweden)
M.G Reddy
2011-01-01
Full Text Available A steady two-dimensional MHD free convection and mass transfer flow past an inclined semi-infinite vertical surface in the presence of heat generation and a porous medium has been studied numerically. The governing partial differential equations are reduced to a system of ordinary differential equations by introducing similarity transformations. The non-linear similarity equations are solved numerically by applying the Runge-Kutta method of fourth order with shooting technique. The numerical results are presented graphically for different values of the parameters. Finally, the numerical values of the local skin-friction coefficient, local Nusselt number and Sherwood number are shown in Table 1.
International Nuclear Information System (INIS)
It has be done to determination of mass transfer coefficient on the extractions Ce (IV) by Di (2- ethylhexyl) phosphoric acid (D2EHPA) using CELL ARMOLLEX. CELL ARMOLLEX have two stirrers are top and down to make tin layer between organic face and water face to be constant so that diffusion mechanism reaction was took place. It was obtained that mass transfer coefficient on variation of acids 1-3 N = 2.50x10-3 - 1.06x10-3 ; on variation of concentration reactant 2.5 - 7.5% = 2.21x10-3 - 2.58x10-3 and on the variation of stirring speed = 4.703x10-3 - 1.88x10-4
Directory of Open Access Journals (Sweden)
GUO Zhi-peng
2007-02-01
Full Text Available The high pressure die casting (HPDC process is one of the fastest growing and most efficient methods for the production of complex shape castings of magnesium and aluminum alloys in today’s manufacturing industry.In this study, a high pressure die casting experiment using AZ91D magnesium alloy was conducted, and the temperature profiles inside the die were Measured. By using a computer program based on solving the inverse heat problem, the metal/die interfacial heat transfer coefficient (IHTC was calculated and studied. The results show that the IHTC between the metal and die increases right after the liquid metal is brought into the cavity by the plunger,and decreases as the solidification process of the liquid metal proceeds until the liquid metal is completely solidified,when the IHTC tends to be stable. The interfacial heat transfer coefficient shows different characteristics under different casting wall thicknesses and varies with the change of solidification behavior.
Energy Technology Data Exchange (ETDEWEB)
Kotthoff, Stephan; Gorenflo, Dieter [Thermodynamik und Energietechnik, Universitaet Paderborn, D-33098 Paderborn (Germany); Danger, Elisabeth [Benteler Automobiltechnik GmbH, Paderborn (Germany); Luke, Andrea [Institut fuer Thermodynamik, Universitaet Hannover (Germany)
2006-03-15
The present project within the joint research program on fundamentals of boiling heat transfer aims at better understanding of the basic processes which produce heat transfer enhancement in nucleate pool boiling. In the experiments, heater surfaces with two kinds of modifications for enhancement in the form of macro cavities with comparatively simple shapes are used in order to link experimental results of bubble formation and heat transfer to the geometric features of the cavities without additional assumptions, and particularly to resolve their overall effect on heat transfer into local convective or evaporative contributions without introducing severe simplifications. The very accurate results on local heat transfer obtained so far around the circumference of the horizontal test tube with and without macro cavities for enhancement, and their combination with the local events connected to growing, departing and sliding bubbles are suitable to interpret the basic convective and evaporative processes which produce heat transfer enhancement in nucleate pool boiling. (authors)
Selig, Stefan; Westig, Marc Peter; Jacobs, Karl; Schultz, Michael; Honingh, Netty
2014-01-01
In this paper we present the experimental realization of a Nb tunnel junction connected to a high-gap superconducting NbTiN embedding circuit. We investigate relaxation of nonequilibrium quasiparticles in a small volume Au layer between the Nb tunnel junction and the NbTiN circuit. We find a saturation in the effective heat-transfer coefficient consistent with a simple theoretical model. This saturation is determined by the thickness of the Au layer. Our findings are importa...
International Nuclear Information System (INIS)
Tehe vapour bubble growth and break off, temperature distribution in the overheated layer during nucleate boiling of liquids are simulated numerically. A new mechanism of vapour bubble growth is suggested. Analytical relations are given for the heat transfer coefficient and the onset of a developed boiling of liquids. The calculated and measured intrinsic and integral characteristics for boiling nitrogen, oxygen and helium are observed to be in good agreement. 53 refs.; 16 figs.; 7 tabs
Spin transfer coefficient Knn and polarization Py of the reaction pp ? d?+ between 1.3 and 2.4 GeV
International Nuclear Information System (INIS)
The results of the measurement of the spin transfer coefficient and the polarization of the reaction pp ? d?+ at energies Tp ? 1300 MeV are presented. These data show a strong dependence of the angular distribution with energy and a structure around ? s = 2.65 GeV which has been already observed in other observables. At Tp = 1300 MeV the data disagree with the prediction of the last phase-shift analysis
Liquid transfer between two solid surfaces with the effect of contact angle hysteresis
Chen, Huanchen; Tang, Tian; Amirfazli, Alidad
2013-11-01
Drop transfer from one solid surface to another (e.g. due to the approach of a surface from top to a sessile drop resting on a lower surface) is widely observed in many industrial areas, e.g. offset printing. This process is governed by many factors such as the contact angle (CA) and contact angle hysteresis (CAH) of surfaces, viscosity of the liquid and the rate at which the donor and acceptor surfaces are separated. In this work, an experimental apparatus is developed to study the transfer of liquid drop between surfaces, with the particular focus on addressing the effect of the surfaces' CAH when the loading speed is low (transfer is quasi-static). In the experiment, a liquid bridge between the two surfaces is first formed by compression; then stretched to the point of breakage. By using surfaces that have similar CA but dissimilar CAH, the liquid transfer ratio (the amount of liquid transferred to the acceptor surface over the total amount of liquid) is found to be significantly influenced by CAH. In addition, as a result of CAH, the maximum compression of the liquid bridge is found to play an important role in determining the transfer ratio. These findings can be very helpful for the design of surfaces and loading conditions to achieve desired transfer ratios in practice.
Pool boiling heat transfer on heterogeneous wetting surface with hydrophobic dots
International Nuclear Information System (INIS)
The boiling heat transfer mechanism of pool boiling is fundamental phenomena for understanding the phase change nature. Of many surface characteristics, the effects of wettability of heating surface is focused on as the dominant parameter for bubble dynamics and boiling heat transfer. In this study, highly controlled heating surfaces via MEMs technique were used for understanding the boiling heat transfer of heterogeneous wetting surfaces mixed by hydrophobic dots and a hydrophilic substrate. The diameter of hydrophobic dots and area ratio of phobic dots to heating area were regulated. The range of phobic dot diameter and area ratio were 50?1000?m and 18.33?54.3%, respectively. The performance of boiling heat transfer of each surface were evaluated by comparing with a wholly hydrophilic surface. It will contribute to understand the mechanism and criterion of enhanced heating surface condition by modified surface treatment procedure
Directory of Open Access Journals (Sweden)
Kneževi? Milena M.
2014-01-01
Full Text Available Distribution of gas bubbles and volumetric mass transfer coefficient, Kla, in a three phase system, with different types of solid particles at different operation conditions were studied in this paper. The ranges of superficial gas and liquid velocities used in this study were 0,03-0,09 m/s and 0-0,1 m/s, respectively. The three different types of solid particles were used as a bed in the column (glass dp=3 mm, dp=6 mm; ceramic dp=6 mm. The experiments were carried out in a 2D plexiglas column, 278 x 20,4 x 500 mm and in a cylindrical plexiglas column, with a diameter of 64 mm and a hight of 2000 mm. The Kla coefficient increased with gas and liquid velocities. Results showed that the volumetric mass transfer coefficient has a higher values in three phase system, with solid particles, compared with two phase system. The particles properties (diameter and density have a major impact on oxygen mass transfer in three phase systems.
Energy Technology Data Exchange (ETDEWEB)
Marcos, J.D. [Escuela Tecnica Superior Ingenieria Industrial, UNED, c/Juan del Rosal 12, 28040 Madrid (Spain); Izquierdo, M. [Instituto de Ciencias de la Construccion Eduardo Torroja (CSIC), c/Serrano Galvache 4, 28033 Madrid (Spain); Escuela Politecnica Superior, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Leganes, Madrid (Spain); Lizarte, R. [Escuela Politecnica Superior, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Leganes, Madrid (Spain); Palacios, E. [Escuela Universitaria Ingenieria Tecnica Industrial, Universidad Politecnica de Madrid, C/ Ronda de Valencia 3, 28012 Madrid (Spain); Infante Ferreira, C.A. [Delft University of Technology, Engineering Thermodynamics, Leeghwaterstraat 44, 2628 CA Delft (Netherlands)
2009-06-15
The aim of this work is to determine the boiling heat transfer coefficients in the high temperature desorber (HTD) of an air-cooled double effect lithium bromide/water absorption prototype. The HTD is a plate heat exchanger (PHE) with thermal oil on one side, and a lithium bromide solution on the other side. Several experiments were performed with this PHE while the prototype was working with an outdoor dry bulb temperature around 42 C and condensation temperature around 55 C. The registered data allowed to calculate the global heat transfer coefficient and the heat transfer coefficient for the LiBr/water mixture in forced convective boiling. The pressure drop produced by the boiling of the refrigerant has been calculated as well. It has been verified that the largest part of the heat supplied in the generator is required for desorbing the refrigerant (except for the maximum solution mass flow), while the sensible heat varies from 10% to 50% of the total heat supplied. (author)
Energy Technology Data Exchange (ETDEWEB)
Eckels, S.J. [Kansas State Univ., Manhattan, KS (United States); Doerr, T.M.; Pate, M.B. [Iowa State Univ., Ames, IA (United States). Mechanical Engineering Dept.
1998-10-01
This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.
Effect of surface roughness on rarefied-gas heat transfer in microbearings
International Nuclear Information System (INIS)
In this Letter, the rarefaction and roughness effects on the heat transfer process in gas microbearings are investigated. A heat transfer model is developed by introducing two-variable Weierstrass–Mandelbrot (W–M) function with fractal geometry. The heat transfer problem in the multiscale self-affine rough microbearings at slip flow regime is analyzed and discussed. The results show that rarefaction has more significant effect on heat transfer in rough microbearings with lower fractal dimension. The negative influence of roughness on heat transfer found to be the Nusselt number reduction. The heat transfer performance can be optimized with increasing fractal dimension of the rough surface. -- Highlights: ? A heat transfer model is described with fractal geometry. ? The rarefaction affects the heat transfer under lower fractal dimension. ? The negative influence of roughness on heat transfer is Nusselt number reduction. ? The heat transfer can be optimized with increasing fractal dimension.
Radionuclide transfer onto ground surface in surface water flow. 2. Undisturbed tuff rock
Energy Technology Data Exchange (ETDEWEB)
Mukai, Masayuki; Takebe, Shinichi; Komiya, Tomokazu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1994-09-01
Radionuclide migration with ground surface water flow is considered to be one of path ways in the scenario for environmental migration of the radionuclide leaked from LLRW depository. To study the radionuclide migration demonstratively, a ground surface radionuclide migration test was carried out by simulating radioactive solution flowing on the sloped tuff rock surface. Tuff rock sample of 240 cm in length taken from the Shimokita district was used to test the transfer of {sup 60}Co, {sup 85}Sr and {sup 137}Cs onto the sample surface from the flowing radioactive solution under restricted infiltration condition at flow rates of 25, 80, 160ml/min and duration of 56h. The concentration change of the radionuclides in effluent was nearly constant as a function of elapsed time during the experimental period, but decreased with lower flow rates. Among the three radionuclides, {sup 137}Cs was greatly decreased its concentration to 30% of the inflow. Adsorbed distribution of the radionuclides concentration on the ground surface decreased gradually with the distance from the inlet, and showed greater gradient at lower flow rate. Analyzing the result by the migration model, where a vertical advection distribution and two-dimensional diffusion in surface water are adopted with a first order adsorption reaction, value of migration parameters was obtained relating to the radionuclide adsorption and the surface water flow, and the measured distribution could be well simulated by adopting the value to the model. By comparing the values with the case of loamy soil layer, all values of the migration parameters showed not so great difference between two samples for {sup 60}Co and {sup 85}Sr. For {sup 137}Cs, reflecting a few larger value of adsorption to the tuff rock, larger ability to reduce the concentration of flowing radioactive solution could be indicated than that to the loamy soil surface by estimation for long flowed distance. (author).
Radionuclide transfer onto ground surface in surface water flow. 2. Undisturbed tuff rock
International Nuclear Information System (INIS)
Radionuclide migration with ground surface water flow is considered to be one of path ways in the scenario for environmental migration of the radionuclide leaked from LLRW depository. To study the radionuclide migration demonstratively, a ground surface radionuclide migration test was carried out by simulating radioactive solution flowing on the sloped tuff rock surface. Tuff rock sample of 240 cm in length taken from the Shimokita district was used to test the transfer of 60Co, 85Sr and 137Cs onto the sample surface from the flowing radioactive solution under restricted infiltration condition at flow rates of 25, 80, 160ml/min and duration of 56h. The concentration change of the radionuclides in effluent was nearly constant as a function of elapsed time during the experimental period, but decreased with lower flow rates. Among the three radionuclides, 137Cs was greatly decreased its concentration to 30% of the inflow. Adsorbed distribution of the radionuclides concentration on the ground surface decreased gradually with the distance from the inlet, and showed greater gradient at lower flow rate. Analyzing the result by the migration model, where a vertical advection distribution and two-dimensional diffusion in surface water are adopted with a first order adsorption reaction, value of migration parameters was obtained relating to the radionuclide adsorption and the surface water flow, and the measured distribution could be well simulated by adopting the value to the model. By comparing the values with the case of loamy soil layer, all values of the migration parameters showed not so great difference between two samples for 60Co and 85Sr. For 137Cs, reflecting a few larger value of adsorption to the tuff rock, larger ability to reduce the concentration of flowing radioactive solution could be indicated than that to the loamy soil surface by estimation for long flowed distance. (author)
Heat transfer by free convection from the inside surface of the vertical and inclined elliptic tube
International Nuclear Information System (INIS)
Free convection from the inside surface of vertical and inclined elliptic tubes of axis ratio (a:b) 2:1 with a uniformly heated surface (constant heat flux) is investigated experimentally. The effects of orientation angle (?) and inclination angle (?) on the heat transfer coefficient were studied. The orientation angle (?) is varied from 0 deg. (when the major axis is horizontal) to 90 deg. (when the major axis is vertical) with steps of 15 deg. The inclination angle (?) is measured from the horizontal and varied from 15 deg. to 75 deg. with steps of 15 deg. The vertical position is considered as a special case of the inclined case when ? = 90. The experiments covered a range of Rayleigh number, Ra from 2.6 x 106 to 3.6 x 107. The local and average Nusselt numbers are estimated for different orientation angles and inclination angles at different Rayleigh numbers. The results obtained showed that the local Nu increased with the increase of axial distance from the lower end of the elliptic tube until a maximum value near the upper end, and then, it gradually decreased. The average Nu increases with the increase of ? or ? at the same Ra. The results obtained are correlated by dimensionless groups and with the available data of the inclined and vertical elliptic tubes
Energy Technology Data Exchange (ETDEWEB)
Tam, L.M.; Ghajar, A.J. [Oklahoma State Univ., Stillwater, OK (United States). School of Mechanical and Aerospace Engineering
1996-12-31
The local heat transfer characteristics for ethylene glycol water mixtures flowing in a horizontal circular straight tube with a bell-mouth inlet have been determined experimentally over a flow Reynolds number range of 1,500 to 27,000. A wall-boundary heating condition of uniform heat flux was imposed. The variation of local heat transfer coefficient with length in the transition and turbulent flow regimes is very unusual. For the bell-mouth inlet, the boundary layer along the tube wall is at first laminar and then changes through a transition region to the turbulent condition causing a dip in the Nu-x/D curve. The length of the dip in the transition region is much longer than that in the turbulent region. For the experiments the length of the dip in the transition region varied from x/D = 100 to 175 in comparison to an x/D < 25 for the turbulent region. The presence of the dip in the transition region causes a significant influence on both the local and the average heat transfer coefficients. This is particularly important for heat transfer calculations in short tubes with a bell-mouth inlet.
International Nuclear Information System (INIS)
Boiling heat transfer characteristics of nano-fluids with nano-particles suspended in water are studied using different volume concentrations of alumina nano-particles. Pool boiling heat transfer coefficients and phenomena of nano-fluids are compared with those of pure water, which are acquired on a horizontal flat surface with highly smooth roughness of a few tens nanometers. The experimental results show that these nano-fluids have poor heat transfer performance compared to pure water in natural convection and nucleate boiling. This is related to a change of surface characteristics by the deposition of nano-particles. Comparisons between the experimental data and the Rhosenow correlation show that the correlation has a possibility to predict the performance with an appropriate modified liquid-surface combination factor and changed physical properties of a base liquid. (authors)
Draganov, Deyan; Ruigrok, Elmer; Ghose, Ranajit; Mikesell, Dylan; van Wijk, Kasper
2015-01-01
Seismic interferometry can retrieve the Green's function between receivers from the cross-correlation and summation of recordings from a boundary of surrounding sources. Having the sources only along a boundary is sufficient if the medium is lossless. If the medium is dissipative, the retrieved result using cross-correlation contains non-physical (ghost) arrivals. When using receivers at the surface and transient sources in the subsurface for the retrieval of the reflection response in a dissipative medium, it has been shown that the retrieved ghost reflections are characteristic of the quality factor of the subsurface. The ghost reflections are caused by internal reflections inside subsurface layers. It has been shown with numerical examples for recordings in a borehole from a surface source that a ghost reflection can be discriminated from physical reflections and tied to a specific subsurface layer. After connecting the ghost reflection to a specific layer, the quality factor of the medium above this layer and the reflection coefficient at the layer interface can be estimated. In this article, we show how the above principles can be adapted and applied for surface waves. Due to intrinsic losses in the medium, surface-wave ghost reflections are retrieved from internal scattering between subvertical boundaries. We demonstrate the method on an ultrasonic dataset recorded on a sample composed of a PVC block and an aluminum block. The aluminum block has a groove parallel to the PVC/aluminum interface. Using a surface-wave ghost reflection between the groove and the PVC/aluminum interface, we estimate the quality factor of the PVC and the reflection coefficient at the PVC/aluminum interface. We also show that the ghost reflection can be identified and tied to the layer between the groove and the PVC/aluminum interface, thus confirming previous numerical findings.
Energy Technology Data Exchange (ETDEWEB)
Perez Galindo, Jose Arturo; Garcia Gutierrez, Alonso [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1985-12-31
This work describes the experimental technique for the sublimation of naphthalene in air which measures heat transfer coefficients through the use of the analogy between the transference phenomena of heat and mass. The technique used to substitute the experimental measurements of heat transfer, in which it is difficult to control the border thermal conditions, when they are dimmed by the omnipresent problem of heat conduction through the walls of the transference surfaces. Two examples are included of the application technique and its potential is outlined. [Espanol] En este trabajo se describe la tecnica experimental de la sublimacion de naftalina en aire mediante la que se miden coeficientes de transferencia de masa. Los datos asi obtenidos pueden convertirse en coeficientes de transferencia de calor a traves del uso de la analogia entre los fenomenos de transferencia de calor y masa. La tecnica se utiliza para substituir las mediciones experimentales de transferencia de calor, en las que es dificil controlar las condiciones termicas de frontera, cuando las empana el problema omnipresente de la conduccion de calor a traves de las paredes de las superficies de transferencia. Se incluyen dos ejemplos de la aplicacion de la tecnica y se destaca su potencial.
Kabeel, A. E.; Abdelgaied, Mohamed
2015-08-01
Nano-fluids are used to improve the heat transfer rates in heat exchangers, especially; the shell-and-tube heat exchanger that is considered one of the most important types of heat exchangers. In the present study, an experimental loop is constructed to study the thermal characteristics of the shell-and-tube heat exchanger; at different concentrations of Al2O3 nonmetallic particles (0.0, 2, 4, and 6 %). This material concentrations is by volume concentrations in pure water as a base fluid. The effects of nano-fluid concentrations on the performance of shell and tube heat exchanger have been conducted based on the overall heat transfer coefficient, the friction factor, the pressure drop in tube side, and the entropy generation rate. The experimental results show that; the highest heat transfer coefficient is obtained at a nano-fluid concentration of 4 % of the shell side. In shell side the maximum percentage increase in the overall heat transfer coefficient has reached 29.8 % for a nano-fluid concentration of 4 %, relative to the case of the base fluid (water) at the same tube side Reynolds number. However; in the tube side the maximum relative increase in pressure drop has recorded the values of 12, 28 and 48 % for a nano-material concentration of 2, 4 and 6 %, respectively, relative to the case without nano-fluid, at an approximate value of 56,000 for Reynolds number. The entropy generation reduces with increasing the nonmetallic particle volume fraction of the same flow rates. For increase the nonmetallic particle volume fraction from 0.0 to 6 % the rate of entropy generation decrease by 10 %.
Directory of Open Access Journals (Sweden)
Mohammad H. Yazdi
2011-12-01
Full Text Available This paper presents an analysis of the energy exchange resulting from a 2D steady magnetohydrodynamics (MHD flow past a permeable surface with partial slip in the presence of the viscous dissipation effect under convective heating boundary conditions. A magnetic field can effectively control the motion of an electrically conducting fluid in micro scale systems, which can be applied for fluid transportation. Local similarity solutions for the transformed governing equations are obtained, and the reduced ordinary differential equations solved numerically via an explicit Runge-Kutta (4, 5 formula, the Dormand-Prince pair and shooting method, which is valid for fixed positions along the surface. The effects of various physical parameters, such as the magnetic parameter, the slip coefficient, the suction/injection parameter, the Biot number, the Prandtl number and the Eckert number, on the flow and heat transfer characteristics are presented graphically and discussed. The results indicate that the heat transfer rate increases with the increase in Biot number, slip coefficient, suction and magnetic parameter, whereas it decreases with the increase in Eckert number and injection.
A REVIEW OF HEAT TRANSFER CHARACTERISTICS IN RIB ROUGHENED SURFACES IN RECTANGULAR CHANNEL
Directory of Open Access Journals (Sweden)
Mayur P.
2014-12-01
Full Text Available Enhancement of heat transfer in internal passages is always preferred in variety of applications like combustion chamber, cooling of gas turbine blades, compact heat exchangers and solar air heater etc. Several attempts have been made on enhancement of heat transfer which is broadly classified in two categories namely active and passive techniques. One of the wellknown passive methods of enhancing the heat transfer is to roughen the heat transfer surface artificially by the use of repeated transverse or inclined ribs to the flow. This paper review the heat transfer evaluation in a compact rectangular duct by using the rib roughened surface. Some distinguished roughness geometries have been compared on the basis of heat transfer enhancements and thermo hydraulic performance to draw attention towards their usefulness for specific applications. Furthermore, light is thrown on different investigation techniques adopted for prediction of heat transfer and friction characteristics of artificially roughened solar air heaters to recognize features and limitations of each technique.
Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Witkamp, Geert-Jan
2008-01-01
In a cylindrical scraped heat exchanger crystallizer geometry the flow field influence on the local heat transfer distribution on an evenly cooled scraped heat exchanger surface has been studied by direct measurements of the heat exchanger surface temperature and the fluid velocity field inside the crystallizer. Liquid Crystal Thermometry revealed that the local heat transfer is higher in the middle area of the scraped surface. Stereoscopic PIV measurements demonstrated that the secondary flo...
The problems of effective coefficient of static friction at friction surfaces of joint replacement.
Czech Academy of Sciences Publication Activity Database
Franta, L.; Pražák, Josef
Praha : Ústav termomechaniky AV ?R, 2004 - (Zolotarev, I.), s. 1-6 ISBN 80-85918-88-9. [Engineering mechanics 2004. Svratka (CZ), 10.05.2004-13.05.2004] Institutional research plan: CEZ:AV0Z2076919 Keywords : friction surfaces * joint replacement Subject RIV: BJ - Thermodynamics
Scientific Electronic Library Online (English)
Josué, Imbert-González; Octavio, García-Valladares; A., Viedma; Reinaldo, Guillen-Gordín.
2014-12-01
Full Text Available La transferencia de calor incrementada por métodos pasivos se emplea en diversos intercambiadores de calor de alta efectividad. El objetivo del trabajo presentado fue la evaluación del estado de las investigaciones en el campo de la transferencia de calor mejorada en espacios anulares, a partir del [...] empleo de elementos turbulizadores helicoidales como técnicas pasivas. La revisión se centró en el empleo de láminas helicoidales y espirales, la obtención de ecuaciones de correlación del coeficiente de transferencia de calor incrementado, el coeficiente de fricción y la evaluación que se realiza de este proceso por parte de diferentes autores. El análisis crítico permitió realizar valoraciones integradas y recomendar sobre los aspectos que podrían ser analizados en el futuro en esta temática. Abstract in english The transfer enhancement by passive methods is used in several heat exchanger of high effectiveness. The objective of the presented work was the evaluation of the state of the investigations in heat transfer enhancement in annular spaces, from the employment of elements helical. The revision was cen [...] tered in the employment of twisted tape and wire coil in spiral, the equations of correlation obtained of the coefficient of transfer of increased heat, the coefficient of friction and the evaluation that was carried out of this process on the part of different authors. From the critical analysis of the published results, the authors recommend on the topics that can be analyzed in the future in this area.
Directory of Open Access Journals (Sweden)
X. Y. Ji
2010-12-01
Full Text Available The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure variation of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width, 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data.
Scientific Electronic Library Online (English)
X. Y., Ji; Y. G., Ma; T. T., Fu; CH. Y., Zhu; D. J., Wang.
2010-12-01
Full Text Available The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure varia [...] tion of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width), 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data.
The effect of surface roughness on the heat exchange and pressure-drop coefficients
International Nuclear Information System (INIS)
The effect of various types of roughness on the wall of an axial tube in an annular space of 15-25 mm cooled by an air-flow has been studied in the case of steady turbulence. Roughness of the type 'disrupter of the boundary layer' was set up using triangular threads of 0.2 to 0.4 mm thickness machined in the tube itself, or brass or glass wire wound on a smooth tube. Tests were also carried out using the roughness provided by regularly spaced pyramids 0.4 mm high. The results obtained showed that the heat exchange increased because of the presence of this roughness. A maximum in the heat exchange and pressure-drop coefficients was observed when the pitch equals about eight times the height of the thread. An analytical method has been developed and experiments have been carried out in which the two walls of the annular space were heated in such a way as to transmit unequal heat flows. The region considered is limited to Reynolds's numbers of between 5 X 103 and 5 x 104 and wall temperatures of under 250 deg C. (author)
Surface roughness and friction coefficient in peened friction stir welded 2195 aluminum alloy
International Nuclear Information System (INIS)
The tribological properties of friction stir welded 2195 aluminum alloy joints were investigated for several laser- and shot-peened specimens. The first portion of this study assessed the surface roughness changes at different regions of the weld resulting from the various peening processes and included an atomic force microscopy (AFM) study to reveal fine structures. The second portion investigated the friction characteristics for various conditions when slid against a 440C ball slider. Shot peening resulted in significant surface roughness when compared to the unpeened and laser-peened samples. The initial friction for all types of specimens was highly variable. However, long-term friction was shown to be lowest for samples with no peening treatment. Laser peening caused the friction to increase slightly. The shot peening process on the other hand resulted in an increase of the long-term friction effects on both sides of the weld.
Surface roughness and friction coefficient in peened friction stir welded 2195 aluminum alloy
Energy Technology Data Exchange (ETDEWEB)
Hatamleh, Omar, E-mail: omar.hatamleh-1@nasa.gov [Structures Branch, NASA - Johnson Space Center, Houston, TX 77058 (United States); Smith, James [Structures Branch, NASA - Johnson Space Center, Houston, TX 77058 (United States); Cohen, Donald [Michigan Metrology LLC, Livonia, MI 48152 (United States); Bradley, Robert [Oak Ridge Associate Universities, Houston, TX 77058 (United States)
2009-05-30
The tribological properties of friction stir welded 2195 aluminum alloy joints were investigated for several laser- and shot-peened specimens. The first portion of this study assessed the surface roughness changes at different regions of the weld resulting from the various peening processes and included an atomic force microscopy (AFM) study to reveal fine structures. The second portion investigated the friction characteristics for various conditions when slid against a 440C ball slider. Shot peening resulted in significant surface roughness when compared to the unpeened and laser-peened samples. The initial friction for all types of specimens was highly variable. However, long-term friction was shown to be lowest for samples with no peening treatment. Laser peening caused the friction to increase slightly. The shot peening process on the other hand resulted in an increase of the long-term friction effects on both sides of the weld.
Ebel, B.A.; Mirus, B.B.; Heppner, C.S.; VanderKwaak, J.E.; Loague, K.
2009-01-01
Distributed hydrologic models capable of simulating fully-coupled surface water and groundwater flow are increasingly used to examine problems in the hydrologic sciences. Several techniques are currently available to couple the surface and subsurface; the two most frequently employed approaches are first-order exchange coefficients (a.k.a., the surface conductance method) and enforced continuity of pressure and flux at the surface-subsurface boundary condition. The effort reported here examines the parameter sensitivity of simulated hydrologic response for the first-order exchange coefficients at a well-characterized field site using the fully coupled Integrated Hydrology Model (InHM). This investigation demonstrates that the first-order exchange coefficients can be selected such that the simulated hydrologic response is insensitive to the parameter choice, while simulation time is considerably reduced. Alternatively, the ability to choose a first-order exchange coefficient that intentionally decouples the surface and subsurface facilitates concept-development simulations to examine real-world situations where the surface-subsurface exchange is impaired. While the parameters comprising the first-order exchange coefficient cannot be directly estimated or measured, the insensitivity of the simulated flow system to these parameters (when chosen appropriately) combined with the ability to mimic actual physical processes suggests that the first-order exchange coefficient approach can be consistent with a physics-based framework. Copyright ?? 2009 John Wiley & Sons, Ltd.
Upscale energy transfer and flow topology in free-surface turbulence
Lovecchio, Salvatore; Zonta, Francesco; Soldati, Alfredo
2015-03-01
Free-surface turbulence, albeit constrained onto a two-dimensional space, exhibits features that barely resemble predictions of simplified two-dimensional modeling. We demonstrate that, in a three-dimensional open channel flow, surface turbulence is characterized by upscale energy transfer, which controls the long-term evolution of the larger scales. We are able to associate downscale and upscale energy transfer at the surface with the two-dimensional divergence of velocity. We finally demonstrate that surface compressibility confirms the strongly three-dimensional nature of surface turbulence.
Thomas, John E; Ou, Li-Tse; Allen, Leon H; Vu, Joseph C; Dickson, Donald W
2006-02-01
Methyl bromide, a pre-emergent soil fumigant, is scheduled to be phased out in the US by 2005, with exceptions for critical use. Comparison of some of the physical constants related to distribution and retention for methyl bromide (MBr) to other fumigants yields a useful quantification of possible alternatives. In this study, the atmospheric and subsurface dissipation of methyl bromide as well as (Z)- and (E)-1,3-dichloropropene (1,3-D) isomers in Telone II were examined. The Henry's law constants of the three chemicals at soil temperature and their mass transfer coefficients for movement through an agricultural mulch of UV-resistant, high-density polyethylene (PE) were evaluated using field data. At the soil temperature of 16.4 degrees C, calculated Henry's law constant gave a fumigant ranking of MBr (0.21)>(Z)-1,3-D (0.041)>(E)-1,3-D (0.027). Since rapid subsurface distribution of a fumigant is highly dependent on the amount in the gas phase, the greater value for Henry's law constant implies faster distribution throughout the soil. After distribution through the soil, retention of the fumigant becomes imperative. Calculation of the fumigant's mass transfer coefficients through PE from field data gave a ranking of the three chemicals: MBr (1.08 cm/h)<(E)-1,3-D (3.25 cm/h)<(Z)-1,3-D (4.13 cm/h). With mass transfer coefficients of this magnitude, it was concluded that PE film was an inadequate barrier for retaining these fumigants in an agricultural setting. PMID:16084566
Kolthoff, Izaak M.; Chantooni, Miran K.
1980-01-01
Between dipolar aprotic solvents S1 and S2, the transfer activity coefficients, S1?S2, of complexed sodium, potassium, thallium(I), and silver ions with cryptand 2.2.2 have been found to be equal to that of the cryptand. With reference to methanol (S1), this equality does not hold, the cryptates being more or less solvated by hydrogen bonding in this solvent. In water as a solvent, the cryptates are on a considerably higher level of free energy than in the organic solvents. This is attributed...
International Nuclear Information System (INIS)
A new method to calculate pressure drop (?p) and shell-side heat transfer coefficient (h sub(c)) in a shell-and-tube heat exchanger with segmental baffles is presented. The method is based on the solution of the equations of conservation of mass and momentum between two baffles. The calculated distributions of pressure and velocities given respectively, ?p and h sub(c). The values of ?p and h sub(c) are correlated for a given geometry whit the shell side fluid properties and flow rate. The calculated and experimental results agree very well for a U-Tube heat exchanger. (Author)
International Nuclear Information System (INIS)
The aim of this work is to improve heat transfer performances of flush mounted heat sinks used in electronic cooling. To do this we patterned 1.23 cm2 heat sinks surfaces by microstructured roughnesses built by laser etching manufacturing technique, and experimentally measured the convective heat transfer enhancements due to different patterns. Each roughness differs from the others with regards to the number and the size of the micro-fins (e.g. the micro- fin length ranges from 200 to 1100 ?m). Experimental tests were carried out in forced air cooling regime. In particular fully turbulent flows (heating edge based Reynolds number ranging from 3000 to 17000) were explored. Convective heat transfer coefficient of the best micro-structured heat sink is found to be roughly two times compared to the smooth heat sinks one. In addition, surface area roughly doubles with regard to smooth heat sinks, due to the presence of micro-fins. Consequently, patterned heat sinks thermal transmittance [W/K] is found to be roughly four times the smooth heat sinks one. We hope this work may open the way for huge boost in the technology of electronic cooling by innovative manufacturing techniques.
Interaction of NO2 with TiO2 surface under UV irradiation: measurements of the uptake coefficient
Directory of Open Access Journals (Sweden)
Y. Bedjanian
2012-01-01
Full Text Available The interaction of NO2 with TiO2 solid films was studied under UV irradiation using a low pressure flow reactor (1–10 Torr combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The NO2 to TiO2 reactive uptake coefficient was measured from the kinetics of NO2 loss on TiO2 coated Pyrex rods as a function of NO2 concentration, irradiance intensity (JNO2 = 0.002–0.012 s?1, relative humidity (RH = 0.06–69 %, temperature (T = 275–320 K and partial pressure of oxygen (0.001–3 Torr. TiO2 surface deactivation upon exposure to NO2 was observed. The initial uptake coefficient of NO2 on illuminated TiO2 surface (with 90 ppb of NO2 and JNO2?0.006 s?1 was found to be ?0 = (1.2±0.4 ×10?4 (calculated using BET surface area under dry conditions at T = 300 K. The steady state uptake, ?, was several tens of times lower than the initial one, independent of relative humidity, and was found to decrease in the presence of molecular oxygen. In addition, it was shown that ? is not linearly dependent on the photon flux and seems to level off under atmospheric conditions. Finally, the following expression for ? was derived, ? = 2.3×10?3 exp(?1910/T/(1 + P0.36 (where P is O2 pressure in Torr, and recommended for atmospheric applications (for any RH, near 90 ppb of NO2 and JNO2 = 0.006 s?1.
Heat emission in water film streaming down along heat transferring surface at air contact
International Nuclear Information System (INIS)
The results of heat emission study in turbulent water film, transporting along the hydraulically smooth heat transferring pipe surface by the air flow are presented. Effect of liquid drops teared off the film surface on the coolant final temperature resulting from moisture and drops evaporation from the film surface and its renewal is established. The dependences for the heat emission factor calculation are given
Lewandowska, Monika; Herzog, Robert; Malinowski, Leszek
2015-01-01
A heat slug propagation experiment in the final design dual channel ITER TF CICC was performed in the SULTAN test facility at EPFL-CRPP in Villigen PSI. We analyzed the data resulting from this experiment to determine the equivalent transverse heat transfer coefficient hBC between the bundle and the central channel of this cable. In the data analysis we used methods based on the analytical solutions of a problem of transient heat transfer in a dual-channel cable, similar to Renard et al. (2006) and Bottura et al. (2006). The observed experimental and other limits related to these methods are identified and possible modifications proposed. One result from our analysis is that the hBC values obtained with different methods differ by up to a factor of 2. We have also observed that the uncertainties of hBC in both methods considered are much larger than those reported earlier.
Energy Technology Data Exchange (ETDEWEB)
Sieres, Jaime; Fernandez-Seara, Jose [University of Vigo, Area de Maquinas y Motores Termicos, E.T.S. de Ingenieros Industriales, Vigo (Spain)
2008-08-15
The ammonia purification process is critical in ammonia-water absorption refrigeration systems. In this paper, a detailed and a simplified analytical model are presented to characterize the performance of the ammonia rectification process in packed columns. The detailed model is based on mass and energy balances and simultaneous heat and mass transfer equations. The simplified model is derived and compared with the detailed model. The range of applicability of the simplified model is determined. A calculation procedure based on the simplified model is developed to determine the volumetric mass transfer coefficients in the vapour phase from experimental data. Finally, the proposed model and other simple calculation methods found in the general literature are compared. (orig.)
Charge transfer processes of atomic hydrogen Rydberg states near surfaces
Dethlefsen, Mark Georg Bernhard; Softley, Tim
2013-01-01
When approaching a metal surface, the electronic structure of Rydberg atoms or molecules is perturbed by the surface potential and at close enough distances resonant ionisation of the Rydberg electron into the conduction band of the surface can occur. It is possible to interfere in this process and steer the ionisation distance by making use of the polarisability of the Rydberg orbital in the presence of electric fields. The resulting ions from the surface can extracted via electric fields an...
Enhancement of natural convection heat transfer rate by the improved heated surface
International Nuclear Information System (INIS)
The cooling system of water in spent fuel pit without electricity power is developed. The cooling system has a air radiator. The radiator size would be too large, because natural convection heat transfer is low. Therefore, enhancement of natural convection heat transfer is necessary. We applied thermal splay to heated surface, and found that thermal splay enhanced natural convection heat transfer performance. The material of thermal splay is aluminum bronze and polyester powder. Using this result, radiator size could be reduced. (author)
Energy Technology Data Exchange (ETDEWEB)
Wang, Wenbo; He, Xingli; Ye, Zhi, E-mail: yezhi@zju.edu.cn, E-mail: jl2@bolton.ac.uk; Wang, Xiaozhi [Department of Information Science and Electronic Engineering, Zhejiang University and Cyrus Tang Centre for Sensor Materials and Applications, 38 Zheda Road, Hangzhou 310027 (China); Mayrhofer, Patrick M.; Gillinger, Manuel; Bittner, Achim; Schmid, Ulrich [Institute of Sensor and Actuator Systems, Vienna University of Technology, Floragasse, 7/2/366-MST, A-1040 Vienna (Austria); Luo, J. K., E-mail: yezhi@zju.edu.cn, E-mail: jl2@bolton.ac.uk [Institute of Renewable Energy Environmental Technology, University of Bolton, Deane Road, Bolton BL3 5AB (United Kingdom); Department of Information Science and Electronic Engineering, Zhejiang University and Cyrus Tang Centre for Sensor Materials and Applications, 38 Zheda Road, Hangzhou 310027 (China)
2014-09-29
AlN and AlScN thin films with 27% scandium (Sc) were synthesized by DC magnetron sputtering deposition and used to fabricate surface acoustic wave (SAW) devices. Compared with AlN-based devices, the AlScN SAW devices exhibit much better transmission properties. Scandium doping results in electromechanical coupling coefficient, K{sup 2}, in the range of 2.0%???2.2% for a wide normalized thickness range, more than a 300% increase compared to that of AlN-based SAW devices, thus demonstrating the potential applications of AlScN in high frequency resonators, sensors, and high efficiency energy harvesting devices. The coupling coefficients of the present AlScN based SAW devices are much higher than that of the theoretical calculation based on some assumptions for AlScN piezoelectric material properties, implying there is a need for in-depth investigations on the material properties of AlScN.
Second law analysis of heat transfer surfaces in circulating fluidized beds
International Nuclear Information System (INIS)
The correct sizing of the heat transfer surfaces is important to ensure proper operation, load turndown, and optimization of circulating fluidized beds (CFBs). From this point of view, in this study, the thermodynamic second law analysis of heat transfer surfaces in CFBs is investigated theoretically in order to define the parameters that affect the system efficiency. Using a previously developed 2D CFB model which uses the particle-based approach and integrates and simultaneously predicts the hydrodynamics and combustion aspects, second law efficiency and entropy generation values are obtained at different height and volume ratios of the heat transfer surfaces for CFBs. Besides that, the influences of the water flow rates and heat exchanger tube diameters on the second law efficiency are investigated. Through this analysis, the dimensions, arrangement and type of the heat transfer surfaces which achieve maximum efficiency are obtained
Scientific Electronic Library Online (English)
Luis, Patiño; Yordy, González; Antonio, Carmona; José, Valero; Henry, Espinoza.
2008-12-01
Full Text Available Se presenta una metodología teórico-experimental para determinar los coeficientes intersticiales de transferencia de calor promedio en el flujo radial de agua a través de un lecho de empaque de polietileno donde el fluido no está en equilibrio térmico con la fase sólida. Los coeficientes de transfer [...] encia de calor se obtienen a través del Single Blow Transient Method combinando los resultados experimentales en un banco de ensayo con las soluciones numéricas del modelo matemático. El sistema de ecuaciones diferenciales parciales generado en el modelo matemático es resuelto a través de una metodología numérica basada en el método de volúmenes finitos. Las pruebas experimentales y las soluciones numéricas se realizaron para diferentes valores de velocidad superficial del fluido a la entrada del lecho y para diversos valores de porosidad del medio, obteniéndose que los números de Nusselt aumentan al incrementarse el número de Reynolds, y de igual manera, también aumentan al disminuir la porosidad del medio, observándose valores de Nusselt hasta de 2,8 para una porosidad de 0,375 y un número de Reynolds de 650. Abstract in english A numerical-experimental methodology was used for determining interstitial heat transfer coefficients in water flowing through porous media where it was not in heat balance with the solid phase. Heat transfer coefficients were obtained through the single blow transient test method, combining experim [...] ental test equipment results with a mathematical model’s numerical solution. The partial differential equation system produced by the mathematical model was resolved by a numerical finite volume method-based methodology. Experimental tests and numerical solutions were satisfactorily carried out for different values from the fluid’s surface speed from the entrance to the bed and for different porosity values, finding that Nusselt numbers increased when Reynolds numbers also increased and that Nusselt numbers increased when porosity decreased. A 650 Reynolds number and 0.375 porosity gave a Nusselt number of up to 2.8.
Reis, M. L. C. C.; Falcao Filho, J. B. P.; Basso, E.; Caldas, V. R.
2015-02-01
A test campaign of the Brazilian sounding rocket Sonda III was carried out at the Pilot Transonic Wind Tunnel, TTP. The aim of the campaign was to investigate aerodynamic phenomena taking place at the connection region of the first and second stages. Shock and expansion waves are expected at this location causing high gradients in airflow properties around the vehicle. Pressure taps located on the surface of a Sonda III half model measure local static pressures. Other measured parameters were freestream static and total pressures of the airflow. Estimated parameters were pressure coefficients and Mach numbers. Uncertainties associated with the estimated parameters were calculated by employing the Law of Propagation of Uncertainty and the Monte Carlo method. It was found that both uncertainty evaluation methods resulted in similar values. A Computational Fluid Dynamics simulation code was elaborated to help understand the changes in the flow field properties caused by the disturbances.
Observation of orientation-dependent electron transfer in molecule–surface collisions
Bartels, Nils; Golibrzuch, Kai; Bartels, Christof; Chen, Li; Auerbach, Daniel J.; Wodtke, Alec M.; Schäfer, Tim
2013-01-01
How molecules point in space—that is, their spatial orientation—determines how they interact with their environment. Exchange of energy, photons, and particles as well as chemical reactions are all elementary processes that depend on orientation. Electron transfer reactions are of particular interest because of their importance in a remarkably wide range of phenomena. In this work, we examine electron transfer reactions at surfaces, which control the change of oxidation state in surface chemi...
International Nuclear Information System (INIS)
A experiment was conducted to study kinetics, transfer coefficients, and biological half-lives of 90Sr, 134Cs, and 137Cs from feed to milk. A cow was fed a diet containing alfalfa hay contaminated by Chernobyl fallout for 14.5 wk. The time-dependent activity in milk was approximated by a two-compartment model with fast biological half-lives of 2, 0.9, and 1 d and slow biological half-lives of 36.9, 8.7, and 12.4 d for 90Sr, 134Cs, and 137Cs respectively. The transfer coefficients determined in the experiment were 0.0008 d L-1 for 90Sr, 0.0029 d L-1 for 137Cs, and 0.0031 d L-1 for 137Cs. The biological elimination phases of 134Cs and 137Cs were described by a two-compartment model while a one-compartment model was proposed for 90Sr. 18 refs., 4 figs., 2 tabs
International Nuclear Information System (INIS)
The present work focuses on the generation of the flow regime map for two-phase water flow in microchannels of a hydraulic diameter of 140 µm. An image analysis algorithm has been developed and utilized to obtain the local void fraction. The image processing technique is also employed to identify and estimate the percentage of different flow regimes and heat transfer coefficient, as a function of position, heat flux and mass flow rate. Both void fraction and heat transfer coefficient are found to increase monotonically along the length of the microchannel. At low heat flux and low flow rates, bubbly, slug and annular flow regimes are apparent. However, the flow is predominately annular at high heat flux and high flow rate. A breakup of the flow frequency suggests that the flow is bistable in the annular regime, in that at a fixed location, the flow periodically switches from single-phase liquid to annular and vice versa. Otherwise, the occurrence of three regimes—single-phase liquid, bubbly and slug are observed. These results provide several useful insights about two-phase flow in microchannels besides being of fundamental interest
Temma, T.; Baines, K. H.; Butler, R. A. H.; Brown, L. R.; Sagui, L.; Kleiner, I.
2006-01-01
PH3 exponential sum k coefficients were computed between 2750 and 3550/cm (2.82-3.64 (microns), in view of future application to radiative transfer analyses of Jupiter and Saturn in a phosphine absorption band near 3 microns. The temperature and pressure of this data set cover the ranges from 80 to 350 K and from 10 (exp -3)to 10(exp 1) bars, respectively. Transmission uncertainty incurred by the use of the k coefficients is smaller than a few percent as long as the radiation is confined above an altitude of a few bars in the giant planets. In spectral regions of weak absorption at high pressures close to 10 bars, contributions from far wings of strong absorption lines must be carefully taken into account. Our data set helps map the three-dimensional distribution of PH3 on the giant planets, revealing their global atmospheric dynamics extending down to the deep interior. The complete k coefficient data set of this work is available at the Web site of the NASA Planetary Data System Atmospheres Node.
Bacon, D H
2013-01-01
Basic Heat Transfer aims to help readers use a computer to solve heat transfer problems and to promote greater understanding by changing data values and observing the effects, which are necessary in design and optimization calculations.The book is concerned with applications including insulation and heating in buildings and pipes, temperature distributions in solids for steady state and transient conditions, the determination of surface heat transfer coefficients for convection in various situations, radiation heat transfer in grey body problems, the use of finned surfaces, and simple heat exc
Condensation heat transfer enhancement by surface modification on a monolithic copper heat sink
International Nuclear Information System (INIS)
In this study, the condensation heat transfer performance on a pure copper surface, as well as a superhydrophobic-modified copper surface were compared. Differing from other condensation heat transfer experimental designs, a monolithic copper heat sink was utilized in this study to prevent contact thermal resistance and/or thermal conduction limitation of the thermal paste applied between the modified condensation surface and heat sink plate. This approach has not yet been documented in the literature. The superhydrophobic copper heat sink surface was prepared using a hydrogen peroxide immersion and fluorosilane polymer (EGC-1720) spin-coating. Experimental results show that the condensation heat transfer performance on the superhydrophobic copper surface is superior to that of a pure copper surface. Additionally, durability tests of the pure and superhydrophobic coating copper surfaces in a harsh vapor environment are discussed in this study. - Highlights: • Superhydrophobic surface modification is applied to a monolithic copper heat sink. • A monolithic copper heat sink is used to prevent contact thermal resistance. • EGC-1720 fluorosilane polymer is employed as the waterproof agent. • Durability of the EGC-1720 coated surface is investigated. • The relative heat transfer enhancement of the heat sink is compared
Magnetohydrodynamic flow and mass transfer of a Jeffery fluid over a nonlinear stretching surface
Energy Technology Data Exchange (ETDEWEB)
Hayat, Tasawar; Qasim, Muhammad [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; Abbas, Zaheer [International Islamic Univ., Islamabad (Pakistan). Dept. of Mathematics; Hendi, Awatif A. [Dept. of Physics, Riyadh (Saudi Arabia). Faculty of Science
2010-12-15
This paper investigates the magnetohydrodynamic (MHD) boundary layer flow of a Jeffery fluid induced by a nonlinearly stretching sheet with mass transfer. The relevant system of partial differential equations has been reduced into ordinary differential equations by employing the similarity transformation. Series solutions of velocity and concentration fields are developed by using the homotopy analysis method (HAM). Effects of the various parameters such as Hartman number, Schmidt number, and chemical reaction parameter on velocity and concentration fields are discussed by presenting graphs. Numerical values of the mass transfer coefficient are also tabulated and analyzed. (orig.)
Czech Academy of Sciences Publication Activity Database
Fialová, Marie; Orvalho, Sandra; Zedníková, Mária; Drahoš, Ji?í; R?ži?ka, Marek
Praha : Process Engineering Publisher, 2010, s. 1031. ISBN 978-80-02-02248-0. [International Congress of Chemical and Process Engineering CHISA 2010 and 7th European Congress of Chemical Engineering ECCE-7 /19./. Prague (CZ), 28.08.2010-01.09.2010] R&D Projects: GA ?R GA104/07/1110 Institutional research plan: CEZ:AV0Z40720504 Keywords : gas holdup * volumetric mass transfer * bubble column Subject RIV: CI - Industrial Chemistry, Chemical Engineering www.chisa.cz/2010, www.ecce7.com
International Nuclear Information System (INIS)
The stainless steel tube used for the experiments is heated by means of d.c current; its inside diameter is 40 mm; its length is about 5.80 meters. Special core has been taken (heated rocket) to avoid heat loss and to provide very accurate measurements. The cooling gases tested are air and carbon dioxide at a pressure of 2.6 to 19 psi; the Reynolds number ranges from 70,000 to 106, the wall temperature and the heat flux reach respectively 430 deg C and 16 watts/cm2. The Reynolds number Rem, Stanton number Mm and friction coefficient f are computed by evaluating the physical properties of the gases at the mean temperature Tm. For a given Reynolds number, a decrease of Mm and of f is observed hen the heat flux increases, this decrease reaches 10 per cent in the experiments described. A formulation is proposed to express this effect in terms of a heat flow parameter (Tm - Tm) / Tp used as a corrective factor (Tp = wall temperature). The correlation formulae are: Mm = 0.0168 Rem-0.18 Pm-0.6 (1 - 0.4 [(Tp - Tm) / Tp]) for air f = f0 (1 0.25 [(Tp - Tm) / Tp]) for air Mm = 0.0171 Rem-0.18 Pm-0.6 (1 - 0.2 [(Tp - Tm) / Tp]) for carbon dioxide f = f0 (1 - 0.20 [(Tp - Tm) / Tp]) for carbon dioxide where f0 = the friction coefficient for isotherm flow. (author)
International Nuclear Information System (INIS)
The objective of this study was to compile data, based on an extensive literature survey, for the soil solid-liquid distribution coefficient (Kd) and soil-to-plant transfer factor (TF) for nickel. The Kd best estimates were calculated for soils grouped according to texture and organic matter content (sand, loam, clay and organic) and soil cofactors affecting soil-nickel interaction, such as pH, organic matter, and clay content. Variability in Kd was better explained by pH than by soil texture. Nickel TF estimates were presented for major crop groups (cereals, leafy vegetables, non-leafy vegetables, root crops, tubers, fruits, herbs, pastures/grasses and fodder), and also for plant compartments within crop groups. Transfer factors were also calculated per soil group, as defined by their texture and organic matter content. Furthermore an evaluation of transfer factor dependency on specific soil characteristics was performed following regression analysis. The derived estimates were compared with parameter estimates currently in use
Energy Technology Data Exchange (ETDEWEB)
Fradera, J.; Sedano, L.; Mas de les Valls, E.; Batet, L.
2010-07-01
High helium (He) production rates support the conditions for He nucleation in liquid metal (LM) breeding blankets. The formation of bubbles in the LM might have an important impact on the hydrodynamics and on the tritium transport. The issue of He bubbles formation is, hence, highly relevant to tritium inventory control and recovery. Models for tritium and helium transport phenomena involving He nucleation, bubble growth, T absorption into He bubbles, T adsorption onto structural material and desorption to cooling system channels (CSC) are implemented into OpenFOAM CFD code (BelFoam solver). The code is capable of solving the mass transfer between different materials with a conjugated scalar transfer algorithm, so it takes into account LM-structural material interface T transport. In the present work, BelFoam solver results for a geometrically simplified horizontalU-bent channel of a helium cooled lithiumlead (HCLL) breeding unit (BU) are shown. In addition, for the T absortion model, a sensitivity analysis to the mass transfer coefficient is presented together with an analysis of the results.
International Nuclear Information System (INIS)
High helium (He) production rates support the conditions for He nucleation in liquid metal (LM) breeding blankets. The formation of bubbles in the LM might have an important impact on the hydrodynamics and on the tritium transport. The issue of He bubbles formation is, hence, highly relevant to tritium inventory control and recovery. Models for tritium and helium transport phenomena involving He nucleation, bubble growth, T absorption into He bubbles, T adsorption onto structural material and desorption to cooling system channels (CSC) are implemented into OpenFOAM CFD code (BelFoam solver). The code is capable of solving the mass transfer between different materials with a conjugated scalar transfer algorithm, so it takes into account LM-structural material interface T transport. In the present work, BelFoam solver results for a geometrically simplified horizontalU-bent channel of a helium cooled lithiumlead (HCLL) breeding unit (BU) are shown. In addition, for the T absortion model, a sensitivity analysis to the mass transfer coefficient is presented together with an analysis of the results.
International Nuclear Information System (INIS)
Three-dimensional heat transfer characteristics and pressure drop of water flow in a set of rectangular microchannels are numerically investigated using Fluent and compared with those of experimental results. Two metamodels based on the evolved group method of data handling (GMDH) type neural networks are then obtained for modelling of both pressure drop (?P) and Nusselt number (Nu) with respect to design variables such as geometrical parameters of microchannels, the amount of heat flux and the Reynolds number. Using such obtained polynomial neural networks, multi-objective genetic algorithms (GAs) (non-dominated sorting genetic algorithm, NSGA-II) with a new diversity preserving mechanism is then used for Pareto based optimization of microchannels considering two conflicting objectives such as (?P) and (Nu). It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of microchannels can be discovered by Pareto based multi-objective optimization of the obtained polynomial metamodels representing their heat transfer and flow characteristics. Such important optimal principles would not have been obtained without the use of both GMDH type neural network modelling and the Pareto optimization approach
International Nuclear Information System (INIS)
The transfer coefficient (TF) from soil to rice plants of 134Cs and 137Cs in the form of radioactive deposition from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011 was investigated in three rice paddy fields in Minami-Soma City. Rice crops were planted in the following May and harvested at the end of September. Soil cores of 30-cm depth were sampled from rice-planted paddy fields to measure 134Cs and 137Cs radioactivity at 5-cm intervals. 134Cs and 137Cs radioactivity was also measured in rice ears (rice with chaff), straws and roots. The rice ears were subdivided into chaff, brown rice, polished rice and rice bran, and the 134Cs and 137Cs radioactivity concentration of each plant part was measured to calculate the respective TF from the soil. The TF of roots was highest at 0.48 ± 0.10 in the field where the 40K concentration in the soil core was relatively low, in comparison with TF values of 0.31 and 0.38 in other fields. Similar trends could be found for the TF of whole rice plants, excluding roots. The TF of rice ears was relatively low at 0.019–0.026. The TF of chaff, rice bran, brown rice and polished rice was estimated to be 0.049, 0.10–0.16, 0.013–0.017 and 0.005–0.013, respectively. - Highlights: ? We investigated the transfer coefficient of 134Cs and 137Cs from soil to rice plants in Minami-Soma City dce plants in Minami-Soma City due to the Fukushima accident in 2011. ? The rice ears, straws, roots, chaff, brown rice, polished rice, rice bran and soil samples have been measured by Ge-detector. ? Transfer coefficient of chaff, rice bran, brown rice, and polished rice is estimated as 0.049, ranging from 0.10 to 0.16, 0.013 to 0.017, and 0.005 to 0.013, respectively.
The role of a convective surface in models of the radiative heat transfer in nanofluids
International Nuclear Information System (INIS)
Highlights: • The role of a convective surface in modelling with nanofluids is investigated over a wedge. • Surface convection significantly controls the rate of heat transfer in nanofluid. • Increased volume fraction of nanoparticles to the base-fluid may not always increase the rate of heat transfer. • Effect of nanoparticles solid volume fraction depends on the types of constitutive materials. • Higher heat transfer in nanofluids is found in a moving wedge rather than in a static wedge. - Abstract: Nanotechnology becomes the core of the 21st century. Nanofluids are important class of fluids which help advancing nanotechnology in various ways. Convection in nanofluids plays a key role in enhancing the rate of heat transfer either for heating or cooling nanodevices. In this paper, we investigate theoretically the role of a convective surface on the heat transfer characteristics of water-based nanofluids over a static or moving wedge in the presence of thermal radiation. Three different types of nanoparticles, namely copper Cu, alumina Al2O3 and titanium dioxide TiO2 are considered in preparation of nanofluids. The governing nonlinear partial differential equations are made dimensionless with the similarity transformations. Numerical simulations are carried out through the very robust computer algebra software MAPLE 13 to investigate the effects of various pertinent parameters on the flow field. The obtained results presented graphically as well as in tabular form and discussed from physical and engineering points of view. The results show that the rate of heat transfer in a nanofluid in the presence of thermal radiation significantly depends on the surface convection parameter. If the hot fluid side surface convection resistance is lower than the cold fluid side surface convection resistance, then increased volume fraction of the nanoparticles to the base fluid may reduces the heat transfer rate rather than increases from the surface of the wedge to the nanofluid. This finding is new and has not been reported in any open literature
International Nuclear Information System (INIS)
Highlights: • The model of hydrogen isotopes desorption from lead lithium alloy in packed column is presented. • Mass transfer coefficient kLa are evaluated from Alpy's Melodie loop experiments. • Packing height and efficiency of packed columns in DEMO plant for DCLL and HCLL are evaluated. • Effects of liquid phase axial dispersion, surface tension and wettability of packing are evaluated. • Effect of flow rate of the purge gas on packing height and desorption efficiency is evaluated. - Abstract: The model of the desorption of hydrogen isotopes from lead lithium alloy in a packed column is derived from the first principles using the plug flow in the liquid phase either the plug flow or ideal mixing in the gas phases. Sievert's law of non-linear equilibrium is followed. The volumetric mass transfer coefficient kLa and its dependence on the liquid metal flow rate are evaluated on the basis of the Melodie loop experiments. The presented model is used for evaluation of the minimum flow rate of the purge gas for which the concentration of the isotope in the gas leaving the column is at its highest, while the driving force of the interfacial transport of the isotope is still not reduced and the tritium desorption efficiency is therefore retained. The potential effect of the axial dispersion in the gas and liquid phase is evaluated. Highlighted are the issues of the optimum packing geometric surface area, above which the efficiency starts to decrease, and of the role of the surface tension and the contact angle with regard to the wettability of the packing. On the basis of the findings related to these factors, the Mellapak 500 Y and Mellapak packings with flat surfaces are recommended for the tests aiming to intensify the tritium desorption efficiency in the packed columns. The models were used for the engineering sizing of the packed columns in two breeding blanket concepts for the DEMO plant – utilizing DCLL (dual coolant lead lithium) and HCLL (helium cooled lithium lead)
Scientific Electronic Library Online (English)
Marcos A., Golato; Hugo, Ruiz; Juan F., D`Angelo; Gustavo, Aso; Dora, Paz.
2005-12-01
Full Text Available En la bibliografía consultada no se encontraron trabajos de secado de cáscara de limón en secaderos rotativos. Se realizaron ensayos de medición en secaderos rotativos de cáscara de limón en una instalación agroindustrial del noroeste argentino. Se desarrolló un modelo matemático semiempírico median [...] te la resolución de los balances de materia y energía. Se obtuvo una correlación estadística para la predicción de los coeficientes globales volumétricos de transferencia de calor aparentes para secaderos rotativos de cáscara de limón. Abstract in english No papers on lemon peel drying in rotary dryers were actually found in the sources consulted. Measurement tests were carried out in the assessment of rotary dryer systems used to dehydrate lemon peel in an agroindustrial plant of Northwestern Argentina. A semiempirical mathematic model was developed [...] solving mass and energy balances. A statistical correlation for predicting global heat transfer coefficient in rotary dryer lemon peel dehydration was obtained.
Selig, Stefan; Jacobs, Karl; Schultz, Michael; Honingh, Netty
2014-01-01
In this paper we present the experimental realization of a Nb tunnel junction connected to a high-gap superconducting NbTiN embedding circuit. We investigate relaxation of nonequilibrium quasiparticles in a small volume Au layer between the Nb tunnel junction and the NbTiN circuit. We find a saturation in the effective heat-transfer coefficient consistent with a simple theoretical model. This saturation is determined by the thickness of the Au layer. Our findings are important for the design of the ideal Au energy relaxation layer for practical SIS heterodyne mixers and we suggest two geometries, one, using a circular Au layer and, two, using a half-circular Au layer. Our work is concluded with an outlook of our future experiments.
International Nuclear Information System (INIS)
Measurements of the H-2(d, n)(3) He transverse vector polarization-transfer coefficient K-y(y)' at 0 degrees. are reported for 29 outgoing neutron energies between 3.94 and 8.47MeV. Our new results determine K-y(y)' (0 degrees) more accurately than previous data, especially for neutron energies below 5MeV. Low-energy data for this reaction are important both as a high-intensity source of highly polarized neutrons for nuclear physics studies with polarized neutron beams, and as a test of the emerging theoretical descriptions of the four-body system, where recently substantial progress has been made.
Stevenson, Gareth P; Lee, Chong-Yong; Kennedy, Gareth F; Parkin, Alison; Baker, Ruth E; Gillow, Kathryn; Armstrong, Fraser A; Gavaghan, David J; Bond, Alan M
2012-06-26
A detailed analysis of the cooperative two-electron transfer of surface-confined cytochrome c peroxidase (CcP) in contact with pH 6.0 phosphate buffer solution has been undertaken. This investigation is prompted by the prospect of achieving a richer understanding of this biologically important system via the employment of kinetically sensitive, but background devoid, higher harmonic components available in the large-amplitude Fourier transform ac voltammetric method. Data obtained from the conventional dc cyclic voltammetric method are also provided for comparison. Theoretical considerations based on both ac and dc approaches are presented for cases where reversible or quasi-reversible cooperative two-electron transfer involves variation in the separation of their reversible potentials, including potential inversion (as described previously for solution phase studies), and reversibility of the electrode processes. Comparison is also made with respect to the case of a simultaneous two-electron transfer process that is unlikely to occur in the physiological situation. Theoretical analysis confirms that the ac higher harmonic components provide greater sensitivity to the various mechanistic nuances that can arise in two-electron surface-confined processes. Experimentally, the ac perturbation with amplitude and frequency of 200 mV and 3.88 Hz, respectively, was employed to detect the electron transfer when CcP is confined to the surface of a graphite electrode. Simulations based on cooperative two-electron transfer with the employment of reversible potentials of 0.745 ± 0.010 V, heterogeneous electron transfer rate constants of between 3 and 10 s(-1) and charge transfer coefficients of 0.5 for both processes fitted experimental data for the fifth to eighth ac harmonics. Imperfections in theory-experiment comparison are consistent with kinetic and thermodynamic dispersion and other nonidealities not included in the theory used to model the voltammetry of surface-confined CcP. PMID:22607123
Wilson, E K; Huang, L; Sutcliffe, M J; Mathews, F S; Hille, R; Scrutton, N S
1997-01-01
In wild-type trimethylamine dehydrogenase, tyrosine-442 is located at the center of a concave region on the surface of the enzyme that is proposed to form the docking site for the physiological redox acceptor, electron transferring flavoprotein. The intrinsic rate constant for electron transfer in the reoxidation of one-electron dithionite-reduced wild-type trimethylamine dehydrogenase (modified with phenylhydrazine) by electron transferring flavoprotein was investigated by stopped-flow spectroscopy. Analysis of the temperature dependence of the reaction rate by electron transfer theory yielded values for the reorganizational energy of 1.4 eV and the electronic coupling matrix element of 0.82 cm-1. The role played by residue Tyr-442 in facilitating reduction of ETF by TMADH was investigated by isolating three mutant forms of the enzyme in which Tyr-442 was exchanged for a phenylalanine, leucine, or glycine residue. Rates of electron transfer from these mutants of TMADH to ETF were investigated by stopped-flow spectroscopy. At 25 degrees C, modest reductions in rate were observed for the Y442F (1.4-fold) and Y442L (2.2-fold) mutant complexes, but a substantial decrease in rate (30.5-fold) and an elevated dissociation constant for the complex were seen for the Y442G mutant enzyme. Inspection of the crystal structure of wild-type TMADH reveals that Tyr-442 is positioned along one side of a small cavity on the surface of the enzyme: Val 344, located at the bottom of this cavity, is the closest surface residue to the 4Fe-4S center of TMADH and is likely to be positioned on a major electron transfer pathway to ETF. The reduced electron transfer rates in the mutant complexes are probably brought about by decreases in electronic coupling between the electron transfer donor and acceptor within the complex, either directly or indirectly due to unfavorable change in the orientation of the two proteins with respect to one another. PMID:8993316
International Nuclear Information System (INIS)
This research is aimed for finding out the volumetric mass transfer coefficient of the zeolite particle, ks. The experiment has been conducted using an ion exchange column. The column diameter and length are 4.2 cm and 28 cm, respectively. The experiments have been conducted by flowing in the feed to the ion-exchange column containing zeolite with the varied particle diameters, I.e. 20, 40, 60, 80 and 100 mesh. The feed concentrations of Sr(NO3)2, have been varied, I.e. 100, 250, 450, 550 and 650 ppm, and so have been the flow rates, I.e/ 35, 49, 70, 90 and 105 ml/minute. Samples of the effluents have been taken at certain series of time and subjected to analysis using an Atomic Absorption Spectrophotometer. The analytical data obtained have shown that the mass transfer coefficient of the zeolite particle is predominantly affected by the zeolite structure, in particular is effected by the number of AI atoms that hold the K ions. The analytical result from the above parameters has been presented in the forms of several groups of dimensionless number. The equations obtained are: (kL*dp)/DL 18.902(Re)0,378 (dp/D)0,6972(Co*)0,2667 with a mean error of 7.26%; kS 2240.268(dp/D)1.553; and each of them is valid in range of: Re: 0.182 - 0.856; dp/D: 0.004 - 0.022; Co*: 9.5408x10-5 - 6.2827x10-4
Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim
2015-04-01
Investigation of small scale transfer processes between the ocean and atmosphere in the boundary and its parameterization on the meteorological conditions (wind and surface waves parameters) is very important for weather forecasts modeling [1]. The accuracy of the predictions taking in to account the so named bulk-formulas strongly depends on the quality empirical data. That is why the laboratory modeling sometimes is preferable (see [2]) then in situ measurements for obtaining enough ensembles of the data with a good accuracy in control conditions, first of all in a case of severe conditions (strong winds with intensive wave breaking and sprays generation). In this investigation laboratory modeling was performed on the Thermostratified Wind-Wave Channel of the IAP RAS (see. [3]). Experiments were carried out for the wind speeds up to 18.5 m/s (corresponding the equivalent 10-m wind speed 30 m/s). For the possibility of varying parameters of surface roughness independently on the wind flow a special system basing on the submerged mosquito mesh (cell of 2*2 mm) was used (see [4]). The roughness was controlled by the depth of the mesh installation under the free surface (no waves when the mesh was on the surface and maximum wave amplitude for the maximum depth). So, for each wind speed several cases of the waves parameters were investigated. During experiments a stable stratification of the boundary layer of air flow was obtained. Temperature of the heating air was 33-37 degrees (depending on the reference wind speed), and the water temperature was 14-16 degrees. The Pitote gauge and hotwire were used together for measuring velocity and temperature profiles. Also indirect estimations of the total volume of the phase of sprays were obtained by analyzing hotwire signals errors during droplets hits. Then aerodynamic drag CD and heat transfer Ch coefficients were obtained by profiling method. It was shown that that these parameters are very sensitive to the intensity of the spray of droplets generation, especially heat transfer. The work was supported by RFBR grants (14-05-91767, 14-08-31740, 15-35-20953) and RSF grant 14-17-00667 and by President grant for young scientists MK-3550.2014.5 References: 1. Emanuel, K. A. Sensitivity of tropical cyclones to surface exchange coefficients and a revised steady-state model incorporating eye dynamics // J. Atmos. Sci., 52(22), 3969-3976,1995. 2. Brian K. Haus, Dahai Jeong, Mark A. Donelan, Jun A. Zhang, and Ivan Savelyev Relative rates of sea-air heat transfer and frictional drag in very high winds // GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L07802, doi:10.1029/2009GL042206, 2010 3. Yu. I. Troitskaya, D.A. Sergeev, A.A. Kandaurov, G.A Baidakov, M.A. Vdovin, V.I. Kazakov Laboratory and theoretical modeling of air-sea momentum transfer under severe wind conditions // JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, C00J21, 13 PP., 2012 doi:10.1029/2011JC007778 4. Yu.I.Troitskaya, D.A.Sergeev, A.A.Kandaurov, M.I. Vdovin, A.A. Kandaurov, E.V.Ezhova, S.S.Zilitinkevich Momentum and buoyancy exchange in a turbulent air boundary layer over a wavy water surface. Part 2. Wind wave spectra // Nonlinear. Geoph. Processes, Vol. 20, P. 841-856, 2013.
International Nuclear Information System (INIS)
Pre- and posttest calculations of the NOKO experiments shall be performed with the ATHLET code. ATHLET which is being developed by the Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH is intended to cover in a single code the entire spectrum of loss-of-coolant and transient accidents in Light Water Reactors (LWR). The present work is sponsored by BMBF. The objectives are in detail: the modeling of the emergency condenser and the NOKO test facility; the improvement of the ATHLET condensation model to describe the condensation heat transfer of pure vapors and vapor/non-condensible mixtures in horizontal and inclined tubes in ATHLET; pre- and posttest calculations of selected NOKO experiments. The progress to data is that ATHLET and its pre- and postprocessors are installed on the IBM RISC workstation cluster of the Zentralinstitut fuer Angewandte Mathematik (ZAM) and DEC workstation of the institute. Furtheron an input data set for NOKO has been developed and first calculations have been performed. 11 figs
International Nuclear Information System (INIS)
The topography of rough surfaces is characterized by using a Cantor set structure. Based on this fractal characterization, a model of laminar heat transfer in rough microchannels is developed and analyzed numerically. The effects of the Reynolds number, relative roughness, and fractal dimension on laminar heat transfer are all investigated and discussed. The results indicate that the local Nusselt numbers after the entrance region are no longer constant but tend to experience fluctuation along the rough microchannels. Differing from the smooth microchannels, the average Nusselt number increases nearly linearly with the Reynolds number and is larger than the classical value. For higher values of relative roughness, the flow-over roughness induces flow separation, which plays an enhancement on laminar convective heat transfer. Moreover, the laminar heat transfer in microchannels is also enhanced by roughness with a larger fractal dimension yielding more frequent variation in the surface profile even though at the same relative roughness.
Energy Technology Data Exchange (ETDEWEB)
Chen Yongping, E-mail: ypchen@seu.edu.c [School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096 (China); Fu Panpan; Zhang Chengbin; Shi Mingheng [School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210096 (China)
2010-08-15
The topography of rough surfaces is characterized by using a Cantor set structure. Based on this fractal characterization, a model of laminar heat transfer in rough microchannels is developed and analyzed numerically. The effects of the Reynolds number, relative roughness, and fractal dimension on laminar heat transfer are all investigated and discussed. The results indicate that the local Nusselt numbers after the entrance region are no longer constant but tend to experience fluctuation along the rough microchannels. Differing from the smooth microchannels, the average Nusselt number increases nearly linearly with the Reynolds number and is larger than the classical value. For higher values of relative roughness, the flow-over roughness induces flow separation, which plays an enhancement on laminar convective heat transfer. Moreover, the laminar heat transfer in microchannels is also enhanced by roughness with a larger fractal dimension yielding more frequent variation in the surface profile even though at the same relative roughness.
Convective heat transfer fouling of aqueous solutions on modified surfaces
Janabi, Abdullah K. O. Al-
2011-01-01
The present research study was part of the European project "MEDESOL" entitled "Seawater desalination by innovative solar-powered membrane-distillation system". The project aimed at developing a stand-alone desalination unit to produce fresh water with a maximum of 50 m3/day. Several components such as suitable membrane and efficient solar collectors had to be developed as well as a plate heat exchanger for a maximum life expectancy with least deposition occurrence on its surfaces. The contri...
Effect of Surface Diffusion on Transfer Processes in Heterogeneous Systems.
Czech Academy of Sciences Publication Activity Database
Levdansky, V.V.; Smolík, Ji?í; Moravec, Pavel
2008-01-01
Ro?. 51, 9-10 (2008), s. 2471-2481. ISSN 0017-9310 R&D Projects: GA ?R GA101/05/2214; GA ?R(CZ) GA101/05/2524; GA ?R GA104/07/1093 Institutional research plan: CEZ:AV0Z40720504 Keywords : adsorption * gas flow * surface diffusion Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.894, year: 2008
Microscale Heat Transfer Transduced by Surface Plasmon Resonant Gold Nanoparticles
Roper, D. Keith; Ahn, W; Hoepfner, M.
2007-01-01
Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ?10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation ...
Immersion Condensation on Oil-Infused Heterogeneous Surfaces for Enhanced Heat Transfer
Rong Xiao; Nenad Miljkovic; Ryan Enright; Wang, Evelyn N.
2013-01-01
Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nuc...
Surface energy equation for heat transfer process in a pebble fuel
International Nuclear Information System (INIS)
Highlights: • Steady and transient behaviors of the interfacial heat transfer in a fuel element. • Non-local averaging volume method for deriving the surface energy equation. • The method captures significant physical phenomena of the interfacial heat transfer. • Closure relationships are proposed in order to obtain the temperatures distribution. • The derived average equation represents an upscaling regarding the local description. - Abstract: In this paper the surface energy equation for the heat transfer process (HT) between the mixture of fuel (TRISO particles and graphite matrix) and coating in a fuel pebble is derived. The fuel pebble can be treated as a heterogeneous region (mixture of microspheres and graphite) interacting thermally with the homogeneous region (the coating or cladding). These two regions are separated by a boundary region where the properties and behavior differ from those of the adjoining regions. The methodology applied for deriving the surface energy equation is based on the classical theory on interfacial transport phenomena. The surface energy equation derived in this work is an average equation that represents an upscaling respect to the local description. The regions around the surface where changes in the physical phenomena are important are of the order of microns, in contrast with interfacial mass transfer between phases that may be several molecular diameters. The numerical analysis regarding the application of surface energy equation is presented in this work
Energy Technology Data Exchange (ETDEWEB)
Zheng, Junwei
1999-11-08
Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.
Scientific Electronic Library Online (English)
César-Arnaldo, Cisneros-Ramírez.
2014-08-01
Full Text Available La necesidad de disipar altas densidades de flujo de calor ha llevado a los investigadores y diseñadores a emplear el cambio de fase como mecanismo para lograr tal objetivo y con ello lograr equipos intercambiadores de calor más compactos. En el presente trabajo se realizó un estudio de la bibliográ [...] fica sobre la ebullición en minicanales y microcanales. Para ello se consultaron bibliografías que datan desde los años 90 hasta la actualidad, con lo cual se revelaron los principales parámetros o tópicos que caracterizan a este proceso en minicanales y microcanales. Es así que se abordan los términos minicanales y microcanales, ebullición en flujo forzado y regímenes (mapa) de flujo. Además se presenta un resumen de las ecuaciones para la determinación del coeficiente de traspaso de calor en régimen bifásico (h df). Abstract in english The necessity of transfer high heat flux had led to researchers and designers to use the change of phase in order to get this objective. In this work was made a review in more of seventy sources of information dating since 90´s up to the present, where were revealed the main parameters that characte [...] rize the boiling process in minichanels-microchannels. It deals with terms mini-microchannels, flow boiling and flow pattern map. Also, it is presented a summary of equations used for calculate the two-phase heat transfer coefficient.
Resonance Energy Transfer in Hybrid Devices in the Presence of a Surface
DEFF Research Database (Denmark)
Kopylov, Oleksii; Huck, Alexander
2014-01-01
We have studied room-temperature, nonradiative resonant energy transfer from InGaN/GaN quantum wells to CdSe/ZnS nanocrystals separated by aluminum oxide layers of different thicknesses. Nonradiative energy transfer from the quantum wells to the nanocrystals at separation distances of up to approximately 10 nm was observed. By comparing the carrier dynamics of the quantum wells and the nanocrystals, we found that nonradiative recombination via surface states, generated during dry etching of the wafer, counteracts the nonradiative energy-transfer process to the nanocrystals and therefore decreases the process efficiency.
Heat transfer tests under forced convection conditions with high wettable heater surface
International Nuclear Information System (INIS)
Under forced convection and atmospheric pressure conditions, heat transfer tests were performed using the annulus channel of a heater rod with highly wettable surface. Improvement of boiling heat transfer requires that the cooling liquid can contact the heating surface, or a high-wettability heating surface, even if a vapor bubble layer is generated on the surface. From this point of view, high-wettable heating surface was studied. As oxide semiconductor-coated materials are highly-wettable, we made a TiO2 coated heater rod. TiO2 coated surface has a high-wettability, in terms of contact angle and Leidenfrost temperature. The boiling curve was measured with and without TiO coated surface. The results showed difference between with and without TiO2 coating. TiO2 coating rod showed lower boiling onset heat flux, wider nucleate boiling region and higher critical heat flux than without coating. In summary, high wettablity heater surface produced higher boiling heat transfer characteristics under forced convection conditions. (author)
International Nuclear Information System (INIS)
Highlights: ? New drag law in AIAD model was implemented in a CFD code to simulate the flows in nuclear reactor. ? The problems include the CCFL, hydraulic jump and pressurized thermal shock (PTS). ? The model is able to distinguish the local flow morphologies in frame of the Euler–Euler. ? CFD calculations agree well with the experimental data. - Abstract: This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modeling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model () into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air–water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modeling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler–Euler simulation, the local morphology of the phases has to be considered in the drag model. To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler–Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.
Garcia Gonzalez, Raquel; Verhoef, Anne; Luigi Vidale, Pier; Braud, Isabelle
2012-05-01
This study focuses on the mechanisms underlying water and heat transfer in upper soil layers, and their effects on soil physical prognostic variables and the individual components of the energy balance. The skill of the JULES (Joint UK Environment Simulator) land surface model (LSM) to simulate key soil variables, such as soil moisture content and surface temperature, and fluxes such as evaporation, is investigated. The Richards equation for soil water transfer, as used in most LSMs, was updated by incorporating isothermal and thermal water vapor transfer. The model was tested for three sites representative of semiarid and temperate arid climates: the Jornada site (New Mexico, USA), Griffith site (Australia), and Audubon site (Arizona, USA). Water vapor flux was found to contribute significantly to the water and heat transfer in the upper soil layers. This was mainly due to isothermal vapor diffusion; thermal vapor flux also played a role at the Jornada site just after rainfall events. Inclusion of water vapor flux had an effect on the diurnal evolution of evaporation, soil moisture content, and surface temperature. The incorporation of additional processes, such as water vapor flux among others, into LSMs may improve the coupling between the upper soil layers and the atmosphere, which in turn could increase the reliability of weather and climate predictions.
Bhaskarananda Dasgupta; Pinaky Bhadury
2014-01-01
Plasma Transferred Arc surfacing is a kind of Plasma Transferred Arc Welding process. Plasma Transferred Arc surfacing (PTA) is increasingly used in applications where enhancement of wear, corrosion and heat resistance of materials surface is required. The shape of weld bead geometry affected by the PTA Welding process parameters is an indication of the quality of the weld. In this paper the analysis and optimization of weld bead parameters, during deposition of a Nickel based...
Turner, E. R.; Wilson, M. D.; Hylton, L. D.; Kaufman, R. M.
1985-01-01
Progress in predictive design capabilities for external heat transfer to turbine vanes was summarized. A two dimensional linear cascade (previously used to obtain vane surface heat transfer distributions on nonfilm cooled airfoils) was used to examine the effect of leading edge shower head film cooling on downstream heat transfer. The data were used to develop and evaluate analytical models. Modifications to the two dimensional boundary layer model are described. The results were used to formulate and test an effective viscosity model capable of predicting heat transfer phenomena downstream of the leading edge film cooling array on both the suction and pressure surfaces, with and without mass injection.
Heat transfer enhancement in reflooding process on SUS304 rod with film-coated surface
International Nuclear Information System (INIS)
In this study, the heat transfer enhancement on a thin film-coated surface of SUS304 rod during reflooding process was investigated. The test rod was made of SUS304 with the length of 150mm and the outer diameter of 24mm. A thin film layer was deposited by the vacuum evaporation method on a half-circumference of the rod surface with the thickness of 200 nm. Thermocouples were spot-welded at three positions along the rod both on the coated and un-coated surface separately to measure the transient temperature during reflooding experiments. It was found that the reflooding velocity on the film-coated surfaces was much faster than that on the un-coated surface. In addition, it was found that the minimum film boiling temperature on the film-coated surface is about 50 K higher than that on the un-coated surface. Four kinds of coated film material, i.e. titanium, germanium, zircaloy2 and silicon were tested. Heat transfer enhancement was observed for each rod with the same thickness of the coated film. The effect of the film thickness on the heat transfer enhancement was also discussed. It was indicated that in the range of 0-500nm of the thickness, the thicker the coated film is, the faster the reflooding velocity is. (author)
DEFF Research Database (Denmark)
Fristrup, Charlotte Juel; Jankova Atanasova, Katja
2009-01-01
The initial formation of initiating sites for atom transfer radical polymerization (ATRP) on various polymer surfaces and numerous inorganic and metallic surfaces is elaborated. The subsequent ATRP grafting of a multitude of monomers from such surfaces to generate thin covalently linked polymer coatings is discussed briefly in order to provide a readily accessible survey. The potential for achieving a range of well-defined biofunctionalities, such as inhibition of non-specific fouling, immobilization of biomolecules, separation of proteins, adsorbents for proteins or cells, antibacterial activity, and encapsulation of drugs in particular provided by these surface-grafted polymers is described.
Chantooni, Miran K.; Kolthoff, Izaak M.
1981-01-01
Stability constants, KfLMn+ (in which L = ligand and Mn+ = metal ion), of complexes of sodium, potassium, silver, thallium(I), and barium with dibenzocryptand 2.2.2 were determined at 25°C in water and methanol. Also determined were transfer activity coefficients between methanol and water of two ligands, dibenzocryptand 2.2.2 and 18-crown-6. From these data, transfer activity coefficients of complexes of these two ligands with the above cations have been calculated. For univalent ion complex...
E-transfer of materials surface engineering e-foresight results
Directory of Open Access Journals (Sweden)
A.D. Dobrza?ska-Danikiewicz
2011-12-01
Full Text Available Purpose: The purpose of the paper is to present an innovative concept of e-transfer of tech¬nology e-foresight results concerning materials surface technology, allowing for the practical industrial implementation of the results of materials science-heuristic research using a state-of-art IT technology.Design/methodology/approach: Technology e-transfer is an innovating concept popularised in industry, especially in SMEs, developed in the course of the previously pursued e-foresight research of modern knowledge concerning the priority innovative materials surface technologies and the forecast directions of their development.Findings: Technology e-transfer embracing e-information, e-advisory and e-learning, is an efficient method of disseminating the results of technology e-foresight of materials surface engineering within industry.Research limitations/implications: If technology e-transfer is used in the Open Access mode, anyone, for free and at the same terms, has access to a database on the priority innovative tech¬nologies of materials surface engineering and the anticipated directions of their development, which has a positive effect on the development of a knowledge- and innovation-based economy.Practical implications: The idea of disseminating the results of e-foresight of materials surface engineering by way of technology e-transfer is especially attractive for small- and medium-sized companies lacking the funds required to perform their own research in this scope.Originality/value: The concept of technology e-transfer represents the Authors’ original contribution into the development of Computer Aided Knowledge Management.
Microscale heat transfer in a free jet against a plane surface
Shu, Jian-Jun
2014-01-01
A new two-layer model has been proposed to study microscale heat transfer associated with a developing flow boundary layer. As an example, a cold, microscale film of liquid impinging on an isothermal hot, horizontal surface has been investigated. The boundary layer is divided into two regions: a micro layer at microscale away from the surface and a macro layer at macroscale away from the surface. An approximate solution for the velocity and temperature distributions in the flow along the horizontal surface is developed, which exploits the hydrodynamic similarity solution for microscale film flow. The approximate solution may provide a valuable basis for assessing microscale flow and heat transfer in more complex settings.
Choe, H.; Kays, W. M.; Moffat, R. J.
1976-01-01
Heat transfer behavior was studied in a turbulent boundary layer with full-coverage film cooling through an array of discrete holes and with injection normal to the wall surface. Stanton numbers were measured for a staggered hole pattern with pitch-to-diameter ratios of 5 and 10, an injection mass flux ratio range of 0.1 to 1.0, and a range of Reynolds number 170 thousand to 5 million. Air was used as the working fluid with the mainstream velocity varied from .14 to 33.5 m/sec (30 to 110 ft/sec). The data were taken for secondary injection temperatures equal to the wall temperature and also equal to the mainstream temperature. By use of linear superposition theory, the data may be used to obtain Stanton number as a continuous function of the injectant temperature. The heat transfer coefficient is defined on the basis of a mainstream-to-wall temperature difference. This difinition permits direct comparison of performance between film cooling and transpiration cooling.
Lalande, M; Tissier, J P
1985-06-01
Denaturation of beta-lactoglobulin during heating of milk in a plate heat exchanger has been investigated as an important factor in fouling the heat transfer surface. Using, on one hand, data on chemical composition of deposits obtained from biochemical analysis technics and, on the other hand, kinetic data of beta-Iactoglobulin denaturation, the distribution profile of deposits along the surface and the experimental fouling curves can be adequately predicted. PMID:20568150
Kinetics of conjugative gene transfer on surfaces in granular porous media
Massoudieh, A.; Crain, C.; Lambertini, E.; Nelson, K. E.; Barkouki, T.; L'Amoreaux, P.; Loge, F. J.; Ginn, T. R.
2010-03-01
The transfer of genetic material among bacteria in the environment can occur both in the planktonic and attached state. Given the propensity of organisms to exist in sessile microbial communities in oligotrophic subsurface conditions, and that such conditions typify the subsurface, this study focuses on exploratory modeling of horizontal gene transfer among surface-associated Escherichiacoli in the subsurface. The mathematics so far used to describe the kinetics of conjugation in biofilms are developed largely from experimental observations of planktonic gene transfer, and are absent of lags or plasmid stability that appear experimentally. We develop a model and experimental system to quantify bacterial filtration and gene transfer in the attached state, on granular porous media. We include attachment kinetics described in Nelson et al. (2007) using the filtration theory approach of Nelson and Ginn (2001, 2005) with motility of E. coli described according to Biondi et al. (1998).
Liu, Siyu; Zhao, Ning; Cheng, Zhen; Liu, Hongguang
2015-04-01
Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis.Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00070j
Heat Transfer Measurement and Modeling in Rigid High-Temperature Reusable Surface Insulation Tiles
Daryabeigi, Kamran; Knutson, Jeffrey R.; Cunnington, George R.
2011-01-01
Heat transfer in rigid reusable surface insulations was investigated. Steady-state thermal conductivity measurements in a vacuum were used to determine the combined contribution of radiation and solid conduction components of heat transfer. Thermal conductivity measurements at higher pressures were then used to estimate the effective insulation characteristic length for gas conduction modeling. The thermal conductivity of the insulation can then be estimated at any temperature and pressure in any gaseous media. The methodology was validated by comparing estimated thermal conductivities with published data on a rigid high-temperature silica reusable surface insulation tile. The methodology was also applied to the alumina enhanced thermal barrier tiles. Thermal contact resistance for thermal conductivity measurements on rigid tiles was also investigated. A technique was developed to effectively eliminate thermal contact resistance on the rigid tile s cold-side surface for the thermal conductivity measurements.
Mounsef, Jihane Rahbani; Salameh, Dominique; Louka, Nicolas; Brandam, Cedric; Lteif, Roger
2015-09-20
The aeration is a key factor for Bacillus thuringiensis growth, sporulation and ?-endotoxins production. The objective of our work was to study the effect of aeration on the fermentation kinetics of Bacillus thuringiensis kurstaki (Btk), cultivated in a cereal milling byproduct (CMB) mono-component medium, in order to improve the ?-endotoxins productivity. Aeration conditions were systematically characterized by the volumetric mass transfer coefficient KLa. In the 6% CMB culture medium, different values of the maximal specific oxygen uptake rate were obtained at different values of KLa. For KLa of 7.2h(-1), the growth was inhibited and the sporulation was defective. There was a linear increase of the average specific growth rate and faster sporulation and liberation of spores and ?-endotoxins crystals when KLa was increased between 13.3h(-1) and 65.5h(-1). Similar kinetic was observed in cultures performed at KLa equal to 65.5h(-1) and 106.2h(-1). The highest toxins productivity of 96.1mgL(-1)(h)-1 was obtained in the 9% CMB culture medium for KLa of 102h(-1). It was possible to track the evolution of the bacterial cells between vegetative growth, sporulation and liberation of mature spores by following the variation of the CO2 percent in the effluent gas. PMID:26091772
International Nuclear Information System (INIS)
The lack of published data on the extraction kinetics of Tc(VII) in the system U(VI)/HNO3//TBP/dodecane prompted us to investigate its transport behaviour in detail. The aim was to improve the U(VI)/Tc(VII) separation in the PUREX process. We choose the method of analytical ultracentrifugation to determine the concentration gradient profile, the initial flux density and the integral mass transport for both sides of the unstirred liquid-liquid interface as well as the overall mass transfer coefficients as a function of Tc(VII)-, U(VI)-concentrations and temperature from time-dependent changes of the refractive index gradients. The results were supplemented by comparing the experimental with calculated concentration profiles, obtained by modeling a diffusion-limited extraction process. In some of the investigated systems, the transport at the interface is reaction-limited after phase contact. The determined values of vectorJmax, I, and vector? are discussed in terms of the extraction conditions. (orig.)
Dissolved organic matter in sea spray: a transfer study from marine surface water to aerosols
Directory of Open Access Journals (Sweden)
P. Schmitt-Kopplin
2011-12-01
Full Text Available Atmospheric aerosols impose direct and indirect effects on the climate system, for example, by adsorption of radiation in relation to cloud droplets size, on chemical and organic composition and cloud dynamics. The first step in the formation of primary marine aerosols, i.e., the transfer of dissolved organic matter from the marine surface into the atmosphere was studied, and we present a molecular level description of this phenomenon using high resolution analytical tools (Fourier transform ion cyclotron resonance = FT-ICR MS and NMR. We could experimentally confirm the chemo-selective transfer of natural organic molecules, especially of aliphatic compounds from the surface water into the atmosphere via bubble bursting processes. Transfer from marine surface water to the atmosphere involves a chemical gradient governed by the physicochemical properties of the involved molecules when comparing elemental compositions and differentiating CHO, CHNO, CHOS and CHNOS bearing compounds. Typical chemical fingerprints of concentrated compounds were CHO and CHOS type of molecules, smaller molecules of higher aliphaticity and lower oxygen content and typical surfactants. A non-targeted mass spectrometric analysis of the samples showed that many of these molecules correspond to homologous series of oxo-, hydroxyl-, methoxy-, branched fatty acids and mono-, di- and tricarboxylic acids as well as monoterpenes and sugars. These surface active biomolecules were preferentially transferred from surface water into the atmosphere via bubble bursting processes to form a significant fraction of primary organic aerosols. This way of production of sea spray leaves a specific biological signature of the surface water in the corresponding lower atmosphere that can be transported laterally in the context of global cycling.
Investigation of the strain transfer for surface-attached optical fiber strain sensors
International Nuclear Information System (INIS)
The relation between the component strain and the strain on a surface-attached optical fiber is governed by the effectiveness of shear transfer through the adhesive and the polymeric coating(s) on the optical fiber. A classical shear lag model can predict the strain transfer through a soft layer well. However, experiments showed that the results are unsatisfactory for bare fiber with stiff adhesive case. A 3D-FEM is established to model the strain transfer of a surface-mounted strain sensor and it is verified by experiments. Then, it is used to investigate the influence of four geometric parameters of the adhesive: (1) side width, (2) top thickness, (3) bond length, (4) bottom thickness, on the strain transfer. By sensitivity analysis, it is revealed that the bond length and the bottom thickness are dominant factors. Based on finite element results, the parameter of the analytical model is modified to suit stiff layer cases. Important considerations for practical installation of surface-attached optical interferometric and FBG strain sensors will be discussed
Li, Juan; Hong, Cheng-Yi; Wu, Shu-Xian; Liang, Hong; Wang, Li-Ping; Huang, Guoming; Chen, Xian; Yang, Huang-Hao; Shangguan, Dihua; Tan, Weihong
2015-09-01
Hydrophobic nanoparticles have shown substantial potential for bioanalysis and biomedical applications. However, their use is hindered by complex phase transfer and inefficient surface modification. This paper reports a facile and universal strategy for phase transfer and surface biofunctionalization of hydrophobic nanomaterials using aptamer-pendant DNA tetrahedron nanostructures (Apt-tet). The Janus DNA tetrahedron nanostructures are constructed by three carboxyl group modified DNA strands and one aptamer sequence. The pendant linear sequence is an aptamer, in this case AS1411, known to specifically bind nucleolin, typically overexpressed on the plasma membranes of tumor cells. The incorporation of the aptamers adds targeting ability and also enhances intracellular uptake. Phase-transfer efficiency using Apt-tet is much higher than that achieved using single-stranded DNA. In addition, the DNA tetrahedron nanostructures can be programmed to permit the incorporation of other functional nucleic acids, such as DNAzymes, siRNA, or antisense DNA, allowing, in turn, the construction of promising theranostic nanoagents for bioanalysis and biomedical applications. Given these unique features, we believe that our strategy of surface modification and functionalization may become a new paradigm in phase-transfer-agent design and further expand biomedical applications of hydrophobic nanomaterials. PMID:26302208
Aerodynamic losses and surface heat transfer in a strut/endwall intersection flow
Campbell, Bryan Thomas
This thesis presents the results of an investigation into aerodynamic losses and surface heat transfer of a strut/endwall intersection flow field. This type of geometry is prevalent in many aerospace applications, such as wing/body junctions on aircraft, rotor/stator blades in turbomachinery and support struts in turbofan bypass ducts. The changes in aerodynamic drag and surface heat transfer due to the presence of this geometry are of interest to aerospace companies seeking small improvements in performance which contribute to large reductions in operating costs over the lifetime of a product. Aerodynamic losses (i.e. drag) were evaluated from flow-field data obtained with a seven-hole pressure probe using loss equations derived from a control-volume analysis of the integral conservation equations. In addition, a methodology was developed for this type of flow field that allows separation of losses into inviscid and viscous contributions. Strut profile drag, total drag and interference drag were computed for the strut/endwall intersection geometry and compare favorably with previous results. The endwall heat transfer of the strut/endwall intersection was measured using a new heat transfer measurement system that was developed for this research. This system is an expansion of the laser-scanning Temperature Sensitive Paint technique. Results from transition detection and impinging jet experiments conducted during system development are also reported. A map of endwall convective heat transfer in the leading edge region of the strut is presented. The endwall heat transfer results are similar to those found in other investigations of endwall heat transfer for the strut/endwall geometry.
Nature of the bonding, surface relaxation and charge transfer of Au dimmers on an MgO(100) surface
Scientific Electronic Library Online (English)
C, Quintanar; R, Caballero; J, Ulises Reveles; S.N., Khanna.
2012-02-01
Full Text Available First principles electronic structure investigations of the nature of adsorption, relaxation of the atoms near the adsorption site, and the charging of the Au2 particle on the relaxed-rumpled MgO(100) surface have been carried out within the density functional theory-cluster-embedding approach. The [...] investigations focus on an Au2 molecule, perpendicular to the surface, adsorbed at different locations. Three bonding sites are studied: a five coordinated oxygen regular terrace site O5c, an Fs neutral color center (two electrons in an O vacancy), and an F+s positive charged color center (one electron in an O vacancy). The studies indicate that large relaxation of the neighboring atoms and large charge transfer occurs for an Au2 over the color centers. An analysis of the one-electron energy levels of the Au dimer, the MgO surface and the Au2MgO(100) complex for each absorption site allows us to rationalize the nature of the bonding, surface relaxation, calculated absorption and dimerization energies and electron charge transfers.
International Nuclear Information System (INIS)
On the basis of a set of boundary conditions describing quite generally mass and energy transport processes across the free surface of helium II, the acoustic coefficients of reflection, transmission, and transformation of first sound, second sound, and the sound wave propagating in the vapor are calculated in the case of perpendicular incidence of sound waves against the liquid--vapor phase boundary. Considering rigoroulsy the influences of the Onsager surface coefficients, the isobaric thermal expansion coefficients, and the thermal conductivities of the liquid and the vapor, we derive sets of equations from which the acoustic coefficients are determined numerically. For estimations, simple explicit formulas of the acoustic coefficients are given. It is shown that the evaporation and energy transport processes occurring at the free surface of helium II due to the incidence of sound waves may be connected with appreciable energy dissipation. The surface absorption coefficients of first, second, and gas sound waves are deduced
Dynamical interaction of He atoms with metal surfaces: Charge transfer processes
International Nuclear Information System (INIS)
A self-consistent Kohn-Sham LCAO method is presented to calculate the charge transfer processes between a He*-atom and metal surfaces. Intra-atomic correlation effects are taken into account by considering independently each single He-orbital and by combining the different charge transfer processes into a set of dynamical rate equations for the different ion charge fractions. Our discussion reproduces qualitatively the experimental evidence and gives strong support to the method presented here. (author). 24 refs, 4 figs
Numerical study of 2D heat transfer in a scraped surface heat exchanger
Sun, KH; Pyle, DL; Fitt, AD; Please, CP; Baines, MJ; Hall-Taylor, N
2004-01-01
A numerical study of fluid mechanics and heat transfer in a scraped surface heat exchanger with non-Newtonian power law fluids is undertaken. Numerical results are generated for 2D steady-state conditions using finite element methods. The effect of blade design and material properties, and especially the independent effects of shear thinning and heat thinning on the flow and heat transfer, are studied. The results show that the gaps at the root of the blades, where the blades are connected to...
Pratte, Zoe A; Richardson, Laurie L; Mills, DeEtta K
2015-02-01
Bacteria associated with the surface mucopolysaccharide layer (SML) of corals have been proposed to be paramount to coral health, and are occasionally studied in aquaria. Using automated ribosomal intergenic spacer analysis (ARISA), this study examined the temporal changes in the SML microbiota of coral fragments (Siderastrea siderea) transferred from the reef to aquaria. In total, 460 amplicon peaks were detected, 155 of which were unique. Extensive microbiota shifts occurred one day after transfer, with stabilization between 14 and 28days. These results suggest that studies examining coral in laboratory settings should consider the observed temporal dynamics in the SML microbiota. PMID:25553581
Directory of Open Access Journals (Sweden)
Elsayed M. A Elbashbeshy
2011-01-01
Full Text Available The effects of thermal radiation and heat transfer over an unsteady stretching surface embedded in a porous medium in the presence of heat source or sink are studied. The governing time dependent boundary layer equations are transformed to ordinary differential equations containing radiation parameter, permeability parameter, heat source or sink parameter, Prandtl number, and unsteadiness parameter. These equations are solved numerically by applying Nachtsheim-Swinger shooting iteration technique together with Rung-Kutta fourth order integration scheme. The velocity profiles, temperature profiles, the skin friction coefficient, and the rate of heat transfer are computed and discussed in details for various values of the different parameters. Comparison of the obtained numerical results is made with previously published results.
Flow measurements for establishing the mechanisms of heat transfer from a rib-roughened surface
International Nuclear Information System (INIS)
Measurements are presented of the velocity and static pressure distribution in the flow around the roughness elements of a rib-roughened surface, similar to that used for the fuel cladding in Advanced Gas-Cooled Reactors. The data were obtained in a wind-tunnel on a large-scale two-dimensional simulation of the rough surface using a cylindrical pressure probe. The momentum balance in the tunnel is discussed and the effective rough wall shear-stress evaluated from the pressure distribution around the ribs. This enables the inter-rib velocities in the tunnel to be related to the friction velocity and hence to the flow in the reactor. The data have been analysed by computer so that the two components of mean velocity, all three independent velocity gradients, and the convective terms in momentum equation, could be evaluated on a fine mesh covering the flow region. These data are stored on tape for use in future heat transfer calculations. The eventual aim is to optimize the heat transfer performance of rough surfaces from a knowledge of the interaction between the several complex flow regimes which have been identified. The presence of high turbulence intensities close to the inter-rib surface, where the flow would normally be considered laminar, is an important feature of the heat transfer performance. (author)
NU Rahman; Shawahna, R.
2011-01-01
Background and the purpose of the study: Partition coefficients (log D and log P) and molecular surface area (PSA) are potential predictors of the intestinal permeability of drugs. The aim of this investigation was to evaluate and compare these intestinal permeability indicators. Methods: Aqueous solubility data were obtained from literature or calculated using ACD/Labs and ALOGPS. Permeability data were predicted based on log P, log D at pH 6.0 (log D6.0), and PSA. Resul...
Directory of Open Access Journals (Sweden)
Shutthanandan V
2008-06-01
Full Text Available Abstract Molybdenum disulfide (MoS2, a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia. The present work was performed to understand thermal oxidation and metal-insertion processes of molybdenite surfaces. The analysis was performed using atomic force microscopy (AFM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, Rutherford backscattering spectrometry (RBS, and nuclear reaction analysis (NRA. Structural studies using SEM and TEM indicate the local-disordering of the structure as a result of charge-transfer process between the inserted lithium and the molybdenite layer. Selected area electron diffraction measurements indicate the large variations in the diffusivity of lithium confirming that the charge-transfer is different along and perpendicular to the layers in molybdenite. Thermal heating of molybenite surface in air at 400°C induces surface oxidation, which is slow during the first hour of heating and then increases significantly. The SEM results indicate that the crystals formed on the molybdenite surface as a result of thermal oxidation exhibit regular thin-elongated shape. The average size and density of the crystals on the surface is dependent on the time of annealing; smaller size and high density during the first one-hour and significant increase in size associated with a decrease in density with further annealing.
Jin, Zhonghai; Charlock, Thomas P.; Rutledge, Ken; Knut Stamnes; Wang, Yingjian
2006-01-01
Using the efficient discrete-ordinate method, we present an analytical solution for radiative transfer in the coupled atmosphere-ocean system with rough air-water interface. The theoretical formulations of the radiative transfer equation and solution are described. The effects of surface roughness on radiation field in the atmosphere and ocean are studied and compared with measurements. The results show that ocean surface roughness has significant effects on the upwelling radiation in the atmosphere and the downwelling radiation in the ocean. As wind speed increases, the angular domain of sunglint broadens, the surface albedo decreases, and the transmission to ocean increases. The downward radiance field in the upper ocean is highly anisotropic, but this anisotropy decreases rapidly as surface wind increases and as depth in ocean increases. The effects of surface roughness on radiation also depend greatly on both wavelength and angle of incidence (i.e., solar elevation); these effects are significantly smaller throughout the spectrum at high sun. The model-observation discrepancies may indicate that the Cox-Munk surface roughness model is not sufficient for high wind conditions.
Werfelli, Ghofran; Halvick, Philippe; Honvault, Pascal; Kerkeni, Boutheïna; Stoecklin, Thierry
2015-09-01
The observed abundances of the methylidyne cation, CH+, in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH+ in the interstellar medium with the most abundant species H, H2, and e-. In this work, we address the destruction process of CH+ by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potential energy surface including a realistic model of the long-range interaction between the reactants H and CH+. The calculated thermal rate coefficient is in good agreement with the experimental data in the range 50 K-800 K. However, at lower temperatures, the experimental rate coefficient takes exceedingly small values which are not reproduced by the calculated rate coefficient. Instead, the latter rate coefficient is close to the one given by the Langevin capture model, as expected for a reaction involving an ion and a neutral species. Several recent theoretical works have reported a seemingly good agreement with the experiment below 50 K, but an analysis of these works show that they are based on potential energy surfaces with incorrect long-range behavior. The experimental results were explained by a loss of reactivity of the lowest rotational states of the reactant; however, the quantum scattering calculations show the opposite, namely, a reactivity enhancement with rotational excitation.
Catena, Robert D; Xu, Xu
2015-09-01
We previously studied balance during lateral load transfers, but were left without explanation of why some individuals were successful in novel low friction conditions and others were not. Here, we retrospectively examined lower extremity kinematics between successful (SL) and unsuccessful (UL) groups to determine what characteristics may improve low friction performance. Success versus failure over a novel slippery surface was used to dichotomise 35 healthy working-age individuals into the two groups (SL and UL). Participants performed lateral load transfers over three sequential surface conditions: high friction, novel low friction, and practiced low friction. The UL group used a wide stance with rotation mostly at the hips during the high and novel low friction conditions. To successfully complete the practiced low friction task, they narrowed their stance and pivoted both feet and torso towards the direction of the load, similar to the SL group in all conditions. This successful kinematic method potentially results in reduced muscle demand throughout the task. Practitioner Summary: The reason for this paper is to retrospectively examine the different load transfer strategies that are used in a low friction lateral load transfer. We found stance width to be the major source of success, while sagittal plane motion was altered to potentially maintain balance. PMID:25782076
Bhandari, Satyapriya; Roy, Shilaj; Pramanik, Sabyasachi; Chattopadhyay, Arun
2014-09-01
Chemical reaction between oleate-capped Zn(x)Cd(1-x)S quantum dots (Qdots) and 8-hydroxyquinoline (HQ) led to formation of a surface complex, which was accompanied by transfer of hydrophobic Qdots from nonpolar (hexane) to polar (water) medium with high efficiency. The stability of the complex on the surface was achieved via involvement of dangling sulfide bonds. Moreover, the transferred hydrophilic Qdots--herein called as quantum dot complex (QDC)--exhibited new and superior optical properties in comparison to bare inorganic complexes with retention of the dimension and core structure of the Qdots. Finally, the new and superior optical properties of water-soluble QDC make them potentially useful for biological--in addition to light emitting device (LED)--applications. PMID:25133937
Infrared Low-Temperature Turbine Vane Rough Surface Heat Transfer Measurements
Boyle, R. J.; Spuckler, C. M.; Lucci, B. L.; Camperchioli, W. P.
2001-01-01
Turbine vane heat transfer distributions obtained using an infrared camera technique are described. Infrared thermography was used because noncontact surface temperature measurements were desired. Surface temperatures were 80 C or less. Tests were conducted in a three-vane linear cascade, with inlet pressures between 0.14 and 1.02 atm, and exit Mach numbers of 0.3, 0.7, and 0.9, for turbulence intensities of approximately 1 and 10 percent. Measurements were taken on the vane suction side, and on the pressure side leading edge region. The designs for both the vane and test facility are discussed. The approach used to account for conduction within the vane is described. Midspan heat transfer distributions are given for the range of test conditions.
Forced convection heat transfer from heated surface in a cavity formed by two high ribs
International Nuclear Information System (INIS)
The work under consideration is devoted to experimental study on forced convection heat transfer from heated surface between two high ribs. Great attention is paid to the flow visual picture. The experiments were carried out in the channel of a subsonic aerodynamic tube with 200x200 mm cross section. Ribs of material with low heat conductivity (organic glass) 3 mm thick were located at the channel lower wall. The ribs were of similar height (h=60 mm) and the distance between them was equal to L/h=1; 2; 3 calibers. The most interesting fact from practical point of view is that average heat transfer between the ribs appeared to be by 1.5-3 times lower as compared to streamlining smooth surface
Local structures in polyhedral maps on surfaces, and path transferability of graphs
Torii, Ryuzo
2009-01-01
We extend Jendrol' and Skupie\\'n's results about the local structure of maps on the 2-sphere: In this paper we show that if a polyhedral map $G$ on a surface $\\M$ of Euler characteristic $\\chi (\\M) \\le 0$ has more than $126|\\chi (\\M)|$ vertices, then $G$ has a vertex with "nearly" non-negative combinatorial curvature. As a corollary of this, we can deduce that path transferability of such graphs are at most 12.
The dynamics of energy transfer in hyperthermal energy ion scattering from metal surfaces
International Nuclear Information System (INIS)
I have studied the interaction potential, energy transfer, and trapping for Na+ scattering from a clean Cu(001) surface at incident energies ranging from 10 eV to 100 eV. Excellent agreement with the measured energy- an angle-resolved ion scattering distributions is achieved with simulations using a scattering potential consisting of a sum of Hartree-Fock (Na-Cu)+ pair potentials and an additional attrative potential to account for the classical image interaction. From these simulations detailed information about the scattering dynamics is extracted, such as the scattering trajectories, and energy transfer and trapping mechanisms. For energies below 100 eV we find that these quantities are particularly sensitive to the attractive well in the potential: the scattered angular distribution broaden, the fractional energy transfer increases, and the onset of trapping of the scattered flux is observed. The trajectories and energy transfer mechanisms leading to the trapping, and their dependence on incident energy are discussed. Differences between the energy and angular distributions that are consistent with a simple model in which the scattered Na+, unlike the Na degrees, is decelerated by the attractive well. Evidence for trajectory dependent neutralization is also presented and discussed. I have also studied the width of the peak in the energy spectra corresponding to single collisions between the ion and a CU surface atom for 50 eV to 400 eV Na+ and 200 eV K+ scattering. The width has been measured as a function of surface temperature, scattering geometry, and incident energy. The width, which is dominated by the momentum fluctuations of the surface atom, is in excellent agreement with a rigorous semiclassical calculation at high temperatures. At temperatures below the Debye temperature the zero point motion of the atom increases the peak width. I have observed evidence of this behavior at Ts < 200K
Zhu, Tingju; Marques, Guilherme Fernandes; Lund, Jay R.
2015-05-01
Efficient reallocation and conjunctive operation of existing water supplies is gaining importance as demands grow, competitions among users intensify, and new supplies become more costly. This paper analyzes the roles and benefits of conjunctive use of surface water and groundwater and market-based water transfers in an integrated regional water system where agricultural and urban water users coordinate supply and demand management based on supply reliability and economic values of water. Agricultural users optimize land and water use for annual and perennial crops to maximize farm income, while urban users choose short-term and long-term water conservation actions to maintain reliability and minimize costs. The temporal order of these decisions is represented in a two-stage optimization that maximizes the net expected benefits of crop production, urban conservation and water management including conjunctive use and water transfers. Long-term decisions are in the first stage and short-term decisions are in a second stage based on probabilities of water availability events. Analytical and numerical analyses are made. Results show that conjunctive use and water transfers can substantially stabilize farmer's income and reduce system costs by reducing expensive urban water conservation or construction. Water transfers can equalize marginal values of water across users, while conjunctive use minimizes water marginal value differences in time. Model results are useful for exploring the integration of different water demands and supplies through water transfers, conjunctive use, and conservation, providing valuable insights for improving system management.
Directory of Open Access Journals (Sweden)
Cleide M. D. P. da S. e Silva
2012-04-01
Full Text Available In this article, a methodology is used for the simultaneous determination of the effective diffusivity and the convective mass transfer coefficient in porous solids, which can be considered as an infinite cylinder during drying. Two models are used for optimization and drying simulation: model 1 (constant volume and diffusivity, with equilibrium boundary condition, and model 2 (constant volume and diffusivity with convective boundary condition. Optimization algorithms based on the inverse method were coupled to the analytical solutions, and these solutions can be adjusted to experimental data of the drying kinetics. An application of optimization methodology was made to describe the drying kinetics of whole bananas, using experimental data available in the literature. The statistical indicators enable to affirm that the solution of diffusion equation with convective boundary condition generates results superior than those with the equilibrium boundary condition.Neste artigo, é usada uma metodologia para a determinação simultânea da difusividade efetiva e do coeficiente de transferência convectivo de massa em sólidos porosos que possam ser considerados como um cilindro infinito, durante sua secagem. Dois modelos são utilizados para a otimização e a simulação do processo de secagem: o modelo 1 (volume e difusividade constantes, com condição de contorno de equilíbrio; e o modelo 2 (volume e difusividade constantes, com condição de contorno convectiva. Algoritmos de otimização por varredura, baseados no método inverso, foram acoplados às soluções analíticas referentes aos dois modelos utilizados, possibilitando ajustar tais soluções aos dados experimentais da cinética de secagem em camada fina de produtos com a forma cilíndrica. Foi feita uma aplicação da metodologia de otimização na descrição da cinética de secagem de bananas inteiras, usando dados experimentais disponíveis na literatura. Os indicadores estatísticos relativos aos ajustes possibilitam afirmar que a solução da equação de difusão com condição de contorno convectiva produz resultados significativamente melhores que aqueles considerando a condição de contorno de equilíbrio.
Scientific Electronic Library Online (English)
Cleide M. D. P. da S. e, Silva; Wilton P. da, Silva; Vera S. de O., Farias; Josivanda P., Gomes.
2012-04-01
Full Text Available Neste artigo, é usada uma metodologia para a determinação simultânea da difusividade efetiva e do coeficiente de transferência convectivo de massa em sólidos porosos que possam ser considerados como um cilindro infinito, durante sua secagem. Dois modelos são utilizados para a otimização e a simulaçã [...] o do processo de secagem: o modelo 1 (volume e difusividade constantes, com condição de contorno de equilíbrio); e o modelo 2 (volume e difusividade constantes, com condição de contorno convectiva). Algoritmos de otimização por varredura, baseados no método inverso, foram acoplados às soluções analíticas referentes aos dois modelos utilizados, possibilitando ajustar tais soluções aos dados experimentais da cinética de secagem em camada fina de produtos com a forma cilíndrica. Foi feita uma aplicação da metodologia de otimização na descrição da cinética de secagem de bananas inteiras, usando dados experimentais disponíveis na literatura. Os indicadores estatísticos relativos aos ajustes possibilitam afirmar que a solução da equação de difusão com condição de contorno convectiva produz resultados significativamente melhores que aqueles considerando a condição de contorno de equilíbrio. Abstract in english In this article, a methodology is used for the simultaneous determination of the effective diffusivity and the convective mass transfer coefficient in porous solids, which can be considered as an infinite cylinder during drying. Two models are used for optimization and drying simulation: model 1 (co [...] nstant volume and diffusivity, with equilibrium boundary condition), and model 2 (constant volume and diffusivity with convective boundary condition). Optimization algorithms based on the inverse method were coupled to the analytical solutions, and these solutions can be adjusted to experimental data of the drying kinetics. An application of optimization methodology was made to describe the drying kinetics of whole bananas, using experimental data available in the literature. The statistical indicators enable to affirm that the solution of diffusion equation with convective boundary condition generates results superior than those with the equilibrium boundary condition.
International Nuclear Information System (INIS)
When simulating the High Pressure Die Casting 'HPDC' process, the heat transfer coefficient 'HTC' between the casting and the die is critical to accurately predict the quality of the casting. To determine the HTC at the metal-die interface a production die for an automotive engine bearing beam, Die 1, was instrumented with type K thermocouples. A Magmasoft simulation model was generated with virtual thermocouple points placed in the same location as the production die. The temperature traces from the simulation model were compared to the instrumentation results. Using the default simulation HTC for the metal-die interface, a poor correlation was seen, with the temperature response being much less for the simulation model. Because of this, the HTC at the metal-die interface was modified in order to get a better fit. After many simulation iterations, a good fit was established using a peak HTC of 42,000 W/m2 K, this modified HTC was further validated by a second instrumented production die, proving that the modified HTC gives good correlation to the instrumentation trials. The updated HTC properties for the simulation model will improve the predictive capabilities of the casting simulation software and better predict casting defects. - Highlights: ? The HTC between the casting and die is critical to predict casting quality. ? A Magmasoft simulation model was used to simulate the casting die. ? A good fit to the simulation model was established using a peak HTC of 42 kW/m2 K. ? The improved simulation model will improve the accuracy to predict casting defects.
Heat pipe and surface mass transfer cooling of hypersonic vehicle structures
Colwell, Gene T.; Modlin, James M.
1992-01-01
The problem of determining the feasibility of cooling hypersonic vehicle leading-edge structures exposed to severe aerodynamic surface heating using heat pipe and mass transfer cooling techniques is addressed. A description is presented of a numerical finite-difference-based hypersonic leading-edge cooling model incorporating poststartup liquid metal heat pipe cooling with surface transpiration and film cooling to predict the transient structural temperature distributions and maximum surface temperatures of hypersonic vehicle leading edge. An application of this model to the transient cooling of a typical aerospace plane wing leading-edge section. The results of this application indicated that liquid metal heat pipe cooling alone is insufficient to maintain surface temperatures below an assumed maximum level of 1800 K for about one-third of a typical aerospace plane ascent trajectory through the earth's atmosphere.
Stalmach, C. J., Jr.
1975-01-01
Several model/instrument concepts employing electroless metallic skin were considered for improvement of surface condition, accuracy, and cost of contoured-geometry convective heat transfer models. A plated semi-infinite slab approach was chosen for development and evaluation in a hypersonic wind tunnel. The plated slab model consists of an epoxy casting containing fine constantan wires accurately placed at specified surface locations. An electroless alloy was deposited on the plastic surface that provides a hard, uniformly thick, seamless skin. The chosen alloy forms a high-output thermocouple junction with each exposed constantan wire, providing means of determining heat transfer during tunnel testing of the model. A selective electroless plating procedure was used to deposit scaled heatshield tiles on the lower surface of a 0.0175-scale shuttle orbiter model. Twenty-five percent of the tiles were randomly selected and plated to a height of 0.001-inch. The purpose was to assess the heating effects of surface roughness simulating misalignment of tiles that may occur during manufacture of the spacecraft.
Directory of Open Access Journals (Sweden)
Jing Cui
2015-06-01
Full Text Available The surface characteristics, such as wettability and roughness, play an important role in heat transfer performance in the field of microfluidic flow. In this paper, the process of a hot liquid flowing through a microchannel with cold walls, which possesses different surface wettabilities and microstructures, is simulated by a transient double-distribution function (DDF two-phase thermal lattice Boltzmann BGK (LBGK model. The Shan-Chen multiphase LBGK model is used to describe the flow field and the independent distribution function is introduced to solve the temperature field. The simulation results show that the roughness of the channel wall improves the heat transfer, no matter what the surface wettability is. These simulations reveal that the heat exchange characteristics are directly related to the flow behavior. For the smooth-superhydrophobic-surface flow, a gas film forms that acts as an insulating layer since the thermal conductivity of the gas is relatively small in comparison to that of a liquid. In case of the rough-superhydrophobic-surface flow, the vortex motion of the gas within the grooves significantly enhances the heat exchange between the fluid and wall.
Surface temperature/heat transfer measurement using a quantitative phosphor thermography system
Buck, G. M.
1991-01-01
A relative-intensity phosphor thermography technique developed for surface heating studies in hypersonic wind tunnels is described. A direct relationship between relative emission intensity and phosphor temperature is used for quantitative surface temperature measurements in time. The technique provides global surface temperature-time histories using a 3-CCD (Charge Coupled Device) video camera and digital recording system. A current history of technique development at Langley is discussed. Latest developments include a phosphor mixture for a greater range of temperature sensitivity and use of castable ceramics for inexpensive test models. A method of calculating surface heat-transfer from thermal image data in blowdown wind tunnels is included in an appendix, with an analysis of material thermal heat-transfer properties. Results from tests in the Langley 31-Inch Mach 10 Tunnel are presented for a ceramic orbiter configuration and a four-inch diameter hemisphere model. Data include windward heating for bow-shock/wing-shock interactions on the orbiter wing surface, and a comparison with prediction for hemisphere heating distribution.
Heat transfer and friction correlations and thermal performance analysis for a finned surface
Energy Technology Data Exchange (ETDEWEB)
Bilen, K. [University of Ataturk, Erzurum (Turkey). Dept. of Mechanical Engineering; Akyol, U. [University of Trakya (Turkey). Dept. of Mechanical Engineering; Yapici, S. [University of Ataturk, Erzurum (Turkey). Dept. of Chemical Engineering
2001-07-01
In the present work, the heat transfer and friction loss characteristics were investigated experimentally, employing a finned heating surface kept at a constant temperature of 45{sup o}C in a rectangular channel through which air was passed as a working fluid. The position of the cylindrical fins attached on the surface was arranged either in-line or staggered. The parameters for the study were chosen as Reynolds number (3700-30000), depending on hydraulic diameter, the distance between fins in the flow direction (S{sub y}/D = 1.96-4.41) and fin arrangement. The variation of Nusselt number with these parameters was determined and presented graphically. For both fin arrangements, it was found that increasing Reynolds number increased Nusselt number and friction factor were developed for both fin arrangements and smooth channel, and the thermal performances of the arrangements were also determined and compared with respect to heat transfer from the same surface without fins. With the staggered array, a heat transfer enhancement up to 33% at constant pumping power was achieved. (Author)
International Nuclear Information System (INIS)
The evolution of molecular excited states near solid surfaces is investigated. The mechanisms through which energy is transferred to the surface are described within a classical image dipole picture of the interaction. More sophisticated models for the dielectric response of the solid surface add important new decay channels for the energy dissipation. The predictions and applicability of three of these refined theories are discussed
Energy Technology Data Exchange (ETDEWEB)
Teixeira, G.J.; Sousa, C.H.S.; Peixoto, J.G.P., E-mail: gt@ird.gov.br [Instituto de Radioprotecao e Dosimetria, (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)
2014-07-01
The objective was to determine, through specific software, the mass-energy transfer coefficients by X-ray beams in air between 30-150 kV. Were generated by the Spectrum Processor program, the spectra and calculated their mass coefficients. The results behaved numerically decreasing order, ranging between 0.3733 and 0.0439 cm{sup 2}/g, inversely proportional to the voltage used and differing behavior of mono-energetic beams above 100 keV. Values align with literal definitions of the interaction of radiation with matter, being useful for dosimetry in diagnostic radiology, including for systems not using an ionization chamber. (author)
Carlsson, Per
2007-01-01
When designing a new fuel management system for a spark ignition engine the amount of air that is fed to the cylinders is highly important. A tool that is being used to improve the performance and reduce emission levels is engine modeling were a fuel management system can be tested and designed in a computer environment thus saving valuable setup time in an engine test cell. One important part of the modeling is the throttle which regulates the air. The current isentropic model has been inves...