Modeling Local Hygrothermal Interaction: Local surface transfer coefficients
DEFF Research Database (Denmark)
Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans; Rode, Carsten
2009-01-01
Current models to predict heat, air and moisture (HAM) conditions in building components assume uniform boundary conditions, both for the temperature and relative humidity of the air in an indoor space as well as for the heat and moisture surface transfer coefficients. In order to obtain a reliable prediction of the HAM conditions in a building component, an accurate description of the indoor boundary conditions is required. This paper presents the modelling of the local indoor environmental con...
The heat transfer coefficient on film cooled surfaces
Ammari, H.D.
1989-01-01
A systematic investigation of the effects of coolant-to-mainstream density ratio and mainstream acceleration on the heat transfer following injection through a row of holes in a flat plate into a turbulent boundary layer is described. A mass transfer technique was employed which uses a swollen polymer surface and laser holographic interferometry. The constant concentration of the test surface simulated isothermal conditions. Density ratios in excess of unity, representative of gas turbine ope...
DEFF Research Database (Denmark)
Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans; Rode, Carsten
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 showe...
Sivaraja Subramania Pillai; Ryuichiro Yoshie
2013-01-01
This study investigates the effect of flow velocity and building surface temperature effects on Convective Heat Transfer Coefficient (CHTC) from urban building surfaces by numerical simulation. The thermal effects produced by geometrical and physical properties of urban areas generate a relatively differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI) phenomena. The urban thermal comfort is directly related to the CHTC from the urban can...
Directory of Open Access Journals (Sweden)
Sivaraja Subramania Pillai
2013-06-01
Full Text Available This study investigates the effect of flow velocity and building surface temperature effects on Convective Heat Transfer Coefficient (CHTC from urban building surfaces by numerical simulation. The thermal effects produced by geometrical and physical properties of urban areas generate a relatively differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI phenomena. The urban thermal comfort is directly related to the CHTC from the urban canopy surfaces. This CHTC from urban canopy surfaces expected to depend upon the wind velocity flowing over the urban canopy surfaces, urban canopy configurations, building surface temperature etc. But the most influential parameter on CHTC has not been clarified yet. Urban canopy type experiments in thermally stratified wind tunnel have normally been used to study the heat transfer issues. But, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary on individual canyon surfaces such as building roof, walls and ground. Numerical simulation validated by wind tunnel experiments can be an alternative for the prediction of CHTC from building surfaces in an urban area. In our study, wind tunnel experiments were conducted to validate the low-Reynolds-number k-? model which was used for the evaluation of CHTC from surfaces. The calculated CFD results showed good agreement with experimental results. After this validation, the effects of flow velocity and building surface temperature effects on CHTC from urban building surfaces were investigated. It has been found that the change in velocity remarkably affects the CHTC from urban canopy surfaces and change in surface temperature has almost no effect over the CHTC from urban canopy surfaces.
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.
Neely, AJ; Ireland, PT; Harper, LR
1997-01-01
An experimental investigation of the performance of extended fin surfaces for the forced convective cooling of a range of engine component geometries in crossflow is reported. The experiments were undertaken to measure the surface heat transfer coefficient distributions of external finning around non-cylindrical geometries for use in aviation gas turbines in which the cooling performance/mass ratio must be maximized. The geometries examined were a box (square with rounded corners), a flute (r...
Energy Technology Data Exchange (ETDEWEB)
Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering
2013-07-01
Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)
Measuring of heat transfer coefficient
DEFF Research Database (Denmark)
Henningsen, Poul; Lindegren, Maria
2000-01-01
Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine ...
International Nuclear Information System (INIS)
Because convective heat transfer is enhanced in flow past rough surfaces, much experimental and analytical effort over the past several decades has been devoted to the evaluation of artificial roughening for potential application to the heat transfer surfaces of gas-cooled reactors. Unfortunately, much of the analytical development in this field has been inadequately explained in the literature; this has led to misinterpretation of some of the subsequent experimental findings, compounding the uncertainty. This work provides a critical review of the underlying assumptions, theoretical foundations, and supporting experimental evidence for the analytical procedures in current use for the evaluation of roughness effects. It is a concise presentation of the available formulations with recommendations concerning their applicability to rough rod bundles
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
Gillespie, DRH; Guo, SM; Wang, Z.; Ireland, PT; Kohler, ST
1996-01-01
Full heat transfer coefficient and static pressure distributions have been measured on the target surface under impinging jets formed by sharp-edged and large entry radius holes. These geometries are representative of impingement holes in a gas turbine blade manufactured by laser cutting and by casting, respectively. Target surface heat transfer has been measured in a large scale perspex rig using both the transient liquid crystal technique and hot thin film gauges. A range of jet Reynolds nu...
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
Energy Technology Data Exchange (ETDEWEB)
Hodge, S.A.; Sanders, J.P.; Klein, D.E.
1979-11-01
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.
Sensitivity of the Heat Transfer Coefficient Calculation
Singer, Sasa
2014-01-01
The purpose of the Liscic/Petrofer probe is to determine the cooling intensity during liquid quenching in laboratory and workshop environments. The surface heat transfer coefficient is calculated by the one-dimensional finite volume method from the smoothed temperature curve, measured at a near-surface point in the probe. Smoothed reference temperature curves for oil and water, based on measurements made by the probe, are used in a series of numerical experiments to investig...
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...
Non intrusive measurement of the convective heat transfer coefficient
Energy Technology Data Exchange (ETDEWEB)
Rebay, M.; Mebarki, G.; Padet, J. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Arfaoui, A. [Reims Univ., Reims (France). Faculty of Science, GRESPI Thermomechanical Lab; Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM; Maad, B.R. [Tunis Univ., Tunis (Tunisia). Faculty of Science, EL MANAR, LETTM
2010-07-01
The efficiency of cooling methods in thermal systems such as radiators and heat exchangers must be improved in order to enhance performance. The evaluation of the heat transfer coefficients between a solid and a fluid is necessary for the control and the dimensioning of thermal systems. In this study, the pulsed photothermal method was used to measure the convective heat transfer coefficient on a solid-fluid interface, notably between an air flow and a heated slab mounted on a PVC flat plate. This configuration simulated the electronic air-cooling inside enclosures and racks. The influence of the deflector's inclination angle on the enhancement of heat transfer was investigated using 2 newly developed identification models. The first model was based on a constant heat transfer coefficient during the pulsed experiment, while the second, improved model was based on a variable heat transfer coefficient. The heat transfer coefficient was deduced from the evolution of the transient temperature induced by a sudden deposit of a luminous energy on the front face of the slab. Temperature evolutions were derived by infrared thermography, a camera for cartography and a detector for precise measurement in specific locations. The results show the improvement of measurement accuracies when using a model that considers the temporal evolution of the convective heat transfer coefficient. The deflection of air flow on the upper surface of the heated slab demonstrated better cooling of the slab by the deflection of air flow. 11 refs., 1 tab., 8 figs.
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.)
Determination of the surface drag coefficient
DEFF Research Database (Denmark)
Mahrt, L.; Vickers, D.; Sun, J.L.; Jensen, N.O.; Ejsing Jørgensen, Hans; Pardyjak, E.; Fernando, H.
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 w...
Experimental evaluation of heat transfer coefficients between radiant ceiling and room
DEFF Research Database (Denmark)
Causone, Francesco; Corgnati, Stefano P.; Filippi, Marco; Olesen, Bjarne W.
2009-01-01
The heat transfer coefficients between radiant surfaces and room are influenced by several parameters: surfaces temperature distributions, internal gains, air movements. The aim of this paper is to evaluate the heat transfer coefficients between radiant ceiling and room in typical conditions of occupancy of an office or residential building. Internal gains were therefore simulated using heated cylinders and heat losses using cooled surfaces. Evaluations were developed by means of experimental te...
Indian Academy of Sciences (India)
E C Monahan
2002-09-01
Stage A whitecaps (spilling wave crests) have a microwave emissivity of close to 1. Thus if even a small fraction of the sea surface is covered by these features there will be a detectable enhancement in the apparent microwave brightness temperature of that surface as determined by satellite-borne microwave radiometers. This increase in the apparent microwave brightness temperature can as a consequence be routinely used to estimate the fraction of the sea surface covered by stage A whitecaps. For all but the very lowest wind speeds it has been shown in a series of controlled experiments that the air-sea gas transfer coeffcient for each of a wide range of gases, including carbon dioxide and oxygen, is directly proportional to the fraction of the sea surface covered by these stage A whitecaps.
Overall mass-transfer coefficients in non-linear chromatography
DEFF Research Database (Denmark)
Mollerup, JØrgen; Hansen, Ernst
1998-01-01
In case of mass transfer where concentration differences in both phases must be taken into account, one may define an over-all mass-transfer coefficient basd on the apparent over-all concentration difference. If the equilibrium relationship is linear, i.e. in cases where a Henry´s law relationship can be applied, the over-all mass-transfer coefficient will be concentration independent. However, in mass-transfer operations, a linear equilibrium relationship is in most cases not a valid approximation wherefore the over-all mass-transfer coefficient becomes strongly concentration dependent as shown in this paper. In this case one has to discard the use of over-all mass-transfer coefficients and calculate the rate of mass transfer from the two film theory using the appropriate non-linear relationship to calculate the equilibrium ratio at the interface between the two films.
Spatial dependence of local heat transfer coefficients in liquid metal sub-channel flows
International Nuclear Information System (INIS)
CFD code, FLUENT was applied to investigate the spatial dependence of local rod surface heat transfer coefficients of liquid sodium and liquid lead flows in a triangular sub-channel. As a result of high thermal conductivities in liquid metals, their thermal boundary layers are thicker than ordinary fluids. Their developments are then dependent on the available void spaces inside the sub-channel. This means that local surface convective heat transfer coefficients are not uniform around the fuel rod, resulting non-uniform surface temperature distributions in the azimuthal direction. Our studies show that higher local heat transfer coefficients are observed at surfaces whose facing channel widths are narrower. The ratios of maximum-to-minimum heat transfer coefficients are 2.66, 1.92, 1.57 for pitch-to-diameter ratios of 1.1, 1.2, 1.375 respectively. Such spatial dependence is quite apparent for low P/D's. (authors)
Condensation heat transfer coefficients in LWR-containments during LOCA
International Nuclear Information System (INIS)
Best estimate calculations in nuclear safety analysis require replacement of conservative assumptions by measured data or verified correlations. In the field of containment response analysis this holds for condensation heat transfer coefficients at containment structures. In a large scale pressure suppression test facility heat transfer coefficients are determined at structures of the drywell in order to get data representative for break compartments of LWR-containments. Experimental results show heat transfer coefficients of the order 104 W.m-2.K-1 even at presence of noncondensable gas
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.
Dateo, Christopher E.; Arnold, James O. (Technical Monitor)
1994-01-01
A new analytic global potential energy surface describing the hydroperoxyl radical system H((sup 2)S) + O2(X (sup 3)Sigma((sup -)(sub g))) (reversible reaction) HO2 ((X-tilde) (sup 2)A'') (reversible reaction) O((sup 3)P) + O H (X (sup 2)Pi) has been fitted using the ab initio complete active space SCF (self-consistent-field)/externally contracted configuration interaction (CASSCF/CCI) energy calculations of Walch and Duchovic. Results of quasiclassical trajectory studies to determine the rate coefficients of the forward and reverse reactions at combustion temperatures will be presented. In addition, vibrational energy levels were calculated using the quantum DVR-DGB (discrete variable representation-distributed Gaussian basis) method and the splitting due to H atom migration is investigated. The material of the proposed presentation was reviewed and the technical content will not reveal any information not already in the public domain and will not give any foreign industry or government a competitive advantage.
Heat transfer coefficient for F.E analysis in the warm forging process
Kang, S S; KANG, J. H.; Lee, K. O.
2007-01-01
Purpose: The Purpose of this paper is to obtain suitable convection and contact heat transfer coefficient forone-time finite element analysis in the warm forging process.Design/methodology/approach: To do this, the temperature of the tool used in the operation was measured witha thermocouple and repeated finite element analysis(FEA) was performed using the experimentally calculatedcontact and cooling heat transfer coefficient. Also the surface temperature of the active tool was obtained bycom...
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
International Nuclear Information System (INIS)
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
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.
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.)
DEFF Research Database (Denmark)
Ratkovich, Nicolas Rios; Berube, P.R.; Nopens, I.
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 comp...
Finite element model for beef chilling using CFD-generated heat transfer coefficients
Energy Technology Data Exchange (ETDEWEB)
Pham, Q.T. [University of New South Wales, Sydney, NSW 2052 (Australia); Trujillo, F.J. [Food Science Australia, 11 Julius Avenue, North Ryde, NSW 2113 (Australia); McPhail, N. [Food Science Australia, P.O. Box 3312, Tingalpa DC, Brisbane, QLD 4173 (Australia)
2009-01-15
A combined model of the beef chilling process is presented, in which computational fluid dynamics (CFD) was used to estimate the local heat and mass transfer coefficients, assuming uniform surface temperatures, and a set of 2-D finite element grids was used to solve the heat transfer equation in the product, which has an elongated shape. Another set of 1-D grids was used to solve the water transport equation near the surface of the meat. The surface transfer coefficients were calculated for various combinations of air orientations and speeds, and summarised in a set of regression equations. The model was verified by existing and new data on heat load, temperatures, weight loss and surface water activity. (author)
Measurement of Heat Transfer Coefficient by Thermochromic Liquid Crystals.
Czech Academy of Sciences Publication Activity Database
Vejražka, Ji?í; Marty, Ph.
Bratislava : Slovak University of Technology, 2002 - (Markoš, J.; Štefuca, V.), s. 17 ISBN 80-227-1690-1. [International Conference of Slovak Society of Chemical Engineering /29./. Tatranské Matliare (SK), 27.05.2002-31.05.2002] Institutional research plan: CEZ:AV0Z4072921 Keywords : measurement * transfer coefficient * liquid crystals Subject RIV: CI - Industrial Chemistry, Chemical Engineering
Estimation of bulk transfer coefficient for latent heat flux (Ce)
Digital Repository Service at National Institute of Oceanography (India)
Sadhuram, Y.
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...
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.
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-01
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985
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.
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.)
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
Measurement and modeling of interface heat transfer coefficients
International Nuclear Information System (INIS)
The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m2/K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, epsilon = 0.2, of the solidified metal
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 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
International Nuclear Information System (INIS)
The difficulty in solving heat transfer tasks in machine structures is often involved in determination of heat transfer coefficient on the surface of the given part. The method considered enables this calculation when based only on values of temperature, measured at several arbitrary points within the part. The points may be placed even outside the exposed region. Let us consider a body of general shape with heat transfer on its surface S. Boundary conditions on the part S(4) of the surface S may be known, and on the other part S(B) of the surface S are given either in terms of surrounding temperature, which is supposed to be known, and of heat transfer coefficient. The spatially variable distribution of the latter can be expressed by Langrange's polynomial, determined by unknown values of the heat transfer coefficient in several points on the surface S(B). These values form the vector V, that describes the heat transfer coefficient distribution with accuracy, proportional to the chosen dimension of the vector. In this way the vector defines also a temperature field of the given body. the task is now to find a vector determining such temperature field, that proves the best agreement with experimental results. This is performed by Nelder and Meads direct search optimizing method. The method requires the evaluation of temperature fields, corresponding to the initial set of vectors V. The temperature field is computed by the finite element method using triangular elements with linear approximation of temperatures. In accordance with the foregoing outlines a FORTRAN program for the ICL 1905 computer was written
Modeling the Effect of Internal Convection Currents on Heat Transfer Coefficient of Liquid Foods
SAJID ALI; RASHID ALI
2013-01-01
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-...
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.
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...
Transfer coefficients of radionuclides secreted in milk of dairy cows
International Nuclear Information System (INIS)
This study simulated experimentally the transfer of radionuclides to milk of dairy cows on a worst-case situation using various radionuclides known to emanate from nuclear power stations and which have been detected on particulates. Two lactating Holstein cows were administered orally one gelatin capsule containing 10 radionuclides in water-soluble form per day for 14 consecutive days. Milk samples were collected and aliquots analyzed in a germanium lithium-drifted detector coupled to a 2048-multichannel gamma-ray analyzer to measure small amounts of complex mixtures of radionuclides. The transfer coefficients of the radionuclides were calculated when their secretion in milk reached or approached a plateau of concentration. The radionuclides and their transfer coefficients to milk were: chromium51 less than 0.01%; manganese54 0.033 +- 0.005%; cobalt60 0.01 +- 0.002%; iron59 0.0048 +- 0.002%; zinc65 0.31 +- 0.07%; selenium75 0.29 +- 0.1%; antimony125 0.011 +- 0.003%; iodine131 0.88 +- 0.05%; and cesium137 0.79 +- 0.08%
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.
Hernandez-Morales, B.; Brimacombe, J. K.; Hawbolt, E. B.
1992-12-01
An existing sequential function specification algorithm for the solution of the inverse heat conduction problem (IHCP) has been applied to determine the response of both the surface heat flux and the surface temperature of flat stainless steel samples subjected to water quenching under controlled laboratory conditions that ensured one-dimensional heat flow. From this information, combined convective and radiative heat-transfer coefficients have been obtained as a function of steel surface temperature. The computer code was subsequently modified to solve the IHCP for air-cooled cylindrical carbon steel samples. In the algorithm, the problem is linearized by assuming the thermophysical properties of the steel to be fixed at values from the previous time step while estimating the current surface heat flux, which results in a more efficient code without a severe loss of accuracy. When compared with iterative (“brute force”) methods commonly used in the past, techniques like sequential function specification offer a more robust strategy for solving the IHCP. By including information on future measurements, while solving for the unknown surface heat flux at a particular time, the sequential function specification algorithm effectively prevents over-responses to measured temperatures, and large variations in calculated heat-transfer coefficients, observed when sequential matching is applied, can be reduced. Sensitivity coefficients, a measure of the response of temperature to changes in the unknown surface heat flux which are calculated with this algorithm, can be used to design experiments involving the IHCP effectively.
Confirmation of selected milk and meat radionuclide transfer coefficients. Progress report
International Nuclear Information System (INIS)
The objectives are to determine transfer coefficients to milk, beef and chicken of four radionuclides for which transfer coefficients were either indetermined or based upon secondary data. The radionuclides are 99Mo, 99Tc, 140Ba, and 131Te. The transfer coefficient for 133I to eggs was also determined, because again only limited data was available in the literature
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 ...
Heat transfer coefficient determination for flow boiling in vertical and horizontal minichannels
Directory of Open Access Journals (Sweden)
Piasecka Magdalena
2014-03-01
Full Text Available The paper presents the results of boiling heat transfer research during FC-72 laminar flow along a minichannel of 1 mm depth, positioned vertically and horizontally, with an enhanced heating surface. One glass pane allows to determine the temperature of the heating wall by liquid crystal thermography. Calculations are aimed at the evaluation of one- and two-dimensional heat transfer approaches to determine the local heat transfer coefficient. In the one-dimensional approach only the direction of the flow in the channel is considered. In the two-dimensional approach the inverse problem in the heating wall and the direct problem in the glass barrier were solved by the finite element method with Trefftz functions as shape functions (FEMT. The developed flow boiling area was studied. Heat transfer coefficient values obtained for the horizontal minichannel were higher than those obtained for the vertical one. When the heat flux supplied to heating wall grows, the share of gas-phase increases leading to the heat transfer coefficient decreases. The same courses of the experiment were observed for the two applied methods, but the results obtained in the one-dimensional approach are considerably higher than in the two-dimensional one. One-dimensional approach seems to be less sensitive to measurement errors.
Heat transfer from rough surfaces
International Nuclear Information System (INIS)
Artificial roughness is often used in nuclear reactors to improve the thermal performance of the fuel elements. Although these are made up of clusters of rods, the experiments to measure the heat transfer and friction coefficients of roughness are performed with single rods contained in smooth tubes. This work illustrated a new transformation method to obtain data applicable to reactor fuel elements from these annulus experiments. New experimental friction data are presented for ten rods, each with a different artificial roughness made up of two-dimensional rectangular ribs. For each rod four tests have been performed, each in a different outer smooth tube. For two of these rods, each for two different outer tubes, heat transfer data are also given. The friction and heat transfer data, transformed with the present method, are correlated by simple equations. In the paper, these equations are applied to a case typical for a Gas Cooled Fast Reactor fuel element. (orig.)
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.
Mass-transfer coefficients at the uranium adsorption from solution on ion exchange resins
International Nuclear Information System (INIS)
The process of uranium adsorption on ion exchange resins is a mass-transfer process of solid-liquid nature asociated with chemical reaction. Mathematical models used in these studies considers a spherical ion exchange resin grain where on its surface and its pores is taking place the chemical reaction. This paper presents experimental data of the uranium adsorption from alkaline solutions on a strong basic ion exchange resin, second type in chlorine form. The resin and the solution are contacting in two ways: fixed bed and perfect mixing. The optimal resin size and mass transfer coefficient was established for uranium adsorption from alkaline solutions. Also, criterial relation were established between mass-transfer process variables, impulse transfer, equipment geometry used for the experiments. (orig.)
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
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.
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.
Dimethylsulfide gas transfer coefficients from algal blooms in the Southern Ocean
Bell, T. G.; De Bruyn, W.; Marandino, C. A.; Miller, S. D.; Law, C. S.; Smith, M. J.; Saltzman, E. S.
2015-02-01
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 show 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.
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
Mass transfer coefficients in a hanson mixer-settler extraction column
Directory of Open Access Journals (Sweden)
M. Torab-Mostaedi
2008-09-01
Full Text Available The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with further increase in agitation speed. It was found that the volumetric overall mass transfer coefficient increases with increase in dispersed phase flow rate, while it decreases with increase in continuous phase flow rate. By using interfacial area, the overall mass transfer coefficients for continuous and dispersed phases are determined from volumetric coefficients. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is proposed in terms of Sherwood and Reynolds numbers. Also the experimental data of the column investigated are compared with data for various extraction columns. Comparison between theoretical models and experimental results for the dispersed phase mass transfer coefficient shows that these models do not have enough accuracy for column design. Using effective diffusivity in the Gröber equation results in more accurate prediction of overall mass transfer coefficient. The prediction of overall mass transfer coefficients from the presented equations is in good agreement with experimental results.
Mass transfer coefficients in a hanson mixer-settler extraction column
Scientific Electronic Library Online (English)
M., Torab-Mostaedi; S. J., Safdari; M. A., Moosavian; M. Ghannadi, Maragheh.
2008-09-01
Full Text Available The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficie [...] nts have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with further increase in agitation speed. It was found that the volumetric overall mass transfer coefficient increases with increase in dispersed phase flow rate, while it decreases with increase in continuous phase flow rate. By using interfacial area, the overall mass transfer coefficients for continuous and dispersed phases are determined from volumetric coefficients. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is proposed in terms of Sherwood and Reynolds numbers. Also the experimental data of the column investigated are compared with data for various extraction columns. Comparison between theoretical models and experimental results for the dispersed phase mass transfer coefficient shows that these models do not have enough accuracy for column design. Using effective diffusivity in the Gröber equation results in more accurate prediction of overall mass transfer coefficient. The prediction of overall mass transfer coefficients from the presented equations is in good agreement with experimental results.
International Nuclear Information System (INIS)
A computer tomography based methodology is applied to determine the transport properties of fluid flow across porous media. A 3D digital representation of a 10-ppi reticulate porous ceramic (RPC) sample was generated by X-ray tomographic scans. Structural properties such as the porosity, specific interfacial surface area, pore-size distribution, mean survival time, two-point correlation function s2, and local geometry distribution of the RPC sample are directly extracted from the tomographic data. Reference solutions of the fluid flow governing equations are obtained for Re = 0.2-200 by applying finite volume direct pore-level numerical simulation (DPLS) using unstructured, body-fitted, tetrahedral mesh discretization. The permeability and the Dupuit-Forchheimer coefficient are determined from the reference solutions by DPLS, and compared to the values predicted by selected porous media flow models, namely: conduit-flow, hydraulic radius theory, drag models, mean survival time bound, s2-bound, fibrous bed correlations, and local porosity theory-based models. DPLS is further employed to determine the interfacial heat transfer coefficient and to derive a corresponding Nu-correlation, which is compared to empirical correlations
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.
Effect of design and operation parameters on heat transfer coefficient in condensers
International Nuclear Information System (INIS)
Accurate and optimum usage of energy sources is gaining importance all over the world due to the increase of energy need and limited energy sources. Increasing condenser efficiency, reduce both the dimensions and the material usage and also the investment cost of the devices. This can be maintained by increasing the heat transfer coefficient in condensers. Generally, tubes having plain inner surfaces are mounted horizontally in serpentine type condenser applications and due to the performance loss results from the congestion in serpentine connections, vertical tube mounting is not preferred. Due to the complexity of the two-phase flow, a single set of correlation for heat transfer cannot be used. Average and local heat transfer coefficient for condensers are determined. Moreover, for each experiments flow pattern is determined and the validity of the correlations are compared according to that flow pattern. In Table 2, some of the experiments for R134a are listed. Local heat transfer coefficient is also important for condenser design. As a result, to design effective condensers the accuracy of the correlations is very important. When all the experiments are taken into account, it is seen that deviation of the correlations differs according to the refrigerant type, tube dimensions, mass flux, saturation temperature and flow pattern. For high mass flux (>400 kg/m2s) Traviss (1973) correlation failed. For small diameters (<3.14 mm) Tandon (1985) correlation estimate the heat transfer coefficient with a high deviation. Most accurate results are obtained for Akers et al. (1959), M.M. Shah (1978), Cavallini and Zecchlin (1974), J.R. Thome - J. El Hajal - A. Cavallini (2003) correlations. For high mass flux and annular flow, M.M. Shah (1978) correlation estimates the heat transfer coefficient with high precision. However, as the tube diameter decrease, this deviation increases. For small tube diameter such as 0.691 mm Cavallini and Zecchlin (1974) gives the most accurate results. J.R. Thome - J. El Hajal - A. Cavallini (2003) correlations are classified according to the flow pattern. For stratified flow the accuracy of that correlation is much better than the others. (author)
International Nuclear Information System (INIS)
The tritium bred in a deuterium-tritium fusion reactor is removed from its blanket by using helium sweep gas. From the viewpoint of adsorption capacity and pressure of tritium at release, a cryosorption bed, which uses molecular sieves or activated carbon at the temperature of liquid nitrogen, is attractive for the recovery of this tritium. The mass transfer coefficients required to predict the breakthrough curve are experimentally discussed. The overall mass transfer coefficient KFav, in the cryosorption of hydrogen isotopes on molecular sieves or activated carbon at 77 K consists of a mass transfer coefficient that represents the transfer from the bulk gas flow to the surface of the adsorbent through the boundary layer kfav, a mass transfer coefficient that represents the axial dispersion in the packed bed kzav, and a mass transfer coefficient that represents the intraparticle diffusion through micro pores in the adsorbent particle ?ks av. The value of ?ksav is confirmed to be 1 to 50 s-1, which decreases with an increase of hydrogen partial pressure, and the rate-controlling step is ?ksav when the hydrogen partial pressure is higher than several hundred pascals, and kzav, becomes the rate-controlling step when the hydrogen partial pressure is low and gas velocity is slow. 7 refs., 10 figs., 4 tabs
Convective Heat Transfer Coefficients of the Human Body under Forced Convection from Ceiling
DEFF Research Database (Denmark)
Kurazumi, Yoshihito; Rezgals, Lauris; Melikov, Arsen Krikor
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 ...
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.
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
Energy Technology Data Exchange (ETDEWEB)
Danilov, Valery A. [Department of Chemical Engineering, Curtin University of Technology, GPO Box U1987, Perth WA 6001 (Australia); Department of Processes and Unit Operations of Chemical Technology, Kazan State Technological University, Kazan 420015 (Russian Federation); Tade, Moses O. [Department of Chemical Engineering, Curtin University of Technology, GPO Box U1987, Perth WA 6001 (Australia)
2009-08-15
A new technique is presented for estimating cathodic and anodic transfer coefficients from SOFC voltage-current curves. The new technique for charge transfer coefficients is based on integral characteristics of fuel cell polarization curves. Experimental data from literature are used to illustrate the parameter estimation from SOFC current-voltage curves. (author)
On calculation of heat transfer coefficient during boiling of liquid metals in a large volume
International Nuclear Information System (INIS)
A dependence is obtained for calculating the heat transfer coefficient in developed boiling of alkali metals in a large volume. It takes into account the influence of pressure, the acceleration of gravity, and the material of the heating agent on the magnitude of the heat transfer coefficient
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.
PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND WASTE
This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition ...
FEROZ, Shaik
2007-01-01
This paper presents the second part of experimental results for the mass transfer coefficients in the radial direction from the stagnation point of a multi-jet flow. Two more regions are identified on the target surface, beside the stagnation point/impingement region. One is the region in which the coefficients fall rapidly and the other is the region in which the fall in the coefficients is gradual and smooth as the impinging jet-flow is fully transformed into wall-jet flow. In vie...
Heat transfer from rough surfaces
International Nuclear Information System (INIS)
The transformation of the friction data obtained with experiments in annuli can be performed either with the assumption of universal logarithmic velocity profile or of an universal eddy momentum diffusivity profile. For the roughness of practical interest both methods, when properly applied, give good results. For these roughnesses the transformed friction factors seem not to be unduly affected if one assumes a constant slope of the velocity profile equal to 2.5. All the transformation methods of the heat transfer data so far proposed predict too high wall temperatures in the central channels of a 19-rod bundle with three-dimensional roughness. Preliminary calculations show that the application of the superimposition principle with the logarithmic temperature profiles gives good results for the three-dimensional roughness as well. Although the measurements show that the slope of the logarithmic temperature profiles is different from 2.5, the assumption of a constant slope equal to 2.5 does not affect the transformed heat transfer data appreciably. For moderately high roughness ribs the turbulent Prandtl number, averaged over the cross section of a tube, is about the same (approx. 0.8) for rough as for smooth surfaces. The temperature effect on the heat transfer data with air cooling is stronger than originally assumed in the general correlation of Dalle Donne and Meyer. With helium cooling this temperature effect is even stronger. (orig.)
International Nuclear Information System (INIS)
The tritium bred in a DT fusion reactor is taken out of its blanket using helium sweep gas. The cryosorption bed using molecular sieves or activated carbon at liquid nitrogen temperature is attractive for recovery of this tritium from the view point of adsorption capacity and pressure of tritium at release. The mass transfer coefficients required to predict the breakthrough curve are discussed in this paper. The surface diffusivity included in one of them is quantitated. Its value is dependent on the adsorption site. The rate controlling step changes with the equilibrium partial pressure of the hydrogen isotope, because the mass transfer coefficient representing the intraparticle diffusion decreases with increasing equilibrium pressure. The mass transfer coefficients in desorption are estimated to be the same as those in adsorption. 6 refs., 8 figs., 1 tab
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
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.
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)
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.
Mass transfer in the contamination of isothermal steel surfaces
International Nuclear Information System (INIS)
An existing mathematical model that describes the contamination of isothermal steel surfaces by radioactive corrosion products in high-temperature water is extended by including a term for mass transfer across the fluid boundary layer. Fits to experimental data from recirculating and once-through loops remain good, while predictions of corrosion rate are altered slightly. Resulting variations of initial deposition coefficient and surface activity with velocity are shown
Wall heat transfer coefficient for condensation and boiling in forced convection of sodium
International Nuclear Information System (INIS)
The wall heat transfer coefficient for sodium boiling and condensation in forced convective flow is theoretically derived by using the momentum-heat transfer analogy and the logarithmic law for velocity distribution in the liquid film. Only one constant in the logarithmic form is empirically determined. The results are insensitive to some of the approximations used, namely in the evaluation of E and of /tau/ /SUB i/ //tau/ /SUB w/. The results from the suggested correlation are in good agreement with the Zeigarnick and Litvinov data over the range of parameters that were specified in their experiments, while the Chen and NATOF correlations predict lower heat transfer coefficients. The suggested correlation predicts well the data in the high-heat transfer coefficient region. It can be argued that the data in the low heat transfer coefficient region are affected by unstable flow conditions and the uncertainties in the saturation-temperature measurements
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.
Fouling of heat transfer surfaces
International Nuclear Information System (INIS)
There are many parameters affecting the fouling deposit on the heat transfer surface. These parameters include flow velocity, surface temperature, fluid bulk temperature, fluid characteristics, surface material and structure. The flow velocity is one of the most important parameters affecting the fouling rate and there is a rarity in literature covering this effect. Therefore, the purpose of the present work is to study the effect of flow velocity on the fouling rate. To carry out this study, an experimental test rig has been designed and constructed. The experimental loop has three 97% Cu-Ni test tubes of 2400 mm length and 16 mm inner diameter. Water with a solid particle concentration of 19 m/lit is used as a test fluid. The test fluid flows through the tubes which are heated by means of steam. The cooling water is arranged in a closed loop to keep constant solid particle concentration. The experiments are carried out under constant surface temperature by using the steam as a heating medium. These experiments have been carried out under different flow velocities (from 0.2 to 1.42 m/s). The experimental loop is a differential one and the runs have been operated for long time (about 200 hrs.) to attain the asymptotic fouling resistance. The obtained experimental results are analyzed, and the effect of flow velocity on the fouling rate and the asymptotic fouling resistance is plotted. From the discussion of these results, it is concluded that; both the fouling resistance and the asymptotic fouling resistance decrease with increasing the flow velocity. The delay time is very small and is seen to approach zero in all the experimental work. The saw tooth effect has been obtained in all runs. Results have shown also essential.10 tabs.,4-8 figs.,71 refs
International Nuclear Information System (INIS)
The object of the experiments was to choose suitable particulate materials for a fluidised bed cooler, to test a deep fluidised bed for uniformity of heat transfer coefficient, and to explore the temperature distribution in a centrally heated annular fluidised bed. This memorandum records the techniques used and some of the practical aspects involved, together with the performance results obtained, for the assistance of other experimenters who may wish to use fluidised beds as a laboratory technique. Mathematical correlation of the results has not been attempted since some of the properties of the bed material were not known and to determine them was beyond the scope of the work programme. Rather, we have compared our results with those of other experimenters. Graphite tubes, for use in steady state thermal stress experiments, are to be heated by a graphite radiant heater situated in the bore and cooled on the outer surface. The tubes are 2 cm. bore, 8 cm. outside diameter and 48 cm. long. The outside temperature of the tubes is to be between 500 deg. C. and 1500 deg. C. It is estimated that the heat transfer rate required for fracture at the outer surface is 30 watts/cm2. This could readily be achieved by cooling with liquid metals, water or high velocity gas. However, serious problems of either materials compatibility or mechanical complexity make these undesirable. A water-cooled fluidised bed of compatible solids fluidised with nitrogen gas can overcome most of these problems and give heat transfer coefficients close to that required, vis. about 0.1 w/cm C . A coolant bed about 20'' long would be required and an annulus of about 2'' radial width round the specimen was considered to be practicable
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)
Measurement of Average Pool Boiling Heat Transfer Coefficient on Near-Horizontal Tube
International Nuclear Information System (INIS)
An experimental study is performed to obtain an average heat transfer coefficient around the perimeter of a near horizontal tube. For the test a stainless steel tube of 50.8 mm diameter submerged in water at atmospheric pressure is used. Both subcooled and saturated pool boiling conditions are considered and the inclination angle of the tube is changed from the horizontal position to 9 .deg. in steps of 3 .deg.. In saturated water, the local boiling heat transfer coefficient at the azimuthal angle of 90 .deg. from the tube bottom can be regarded as the average of the coefficients regardless of the tube inclination angles. However, when the water is subcooled the location for the average heat transfer coefficient depends on the inclination angle and the heat flux. It is explained that the major mechanisms changing the heat transfer are closely related with the intensity of the liquid agitation and the generation of big size bubbles through bubble coalescence
Estimating the workpiece-backingplate heat transfer coefficient in friction stirwelding
DEFF Research Database (Denmark)
Larsen, Anders; Stolpe, Mathias; Hattel, Jesper Henri
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 ...
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…
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)
Investigation of heat transfer coefficient during quenching in various cooling agents
International Nuclear Information System (INIS)
Highlights: • The highest HTC during quenching in mineral oils occur in temperature 520–550 °C. • The peaks of HTC for polymers exist at lower temperature compared to mineral oils. • Temperature and utilization time of coolant affect the heat transfer coefficient. • Ageing of mineral oils affects their severities; a direction of change is equivocal. -- Abstract: Heat transfer coefficients, HTCs, at the surface of a metal sample during immersion quenching were measured and evaluated using numerical procedures. The boundary inverse heat conduction problem has been defined and solved. A FEM self-developed computer code has been used to obtain a solution to the direct problem. The sensitivity of the method enabled us to examine the effect of various quenching parameters on the heat transfer for two mineral oils and a polymer quenchant. At 800 °C the HTC values were equal to ?0.5 kW/(m2 K) and ?3.2 kW/(m2 K), for mineral oils and a polymer coolant, respectively. They increased to ?4.7 kW/(m2 K) – oil A, ?6.0 kW/(m2 K) – oil B and ?7.4 kW/(m2 K) – polymer, respectively. The peak of HTC was sharp and occurred at a narrow temperature interval between 520 and 550 °C for the oils, whereas for the polymer, the peak was lower by approx. 100 K and flat over 100–120 K interval. Subsequently HTC decreased, and at ?150 °C the values were ?0.5 kW/(m2 K) and ?2.0 kW/(m2 K), for mineral oils and a water polymer coolant, respectively
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.
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.
DEFF Research Database (Denmark)
Feyissa, Aberham Hailu; Christensen, Martin Gram; Pedersen, Søren Juhl; Hickman, Minka; Adler-Nissen, Jens
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 ...
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.
Pool boiling heat transfer on surfaces with plain minifins and minifins with perforated foil
Directory of Open Access Journals (Sweden)
Nadstawna Ewelina
2014-01-01
Full Text Available The paper describes experimental study results for three kinds of enhanced surfaces (smooth surface, plain minifin surface and minifin surface with sintered perforated foil and for two kinds of boiling fluids (ethyl alcohol and NovecTM 649. Novec 649 is considered to be an environmentally friendly alternative for electronic devices cooling applications. The experiments were carried out at atmospheric pressure. Compared with smooth surface, the surface with plain minifins provides approximately 1.5-times higher heat transfer coefficient obtained with NovecTM 649 and ethyl alcohol boiling. At low and medium heat fluxes minifins with porous covering produced the highest heat transfer coefficient.
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
Ko?í, Václav; Ko?í, Jan; Korecký, Tomáš; Mad?ra, Ji?í; ?erný, Robert ?.
2015-04-01
The radiative heat transfer coefficient at high temperatures is determined using a combination of experimental measurement and computational modeling. In the experimental part, cement mortar specimen is heated in a laboratory furnace to 600°C and the temperature field inside is recorded using built-in K-type thermocouples connected to a data logger. The measured temperatures are then used as input parameters in the three dimensional computational modeling whose objective is to find the best correlation between the measured and calculated data via four free parameters, namely the thermal conductivity of the specimen, effective thermal conductivity of thermal insulation, and heat transfer coefficients at normal and high temperatures. The optimization procedure which is performed using the genetic algorithms provides the value of the high-temperature radiative heat transfer coefficient of 3.64 W/(m2K).
International Nuclear Information System (INIS)
In order to execute efficiently the free vibration analysis of 2-dimensional structures like plate structures, the author developed the finite element-transfer stiffness coefficient method. This method is based on the combination of the modeling techniques in the FEM and the transfer technique of the stiffness coefficient in the transfer stiffness coefficient method. Numerical results of the simply supported and the elastic supported rectangular plates showed that the present method can be successfully applied to the free vibration analysis of plate structures on a personal computer. We confirmed that, in the case of analyzing the free vibration of rectangular plate structures, the present method is superior to the FEM from the viewpoint of computation time and storage
Energy Technology Data Exchange (ETDEWEB)
Choi, Myung Soo [Pukyong National Univ., Busan (Korea, Republic of)
2003-06-01
In order to execute efficiently the free vibration analysis of 2-dimensional structures like plate structures, the author developed the finite element-transfer stiffness coefficient method. This method is based on the combination of the modeling techniques in the FEM and the transfer technique of the stiffness coefficient in the transfer stiffness coefficient method. Numerical results of the simply supported and the elastic supported rectangular plates showed that the present method can be successfully applied to the free vibration analysis of plate structures on a personal computer. We confirmed that, in the case of analyzing the free vibration of rectangular plate structures, the present method is superior to the FEM from the viewpoint of computation time and storage.
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
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The determination of the heat transfer coefficient of the pins of the Spallation Neutron Source is a very important problem for the development of this facility, as data for thermal and structural studies. For this purpose, a test apparatus was built, in scale 1:1, for the simulation of the thermal and hydraulical conditions of the Neutron Source. This apparatus is a pin bank, with one of the pins electrically heated. Performance of measurements gave the values for the heat transfer coefficient, here presented in the Nusselt Number form, and its local distribution. Results show the linear dependence of Nusselt Number on Reynolds Number, for a constant heat production. (orig.)
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
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)
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
A Study of the Heat Transfer Coefficient of a Mini Channel Evaporator with R-134a as Refrigerant
Dollera, E. B.; Villanueva, E. P.
2015-09-01
The present study is to evaluate the heat transfer coefficient of the minichannel copper blocks used as evaporator with R-134a as the refrigerant. Experiments were conducted using three evaporator specimens of different channel hydraulic diameters (1.0mm, 2.0mm, 3.0mm). The total length for each channel is 640 mm. The dimension of each is 100mm.x50mm.x20mm. and the outside surfaces were machined to have fins. They were connected to a standard vapour compression refrigeration system. During each run of the experiment, the copper block evaporator was placed inside a small wind tunnel where controlled flow of air from a forced draft fan was introduced for the cooling process. The experimental set-up used data acquisition software and computer-aided simulation software was used to simulate the pressure drop and temperature profiles of the evaporator during the experimental run. The results were then compared with the Shah correlation. The Shah correlation over predicted and under predicted the values as compared with the experimental results for all of the three diameters and high variation for Dh=1.0mm. This indicates that the Shah correlation at small diameters is not the appropriate equation for predicting the heat transfer coefficient. The trend of the heat transfer coefficient is increasing as the size of the diameter increases.
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.
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.
Apparent Charge Transfer at Semiconductor Surfaces
International Nuclear Information System (INIS)
We investigate the apparent charge transfer between adatoms in the GeXPb[l.XjGe(lll) interface both experimentally and theoretically. Scanning tunneling microscopy and surface core level measurements suggest significant charge transfer from the Ge adatoms to the Pb adatoms. However, first-principles calculations unambiguously find that the total electronic displacement is negligibly small, and that the results of published experiments can be explained as a result of bond rearrangement
Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media
International Nuclear Information System (INIS)
Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02-0.1 m/s), liquid viscosity (0.1-3 Pa·s) and surface tension (66.1-72.9x10-3 N/m) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; h=2502UG0.236L-0.250L-0.028 Nu=3.25Re0.180Pr-0.067We0.028
Heat Transfer in Bubble Columns with High Viscous and Low Surface Tension Media
Energy Technology Data Exchange (ETDEWEB)
Kim, Wan Tae; Lim, Dae Ho; Kang, Yong [Chungnam National University, Daejeon (Korea, Republic of)
2014-08-15
Axial and overall heat transfer coefficients were investigated in a bubble column with relatively high viscous and low surface tension media. Effects of superficial gas velocity (0.02-0.1 m/s), liquid viscosity (0.1-3 Pa·s) and surface tension (66.1-72.9x10{sup -3} N/m) on the local and overall heat transfer coefficients were examined. The heat transfer field was composed of the immersed heater and the bubble column; a vertical heater was installed at the center of the column coaxially. The heat transfer coefficient was determined by measuring the temperature differences continuously between the heater surface and the column which was bubbling in a given operating condition, with the knowledge of heat supply to the heater. The local heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing axial distance from the gas distributor and liquid surface tension. The overall heat transfer coefficient increased with increasing superficial gas velocity but decreased with increasing liquid viscosity or surface tension. The overall heat transfer coefficient was well correlated in terms of operating variables such as superficial gas velocity, liquid surface tension and liquid viscosity with a correlation coefficient of 0.91, and in terms of dimensionless groups such as Nusselt, Reynolds, Prandtl and Weber numbers with a correlation of 0.92; h=2502U{sub G}{sup 0.236}{sub L}{sup -0.250}{sub L}{sup -}0{sup .028} Nu=3.25Re{sup 0.180}Pr{sup -0.067}We{sup 0.028}.
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Sparrow, E.M.; Abraham, J.P. [University of Minnesota, Minneapolis (United States). Laboratory of Heat Transfer Practice, Department of Mechanical Engineering
2002-08-01
An in-depth experimental study of heat transfer in ovens has provided basic data that is directly applicable to design. Heat transfer coefficients were measured for thermal loads having either black or highly reflective surface finishes. Approximately 100 different data runs were carried out. These heat transfer coefficients enabled the separation of the heat transfer into convective and radiative components, with radiation being the dominant transfer mechanism for blackened loads. The thermal response of the load to the presence of blockages situated either below or above the load was quantified. This response was only slightly affected by the blockages when they were empty of water, but major effects were observed when the blockages were water filled. Major effects were also encountered when the load was supported from below by cookie sheets. On the other hand, extensive investigation of various positions throughout the oven indicated a very weak effect of load position on the thermal response. (author)
International Nuclear Information System (INIS)
In a high-level waste (HLW) repository, heat is generated by the radioactive decay of the waste. This can affect the safety of the repository because the surrounding environment can be changed by the heat transfer through the rock. Thus, it is important to determine the heat transfer coefficient of the atmosphere in the underground repository. In this study, the heat transfer coefficient was estimated by measuring the indoor environmental factors in the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT) under forced convection. For the experiment, a heater of 5 kw capacity, 2 meters long, was inserted through the tunnel wall in the heating section of KURT in order to heat up the inside of the rock to 90 .deg. C, and fresh air was provided by an air supply fan connected to the outside of the tunnel. The results showed that the average air velocity in the heating section after the provision of the air from outside of the tunnel was 0.81 m/s with the Reynolds number of 310,000 ? 340,000. The seasonal heat transfer coefficient in the heating section under forced convection was 7.68 W/m2 K in the summer and 7.24 W/mm2 K in the winter
Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element
Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.
2007-05-01
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.
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
Resonant charge transfer at dielectric surfaces
Marbach, Johannes; Bronold, Franz Xaver; 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 ...
Charge transfer between carbon nanotubes on surfaces
Araujo, Karolline A. S.; Barboza, Ana P. M.; Fernandes, Thales F. D.; Shadmi, Nitzan; Joselevich, Ernesto; Mazzoni, Mario S. C.; Neves, Bernardo R. A.
2015-10-01
The charge transfer between neighboring single-walled carbon nanotubes (SWNTs) on a silicon oxide surface was investigated as a function of both the SWNT nature (metallic or semiconducting) and the anode/cathode distance using scanning probe techniques. Two main mechanisms were observed: a direct electron tunneling described by the typical Fowler-Nordheim model, and indirect electron transfer (hopping) mediated by functional groups on the supporting surface. Both mechanisms depend on the SWNT nature and on the anode/cathode separation: direct electron tunneling dominates the charge transfer process for metallic SWNTs, especially for large distances, while both mechanisms compete with each other for semiconducting SWNTs, prevailing one over the other depending on the anode/cathode separation. These mechanisms may significantly influence the design and operation of SWNT-based electronic devices.
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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)
A measurement technique is presented that uses a new dilatometer measuring device to determine the instantaneous bubble volume and thereby calculate the instantaneous heat transfer coefficients for vaporizing bubbles in an immiscible liquid. Data were taken on single droplets of refrigerant-114 evaporating in water with a nominal initial diameter of 0.8 mm at a temperature difference of 4 K. The results indicate that the heat transfer data for R-114 may be different in the region at the end of evaporation where the vaporization ratio is greater than 50%. The technique used is consistent, accurate and the experimental method is easy to perform
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
Experimental Estimation of Heat Transfer Coefficients Using Helical Coil in an Agitated Vessel
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Ashok Reddy K , Bhavanth Rao M ,Ram Reddy P
2012-04-01
Full Text Available A mathematical model is developed to analyze the heating rates and compare the relation with experimental results obtained in our present study . Low shear rate concentration of sodium carboxymethal cellulose fluids with two different coil lengths 2.362m and 2.82m, diameter of the helical coil equal to 156mm, di=4.0mm and do=6.4mm were used to correlate overall heat transfer coefficients in an agitated vessel with four blade paddle impeller. The model is derived by using velocity flow field and energy equations in cylindrical coordinate for straight tube and later extended to helical coil. The new design relation for obtaining the individual heat transfer coefficient in terms of flow behavior index is equal to
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
Estimation of overall heat transfer coefficient of cooling system in RF capacitive hyperthermia
Mohammad Hasan Zahmatkesh; Seyed Rabii Mahdi Mahdavi; Dariush Sardari; Seyed Ali Aghayan
2013-01-01
The study presented in this article involves the estimation of the overall heat transfer coefficient of cooling system in RF capacitive hyperthermia treatment using inverse problem based on the conjugate gradient method to provide improved distribution of temperature. The temperature data computed numerically from the direct problem using the finite difference time domain method are used to simulate the temperature measurements. The effects of the errors and sensor positions upon the precisi...
Calculating the heat transfer coefficient of frame profiles with internal cavities
DEFF Research Database (Denmark)
Noyé, Peter Anders; Laustsen, Jacob Birck; Svendsen, Svend
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 differenc...
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
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.
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.
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.
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)
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.
Diazo transfer for azido-functional surfaces
Directory of Open Access Journals (Sweden)
Laura Russo
2011-04-01
Full Text Available Preparation of azido-functionalized polymers is gaining increasing attention. We wish to report an innovative, novel strategy for azido functionalization of polymeric materials, coupling plasma technology and solution processed diazo transfer reactions. This novel approach allows the azido group to be introduced downstream of the material preparation, thus preserving its physicochemical and mechanical characteristics, which can be tailored a priori according to the desired application. The whole process involves the surface plasma functionalization of a material with primary amino groups, followed by a diazo transfer reaction, which converts the amino functionalities into azido groups that can be exploited for further chemoselective reactions. The diazo transfer reaction is performed in a heterogeneous phase, where the azido group donor is in solution. Chemical reactivity of the azido functionalities was verified by subsequent copper-catalyzed azide-alkyne cycloaddition.
International Nuclear Information System (INIS)
The friction coefficient between surfaces depends not only on their roughness but also on their relative speed. The aim of this work is to show how the friction coefficient would vary with the relative speed of the two rough surfaces provided accounting affects of their reciprocal correlation. The reciprocal spectral density of the two surfaces is studied in addition to their structure function. It is shown that the reciprocal spectral density has important impacts on the friction coefficient of the surfaces, in a sense that a positive or a negative reciprocal correlation would cause a decrease or an increase in the friction coefficient. In addition, the friction is studied in the context of the relaxation time. It is shown that there is a threshold for the relative velocity of the two surfaces, where by exceeding the threshold velocity the friction coefficient would not increase, but decrease
International Nuclear Information System (INIS)
Although the heat transfer problem of pressurized supercritical water (SCW) flows in around tube has been studied for decades, the subject is still considerably of interest nowadays. This is partly because of the expanded investigation of using SCW for nuclear engineering applications like SCWR which is generation IV reactor and promising advanced nuclear systems because of their high thermal efficiency(i.e., about 45% as opposed to about 33% efficiency for current light water reactors LWRs) and considerable plant simplification. Literature survey shows that heat transfer coefficient (HTC) is sharply enhanced near the pseudo critical temperature. As the heat flux increases, the peak of the HTC decreases. When the heat flux reaches to some high values, heat transfer deterioration (HTD) occurs. CFD code with various turbulence models are being used to evaluate HTC. Modeling of Yamagata's experiment has been carried out for evaluation of HTC using CFD code FLUENT with standard k? turbulence model, nonequilibrium wall function,viscous heating, full buoyancy effect and including wall roughness effect.In this paper model constants for standard k? model have been derived. In the Yamagata experiment, investigations were made for HTC to supercritical water flowing vertically upward in vertical tubes of 10 and 7.5mm internal diameter, at pressures 22.6, 24.5 and 29.5 MPa, bulk temperature from 230 to 540 oC, heat flux 233, 465, 698 and 930kW/m2 and mass flux 1200 kg/m2.s. Two dimensional axisymmetry grid generation has been done using GAMBIT. Inbuilt boundary conditions in the FLUENT are invoked for mass flow rate at inlet,pressure outlet at the outlet of the tube and wall at the cylindrical surface where heat flux is given. Thermo-physical properties are taken from the (IAPWSIF97) and piecewise linear variation are given in the FLUENT for 30 temperature points. Bulk fluid temperature is obtained using user defined function. HTC are obtained based on heat flux, surface temperature and bulk fluid temperature. The calculated HTC is compared with the experimental results and also compared with the results of the other authors. It is observed in both experimental and code calculated values that peak HTC decreases for increase in heat flux for constant mass flux and it is also noticed that peak HTC decreases with the increase in system pressure for constant heat flux. However, it is noticed that magnitude of peak HTC calculated by code is higher than the experimental data especially for higher heat flux and rate of decrease of peak HTC with increase in heat flux is lesser with compared to experimental results. It is observed that peak HTC increases with increase in wall roughness of the tube. It is also observed that HTC calculated by FLUENTcode is in good agreement with the HTC calculated by other authors using CFD code with various turbulence models. (author)
International Nuclear Information System (INIS)
Detailed heat transfer coefficient distributions on two types of gas turbine blade tip, plane tip and squealer tip, were measured using a hue-detection base transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of the blade were also measured. The heat transfer measurements were taken at the three different tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span. Results show the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. By using squealer tip, however, the reductions of heat transfer coefficients near the tip regions of the pressure and suction sides were not remarkable
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.
Energy Technology Data Exchange (ETDEWEB)
Devgan, Seema; Jain, A.K.; Bhattacharjee, B. [Department of Civil Engineering, Indian Institute of Technology, Hauz khas, New Delhi 110016 (India)
2010-10-15
This paper attempts to formulate Overall Thermal Transfer Value (OTTV) coefficients for Composite, Hot-Dry and Warm-Humid climates, the three main tropical climates in India. Four existing air-conditioned office buildings - two mid-rise and two high-rise were modeled as case studies using eQuest v.3.6, which is a DoE2.2, based building energy simulation tool. Based on the study of building envelope, loads, operation and HVAC system characteristics of these case study buildings, a hypothetical high-rise, 16 storey office building, octagonal in plan was created for parametric studies. 98 types of opaque exterior wall constructions and 93 types of glass constructions were varied sequentially in parametric runs to obtain results for hourly wall conduction, glass conduction and glass radiation heat flow in eight orientations for each of the climate type. These hourly results were processed to obtain annual heat gain intensities for each parametric case for all three modes of heat transfer. Regression analysis was used to obtain the OTTV coefficients -TD{sub eq}, DT and SF for the three climates. A new OTTV equation is obtained and presented. The set of coefficients obtained were verified by calculating the OTTV for the four case study buildings, for various parametric runs. The computed OTTV for the four case study buildings exhibits good linear correlation with the annual space cooling plus heating energy use in three climates. (author)
Condition monitoring of steam generator by estimating the overall heat transfer coefficient
International Nuclear Information System (INIS)
This study develops a technique for monitoring in on-line the state of the steam generator of the fast-breeder reactor (FBR) “Monju”. Because the FBR uses liquid sodium as coolant, it is necessary to handle liquid sodium with caution due to its chemical characteristics. The steam generator generates steam by the heat of secondary sodium coolant. The sodium-water reaction may happen if a pinhole or crack occurs at the thin metal tube wall that separates the secondary sodium coolant and water/steam. Therefore, it is very important to detect an anomaly of the wall of heat transfer tubes at an early stage. This study aims at developing an on-line condition monitoring technique of the steam generator by estimating overall heat transfer coefficient from process signals. This paper describes simplified mathematical models of superheater and evaporator to estimate the overall heat transfer coefficient and a technique to diagnose the state of the steam generator. The applicability of the technique is confirmed by several estimations using simulated process signals with artificial noises. The results of the estimations show that the developed technique can detect the occurrence of an anomaly. (author)
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.
Energy Technology Data Exchange (ETDEWEB)
Bennion, Kevin; Moreno, Gilberto
2015-09-29
Thermal management for electric machines (motors/ generators) is important as the automotive industry continues to transition to more electrically dominant vehicle propulsion systems. Cooling of the electric machine(s) in some electric vehicle traction drive applications is accomplished by impinging automatic transmission fluid (ATF) jets onto the machine's copper windings. In this study, we provide the results of experiments characterizing the thermal performance of ATF jets on surfaces representative of windings, using Ford's Mercon LV ATF. Experiments were carried out at various ATF temperatures and jet velocities to quantify the influence of these parameters on heat transfer coefficients. Fluid temperatures were varied from 50 degrees C to 90 degrees C to encompass potential operating temperatures within an automotive transaxle environment. The jet nozzle velocities were varied from 0.5 to 10 m/s. The experimental ATF heat transfer coefficient results provided in this report are a useful resource for understanding factors that influence the performance of ATF-based cooling systems for electric machines.
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.
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
The role of surface energy coefficients and nuclear surface diffuseness in the fusion of heavy-ions
Dutt, Ishwar; Puri, Rajeev K
2010-01-01
We discuss the effect of surface energy coefficients as well as nuclear surface diffuseness in the proximity potential and ultimately in the fusion of heavy-ions. Here we employ different versions of surface energy coefficients. Our analysis reveals that these technical parameters can influence the fusion barriers by a significant amount. A best set of these parameters is also given that explains the experimental data nicely.
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
Effect of Mass on Convective Heat Transfer Coefficient During Onion Flakes Drying
G. N. Tiwari; Anil Kumar, *
2006-01-01
In this present study an open sun and greenhouse drying of onion flakes has been performed to study the effect of mass on convective heat transfer coefficient. Three sets of experiments with total quantity of onion as 300, 600 and 900 g were done. The onion was continuously dried for 33 h both in open sun and in the roof type even span greenhouse with floor area of 1.2 x 0.78 m2. Experiments were carried out during the months of October to December 2003 at IIT Delhi (28°35`N 72°12`E). Experim...
Directory of Open Access Journals (Sweden)
S. I. ANWAR
2012-10-01
Full Text Available In this paper, convective heat transfer coefficient of Indian gooseberry (Emblica officinalis, in three different forms (shreds, slices and pieces, under forced convection mode has been determined. These forms were dried in laboratory drier. Values of constants C and n have been determined using experimental data and regression analysis for calculating values of convective heat transfer coefficient. It was found that the convective heat transfer coefficient varies with form of commodity being dried and decreases as the drying progresses. The value of convective heat transfer coefficient was highest for shredded form (30.39 W/m2oC followed by slices (25.88 W/m2oC and pieces (18.67 W/m2oC when compared at certain final moisture content. The data were also analyzed for per cent uncertainty.
A review of measured values of the milk transfer coefficient (fsub(m)) for iodine
International Nuclear Information System (INIS)
Most published assessments of the environmental transport of iodine have used a value of 1 X 10-2 days per litre (d/1) for the transfer coefficient (fsub(m)) which relates the concentration per litre of milk to the daily amount of the element ingested by a cow. However, the USNRC has recommended (USNRC 77) a value of 0.6 X 10-2 d/1 for the transfer of iodine to cow's milk and 6 X 10-2 d/1 for goat's milk. A literature survey of published values of fsub(m) leads to a recommendation which deviates from the values chosen by the USNRC. An fsub(m) of 0.5 d/1 for goat's milk and an fsub(m) of 1 X 10-2 for cow's milk appear to be more appropriate. (author)
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)
DEFF Research Database (Denmark)
Nielsen, Anders Michael; Nielsen, Lars Peter; Feilberg, Anders; Christensen, Knud Villy
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...
International Nuclear Information System (INIS)
Forced convective heat transfer coefficient and pressure drop of SiO2- and Al2O3-water nanofluids were characterized. The experimental facility was composed of thermal-hydraulic loop with a tank with an immersed heater, a centrifugal pump, a bypass with a globe valve, an electromagnetic flow-meter, a 18 kW in-line pre-heater, a test section with band heaters, a differential pressure transducer and a heat exchanger. The test section consists of a 1000 mm long aluminium pipe with an inner diameter of 31.2 mm. Eighteen band heaters were placed all along the test section in order to provide a uniform heat flux. Heat transfer coefficient was calculated measuring fluid temperature using immersed thermocouples (Pt100) placed at both ends of the test section and surface thermocouples in 10 axial locations along the test section (Pt1000). The measurements have been performed for different nanoparticles (Al2O3 and SiO2 with primary size of 11 nm and 12 nm, respectively), volume concentrations (1% v., 5% v.), and flow rates (3 103Re5). Maximum heat transfer coefficient enhancement (300%) and pressure drop penalty (1000%) is obtained with 5% v. SiO2 nanofluid. Existing correlations can predict, at least in a first approximation, the heat transfer coefficient and pressure drop of nanofluids if thermal conductivity, viscosity and specific heat were properly modelled.
Transfer of tritiated water vapour to and from land surfaces
International Nuclear Information System (INIS)
Deposition of tritiated water vapour may result in contamination of food supplies and reduction of air concentrations, but the process has received little attention. Field and laboratory experiments were undertaken to investigate the mechanisms involved. The exchange between air and ground involves turbulent transfer in the atmosphere near the surface and diffusion within the soil. The exchange velocity for moist soil was limited by atmospheric mixing to about 1 cms-1, and was only a little smaller at dry soil and grass surfaces. For exposure times exceeding a few minutes re-evaporation becomes significant, reducing the net rate of uptake, but the total amount deposited continues to increase as the tritiated water diffuses deeper into the soil. Diffusion in soil was investigated and a simple equation proposed to predict the effective diffusion coefficient. Tritiated water deposited during a brief exposure in the field evaporated from the surface during several weeks, and its behaviour can be described by the diffusion equation with a suitable boundary condition. Rain washes activity into the soil and impedes further evaporation. Most of the vapour will interact with the surface within two or three days of release, and transport over continental distances will be retarded as a result. The effect of surface exchange on the distribution of doses following a release of tritiated water vapour will be complicated by changes in the weather over a period of several weeks, and will be difficult to foresee. (author)
Reconstruction of the heat transfer coefficient on the grounds of experimental data
Directory of Open Access Journals (Sweden)
D. S?ota
2009-05-01
Full Text Available Purpose: Solidification of pure metal can be modelled by a two-phase Stefan problem, in which the distribution of temperature in the solid and liquid phases is described by the heat conduction equation with initial and boundary conditions. The inverse Stefan problem can be applied to solve design problems in casting process.Design/methodology/approach: In numerical calculations the alternating phase truncation method, the Tikhonov regularization and the genetic algorithm were used. The featured examples of calculations show a very good approximation of the experimental data.Findings: The verification of the method of reconstructing the cooling conditions during the solidification of pure metals. The solution of the problem consists of selecting the heat transfer coefficient on the boundary, so that the temperature in selected points on the boundary of the domain assumes given values.Research limitations/implications: The method requires that it must be possible to describe the sought boundary condition by means of a finite number of parameters. It is not necessary, that the sought boundary condition should be linearly dependent on those parameters.Practical implications: The presented method can be easy applied to solve design problems of different types, e.g. for the design of continuous casting installations (incl. the selection of the length of secondary cooling zones, the number of jets installed in individual zones, etc..Originality/value: Verification, on the grounds of experimental data, the formerly devised method of determining the heat transfer coefficient during the solidification of pure metals.
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
Volumetric mass transfer coefficient and hydrodynamic study of a new self-inducing turbine
International Nuclear Information System (INIS)
Highlights: • Experimental study of a new self inducing turbine. • Hydrodynamic parameters study of the generated flow. • Experimental study of the evolution of kLa and we give an empirical correlation. • Comparing our results to a previous research [17]. • Find a good agreements, with better performances of our turbine. - Abstract: The self-inducing turbines are among mobile agitations which present a very interesting potential in terms of energy in the field of wastewater treatment by activated sludge. Often, the reactions involved in this type of contactors are limited by the gas–liquid mass transfer. The objective of this experimental work is the determination of the oxygenation capacity of a new self-inducing turbine, a holed hollow cylinder, having a thickness of W = 1.5 cm and a diameter D = 9 cm, with 6 holes having a diameter of 0.5 cm each. During this experimental work, we evaluated the volumetric mass transfer coefficient kLa, which is directly related to the oxygenation capacity (OC) and this for various rotational speeds of the turbine as well as for various submergences. We finally succeeded to find an empirical correlation for our new self inducing turbine. The most common method used to estimate experimentally the coefficient kLa is the technique of dynamic oxygenation and deoxygenation. We finally concluded that this new turbine had a satisfying aeration capacity, which increases with the increase of the rotational speed, and decreases when increasing the submergence of the impeller
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.
Surface diffusion coefficients by thermodynamic integration: Cu on Cu(100)
Boisvert, Ghyslain; Mousseau, Normand; Lewis, Laurent J.
1998-01-01
The rate of diffusion of a Cu adatom on the Cu(100) surface is calculated using thermodynamic integration within the transition state theory. The results are found to be in excellent agreement with the essentially exact values from molecular-dynamics simulations. The activation energy and related entropy are shown to be effectively independent of temperature, thus establishing the validity of the Arrhenius law over a wide range of temperatures. Our study demonstrates the equ...
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
Pool Boiling Heat Transfer on the Inside Surface of an Inclined Tube
International Nuclear Information System (INIS)
The present study is aimed at the determination of heat transfer characteristics on the inside surface of a tube while changing the inclination angle. Changes in pool boiling heat transfer coefficients on the inside surface of a 16.2 mm internal diameter has been studied experimentally at atmospheric pressure. Experiments were performed at six different inclination angles to investigate variations in the heat transfer coefficients due to the inclination angle change. Results for 30 .deg.???90 .deg. are almost same whereas the result for ? =15 .deg. is different from the other angles. To predict the heat transfer coefficients an empirical correlation has been developed as ?b 1/(A + Blnq). The developed correlation can predict the measured experimental data within ±4% error bound. Pool boiling is closely related with the design of passive type heat exchangers, which have been investigated in nuclear power plants to achieve safety functions in case of no power supply. Since the space for the installation of a heat exchanger is usually limited, developing more efficient heat exchangers is important. Several researchers have published results for the pool boiling on the outside surface. Jung et al. experimented boiling heat transfer in R-11 to investigate heat transfer mechanisms on the inside surface of a circular cylindrical tank. They simulated the surface by a flat plate. Somewhat detailed study on the inclination angle itself was previously done by Nishikawa et al. by using the combination of a plate and water. Jabardo and Filho performed an experimental study of forced convective boiling of refrigerants in a 12.7 mm internal diameter tube to investigate effects of physical parameters over the variations in local surface temperature. However, mechanisms of pool boiling are much different from those of the forced convective boiling. Kang investigated pool boiling heat transfer of water on the inside surface of a horizontal tube at atmospheric pressure. Experiments were performed at four different azimuthal angles to investigate variations in local heat transfer coefficients along the tube periphery. The local coefficient changes much along the tube periphery and the minimum was observed at the tube bottom. Summarizing the previous works, it is identified that the study for pool boiling heat transfer on the inside surface of a tube is very rare
International Nuclear Information System (INIS)
In the search for a deeper understanding of the factors governing the stability of liquid metal field-ion emitters, the behaviour of a liquid anode with an anomalous surface tension coefficient is studied. The main parameter in this experimental study is the emitter temperature. At the conclusion of the work an important result emerged: apart from the surface tension coefficient, space-charge effects constitute a major factor influencing emitter stability
Tailoring of Seebeck coefficient with surface roughness effects in silicon sub-50-nm films
Kumar, Manoj; Bagga, Anjana; Neeleshwar, S
2012-01-01
The effect of surface roughness on the Seebeck coefficient in the sub-50-nm scale silicon ultra thin films is investigated theoretically using nonequilibrium Green's function formalism. For systematic studies, the surface roughness is modelled by varying thickness periodically with square wave profile characterized by two parameters: amplitude (A0) and wavelength (?). Since high Seebeck coefficient is obtained if the temperature difference between the ends of device produces higher currents a...
International Nuclear Information System (INIS)
Experimental data on heat transfer of finning tubes transversely stream-lined by the gas flow in a gas-liquid heat exchangers are generalized. Effect of staggered bundle geometrical parameters and tube finning coefficient on the heat transfer in a gas flow is considered
Determination of the pressure drop and the heat transfer coefficient in a gas-solid two-phase flow
International Nuclear Information System (INIS)
An experimental study was developed for a vertical gas solid two phase flow with heat transfer by analysing the gradient of both static pressure and temperature alongside the system. The measurements were used to produce the isothermal hydrodynamic entry lenght and the gas-solid heat transfer coefficient as well as the influence of the solid particle. (Author)
Surface diffusion coefficients by thermodynamic integration Cu on Cu(100)
Boisvert, G; Lewis, L J; Boisvert, Ghyslain; Mousseau, Normand; Lewis, Laurent J.
1998-01-01
The rate of diffusion of a Cu adatom on the Cu(100) surface is calculated using thermodynamic integration within the transition state theory. The results are found to be in excellent agreement with the essentially exact values from molecular-dynamics simulations. The activation energy and related entropy are shown to be effectively independent of temperature, thus establishing the validity of the Arrhenius law over a wide range of temperatures. Our study demonstrates the equivalence of diffusion rates calculated using thermodynamic integration within the transition state theory and direct molecular-dynamics simulations.
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.
Hayashi, M.; Sakurai, A.; Aso, S.
1986-01-01
A thin film heat transfer gauge is applied to the measurement of heat transfer coefficients in the interaction regions of incident shock waves and fully developed turbulent boundary layers. It was developed to measure heat flux with high spatial resolution and fast response for wind tunnels with long flow duration. To measure the heat transfer coefficients in the interaction region in detail, experiments were performed under the conditions of Mach number = 4, total pressure = 1.2 MPa, 0.59 to approximately 0.65. Reynolds number = 1.3 to approximately 1.5 x 10 to the 7th power and incident shock angles from 17.8 to 22.8 degrees. The results show that the heat transfer coefficient changes complicatedly in the interaction region. At the beginning the interaction region, the heat transfer coefficient decreases at first, reaches its minimum value at the point where the pressure begins to increase, and then increases sharply. When the boundary layer begins to separate, even a small separation bubble causes significant changes in the heat transfer coefficient, while the pressure does not show any changes which suggests that the boundary layer begins to separate.
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
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)
International Nuclear Information System (INIS)
Some studies on direct-contact condensation in cocurrent stratified flow of steam and subcooled water were reviewed. Several approaches have been performed to develop the condensation heat transfer coefficient relationship. The local Nusselt number is correlated in terms of the local water Reynolds and Prandtl numbers as well as the steam Froude number. In addition, a turbulence-centered model, developed principally for gas absorption in several geometries, is modified by using calculated interfacial parameters for the turbulent velocity and length scales. These approaches result in a fairly good agreement with the data, whereas, the turbulence-centered model is here recommended since it is based on the turbulent properties which may be closely related to the condensation phenomena. (Author)
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
Determination of surface tension coefficient of liquids by diffraction of light on capillary waves
International Nuclear Information System (INIS)
This paper describes a simple technique for determining the coefficient of the surface tension of liquids, based on laser light diffraction on capillary waves. Capillary waves of given frequency are created by an exciter needle acting on the surface of liquid and represent a reflective diffraction grating, the constant of which (the wavelength of capillary waves) can be determined based on a known incidence angle of light (grazing angle). We obtain the coefficient of the surface tension of liquids by applying the dispersion relation for capillary waves and analyze the difficulties that arise when setting up and conducting the experiment in detail. (paper)
Exergoeconomic Analysis on Enhanced Heat Transfer Surfaces at Low Temperature
Ruan, Deng-Fang; Li, You-Rong; Wu, Shuang-Ying; Lan, Bo
The exergoeconomic analysis is carried out on enhanced heat transfer surfaces at low temperature. A new criterion for evaluating the performance of enhanced heat transfer surfaces at low temperature is proposed. It can be applied to various augmentation techniques and generalizes the performance evaluation criteria obtained by means of the first and second law analysis. The validity of the new performance evaluation criterion is illustrated by the analysis of heat transfer characteristics at low temperature and assessment of the heat transfer cost of two types of enhanced heat transfer surfaces.
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
Simulation of Convective Heat-Transfer Coefficient in a Buried Exchanger
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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.
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...
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)
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)
Hodge, S.A.
1980-08-01
The friction factor and Stanton number for flow past a roughened surface are determined by the parameters A and R(h/sup +/) of the universal law of friction and A/sub H/ and G(h/sup +/) of the universal law of heat transfer. The methods to be used for determination of these parameters for the particular roughness to be used in the Core Flow Test Loop (CFTL) are presented. Examples are given concerning the application of these methods to both transitional and fully rough flow using experimental results taken from the literature.
Energy Technology Data Exchange (ETDEWEB)
Sahin, Haci Mehmet [Gazi Ueniversitesi, Teknik Egitim Fakueltesi, Teknikokullar, Ankara 06503 (Turkey)]. E-mail: mesahin@gazi.edu.tr; Kocatepe, Kadir [Gazi Ueniversitesi, Teknik Egitim Fakueltesi, Teknikokullar, Ankara 06503 (Turkey); Kayikci, Ramazan [Sakarya Ueniversitesi, Teknik Egitim Fakueltesi, Sakarya (Turkey); Akar, Neset [Gazi Ueniversitesi, Teknik Egitim Fakueltesi, Teknikokullar, Ankara 06503 (Turkey)
2006-01-15
In this study, the interfacial heat transfer coefficient (IHTC) for vertically upward unidirectional solidification of a eutectic Al-Si casting on water cooled copper and steel chills was measured during solidification. A finite difference method (FDM) was used for solution of the inverse heat conduction problem (IHCP). Six computer guided thermocouples were connected with the chill and casting, and the time-temperature data were recorded automatically. The thermocouples were placed, located symmetrically, at 5 mm, 37.5 mm and 75 mm from the interface. As the lateral surfaces are very well heat isolated, the unidirectional solidification process starts vertically upward at the interface surface. The measured time-temperature data files were used by a FDM using an explicit technique. A heat flow computer program has been written to estimate the transient metal-chill IHTC in the IHCP. The experimental and calculated temperatures have shown excellent agreement. The IHTC during vertically upward unidirectional solidification of an Al-Si casting on copper and steel chills have varied between about 19-9.5 kW/m{sup 2} K and 6.5-5 kW/m{sup 2} K, respectively.
International Nuclear Information System (INIS)
In this study, the interfacial heat transfer coefficient (IHTC) for vertically upward unidirectional solidification of a eutectic Al-Si casting on water cooled copper and steel chills was measured during solidification. A finite difference method (FDM) was used for solution of the inverse heat conduction problem (IHCP). Six computer guided thermocouples were connected with the chill and casting, and the time-temperature data were recorded automatically. The thermocouples were placed, located symmetrically, at 5 mm, 37.5 mm and 75 mm from the interface. As the lateral surfaces are very well heat isolated, the unidirectional solidification process starts vertically upward at the interface surface. The measured time-temperature data files were used by a FDM using an explicit technique. A heat flow computer program has been written to estimate the transient metal-chill IHTC in the IHCP. The experimental and calculated temperatures have shown excellent agreement. The IHTC during vertically upward unidirectional solidification of an Al-Si casting on copper and steel chills have varied between about 19-9.5 kW/m2 K and 6.5-5 kW/m2 K, respectively
International Nuclear Information System (INIS)
An experimental study on forced convection in a four-cusp duct simulating a typical nuclear reactor channel degraded by accident is presented. Transfer coefficients were obtained by using the analogy between heat and mass tranfer, with the naphtalene sublimation technique. The experiment consisted in forcing air past a four-cusp naphthalene moulded duct. Mass transfer coefficients were determined in nondimensional form as Sherwood number. Experimental curves correlating the Sherwood number with a nondimensional length, x+, were obtained for Reynolds number varying from 891 to 30.374. This range covers typical flow rates that are expected to exist in a degraded nuclear reactor core. (Author)
Impact of External Pressure on the Heat Transfer Coefficient during Solidification of Al-A356 Alloy
DEFF Research Database (Denmark)
Jabbari, Masoud; Ilkhchy, A.Fardi
In this paper the interfacial heat transfer coefficient (IHTC) is correlated to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of the 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 and compared with data in literature which shows acceptable agreement.
Miyabe, K; Guiochon, G
1999-01-01
The experimental results of a previous study of the mass transfer kinetics of bovine serum albumin (BSA) in ion-exchange chromatography under nonlinear conditions are reevaluated. The analysis of the concentration dependence of the lumped mass-transfer rate coefficient (k(m,L)) provides information on the kinetics of axial dispersion, fluid-to-particle mass transfer, intraparticle mass transfer, and adsorption/desorption. The new analysis shows that the contribution of intraparticle mass transfer is the dominant one. Similar to k(m,L), the surface diffusivity (D(s)) of BSA increases with increasing concentration. The linear concentration dependence of k(m,L) seems to originate in a similar dependence of D(s). The use of an heterogeneous-surface model for the anion-exchange resin provides an explanation of the positive concentration dependence of D(s). This work illustrates how frontal analysis data can be used for a detailed investigation of the kinetics of mass transfer between the phases of a chromatographic column, in addition to its conventional use in the determination of the thermodynamic characteristics of the phase equilibrium. PMID:10441366
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.
Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces
Kim, Hyunsik; Nam, Youngsuk
2014-11-01
We investigated condensate mobility and resulting heat transfer performance on Cu based water repellent surfaces including hydrophobic, superhydrophobic and oil-infused surfaces. We observed the transient microscale condensation behaviours up to 3 hours with controlling the supersaturation level at 1.64. We experimentally characterized the nucleation density, droplet size distribution and growth rate, and then incorporated them into the developed condensation heat transfer model to compare the condensation heat transfer performance of each surface. Due to the spontaneous coalescence induced jumping, superhydrophobic surface can maintain the high heat transfer performance while other surfaces show a gradual decrease in heat transfer performance due to the increase in the thermal resistance across the growing droplets. We also quantified each thermal resistance values from the vapor to the surface through the droplets to find out the relative importance of each thermal resistance term.
Critical temperatures and temperature coefficients of the surface tension of liquid metals
International Nuclear Information System (INIS)
It is unlikely that the temperature coefficient of liquid surface tension of approximately 50% of the elements will ever be determined because of experimental difficulties. After having given a method of estimating the surface tension at the melting point of such elements in a previous publication, here a possible very simple way of calculating the temperature coefficient is suggested. In addition, numerical values for the critical temperatures of all metals up to the atomic number 95, whose experimental determination will certainly be limited to low melting elements for quite a long time, are given for the first time. (orig.)
Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer
Directory of Open Access Journals (Sweden)
I. N. Esau
2004-11-01
Full Text Available Modern large-scale models (LSMs rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer, the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate.
The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients.
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)
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.; Sun, K. H.
1976-01-01
The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer coefficient versus the film length is obtained. The Helmholtz instability for the steam-liquid interface is analyzed, and it is shown that films beyond a certain length are unstable. Assuming the most unstable w...
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.
International Nuclear Information System (INIS)
Using 86Rb as a tracer the effective diffusion coefficient in the resin phase has been determined by direct measurement of the change in the ion concentration. The evaluation of the charging curves was carried out graphically by comparing the experimental curves with theoretical ones, taking into account liquid phase mass transfer
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.
Studying heat transfer enhancement for water boiling on a surface with micro- and nanorelief
Kuzma-Kichta, Yu. A.; Lavrikov, A. V.; Shustov, M. V.; Chursin, P. S.; Chistyakova, A. V.; Zvonarev, Yu. A.; Zhukov, V. M.; Vasil'eva, L. T.
2014-03-01
We present the results from a study of heat transfer enhancement for bulk water boiling at atmospheric pressure on a surface with micro- and nanorelief, including a relief formed from silicon carbide and aluminum oxide nanoparticles. Horizontally oriented steel tube 1.2 mm in diameter and copper plate 15 × 3 mm in size were selected as test sections. The process was recorded by means of a video camera, and the values of heat transfer, critical heat fluxes, and contact angles were measured. The use of surface with micro- and nanorelief makes it possible to obtain a significantly higher critical heat flux and boiling heat transfer coefficient owing to a change of surface wettability. The results of investigations can find use in compact heat exchangers, refrigerating plants, heat pipes, in the mirrors of high-capacity lasers, in the targets and resonators of charged particle accelerators and for external cooling of reactor vessels under emergency conditions.
International Nuclear Information System (INIS)
Experimental condensing heat transfer coefficients for R-114 flowing in a horizontal tube were compared with those calculated by the classical Nusselt correlation and with a new prediction method of Rohsenow. It was determined that the Rohsenow method provides satisfactory agreement with the experimental data and that the coefficients calculated by the Nusselt correlation were much too low. A concurrent study of flow regimes was also made by observing the flow patterns in a glass section just downstream of the condensing section. The regimes observed agree reasonably well with a Baker map that was previously developed from theoretical considerations. An improved correlation was also developed for estimating the inside heat transfer coefficients for water in an annulus
Surface diffusion coefficient near first-order phase transitions at low temperatures
Medved, Igor; Trnik, Anton
2012-01-01
We analyze the collective surface diffusion coefficient, $D_c$, near a first-order phase transition at which two phases coexist and the surface coverage, $\\te$, drops from one single-phase value, $\\te_+$, to the other one, $\\te_-$. Contrary to other studies, we consider the temperatures that are sufficiently sub-critical. Using the local equilibrium approximation, we obtain, both numerically and analytically, the dependence of $D_c$ on the coverage and system size, $N$, near...
Directory of Open Access Journals (Sweden)
Maciejewska Beata
2012-04-01
Full Text Available The paper presents the FEM method for determination of boiling heat transfer coefficient in cooling liquid flow in a rectangular minichannel with asymmetric heating. Experimental research has focused on the transition from single phase forced convection to nucleate boiling, i.e. the zone of boiling incipience. The “boiling front” location has been determined from the temperature distribution of the heated wall obtained from liquid crystal thermography. The main part of the test section has been a minichannel of pre-set depth from 0.7 to 2.0 mm, of different spatial orientations. Local values of heat transfer coefficient have been determined following the solution of the two-dimensional inverse heat transfer problem. This problem has been solved with the use of Trefftz functions. Trefftz functions have been used to construct base functions in the finite element method (FEMT.
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)
The goat milk transfer coefficient of Tc administered as TcO4- was found to be 20 to 40 times that of Tc administered in a reduced form. The fraction of Tc, as TcO4-, transferred from gut to blood was approximately 6 to 10 times that of reduced Tc. The milk transfer coefficient of Tc administered as TcO4- was 6 to 8 times greater for goats than cows. The fraction of Tc, as TcO4-, absorbed from the gut by cows, however, was approximately twice that absorbed by goats. The mean time for loss of Tc in cows' milk based on the average values plotted in Figure 2 was approximately 10 hours. The fraction of Tc, administered as TcO4-, absorbed from blood to mammary gland by cows was estimated to be approximately 2% that of goats. 4 refs., 15 tabs
Takahashi, Yasushi; Gokan, Yoshitsugu; Inayoshi, Makoto; Ishima, Tsuneaki; Obokata, Tomio
Cooling performance is a significant issue for air-cooled motorcycle engines, because its performance depends on the vehicle motion. Commonly, a heat transfer coefficient is calculated by heat flux and temperature difference, which are solved by energy equation under conjugated condition between a solid and a fluid. However, this method is complicated. Therefore, Karman's analogy based on a relation between the fluid friction and the heat transportation was used to obtain a heat transfer coefficient without solving an energy equation. Partial Cells in Cartesian coordinate method was employed as a CFD (Computational Fluid Dynamics) method for an efficient calculation around complex obstacles. Characteristics of heat transfer in a straight pipe were confirmed by a comparison with the Colburn's empirical formula. The results showed good agreement within ±10% differences under Pr=0.7 and 104motorcycle engine was shown. From the above, a new approach of heat analysis by a CFD was proposed.
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.
International Nuclear Information System (INIS)
Determination of velocity coefficient for gas flow transfer across the natural sea surface into the atmosphere (Kv) was attempted by means of radon method on board the SRS Academician Alexander Nesmeyanov (July-August 1992). The measurements were conducted in the Bering Sea, the Okhotsk Sea and in the North Pacific Ocean. It is shown that the total range of the Kv observed values equaled from 1.8 up to 5.4 m.day, which is within the known limits for other regions of the world ocean. 9 refs., 1 fig
DEFF Research Database (Denmark)
Rong, Li; Nielsen, Peter V.; Zhang, Guoqiang
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 exper...
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
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
Pathak, Mihir G.; Mulcahey, Thomas; Ghiaasiaan, S. Mostafa
2012-06-01
Solid-fluid thermal interactions during unsteady flow in porous media play an important role in the regenerators and heat exchangers of pulse tube cryocoolers. Porelevel thermal processes in porous media under laminar unsteady flow conditions have recently been investigated and have been shown to produce significantly larger heat transfer coefficients compared to those in steady flow [1]. The objective of this investigation was to study pore-level hydrodynamic and thermal phenomena during pulsating sinusoidal flow through a generic, two-dimensional porous medium by numerical analysis. The investigated porous media are periodic arrays of rectangular cylinders, and are meant to represent tube bundles in micro heat exchangers. Furthermore, an examination of the effects of flow pulsations on the drag and heat transfer coefficients that are encountered in the standard, volume-average energy equations was carried out. Detailed numerical data for the typical 75% porous configuration, with flow pulsation frequencies of 20, 40, and 80 Hz were obtained at mean flow - Reynolds numbers in the range 0-1000. Based on these numerical results, the instantaneous as well as cycle-average drag coefficients and heat transfer coefficients, to be used in the standard unsteady volume- average momentum and energy conservation equations, were derived.
Effects of surface wettability on fast liquid transfer
Chen, H.; Tang, T.; Amirfazli, A.
2015-11-01
A systematic experimental study was performed to understand the role of surface contact angles in affecting the process of fast liquid transfer. Surfaces with different wettabilities were used, and the transfer ratio (?, the amount of liquid transferred to the acceptor surface over the total amount of liquid) was measured for each pair of surfaces. A numerical model based on the volume of fluid method was developed to help understand the experimental results. The surface wettability was shown to significantly affect the boundaries between three regimes based on stretching speeds: quasi-static (surface force dominated), transition (surface/viscous/inertia forces all important) and dynamic (viscous/inertia forces dominated). Specifically, the values of the boundary speeds were found to increase with |?0 - 0.5|, where ?0 is the transfer ratio in the quasi-static regime, and ?0 is governed by the surface receding contact angles. Based on our results, an empirical equation to describe the transfer ratio as function of stretching speed was proposed. This equation can also be used as a prediction tool for the value of ? for a fast transfer system.
Cheng, Jiangtao
2015-03-01
We report the effects of surface roughness on contact line friction coefficient (CLFC) of water droplets on micro- and nano-patterned surfaces. Both advancing and receding CLFCs have been measured on smooth, one-tier (with micropillars), and two-tier (with CNTs grown on micropillars) surfaces. In comparison with smooth surface, superhydrophobic surfaces can decrease both the advancing and receding CLFCs by more than 10 times. However, droplets on one-tier surfaces exhibit different dynamic behaviors in advancing and receding movements. We investigated the Wenzel-Cassie state transition on micropillar structures and found that the receding motion of a droplet on micropillars is dominated by the Wenzel model with significant receding contact line pinning, which leads to higher receding CLFC. However, rolling mechanism of liquid particles near the advancing contact line controls the advancing motion of a droplet on micropillars. There is a high tendency for an advancing droplet to exhibit Cassie-type behavior on one-tier surfaces and hence advancing CLFC is considerably mitigated. On two-tier superhydrophobic surfaces, it is the Cassie-Baxter behavior that dominates both the advancing and receding contact line motions giving rise to less friction coefficients.
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)
International Nuclear Information System (INIS)
Overall mass transfer coefficients as a function of time for the transfer of uranium between nitric acid and tri-butyl phosphate have been measured using the quasi-steady state droplet technique. The time dependence of the mass transfer coefficient is known to be a result of a corresponding decrease in the frequency of interfacial turbulence as the interface ages. The present study reports several supporting experiments carried out in an attempt to gain a better understanding of this phenomenon. The experimental conditions investigated concentrated on the extraction of uranyl nitrate into and from tri-n-butylphosphate, and included measurements of the mass transfer coefficients to examine the effect of solute loading of the solvent continuous phase, the effect of drop size, and the effect of a change of solvent phase diluent. A study of the backwashing of uranyl nitrate, in which interfacial turbulence is not observed, from the solvent phase to an aqueous one was made. An explanation for the cause of the dampening of interfacial turbulence is proposed and discussed. (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...
Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L
2013-04-01
Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed. PMID:23434811
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)
Experimental assignment of total drag coefficients of bodies embedded in a free surface stream.
Czech Academy of Sciences Publication Activity Database
Chára, Zden?k; Vlasák, Pavel
Praha : Institute of Theoretical and Applied Mechanics AS CR, 2003, s. -. [Engineering mechanics 2003 : national conference with international participation. Svratka (CZ), 12.05.2003-15.05.2003] R&D Projects: GA ?R GA103/03/0724; GA ?R GA103/00/1620; GA ?R GA103/03/0346 Institutional research plan: CEZ:AV0Z2060917 Keywords : total drag coefficients * free surface stream Subject RIV: BK - Fluid Dynamics
Trumi? B.; Stankovi? D.; Truji? V.
2009-01-01
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 incre...
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 wi...
Correlation of the surface layer stress coefficient and stress corrosion cracking. II
International Nuclear Information System (INIS)
Analytical expressions are presented that relate the crack velocity and the failure time to the surface-layer stress coefficient for compact-tension specimens of Ti--6Al--4V and a 4130 steel subjected to stress corrosion cracking (SCC). The experimental data for the threshold stress intensity factor and the crack velocities for various stress intensity factors agree well with the calculated values
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.
Resonant enhancement of charge transfer through surface states
Dick, R.
2002-10-01
A model is proposed that treats electrons at surfaces as a combination of two-dimensional and three-dimensional degrees of freedom. This yields a simple formula for the surface state induced resonant enhancement of the transfer of electrons through a surface. The model also yields analytic approximations for the transition between two-dimensional and three-dimensional distance laws in the correlations between electrons in surface states.
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.
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.
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; Davami, P.
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 h...
Impact of External Pressure on the Heat Transfer Coefficient during Solidification of Al-A356 Alloy
DEFF Research Database (Denmark)
Jabbari, Masoud; Ilkhchy, A.Fardi; Moumani, E.
2012-01-01
In this paper the interfacial heat transfer coefficient (IHTC) is correlated to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of the 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 hea...
International Nuclear Information System (INIS)
In the present study, the effect of delta-wing vortex generators(DWVG) on the local heat transfer of the plate fin-oval tube was experimentally analyzed for Reynolds numbers for 2000, 2500 and 3200. The local heat transfer coefficient of the fin surface for four type DWVGs was measured by the naphthalene sublimation technique. As the results, the distribution of the heat transfer coefficient at rear of DWVGs showed longitudinal contours for common flow down DWVGs and wavy contours for common flow up DWVGs. The distribution showed many cell type contours at near wall and downstream for all DWVGs. Compared to case without DWVGs in present experimental tests, all DWVGs showed the best enhancement of heat transfer at Re=2000. Of 4 cases of DWVGs, D type showed the best enhancement of heat transfer
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)
P. Raveendiran
2015-06-01
Full Text Available The heat transfer coefficients and friction factors of a baffled shell and heat pipe heat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heat pipe heat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of both hot and cold side of heat exchanger and mass flow rate of fluids were measured using an appropriate instrument. Different tests were performed from which condenser side heat transfer coefficient and friction factor were calculated. In all operating conditions it has been found that the heat transfer coefficient increases by increasing the mass flow rate and angle of inclination. The reduction in friction factor occurs when the Reynolds number is increased. The overall optimum experimental effectiveness of GABSHPHE has found to be 42% in all operating conditioning at ? = 45o.
Jiang, Han; Browning, Robert; Fincher, Jason; Gasbarro, Anthony; Jones, Scooter; Sue, Hung-Jue
2008-05-01
To study the effects of surface roughness and contact load on the friction behavior and scratch resistance of polymers, a set of model thermoplastic olefins (TPO) systems with various surface roughness ( Ra) levels were prepared and evaluated. It is found that a higher Ra corresponds to a lower surface friction coefficient ( ?s). At each level of Ra, ?s gets larger as contact load increases, with a greater increase in ?s as Ra level increases. It is also observed that with increasing contact load and increasing Ra, the ?s tend to level off. In evaluating TPO scratch resistance, a lower ?s would delay the onset of ductile drawing-induced fish-scale surface deformation feature, thereby raising the load required to cause scratch visibility. However, as the contact load is further increased, the ?s evolves to become scratch coefficient of friction (SCOF) as significant sub-surface deformation and tip penetration occur and material displacement begins, i.e., ploughing. No dependence of Ra and ?s on the critical load for the onset of ploughing is observed. In this work, the distinction between ?s and SCOF will be illustrated. Approaches for improving scratch resistance of polymers via control of Ra are also discussed.
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
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
Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu
Energy Technology Data Exchange (ETDEWEB)
Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)
2014-02-28
A 5?nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup ?8}]exp[?(0.31±0.02(eV)/(at) )/kT]?cm{sup 2}/s.
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
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.
Theory of the kinetic coefficients of the atomically rough surface of 4He crystals
International Nuclear Information System (INIS)
The growth coefficient K (the velocity of growth per unit chemical potential difference) and the Onsager cross-coefficients b1 and b2, coupling growth and heat flow, are calculated for atomically rough surfaces of hcp 4He crystals. The calculation is based on the premise, suggested by Andreev and Parshin, that growth is limited by the collision of phonons and rotons with the interface. The calculated K is compared with that obtained by Keshiskev et al. from the damping of melting-freezing waves. The theory assumes that the excitations are in the ballistic regime where their mean free path is large compared to the wavelength of the melting-freezing waves. In the experiment only the phonons satisfy this condition, yet the theory agrees with the data even when roton scattering is important. Irreversible thermodynamics requires that the cross coefficients b1 and b2 be equal. This is shown by direct calculation. The value of b1 and b2 depends on the ratio of two integrals over the phonon transmission coefficient and it is evaluated for two models of the transmission. The theory agrees fairly well with a recent measurement of b1. A calculation of the dissipation in the hydrodynamic regime, where the free path is short, shows that the damping of melting-freezing waves should have a different dependence on frequency compared to the ballistic regime
Study on two-phase heat transfer coefficients in helical coil steam generator of 200MW HTGR
International Nuclear Information System (INIS)
Steam-water two-phase boiling heat transfer characteristics of helical-coil-type steam generators within the operating conditions of 200MW HTGR were studied in detail. Experiments of heat transfer in a vertical helically-coiled tube were carried out in high-pressure water test loop of Xi'an Jiaotong University. The coil was constructed from 1Cr18Ni9Ti stainless steel tube with 3800mm length, 20mm OD and 16mm ID Its helix diameter is 1300mm, and helix angle is 3.65deg. The experimental conditions covered in tests are: pressure p=4-19 MPa, mass velocity G=400-1400 kg/(m2·s), inner wall heat flux q=100-750 kW/m2. Wall temperature profiles along the tube axis and around the tube perimeter were recorded. On the bases of these data, the boiling heat transfer and post-CHF heat transfer were studied. A set of general correlations for predicting the heat transfer coefficients was derived. The correlations are in good agreement with the experimental data. So they can be used in the design of steam generator and other helical-coil-type heat transfer device. (author)
Study of energy transfer in helium atom scattering from surfaces
Siber, A; Toennies, J P
1999-01-01
Recently developed quantum mechanical theory of inelastic He atom scattering (HAS) from solid surfaces is employed to analyze the energy transfer between projectile particles (thermal energy He-atoms) and vibrational degrees of freedom (phonons) characteristic of a variety of experimentally studied surfaces. We have first calculated the angular resolved energy transfer which can be directly compared with the values deducible from the HAS time-of-flight spectra and a good agreement with experimental data has been found. This enabled us to calculate the total or angular integrated energy transfer, which is of paramount importance in the studies of gas-surface scattering, but is neither accessible in HAS (which yields only the angular resolved quantities), nor in the wind tunnel measurements for surfaces whose atomic composition and cleanliness must be maintained during the experiment. Here we present the results for prototype collision systems of this kind, viz. He => Cu(001), He => Xe/Cu(111) and He => Xe(111)...
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...
Molecular Boundary Conditions and Accommodation Coefficient on A Nonequilibrium Liquid Surface
Tsuruta, Takaharu; Tokunaga, Atsushi; Nagayama, Gyoko
2011-05-01
The non-equilibrium molecular dynamics (NEMD) simulations have been carried out to obtain new evidence about inverted temperature profiles. We find that the inverted temperature profile occurs due to the excess energy of the reflecting molecules without contradiction to the second law. Therefore, a new definition of the accommodation coefficient for the reflecting molecule is proposed based on the energy of the reflecting molecule under the equilibrium condition. The accommodation coefficient decreases with increasing the mass flux in the vicinity of the liquid surface and this is the reason for the inverted temperature profile. Also, a direct simulation of Monte Carlo (DSMC) method has been performed with applying the molecular boundary condition developed in the non-equilibrium molecular dynamics simulation. An inverted temperature profile is obtained because the energy of the reflecting molecule cannot reach accommodations to that of the equilibrium ones.
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
Subcooled flow boiling heat transfer from microporous surfaces in a small channel
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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)
Amirkhanov, I V; Pavlus, M; Puzynina, T P; Puzynin, I V; Sarhadov, I
2005-01-01
On the basis of the solution of a nonlinear diffusion equation with initial and boundary conditions, a transport coefficient of moisture in a sample of a porous material is found by minimization of a functional, which expresses diversion of the computed profile of moisture concentration in well-defined time moments from their experimental values for the defined moisture transport coefficient. In this case the transport coefficient as opposed to the previous works is found as a sum of the degree and exponential functions of the moisture concentration. The exponent of the power function depends on time. Thus, a more accurate coincidence of the computed profiles of the moisture concentration with their experimental profiles is gained in comparison to previous works performed by other authors. The exponential term provides a good coincidence of the mentioned profiles for big times nearby the boundary of the sample, where evaporation of the moisture to the atmosphere takes place.
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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.)
Heat transfer characteristics of a back-corrugated absorber surface for solar air collectors
Shockey, K. A.; Pearson, J. T.; Dewitt, D. P.
1981-11-01
The present study experimentally examines a back-corrugated absorber-convector comprised of a rectangularly corrugated plate attached to the back side of a flat absorber plate with a high temperature, high strength adhesive. The upper surface is subjected to a heat flux from a blanket-type electric heater simulating solar irradiation. The corrugated plate configuration creates two parallel airflow channel types. The two channels have different geometries and, therefore, may have different heat transfer characteristics. An apparatus was designed to determine the local convective heat transfer coefficients along each of the channels. The results show that the back-corrugated absorber-convector has much better thermal performance than the simple flat-plate absorber-convector, mainly because of the increased connective heat transfer area.
International Nuclear Information System (INIS)
The pathway of farm product intake are very important for evaluating the human health risks caused by the long term global radioactive contamination. The main parameters contained in this pathway : the distribution coefficient(kd), the transfer coefficient by direct foliar absorption(K) and the transfer coefficient by root uptake(TF), were determined using the Sr-90 and Cs-137 environmental monitoring data in Japan. The major finding obtained in this study are as follows : (1) kd can be determined by the monitoring data of radionuclide concentration in soil, K by the concentration in farm products during larger fallout period, 1960's, and TF by the concentration in farm products during smaller fallout period, after 1970's. (2) The ranges of kd were determined as 10-300 for Sr-90 and 10-2,000(ml/g) for Cs-137. These ranges are smaller than the reported ranges, thus the accuracy for estimating kd were improved in this study. K are 0.03-1 for Sr-90 and 0.4-1(cm2·month/g) for Cs-137 ; TF are 0.001-0.06 for Sr-90 and 0.0005-0.001(-) for Cs-137. (author)
Jebaraj Johnley Muthuraj, Josiah
Cathodic protection is widely used for corrosion prevention. However, this process generates hydrogen at the protected metal surface, and diffusion of hydrogen through the metal may cause hydrogen embrittlement or hydrogen induced stress corrosion cracking. Thus the choice of a metal for use as fasteners depends upon its hydrogen uptake, permeation, diffusivity and trapping. The diffusivity of hydrogen through four high strength alloys (AISI 4340, alloy 718, alloy 686, and alloy 59) was analyzed by an electrochemical method developed by Devanathan and Stachurski. The effect of plasma nitriding and microstructure on hydrogen permeation through AISI 4340 was studied on six different specimens: as-received (AR) AISI 4340, nitrided samples with and without compound layer, samples quenched and tempered (Q&T) at 320° and 520°C, and nitrided samples Q&T 520°C. Studies on various nitrided specimens demonstrate that both the gamma'-Fe 4N rich compound surface layer and the deeper N diffusion layer that forms during plasma nitriding reduce the effective hydrogen diffusion coefficient, although the gamma'-Fe4N rich compound layer has a larger effect. Multiple permeation transients yield evidence for the presence of only reversible trap sites in as-received, Q&T 320 and 520 AISI 4340 specimens, and the presence of both reversible and irreversible trap sites in nitrided specimens. Moreover, the changes in microstructure during the quenching and tempering process result in a significant decrease in the diffusion coefficient of hydrogen compared to as-received specimens. In addition, density functional theory-based molecular dynamics simulations yield hydrogen diffusion coefficients through gamma'- Fe4N one order of magnitude lower than through ?-Fe, which supports the experimental measurements of hydrogen permeation. The effect of microstructure and trapping was also studied in cold rolled, solutionized, and precipitation hardened Inconel 718 foils. The effective hydrogen diffusion coefficient is considerably higher for the solutionized Inconel 718 than for either the cold rolled or precipitation hardened specimens. Microstructural studies indicate that the reduced hydrogen diffusion coefficients in the latter specimens arise from hydrogen trapping at dislocations and precipitates that are present at much lower concentrations in the solutionized specimens. Repeated permeation transients provide evidence for irreversible hydrogen trapping in the cold rolled and precipitation hardened specimens, but such effects are insignificant in the solutionized specimens. The effect of trapping in determining the hydrogen diffusion coefficients was also studied in alloy 686 and 59 specimens. Microstructural studies indicate the presence of bcc-Mo rich inclusions concentrated along the grain boundaries in alloy 686 specimens, but randomly distributed in alloy 59 specimens. Multiple permeation transients show an increase in diffusion coefficient values for the decay transients compared to rise transients in alloy 686 specimens. On the other hand, the first rise transient had a lower diffusion coefficient compared to successive rise and decay transients in alloy 59 specimens. Effective diffusion coefficient (Deff) values of hydrogen in multiple permeation transients suggest that hydrogen trapping sites are predominantly reversible in alloy 686, but mixed reversible and irreversible in alloy 59.
Calculation on fluorescence resonance energy transfer on surfaces.
Dewey, T G; Hammes, G.G.
1980-01-01
A general method for estimating fluorescence resonance energy transfer between distributions of donors and acceptors on surfaces is presented. Continued fraction approximants are obtained from equivalent power series expansions of the change in quantum yield in terms of the fluorescent lifetimes or the steady-state fluorescence. These approximants provide analytic equations for the analysis of energy transfer and error bounds for the approximants. Specific approximants are derived for five mo...
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.
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.
Heat and mass transfer effect on hydromagnetic flow of a moving permeable vertical surface
International Nuclear Information System (INIS)
Numerical results are presented for the effects of heat and mass transfer on hydromagnetic flow of a moving permeable vertical surface. The surface is maintained at linear temperature and concentration variations. The nonlinear-coupled boundary layer equations were transformed and the resulting ordinary differential equations were solved by perturbation technique. Numerical results for the dimensionless velocity profiles, the temperature profiles, the local friction coefficient and the local Nusselt number are presented for various values of Prandtl number, suction/blowing parameter, Schrnidt number, buoyancy ratio and Hartmann number. The effects of the different parameters on the velocity and temperature profiles as well as skin friction and wall heat transfer are evaluated. Favorable comparisons with previously published work confirm the correctness of numerical results
Characteristics of transient heat transfer on a hot surface during cooling with spray
International Nuclear Information System (INIS)
An experimental study has been done to make clear effect of mass flux and subcooling of spray liquid, gravity and thermal properties of solid material on spray cooling of a cylindrical hot block surface. A cooling history is divided into four time periods determined by behavior of spray droplets on the hot surface. Heat transfer coefficient during wetted period increases about 100 times larger than that for non-wetted period. We tried to correlate a wetting time giving sudden wall temperature drop with two groups of parameters which was determined from conjugate heat transfer with heat conduction of the hot solid. The two parameter groups correlate experimental data fairly well in spite of simple assumptions for the derivation. (author)
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
International Nuclear Information System (INIS)
Nature of physical problem solved: AUTOJOM is a computer program that will generate the coefficients of any quadratic equation used to define conic volumes and also the coefficients of the planes needed to define parallelepipeds, wedges, and pyramids. JOMREAD is a computer code to check any 3D geometry composed of and constructed with quadratic surfaces
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...
Measurement of the 2H(p,n) pp transverse polarization transfer coefficient at 20.4 MeV
International Nuclear Information System (INIS)
The transverse polarization transfer coefficient, K/suby//suby/', has been measured for the reaction 2H(p,n) pp at 18degree for E/subp/=20.4 MeV as a function of neutron energy. Although predictions based on a three-body separable-potential model with S-wave N-N interactions are in reasonable agreement with the data, the need for a three-body theory with more realistic N-N forces is indicated
Jafar Ghani Majeed
2013-01-01
The volumetric mass transfer coefficient (KG.a) for SO2 removal from gas mixture into aqueous Na2SO3 solution was studied in a plate column at constant temperature ( 25 , and liquid holdup. The KG.a values were evaluated over ranges of operating independent variables: gas flow rate (QG), SO2 concentration in inlet gas (CSO2, in), and concentration of aqueous Na2SO3 solution (CNa2SO3). The experimental results showed that KG.a decreased with i...
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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.
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)
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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.
Determination of transfer coefficients soil/vegetation by means of site-specific soil parameters
International Nuclear Information System (INIS)
The transfer of Sr and Cs to different forms of vegetation is influenced by a great number of soil properties, some parameters playing a key part for certain nuclides. The dominant factor for the uptake of Sr is the exchangeable Ca content of the soil. The transfer of Cs to different plants on the other hand is affected by several properties of the soil in about equal strength, for different types of plant and soil one or the other parameter having got greater influence. (orig.) 891 HP/orig. 892 MB
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
Sieres, Jaime; Fernández-Seara, José
2008-08-01
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.
Rate coefficients for collisional population transfer between 3p54p argon levels at 300 0K
International Nuclear Information System (INIS)
The population transfer between excited 3p54p argon levels induced by the collisional process Ar* (3p54p)/sub i/ + Ar(1S0) arrow-right-left Ar* (3p54p)/sub j/ + Ar(1S0) + ?E was studied in the afterglow of an argon pulsed discharge, at the pressure range of 0.2--1 Torr. Selective population of one particular argon 3p54p level was achieved by laser excitation from one metastable state by use of a tunable cw dye laser. The populations of the laser-excited level and of the collisional excited levels were determined by intensity measurements of the fluorescence line and of the sensitized fluorescence lines. The time-dependence study of the populations of the metastable state, of the laser-excited state, and of the collisional excited states was carried out to ascertain the product channel and to determine the collisional transfer rate coefficients
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
International Nuclear Information System (INIS)
Volume-transfer coefficients of uranyl nitrate and nitric acid are determined during extraction by tri-n-butyl phosphate diluted with a mixture of saturated hydrocarbons in centrifugal extractor. The interface area is determined experimentally by two independent methods: using solidification of dispersed phase or its sedimentation. Both methods give close results. Uranium and nitric acid mass-transfer coefficients are calculated with regard to the interface area
Marquardt, Katharina; Dohmen, Ralf; Wagner, Johannes
2014-05-01
Diffusion along interface and grain boundaries provides an efficient pathway and may control chemical transport in rocks as well as their mechanical strength. Besides the significant relevance of these diffusion processes for various geologic processes, experimental data are still very limited (e.g., Dohmen & Milke, 2010). Most of these data were measured using polycrystalline materials and the formalism of LeClaire (1951) to fit integrated concentration depth profiles. To correctly apply this formalism, certain boundary conditions of the diffusion problem need to be fulfilled, e.g., surface diffusion is ignored, and furthermore the lattice diffusion coefficient has to be known from other studies or is an additional fitting parameter, which produces some ambiguity in the derived grain boundary diffusion coefficients. We developed an experimental setup where we can measure the lattice and grain boundary diffusion coefficients simultaneously but independent and demonstrate the relevance of surface diffusion for typical grain boundary diffusion experiments. We performed Mg2SiO4 bicrystal diffusion experiments, where a single grain boundary is covered by a thin-film of pure Ni2SiO4 acting as diffusant source, produced by pulsed laser deposition. The investigated grain boundary is a 60° (011)/[100]. This specific grain boundary configuration was modeled using molecular dynamics for comparison with the experimental observations in the transmission electron microscope (TEM). Both, experiment and model are in good agreement regarding the misorientation, whereas there are still some disagreements regarding the strain fields along the grain boundary that are of outmost importance for the strengths of the material. The subsequent diffusion experiments were carried out in the temperature range between 800° and 1450° C. The inter diffusion profiles were measured using the TEMs energy dispersive x-ray spectrometer standardized using the Cliff-Lorimer equation and EMPA measurements. To evaluate the obtained diffusion profiles we adapted the isolated grain boundary model, first proposed by Fisher (1951) to match several observations: (i) Anisotropic diffusion in forsterite, (ii) fast diffusion along the grain boundary, (iii) fast diffusion on the surface of the sample. The latter process is needed to explain an additional flux of material from the surface into the grain boundary. Surface and grain boundary diffusion coefficients are on the order of 10000 times faster than diffusion in the lattice. Another observation was that in some regions the diffusion profiles in the lattice were greatly extended. TEM observations suggest here that surface defects (nano-cracks, ect.) have been present, which apparently enhanced the diffusion through the bulk lattice. Dohmen, R., & Milke, R. (2010). Diffusion in Polycrystalline Materials: Grain Boundaries, Mathematical Models, and Experimental Data. Reviews in Mineralogy and Geochemistry, 72(1), 921-970. Fisher, J. C. (1951). Calculations of Diffusion Penetration Curves for Surface and Grain Boundary Diffusion. Journal of Applied Physics, 22(1), 74-77. Le Claire, A. D. (1951). Grain boundary diffusion in metals. Philosophical Magazine A, 42(328), 468-474.
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 %.
Experimental &Theoretical Analysis Of Heat Transfer Augmentation From Dimpled Surface
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Dhananjay R.Giram
2013-09-01
Full Text Available In the present work the heat transfer characteristics and the pressure drop of the forced convection apparatus of six dimpled plates is studied. Six test plates with varying dimple densities; by varying the input voltage Nusselt No. variation was recorded. It is found that Nusselt No. increases as the dimple density increases .Also it was found that percentage increase in Nusselt No. is greater for staggered dimple arrangement. The sample experimental results obtained are presented in graphical forms as shown in Figure shows the calculated results based on the observations to show the comparative Nusselt numbers enhancements with that obtained with different parameters combinations. Dimpled typical technique that offers a higher heat transfer increase at the cost of mild pressure drop penalty. This study investigates the heat transfer characteristics of Plate with dimpled surface. 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.
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.
Mitigated subsurface transfer line leak resulting in a surface pool
International Nuclear Information System (INIS)
This analysis evaluates the mitigated consequences of a potential waste transfer spill from an underground pipeline. The spill forms a surface pool. One waste composite, a 67% liquid, 33% solid, from a single shell tank is evaluated. Even drain back from a very long pipeline (50,000 ft), does not pose dose consequences to the onsite or offsite individual above guideline values
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.
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.
Application of FLECHT reflood heat transfer coefficients to C-E's 16 x 16 fuel bundles
International Nuclear Information System (INIS)
NRC has approved a FLECHT based reflood heat transfer correlation (designated MOD-1C) for use on the C-E 14 x 14 fuel assembly. This report proposes a procedure for applying the MOD-1C correlation to the C-E 16 x 16 fuel assembly. The procedure applies a non-constant correction factor to the MOD-1C correlation. This correction factor accounts for the geometric differences between the 14 x 14 and 16 x 16 fuel assemblies. Comparison with experimental data corroborates the applicability of the correction method. A computer program called THERM which presents a physical model of the reflood heat transfer process is described. This program was employed to establish the significant parameters involved in the geometric correction factor. Thus, the acceptability of the correction factor is based on the comparisons with experimental data rather than on the THERM program
Evaluation of Heat and Mass Transfer Coefficients for R134a/DMF Bubble Absorber
Suresh, M; 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...
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...
Energy Technology Data Exchange (ETDEWEB)
Hosseini, R.; Hosseini-Ghaffar, A. [Faculty of Mechanical Engineering Amirkabir University of Technology, 424 Hafez Avenue, P.O. Box 15875-4413, Tehran (Iran); Soltani, M. [Mechanical Systems Department, Niroo research Institute (NRI), End of Pounak Bakhtari Blvd., P.O. Box 14665-517, Shahrak Gharb, Tehran (Iran)
2007-04-15
In this paper, the heat transfer coefficient and pressure drop on the shell side of a shell-and-tube heat exchanger have been experimentally obtained for three different types of copper tubes (smooth, corrugated and with micro-fins). Also, experimental data has been compared with theoretical data available. Correlations have been suggested for both pressure drop and Nusselt number for the three tube types. A shell-and-tube heat exchanger of an oil cooler used in a power transformer has been modeled and built for this experimental work in order to investigate the effect of surface configuration on the shell side heat transfer as well as the pressure drop of the three types of tube bundles. The bundles with the same geometry, configuration, number of baffles and length, but with different external tube surfaces inside the same shell were used for the experiment. Corrugated and micro-fin tubes have shown degradation of performance at a Reynolds number below a certain value (Re<400). At a higher Reynolds number the performance of the heat exchanger greatly improved for micro-finned tubes. (author)
International Nuclear Information System (INIS)
The pipe thinning phenomenon which is due to flow accelerated corrosion (FAC) is one of the major causes of unexpected troubles at current nuclear power plants. In order to prevent these troubles in the future, it is highly important to understand and analyze FAC mechanism. So, we calculated three dimensional flow to evaluate a turbulence energy and a mass transfer coefficient at pipe surface which is one of the key parameters of corrosion model. (author)
Ellwood, R; Stratoudaki, T; Sharples, S D; Clark, M; Somekh, M G
2015-11-01
Much interest has arisen in nonlinear acoustic techniques because of their reported sensitivity to variations in residual stress, fatigue life, and creep damage when compared to traditional linear ultrasonic techniques. However, there is also evidence that the nonlinear acoustic properties are also sensitive to material microstructure. As many industrially relevant materials have a polycrystalline structure, this could potentially complicate the monitoring of material processes when using nonlinear acoustics. Variations in the nonlinear acoustoelastic coefficient on the same length scale as the microstructure of a polycrystalline sample of aluminum are investigated in this paper. This is achieved by the development of a measurement protocol that allows imaging of the acoustoelastic response of a material across a samples surface at the same time as imaging the microstructure. The development, validation, and limitations of this technique are discussed. The nonlinear acoustic response is found to vary spatially by a large factor (>20) between different grains. A relationship is observed when the spatial variation of the acoustoelastic coefficient is compared to the variation in material microstructure. PMID:26627757
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 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.)
Determining the moderator temperature coefficient by fitting the noise analysis transfer function
International Nuclear Information System (INIS)
Previous researchers have established that the value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. Both the root-mean-square method and the frequency response function (FRF) technique are used to determine the absolute magnitude of the MTC. Normally, these methods are used in conjunction with the phase angle technique, which is used to ascertain the MTC sign; however, a recent study has determined that a boundary exists on the range of MTC values for which the phase angle from noise analysis can be used. This paper describes a fitting method to determine both the MTC sign and magnitude in a single analysis in order to overcome such limitations
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.
Study on electron transfer mechanism in surface enhanced Raman scattering
International Nuclear Information System (INIS)
The Raman intensity from the pyridine on the silver electrode is measured as the function of electrode potential. The charge transfer mechanism can be confirmed by measuring the potential dependence of peak value of Raman intensity as varying the incident photon energy. In order to find the potential dependence of resonent Raman Scattering intensity through the charge transfer process, the Herzberg-Teller terms of polarization tensor is in the theoritical study and this is compared with experimental value. During the potential range of constant surface complex concentration, the experimental result of Raman intensity profile is coincide quite well with theoritical calculation.(Author)
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.
Taslim, M. E.; Spring, S. D.
1991-06-01
An experimental investigation is conducted using liquid crystals to study the effects of turbulator profile and spacing on heat transfer coefficient. Friction factors are also measured and both friction factor and heat transfer results for fifteen turbulator geometries are compared. All test configurations position the turbulators on two opposite walls of a rectangular test section in a staggered arrangement with an angle of attack to the mainstream flow of 90 degrees. It is concluded that while turbulators with aspect ratios greater than unity produce higher heat transfer coefficients at the expense of higher pressure losses, 'jersey-barrier' shaped turbulators, properly spaced, are very effective in heat removal with moderate pressure losses.
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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
Stability analysis of MHD viscous flow and heat transfer over a permeable shrinking surface
Hafidzuddin, Mohd Ezad Hafidz; Nazar, Roslinda
2015-10-01
In this study, a problem of steady laminar magnetohydrodynamic (MHD) viscous boundary layer flow and heat transfer over a permeable shrinking surface is considered. The governing nonlinear partial differential equations are transformed into a system of nonlinear ordinary differential equations using a similarity transformation. The transformed ordinary differential equations are then solved numerically using the bvp4c function in MATLAB software. Dual solutions are found for a certain range of the suction parameter. A stability analysis has been performed to determine which solution is stable and physically realizable. The effects of the suction parameter, the Hartmann number and the Prandtl number on the skin friction and heat transfer coefficients as well as the velocity and temperature profiles are presented and discussed in detail.
Directory of Open Access Journals (Sweden)
anjali devi
2015-01-01
Full Text Available The effects of nonlinear radiation on hydromagnetic boundary layer flow and heat transfer over a shrinking surface is investigated in the present work. Using suitable similarity transformations, the governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations. The resultant equations which are highly nonlinear are solved numerically using Nachtsheim Swigert shooting iteration scheme together with Fourth Order Runge Kutta method. Numerical solutions for velocity, skin friction coefficient and temperature are obtained for various values of physical parameters involved in the study namely Suction parameter, Magnetic parameter, Prandtl number, Radiation parameter and Temperature ratio parameter. Numerical values for dimensionless rate of heat transfer are also obtained for various physical parameters and are shown through tables. The analytical solution of the energy equation when the radiation term is taken in linear form is obtained using Confluent hypergeometric function.
Ibrahim, Mounir; Kannapareddy, Mohan; Tew, Roy C.; Dudenhoefer, James E.
1991-01-01
Twelve different cases of multidimensional models of Stirling engine components for space applications have been numerically investigated for oscillating, incompressible laminar flow with heat transfer. The cases studied covered wide ranges of Valensi number (from 44 to 700), Re(max) number (from 8250 to 60,000), and relative amplitude of fluid motion of 0.686 and 1.32. The Nusselt numbers obtained from the present study indicate a very complex shape with respect to time and axial location in the channel. The results indicate that three parameters can be used to define the local Nusselt number variation, namely: time average, amplitude, and phase angle. These parameters could be correlated respectively using: Re(max), Va and Re(max), and the relative amplitude of fluid motion.
Surface roughness effects on heat transfer in Couette flow
International Nuclear Information System (INIS)
A cell theory for viscous flow with rough surfaces is applied to two basic illustrative heat transfer problems which occur in Couette flow. Couette flow between one adiabatic surface and one isothermal surface exhibits roughness effects on the adiabatic wall temperature. Two types of rough cell adiabatic surfaces are studied: (1) perfectly insulating (the temperature gradient vanishes at the boundary of each cell); (2) average insulating (each cell may gain or lose heat but the total heat flow at the wall is zero). The results for the roughness on a surface in motion are postulated to occur because of fluid entrainment in the asperities on the moving surface. The symmetry of the roughness effects on thermal-viscous dissipation is discussed in detail. Explicit effects of the roughness on each surface, including combinations of roughness values, are presented to enable the case where the two surfaces may be from different materials to be studied. The fluid bulk temperature rise is also calculated for Couette flow with two ideal adiabatic surfaces. The effect of roughness on thermal-viscous dissipation concurs with the viscous hydrodynamic effect. The results are illustrated by an application to lubrication. (Auth.)
Experimental determinations of the performances of heat transfer surfaces
International Nuclear Information System (INIS)
With the help of flow schemes and of assumptions on the heat transfer, it is possible, in some cases, to predict the thermal and aerodynamical performances of a new heat transfer surface with moderate accuracy. These estimates, valid for an approximate classification of a new surface among known surfaces, are not accurate enough to be taken as a basis for the design of heat exchangers. In the present state of knowledge, the performances of a new heat transfer surface can only be determined accurately with experimental measurements. Bertin and Co have at their disposal two air test rigs especially designed for this purpose. The first one, more directly concerned with the measurements on tube bundles with fluid flow perpendicular to the generatrices of the tubes, is a semi-closed loop equipped with a high-efficiency ejector which amplifies the air flow rate supplied by an external source and thus allows high values of Reynolds number to be reached. The second one is adapted to other types of surfaces: tubes with external flow parallel to the generatrices, tubes with sophisticated cross section and with internal flow, compact surfaces with finned plates, etc. Both test rigs, the relevant equipment, the methods of data acquisition and of test results analysis are described in this paper. During the 5 past years, 60 configurations were tested. It was possible to compare some of the test results with the results of measurements performed later, on entire heat exchangers working with numbers of tubes, fluids, and temperature levels different from those prevailing during the tests on the small scale mock-up; the agreement is quite good
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
Guerry, J.; Hot, J. P.; Durou, C.
1980-05-01
The rate of convective heat transfer at the surface of a solar collector is measured by means of a real-time holographic interferometry system as part of a study of the suitability of cold solar collectors. Holograms were recorded in rapid sequence on photographic plates and continuously on magnetic by the use of a video system for both surfaces of a flat rectangular collector which was heated and cooled to temperatures 20 C above and 10 C below ambient and tilted at various angles of inclination. A zone of laminar flow with a heat transfer coefficient decreasing from 5 to 3.5 W/K per min with distance from the edge of the vertical plate is found, followed by a transition into a turbulent regime in which the heat transfer coefficients remain nearly constant at 3 W/K per min. As the plate is tilted, the heat transfer coefficient on the upper face is observed to exceed that of the lower face, accompanied by greater turbulence on the upper face. Results thus indicate that a 1-sq m collector inclined at 45 deg and maintained at 2 C in a still 12-C atmosphere will collect 70 W of ambient energy by free convection, in addition to the 200 W recoverable from diffuse solar radiation.
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.
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.
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
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.
Effect of Blade Tip Geometry on Heat Transfer Characteristics on Blade Surface and Shroud
International Nuclear Information System (INIS)
The effect of blade tip geometry has been investigated on blade near-tip surface and shroud heat transfer. The local mass transfer coefficients were measured on the blade surface and shroud using a naphthalene sublimation technique. A low speed stationary annular cascade with a single turbine stage was used. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is 2.5% of the blade chord. To investigate the effect of tip geometry, the blade with squealer rim was used and the results were compared with the flat tip cases. The average cavity depth to chord ratio (H/C) is 2.2% and the rim width is 5 mm (w/C=3.3%). The inlet flow Reynolds number based on chord length and incoming flow velocity is fixed to 1.5 x 105. The results show that the squealer rim reduces the amount of tip leakage flow, which results in the increased effect on the blade surface. The reason is that the momentum of tip leakage flow is reduced and then the tip leakage vortex is closer to the surface than the flat tip case. On shroud, the average value is almost the same as that for the flat-tip blade although the local distribution is quite different
Charbonneau, Francois
La surveillance maritime est un domaine d'applications ou l'interet politique et scientifique croit constamment au Canada. Un des outils privilegies pour la surveillance maritime est l'acquisition de donnees radars, par des systemes aeroportes ou spatio-portes (ERS-2, RADARSAT et Envisat). Par leur grande couverture spatiale, ainsi que leur sensibilite a la geometrie de surface, les donnees radars permettent, en autres, la detection de cibles ponctuelles (bateaux), estimation des vents, detection des glaces de mer, ainsi que la detection de deversement d'hydrocarbure. Les limites et les avantages de la detection d'hydrocarbure par acquisitions de donnees radars sont bien connus, mais il reste encore des lacunes au niveau de l'extraction des parametres physiques d'une surface d'hydrocarbure. Ce projet a pour objectif de caracteriser le coefficient de retrodiffusion radar associe a une surface d'hydrocarbure en milieu oceanique, par l'introduction d'un modele thermodynamique d'attenuation de la surface, au modele theorique radar IEM. Le modele global permet de simuler le comportement de sigma° en fonction des proprietes visco-elastiques, ainsi que de l'epaisseur de la couche d'hydrocarbure et en fonction des parametres d'acquisition radar. Le modele developpe fut valide a partir des donnees SIR-C acquises lors d'experimentations controlees. A partir des informations environnementales et du type d'hydrocarbure, notre modele a permis d'estime le contraste d'intensite avec une precision de 1 a 1,5 dB, a la bande C. Alors qu'a la bande L, l'erreur sur le contraste est d'environ 1,5 a 2 dB sur l'ensemble des mesures. Ce qui est excellant considerant l'heterogeneite des surfaces analysees. Egalement, nous effectuons des analyses multi-polarisees et polarimetriques avec les donnees SIR-C acquises au-dessus de sites experimentaux. II en ressort que le ratio de polarisation VV/HH, ainsi que le facteur d'anisotropie sont des pistes de recherche prometteuses qu'il faudra explorer dans le futur. Cependant, la qualite des analyses sera limitee par le niveau du seuil du bruit technique de l'antenne RSO.
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)
International Nuclear Information System (INIS)
In real design of the high and interim pressure turbine casing, it is one of the important things to figure out its thermal strain exactly. In this paper, with the establishment of the new concept for the heat transfer coefficient of steam that is one of the factors in analysis of the thermal stress for turbine casing, an analysis was done for one of the high and interim pressure turbine casings in operating domestically. The sensitivity analysis of the heat transfer coefficient of steam to the thermal strain of the turbine casing was done with a 2-D simple model. The analysis was also done with switching of the material properties of the turbine casing and resulted in that the thermal strain of the turbine casing was not so sensitive to the heat transfer coefficient of steam. On the basis of this, 3-D analysis of the thermal strain for the high and interim pressure turbine casing was done
Marbach, J.; Bronold, F. X.; Fehske, H.
2012-04-01
We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable N2(3?+ u ) molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance N2 -(2? g ) 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 Al2O3, MgO, SiO2, and diamond at several kinetic energies of the projectile. With the exception of MgO the coefficients turn out to be of the order of 10-1 over the whole range of kinetic energies. This rather large value is a direct consequence of the shape resonance acting as a relay state for electron emission.
Energy Technology Data Exchange (ETDEWEB)
Dimitriadis, Alexandros I., E-mail: aldimitr@ee.auth.gr [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kantartzis, Nikolaos V., E-mail: kant@auth.gr [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Tsiboukis, Theodoros D., E-mail: tsibukis@auth.gr [Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Hafner, Christian, E-mail: hafner@ethz.ch [Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, 8092 Zurich (Switzerland)
2015-01-15
Highlights: •Formulas for E/M fields radiated by continuous surface polarization distributions. •Non-local effective surface susceptibility model for periodic metafilms. •Generalized reflection and transmission coefficients for an arbitrary metafilm. •Successful treatment of non-planar scatterer arrays and spatial dispersion effects. -- Abstract: A non-local surface susceptibility model for the consistent description of periodic metafilms formed by arbitrarily-shaped, electrically-small, bianisotropic scatterers is developed in this paper. The rigorous scheme is based on the point-dipole approximation technique and is valid for any polarization and propagation direction of an electromagnetic wave impinging upon the metafilm, unlike existing approaches whose applicability is practically confined to very specific cases of incidence. Next, the universal form of the resulting surface susceptibility matrix is employed for the derivation of the generalized Fresnel coefficients for such surfaces, which enable the comprehensive interpretation of several significant, yet relatively unexamined, physical interactions. Essentially, these coefficients include eight distinct terms, corresponding to the co-polarized and cross-polarized reflection and transmission coefficients for the two orthogonal eigenpolarizations of a linearly-polarized incident plane wave. The above formulas are, then, utilized for the prediction of the scattering properties of metafilms with different planar and non-planar resonators, which are characterized via the featured model and two previously reported local ones. Their comparison with numerical simulation outcomes substantiates the merits of the proposed method, reveals important aspects of the underlying physics, and highlights the differences between the various modeling procedures.
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...
DEFF Research Database (Denmark)
Hansen, Ernst; Mollerup, Jørgen
1999-01-01
The paper describes a method of simultaneous determination of the external and the solid phase mass-transfer coefficients from frontal analysis data. The protein flux to the solid particles is determined from the slope of the breakthrough curve and the mass-transfer coefficients are determined by fitting the two film model to the experimentally determined flux. The two film model is compared with two apparent over-all driving force models: The apparent over-all mobile phase driving force model a...
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.
Dudley, Peter N; Bonazza, Riccardo; Porter, Warren P
2013-07-01
Animal momentum and heat transfer analysis has historically used direct animal measurements or approximations to calculate drag and heat transfer coefficients. Research can now use modern 3D rendering and computational fluid dynamics software to simulate animal-fluid interactions. Key questions are the level of agreement between simulations and experiments and how superior they are to classical approximations. In this paper we compared experimental and simulated heat transfer and drag calculations on a scale model solid aluminum African elephant casting. We found good agreement between experimental and simulated data and large differences from classical approximations. We used the simulation results to calculate coefficients for heat transfer and drag of the elephant geometry. PMID:23613217
DEFF Research Database (Denmark)
Sing, M.; Schwingenschlögl, U.; Claessen, R.; Dressel, M.; Jacobsen, Claus Schelde
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. Espec...
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.
Yasin, Muhammad; Park, Shinyoung; Jeong, Yeseul; Lee, Eun Yeol; Lee, Jinwon; Chang, In Seop
2014-10-01
This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A(S)/V(L)) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k(L)a) values. We found a k(L)a of 135.72 h(-1) when P was 93.76 kPa and AS/VL was fixed at 27.5m(-1). A higher k(L)a of 155.16 h(-1) was achieved by increasing AS/VL to 62.5m(-1) at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO2 fermentation using Eubacterium limosum KIST612. PMID:25105269
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.
da Silva, Wilton Pereira; E Silva, Cleide M D P S
2014-09-01
Cooling of fruits and vegetables, immediately after the harvest, has been a widely used method for maximizing post-harvest life. In this paper, an optimization algorithm and a numerical solution are used to determine simultaneously the convective heat transfer coefficient, hH, and the thermal diffusivity, ?, for an individual solid with cylindrical shape, using experimental data obtained during its cooling. To this end, the one-dimensional diffusion equation in cylindrical coordinates is discretized and numerically solved through the finite volume method, with a fully implicit formulation. This solution is coupled to an optimizer based on the inverse method, in which the chi-square referring to the fit of the numerical simulation to the experimental data is used as objective function. The optimizer coupled to the numerical solution was applied to experimental data relative to the cooling of a cucumber. The obtained results for ? and hH were coherent with the values available in the literature. With the results obtained in the optimization process, the cooling kinetics of cucumbers was described in details. PMID:25190830
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.
The Henry’s law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for aqueous formaldehyde solutions were determined in the concentration range f...
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
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
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
Correlation properties of surface and percolation transfer of electrons
International Nuclear Information System (INIS)
In this work was received equation, connecting correlatively properties of surface with electrons distribution function. Usually for equilibrium is necessary a large number of collisions. Collisions are 'destroying' correlations. In case rare collisions large importance have correlations and 'memory' effects. Non-Markov's character of emitting particles by surface lead to strongly nonequilibrium condition of 'gas'. Here kinetic equation of diffusive form does not apply. Classical kinetic equation are described only conditions near to equilibrium. This work offers to use ideas anomal diffusion in phase-space. The correlation properties of surface describe by correlations of velocities of emitting electrons: B(t). We offer to use functional equation for probability collision instead of kinetic equation: ?0?0WnoncollF(?) dv = 1 - B(t). This functional allow to consider 'memory' effects. It is important for consideration of electrons and clusters near surfaces. Distribution function become direct connected with correlations. In classical Kubo-Mory theory of transfer is necessary to get nondivergences integral: D ? ?0?B(t). In considering case we can use even 'power function'. It was used 'slow' correlation function as Kohlraush in calculations. The information about kinetics and correlations properties are containing in one functional equation. It was received solution of this equation in form Levy function: F(?) ? 1/?? exp(-1/?). The solution of this form can not be get with help asymptotic methods of kinetic theory. Asymptotics of solution have scale-invariant character F(V) ? 1/V?. This indicate on fractal properties phase-space. (author)
Heat transfer coeffcient for boiling carbon dioxide
DEFF Research Database (Denmark)
Knudsen, Hans Jørgen Høgaard; Jensen, Per Henrik
1997-01-01
Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater wich evaporates the R22. With the heat flux assumed constant over the whole surface and with measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coeffici...
International Nuclear Information System (INIS)
A method of time historical response analysis for large-scale structures is presented. This method is derived from a combination of the transfer influence coefficient method and the Newmark-? or Wilson-? method, and it improves the computational efficiency and accuracy of the transient response analysis remarkably by means of several advantages of the transfer influence coefficient method. The present method is free of the numerical instabilities which often occur in using the Newmark-? or Wilson-? method combined with the transfer matrix method or the Runge-Kutta-Gill method. An algorithm for the transient response is formulated for the three-dimensional tree structure which is mainly found in pipeline systems. We regard the tree structure as a lumped mass system here. The validity of the present method compared with other methods for transient analysis is demonstrated through various numerical computations. (author)
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.
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.
Increased concentration of salts on heat transfer surfaces
International Nuclear Information System (INIS)
The increased concentration of NaCl in the deposits on heat transfer surfaces at leakages from condensers have been studied. The experiments were performed in a high pressure facility simulating a PWR steam generator. Leakages were simulated by continuous feed of synthetic sea water. The increased concentration of NaCl was determined by measuring the gamma-active isotopes Cl-38 and Na-24. A NaI-detector connected to a miltichannel analyzer was used. It was found that a proportion of 0.1 mg/kg chloride in the steamgenerator water gives a proportion of at least 10 mg/kg in the deposit. This is important for the corrosivity of the water in contact with the steam generator tubes
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.
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.
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)
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.
International Nuclear Information System (INIS)
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 (D0), surface coverage (?R), and monolayer thickness (di) were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). DNA surface density (?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: ?DNA (dsS-DNA/Au) > ?DNA (MCH/dsS-DNA/Au) > ?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.
Natural convection heat transfer below downward facing horizontal surfaces
International Nuclear Information System (INIS)
The laminar steady-state natural convection below an infinite strip and below a circular plate, heated at their bottom sides, has been calculated analytically for a uniform surface temperature as well as for a uniform surface heat flux. This convection is driven by the non-uniform temperature distribution near the edges of the plate. This particular feature makes the problem a basically elliptic one, a fact that was not taken into account in earlier studies. In contrast to the flow near inclined heated plates the horizontal situation cannot be described by a boundary layer theory alone. Similarity solutions have been obtained employing the method of matched asymptotic expansions. A potential flow or a Stokes' flow with an unknown upstream velocity is taken as the outer expansion and a boundary layer flow as the inner expansion. Both expansions are matched by an energy balance in the region near the stagnation point at the plate center. In this way the unknown upstream velocity is fixed. This iterative procedure is first restricted to the limiting cases of low and high Prandtl numbers. Then an interpolation of these asymptotes yields heat transfer correlations for arbitrary Prandtl numbers. In comparison to earlier approximations these results are independent of any empirical boundary layer profiles and are based on experimental data to a very limited extend. (orig.)
International Nuclear Information System (INIS)
For the extensive investigation of local heat/mass transfer on the near-tip surface of turbine blade, experiments were conducted in a low speed stationary annular cascade. The turbine test section has a single stage composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has flat tip geometry and the mean tip clearance is about 2.5% of the blade chord. Detailed mass transfer coefficient on the blade near-tip surface was obtained using a naphthalene sublimation technique. The inlet flow Reynolds number based on chord length and incoming flow velocity is changed from 1.0x105 to 2.3x105. Extremely complex heat transfer characteristics are observed on the blade surface due to complicated flow patterns, such as flow acceleration, laminarization, transition, separation bubble and tip leakage flow. Especially, the suction side surface of the blade has higher heat/mass transfer coefficients and more complex distribution than the pressure side surface, which is related to the leakage flow. For all the tested Reynolds numbers, the heat/mass transfer characteristics on the turbine blade are the similar. The overall averaged Shc values are proportional to Rec0.5 on the stagnation region and the laminar flow region such as the pressure side surface. However, since the flow is fully turbulent in the near-tip region, the heat/mass transfer coefficients are proportional to Rec0.8
Experimental assignment of total drag coefficients of bodies embedded in a free surface stream.
Czech Academy of Sciences Publication Activity Database
Chára, Zden?k; Vlasák, Pavel
Praha : Institute of Theoretical and Applied Mechanics AS CR, 2003. s. 126-127. ISBN 80-86246-18-3. [Engineering mechanics 2003 : national conference with international participation. 12.05.2003-15.05.2003, Svratka] R&D Projects: GA ?R GA103/03/0724; GA ?R GA103/00/1620; GA ?R GA103/03/0346 Institutional research plan: CEZ:AV0Z2060917 Keywords : total drag coefficients * free stream flow Subject RIV: BK - Fluid Dynamics
Diffusion coefficients-surface and interfacial tensions - Particular study of some lauryl compounds
International Nuclear Information System (INIS)
Two important results of the double lipophilic and hydrophilic character of some heavy organic compounds with a polar group at the end of the chain, were studied: - In a first part, molecular diffusion coefficients were measured in order to prove the micellar aggregation of tri-laurylammonium nitrate in some organic solutions; - In a second part, the tensioactivity of some lauryl compounds (lauric acid, lauric alcohol, mono-laurylamine, etc.), was studied. (author)
Beibei, Zhou; Quanjiu, Wang; Shuai, Tan
2014-01-01
A theory based on Manning roughness equation, Philip equation and water balance equation was developed which only employed the advance distance in the calculation of the infiltration parameters and irrigation coefficients in both the border irrigation and the surge irrigation. The improved procedure was validated with both the border irrigation and surge irrigation experiments. The main results are shown as follows. Infiltration parameters of the Philip equation could be calculated accurately...
EXPERIMENTAL INVESTIGATIONS OF HEAT TRANSFER ENHANCEMENT FROM DIMPLED SURFACE IN A CHANNEL.
Directory of Open Access Journals (Sweden)
Sandeep S. Kore
2011-08-01
Full Text Available An experimental investigation has been carried out to study heat transfer and friction coefficient by dimpled surface. The aspect ratio of rectangular channel is kept 4:1 and Reynolds number based on hydraulic diameter is varied from 10000 to 40000. The ratios of dimple depth to dimple print diameter is varied from 0.02 to 0.04 toprovide information on the influences of dimple depth. The ratio of channel height to print diameter is 0.5. The heat transfer and friction factor data obtained is compared with the data obtained from smooth plate under similar geometric and flow conditions. It is observed that at all Reynolds number as depth increases from 0.2 to0.3, the normalised Nusselt number and thermal performance increases and then after when depth increase from 0.3 to 0.4 normalised Nusselt number and thermal performance decreases.These are because of increase in strength and intensity of vortices and associated secondary flows ejected from the dimples.
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.
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
Energy Technology Data Exchange (ETDEWEB)
Laurindo, J.B.; Carciofi, B.A.M.; Silva, R.; Hense, H. [Department of Chemical and Food Engineering, Federal University of Santa Catarina, P.O. Box 476, 88040-900 Florianopolis-SC (Brazil)
2010-05-15
A new procedure for on-line monitoring of heat transfer coefficients (h) during immersion cooling is presented. The signature of the resultant force acting on a sphere connected to a load cell by a rigid rod and immersed in a stirred tank was used as an indirect measurement of h. Temperature evolutions over time of the sphere initially at 40 C, immersed in water at 1 C, were used to determine h at different positions in a tank. The standard deviation (sd) of the resultant force was used as a measurement of force oscillations (force signature). The results indicated that it is possible to estimate h between sphere and water from the force signature. For a given spatial positions in the tank, a transfer function with correlation coefficients up to 0.98 was observed when a logarithm function was used to correlate h with sd of the normalized resultant force on the sphere. (author)
James, Philip L.; Sims, Ian R.; Smith, Ian W. M.
1997-07-01
Infrared-ultraviolet double resonance (IRUVDR) experiments have been implemented in the ultra-cold environment provided by a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme) apparatus. This has enabled us to measure rate coefficients for rotational energy transfer in collisions between NO and He of two kinds: those relating to total removal from a specific rovibrational state of NO( X2?; ? = 1/2; ? = 3; J = 0.5, 3.5 or 6.5 ) and also state-to-state rate coefficients for transfer from these levels. Using different Laval nozzles, results have been obtained at four different temperatures: 149, 63, 27 and 15 K, and are also reported for 295 K.
Troitskaya, Yu.; Ezhova, E.; Sergeev, D.; Kandaurov, A.; Baidakov, G.; Vdovin, M.
2012-04-01
The most important characteristics that determine the interaction between atmosphere and ocean are fluxes of momentum, heat and moisture. For their parameterization the dimensionless exchange coefficients (the surface drag coefficient CD and the heat transfer coefficient or the Stanton number CT) are used. Numerous field and laboratory experiments show that CD increases with increasing wind speed. This is due to the fact that the transfer of the momentum wave disturbances, or form drag, increases with increasing wind speed, which is accompanied by broadening the wind wave spectrum. The dependence of heat transfer coefficient CT on the wind speed is not well studieds and the role of the mechanism associated with the wave disturbances in the mass transfer is poorly understood. Observations and laboratory data show that this dependence is weaker than for the CD, and there are differences in the character of the dependence in different data sets. For example, the algorithm COARE 3.0 (see [1] indicates a slight increase in CT with increasing wind speed U10, a similar dependence was obtained in [2] and the laboratory experiment, [3], and in [4] a dependence of CT on the wind speed was not found. The weak dependence of the CT on U10 is confirmed by theoretical models [5], but the details of the dependence (growing or dropping) were sensitive to the choice of model. The purpose of this paper is investigation of the effect of waves on the surface of the water on the exchange of momentum and mass to drive the boundary layer of air and from this point of view it largely follows [5]. The main difference is related to the used model of the marine atmospheric boundary layer, in which the perturbations induced by the waves on the water surface in the atmosphere are calculated. It is a generalization of the model developed for a homogeneous atmosphere in [6] to the case of a stratified marine atmospheric boundary layer. The model was recently verified by comparing with experimental results [7] and direct numerical modeling [8]. Two first-order closing models of turbulence are discussed. In the first model, wave-dependent eddy viscosity and heat conductivity are postulated by decreasing turbulent momentum flux near the wavy water surface due to wave momentum transfer. In the second model, the turbulent transfer coefficients are parameterized only by the constant wind friction velocity. Special experiments were carried out in the wind-wave flume to investigate velocity and temperature distribution in the stratified air boundary layer above the water surface disturbed by paddle generated waves. Experiments showed that in accordance with the second closing model the air flow velocity decreases with the growth of the surface wave amplitude and the temperature profile was wave-independent within experimental errors. Surface wave spectrum is an important element of the model. We investigated sensitivity of the model to spectral models, including spectra suggested by [9-12], which describe waves in wide range of wavelengths from energy-containing scales to centimeters and millimeters. Comparing of the theoretical calculations with the experimental algorithm TOGA-COARE [1] shows, that the best agreement takes place, when the Hwang spectrum [12] corrected at high wind conditions is used.
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.
Chana, KS; Haller, BR
2010-01-01
For gas turbines, accurate prediction of the external heat transfer coefficient on the high pressure (HP) turbine rotor blades is of immense importance, as this component is critical and operates at material limits. Furthermore the external heat load is the governing boundary condition for the design of the internal cooling system of the blade. There is a continuous drive to increase the turbine entry temperature to increase the cycle efficiency, whilst developing blade cooling systems with h...
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...
Energy Technology Data Exchange (ETDEWEB)
Miller, W.A.
1999-03-24
Experiments were conducted in a laboratory to investigate the absorption of water vapor into a falling-film of aqueous lithium bromide (LiBr). A mini-absorber test stand was used to test smooth tubes and a variety of advanced tube surfaces placed horizontally in a single-row bundle. The bundle had six copper tubes; each tube had an outside diameter of 15.9-mm and a length of 0.32-m. A unique feature of the stand is its ability to operate continuously and support testing of LiBr brine at mass fractions {ge} 0.62. The test stand can also support testing to study the effect of the failing film mass flow rate, the coolant mass flow rate, the coolant temperature, the absorber pressure and the tube spacing. Manufacturers of absorption chillers add small quantities of a heat and mass transfer additive to improve the performance of the absorbers. The additive causes surface stirring which enhances the transport of absorbate into the bulk of the film. Absorption may also be enhanced with advanced tube surfaces that mechanically induce secondary flows in the falling film without increasing the thickness of the film. Several tube geometry's were identified and tested with the intent of mixing the film and renewing the interface with fresh solution from the tube wall. Testing was completed on a smooth tube and several different externally enhanced tube surfaces. Experiments were conducted over the operating conditions of 6.5 mm Hg absorber pressure, coolant temperatures ranging from 20 to 35 C and LiBr mass fractions ranging from 0.60 through 0.62. Initially the effect of tube spacing was investigated for the smooth tube surface, tested with no heat and mass transfer additive. Test results showed the absorber load and the mass absorbed increased as the tube spacing increased because of the improved wetting of the tube bundle. However, tube spacing was not a critical factor if heat and mass transfer additive was active in the mini-absorber. The additive dramatically affected the hydrodynamics of the falling film and a droplet flow regime was evident for testing at all tube spacings. The mechanical mixing of the advanced surfaces increased the mass transfer to about 75% of that observed on a smooth tube bundle, tested with heat and mass transfer additive. Testing with heat and mass transfer additive and advanced surfaces demonstrated a synergistic effect which doubled the mass absorbed from that observed with only the advanced surface. The overall film-side heat transfer coefficient for the advanced tube bundles doubled with the addition of 500-wppm of 2-ethyl-1- hexanol.
Fransson, T. H.
1992-04-01
A two-dimensional section of the last stage of a steam turbine blade has been investigated experimentally in an annular non-rotating cascade facility as regards to its steady-state and time-dependent aerodynamic characteristics at design and off-design conditions. The unsteady experimental data obtained with the blades vibrating in the “travelling wave” mode indicate that one of the main reasons for the flutter susceptibility of the cascade lies in the high expansion and following shock wave close to the blade suction surface leading edge and the corresponding high unsteady loading. The decomposition of the experimental data into unsteady aerodynamic influence coefficients validates this conclusion and also shows that another reason for the flutter susceptibility can be found in the fact that the cascades is overlapped for a part of the blade surface where the local flow velocities are close to sonic. The unsteady aerodynamic influence coefficients show that the instability arises because of the time dependent aerodynamic coupling effects between, essentially, the reference blade and its immediate suction surface and, to a lesser extent, pressure surface neighbors.
Ishii, K.; Fujita, A.; Toyama, S.; Terakawa, A.; Matsuyama, S.; Arai, H.; Osada, N.; Takyu, S.; Matsuyama, T.; Koshio, S.; Watanabe, K.; Ito, S.; Kasahara, K.
Edible wild plants growing in the area around the Fukushima Daiichi nuclear power plant remain contaminated. It is important to identify plants with low levels of contamination for the restoration of agriculture in the area. We collected specimens of 10 wild plant species growing in Iitate village which is one of the most highly contaminated areas and also sampled the soil beneath each plant. We measured the specific activity of 137Cs and the concentrations of Na, Mg, Al, Si, P, S, K, Ca, Fe, Zn, Rb and Sr in these samples using a germanium detector and PIXE analysis, respectively. We compared the soil-plant transfer coefficient of 137Cs with those of each element and determined their correlation with 137Cs. It was found that a low Sr transfer coefficient could be used to determine the plants with a low 137Cs transfer coefficient. We suggest that PIXE analysis is a useful analysis technique for agricultural remediation projects in highly contaminated areas around the Fukushima Daiichi nuclear power plant.
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)
Heat transfer characteristics in closed-loop spray cooling of micro-structured surfaces
International Nuclear Information System (INIS)
With water as the working fluid, experiments on the heat transfer characteristics of spray cooling of micro-structured surfaces were performed in a closed loop system. Experimental data were analyzed in the view of the ratio between convective heat transfer and phase change heat transfer. The results indicate that heat transfer is obviously enhanced for micro-channel surfaces relative to the flat surface because of higher phase change heat transfer. For the geometries tested at lower surface temperature, the straight finned surface has the largest heat flux; while at higher surface temperature, the cubic pin finned surface has the largest heat flux. Heat fluxes of all the surfaces grow with increasing flow rates, except for the straight finned surface under lower surface temperature. The ratio of phase change to total heat transfer is bigger than 20% for the flat surface, and higher than 50% for micro-structured surface. Critical heat fluxes of 159.1 W/cm2, 120.2 W/cm2, and 109.8 W/cm2 are attained respectively for cubic pin finned, straight finned and flat surfaces when the flow rate is 15.9 mL/min, and the corresponding evaporation efficiency are 96.0%, 72.5%, 67.1%. (authors)
Doña, J. M.; González-Velasco, J.
1992-08-01
By using a method based on the time dependence of the surface roughness factor of electrodispersed gold electrodes it was possible to estimate values of the surface diffusion coefficients (Ds) of gold atoms in contact with an 1M HClO4 electrolytic solution at room temperature and as a function of the potential. The exponential growth of Ds with E at potentials positive with respect to the zero charge potential (Ez), is interpreted as a consequence of the increase in the surface mobility of gold atoms, associated with their growing interactions with species in the electrolyte (water molecules), and the consequent decrease of their interactions with bulk gold atoms, i.e. with the loss in metallic character inherent in the use of individual orbitais in the formation of covalent bonds with hydroxyls arising from water molecules.
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.
International Nuclear Information System (INIS)
Full text of publication follows: Flow Accelerated Corrosion (FAC) is a corrosion mechanism that results in wall thinning in piping systems and components. FAC on carbon steels in pure water has occurred in a number of industry and power plant. A pipe wall thinning due to the FAC at nuclear power plant is just reported in confined to carbon steel pipe on the secondary system which does not equip a radioactive component. Recently, at Canadian Deuterium Uranium type reactor, it is reported that the feeder lines suffer the wall thinning on the primary system to equip 380 feeder pipes. Differently from the fast FAC rate of the secondary system on PWR, FAC rate of feeder pipes on CANDU is not more than the 0.2 mm/year. Although the FAC rate of feeder pipe is relatively slow, the narrow thickness margin of 2.6089 mm is endangered sufficiently by only the slow FAC rate. The FAC is governed by the mass transfer coefficient which is determined by the flow field. To well predict the FAC rate, mass transfer coefficient should be well measured or calculated. New measurement method of mass transfer coefficient is developed to obtain the coefficient for the complex shape like feeder pipe. The method evaluated the naphthalene sublimation method to apply it under the water flow. The naphthalene sublimation method can be used to study mass and heat transfer with confidence for a variety of applications, but with certain restrictions. At present, Plaster of paris method can modified the sublimation method to overcome the restrictions. This method is particularly useful in complex flows on geometries and for flows with large gradients in wall transport rate. The test specimen can be easily prepared by several methods, including dipping, machining, spraying, and casting. The local transfer coefficients can be determined with high accuracy and in detail by automated measurement systems that eliminate most human errors during the measurement process. To evaluate the method, the experiments are performed to compare with other correlations for straight pipe and feeder pipes. The comparisons are good agreement with error of 10 % for the straight pipe and are agreement with the CFX 4 calculation results for the feeder pipe. (authors)
International Nuclear Information System (INIS)
We report on nanoimprinting of polymer thin films at 30 nm scale resolution using two types of ultraviolet (UV)-curable, flexible polymer molds: perfluoropolyether (PFPE) and polyurethane acrylate (PUA). It was found that the quality of nanopatterning at the 30 nm scale is largely determined by the combined effects of surface tension and the coefficient of thermal expansion of the polymer mold. In particular, the polar component of surface tension may play a critical role in clean release of the mold, as evidenced by much reduced delamination or broken structures for the less polarized PFPE mold when patterning a relatively hydrophilic PMMA film. In contrast, such problems were not notably observed with a relatively hydrophobic PS film for both polymer molds. In addition, the demolding characteristic was also influenced by the coefficient of thermal expansion so that no delamination or uniformity problems were observed when patterning a UV-curable polymer film at room temperature. These results suggest that a proper polymeric mold material needs to be chosen for patterning polymer films under different surface properties and processing conditions, providing insights into how a clean demolding characteristic can be obtained at 30 nm scale nanopatterning. (paper)
Sustained frictional instabilities on nanodomed surfaces: Stick-slip amplitude coefficient
DEFF Research Database (Denmark)
Quignon, Benoit; Pilkington, Georgia A.; Thormann, Esben; Claesson, Per M.; Ashfold, Michael N R; Mattia, Davide; Leese, Hannah; Davis, Sean A.; Briscoe, Wuge H.
2013-01-01
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...
Ivanova, Anna
2010-01-01
The detailed mathematical model of heat and mass transfer of steel ingot of curvilinear continuous casting machine is proposed. The process of heat and mass transfer is described by nonlinear partial differential equations of parabolic type. Position of phase boundary is determined by Stefan conditions. The temperature of cooling water in mould channel is described by a special balance equation. Boundary conditions of secondary cooling zone include radiant and convective components of heat exchange and account for the complex mechanism of heat-conducting due to airmist cooling using compressed air and water. Convective heat-transfer coefficient of secondary cooling zone is unknown and considered as distributed parameter. To solve this problem the algorithm of initial adjustment of parameter and the algorithm of operative adjustment are developed.
International Nuclear Information System (INIS)
In the present paper, the effect of Delta-Wing Vortex Generators(DWVGs) on heat transfer of the plate fin-oval tube heat exchanger was experimentally studied. The local heat transfer coefficient of the tube surface of one kind of DWVGs arrangement were measured by naphthalene sublimation technique for Reynolds numbers of 2000 ? 3200 and angles of attack of DWVG of 30 .deg. ? 60 .deg.. As the results, compared to the case without DWVGs, the heat transfer of the plate fin surface with DWVGs was enhanced from upstream to downstream in the test region. The heat transfer were significantly affected by angles of attack of DWVGs as well as Reynolds number. It showed that the result of 45 .deg. was best within test angles
Behaviour of Tc in surface soils. Distribution coefficients of Tc obtained by a batch technique
International Nuclear Information System (INIS)
In order to investigate behavior of Technetium (Tc) in agricultural soil, variation region and probability frequency distribution of Tc distribution coefficient (Tc-Kd) was obtained by using 41 kinds of paddy field soils and 45 kinds of farm soils collected from all over Japan. And, correlation between the obtained Tc-Kds and various physical and chemical properties of the soils was investigated. The distribution coefficient was obtained by a batch technique using Tc-95 m (chemical form: TcO4- for a tracer. The obtained Kds were very small, which were 0.02-8.1 L/kg in paddy field soils and 0.05-2.0 L/kg in farm soils. Both of the distributions of the Kds were judged to be a log-normal form, of which geometrical mean values were 0.71 L/kg (paddy field soil) and 0.37/kg (farm soil), respectively. The obtained Kd values could not be found any large difference between in the paddy field soil and in the farm soil. Since the oxidation-reduction potentials in solution scarcely changed, this reason was thought that all the obtained Kd values would be under an oxidative atmosphere. The soil features shown by high correlation with Kd value of the farm soil were active Al, active Fe, total carbon, total nitrogen, and water content. On the other hand, on the paddy field soil, so high correlation could not be found in any soil feature. As this reason could not be clear, it was presumed to be one of reasons to measure the soil feature under oxidative atmosphere. (G.K.)
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.
Effect of U3O8 specific surface area on in vitro dissolution, biokinetics, and dose coefficients
International Nuclear Information System (INIS)
The purpose of this study was to investigate the effect of the specific surface area (SSA) of U3O8, sampled from different processes, on its in vitro dissolution, its biokinetics in rats, and dose coefficient. A knowledge of the manufacturing process as well as the physico-chemical properties of uranium oxides are necessary to understand why the solubility and consequently the dose may vary for the same chemical form of a compound. Eight preparations of U3O8 with different SSA, have been characterised. In vitro chemical dissolution tests, in culture medium, have shown an increase of solubility with SSA. In vivo experiments involving intratracheal deposition of a suspension of the oxides showed that the amount of uranium absorbed into blood increased 3-fold when the SSA increased 5-fold. Calculations of the dose coefficients from in vitro dissolution parameters, have shown a decrease from 4.30 to 1.75 ?Sv.Bq-1 when the SSA increased from 0.7 to 15.5 m2.g-1. Dose coefficients calculated from in vivo absorption parameters varied from 5.5 to 4.2 ?Sv.Bq-1, when the SSA increased from 0.7 to 3.2 m2.g-1. (author)
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 %.
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.
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)
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...
International Nuclear Information System (INIS)
Two-phase friction pressure drop and heat transfer coefficients in a once-through steam generator with helically coiled tubes were investigated with the model test rig of an integrated type marine water reactor. As the dimensions of the heat transfer tubes and the thermal-fluid conditions are almost the same as those of real reactors, the data applicable directly to the real reactor design were obtained. As to the friction pressure drop, modified Kozeki's prediction which is based on the experimental data by Kozeki for coiled tubes, agreed the best with the experimental data. Modified Martinelli-Nelson's prediction which is based on Martinelli-Nelson's multiplier using Ito's equation for single-phase flow in coiled tube, agreed within 30%. The effect of coiled tube on the average heat transfer coefficients at boiling region were small, and the predictions for straight tube could also be applied to coiled tube. Schrock-Grossman's correlation agreed well with the experimental data at the pressures of lower than 3.5 MPa. It was suggested that dryout should be occurred at the quality of greater than 90% within the conditions of this report. (author)
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.
Heat Transfer Measurements on Surfaces with Natural Ice Castings and Modeled Roughness
Breuer, Kenneth S.; Torres, Benjamin E.; Orr, D. J.; Hansman, R. John
1997-01-01
An experimental method is described to measure and compare the convective heat transfer coefficient of natural and simulated ice accretion roughness and to provide a rational means for determining accretion-related enhanced heat transfer coefficients. The natural ice accretion roughness was a sample casting made from accretions at the NASA Lewis Icing Research Tunnel (IRT). One of these castings was modeled using a Spectral Estimation Technique (SET) to produce three roughness elements patterns that simulate the actual accretion. All four samples were tested in a flat-plate boundary layer at angle of attack in a "dry" wind tunnel test. The convective heat transfer coefficient was measured using infrared thermography. It is shown that, dispite some problems in the current data set, the method does show considerable promise in determining roughness-induced heat transfer coefficients, and that, in addition to the roughness height and spacing in the flow direction, the concentration and spacing of elements in the spanwise direction are important parameters.
Fuhrmann, Eckart; Dreyer, Michael E.
2014-06-01
In this paper, we analyzed the heat and mass transfer at a free surface under microgravity conditions. The SOURCE-II (Sounding Rocket COMPERE Experiment) experiment was performed on a suborbital flight in February 2012 from Esrange in North Sweden. It provided representative data with respect to solid, liquid, and vapor temperatures as well as the visible surface position. The objectives were to quantify the deformation of the free liquid surface and to correlate the apparent contact angle to a characteristic temperature difference between subcooled liquid and superheated wall. Furthermore, the influence of evaporation and condensation at the liquid/vapor interface and at the superheated wall must be taken into account to analyze heat and mass fluxes due to a characteristic temperature difference. In the following, we show evidently that the magnitude of the apparent contact angle depends on the exerted specific pressurizations of the vapor phase during the experiment and hence on the change in the saturation temperature at the free surface. The characteristic temperature difference is defined with respect to the wall temperature in the vicinity of the contact line and the saturation temperature. Therefore, apparent contact angle and temperature difference can be correlated and indicate a specific characteristic. Concerning the heat and mass transfer at the free liquid surface and the contact line, two different methods are presented to evaluate the net mass due to phase change within a certain time interval. In the first approach, the mass flow rate is calculated by means of the ideal gas law and its derivatives with respect to temperature and pressure. The second approach calculates the heat flux as well as the mass flux at the wall and in the region of the free liquid surface. In these cases, a specific heat transfer coefficient and a thermal boundary layer thickness are used.
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.
Nam, Seung-il
2009-01-01
We investigate the polarization transfer coefficients C_(x,z) for the gamma p -> K^+ Lambda(1520,3/2^-) reaction process, in which the photon is polarized circularly and the Lambda(1520,3/2^-) along the x- or z-axis. To this end, we employ the effective Lagrangian method at tree level and the gauge-invariant form factor scheme. In addition to the Born terms, (s,u,t_K,t_K^*)-channels and contact term, we include the nucleon resonance D_{13}(2080) in the s-channel. We compute ...
A. C. Rizzi Jr.; M. L. Passos; J. T. FREIRE
2009-01-01
This work is aimed at modeling the heat transfer mechanism in a fluidized bed of grass seeds (Brachiaria brizantha) for supporting further works on simulating the drying of these seeds in such a bed. The three-phase heat transfer model, developed by Vitor et al. (2004), is the one used for this proposal. This model is modified to uncouple one of the four adjusted model parameters from the gas temperature. Using the first set of experiments, carried out in a laboratory scale batch fluidized be...
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.)
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.
Boiling Heat Transfer on Superhydrophilic, Superhydrophobic, and Superbiphilic Surfaces
Betz, Amy Rachel; Jenkins, James; 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 nucleat...
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.
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.
Development of surface wettability characteristics for enhancing pool boiling heat transfer
International Nuclear Information System (INIS)
For several centuries, many boiling experiments have been conducted. Based on literature survey, the characteristic of heating surface in boiling condition played as an important role which mainly influenced to boiling performance. Among many surface factor, the fact that wettability effect is significant to not only the enhancement of critical heat flux(CHF) but also the nucleate boiling heat transfer is also supported by other kinds of boiling experiments. In this regard, the excellent boiling performance (a high CHF and heat transfer performance) in pool boiling could be achieved through some favorable surface modification which satisfies the optimized wettability condition. To find the optimized boiling condition, we design the special heaters to examine how two materials, which have different wettability (e.g. hydrophilic and hydrophobic), affect the boiling phenomena. The special heaters have hydrophobic dots on hydrophilic surface. The contact angle of hydrophobic surface is 120 .deg. to water at the room temperature. The contact angle of hydrophilic surface is 60 .deg. at same conditions. To conduct the experiment with new surface condition, we developed new fabrication method and design the pool boiling experimental apparatus. Through this facility, we can the higher CHF on pattern surface than that on hydrophobic surface, and the higher boiling heat transfer performance on pattern surface than that on hydrophilic surface. Based on this experimental results, we concluded that we proposed new heating surface condition and surface fabrication method to realize the best boiling condition by modified heating surface condition
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.
Directory of Open Access Journals (Sweden)
Ali Abdul-Rahman N. Jasim
2009-01-01
Full Text Available 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 column is 1.5m and the ratio of the draught tube diameter to the column diameter equals 0.5 and the air dispersion into the base of the draught tube using a multi hole tuyere is equivalent to a diameter of 0.15 mm and has a free sectional distributor area of 61%.Water and three aqueous solutions of 10% concentration methanol, ethanol and isopropanol, were used as the liquid phase. The various gas velocity (0.01-0.1 meter/sec are used and the results were compared in case of using water only without the addition of alcohols. From experimental observations, and KLa increase with increasing gas velocity and with the coalescence inhibition of liquid.
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.
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...
Surface-to-food pesticide transfer as a function of moisture and fat content.
Vonderheide, Anne P; Bernard, Craig E; Hieber, Thomas E; Kauffman, Peter E; Morgan, Jeffrey N; Melnyk, Lisa Jo
2009-01-01
Transfer of pesticides from household surfaces to foods may result in excess dietary exposure in children (i.e., beyond that inherent in foods due to agricultural application). In this study, transfer was evaluated as a function of the moisture and fat content of various foods. Surfaces chosen for investigation were those commonly found in homes and included Formica, ceramic tile, plastic, carpet, and upholstery fabric. Each surface type was sprayed with an aqueous emulsion of organophosphates, fipronil, and synthetic pyrethroids. In the first phase of the study, multiple foods (apples, watermelon, wheat crackers, graham crackers, white bread, flour tortillas, bologna, fat-free bologna, sugar cookies, ham, Fruit Roll-ups, pancakes, and processed American cheese) were categorized with respect to moisture and fat content. All were evaluated for potential removal of applied pesticides from a Formica surface. In the second phase of the study, representative foods from each classification were investigated for their potential for pesticide transfer with an additional four surfaces: ceramic tile, plastic, upholstery, and carpet. Moisture content, not fat, was found to be a determining factor in most transfers. For nearly all surfaces, more efficient transfer occurred with increased hardness (Formica and ceramic tile). Comparatively, the polymer composition of the plastic delivered overall lower transfer efficiencies, presumably due to an attraction between it and the organic pesticides of interest. PMID:18414514
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)
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
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.
Varnek, Alexandre; Gaudin, Cédric; Marcou, Gilles; Baskin, Igor; Pandey, Anil Kumar; Tetko, Igor V
2009-01-01
Two inductive knowledge transfer approaches - multitask learning (MTL) and Feature Net (FN) - have been used to build predictive neural networks (ASNN) and PLS models for 11 types of tissue-air partition coefficients (TAPC). Unlike conventional single-task learning (STL) modeling focused only on a single target property without any relations to other properties, in the framework of inductive transfer approach, the individual models are viewed as nodes in the network of interrelated models built in parallel (MTL) or sequentially (FN). It has been demonstrated that MTL and FN techniques are extremely useful in structure-property modeling on small and structurally diverse data sets, when conventional STL modeling is unable to produce any predictive model. The predictive STL individual models were obtained for 4 out of 11 TAPC, whereas application of inductive knowledge transfer techniques resulted in models for 9 TAPC. Differences in prediction performances of the models as a function of the machine-learning method, and of the number of properties simultaneously involved in the learning, has been discussed. PMID:19125628
Heat transfer performance of the thermal entrance region of the narrow ribbed-surface channel
Energy Technology Data Exchange (ETDEWEB)
Suzuki, Akira; Kaminaga, Masanori; Hino, Ryutaro [Center for Neutron Science, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Kanamaru, Nobuhisa; Sudo, Yukio
1999-02-01
The heat transfer argumentation in the thermal entrance region of a narrow rectangular channel roughened with repeated ribs was investigated experimentally for removing high-density heat generated in a solid target. This solid target works as a spallation neutron source coupled with a proton beam accelerator of 1.5 MW power. Experimental results showed that the thermal entrance region could extent to the range of 50-60 times as long as the equivalent diameter from the coolant inlet, and that the heat transfer coefficient in the region could be estimated with the Gnielinski`s correlation. (author)
Heat transfer performance of the thermal entrance region of the narrow ribbed-surface channel
International Nuclear Information System (INIS)
The heat transfer argumentation in the thermal entrance region of a narrow rectangular channel roughened with repeated ribs was investigated experimentally for removing high-density heat generated in a solid target. This solid target works as a spallation neutron source coupled with a proton beam accelerator of 1.5 MW power. Experimental results showed that the thermal entrance region could extent to the range of 50-60 times as long as the equivalent diameter from the coolant inlet, and that the heat transfer coefficient in the region could be estimated with the Gnielinski's correlation. (author)
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.)
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
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
Tong, J.
2014-12-01
With the development of modern agriculture, large amount of fertilizer and pesticide outflow from farming land causes great wastes and contributes to serious pollution of surface water and groundwater, which threatens ecological environment and human life. In this paper, laboratory experiments are conducted to simulate adsorbed Cr(VI) transfer from soil into runoff. A two-layer in-mixing analytical model is developed to to analyze laboratory experimental results. A data assimilation (DA) method via the ensemble Kalman filter (EnKF) is used to update parameters and improve predictions. In comparison with the observed data, DA results are much better than forward model predictions. Based on the used rainfall and relevant physical principles, the updated value of the incomplete mixing coefficient is about 7.4 times of the value of the incomplete mixing coefficient in experiment 1 and about 14.0 times in experiment 2, which indicates the loss of Cr(VI) in soil solute is mainly due to infiltration, rather than surface runoff. With the increase of soil adsorption ability and the mixing layer depth, the loss of soil solute will decrease. These results provide information for preventing and reducing the agricultural nonpoint source pollution.
The role of a convective surface in models of the radiative heat transfer in nanofluids
Energy Technology Data Exchange (ETDEWEB)
Rahman, M.M., E-mail: mansurdu@yahoo.com; Al-Mazroui, W.A.; Al-Hatmi, F.S.; Al-Lawatia, M.A.; Eltayeb, I.A.
2014-08-15
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 Al{sub 2}O{sub 3} and titanium dioxide TiO{sub 2} 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.
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
Tiwari, Akhilesh; Kondjoyan, Alain; Fontaine, Jean-Pierre
2012-07-01
The phenomenon of heat and mass transfer by condensation of water vapour from humid air involves several key concepts in aerobic bioreactors. The high performance of bioreactors results from optimised interactions between biological processes and multiphase heat and mass transfer. Indeed in various processes such as submerged fermenters and solid-state fermenters, gas/liquid transfer need to be well controlled, as it is involved at the microorganism interface and for the control of the global process. For the theoretical prediction of such phenomena, mathematical models require heat and mass transfer coefficients. To date, very few data have been validated concerning mass transfer coefficients from humid air inflows relevant to those bioprocesses. Our study focussed on the condensation process of water vapour and developed an experimental set-up and protocol to study the velocity profiles and the mass flux on a small size horizontal flat plate in controlled environmental conditions. A closed circuit wind tunnel facility was used to control the temperature, hygrometry and hydrodynamics of the flow. The temperature of the active surface was controlled and kept isothermal below the dew point to induce condensation, by the use of thermoelectricity. The experiments were performed at ambient temperature for a relative humidity between 35-65% and for a velocity of 1.0 ms?¹. The obtained data are analysed and compared to available theoretical calculations on condensation mass flux. PMID:22367641
Effects of surface roughness on heat transfer to gas turbine blades
Turner, A. B.; Tarada, F. H. A.; Bayley, F. J.
1985-09-01
A brief, preliminary sample of results of an investigation into the effect of surface roughness on heat transfer to gas turbine blades is presented. Only the kind of roughness due to the accretion of dirt or dust is considered and this has been simulated in cascade flow by attaching various grades of abrasive powders to the blade surface with a water soluble adhesive. A significant increase in heat is reported particularly with high free stream turbulent levels. Roughness on the pressure surface alone is shown to increase the overall heat transfer without any corresponding increase in profile loss.
DEFF Research Database (Denmark)
Henningsen, Poul; Hattel, Jesper Henri; Wanheim, Tarras
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 thermo...
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.
Connan, O; Solier, L; Hébert, D; Maro, D; Lamotte, M; Voiseux, C; Laguionie, P; Cazimajou, O; Le Cavelier, S; Godinot, C; Morillon, M; Thomas, L; Percot, S
2014-11-01
The aim of this work was to study the near-field dispersion of (85)Kr around the nuclear fuel reprocessing plant at La Hague (AREVA NC La Hague - France) under stable meteorological conditions. Twenty-two (85)Kr night-time experimental campaigns were carried out at distances of up to 4 km from the release source. Although the operational Gaussian models predict for these meteorological conditions a distance to plume touchdown of several kilometers, we almost systematically observed a marked ground signal at distances of 0.5-4 km. The calculated atmospheric transfer coefficients (ATC) show values (1) higher than those observed under neutral conditions, (2) much higher than those proposed by the operational models, and (3) higher than those used in the impact assessments. PMID:25078471
Energy Technology Data Exchange (ETDEWEB)
Linek, V., E-mail: linekv@vscht.cz [Prague Institute of Chemical Technology, Department of Chemical Engineering, CZ-166 28 Prague 6 (Czech Republic); Košek, L. [Research Centre ?ež, CZ-250 68 Husinec-?ež (Czech Republic); Moucha, T.; Rejl, F.J.; Korda?, M.; Valenz, L.; Opletal, M. [Prague Institute of Chemical Technology, Department of Chemical Engineering, CZ-166 28 Prague 6 (Czech Republic)
2014-11-15
Highlights: • The model of hydrogen isotopes desorption from lead lithium alloy in packed column is presented. • Mass transfer coefficient k{sub L}a 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 k{sub L}a 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)
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)
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
Lychagin, E V; Nesvizhevsky, V V; Nekhaev, G V; Taldaev, R R; Strelkov, A V; Shetsov V N
2001-01-01
Inelastic scattering of neutrons with small energy transfer of \\sim 10^{-7} eV was investigated using gravitational UCN spectrometer. The probability of such a process at stainless steel and beryllium surfaces was measured. It was also estimated at copper surface. The measurement showed that the detected flux of neutrons scattered at beryllium and copper surfaces is \\sim 2 times higher at room temperature compared to that at the liquid nitrogen temperature.
Fluctuating surface-current formulation of radiative heat transfer: theory and applications
Rodriguez, Alejandro W.; Reid, M. T. Homer; Johnson, Steven G.
2013-01-01
We describe a novel fluctuating-surface current formulation of radiative heat transfer between bodies of arbitrary shape that exploits efficient and sophisticated techniques from the surface-integral-equation formulation of classical electromagnetic scattering. Unlike previous approaches to non-equilibrium fluctuations that involve scattering matrices---relating "incoming" and "outgoing" waves from each body---our approach is formulated in terms of "unknown" surface currents...
Saadi, Zahra; Saadi, Reyhaneh; Fazaeli, Reza
2015-09-01
In the present study, the removal of metal ions Pb(II) using nanostructured ?-alumina was investigated by tests on batch operations and fixed-bed columns. Optimization was determined for factors effective on adsorption such as pH, contact time of metal solution with adsorbent and initial solution concentration. The optimum pH level was determined at 4.5 and the maximum adsorption percentage was achieved at 150 minutes. pHpzc was measured 8.3 for nanostructured ?-Al2O3. The Langmuir, Freundlich and Temkin isotherms were used to analyze the experimental data. The Langmuir isotherm model showed the best agreement with the experimental data. The model showed evaluations for maximum adsorption capacity of adsorbent at 119.04 mg/g and adsorbent bed performance for different flow rates, bed heights and influent concentrations were also investigated. The lumped method was used to solve the bed equations, to predict the breakthrough curve and model overall mass transfer coefficient (Koverall) and axial dispersion coefficient (Dz) parameters to make comparisons with experimental results. PMID:26322764
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
Directory of Open Access Journals (Sweden)
B. Dieng
2015-12-01
Full Text Available : The cold battery is a heat exchanger between two fluids, air (secondary fluid and iced water (primary fluid.The cold battery is composed of two heat exchangers in series, one of which is made up of flat-plate in galvanized steel serving as a reservoir for the iced water and the other one a copper shelland-tube exchanger with aluminum cooling blades. The two heat exchangers a connected pipe of the same diameter. These pipes will permit the transit of the iced water coming from the flat-plate exchanger by gravitation towards the tubes of the second exchanger. These two heat exchangers are incorporated in a galvanized container coupled with a centrifugal fan for the improvement of the thermal comfort. The water, after passing through the two heat exchangers is stored in an adiabatic reservoir and will serve as a water fountain [1].The modeling will be done in a humid mode that is the temperature of the surface of the battery is very low compared with the dew temperature of air. The cooling allows the condensation of water vapor [2].The characterization of that cold battery will be done in a dry regime where there is only one heat exchanger and the quantity of vapor contained in the air does not vary and also the surface temperature of the battery is greater than the dew temperature of air [2 ; 3]..
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.
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.
Fluctuating surface-current formulation of radiative heat transfer for arbitrary geometries
Rodriguez, Alejandro W.; Reid, M. T. Homer; Johnson, Steven G.
2012-01-01
We describe a fluctuating surface-current formulation of radiative heat transfer, applicable to arbitrary geometries, that directly exploits standard, efficient, and sophisticated techniques from the boundary-element method. We validate as well as extend previous results for spheres and cylinders, and also compute the heat transfer in a more complicated geometry consisting of two interlocked rings. Finally, we demonstrate that the method can be readily adapted to compute the...
E-transfer of materials surface engineering e-foresight results
A.D. Dobrza?ska-Danikiewicz; L.A. Dobrza?ski; Mazurkiewicz, J; B. Tomiczek; ?. Reimann
2011-01-01
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...
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.
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
Surface energy equation for heat transfer process in a pebble fuel
Energy Technology Data Exchange (ETDEWEB)
Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico); Castillo-Jiménez, V. [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico); Herranz-Puebla, L.E. [División de Fisión Nuclear, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avda. Complutense, 22, 28040 Madrid (Spain); Vázquez-Rodríguez, R. [Área de Ingeniería en Recursos Energéticos, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186 Col. Vicentina, México, DF 09340 (Mexico)
2014-12-15
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.
Nature of the bonding, surface relaxation and charge transfer of Au dimmers on an MgO(100 surface
Directory of Open Access Journals (Sweden)
C. Quintanar
2012-01-01
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.
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
Energy Technology Data Exchange (ETDEWEB)
Mitsutake, Toru; Morooka, Shin-ichi; Miura, Shigeru; Akiba, Miyuki; Sato, Hisaki; Shirakawa, Ken-etsu; Oosato, Tetsuo; Yamamoto, Seiji [Toshiba Co., Kanagawa (Japan)
2002-07-01
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 TiO{sub 2} coated heater rod. TiO{sub 2} 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 TiO{sub 2} coating. TiO{sub 2} 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)
A simple technique for the transfer of thin gold layer from poly(methyl methacrylate) (PMMA) stamp onto SU-8 photoresist is described and verified. The procedure comprises sputtering of thin gold layer on flat or laser patterned PMMA, bringing the PMMA stamp into contact with photoresist substrate, transferring of the gold layer onto photoresist and finally dissolution of the PMMA stamp. Surface morphology of as sputtered and transferred gold layers was determined by profilometry, confocal microscopy, and atomic force microscopy (AFM) techniques at three different scales. Electrical properties were examined by conductive AFM technique. The transfer from patterned PMMA stamp leads to simultaneous patterning of the gold layer and creation of a system of ordered conductive gold strips separated by non-conductive areas on photoresist surface. - Highlights: • Transfer of gold layer by printing technique has been investigated. • Soluble PMMA has been used as stamp and insoluble photoresist as substrate. • Anti-adhesive interlayer was not necessary. • Flat or patterned gold film transfer has been performed. • Creation of conductive ordered gold strips occurs during transfer procedure
Determination of the transfer function for optical surface topography measuring instruments—a review
International Nuclear Information System (INIS)
A significant number of areal surface topography measuring instruments, largely based on optical techniques, are commercially available. However, implementation of optical instrumentation into production is currently difficult due to the lack of understanding of the complex interaction between the light and the component surface. Studying the optical transfer function of the instrument can help address this issue. Here a review is given of techniques for the measurement of optical transfer functions. Starting from the basis of a spatially coherent, monochromatic confocal scanning imaging system, the theory of optical transfer functions in three-dimensional (3D) imaging is presented. Further generalizations are reviewed allowing the extension of the theory to the description of conventional and interferometric 3D imaging systems. Polychromatic transfer functions and surface topography measurements are also discussed. Following presentation of theoretical results, experimental methods to measure the optical transfer function of each class of system are presented, with a focus on suitable methods for the establishment of calibration standards in 3D imaging and surface topography measurements. (topical review)
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...
Technologies for Lunar Surface Power Systems Power Beaming and Transfer
Marzwell, Neville; Pogorzelski, Ronald J.; Chang, Kai; Little, Frank
2008-01-01
Wireless power transmission within a given working area is required or enabling for many NASA Exploration Systems. Fields of application include robotics, habitats, autonomous rendezvous and docking, life support, EVA, and many others. In robotics applications, for example, the robots must move in the working area without being hampered by power cables and, meanwhile, obtain a continuous and constant power from a power transmitter. The development of modern technology for transmitting electric power over free space has been studied for several decades, but its use in a system has been mainly limited to low power, 1-2 Vdc output voltage at a transmission distance of few meters for which relatively less than 0.5 mW/cm2 is required (e.g., Radio frequency identification RFID). Most of the rectenna conversion efficiency research to date has concentrated in low GHz frequency range of 2.45 to 10 GHz, with some work at 35 GHz. However, for space application, atmospheric adsorbtion is irrelevant and higher frequency systems with smaller transmit and receive apertures may be appropriate. For high power, most of the work on rectennas has concentrated on optimizing the conversion efficiency of the microwave rectifier element; the highest power demonstrated was 35 kW of power over a distance of 1.5 km. The objective of this paper is to establish the manner in which a very large number of very low power microwave devices can be synchronized to provide a beam of microwaves that can be used to efficiently and safely transport a significant amount of power to a remote location where it can be converted to dc (or ac) power by a ``rectenna.'' The proposed system is based on spatial power combining of the outputs of a large number of devices synchronized by mutual injection locking. We have demonstrated at JPL that such power could be achieved by combining 25 sources in a configuration that allows for convenient steering of the resulting beam of microwaves. Retrodirective beam steering for microwave power transmission (the ability to accurately track a moving receiver) has been demonstrated at Texas A&M. It is proposed that the next step in development of this concept is a modest scale up from 25 elements to 435 followed by a further scale up using such 435 element arrays as subarrays for a still larger retrodirective system. Ultimately, transmit antenna sizes on the order of 100 meters are envisioned permitting transfer levels on the order of 30 kW to aerial vehicles up to 20 km.
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.
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.
International Nuclear Information System (INIS)
The kinetics and dynamics of several O + O2 isotope exchange reactions have been investigated on a recently determined accurate global O3 potential energy surface using a time-dependent wave packet method. The agreement between calculated and measured rate coefficients is significantly improved over previous work. More importantly, the experimentally observed negative temperature dependence of the rate coefficients is for the first time rigorously reproduced theoretically. This negative temperature dependence can be attributed to the absence in the new potential energy surface of a submerged “reef” structure, which was present in all previous potential energy surfaces. In addition, contributions of rotational excited states of the diatomic reactant further accentuate the negative temperature dependence
International Nuclear Information System (INIS)
Highlights: ? Surface tension and the Gibbs-Thomson coefficient are computed for Al-based alloys. ? Butler's scheme and ThermoCalc are used to compute the thermophysical properties. ? Predictive cell/dendrite growth models depend on accurate thermophysical properties. ? Mechanical properties can be related to the microstructural cell/dendrite spacing. - Abstract: In this paper, a solution for Butler's formulation is presented permitting the surface tension and the Gibbs-Thomson coefficient of Al-based binary alloys to be determined. The importance of Gibbs-Thomson coefficient for binary alloys is related to the reliability of predictions furnished by predictive cellular and dendritic growth models and of numerical computations of solidification thermal variables, which will be strongly dependent on the thermophysical properties assumed for the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled to a specific interface of a computational thermodynamics software in order to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Fe, Al-Ni, Al-Cu and Al-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.
International Nuclear Information System (INIS)
A new method was discussed to define parameters indicating the extent of colloid deposition onto solid surface, which are important to evaluate the effects of colloid filtration on radionuclide transport in a radioactive waste repository. The deposition coefficients for colloid transport in porous media were determined by the observation of colloid deposition in a parallel-plate channel. The values that were independently derived did not exceed twice as much as deposition coefficients determined by ordinary method, in which the colloid transport model was fitted to colloid breakthrough data obtained from column experiments. (author)
DEFF Research Database (Denmark)
Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Hvilsted, Søren
2010-01-01
Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) has been exploited to hydrophilize PEEK. The ketone groups on the PEEK surface were reduced to hydroxyl groups which were converted to bromoisobutyrate initiating sites for SI-ATRP. The modification steps were followed by contact angle measurements and XPS. Moreover, ATR FTIR has been used to confirm the formation of initiating groups. Grafting of PEGMA from PEEK was performed in aqueous solution. The presence of the PPEGMA grafts ...
Hydromagnetic flow and heat transfer over a continuous, moving, porous, flat surface
International Nuclear Information System (INIS)
Exact solutions for hydromagnetic boundary-layer flow and heat transfer over a continuous, moving, flat surface with uniform suction and internal heat generation/absorption are obtained. Flow of this type represents a new class of boundary-layer problems, with solutions substantially different from those for boundary-layer flow on a flat surface of finite length. These solutions are even exact solutions of the complete Navier-Stokes equations and the energy equation. (Auth.)
Adhesion and material transfer between contacting Al and TiN surfaces from first principles
Feldbauer, G.; Wolloch, M.; Bedolla, P. O.; Mohn, P.; Redinger, J.; Vernes, A.
2015-04-01
A series of density functional theory (DFT) simulations was performed to investigate the approach, contact, and subsequent separation of two atomically flat surfaces consisting of different materials. Aluminum (Al) and titanium nitride (TiN) slabs were chosen as a model system representing a metal-ceramic interface and the interaction between soft and hard materials. The approach and separation were simulated by moving one slab in discrete steps normal to the surfaces allowing for electronic and atomic relaxations after each step. Various configurations were analyzed by considering (001), (011), and (111) surfaces as well as several lateral arrangements of these surfaces at the interface. Several tests were conducted on the computational setup, for example, by changing the system size or using different approximations for the exchange correlation functional. The performed simulations revealed the influences of these aspects on adhesion, equilibrium distance, and material transfer. These interfacial properties depend sensitively on the chosen configuration due to distinct bond situations. Material transfer, in particular, was observed if the absolute value of the adhesion energy for a given configuration is larger than the energy cost to remove surface layers. This result was found to be independent of the employed exchange correlation functional. Furthermore, it was shown that a simple comparison of the surface energies of the slabs is not sufficient to predict the occurrence of material transfer.
Energy Technology Data Exchange (ETDEWEB)
Krukowski, Stanis?aw, E-mail: stach@unipress.waw.pl [Institute of High Pressure Physics, Polish Academy of Sciences, Soko?owska 29/37, 01-142 Warsaw (Poland); Interdisciplinary Centre for Modelling, University of Warsaw, Pawi?skiego 5a, 02-106 Warsaw (Poland); Kempisty, Pawe?; Strak, Pawe?; Sakowski, Konrad [Institute of High Pressure Physics, Polish Academy of Sciences, Soko?owska 29/37, 01-142 Warsaw (Poland)
2014-01-28
It is shown that charge transfer, the process analogous to formation of semiconductor p-n junction, contributes significantly to adsorption energy at semiconductor surfaces. For the processes without the charge transfer, such as molecular adsorption of closed shell systems, the adsorption energy is determined by the bonding only. In the case involving charge transfer, such as open shell systems like metal atoms or the dissociating molecules, the energy attains different value for the Fermi level differently pinned. The Density Functional Theory (DFT) simulation of species adsorption at different surfaces, such as SiC(0001) or GaN(0001) confirms these predictions: the molecular adsorption is independent on the coverage, while the dissociative process adsorption energy varies by several electronvolts.
DEFF Research Database (Denmark)
Source: US2012184029A The present invention relates to preparation of a polymer coating comprising or consisting of polymer chains comprising or consisting of units of 2-methoxyethyl acrylate synthesized by Surface-Initiated Atom Transfer Radical Polymerization (SI ATRP) such as ARGET SI ATRP or AGET SI ATRP and uses of said polymer coating.
Vectorial doping-promoting charge transfer in anatase TiO2 {0 0 1} surface
International Nuclear Information System (INIS)
Graphical abstract: The exhibited vectorial doping of C and F atoms in TiO2 {0 0 1} surface makes a great contribution to the enhanced photocatalytic activity of TiO2. - Highlights: • The impurity C and F atoms prefer to substitute for the outmost O atoms in TiO2 {0 0 1} surface. • The vectorial doping of C and F atoms produces a conducting layer in TiO2 {0 0 1} surface. • The formed conducting layer in TiO2 {0 0 1} surface can promote the charge transfer. - Abstract: Doping-induced visible-light adsorption is often considered as the main reason for the enhanced photocatalytic activity of TiO2. However, this work provides a new understanding on the effect of doping on the photocatalytic activity of TiO2. The investigation on the C–F codoped anatase TiO2 {0 0 1} surface reveals that the impurity C and F atoms prefer to substitute for the outmost O atoms in the TiO2 {0 0 1} surface rather than those in the bulk TiO2. The exhibited vectorial doping of C and F atoms in TiO2 {0 0 1} surface produces a conducting layer with low electric resistance, which can promote the charge transfer in the photocatalytic reaction. This effectively inhibits the undesirable bulk recombination of photogenerated electron and hole. Hence, the optimized charge transfer in the C–F codoped TiO2 {0 0 1} surface makes a great contribution to the enhanced photocatalytic activity of TiO2. Further, the surface doping treatment is a potential method to improve the performance of photocatalyst
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 7.2 h(-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 13.3 h(-1) and 65.5 h(-1). Similar kinetic was observed in cultures performed at KLa equal to 65.5 h(-1) and 106.2 h(-1). The highest toxins productivity of 96.1 mg L(-1) (h)-1 was obtained in the 9% CMB culture medium for KLa of 102 h(-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
Endo, Satoru; Kajimoto, Tsuyoshi; Shizuma, Kiyoshi
2013-02-01
The transfer coefficient (TF) from soil to rice plants of (134)Cs and (137)Cs 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 (134)Cs and (137)Cs radioactivity at 5-cm intervals. (134)Cs and (137)Cs 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 (134)Cs and (137)Cs 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 (40)K 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. PMID:23103577
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.
Dissolved organic matter in sea spray: a transfer study from marine surface water to aerosols
Schmitt-Kopplin, P.; Liger-Belair, G.; Koch, B. P.; Flerus, R.; Kattner, G.; Harir, M.; Kanawati, B.; Lucio, M.; Tziotis, D.; Hertkorn, N.; Gebefügi, I.
2012-04-01
Atmospheric aerosols impose direct and indirect effects on the climate system, for example, by absorption of radiation in relation to cloud droplets size, on chemical and organic composition and cloud dynamics. The first step in the formation of Organic primary aerosols, i.e. the transfer of dissolved organic matter from the marine surface into the atmosphere, was studied. We present a molecular level description of this phenomenon using the high resolution analytical tools of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and nuclear magnetic resonance spectroscopy (NMR). Our experiments confirm the chemoselective 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 compounds enriched in the aerosol phase were CHO and CHOS molecular series, smaller molecules of higher aliphaticity and lower oxygen content, and typical surfactants. A non-targeted metabolomics analysis demonstrated that many of these molecules corresponded to homologous series of oxo-, hydroxy-, 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 sea spray production leaves a selective biological signature of the surface water in the corresponding aerosol that may be transported into higher altitudes up to the lower atmosphere, thus contributing to the formation of secondary organic aerosol on a global scale or transported laterally with possible deposition in the context of global biogeocycling.
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.
Dissolved organic matter in sea spray: a transfer study from marine surface water to aerosols
Directory of Open Access Journals (Sweden)
P. Schmitt-Kopplin
2012-04-01
Full Text Available Atmospheric aerosols impose direct and indirect effects on the climate system, for example, by absorption of radiation in relation to cloud droplets size, on chemical and organic composition and cloud dynamics. The first step in the formation of Organic primary aerosols, i.e. the transfer of dissolved organic matter from the marine surface into the atmosphere, was studied. We present a molecular level description of this phenomenon using the high resolution analytical tools of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS and nuclear magnetic resonance spectroscopy (NMR. Our experiments confirm the chemoselective 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 compounds enriched in the aerosol phase were CHO and CHOS molecular series, smaller molecules of higher aliphaticity and lower oxygen content, and typical surfactants. A non-targeted metabolomics analysis demonstrated that many of these molecules corresponded to homologous series of oxo-, hydroxy-, 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 sea spray production leaves a selective biological signature of the surface water in the corresponding aerosol that may be transported into higher altitudes up to the lower atmosphere, thus contributing to the formation of secondary organic aerosol on a global scale or transported laterally with possible deposition in the context of global biogeocycling.
Analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings.
Wang, Quan-bao; Qiu, Ye; Zhao, Hai-tao; Chen, Ji-an; Wang, Yue-ying; Fan, Zhen-min
2012-06-20
A theoretical analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings (FBGs) subjected to uniform axial stress is presented. The proposed six-layer structure consists of optical fiber, protective coating, adhesive layer, substrate layer, outer adhesive layer, and host material, which is different from the four-layer case of common acknowledgement. A theoretical formula of strain transfer rate from host material to optical fiber is established to provide an accurate theoretical prediction. On the basis of the theoretical analysis, influence parameters of the middle layers that affect the average strain transfer rate of the six-layer surface-bonded FBG are discussed. After the parametric study, a selection scheme of sensor parameters for numerical validation, which makes the average strain transfer rate approach unity, is determined. Good agreement is observed between numerical results and theoretical predictions. In the end, the six-layer model is extended to the general situation of multiple substrate layers, which lays a theoretical groundwork for the research and design of surface-bonded FBGs with substrate layers in the future. PMID:22722290
Time-dependent picture of the charge-transfer contributions to surface enhanced Raman spectroscopy
Lombardi, John R.; Birke, Ronald L.
2007-06-01
We reexamine the Herzberg-Teller theory of charge-transfer contributions to the theory of surface enhanced Raman scattering (SERS). In previous work, the Kramers-Heisenberg-Dirac framework was utilized to explain many of the observed features in SERS. However, recent experimental and theoretical developments suggest that we revise the theory to take advantage of the time-dependent picture of Raman scattering. Results are obtained for molecular adsorption on nanoparticles in both the strong confinement limit and the weak confinement limit. We show that the Herzberg-Teller contributions to the charge-transfer effect in SERS display a resonance at the molecule-to-metal or metal-to-molecule transition while retaining the selection rules associated with normal Raman spectroscopy (i.e., harmonic oscillator, as opposed to Franck-Condon overlaps). The charge-transfer contribution to the enhancement factor scales as ?-4, where ? is the homogeneous linewidth of the charge-transfer transition, and thus is extremely sensitive to the magnitude of this parameter. We show that the Herzberg-Teller coupling term may be associated with the polaron-coupling constant of the surface phonon-electron interaction. A time-dependent expression for the Raman amplitude is developed, and we discuss the implications of these results for both metal and semiconductor nanoparticle surfaces.
Comparison of Predicted and Measured Turbine Vane Rough Surface Heat Transfer
Boyle, R. J.; Spuckler, C. M.; Lucci, B. L.
2000-01-01
The proposed paper compares predicted turbine vane heat transfer for a rough surface over a wide range of test conditions with experimental data. Predictions were made for the entire vane surface. However, measurements were made only over the suction surface of the vane, and the leading edge region of the pressure surface. Comparisons are shown for a wide range of test conditions. Inlet pressures varied between 3 and 15 psia, and exit Mach numbers ranged between 0.3 and 0.9. Thus, while a single roughened vane was used for the tests, the effective rougness,(k(sup +)), varied by more than a factor of ten. Results were obtained for freestream turbulence levels of 1 and 10%. Heat transfer predictions were obtained using the Navier-Stokes computer code RVCQ3D. Two turbulence models, suitable for rough surface analysis, are incorporated in this code. The Cebeci-Chang roughness model is part of the algebraic turbulence model. The k-omega turbulence model accounts for the effect of roughness in the application of the boundary condition. Roughness causes turbulent flow over the vane surface. Even after accounting for transition, surface roughness significantly increased heat transfer compared to a smooth surface. The k-omega results agreed better with the data than the Cebeci-Chang model. However, the low Reynolds number k-omega model did not accurately account for roughness when the freestream turbulence level was low. The high Reynolds number version of this model was more suitable when the freestream turbulence was low.
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.
Surface plasmons mediated energy transfer from a semiconductor quantum well to an organic overlayer
Kawka, Sebastien
2013-01-01
We consider the resonant energy transfer from a two-dimensional Wannier exciton (donor) to a Frenkel exciton of a molecular crystal overlayer (acceptor) when the active medias are separated by a metallic layer, possibly an electrode. We characterize the effect of the surface plasmon on this process. Using realistic values of material parameters, we show that it is possible to change the transfer rate within typically a factor of 5 (up to 44 according to geometrical configuration). We then take into account the quenching of the organic luminescence due to the proximity with the metal. This latter is significant and affect negatively the total internal efficiency that we discuss for different geometries.
International Nuclear Information System (INIS)
The surface tension ?, grain boundary energy ?sub(R) and diffusion coefficient D at 1470C were determined from the creep behaviour of thin In wires having a bamboo structure. The following values were found. ? = 674 +- 74 dyn/cm; ?sub(R) = 258 +- 36 dyn/cm; D = 3.1 +- 0.4 x 1010 cm2/s. Creep is governed by the Nabarro-Herring mechanism. (orig.)
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.
Hamzah, Esah; Ourdjini, Ali; Ali, Mubarak; Akhter, Parvez; Hj. Mohd Toff, Mohd Radzi; Abdul Hamid, Mansor
In the present study, the effect of various N2 gas flow rates on friction coefficient and surface roughness of TiN-coated D2 tool steel was examined by a commercially available cathodic arc physical vapor deposition (CAPVD) technique. A Pin-on-Disc test was carried out to study the Coefficient of friction (COF) versus sliding distance. A surface roughness tester measured the surface roughness parameters. The minimum values for the COF and surface roughness were recorded at a N2 gas flow rate of 200 sccm. The increase in the COF and surface roughness at a N2 gas flow rate of 100 sccm was mainly attributed to an increase in both size and number of titanium particles, whereas the increase at 300 sccm was attributed to a larger number of growth defects generated during the coating process. These ideas make it possible to optimize the coating properties as a function of N2 gas flow rate for specific applications, e.g. cutting tools for automobiles, aircraft, and various mechanical parts.
Experimental Study for Heat Transfer Enhancement Due To Surface Roughness at Laminar Flow
Directory of Open Access Journals (Sweden)
Raju R.Yenare
2014-03-01
Full Text Available An investigation was conducted to determine whether dimples on a heat sink fin can increase heat transfer for laminar airflows. This was accomplished by performing experimental studies using two different types of dimples: 1 circular (spherical dimples, and 2 oval (elliptical dimples. Dimples were placed on both sides of a aluminium plate with a relative pitch of S/D=1.21 and relative depth of ?/D=0.16 (e.g., circular dimples. For oval dimples, similar ratios with the same total depth and circular-edge-to-edge distance as the circular dimples were used. For those configurations the average heat transfer coefficient, pressure drop, thermal performance and Nusselt number ratio were determined experimentally. For circular and oval dimples, heat transfer enhancements (relative to a flat plate were observed for Reynolds number range from 600 to 2000 (Reynolds number based on channel height. Also the results are validated analytically for Nusselt number and friction factor for plain vertical plate.
Directory of Open Access Journals (Sweden)
Isaac T. Yonemoto
2015-01-01
Full Text Available Photobiological hydrogen production is an attractive, carbon-neutral means to convert solar energy to hydrogen. We build on previous research improving the Alteromonas macleodii “Deep Ecotype” [NiFe] hydrogenase, and report progress towards creating an artificial electron transfer pathway to supply the hydrogenase with electrons necessary for hydrogen production. Ferredoxin is the first soluble electron transfer mediator to receive high-energy electrons from photosystem I, and bears an electron with sufficient potential to efficiently reduce protons. Thus, we engineered a hydrogenase-ferredoxin fusion that also contained several other modifications. In addition to the C-terminal ferredoxin fusion, we truncated the C-terminus of the hydrogenase small subunit, identified as the available terminus closer to the electron transfer region. We also neutralized an anionic patch surrounding the interface Fe-S cluster to improve transfer kinetics with the negatively charged ferredoxin. Initial screening showed the enzyme tolerated both truncation and charge neutralization on the small subunit ferredoxin-binding face. While the enzyme activity was relatively unchanged using the substrate methyl viologen, we observed a marked improvement from both the ferredoxin fusion and surface modification using only dithionite as an electron donor. Combining ferredoxin fusion and surface charge modification showed progressively improved activity in an in vitro assay with purified enzyme.
Liuzzi, G.; Masiello, G.; Serio, C.; Blasi, M. G.; Venafra, S.
2015-09-01
This paper describes the theoretical aspects of a fast scheme for the physical retrieval of surface temperature and emissivity from SEVIRI data, their implementation and some sample results obtained. The scheme is based on a Kalman Filter approach, which effectively exploits the temporal continuity in the observations of the geostationary Meteosat Second Generation (MSG) platform, on which SEVIRI (Spinning Enhanced Visible and InfraRed Imager) operates. Such scheme embodies in its core a physical retrieval algorithm, which employs an hyper fast radiative transfer code highly customized for this retrieval task. Radiative transfer and its customizations are described in detail. Fastness, accuracy and stability of the code are fully documented for a variety of surface features, showing a peculiar application to the massive Greek forest fires in August 2007.
DEFF Research Database (Denmark)
Chernyy, Sergey; Lillethorup, Mie; Ceccato, Marcel; Ron, Troels; Hinge, Mogens; Kingshott, Peter; Besenbacher, Flemming; Pedersen, Steen Uttrup; Daasbjerg, Kim; Iruthayaraj, Joseph
2011-01-01
This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying different parameters such as the bromine content of the initiator layer, polarity of reaction medium, ligand type (L), and the ratio of activator (Cu(I)) to deactivator (Cu(II)) in order to ascertain the c...
Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Eskimergen, Ru?ya; Bukrinsky, Jens T.; Hvilsted, Søren
2012-01-01
Grafting of poly(ethylene glycol)methacrylate (PEGMA) and N,N-dimethylacrylamide (DMAAm) from UV-initiator modified polypropylene (PP) was performed by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP). The modification and hydrophilization of the PP substrates were confirmed with Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) spectroscopy and Water Contact Angle (WCA) measurements. Confocal fluorescence microscopy of modified and unmodified substrates imm...
Influence of localised surface plasmons on energy transfer between quantum dots
Bradley , Louise; Gerard, Valerie; GOUNKO, IOURI; LUNZ, MANUELA
2010-01-01
The effects of surface plasmons (SPs) on Förster resonant energy transfer (FRET) in colloidal quantum dot (QD) structures have been investigated. CdTe QDs of two different sizes acted as donors and acceptors in a mixed donor-acceptor monolayer on top of a gold nanoparticle layer and an acceptor-gold-donor sandwich structure. The structures were prepared by a layer-by-layer technique and characterized by absorption and photoluminescence (PL) spectroscopy as well as time-resolved PL measurement...
Thermosensitive Nanocables Prepared by Surface-Initiated Atom Transfer Radical Polymerization
Wei Qingshan; Zhou Wenbo; Ji Jian; Shen Jiacong
2008-01-01
Abstract Thermosensitive nanocables consisting of Au nanowire cores and poly(N-isopropylacrylamide) sheaths (denoted as Au/PNIPAAm) were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP). The formation of PNIPAAm sheath was verified by Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance (1H NMR) spectroscopy. Transmission electron microscope (TEM) results confirmed the core/shell structure of nanohybrids. The thickness and density of PNIPAAm...
Long Range Nanoparticle Surface Energy Transfer Ruler for Monitoring Photothermal Therapy Response
Singh, Anant K.; Lu, Wentong; Senapati, Dulal; Khan, Sadia Afrin; Fan, Zhen; Senapati, Tapas; Demeritte, Teresa; Beqa, Lule; Ray, Paresh Chandra
2011-01-01
Gold nanotechnology driven recent approach opens up a new possibility for the destruction of cancer cells through photothermal therapy. Ultimately, photothermal therapy may enter into clinical therapy and as a result, there is an urgent need for techniques to monitor on time tumor response to therapy. Driven by the need, in this article we report nanoparticle surface energy transfer (NSET) approach to monitor photothermal therapy process by measuring the simple fluorescence intensity change. ...
DEFF Research Database (Denmark)
Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars; Vigild, Martin Etchells; Ndoni, Sokol
2010-01-01
Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based oil nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide f...
Pixel level optical-transfer-function design based on the surface-wave-interferometry aperture
Zheng, Guoan; WANG, YINGMIN; Yang, Changhuei
2010-01-01
The design of optical transfer function (OTF) is of significant importance for optical information processing in various imaging and vision systems. Typically, OTF design relies on sophisticated bulk optical arrangement in the light path of the optical systems. In this letter, we demonstrate a surface-wave-interferometry aperture (SWIA) that can be directly incorporated onto optical sensors to accomplish OTF design on the pixel level. The whole aperture design is based on the bull’s eye struc...
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)
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.
Planform structure and heat transfer in turbulent free convection over horizontal surfaces
Theerthan, S. Ananda; Arakeri, Jaywant H.
2000-04-01
This paper deals with turbulent free convection in a horizontal fluid layer above a heated surface. Experiments have been carried out on a heated surface to obtain and analyze the planform structure and the heat transfer under different conditions. Water is the working fluid and the range of flux Rayleigh numbers (Ra) covered is 3×107-2×1010. The different conditions correspond to Rayleigh-Bénard convection, convection with either the top water surface open to atmosphere or covered with an insulating plate, and with an imposed external flow on the heated boundary. Without the external flow the planform is one of randomly oriented line plumes. At large Rayleigh number Ra and small aspect ratio (AR), these line plumes seem to align along the diagonal, presumably due to a large scale flow. The side views show inclined dyelines, again indicating a large scale flow. When the external flow is imposed, the line plumes clearly align in the direction of external flow. The nondimensional average plume spacing, Ra?1/3, varies between 40 and 90. The heat transfer rate, for all the experiments conducted, represented as Ra?T-1/3, where ?T is the conduction layer thickness, varies only between 0.1-0.2, showing that in turbulent convection the heat transfer rates are similar under the different conditions.
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
Directory of Open Access Journals (Sweden)
I.I. Balogun
2012-01-01
Full Text Available Heavy metals have high significance among the inorganic contaminants of surface water (e.g., ponds and streams due to their non-degradable nature in heighten injurious biological effect. For this reason, therefore, this study examined the influence of the land-uses on the performance of the selected heavy metals using z-score and coefficient of variation. In order to achieve the aim of this study, thirty surface ponds water were sampled across four land uses in Akoko Northeast LGA of Ondo State, Nigeria. The sampled water were assessed for four heavy metals and evaluated using the Z-score and coefficient of variation. The heavy metals are zinc (Zn, iron (Fe, manganese (Mn and copper (Cu while the land uses comprise of built-up areas, cultivated lands, vegetation and crop plantation. Observed heavy metals results were converted to standardized Z-scores (z to facilitate objective comparisons and enablement of performance among each parameter in the ponds across the land uses. The predefined water quality result variations were objectively subjected to coefficient of variation (CV to confirm the level of parameters comparability. Thus, the z-score results of heavy metals identified strong remarkable spatial dependency when p>0.01 or weak remarkable spatial dependency when p50%. In conclusion, the study exhibited spatial variation in concentrations of the four heavy metals as a result of different land uses characteristic.
Xiang, Du; Han, Cheng; Wu, Jing; Zhong, Shu; Liu, Yiyang; Lin, Jiadan; Zhang, Xue-Ao; Ping Hu, Wen; Özyilmaz, Barbaros; Neto, A H Castro; Wee, Andrew Thye Shen; Chen, Wei
2015-01-01
Black phosphorus, a fast emerging two-dimensional material, has been configured as field effect transistors, showing a hole-transport-dominated ambipolar characteristic. Here we report an effective modulation on ambipolar characteristics of few-layer black phosphorus transistors through in situ surface functionalization with caesium carbonate (Cs2CO3) and molybdenum trioxide (MoO3), respectively. Cs2CO3 is found to strongly electron dope black phosphorus. The electron mobility of black phosphorus is significantly enhanced to ~27?cm(2)?V(-1)?s(-1) after 10?nm Cs2CO3 modification, indicating a greatly improved electron-transport behaviour. In contrast, MoO3 decoration demonstrates a giant hole-doping effect. In situ photoelectron spectroscopy characterization reveals significant surface charge transfer occurring at the dopants/black phosphorus interfaces. Moreover, the surface-doped black phosphorus devices exhibit a largely enhanced photodetection behaviour. Our findings coupled with the tunable nature of the surface transfer doping scheme ensure black phosphorus as a promising candidate for further complementary logic electronics. PMID:25761440
Mixed-valence correlations in charge-transferring atom-surface collisions
Pamperin, M.; Bronold, F. X.; Fehske, H.
2015-10-01
Motivated by experimental evidence (He and Yarmoff 2010 Phys. Rev. Lett. 105 176806) for a mixed-valence state to occur in the neutralization of strontium ions on gold surfaces we analyze this type of charge-transferring atom-surface collision from a many-body theoretical point of view using quantum-kinetic equations together with a pseudo-particle representation for the electronic configurations of the atomic projectile. Particular attention is paid to the temperature dependence of the neutralization probability which—experimentally—seems to signal mixed-valence-type correlations affecting the charge-transfer between the gold surface and the strontium projectile. We also investigate the neutralization of magnesium ions on a gold surface which shows no evidence for a mixed-valence state. Whereas for magnesium excellent agreement between theory and experiment could be obtained, for strontium we could not reproduce the experimental data. Our results indicate mixed-valence correlations to be in principle present, but for the model mimicking most closely the experimental situation they are not strong enough to affect the neutralization process quantitatively.
International Nuclear Information System (INIS)
The echo signal energy is directly affected by the incident sound beam eccentricity or angle for thick-walled pipes inner longitudinal cracks detection. A method for analyzing the relationship between echo signal energy between the values of incident eccentricity is brought forward, which can be used to estimate echo signal energy when testing inside wall longitudinal crack of pipe, using mode-transformed compression wave adaptation of shear wave with water-immersion method, by making a two-dimension integration of “energy coefficient” in both circumferential and axial directions. The calculation model is founded for cylinder sound beam case, in which the refraction and reflection energy coefficients of different rays in the whole sound beam are considered different. The echo signal energy is calculated for a particular cylinder sound beam testing different pipes: a beam with a diameter of 0.5 inch (12.7mm) testing a ?279.4mm pipe and a ?79.4mm one. As a comparison, both the results of two-dimension integration and one-dimension (circumferential direction) integration are listed, and only the former agrees well with experimental results. The estimation method proves to be valid and shows that the usual method of simplifying the sound beam as a single ray for estimating echo signal energy and choosing optimal incident eccentricity is not so appropriate
Energy Technology Data Exchange (ETDEWEB)
Zhou, Shiyuan, E-mail: redaple@bit.edu.cn; Sun, Haoyu, E-mail: redaple@bit.edu.cn; Xu, Chunguang, E-mail: redaple@bit.edu.cn; Cao, Xiandong, E-mail: redaple@bit.edu.cn; Cui, Liming, E-mail: redaple@bit.edu.cn; Xiao, Dingguo, E-mail: redaple@bit.edu.cn [School of Mechanical Engineering, Beijing Institute of Technology, Beijing, China NO.5 Zhongguancun South Street, Haidian District, Beijing 100081 (China)
2015-03-31
The echo signal energy is directly affected by the incident sound beam eccentricity or angle for thick-walled pipes inner longitudinal cracks detection. A method for analyzing the relationship between echo signal energy between the values of incident eccentricity is brought forward, which can be used to estimate echo signal energy when testing inside wall longitudinal crack of pipe, using mode-transformed compression wave adaptation of shear wave with water-immersion method, by making a two-dimension integration of “energy coefficient” in both circumferential and axial directions. The calculation model is founded for cylinder sound beam case, in which the refraction and reflection energy coefficients of different rays in the whole sound beam are considered different. The echo signal energy is calculated for a particular cylinder sound beam testing different pipes: a beam with a diameter of 0.5 inch (12.7mm) testing a ?279.4mm pipe and a ?79.4mm one. As a comparison, both the results of two-dimension integration and one-dimension (circumferential direction) integration are listed, and only the former agrees well with experimental results. The estimation method proves to be valid and shows that the usual method of simplifying the sound beam as a single ray for estimating echo signal energy and choosing optimal incident eccentricity is not so appropriate.
DEFF Research Database (Denmark)
Mejlbro, Leif
1996-01-01
Fick's Second Law of Diffusion with time-dependent diffusioncoefficient and surface concentration is solved. Mimicking the classicalsolution, special time-dependent surface concentration functions areconsidered. These models are used in giving estimates of the lifetimeof the structure, when the concrete cover is given, as well as estimatesof the thickness of the concrete cover, when the expected lifetime is given.*Note: Book tilte: Durability of Concrete in Saline Environment
DEFF Research Database (Denmark)
Fristrup, Charlotte Juel; Jankova Atanasova, Katja
2010-01-01
Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) has been exploited to hydrophilize PEEK. The ketone groups on the PEEK surface were reduced to hydroxyl groups which were converted to bromoisobutyrate initiating sites for SI-ATRP. The modification steps were followed by contact angle measurements and XPS. Moreover, ATR FTIR has been used to confirm the formation of initiating groups. Grafting of PEGMA from PEEK was performed in aqueous solution. The presence of the PPEGMA grafts on PEEK was revealed by the thermograms from TGA whereas investigations with AFM rejected changes in the surface topography. Two possible applications arose from the hydrophilization of PEEK, metal deposition and protein repellency. The performed modification allowed for successful electroless deposition and good adhesion of nickel as well as copper.
Development of vacuum transfer techniques for tokamak in-situ surface analysis
International Nuclear Information System (INIS)
Plasma-wall interactions in tokamaks can in general be divided into atomic scale and grain size effects. The former class of effects include desorption, sputtering, recoil doping, and other related subjects, while the latter includes larger scale phenomena such as blistering, flaking, cracking and evaporation. These latter effects can be analysed using conventional metallurgical techniques. However, atomic scale processes require that the samples be maintained and analysed in a vacuum environment since monolayer changes can occur in minutes at 10-6 Pa (approximately=10-8 Torr). For this reason it is essential that surface analysis either be done in the tokamak during or briefly after a discharge or the surface of interest should be quickly transferred under vacuum to an ultra high vacuum (UHV) instrument for immediate analysis. However, under certain conditions it is desirable to transfer exposed samples or specially prepared substrates under vacuum for analysis in other UHV instruments not on-line. This requires the use of an ultra high vacuum transfer device (VTD). (Auth.)
International Nuclear Information System (INIS)
The prediction of heat transfer between corium pool and concrete basemat is of particular significance in the framework of the study of PWR's severe accident. Heat transfer directly governs the ablation velocity of concrete in case of molten core concrete interaction (MCCI) and, consequently, the time delay when the reactor cavity may fail. From a restricted hydrodynamic point of view, this issue is related to heat transfer between a heated bubbling pool and a porous wall with gas injection. Several experimental studies have been performed with simulant materials and many correlations have been provided to address this issue. The comparisons of the results of these correlations with the measurements and their extrapolation to reactor materials show that strong discrepancies between the results of these models are obtained which probably means that some phenomena are not well taken into account. The main purpose of this paper is to present an alternative heat transfer model which was originally developed for chemical engineering applications (bubble columns) by Deckwer. A part of this work is devoted to the presentation of this model, which is based on a surface renewal assumption. Comparison of the results of this model with available experimental data in different systems are presented and discussed. These comparisons clearly show that this model can be used to deal with the particular problem of MCCI. The analyses also lead to enrich the original model by taking into account the thermal resistance of the wall: a new formulation of the Deckwer's correlation is finally proposed
International Nuclear Information System (INIS)
Highlights: • We model electron dynamics across cyano alkanethiolates attached to gold cluster. • We present electron transfer time scales from TD-DFT and TD-CI based simulations. • Both DFT and CI methods qualitatively predict the trend in time scales. • TD-CI predicts the experimental relative time scale very accurately. - Abstract: We employ wavepacket simulations based on many-body time-dependent configuration interaction (TD-CI), and single active electron theories, to predict the ultrafast molecule/metal electron transfer time scales, in cyano alkanethiolates bonded to model gold clusters. The initial states represent two excited states where a valence electron is promoted to one of the two virtual ?? molecular orbitals localized on the cyanide fragment. The ratio of the two time scales indicate the efficiency of one charge transfer channel over the other. In both our one-and many-electron simulations, this ratio agree qualitatively with each other as well as with the previously reported experimental time scales (Blobner et al., 2012), measured for a macroscopic metal surface. We study the effect of cluster size and the description of electron correlation on the charge transfer process
Sabine absorption coefficients to random incidence absorption coefficients
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2014-01-01
Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a specimen and non-uniform intensity in the test chamber. In this study, several methods that convert Sabine absorption coefficients into random incidence absorption coefficients for porous absorbers are investigated. Two optimization-based conversion methods are suggested: the surface impedance estimation for locally reacting absorbers ...
Piston surface heat transfer during combustion in large marine diesel engines
DEFF Research Database (Denmark)
Jensen, Michael Vincent; Walther, Jens Honore
2010-01-01
In the design process of large marine diesel engines information on the maximum heat load on the piston surface experienced during the engine cycle is an important parameter. The peak heat load occurs during combustion when hot combustion products impinge on the piston surface. Although the maximum heat load is only present for a short time of the total engine cycle, it is a severe thermal load on the piston surface. At the same time, cooling of the piston crown is generally more complicated than cooling of the other components of the combustion chamber. This can occasionally cause problems with burning off piston surface material. In this work the peak heat load on the piston surface of large marine diesel engines during combustion was investigated. Measurements of the instantaneous surface temperature and surface heat flux on pistons in large marine engines are difficult due to expensive instrumentation and high engine running costs compared to automotive engines. Therefore the investigation in this work was carried out numerically with the use of a computational fluid dynamics (CFD) code. At the same time, numerical work on detailed in-cylinder wall heat transfer in engines has been quite limited. The numerical investigation focused on the simulation of a hot turbulent gas jet impinging on a wall under very high pressure, thus approximating the process of the actual impingement of hot combustion gasses on the piston surface during combustion. The surface heat flux at the wall was calculated under different conditions in the numerical setup in order to obtain information of the actual peak heat flux experienced at the piston in large marine diesel engines during combustion. The variation of physical parameters influencing the heat transfer during combustion included a variation of pressure, temperatures, jet velocity and jet turbulence intensity. The variation in heat flux predictions resulting from application of different turbulence models was also investigated by performing calculations with three different models: the V2F model, a k-? RNG model and a low-Re k-? model. The obtained results indicate peak heat fluxes in the order of 5-10 MW/m2 on the piston surface during the combustion phase of the engine cycle.
Radial and temporal variations in surface heat transfer during cryogen spray cooling
Energy Technology Data Exchange (ETDEWEB)
Franco, Walfre [Department of Mechanical Engineering, University of California, Riverside, CA 92521 (United States); Liu Jie [Department of Mechanical Engineering, University of California, Riverside, CA 92521 (United States); Wang Guoxiang [Department of Mechanical Engineering, University of Akron, Akron, OH 44325 (United States); Nelson, J Stuart [Beckman Laser Institute, University of California, Irvine, CA 92617 (United States); Aguilar, Guillermo [Department of Mechanical Engineering, University of California, Riverside, CA 92521 (United States)
2005-01-21
Cryogen spray cooling (CSC) is a heat extraction process that protects the epidermis from thermal damage during dermatologic laser surgery. The objective of the present work is to investigate radial and temporal variations in the heat transferred through the surface of a skin phantom during CSC. A fast-response thermal sensor is used to measure surface temperatures every 1 mm across a 16 mm diameter of the sprayed surface of the phantom. An analytical expression based on Fourier's law and Duhamel's theorem is used to compute surface heat fluxes from temperature measurements. Results show that radial and temporal variations of the boundary conditions have a strong influence on the homogeneity of heat extraction from the skin phantom. However, there is a subregion of uniform cooling whose size is time dependent. It is also observed that the surface heat flux undergoes a marked dynamic variation, with a maximum heat flux occurring at the centre of the sprayed surface early in the spurt followed by a quick decrease. The study shows that radial and temporal variations of boundary conditions must be taken into account and ideally controlled to guarantee uniform protection during CSC of human skin.
Radial and temporal variations in surface heat transfer during cryogen spray cooling
International Nuclear Information System (INIS)
Cryogen spray cooling (CSC) is a heat extraction process that protects the epidermis from thermal damage during dermatologic laser surgery. The objective of the present work is to investigate radial and temporal variations in the heat transferred through the surface of a skin phantom during CSC. A fast-response thermal sensor is used to measure surface temperatures every 1 mm across a 16 mm diameter of the sprayed surface of the phantom. An analytical expression based on Fourier's law and Duhamel's theorem is used to compute surface heat fluxes from temperature measurements. Results show that radial and temporal variations of the boundary conditions have a strong influence on the homogeneity of heat extraction from the skin phantom. However, there is a subregion of uniform cooling whose size is time dependent. It is also observed that the surface heat flux undergoes a marked dynamic variation, with a maximum heat flux occurring at the centre of the sprayed surface early in the spurt followed by a quick decrease. The study shows that radial and temporal variations of boundary conditions must be taken into account and ideally controlled to guarantee uniform protection during CSC of human skin
International Nuclear Information System (INIS)
We suggest and describe the use of a binary pseudo-random grating as a standard test surface for calibration of the modulation transfer function of microscopes. Results from calibration of a MicromapTM-570 interferometric microscope are presented.
Olaya, Astrid J.; Brevet, Pierre-François; Smirnov, Evgeny; Girault, Hubert H
2014-01-01
We present for the first time experimental measurements on the ultrafast population dynamics of the model surface-active dye methyl orange (MO) during its ion transfer across the water|1,2-dichloroethane interface by using time-resolved surface second harmonic generation (TR-SSHG). The interfacial dynamics reveals that the population of MO relaxes to the ground state within 160 fs without any significant contribution of the molecular reorientation. It is concluded that the MO transfer across ...
Meng, Qingyong; Chen, Jun; Zhang, Dong H.
2015-09-01
The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ? T ? 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.
Meng, Qingyong; Chen, Jun; Zhang, Dong H
2015-09-14
The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300?K ? T ? 1000?K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures. PMID:26373990
Vahabzadeh, A.; Fakour, M.; Ganji, D.; Rahimipetroudi, I.
2014-12-01
In this study, heat transfer and temperature distribution equations for logarithmic surface are investigated analytically and numerically. Employing the similarity variables, the governing differential equations have been reduced to ordinary ones and solved via Homotopy perturbation method (HPM), Variational iteration method (VIM), Adomian decomposition method (ADM). The influence of the some physical parameters such as rate of effectiveness of temperature on non-dimensional temperature profiles is considered. Also the fourth-order Runge-Kutta numerical method (NUM) is used for the validity of these analytical methods and excellent agreement are observed between the solutions obtained from HPM, VIM, ADM and numerical results.
DEFF Research Database (Denmark)
Fristrup, Charlotte Juel; Jankova Atanasova, Katja
2012-01-01
Grafting of poly(ethylene glycol)methacrylate (PEGMA) and N,N-dimethylacrylamide (DMAAm) from UV-initiator modified polypropylene (PP) was performed by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP). The modification and hydrophilization of the PP substrates were confirmed with Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) spectroscopy and Water Contact Angle (WCA) measurements. Confocal fluorescence microscopy of modified and unmodified substrates immersed in labelled insulin aspart showed superior repulsion of this protein for the poly(PEGMA) grafts, due to the achieved architecture.
A three dimensional radiative transfer method for optical remote sensing of vegetated land surfaces
Asrar, Ghassem; Myneni, Ranga B.; Choudhury, Bhaskar J.
1991-01-01
In the application of remote sensing at optical wavelengths to vegetated surfaces from satellite borne high resolution instruments, an understanding of the various physical mechanisms that contribute to the measured signal is important. A numerical method of solving the radiative transfer equation in three dimensions is reported. The reliability of coding and accuracy of the algorithm are evaluated by benchmarching. Parametrization of the methods and results of a simulation are presented. The method is tested with experimental data of canopy bidirectional reflectance factors. The effect of spatial heterogeneity on the relationship between the simple ratio and normalized vrs absorbed Photosynthetically Active Radiation (PAR) is discussed.
Scientific Electronic Library Online (English)
Jesús, Chávez-Galán; Rafael, Almanza; Neftalí, Rodríguez Cuevas.
2014-06-01
Full Text Available Alguns dos principais fatores que determinam a confiabilidade do projeto térmico de um edifício são as propriedades de transferência de calor e térmicas . Não há dados experimentais disponíveis na bibliografia internacional , relacionados com propriedades de transferência de calor por convecção para [...] os materiais de construção mais utilizados, portanto, pela primeira vez, algumas medidas relacionadas com propriedades de transferência de calor por convecção para os materiais de construção mais utilizados foram realizadas para ajudar a otimização do processo de design térmico de edifícios. Apresentamos dados experimentais sobre os coeficientes de transferência de calor convectivo para paredes de diversos materiais de construção na posição vertical e horizontal usando uma ferramenta poderosa como é um túnel de vento. Tijolo vermelho, tepetate (calcário), adobe e paredes de teste concretos de 0.46 x 0.56 x 0.06 m foram fabricados, bem como um protótipo de testes para montá-los e avaliar os seus coeficientes de transferência de calor por convecção. As medições foram realizadas no túnel de vento para o intervalo de um 2 - 10 m / s velocidade do vento. Os valores reportados oscilam entre 14 - 71 W/m²K dependendo do material da parede e de posição, bem como a velocidade do vento. O impacto do uso de dados experimentais contra dados recomendados pelos padrões mexicanos no projeto térmico de um edifício foi avaliada através de simulações com o software Energy - 10, estimando-se discrepância do consumo de energia para um edifício em quatro locais no México, com diversificada radiação solar climática e global condições. Abstract in spanish Algunos de los principales factores que determinan la fiabilidad del diseño térmico de un edificio son las propiedades térmicas y de transferencia de calor. Se llevaron a cabo algunas mediciones de propiedades de transferencia de calor para los materiales de construcción más comunes con el fin de ay [...] udar a la optimización del proceso de diseño térmico de los edificios. Se presentan los datos experimentales sobre los coeficientes de transferencia de calor por convección para las paredes de diversos materiales de construcción en la posición vertical y horizontal utilizando una herramienta potente como es un túnel de viento. Paredes de ladrillo rojo, tepetate (piedra caliza), adobe y concreto con tamaños de 0.46 x 0.56 x 0.06 m fueron fabricados, así como un prototipo de pruebas para montarlos y evaluar sus coeficientes de transferencia de calor por convección. Las mediciones se llevaron a cabo en el túnel de viento para un intervalo de 2 - 10 m / s de velocidad del viento. Los valores reportados oscilan entre 14 - 71 W/m²K según el material y la pared dependiendo de la posición, así como la velocidad del viento. El impacto del uso de los datos experimentales frente a los datos recomendados por las normas mexicanas en el diseño térmico de un edificio se evaluó a través de simulaciones con el software Energy -10; la estimación mostro una discrepancia en el consumo de energía para un edificio en cuatro lugares en México con diversas condiciones climáticas e irradiaciones solar global. Abstract in english Some of the main factors that determine the reliability of a building's thermal design are the thermal and heat transfer properties. Some measurements were carried out to help the optimization of the thermal design process of buildings. We present experimental data on convective heat transfer coeffi [...] cients for walls of diverse building materials in vertical and horizontal position using a powerful tool as it is a wind tunnel. Red brick, tepetate (limestone), adobe and concrete test walls of 0.46 x 0.56 x 0.06 m were manufactured, as well as a testing prototype to mount them and evaluate their convective heat transfer coefficients. Measurements were carried out at the wind-tunnel for a 2 - 10 m/s wind velocity interval. Reported values fluctuate between 14 - 71 W/m²K depending on mate
Energy Technology Data Exchange (ETDEWEB)
Barber, Samuel K.; Anderson, Erik D.; Cambie, Rossana; McKinney, Wayne R.; Takacs, Peter Z.; Stover, John C.; Voronov, Dmitriy L.; Yashchuk, Valeriy V.
2009-09-11
A technique for precise measurement of the modulation transfer function (MTF), suitable for characterization of a broad class of surface profilometers, is investigated in detail. The technique suggested in [Proc. SPIE 7077-7, (2007), Opt. Eng. 47(7), 073602-1-5 (2008)]is based on use of binary pseudo-random (BPR) gratings and arrays as standard MTF test surfaces. Unlike most conventional test surfaces, BPR gratings and arrays possess white-noise-like inherent power spectral densities (PSD), allowing the direct determination of the one- and two-dimensional MTF, respectively, with a sensitivity uniform over the entire spatial frequency range of a profiler. In the cited work, a one dimensional realization of the suggested method based on use of BPR gratings has been demonstrated. Here, a high-confidence of the MTF calibration technique is demonstrated via cross comparison measurements of a number of two dimensional BPR arrays using two different interferometric microscopes and a scatterometer. We also present the results of application of the experimentally determined MTF correction to the measurement taken with the MicromapTM-570 interferometric microscope of the surface roughness of a super-polished test mirror. In this particular case, without accounting for the instrumental MTF, the surface rms roughness over half of the instrumental spatial frequency bandwidth would be underestimated by a factor of approximately 1.4.