Prediction of strongly-heated internal gas flows
International Nuclear Information System (INIS)
McEligot, D.M.; Shehata, A.M.; Kunugi, Tomoaki
1997-01-01
The purposes of the present article are to remind practitioners why the usual textbook approaches may not be appropriate for treating gas flows heated from the surface with large heat fluxes and to review the successes of some recent applications of turbulence models to this case. Simulations from various turbulence models have been assessed by comparison to the measurements of internal mean velocity and temperature distributions by Shehata for turbulent, laminarizing and intermediate flows with significant gas property variation. Of about fifteen models considered, five were judged to provide adequate predictions
Heat transfer of liquid-metal magnetohydrodynamic flow with internal heat generation
International Nuclear Information System (INIS)
Kumamaru, Hiroshige; Kurita, Kazuhisa; Kodama, Satoshi
2000-01-01
Numerical calculations on heat transfer of a magnetohydrodynamic (MHD) flow with internal heat generation in a rectangular channel have been performed for the cases of very-large Hartmann numbers, finite wall conductivities and small aspect ratio (i.e. small length ratios of the channel side perpendicular to the applied magnetic field and the side parallel to the field), simulating typical conditions for a fusion-reactor blanket. The Nusselt numbers of the MHD flow in rectangular channels with aspect ratios of 1/10 to 1/40 for Hartmann numbers of ∼5 x 10 5 become ∼10 times higher than those for the corresponding flow under no magnetic field. The Nusselt number becomes higher as the internal heat generation rate increases as far as the heat generation rates in a fusion reactor blanket are considered. (author)
Analysis of natural convection heat transfer and flows in internally heated stratified liquid pools
International Nuclear Information System (INIS)
Gubaidullin, A.A. Jr.; Dinh, T.N.; Sehgal, B.R.
1999-01-01
In this paper, natural convection flows and heat transfer in a liquid pool, with two superposed immiscible fluid layers, are analyzed. The objective of the study is to examine the effect of interfacial hydrodynamics and to develop a method which enables energy splitting to be evaluated in a stratified liquid pool. The thermal convection, with and without an internal heat source, in a rectangular cavity with different pairs of fluids was numerically simulated by a CFD code FLOW-3D. It was found that the code performs very well for prediction of heat transfer coefficients for different conditions. The hydrodynamic coupling between immiscible layers was found to have minor, if any, impact on the natural convection heat transfer for the conditions examined. Calculated results were used to develop, and validate, a new correlation for energy splitting and for heat transfer in stratified liquid pools
Study on Gas-liquid Falling Film Flow in Internal Heat Integrated Distillation Column
Liu, Chong
2017-10-01
Gas-liquid internally heat integrated distillation column falling film flow with nonlinear characteristics, study on gas liquid falling film flow regulation control law, can reduce emissions of the distillation column, and it can improve the quality of products. According to the distribution of gas-liquid mass balance internally heat integrated distillation column independent region, distribution model of heat transfer coefficient of building internal heat integrated distillation tower is obtained liquid distillation falling film flow in the saturated vapour pressure of liquid water balance, using heat transfer equation and energy equation to balance the relationship between the circulating iterative gas-liquid falling film flow area, flow parameter information, at a given temperature, pressure conditions, gas-liquid flow falling film theory makes the optimal parameters to achieve the best fitting value with the measured values. The results show that the geometric gas-liquid internally heat integrated distillation column falling film flow heat exchange area and import column thermostat, the average temperature has significant. The positive correlation between the heat exchanger tube entrance due to temperature difference between inside and outside, the heat flux is larger, with the increase of internal heat integrated distillation column temperature, the slope decreases its temperature rise, which accurately describes the internal gas-liquid heat integrated distillation tower falling film flow regularity, take appropriate measures to promote the enhancement of heat transfer. It can enhance the overall efficiency of the heat exchanger.
Numerical simulation of magnetohydrodynamic (MHD) flow with internal heat generation
International Nuclear Information System (INIS)
Bokade, Vipin; Bhandarkar, U.V.; Bodi, Kowsik
2016-01-01
A strong magnetic field is used to confine the plasma in a fusion reactor. This magnetic field also affects the flow of Lead-Lithium (breeder/coolant) in the breeding blanket. So it is important to study MHD flow of Lead-Lithium (Pb-Li). Open-source toolbox, OpenFOAM, is used to study single phase behaviour of Pb-Li. As the induced magnetic field is very small, Ni et al. electric potential algorithm is employed in OpenFOAM and validated with analytical results. This solver can also solve the temperature field with heat source term. Simulations are carried out in 2D straight channel for various values of Hartmann Number ranging from 100 to 5000 and velocity profile, temperature, current density and pressure drop are studied. (author)
Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.
Energy Technology Data Exchange (ETDEWEB)
Dechant, Lawrence [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Smith, Justin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2016-01-01
Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by
Controlling the Internal Heat Transfer Coefficient by the Characteristics of External Flows
Zhuromskii, V. M.
2018-01-01
The engineering-physical fundamentals of substance synthesis in a boiling apparatus are presented. We have modeled a system of automatic stabilization of the maximum internal heat transfer coefficient in such an apparatus by the characteristics of external flows on the basis of adaptive seeking algorithms. The results of operation of the system in the shop are presented.
Finite element simulation of internal flows with heat transfer using a ...
Indian Academy of Sciences (India)
Unknown
Velocity correction method; finite element simulation; turbulent .... CFD, developments in turbulence modeling have been only evolutionary and ...... variables are made dimensionless using appropriate combinations of Uav, H, ...... Srinivas M 1994 Finite element analysis of internal flows with heat transfer Ph D thesis, Indian.
Influence of internal channel geometry of gas turbine blade on flow structure and heat transfer
Szwaba, Ryszard; Kaczynski, Piotr; Telega, Janusz; Doerffer, Piotr
2017-12-01
This paper presents the study of the influence of channel geometry on the flow structure and heat transfer, and also their correlations on all the walls of a radial cooling passage model of a gas turbine blade. The investigations focus on the heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of internal cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include a corner fillets, ribs with fillet radii and a special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which has very realistic features.
Directory of Open Access Journals (Sweden)
I-Chung Liu
2012-01-01
Full Text Available We have analyzed the effects of variable heat flux and internal heat generation on the flow and heat transfer in a thin film on a horizontal sheet in the presence of thermal radiation. Similarity transformations are used to transform the governing equations to a set of coupled nonlinear ordinary differential equations. The obtained differential equations are solved approximately by the homotopy perturbation method (HPM. The effects of various parameters governing the flow and heat transfer in this study are discussed and presented graphically. Comparison of numerical results is made with the earlier published results under limiting cases.
Energy Technology Data Exchange (ETDEWEB)
Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abdullah, Z. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Hayat, T. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan)
2016-01-01
This research work addresses the three-dimensional hydromagnetic flow of Jeffrey fluid with nanoparticles. Flow is generated by a bidirectional stretching surface. The effects of thermal radiation and internal heat generation are encountered in energy expressions. More realistic convective boundary conditions at the surface are employed instead of constant surface temperature and mass species conditions. Boundary layer assumptions lead to the governing non-linear mathematical model. Resulting equations through momentum, energy and mass species are made dimensionless using suitable variables. The solution expressions of dimensionless velocities, temperature and nanoparticle concentration have been computed for the convergent series solutions. The impacts of interesting parameters on the dimensionless quantities are displayed and interpreted. The values of physical quantities are computed and analyzed. - Highlights: • Three-dimensional hydromagnetic flow of Jeffrey nanofluid is considered. • Brownian motion and thermophoresis effects are encountered. • Heat transfer analysis is performed with thermal radiation. • Results are plotted and visualized.
Dynamic response of a system with internal heat sources cooled by a flowing incompressible fluid
International Nuclear Information System (INIS)
Georgescu, R.; Dobrescu, C.
1975-01-01
The paper investigates the dynamic temperature response of an incompressible fluid which cools a duct with internal heat sources sinusoidally oscillated. The analytical results utilise the Laplace transformation technique. The experimental and calculated results are obtained by transfer function approach. Comparison of the calculated with the experimental data indicates agreement from 6 to 24 percent for the amplitude and up to 30 degree for the phase-shift. All the calculated data are below the experimental ones. The analytical method of transfer function approach presents interest and may be utilized for the initial calculations giving good results for flow rates above 1000 kg per hour
Method for calculating internal radiation and ventilation with the ADINAT heat-flow code
International Nuclear Information System (INIS)
Butkovich, T.R.; Montan, D.N.
1980-01-01
One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation and ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation
Linear Stability Analysis of Flow in an Internally Heated Rectangular Duct
Energy Technology Data Exchange (ETDEWEB)
Uhlmann, M.
2004-07-01
The linear stability of flow in a vertical rectangular duct subject to homogeneous internal heating, constant-temperature no-slip walls and a driving pressure gradient is investigated numerically. A full Chebyshevbased Galerkin method is found to be more reliable than a collocation method, both including the elimination of the pressure and the stream wise velocity from the system of equations and making use of the full symmetry properties. A classification of the mean flow-obtained as a function of Grashof and Reynolds numbers and the geometrical aspect ratio in terms of its inflectional properties is proposed. It is found that the flow loses stability at all aspects rations for a combination of finite thermal buoyancy and pressure forces with opposed sings. In the square duct, the unstable region coincides with the range where additional inflection lines are observed the mean velocity profile. Unstable eigenfunctions are obtained for all basic symmetry modes and their structure can be described as slightly elongated pockets of cross-stream-vertical motion, training each other along the stream wise direction. (Author) 22 refs.
Wang, C. R.; Towne, C. E.; Hippensteele, S. A.; Poinsatte, P. E.
1997-01-01
This study investigated the Navier-Stokes computations of the surface heat transfer coefficients of a transition duct flow. A transition duct from an axisymmetric cross section to a non-axisymmetric cross section, is usually used to connect the turbine exit to the nozzle. As the gas turbine inlet temperature increases, the transition duct is subjected to the high temperature at the gas turbine exit. The transition duct flow has combined development of hydraulic and thermal entry length. The design of the transition duct required accurate surface heat transfer coefficients. The Navier-Stokes computational method could be used to predict the surface heat transfer coefficients of a transition duct flow. The Proteus three-dimensional Navier-Stokes numerical computational code was used in this study. The code was first studied for the computations of the turbulent developing flow properties within a circular duct and a square duct. The code was then used to compute the turbulent flow properties of a transition duct flow. The computational results of the surface pressure, the skin friction factor, and the surface heat transfer coefficient were described and compared with their values obtained from theoretical analyses or experiments. The comparison showed that the Navier-Stokes computation could predict approximately the surface heat transfer coefficients of a transition duct flow.
Energy Technology Data Exchange (ETDEWEB)
Xiaoyan, Zhang [School of Energy and Power Engineering, Xi' an Jiaotong University, 28 Xianning Road, Xi' an, Shaanxi 710049 (China); School of Energy Engineering, Xi' an University of Science and Technology, 58 Yanta Street, Xi' an, Shaanxi 710054 (China)], E-mail: gqzxy@sohu.com; Xingqun, Zhang; Yunguang, Chen; Xiuling, Yuan [School of Energy and Power Engineering, Xi' an Jiaotong University, 28 Xianning Road, Xi' an, Shaanxi 710049 (China)
2008-06-15
The experimental study on evaporation heat transfer of R417A (R125/R134a/R600) flowing inside horizontal smooth and two internally grooved tubes with different geometrical parameters was conducted with the mass flow rate range from 176 to 344 kg m{sup -2} s{sup -1}, heat flux from 11 to 32 kW m{sup -2}, evaporation temperature from 0 to 5.5 deg. C and vapor quality from 0.2 to 1. Based on the experimental results, the mechanism and role of the mass flow rate, heat flux, vapor quality and enhanced surface influencing the evaporation heat transfer coefficients were analyzed and discussed. In comparison to R22, the evaporation heat transfer coefficients for R417A were lower and much lower in the internally grooved tubes than in the smooth tube. The present experimental results are also compared with the existing correlations, and the modified Kattan model is found to be in much better agreement with the experimental results than the Kattan model. The Koyama and Wellsandt microfin models all tend to over predict the evaporation heat transfer coefficients rather strongly for R417A inside internally grooved tubes.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiaoyan [School of Energy and Power Engineering, Xi' an Jiaotong University, 28 Xianning Road, Xi' an, Shaanxi 710049 (China); School of Energy Engineering, Xi' an University of Science and Technology, 58 Yanta Street, Xi' an, Shaanxi 710054 (China); Zhang, Xingqun; Chen, Yunguang; Yuan, Xiuling [School of Energy and Power Engineering, Xi' an Jiaotong University, 28 Xianning Road, Xi' an, Shaanxi 710049 (China)
2008-06-15
The experimental study on evaporation heat transfer of R417A (R125/R134a/R600) flowing inside horizontal smooth and two internally grooved tubes with different geometrical parameters was conducted with the mass flow rate range from 176 to 344 kg m{sup -2} s{sup -1}, heat flux from 11 to 32 kW m{sup -2}, evaporation temperature from 0 to 5.5{sup o}C and vapor quality from 0.2 to 1. Based on the experimental results, the mechanism and role of the mass flow rate, heat flux, vapor quality and enhanced surface influencing the evaporation heat transfer coefficients were analyzed and discussed. In comparison to R22, the evaporation heat transfer coefficients for R417A were lower and much lower in the internally grooved tubes than in the smooth tube. The present experimental results are also compared with the existing correlations, and the modified Kattan model is found to be in much better agreement with the experimental results than the Kattan model. The Koyama and Wellsandt microfin models all tend to over predict the evaporation heat transfer coefficients rather strongly for R417A inside internally grooved tubes. (author)
International Nuclear Information System (INIS)
Zhang Xiaoyan; Zhang Xingqun; Chen Yunguang; Yuan Xiuling
2008-01-01
The experimental study on evaporation heat transfer of R417A (R125/R134a/R600) flowing inside horizontal smooth and two internally grooved tubes with different geometrical parameters was conducted with the mass flow rate range from 176 to 344 kg m -2 s -1 , heat flux from 11 to 32 kW m -2 , evaporation temperature from 0 to 5.5 deg. C and vapor quality from 0.2 to 1. Based on the experimental results, the mechanism and role of the mass flow rate, heat flux, vapor quality and enhanced surface influencing the evaporation heat transfer coefficients were analyzed and discussed. In comparison to R22, the evaporation heat transfer coefficients for R417A were lower and much lower in the internally grooved tubes than in the smooth tube. The present experimental results are also compared with the existing correlations, and the modified Kattan model is found to be in much better agreement with the experimental results than the Kattan model. The Koyama and Wellsandt microfin models all tend to over predict the evaporation heat transfer coefficients rather strongly for R417A inside internally grooved tubes
Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade
Szwaba, Ryszard; Kaczynski, Piotr; Doerffer, Piotr; Telega, Janusz
2016-08-01
This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.
Energy Technology Data Exchange (ETDEWEB)
Kim, Sin-Yeob; Shin, Dong-Ho; Park, Goon-Cherl; Cho, Hyoung Kyu [Seoul National Univ., Seoul (Korea, Republic of); Kim, Chan-Soo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2016-10-15
VHTR being developed at Korea Atomic Energy Research Institute adopts an air-cooled Reactor Cavity Cooling System (RCCS) incorporating rectangular riser channels to remove the afterheat emitted from the reactor vessel. Because the performance of RCCS is determined by heat removal rate through the RCCS riser, it is important to understand the heat transfer phenomena in the RCCS riser to ensure the safety of the reactor. In the mixed convection, due to the buoyance force induced by temperature and density differences, local flow structure and heat transfer mode near the heated wall have significantly dissimilar characteristics from both forced convection and free convection. In this study, benchmark calculation was conducted to reproduce the previous statements that V2F turbulence model can capture the mixed convection phenomena with the Shehata's experimental data. Then, the necessity of the model validation for the mixed convection phenomena was confirmed with the CFD analyses for the geometry of the prototype RCCS riser. For the purpose of validating the turbulence models for mixed convection phenomena in the heated rectangular riser duct, validation plan with three experimental tests was introduced. Among them, the flow visualization test facility with preserved cross-section geometry was introduced and a preliminary test result was shown.
A Computational Study of Internal Flows in a Heated Water-Oil Emulsion Droplet
Sim, Jaeheon
2015-01-05
The vaporization characteristics of water-oil emulsion droplets are investigated by high fidelity computational simulations. One of the key objectives is to identify the physical mechanism for the experimentally observed behavior that the component in the dispersed micro-droplets always vaporizes first, for both oil-in-water and water-in-oil emulsion droplets. The mechanism of this phenomenon has not been clearly understood. In this study, an Eulerian-Lagrangian method was implemented with a temperature-dependent surface tension model and a dynamic adaptive mesh refinement in order to effectively capture the thermo-capillary effect of a micro-droplet in an emulsion droplet efficiently. It is found that the temperature difference in an emulsion droplet creates a surface tension gradient along the micro-droplet surface, inducing surface movement. Subsequently, the outer shear flow and internal flow circulation inside the droplet, referred to as the Marangoni convection, are created. The present study confirms that the Marangoni effect can be sufficiently large to drive the micro-droplets to the emulsion droplet surface at higher temperature, for both water-in-oil and oil-and-water emulsion droplets. A further parametric study with different micro-droplet sizes and temperature gradients demonstrates that larger micro-droplets move faster with larger temperature gradient. The oil micro-droplet in oil-in-water emulsion droplets moves faster due to large temperature gradients by smaller thermal conductivity.
Dunn, James C.; Hardee, Harry C.; Striker, Richard P.
1985-01-01
A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.
International Nuclear Information System (INIS)
Ravigururajan, T.S.; Bergles, A.E.
1985-01-01
General correlations for friction factors and heat transfer coefficients for single-phase turbulent flow in internally ribbed tubes are presented. Data from previous investigations are gathered for a wide range of tube parameters with e/d: 0.01 to 0.2; p/d: 0.1 to 7.0; α/90: 0.3 to 1.0, and flow parameters Re: 5000 to 250,000 and Pr: 0.66 to 37.6. The data were applied to a linear model to get normalized correlations that were then modified to fit tubes with extremely small parametric values. A shape function was included in the friction correlation to account for different rib profiles. The friction correlation predicts 96% of the data base to within +. 50% and 77% of the data base to within +. 20%. Corresponding figures for the heat transfer correlation are 99% and 69%. The present correlations are superior, for this extensive data base, to those presented by other investigators
International Nuclear Information System (INIS)
Chen Yunmei
1994-01-01
In this paper we study the heat flow of harmonic maps between two compact Riemannian manifolds. The global existence of the regular solution and the weak solution, as well as the blow up of the weak solution are discussed. (author). 14 refs
Valenzuela, Javier
2001-01-01
A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.
Experimental and Computational Studies of Heat Transfer in Complex Internal Flows.
1981-01-01
space having cross-sectional dimensions of 21.6 x 21.6 cm (8.5 x 8.5 in.). Into this space was poured silica aerogel powder insulation whose thermal...types of insulation (silica aerogel and styrofoam) and the surround- ing wooden containment structure. A total of 1600 grid points were used to resolve...Young, G., and Iverson, H. W., "An Investigation of Aircraft Heaters XXVII--Distribution of Heat Transfer Rate in the Entrance Section of a Circular
A study on nuclear heat load tolerable for NET/TF coils cooled by internal flow of helium II
International Nuclear Information System (INIS)
Hofmann, A.
1988-02-01
NbTi cables cooled by internal flow of superfluid helium are considered an option for the design of NET/TF coils with about 11 T peak fields. Starting from an available winding cross section of 0.61x0.61 m 2 for a 8 MA turns coil made of a 16 kA conductor it is shown that sufficient hydraulic cross section can be provided within such cables to remove the expected thermal load resulting from nuclear heating with exponential decay from inboard to outboard side of the winding. The concept is a pancake type coil with 1.8 K helium fed-in the high field region of each pancake. The temperature distribution within such coils is calculated, and the local safety margin is determined from temperature and field. The calculation takes account of nuclear and a.c. heating, and of thermal conductance between the individual layers and the coil casing. It is shown that operation with 1.8 K inlet and about 3 K outlet temperature is possible. The electrical insulation with about 0.5 mm thickness proves to provide sufficient thermal insulation. No additional thermal shield is required between the coil casing and the winding package. Two different types of conductors are being considered: a) POLO type cable with quadratic cross section and a central circular coolant duct, and b) an LCT type cable with two conductors wound in hand. Both concepts with about 500 m length of the cooland channels are shown to meet the requirements resulting from a peak nuclear heat load of 0.3 mW/cm 3 in the inboard turns. The hydraulic diameters are sufficient to operate each coils with self-sustained fountain effect pumps. Even appreciably higher heat loads with up to 3 mW/cm 3 of nuclear heating can be tolerated for the POLO type cable when the hydraulic diameter is enlarged to its maximum of 17 mm. (orig.) [de
Kivisalu, Michael Toomas
Space-based (satellite, scientific probe, space station, etc.) and millimeter -- to -- micro-scale (such as are used in high power electronics cooling, weapons cooling in aircraft, etc.) condensers and boilers are shear/pressure driven. They are of increasing interest to system engineers for thermal management because flow boilers and flow condensers offer both high fluid flow-rate-specific heat transfer capacity and very low thermal resistance between the fluid and the heat exchange surface, so large amounts of heat may be removed using reasonably-sized devices without the need for excessive temperature differences. However, flow stability issues and degredation of performance of shear/pressure driven condensers and boilers due to non-desireable flow morphology over large portions of their lengths have mostly prevented their use in these applications. This research is part of an ongoing investigation seeking to close the gap between science and engineering by analyzing two key innovations which could help address these problems. First, it is recommended that the condenser and boiler be operated in an innovative flow configuration which provides a non-participating core vapor stream to stabilize the annular flow regime throughout the device length, accomplished in an energy-efficient manner by means of ducted vapor re-circulation. This is demonstrated experimentally.. Second, suitable pulsations applied to the vapor entering the condenser or boiler (from the re-circulating vapor stream) greatly reduce the thermal resistance of the already effective annular flow regime. For experiments reported here, application of pulsations increased time-averaged heat-flux up to 900 % at a location within the flow condenser and up to 200 % at a location within the flow boiler, measured at the heat-exchange surface. Traditional fully condensing flows, reported here for comparison purposes, show similar heat-flux enhancements due to imposed pulsations over a range of frequencies
Directory of Open Access Journals (Sweden)
B. Y. Ogunmola
2016-01-01
Full Text Available Regular perturbation technique is applied to analyze the fluid flow and heat transfer in a pipe containing third-grade fluid with temperature-dependent viscosities and heat generation under slip and no slip conditions. The obtained approximate solutions were used to investigate the effects of slip on the heat transfer characteristics of the laminar flow in a pipe under Reynolds’s and Vogel’s temperature-dependent viscosities. Also, the effects of parameters such as variable viscosity, non-Newtonian parameter, viscous dissipation, and pressure gradient at various values were established. The results of this work were compared with the numerical results found in literature and good agreements were established. The results can be used to advance the analysis and study of the behavior of third-grade fluid flow and steady state heat transfer processes such as those found in coal slurries, polymer solutions, textiles, ceramics, catalytic reactors, and oil recovery applications.
Magnetic heat pump flow director
Howard, Frank S. (Inventor)
1995-01-01
A fluid flow director is disclosed. The director comprises a handle body and combed-teeth extending from one side of the body. The body can be formed of a clear plastic such as acrylic. The director can be used with heat exchangers such as a magnetic heat pump and can minimize the undesired mixing of fluid flows. The types of heat exchangers can encompass both heat pumps and refrigerators. The director can adjust the fluid flow of liquid or gas along desired flow directions. A method of applying the flow director within a magnetic heat pump application is also disclosed where the comb-teeth portions of the director are inserted into the fluid flow paths of the heat pump.
Investigation of internally finned LED heat sinks
Li, Bin; Xiong, Lun; Lai, Chuan; Tang, Yumei
2018-03-01
A novel heat sink is proposed, which is composed of a perforated cylinder and internally arranged fins. Numerical studies are performed on the natural convection heat transfer from internally finned heat sinks; experimental studies are carried out to validate the numerical results. To compare the thermal performances of internally finned heat sinks and externally finned heat sinks, the effects of the overall diameter, overall height, and installation direction on maximum temperature, air flow and heat transfer coefficient are investigated. The results demonstrate that internally finned heat sinks show better thermal performance than externally finned heat sinks; the maximum temperature of internally finned heat sinks decreases by up to 20% compared with the externally finned heat sinks. The existence of a perforated cylinder and the installation direction of the heat sink affect the thermal performance significantly; it is shown that the heat transfer coefficient of the heat sink with the perforated cylinder is improved greater than that with the imperforated cylinder by up to 34%, while reducing the mass of the heat sink by up to 13%. Project supported by the Scientific Research Fund of Sichuan Provincial Education Department (No. 18ZB0516) and the Sichuan University of Arts and Science (No. 2016KZ009Y).
Heat exchanger with oscillating flow
Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)
1993-01-01
Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.
Magnetic Heat Pump Containing Flow Diverters
Howard, Frank S.
1995-01-01
Proposed magnetic heat pump contains flow diverters for suppression of undesired flows. If left unchecked, undesired flows mix substantial amounts of partially heated and partially cooled portions of working fluid, effectively causing leakage of heat from heated side to cooled side. By reducing leakage of heat, flow diverters increase energy efficiency of magnetic heat pump, potentially offering efficiency greater than compressor-driven refrigerator.
VII international district heating conference
International Nuclear Information System (INIS)
1988-01-01
The proceedings of the 7th International District Heating Conference contain the full texts of the 89 presented papers of which 11 fall under the INIS Subject Scope. The conference met in seven sessions and dealt with the following problem areas: design and optimization of systems of district heating, integration of the power system and the district heating systems, cooperation of nuclear and fossil burning sources in district heating systems, the use of specific nuclear power plants for heating purposes, questions of the control of systems of district heating, the development of components of heating networks, the reliability and design of heat supply pipes. (Z.M.)
Umi, N. N.; Norazman, M. N.; Daud, N. M.; Yusof, M. A.; Yahya, M. A.; Othman, M.
2018-04-01
Green building technology and sustainability development is current focus in the world nowadays. In Malaysia and most tropical countries the maximum temperature recorded typically at 35°C. Air-conditioning system has become a necessity in occupied buildings, thereby increasing the cost of electric consumption. The aim of this study is to find out the solution in minimizing heat transfer from the external environment and intentions towards going green. In this study, the experimental work includes testing three types of concrete wall panels. The main heat intervention material in this research is 2 inch diameter Polyvinyl Chloride (PVC) pipe embedded at the center of the concrete wall panel, while the EPS foam beads were added to the cement content in the concrete mix forming the outer layer of the wall panel. Water from the rainwater harvesting system is regulated in the PVC pipe to intervene with the heat conductivity through the wall panel. Results from the experimental works show that the internal surface temperature of these heat resistance wall panels is to 3□C lower than control wall panel from plain interlocking bricks.
Heat transfer from internally heated hemispherical pools
International Nuclear Information System (INIS)
Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.
1980-01-01
Experiments were conducted on heat transfer from internally heated ZnSO 4 -H 2 O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere
International Nuclear Information System (INIS)
Rath, Pravat Kumar; Dash, G.C.; Patra, Ajit Kumar
2010-01-01
Effect of Hall current on the unsteady free convection flow of an electrically conducting incompressible viscous fluid past an exponentially accelerated vertical porous flat plate with internal heat absorption/generation in the presence of foreign gases (such as H 2 , CO 2 , H 2 O, NH 3 ) and chemical reaction has been investigated. An uniform magnetic field transverse to the plate has been applied. The effects of the Hall current m, the hydromagnetic parameter Mt, the chemical reaction parameter K c the Grashof number for heat transfer G r , the Grashof number for mass transfer G c , the Schmidt number S c , the Prandtl number P r and the transpiration parameter α are discussed in detail. (author)
International Nuclear Information System (INIS)
1980-08-01
Separate abstracts are included for each of the papers presented concerning critical flow of two-phase mixtures; two-phase flow instrumentation; critical heat flux and effects of local disturbances; heat transfer and rewetting during reflood; hydrodynamic mechanisms in boiling heat transfer; and entrainment and droplet deposition in two-phase flow. Five papers have been previously abstracted and input to the data base
Langseth, M. G.
1977-01-01
The principal components of the experiment were probes, each with twelve thermometers of exceptional accuracy and stability, that recorded temperature variations at the surface and in the regolith down to 2.5 m. The Apollo 15 experiment and the Apollo 17 probes recorded lunar surface and subsurface temperatures. These data provided a unique and valuable history of the interaction of solar energy with lunar surface and the effects of heat flowing from the deep interior out through the surface of the moon. The interpretation of these data resulted in a clearer definition of the thermal and mechanical properties of the upper two meters of lunar regolith, direct measurements of the gradient in mean temperature due to heat flow from the interior and a determination of the heat flow at the Apollo 15 and Apollo 17 sites.
Directory of Open Access Journals (Sweden)
Dulal Pal
2015-05-01
Full Text Available In this paper, we analyzed the buoyancy-driven radiative non-isothermal heat transfer in a nanofluid stagnation-point flow over a stretching/shrinking sheet embedded in a porous medium.The effects of thermal radiation and internal heat generation/absorption along with suction/injection at the boundary are also considered. Three different types of nanofluids, namely the Copper-water, the Alumina-water and the Titanium dioxide water are considered. The resulting coupled nonlinear differential equations are solved numerically by a fifth-order Runge-Kutta-Fehlberg integration scheme with a shooting technique. A good agreement is found between the present numerical results and the available results in the literature for some special cases. The effects of the physical parameters on the flow and temperature characteristics are presented through tables and graphs, and the salient features are discussed. The results obtained reveal many interesting behaviors that warrant further study on the heat transfer enhancement due to the nanofluids.
International Nuclear Information System (INIS)
Cull, J.P.
1981-01-01
Secular and long-term periodic changes in surface temperature cause perturbations to the geothermal gradient which may be significant to depths of at least 1000 m, and major corrections are required to determine absolute values of heat flow from the Earth's interior. However, detailed climatic models remain contentious and estimates of error in geothermal gradients differ widely. Consequently, regions of anomalous heat flow which could contain geothermal resources may be more easily resolved by measuring relative values at a standard depth (e.g. 100 m) so that all data are subject to similar corrections. (orig./ME)
Internally Heated Screw Pyrolysis Reactor (IHSPR) heat transfer performance study
Teo, S. H.; Gan, H. L.; Alias, A.; Gan, L. M.
2018-04-01
1.5 billion end-of-life tyres (ELT) were discarded globally each year and pyrolysis is considered the best solution to convert the ELT into valuable high energy-density products. Among all pyrolysis technologies, screw reactor is favourable. However, conventional screw reactor risks plugging issue due to its lacklustre heat transfer performance. An internally heated screw pyrolysis reactor (IHSPR) was developed by local renewable energy industry, which serves as the research subject for heat transfer performance study of this particular paper. Zero-load heating test (ZLHT) was first carried out to obtain the operational parameters of the reactor, followed by the one dimensional steady-state heat transfer analysis carried out using SolidWorks Flow Simulation 2016. Experiments with feed rate manipulations and pyrolysis products analyses were conducted last to conclude the study.
Matson, D. L.; Ransford, G. A.; Johnson, T. V.
1981-01-01
The existing ground-based measurements of Io's thermal emission at infrared wavelengths of 8.4, 10.6, and 21 microns have been reexamined. Present in these data is the signature of hot spots, presumably similar to the hot spots seen by the IRIS experiment on Voyager. It is possible to extract from these data the total amount of power radiated. Since the hot spots are believed to be a result of deep-seated activity in Io and since the remainder of Io's surface is an extraordinarily poor thermal conductor, the power radiated by the hot spots is essentially the total heat flow. The analysis yields a heat flow of 2 + or - 1 W/sq m. This value is tremendously large in comparison to the average heat flow of the earth (0.06 W/sq m) and the moon (0.02 W/sq m), but is characteristic of active geothermal areas on the earth. A heat flow this large requires that the interior of Io be at least partially molten on a global scale.
Convection flows driven by laser heating of a liquid layer
Rivière , David; Selva , Bertrand; Chraibi , Hamza; Delabre , Ulysse; Delville , Jean-Pierre
2016-01-01
International audience; When a fluid is heated by the absorption of a continuous laser wave, the fluid density decreases in the heated area. This induces a pressure gradient that generates internal motion of the fluid. Due to mass conservation, convection eddies emerge in the sample. To investigate these laser-driven bulk flows at the microscopic scale, we built a setup to perform temperature measurements with a fluorescent-sensitive dye on the one hand, and measured the flow pattern at diffe...
Interpretation of lunar heat flow data
International Nuclear Information System (INIS)
Conel, J.E.; Morton, J.B.
1975-01-01
Lunar heat flow observations at the Apollo 15 and 17 sites can be interpreted to imply bulk U concentrations for the Moon of 5 to 8 times those of normal chondrites and 2 to 4 times terrestrial values inferred from the Earth's heat flow and the assumption of thermal steady state between surface heat flow and heat production. A simple model of nearsurface structure that takes into account the large difference in (highly insulating) regolith thickness between mare and highland provinces is considered. This model predicts atypically high local values of heat flow near the margins of mare regions--possibly a factor of 10 or so higher than the global average. A test of the proposed model using multifrequency microwave techniques appears possible wherein heat flow traverse measurements are made across mare-highland contacts. The theoretical considerations discussed here urge caution in attributing global significance to point heat-flow measurements on the Moon
Axial flow heat exchanger devices and methods for heat transfer using axial flow devices
Koplow, Jeffrey P.
2016-02-16
Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.
Visualisation of heat transfer in laminar flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2009-01-01
Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients at non-adiabatic walls. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the
Auxiliary Heat Exchanger Flow Distribution Test
International Nuclear Information System (INIS)
Kaufman, J.S.; Bressler, M.M.
1983-01-01
The Auxiliary Heat Exchanger Flow Distribution Test was the first part of a test program to develop a water-cooled (tube-side), compact heat exchanger for removing heat from the circulating gas in a high-temperature gas-cooled reactor (HTGR). Measurements of velocity and pressure were made with various shell side inlet and outlet configurations. A flow configuration was developed which provides acceptable velocity distribution throughout the heat exchanger without adding excessive pressure drop
Lunar Heat Flow Probe, Phase I
National Aeronautics and Space Administration — To accurately determine endogenic heat flow, both thermal gradient and thermal conductivity measurements are needed. The thermal gradient measurement can be achieved...
Heat flow in a He II filled fin
International Nuclear Information System (INIS)
Warren, R.P.
1984-01-01
This chapter demonstrates the influence of diameter, length, Kapitza conductance and temperature on the heat carrying capacity of an externally cooled, circular He II filled channel with zero net mass flow and of negligible wall thermal resistance. Topics considered include the internal convection mechanism and the heat transfer model (boundary conditions, solution procedure). The large apparent thermal conductivity of He-II is explained by the two fluid model as an internal convection in which there is a counter flow of the normal and superfluids with no net mass flow. A separate bath is considered in which an He-IIp (pressurized superfluid helium) filled fin is immersed which extends from the heated reservoir. A single heat sink can serve multiple heat sources
Stokes flow heat transfer in an annular, rotating heat exchanger
International Nuclear Information System (INIS)
Saatdjian, E.; Rodrigo, A.J.S.; Mota, J.P.B.
2011-01-01
The heat transfer rate into highly viscous, low thermal-conductivity fluids can be enhanced significantly by chaotic advection in three-dimensional flows dominated by viscous forces. The physical effect of chaotic advection is to render the cross-sectional temperature field uniform, thus increasing both the wall temperature gradient and the heat flux into the fluid. A method of analysis for one such flow-the flow in the eccentric, annular, rotating heat exchanger-and a procedure to determine the best heat transfer conditions, namely the optimal values of the eccentricity ratio and time-periodic rotating protocol, are discussed. It is shown that in continuous flows, such as the one under consideration, there exists an optimum frequency of the rotation protocol for which the heat transfer rate is a maximum. - Highlights: → The eccentric, annular, rotating heat exchanger is studied for periodic Stokes flow. → Counter-rotating the inner tube with a periodic velocity enhances the heat transfer. → The heat-transfer enhancement under such conditions is due to chaotic advection. → For a given axial flow rate there is a frequency that maximizes the heat transfer. → There is also an optimum value of the eccentricity ratio.
Critical heat flux and flow pattern for water flow in annular geometry
International Nuclear Information System (INIS)
Park, Jae Wook; Baek, Won Pil; Chang, Soon Heung
1996-01-01
An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced-circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m, inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, churn-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow
Directory of Open Access Journals (Sweden)
Brahim Berrabah
2017-02-01
Full Text Available Numerical predictions of three-dimensional flow and heat transfer are performed for a two-pass square channel with 45° staggered ribs in non-orthogonally mode-rotation using the second moment closure model. At Reynolds number of 25,000, the rotation numbers studied were 0, 0.24, 0.35 and 1.00. The density ratios were 0.13, 0.23 and 0.50. The results show that at high buoyancy parameter and high rotation number with a low density ratio, the flow in the first passage is governed by the secondary flow induced by the rotation whereas the secondary flow induced by the skewed ribs was almost distorted. As a result the heat transfer rate is enhanced on both co-trailing and co-leading sides compared to low and medium rotation number. In contrast, for the second passage, the rotation slightly reduces the heat transfer rate on co-leading side at high rotation number with a low density ratio and degrades it significantly on both co-trailing and co-leading sides at high buoyancy parameter compared to the stationary, low and medium rotation numbers. The numerical results are in fair agreement with available experimental data in the bend region and the second passage, while in the first passage were overestimated at low and medium rotation numbers.
Heat flow map of the Bohemian massif
Energy Technology Data Exchange (ETDEWEB)
Cermak, V [Geophys. Inst., CS Acad. of Sci.
1977-01-01
Forty seven heat flow values for the Bohemian massif were used to determine the heat flow pattern of the area. By including data from neighboring countries it was possible to draw an isothermal map outlining the geothermal activity. As a result, it is possible to closely correlate the heat flow and the tectonic structure. It is obvious that the areas of high geothermal activity correspond to zones of crustal weakness associated with two major faults bordering the rigid central section of the massif. The highest heat flow values coincide with the axis of the sedimentary basin. The development of these heat flow patterns should assist in the recognition of probable areas of geothermal resources and several promising sites are readily discernible.
Energy Technology Data Exchange (ETDEWEB)
Payan Rodriguez, Luis Alfredo
2003-09-01
In this paper the development of a research project oriented to the analysis of the heat transfer of the water flow in nucleate boiling is presented. Here a mathematical model is described to characterize the water flow in boiling condition in vertical tubes by means of which the temperature distributions in the tube wall and in the water flow are obtained, including the calculation of the pressure drop throughout the tube. In addition, a mechanistic model focused to the prediction of the critical heat flow in vertical tubes uniformly heated was modified to be applied in non-uniform heat flow conditions. The proposed mathematical models were used in a case study derived from a real problem in a thermoelectric power plant, where it was required to simulate the process of boiling in fireplace tubes of the steam generator to determine the causes of the faults that happened in a considerable number of tubes. With the obtained results it was possible to establish that the faults in the tubes of the analyzed steam generator were originated because the heat transfer rate in the fireplace reached critical values that caused the deviation of the nucleate boiling to film boiling, causing the diminution of the heat transfer coefficient with the consequent sudden increase in the tube wall temperature. [Spanish] En este trabajo se presenta el desarrollo de un proyecto de investigacion orientado al analisis de la transferencia de calor en flujo de agua en ebullicion nucleada. Aqui se describe un modelo matematico para caracterizar el flujo de agua en ebullicion en tubos verticales mediante el cual se obtienen las distribuciones de temperatura en la pared del tubo y en el flujo de agua, incluyendo el calculo de la caida de presion a lo largo del tubo. Ademas, un modelo mecanistico enfocado a la prediccion del flujo de calor critico en tubos verticales uniformemente calentados fue modificado para aplicarlo en condiciones de flujo de calor no uniforme. Los modelos matematicos
Heat transfer from internally-heated molten UO2 pools
International Nuclear Information System (INIS)
Stein, R.P.; Baker, L. Jr.; Gunther, W.H.; Cook, C.
1978-01-01
Experimental measurements of heat transfer from internally heated pools of molten UO 2 have been obtained for two cell sizes: 10 cm x 10 cm and 20 cm x 20 cm. The experiments with the large cell have supported a previous conclusion from early small data that the measured downward heat fluxes are higher than would be expected on the basis of considerations of thermal convection. A convective model underpredicts the downward heat fluxes by a factor of 2.5 to 4.5 for all but one early experiment. Arbitrary assumptions of increased thermal conductivity do not account for the discrepancy. A single model based on internal thermal radiation heat transfer is able to account for the high values. The model uses the optically thick Rosseland approximation. Because of this, it is tentatively concluded that thermal radiation plays a dominant role in controlling the heat transfer from internally heated molted fuel
Heat and mass transfer and hydrodynamics in swirling flows (review)
Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.
2017-02-01
Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.
2007 Estimated International Energy Flows
Energy Technology Data Exchange (ETDEWEB)
Smith, C A; Belles, R D; Simon, A J
2011-03-10
An energy flow chart or 'atlas' for 136 countries has been constructed from data maintained by the International Energy Agency (IEA) and estimates of energy use patterns for the year 2007. Approximately 490 exajoules (460 quadrillion BTU) of primary energy are used in aggregate by these countries each year. While the basic structure of the energy system is consistent from country to country, patterns of resource use and consumption vary. Energy can be visualized as it flows from resources (i.e. coal, petroleum, natural gas) through transformations such as electricity generation to end uses (i.e. residential, commercial, industrial, transportation). These flow patterns are visualized in this atlas of 136 country-level energy flow charts.
Lunar ash flow with heat transfer.
Pai, S. I.; Hsieh, T.; O'Keefe, J. A.
1972-01-01
The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.
Conjugate Heat Transfer Study in Hypersonic Flows
Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar
2018-04-01
Coupled and decoupled conjugate heat transfer (CHT) studies are carried out to imitate experimental studies for heat transfer measurement in hypersonic flow regime. The finite volume based solvers are used for analyzing the heat interaction between fluid and solid domains. Temperature and surface heat flux signals are predicted by both coupled and decoupled CHT analysis techniques for hypersonic Mach numbers. These two methodologies are also used to study the effect of different wall materials on surface parameters. Effectiveness of these CHT solvers has been verified for the inverse problem of wall heat flux recovery using various techniques reported in the literature. Both coupled and decoupled CHT techniques are seen to be equally useful for prediction of local temperature and heat flux signals prior to the experiments in hypersonic flows.
Heat flow and heat generation in greenstone belts
Drury, M. J.
1986-01-01
Heat flow has been measured in Precambrian shields in both greenstone belts and crystalline terrains. Values are generally low, reflecting the great age and tectonic stability of the shields; they range typically between 30 and 50 mW/sq m, although extreme values of 18 and 79 mW/sq m have been reported. For large areas of the Earth's surface that are assumed to have been subjected to a common thermotectonic event, plots of heat flow against heat generation appear to be linear, although there may be considerable scatter in the data. The relationship is expressed as: Q = Q sub o + D A sub o in which Q is the observed heat flow, A sub o is the measured heat generation at the surface, Q sub o is the reduced heat flow from the lower crust and mantle, and D, which has the dimension of length, represents a scale depth for the distribution of radiogenic elements. Most authors have not used data from greenstone belts in attempting to define the relationship within shields, considering them unrepresentative and preferring to use data from relatively homogeneous crystalline rocks. A discussion follows.
Heat flow anomalies and their interpretation
Chapman, David S.; Rybach, Ladislaus
1985-12-01
More than 10,000 heat flow determinations exist for the earth and the data set is growing steadily at about 450 observations per year. If heat flow is considered as a surface expression of geothermal processes at depth, the analysis of the data set should reveal properties of those thermal processes. They do, but on a variety of scales. For this review heat flow maps are classified by 4 different horizontal scales of 10 n km (n = 1, 2, 3 and 4) and attention is focussed on the interpretation of anomalies which appear with characteristic dimensions of 10 (n - 1) km in the respective representations. The largest scale of 10 4 km encompasses heat flow on a global scale. Global heat loss is 4 × 10 13 W and the process of sea floor spreading is the principal agent in delivering much of this heat to the surface. Correspondingly, active ocean ridge systems produce the most prominent heat flow anomalies at this scale with characteristic widths of 10 3 km. Shields, with similar dimensions, exhibit negative anomalies. The scale of 10 3 km includes continent wide displays. Heat flow patterns at this scale mimic tectonic units which have dimensions of a few times 10 2 km, although the thermal boundaries between these units are sometimes sharp. Heat flow anomalies at this scale also result from plate tectonic processes, and are associated with arc volcanism, back arc basins, hot spot traces, and continental rifting. There are major controversies about the extent to which these surface thermal provinces reflect upper mantle thermal conditions, and also about the origin and evolution of the thermal state of continental lithosphere. Beginning with map dimensions of 10 2 km thermal anomalies of scale 10 1 km, which have a definite crustal origin, become apparent. The origin may be tectonic, geologic, or hydrologic. Ten kilometers is a common wavelength of topographic relief which drives many groundwater flow systems producing thermal anomalies. The largest recognized continental
Burnout heat flux in natural flow boiling
International Nuclear Information System (INIS)
Helal, M.M.; Darwish, M.A.; Mahmoud, S.I.
1978-01-01
Twenty runs of experiments were conducted to determine the critical heat flux for natural flow boiling with water flowing upwards through annuli of centrally heated stainless steel tube. The test section has concentric heated tube of 14mm diameter and heated lengthes of 15 and 25 cm. The outside surface of the annulus was formed by various glass tubes of 17.25, 20 and 25.9mm diameter. System pressure is atmospheric. Inlet subcooling varied from 18 to 5 0 C. Obtained critical heat flux varied from 24.46 to 62.9 watts/cm 2 . A number of parameters having dominant influence on the critical heat flux and hydrodynamic instability (flow and pressure oscillations) preceeding the burnout have been studied. These parameters are mass flow rate, mass velocity, throttling, channel geometry (diameters ratio, length to diameter ratio, and test section length), and inlet subcooling. Flow regimes before and at the moments of burnout were observed, discussed, and compared with the existing physical model of burnout
Gas flow environmental and heat transfer nonrotating 3D program
Geil, T.; Steinhoff, J.
1983-01-01
A complete set of benchmark quality data for the flow and heat transfer within a large rectangular turning duct is being compiled. These data will be used to evaluate and verify three dimensional internal viscous flow models and computational codes. The analytical objective is to select such a computational code and define the capabilities of this code to predict the experimental results. Details of the proper code operation will be defined and improvements to the code modeling capabilities will be formulated.
Coupled equations for transient water flow, heat flow, and ...
Indian Academy of Sciences (India)
interacting processes, including flow of fluids, deformation of porous materials, chemical reactions, and transport of ... systems involving the flow of water, heat, and deformation. Such systems are ..... Defined thus, αI is independent of boundary con- ditions in an ... perature change with free deformation at constant total stress ...
Experimental study on local heat transfer characteristics of porous media with internal heat source
International Nuclear Information System (INIS)
Zan Yuanfeng; Wang Taotao; Xiao Zejun; Wang Fei; Huang Yanping
2008-01-01
Model of porous media with internal heat source is established. The model uses water as flowing media, and the stainless steel test section is packed with steel spheres in manner of regular triangle, respectively. The armoured resistance wire is inserted inside the steel sphere. On the basis of the experimental model, many parameters of the local heat transfer characteristics including current velocity and wall temperature of steel sphere are measured. The experimental results show that the coefficient of heat transfer scarcely changes with pressure. The coefficient of heat transfer increases with the surface heat flux of steel sphere. When raising the inlet temperature of the cooling water, the coefficient of heat transfer presents the descending trend. In addition, the influence of entrance effect on heat transfer is discovered in the experiment, which is much less than the liquid flow in the light tube. After experiment data are analyzed and processed, the relation model of heat transfer on local heat transfer characteristic of porous media with internal heat source was described with a power-law-equation. The deviations between calculation and experimental values are within ±10%. (authors)
Stirling Engine With Radial Flow Heat Exchangers
Vitale, N.; Yarr, George
1993-01-01
Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.
Turbulent Heat Transfer in Curved Pipe Flow
Kang, Changwoo; Yang, Kyung-Soo
2013-11-01
In the present investigation, turbulent heat transfer in fully-developed curved pipe flow with axially uniform wall heat flux has been numerically studied. The Reynolds numbers under consideration are Reτ = 210 (DNS) and 1,000 (LES) based on the mean friction velocity and the pipe radius, and the Prandtl number (Pr) is 0.71. For Reτ = 210 , the pipe curvature (κ) was fixed as 1/18.2, whereas three cases of κ (0.01, 0.05, 0.1) were computed in the case of Reτ = 1,000. The mean velocity, turbulent intensities and heat transfer rates obtained from the present calculations are in good agreement with the previous numerical and experimental results. To elucidate the secondary flow structures due to the pipe curvature, the mean quantities and rms fluctuations of the flow and temperature fields are presented on the pipe cross-sections, and compared with those of the straight pipe flow. To study turbulence structures and their influence on turbulent heat transfer, turbulence statistics including but not limited to skewness and flatness of velocity fluctuations, cross-correlation coefficients, an Octant analysis, and turbulence budgets are presented and discussed. Based on our results, we attempt to clarify the effects of Reynolds number and the pipe curvature on turbulent heat transfer. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0008457).
Program Computes Flows Of Fluids And Heat
Cullimore, Brent; Ring, Steven; Welch, Mark
1993-01-01
SINDA'85/FLUINT incorporates lumped-parameter-network and one-dimensional-flow mathematical models. System enables analysis of mutual influences of thermal and flow phenomena. Offers two finite-difference numerical solution techniques: forward-difference explicit approximation and Crank-Nicholson approximation. Enables simulation of nonuniform heating and facilitates mathematical modeling of thin-walled heat exchangers. Ability to model nonequilibrium behavior within two-phase volumes included. Recent changes in program improve modeling of real evaporator pumps and other capillary-assist evaporators. Written in FORTRAN 77.
Thermodynamic efficiency of information and heat flow
International Nuclear Information System (INIS)
Allahverdyan, Armen E; Janzing, Dominik; Mahler, Guenter
2009-01-01
A basic task of information processing is information transfer (flow). Here we study a pair of Brownian particles each coupled to a thermal bath at temperatures T 1 and T 2 . The information flow in such a system is defined via the time-shifted mutual information. The information flow nullifies at equilibrium, and its efficiency is defined as the ratio of the flow to the total entropy production in the system. For a stationary state the information flows from higher to lower temperatures, and its efficiency is bounded from above by (max[T 1 ,T 2 ])/(|T 1 −T 2 |). This upper bound is imposed by the second law and it quantifies the thermodynamic cost for information flow in the present class of systems. It can be reached in the adiabatic situation, where the particles have widely different characteristic times. The efficiency of heat flow—defined as the heat flow over the total amount of dissipated heat—is limited from above by the same factor. There is a complementarity between heat and information flow: the set-up which is most efficient for the former is the least efficient for the latter and vice versa. The above bound for the efficiency can be (transiently) overcome in certain non-stationary situations, but the efficiency is still limited from above. We study yet another measure of information processing (transfer entropy) proposed in the literature. Though this measure does not require any thermodynamic cost, the information flow and transfer entropy are shown to be intimately related for stationary states
Free convection film flows and heat transfer
Shang, Deyi
2010-01-01
Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.
Editorial to "Heat flow: recent advances"
Czech Academy of Sciences Publication Activity Database
Čermák, Vladimír; Huang, S.; Ravat, D.; Verdoya, M.
2018-01-01
Roč. 107, č. 1 (2018), s. 1-3 ISSN 1437-3254 Institutional support: RVO:67985530 Keywords : geothermics * climate change * terrestrial heat flow Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.283, year: 2016
Numberical Solution to Transient Heat Flow Problems
Kobiske, Ronald A.; Hock, Jeffrey L.
1973-01-01
Discusses the reduction of the one- and three-dimensional diffusion equation to the difference equation and its stability, convergence, and heat-flow applications under different boundary conditions. Indicates the usefulness of this presentation for beginning students of physics and engineering as well as college teachers. (CC)
Transition to chaos in a square enclosure containing internal heat sources
Energy Technology Data Exchange (ETDEWEB)
Baytas, A.C. [Institute For Nuclear Energy, Istanbul (Turkey)
1995-09-01
A numerical investigation is performed to study the transition from steady to chaotic flow of a fluid confined in a two-dimensional square cavity. The cavity has rigid walls of constant temperature containing uniformly distributed internal heat source. Effects of the Rayleigh number of flow and heat transfer rates are studied. In addition to, same problem is solved for sinusoidally changing internal heat source to show its effect on the flow model and heat transfer of the enclosures. Details of oscillatory solutions and flow bifurcations are presented.
Critical heat flux and flow pattern for water flow in annular geometry
International Nuclear Information System (INIS)
Park, J.-W.; Baek, W.-P.; Chang, S.H.
1997-01-01
An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced-circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m, inner diameter 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, churn-to-annular flow transition and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for the upward flow. In addition to the experiment, selected CHF correlations for annuli are assessed based on 1156 experimental data from various sources. The Doerffer et al. (1994); Barnett (1966); Jannsen and Kervinen (1963); Levitan and Lantsman (1977) correlations show reasonable predictions for wide parameter ranges, among which the Doerffer et al. (1994) correlation shows the widest parameter ranges and a possibility of further improvement. However, there is no correlation predicting the low-pressure, low-flow CHF satisfactorily. (orig.)
Chiaramonte, Francis; Motil, Brian; McQuillen, John
2014-01-01
The Two-phase Heat Transfer International Topical Team consists of researchers and members from various space agencies including ESA, JAXA, CSA, and RSA. This presentation included descriptions various fluid experiments either being conducted by or planned by NASA for the International Space Station in the areas of two-phase flow, flow boiling, capillary flow, and crygenic fluid storage.
International Nuclear Information System (INIS)
Li Longjian; Liu Hongtao; Cui Wenzhi
2007-01-01
The conjugated heat transfer of natural convection in pool with internal heat source and the forced convection in the tube was analyzed, and the corresponding three-dimensional physical and mathematical model was proposed. A control volume based finite element method was employed to solve numerically the problem. The computations were performed for different internal heat source intensity of the pool and the different flow velocity in the tube. The computed heat transfer coefficients on the inner and outer wall showed well consistency of those calculated with the empirical correlations. Compared with the measured total heat transfer coefficients between the fluids in and out of the tube, the computed ones showed also the well consistency, which implied that the numerical model proposed in this paper was reliable. The research results revealed that the total heat transfer coefficients between the fluids were strongly affected by the internal heat source intensity of the pool liquid and the flow velocity in the tube. (authors)
Heat transfer to accelerating gas flows
International Nuclear Information System (INIS)
Kennedy, T.D.A.
1978-01-01
The development of fuels for gas-cooled reactors has resulted in a number of 'gas loop' experiments in materials-testing research reactors. In these experiments, efforts are made to reproduce the conditions expected in gas-cooled power reactors. Constant surface temperatures are sought over a short (300 mm) fuelled length, and because of entrance effects, an accelerating flow is required to increase the heat transfer down-stream from the entrance. Strong acceleration of a gas stream will laminarise the flow even at Reynolds Numbers up to 50000, far above values normally associated with laminar flow. A method of predicting heat transfer in this situation is presented here. An integral method is used to find the velocity profile; this profile is then used in an explicit finite-difference solution of the energy equation to give a temperature profile and resultant heat-transfer coefficient values. The Kline criterion, which compares viscous and disruptive forces, is used to predict whether the flow will be laminar. Experimental results are compared with predictions, and good agreement is found to exist. (author)
Two-dimensional heat flow apparatus
McDougall, Patrick; Ayars, Eric
2014-06-01
We have created an apparatus to quantitatively measure two-dimensional heat flow in a metal plate using a grid of temperature sensors read by a microcontroller. Real-time temperature data are collected from the microcontroller by a computer for comparison with a computational model of the heat equation. The microcontroller-based sensor array allows previously unavailable levels of precision at very low cost, and the combination of measurement and modeling makes for an excellent apparatus for the advanced undergraduate laboratory course.
Assessment of interfacial heat transfer models under subcooled flow boiling
Energy Technology Data Exchange (ETDEWEB)
Ribeiro, Guilherme B.; Braz Filho, Francisco A., E-mail: gbribeiro@ieav.cta.br, E-mail: fbraz@ieav.cta.br [Instituto de Estudos Avançados (DCTA/IEAv), São José dos Campos, SP (Brazil). Div. de Energia Nuclear
2017-07-01
The present study concerns a detailed analysis of subcooled flow boiling characteristics under high pressure systems using a two-fluid Eulerian approach provided by a Computational Fluid Dynamics (CFD) solver. For this purpose, a vertical heated pipe made of stainless steel with an internal diameter of 15.4 mm was considered as the modeled domain. An uniform heat flux of 570 kW/m2 and saturation pressure of 4.5 MPa were applied to the channel wall, whereas water mass flux of 900 kg/m2s was considered for all simulation cases. The model was validated against a set of experimental data and results have indicated a promising use of CFD technique for the estimation of wall temperature, the liquid bulk temperature and the location of the departure of nucleate boiling. Different sub-models of interfacial heat transfer coefficient were applied and compared, allowing a better prediction of void fraction along the heated channel. (author)
Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump
Hong, Feng; Yuan, Jianping; Zhou, Banglun
2016-01-01
In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numerically calculated by using the homogeneous mixture cavitation model based on the Rayleigh-Plesset
Mixing in heterogeneous internally-heated convection
Limare, A.; Kaminski, E. C.; Jaupart, C. P.; Farnetani, C. G.; Fourel, L.; Froment, M.
2017-12-01
Past laboratory experiments of thermo chemical convection have dealt with systems involving fluids with different intrinsic densities and viscosities in a Rayleigh-Bénard setup. Although these experiments have greatly improved our understanding of the Earth's mantle dynamics, they neglect a fundamental component of planetary convection: internal heat sources. We have developed a microwave-based method in order to study convection and mixing in systems involving two layers of fluid with different densities, viscosities, and internal heat production rates. Our innovative laboratory experiments are appropriate for the early Earth, when the lowermost mantle was likely enriched in incompatible and heat producing elements and when the heat flux from the core probably accounted for a small fraction of the mantle heat budget. They are also relevant to the present-day mantle if one considers that radioactive decay and secular cooling contribute both to internal heating. Our goal is to quantify how two fluid layers mix, which is still very difficult to resolve accurately in 3-D numerical calculations. Viscosities and microwave absorptions are tuned to achieve high values of the Rayleigh-Roberts and Prandtl numbers relevant for planetary convection. We start from a stably stratified system where the lower layer has higher internal heat production and density than the upper layer. Due to mixing, the amount of enriched material gradually decreases to zero over a finite time called the lifetime. Based on more than 30 experiments, we have derived a scaling law that relates the lifetime of an enriched reservoir to the layer thickness ratio, a, to the density and viscosity contrasts between the two layers, and to their two different internal heating rates in the form of an enrichment factor beta=1+2*a*H1/H, where H1 is the heating rate of the lower fluid and H is the average heating rate. We find that the lifetime of the lower enriched reservoir varies as beta**(-7/3) in the low
Dynamics of the cross flow heat exchanger for heating purposes
Energy Technology Data Exchange (ETDEWEB)
Mueller, K [Karlsruhe Univ. (TH) (Germany, F.R.). Inst. fuer Mess- und Regelungstechnik mit Maschinenlaboratorium
1980-09-01
A series of publications is available on the dynamic behaviour of heat exchangers (or heat transmitters, respectively), the subject of which is to deal with direct methods or with refined starting models for this general theme. The bridging between both these manners of advance remained as a problem. The author tried in his own investigation to solve the problem, and indeed by the selection of the correct starting model. He succeeded in this way, in that he removed conceptually a finned pipe from an arbitrary place of a heat exchanger and, furthermore, cut out from this particular pipe an arbitrary section. This section now does not stand alone for itself because the processes, which occur upstream of this section at the air-side and the water-side, are the input quantities of the section, which changes them due to its static and dynamic behaviour and emits them again as output quantities. The author, therefore, treats at first the dynamic behaviour of the section, which is represented in a signal flow diagram and which is used to derive approximate solutions from it. Furthermore, the author discusses the evident derivation of the total behaviour of heat exchangers.
Steady, three-dimensional, internally heated convection
International Nuclear Information System (INIS)
Schubert, G.; Glatzmaier, G.A.; Travis, B.
1993-01-01
Numerical calculations have been carried out of steady, symmetric, three-dimensional modes of convection in internally heated, infinite Prandtl number, Boussinesq fluids at a Rayleigh number of 1.4x10 4 in a spherical shell with inner/outer radius of 0.55 and in a 3x3x1 rectangular box. Multiple patterns of convection occur in both geometries. In the Cartesian geometry the patterns are dominated by cylindrical cold downflows and a broad hot upwelling. In the spherical geometry the patterns consist of cylindrical cold downwellings centered either at the vertices of a tetrahedron or the centers of the faces of a cube. The cold downflow cylinders are immersed in a background of upwelling within which there are cylindrical hot concentrations (plumes) and hot halos around the downflows. The forced hot upflow return plumes of internally heated spherical convection are fundamentally different from the buoyancy-driven plumes of heated from below convection
Postaccident heat removal. II. Heat transfer from an internally heated liquid to a melting solid
International Nuclear Information System (INIS)
Faw, R.E.; Baker, L. Jr.
1976-01-01
Microwave heating has been used in studies of heat transfer from a horizontal layer of internally heated liquid to a melting solid. Experiments were designed to simulate heat transfer and meltthrough processes of importance in the analysis of postaccident heat removal capabilities of nuclear reactors. Glycerin, heated by 2.45-GHz microwave radiation, was used to simulate molten fuel. Paraffin wax was used to simulate a melting barrier confining the fuel. Experimentally measured heat fluxes and melting rates were consistent with a model based on downward heat transfer by conduction through a stagnant liquid layer and upward heat transfer augmented by natural convection. Melting and displacement of the barrier material occurred by upward-moving droplets randomly distributed across the melting surface. Results indicated that the melting and displacement process had no effect on the heat transfer process
Heat flow and geothermal processes in Iceland
Flóvenz, Ólafur G.; Saemundsson, Kristján
1993-09-01
Heat flow values, derived from temperature measurements in shallow boreholes in Iceland, vary substantially across the country. The near-surface temperature gradients range from almost 0 to 500°C/km. The thermal conductivity of water-saturated rocks varies from 1.6 to 2.0 W/m°C. The temperature gradient in Iceland is mainly dependent on four factors: (1) the regional heat flow through the crust, (2) hydrothermal activity, (3) the permeability of the rock, and (4) residual heat in extinct volcanic centers. As Iceland is mainly made of basaltic material the radiogenic heat production is almost negligible. The thermal conductivity is, on the other hand, mainly influenced by the porosity of the rock; it increases as the porosity decreases. Iceland is made of sequences of flood basalts that formed within the volcanic rift zone—a continuation of the axis of the Mid-Atlantic ridge—and subsequently drifted sideways. Fresh basaltic lava is usually highly porous (30%) and fractured, and heat is mainly transported by convection. Therefore, a very low or even no temperature gradient is observed at shallow levels within the volcanic rift zone. As the basalt becomes buried the pores close due to lithostatic pressure and formation of secondary minerals. Below 500-1000 m depth in an uneroded lava pile, the heat is mainly transported by conduction. In the lowlands and valleys of Iceland outside the volcanic rift zone, 1000-1500 m of the original lava pile has been eroded, leaving thermal conduction as the most important heat transport mechanism. The regional temperature gradient has been measured in drillholes in dense and poorly permeable rocks away from the geothermal fields. The results show that the temperature gradient varies from 50 to 150°C/km. The highest values are found close to the volcanic rift zone and the gradient decreases with distance from the spreading axis. This result is mainly based on numerous shallow boreholes (60-500 m) but in some cases the results
Numerical analysis of fluid flow and heat transfer in a helical ...
African Journals Online (AJOL)
DR OKE
International Journal of Engineering, Science and Technology ... Numerical analysis of fluid flow and heat transfer in a helical rectangular .... by comparing the results of a conical spiral tube bundle modeled using the same software with that of.
Numerical simulation on coolant flow and heat transfer in core
International Nuclear Information System (INIS)
Yao Zhaohui; Wang Xuefang; Shen Mengyu
1997-01-01
To simulate the coolant flow and the heat transfer characteristics of a core, a computer code, THAPMA (Thermal Hydraulic Analysis Porous Medium Analysis) has been developed. In THAPMA code, conservation equations are based on a porous-medium formulation, which uses four parameters, i.e, volume porosity, directional surface porosity, distributed resistance, and distributed heat source (sink), to model the effects of fuel rods and other internal solid structures on flow and heat transfer. Because the scheme and the solution are very important in accuracy and speed of calculation, a new difference scheme (WSUC) has been used in the energy equation, and a modified PISO solution method have been employed to simulate the steady/transient states. The code has been proved reliable and can effectively solve the transient state problem by several numerical tests. According to the design of Qinshan NPP-II, the flow and heat transfer phenomena in reactor core have been numerically simulated. The distributions of the velocity and the temperature can provide a theoretical basis for core design and safety analysis
International Nuclear Information System (INIS)
Abou-Ziyan, Hosny Z.
2004-01-01
This paper presents the results of an experimental investigation of heat transfer from the heated bottom side of tee cross-section ducts to an internally flowing fluid. The idea of this work is derived from the cooling of critical areas in the cylinder heads of internal combustion engines. Fully developed single phase forced convection and subcooled flow boiling heat transfer data are reported. Six T-ducts of different width and height aspect ratios are tested with distilled water at velocities of 1, 2 and 3 m/s for bulk temperatures of 60 and 80 deg. C, while the heat flux was varied from about 80 to 700 kW/m 2 . The achieved data cover Reynolds numbers in the range of 5.22 x 10 4 to 2.36 x 10 5 , Prandtl numbers in the range from 2.2 to 3.0, duct width aspect ratio between 2.19 and 3.13 and duct height aspect ratio from 0.69 to 2.0. The results revealed that the increase in either the width or height aspect ratio of the T-ducts enhances the convection heat transfer coefficients and the boiling heat fluxes considerably. The following comparisons are provided for coolant velocity of 2 m/s, bulk temperature of 60 deg. C, wall superheat of 20 K and wall to bulk temperature difference of 20 K. As the width aspect ratio increases by 43%, the convection heat transfer coefficient and the boiling heat flux increase by 27% and 39%, respectively. An increase in the height aspect ratio by 290% enhances the convection heat transfer coefficient and the boiling heat fluxes by 82% and 103%, respectively. When the coolant velocity changes from 1 to 2 m/s, the heat transfer coefficient increases by 60% and the boiling heat flux rises by 62-98% for the various tested ducts. The convection heat transfer coefficient increases by 12% and the boiling heat flux decreases by 31% as the bulk fluid temperature rises from 60 to 80 deg. C. A correlation was developed for Nusselt number as a function of Reynolds number, Prandtl number, viscosity ratio and some aspect ratios of the T-duct
Lunar Global Heat Flow: Predictions and Constraints
Siegler, M.; Williams, J. P.; Paige, D. A.; Feng, J.
2017-12-01
The global thermal state of the Moon provides fundamental information on its bulk composition and interior evolution. The Moon is known to have a highly asymmetric surface composition [e.g. Lawrence et al., 2003] and crustal thickness [Wieczorek et al.,2012], which is suspected to result from interior asymmetries [Wieczorek and Phillips, 2000; Laneuville et al., 2013]. This is likely to cause a highly asymmetric surface heat flux, both past and present. Our understanding the thermal evolution and composition of the bulk moon therefore requires a global picture of the present lunar thermal state, well beyond our two-point Apollo era measurement. As on the on the Earth, heat flow measurements need to be taken in carefully selected locations to truly characterize the state of the planet's interior. Future surface heat flux and seismic observations will be affected by the presence of interior temperature and crustal radiogenic anomalies, so placement of such instruments is critically important for understanding the lunar interior. The unfortunate coincidence that Apollo geophysical measurements lie areas within or directly abutting the highly radiogenic, anomalously thin-crusted Procellarum region highlights the importance of location for in situ geophysical study [e.g. Siegler and Smrekar, 2014]. Here we present the results of new models of global lunar geothermal heat flux. We synthesize data from several recent missions to constrain lunar crustal composition, thickness and density to provide global predictions of the surface heat flux of the Moon. We also discuss implications from new surface heat flux constraints from the LRO Diviner Lunar Radiometer Experiment and Chang'E 2 Microwave Radiometer. We will identify areas with the highest uncertainty to provide insight on the placement of future landed geophysical missions, such as the proposed Lunar Geophysical Network, to better aim our future exploration of the Moon.
Internal and external axial corner flows
Kutler, P.; Shankar, V.; Anderson, D. A.; Sorenson, R. L.
1975-01-01
The inviscid, internal, and external axial corner flows generated by two intersecting wedges traveling supersonically are obtained by use of a second-order shock-capturing, finite-difference approach. The governing equations are solved iteratively in conical coordinates to yield the complicated wave structure of the internal corner and the simple peripheral shock of the external corner. The numerical results for the internal flows compare favorably with existing experimental data.
Heat transfer in two-phase flow of helium
International Nuclear Information System (INIS)
Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.
1986-01-01
The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data
Anomalous heat flow belt along the continental margin of Brazil
Hamza, Valiya M.; Vieira, Fabio P.; Silva, Raquel T. A.
2018-01-01
A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100-300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceará) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that "tectonic bonding" between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth's internal heat at shallow depths.
Flow and Heat Transfer Characteristics of Turbulent Gas Flow in Microtube with Constant Heat Flux
International Nuclear Information System (INIS)
Hong, Chungpyo; Matsushita, Shinichi; Ueno, Ichiro; Asako, Yutaka
2012-01-01
Local friction factors for turbulent gas flows in circular microtubes with constant wall heat flux were obtained numerically. The numerical methodology is based on arbitrary-Lagrangian-Eulerian method to solve two-dimensional compressible momentum and energy equations. The Lam-Bremhorst's Low-Reynolds number turbulence model was employed to calculate eddy viscosity coefficient and turbulence energy. The simulations were performed for a wide flow range of Reynolds numbers and Mach numbers with different constant wall heat fluxes. The stagnation pressure was chosen in such a way that the outlet Mach number ranged from 0.07 to 1.0. Both Darcy friction factor and Fanning friction factor were locally obtained. The result shows that the obtained both friction factors were evaluated as a function of Reynolds number on the Moody chart. The values of Darcy friction factor differ from Blasius correlation due to the compressibility effects but the values of Fanning friction factor almost coincide with Blasius correlation. The wall heat flux varied from 100 to 10000 W/m 2 . The wall and bulk temperatures with positive heat flux are compared with those of incompressible flow. The result shows that the Nusselt number of turbulent gas flow is different from that of incompressible flow.
2002-04-11
several smoke items deployed by the U.S. Army for both training and tactical missions. These formulations are essentially a mixture of potassium chlorate... polyacrylic rubber, and graphite were as listed in Table 1. Portions of the TA were substituted with PE, but the sum of the TA and PE was always 57...situation was true for other fuel I oxidizer combinations. Figures 8 through 11 show the results for the low temperature heating of sucrose I potassium
Thaw flow control for liquid heat transport systems
Kirpich, Aaron S.
1989-01-01
In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.
An Internally Heated Shape Memory Polymer Dry Adhesive
Directory of Open Access Journals (Sweden)
Jeffrey Eisenhaure
2014-08-01
Full Text Available A conductive epoxy-based shape memory polymer (SMP is demonstrated using carbon black (CB as a dopant for the purpose of creating an SMP dry adhesive system which can internally generate the heat required for activation. The electrical and mechanical properties of the CB/SMP blends for varying dopant concentrations are characterized. A composite adhesive is created to minimize surface contact resistance to conductive tape acting as electrodes, while maintaining bulk resistivity required for heat generation due to current flow. The final adhesive can function on flat or curved surfaces. As a demonstration, a 25 mm wide by 45 mm long dry adhesive strip is shown to heat evenly from an applied voltage, and can easily hold a mass in excess of 6 kg when bonded to a spherical concave glass surface using light pressure at 75 °C.
Heat transfer and fluid flow in minichannels and microchannels
Kandlikar, Satish; Li, Dongqing; Colin, Stephane; King, Michael R
2014-01-01
Heat exchangers with minichannel and microchannel flow passages are becoming increasingly popular due to their ability to remove large heat fluxes under single-phase and two-phase applications. Heat Transfer and Fluid Flow in Minichannels and Microchannels methodically covers gas, liquid, and electrokinetic flows, as well as flow boiling and condensation, in minichannel and microchannel applications. Examining biomedical applications as well, the book is an ideal reference for anyone involved in the design processes of microchannel flow passages in a heat exchanger. Each chapter is accompan
Augmentation of forced flow boiling heat transfer by introducing air flow into subcooled water flow
International Nuclear Information System (INIS)
Koizumi, Y.; Ohtake, H.; Yuasa, T.; Matsushita, N.
2001-01-01
The effect of air injection into a subcooled water flow on boiling heat transfer and a critical heat flux (CHF) was examined experimentally. Experiments were conducted in the range of subcooling of 50 K, a superficial velocity of water and air Ul = 0.17 ∼ 3.4 and Ug = 0 ∼ 15 m/s, respectively. A test heat transfer surface was a 5 mm wide, 40 mm long and 0.5 mm thick stainless steel sheet embedded on the bottom wall of a 10 mm high and 20 mm wide rectangular flow channel. Nine times enhancement of the heat transfer coefficient in the non-boiling region was attained at the most by introducing an air flow into a water single-phase flow. The heat transfer improvement was prominent when the water flow rate was low and the air introduction was large. The present results of the non-boiling heat transfer were well correlated with the Lockhart-Martinelli parameter X tt ; h TP /h L0 = 5.0(1/ X tt ) 0.5 . The air introduction has some effect on the augmentation of heat transfer in the boiling region, however, the two-phase flow effect was little and the boiling was dominant in the fully developed boiling region. The CHF was improved a little by the air introduction in the high water flow region. However, that was rather greatly reduced in the low flow region. Even so, the general trend by the air introduction was that qCHF increased as the air introduction was increased. The heat transfer augmentation in the non-boiling region was attained by less power increase than that in the case that only the water flow rate was increased. From the aspect of the power consumption and the heat transfer enhancement, the small air introduction in the low water flow rate region seemed more profitable, although the air introduction in the high water flow rate region and also the large air introduction were still effective in the augmentation of the heat transfer in the non-boiling region. (author)
An experimental investigation of turbulent flow heat transfer through ...
African Journals Online (AJOL)
An experimental investigation has been carried out to study the turbulent flow heat transfer and to determine the pressure drop characteristics of air, flowing through a tube with insert. An insert of special geometry is used inside the tube. The test section is electrically heated, and air is allowed to flow as the working fluid ...
Analysis of slip flow heat transfer between two unsymmetrically
Indian Academy of Sciences (India)
This paper presents an analytical investigation to study the heat transfer and fluid flow characteristics in the slip flow region for hydrodynamically and thermally fully developed flow between parallel plates.Both upper and lower plates are subjected to asymmetric heat flux boundary conditions. The effect of first ordervelocity ...
Internal heat exchange tubes for industrial furnaces
Energy Technology Data Exchange (ETDEWEB)
Hoetzl, M.; Lingle, T.M.
1992-05-26
This patent describes a method for cooling the work within an industrial furnace. It comprises providing a longitudinally extending outer tube which extends into the furnace having a closed axial end and an open axial end; providing a preformed inner tube open at both ends within the outer tube; injecting a coolant into the inner tube so that the coolant flows from one axial end of the tube out the opposite end adjacent the closed end of the outer tube, and from the closed end of the outer tube to the open end thereof; circulating a gas within the furnace against the outer tube to effect heat transfer therewith.
Thermodilution-determined Internal Jugular Venous Flow
DEFF Research Database (Denmark)
Rasmussen, Peter; Widmer, Mario; Hilty, Matthias P
2017-01-01
PURPOSE: Cerebral blood flow (CBF) increases ~20% during whole body exercise although a Kety-Schmidt-determined CBF is reported to remain stable; a discrepancy that could reflect evaluation of arterial vs. internal jugular venous (IJV) flow and/or that CBF is influenced by posture. Here we test...
Heat transfer and fluid flow in biological processes advances and applications
Becker, Sid
2015-01-01
Heat Transfer and Fluid Flow in Biological Processes covers emerging areas in fluid flow and heat transfer relevant to biosystems and medical technology. This book uses an interdisciplinary approach to provide a comprehensive prospective on biofluid mechanics and heat transfer advances and includes reviews of the most recent methods in modeling of flows in biological media, such as CFD. Written by internationally recognized researchers in the field, each chapter provides a strong introductory section that is useful to both readers currently in the field and readers interested in learning more about these areas. Heat Transfer and Fluid Flow in Biological Processes is an indispensable reference for professors, graduate students, professionals, and clinical researchers in the fields of biology, biomedical engineering, chemistry and medicine working on applications of fluid flow, heat transfer, and transport phenomena in biomedical technology. Provides a wide range of biological and clinical applications of fluid...
Visualisation of heat transfer in unsteady laminar flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2011-01-01
Heat transfer in fluid flows traditionally is examined in terms of temperature fields and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by
Boundary element method for internal axisymmetric flow
Directory of Open Access Journals (Sweden)
Gokhman Alexander
1999-01-01
Full Text Available We present an accurate fast method for the computation of potential internal axisymmetric flow based on the boundary element technique. We prove that the computed velocity field asymptotically satisfies reasonable boundary conditions at infinity for various types of inlet/exit. Computation of internal axisymmetric potential flow is an essential ingredient in the three-dimensional problem of computation of velocity fields in turbomachines. We include the results of a practical application of the method to the computation of flow in turbomachines of Kaplan and Francis types.
Analysis of the transient compressible vapor flow in heat pipes
Jang, J. H.; Faghri, A.; Chang, W. S.
1989-01-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.
Analysis of the transient compressible vapor flow in heat pipe
International Nuclear Information System (INIS)
Jang, J.H.; Faghri, A.; Chang, W.S.
1989-07-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures
Analysis of the transient compressible vapor flow in heat pipe
Jang, Jong Hoon; Faghri, Amir; Chang, Won Soon
1989-01-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.
Heat flow in the north-central Colorado Plateau
International Nuclear Information System (INIS)
Bodell, J.M.; Chapman, D.S.
1982-01-01
We report new heat flow measurements at 25 evenly distributed sites in the north-central Colorado Plateau. Heat flow values computed for these new sites and one previously published site range from 43 to 116 mW m -2 but fall into the following district subsets related to physiographic and tectonic elements within the Plateau: (1) heat flow of 51 mW m -2 (12 sites; s.d. 6) in the San Rafael Swell and Green River Desert which constitute the core of the Colorado Plateau at this latitude, (2) heat flows of 69 mW m -2 (5 sites; s.d. 10) in successive parallel north-south bands approaching the Wasatch Plateau to the west but still 80 km east of the Basin and Range physiographic boundary, (3) heat flow of 64 mW m -2 (5 sites; s.d. 2) along the Salt Anticline trend which strikes northwest in the region of Moab, Utah. Heat flow results for the entire Colorado Plateau have been reexamined in view of our new results, and the overall pattern supports the concept of a low heat flow 'thermal interior' for the plateau surrounded by a periphery some 100 km wide having substantially higher heat flow. Average heat flow in the thermal interior is about 60 mW m -2 compared to 80--90 mW m -2 in the periphery. This regional heat flow pattern supports a model of tertiary lithospheric thinning under the Colorado Plateau whereby the plateau is still in transient thermal response and a 15--20 m.y. lag between uplift and corresponding surface heat flow anomaly is to be expected. The position of the heat flow transition between our interior and peripheral regions in the northwest plateau is roughly consistent with lateral warming and weakening of the Colorado Plateau lithosphere initiated at the Basin and Range boundary some 20 m.y. ago
Heat transfer characteristics of alkali metals flowing across tube banks
International Nuclear Information System (INIS)
Sugiyama, K.; Ishiguro, R.; Kojima, Y.; Kanaoka, H.
2004-01-01
For the purpose of getting heat transfer coefficients of alkali metals flowing across tube banks at an acceptable level, we propose to use an inviscid-irrotational flow model, which is based on our flow visualization experiment. We show that the heat transfer coefficients obtained for the condition where only the test rod is heated in tube banks considerably differ from those obtained for the condition where all the rods are heated, because of interference between thick thermal boundary layers of alkali metals. We also confirm that the analytical values obtained by this flow model are in a reasonable agreement with experimental values. (author)
An analytical model for annular flow boiling heat transfer in microchannel heat sinks
International Nuclear Information System (INIS)
Megahed, A.; Hassan, I.
2009-01-01
An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)
Simulation of boiling flow in evaporator of separate type heat pipe with low heat flux
International Nuclear Information System (INIS)
Kuang, Y.W.; Wang, Wen; Zhuan, Rui; Yi, C.C.
2015-01-01
Highlights: • A boiling flow model in a separate type heat pipe with 65 mm diameter tube. • Nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux. • The two-phase heat transfer coefficient is less sensitive to the total mass flux. - Abstract: The separate type heat pipe heat exchanger is considered to be a potential selection for developing passive cooling spent fuel pool – for the passive pressurized water reactor. This paper simulates the boiling flow behavior in the evaporator of separate type heat pipe, consisting of a bundle of tubes of inner diameter 65 mm. It displays two-phase characteristic in the evaporation section of the heat pipe working in low heat flux. In this study, the two-phase flow model in the evaporation section of the separate type heat pipe is presented. The volume of fluid (VOF) model is used to consider the interaction between the ammonia gas and liquid. The flow patterns and flow behaviors are studied and the agitated bubbly flow, churn bubbly flow are obtained, the slug bubble is likely to break into churn slug or churn froth flow. In addition, study on the heat transfer coefficients indicates that the nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux, with the heat transfer coefficient being less sensitive to the total mass flux
Experimental study on flow pattern and heat transfer of inverted annular flow
International Nuclear Information System (INIS)
Takenaka, Nobuyuki; Akagawa, Koji; Fujii, Terushige; Nishida, Koji
1990-01-01
Experimental results are presented on flow pattern and heat transfer in the regions from inverted annular flow to dispersed flow in a vertical tube using freon R-113 as a working fluid at atmospheric pressure to discuss the correspondence between them. Axial distributions of heat transfer coefficient are measured and flow patterns are observed. The heat transfer characteristics are divided into three regions and a heat transfer characteristics map is proposed. The flow pattern changes from inverted annular flow (IAF) to dispersed flow (DF) through inverted slug flow (ISF) for lower inlet velocities and through agitated inverted annular flow (AIAF) for higher inlet velocities. A flow pattern map is obtained which corresponds well with the heat transfer characteristic map. (orig.)
House-internal heating systems; Husinterna vaermesystem
Energy Technology Data Exchange (ETDEWEB)
Johansson, Per-Olof; Wollerstrand, Janusz [Lund Univ. (Sweden). Dept. of Heat and Power Engineering
2005-07-01
In this report the placement of the circulation-pump in of waterborne radiator systems, as well as their filling and deairation are investigated. The study was done by literature studies and interviews with consultants and companies active on the HVAC-market. It was concluded that different placements of the pump in relationship to the heat exchanger exist, and the arguments for the choice of placement are varying. The main explanation of the choice of placement is that it is based on experience/or by practical reasons. The most important factor influencing the placement of the pump found, was how the pump is situated in relation to the expansion-tank. To maintain pressure in the whole system the expansion-tank should be placed on the suction side of the pump without any intermediate pressure-dropping devices in between. This placement ensures overpressure in the whole radiator-system and reduces the risk of unwanted leak in of air. To avoid cavitation sufficient static pressure on the suction side of the pump is necessary. The pressure increases with the temperature, which must be taken into consideration if the pump is placed on the warm side of the heat-exchanger. From this point of view a placement in the return-pipe from the radiator-system is to be preferred. Before advices for HVAC-branch regarding placement of the circulation-pump in the heating systems can be implemented, it is of big importance to analyse and clearly specify the advantages and disadvantages of a certain placement of the pump. There is a need of directions to get house-internal systems to operate properly together with district heating system. This is especially important when older heating systems with burners and shunt valves are being connected. Filling and deairation of the radiator system is of great importance for the function of the system. A radiator-system with significant level of air remains is difficult to adjust and will not work properly. Air in the radiators leads to
Compact, Deep-Penetrating Geothermal Heat Flow Instrumentation for Lunar Landers
Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.
2012-01-01
Geothermal heat flow is obtained as a product of the two separate measurements of geothermal gradient in, and thermal conductivity of, the vertical soi/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey [I] and previously the International Lunar Network [2]. The two lunar-landing missions planned later this decade by JAXA [3] and ESA [4] also consider geothermal measurements a priority.
Heat transfer measurements of internally heated liquids in cylindrical convection cells
International Nuclear Information System (INIS)
Fieg, G.
1978-10-01
In hypothetical reactor accidents, the thermohydraulic behaviour of core melts heated by the after-heat must be analyzed. For this purpose model experiments have been performed to study the stationary, natural convective heat transfer of internally heated fluids in cylindrical convertion cells investigating also the influence of geometry (aspect ratio) as well as of difference thermal wall conditions on to the heat transport characteristics. Axial temperature profiles, local heat flux densities at the vertical walls and their dependence, on the external Rayleigh number ar in detail reported, besides the Nusselt vs Rayleigh correlations for the aspect ratios HID=1 and 0,25. The results of these experiments are compared, as for ar possible, with existing thermohydraulic codes and simpler model asoumptions like the zone-model of Baker et. al. and after experimental verification, be used to study realistic PAHR situations. Velocity measurements by means of Laser-Doppler-Method yield information about the flow characteristics near the vertical walls and within the central part of the convecting fluid. (GL) [de
Entropy resistance analyses of a two-stream parallel flow heat exchanger with viscous heating
International Nuclear Information System (INIS)
Cheng Xue-Tao; Liang Xin-Gang
2013-01-01
Heat exchangers are widely used in industry, and analyses and optimizations of the performance of heat exchangers are important topics. In this paper, we define the concept of entropy resistance based on the entropy generation analyses of a one-dimensional heat transfer process. With this concept, a two-stream parallel flow heat exchanger with viscous heating is analyzed and discussed. It is found that the minimization of entropy resistance always leads to the maximum heat transfer rate for the discussed two-stream parallel flow heat exchanger, while the minimizations of entropy generation rate, entropy generation numbers, and revised entropy generation number do not always. (general)
Flow and heat transfer in laminar–turbulent transitional flow regime under rolling motion
International Nuclear Information System (INIS)
Yuan, Hongsheng; Tan, Sichao; Zhuang, Nailiang; Lan, Shu
2016-01-01
Highlights: • Flow and heat transfer experiment in transitional flow regime under rolling motion. • Increases of average friction factor and Nu were found. • Periodic breakdown of laminar flow contributes to the increase. • Nonlinear variation of pressure drop or Nu with Re also contributes to the increase. • Effect of critical Reynolds number shift was discussed. - Abstract: Flow and heat transfer characteristics under rolling motion are extremely important to thermohydraulic analysis of offshore nuclear reactors. An experimental study was conducted in a heated rectangular channel to investigate flow and heat transfer in laminar–turbulent transitional flow regime under rolling motion. The results showed that the average friction factor and Nusselt number are higher than that of the corresponding steady flow as the flow rate fluctuates in transitional flow regime. Larger relative flow rate fluctuation was observed under larger rolling amplitude or higher rolling frequency. In the same manner, larger increases of average friction factor and Nusselt number were achieved under larger rolling amplitude or higher rolling frequency. The increases were mainly caused by the flow rate fluctuation through periodic breakdown of laminar flow and development of turbulence in laminar–turbulent transitional flow regime. First, turbulence, which enhances the rate of momentum and energy exchange, occurs near the crest of flow rate wave even the flow is still in laminar flow regime according to the average Reynolds number. Second, as a result of rapid increases of the friction and heat transfer with Reynolds number in transitional flow regime, the increases of the friction and the heat transfer near the crest of flow rate wave are larger than the decreases of them near the trough of flow rate wave, which also contributes to increases of average friction and heat transfer. Additionally, the effect of critical Reynolds number shift under unsteady flow and heating
Preparation and Interpretation of Heat Flow Map of Turkey
International Nuclear Information System (INIS)
Ozturk, S.; Karli, R.; Destur, M.
2007-01-01
There exist a lot of data indicating our country takes place on an impotrant Kown heat flow anomaly. The preparation of a detailed 'Heat Flow Map' as a result of rational studies and depending upon this the determination of the distribution of heat in litosphere, except from the scientific benefits; shall enlighten subjects such as oil basen analysis, prospection of hydrothermal ores and earthquakes and further shall increase the feasibility of planning geothermal energy research.In between years 1995- 2005; as a part of project of the Geophysical Department of MTA with the purpose of preperation of Heat Flow Maps of Turkey, the heat flow measurments had been carried on at the convenient cold water wells. Using the Thermic and Gamma-Ray measurments and calculated conductivity coefficients of the representative rock samples of formation, heat flow map had been prepared. A distance of 10-30 km had been kept carefully betwen the wells of interest a total of 80204 m Thermic and Gamma-Ray logs and 420 rock samples from 695 wells, had been used in the study. Then according to the Lambert Projection, using the Surfer 8.02 and Grapher4 programmes The Heat Flow Maps of Turkey of scale 1:1000000 had been obtained.Some regional researches indicate that Turkey takes place in a part of Europe of high heat flux. Unfortunately there exist no detailed heat flow map of our country up to now. This shows the importance of present project
Critical heat flux in flow boiling in microchannels
Saha, Sujoy Kumar
2015-01-01
This Brief concerns the important problem of critical heat flux in flow boiling in microchannels. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to “Heat Transfer and Pressure Drop in Flow Boiling in Microchannels,” by the same author team, this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
Heat transfer in flow past a continuously moving porous flat plate with heat flux
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.; Sarma, Y.V.B.
The analysis of the heat transfer in flow past a continuously moving semi-infinite plate in the presence of suction/ injection with heat flux has been presented. Similarity solutions have been derived and the resulting equations are integrated...
A Prototype Flux-Plate Heat-Flow Sensor for Venus Surface Heat-Flow Determinations
Morgan, Paul; Reyes, Celso; Smrekar, Suzanne E.
2005-01-01
Venus is the most Earth-like planet in the Solar System in terms of size, and the densities of the two planets are almost identical when selfcompression of the two planets is taken into account. Venus is the closest planet to Earth, and the simplest interpretation of their similar densities is that their bulk compositions are almost identical. Models of the thermal evolution of Venus predict interior temperatures very similar to those indicated for the regions of Earth subject to solid-state convection, but even global analyses of the coarse Pioneer Venus elevation data suggest Venus does not lose heat by the same primary heat loss mechanism as Earth, i.e., seafloor spreading. The comparative paucity of impact craters on Venus has been interpreted as evidence for relatively recent resurfacing of the planet associated with widespread volcanic and tectonic activity. The difference in the gross tectonic styles of Venus and Earth, and the origins of some of the enigmatic volcano-tectonic features on Venus, such as the coronae, appear to be intrinsically related to Venus heat loss mechanism(s). An important parameter in understanding Venus geological evolution, therefore, is its present surface heat flow. Before the complications of survival in the hostile Venus surface environment were tackled, a prototype fluxplate heat-flow sensor was built and tested for use under synthetic stable terrestrial surface conditions. The design parameters for this prototype were that it should operate on a conforming (sand) surface, with a small, self-contained power and recording system, capable of operating without servicing for at least several days. The precision and accuracy of the system should be < 5 mW/sq m. Additional information is included in the original extended abstract.
Applications of thermoelectric modules on heat flow detection.
Leephakpreeda, Thananchai
2012-03-01
This paper presents quantitative analysis and practical scenarios of implementation of the thermoelectric module for heat flow detection. Mathematical models of the thermoelectric effects are derived to describe the heat flow from/to the detected media. It is observed that the amount of the heat flow through the thermoelectric module proportionally induces the conduction heat owing to the temperature difference between the hot side and the cold side of the thermoelectric module. In turn, the Seebeck effect takes place in the thermoelectric module where the temperature difference is converted to the electric voltage. Hence, the heat flow from/to the detected media can be observed from both the amount and the polarity of the voltage across the thermoelectric module. Two experiments are demonstrated for viability of the proposed technique by the measurements of the heat flux through the building wall and thermal radiation from the outdoor environment during daytime. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.
Analysis of the flow structure and heat transfer in a vertical mantle heat exchanger
DEFF Research Database (Denmark)
Knudsen, Søren; Morrison, GL; Behnia, M
2005-01-01
initially mixed and initially stratified inner tank and mantle. The analysis of the heat transfer showed that the flow in the mantle near the inlet is mixed convection flow and that the heat transfer is dependent on the mantle inlet temperature relative to the core tank temperature at the mantle level. (C......The flow structure inside the inner tank and inside the mantle of a vertical mantle heat exchanger was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the inner tank and in the mantle were measured using a Particle Image...... Velocimetry (PIV) system. A Computational Fluid Dynamics (CFD) model of the vertical mantle heat exchanger was also developed for a detailed evaluation of the heat flux at the mantle wall and at the tank wall. The flow structure was evaluated for both high and low temperature incoming flows and for both...
Low-Flow Film Boiling Heat Transfer on Vertical Surfaces
DEFF Research Database (Denmark)
Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.
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...... length, an average film boiling heat transfer coefficient is obtained....
Visualisation of heat transfer in 3D unsteady flows
Speetjens, M.F.M.; Steenhoven, van A.A.
2010-01-01
Heat transfer in fluid flows traditionally is examined in terms oftemperature field and heat-transfer coefficients at non-adiabaticwalls. However, heat transfer may alternatively be considered asthe transport of thermal energy by the total convective-conductiveheat flux in a way analogous to the
Analytical modeling for heat transfer in sheared flows of nanofluids
Ferrari, C.; Kaoui, B.; L'vov, V.S.; Procaccia, I.; Rudenko, O.; Thije Boonkkamp, ten J.H.M.; Toschi, F.
2012-01-01
We developed a model for the enhancement of the heat flux by spherical and elongated nanoparticles in sheared laminar flows of nanofluids. Besides the heat flux carried by the nanoparticles, the model accounts for the contribution of their rotation to the heat flux inside and outside the particles.
Flow dynamics of volume-heated boiling pools
International Nuclear Information System (INIS)
Ginsberg, T.; Jones, O.C.; Chen, J.C.
1979-01-01
Safety analyses of fast breeder reactors require understanding of the two-phase fluid dynamic and heat transfer characteristics of volume-heated boiling pool systems. Design of direct contact three-phase boilers, of practical interest in the chemical industries also requires understanding of the fundamental two-phase flow and heat transfer behavior of volume boiling systems. Several experiments have been recently reported relevant to the boundary heat-loss mechanisms of boiling pool systems. Considerably less is known about the two-phase fluid dynamic behavior of such systems. This paper describes an experimental investigation of the steady-state flow dynamics of volume-heated boiling pool systems
Heat transfer measurements of the 1983 kilauea lava flow.
Hardee, H C
1983-10-07
Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.
Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger
International Nuclear Information System (INIS)
Xue Ruojun; Deng Chengcheng; Li Chaojun; Wang Mingyuan
2012-01-01
In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)
Flowing and heat transfer characteristics of turbulent flow in typical rod bundles at rolling motion
International Nuclear Information System (INIS)
Yan Binghuo; Yu Lei; Gu Hanyang
2011-01-01
The influence mechanism of rolling motion on the flowing and heat transfer characteristics of turbulent flow in typical four rod bundles was investigated with Fluent code. The flowing and heat transfer characteristics of turbulent flow in rod bundles can be affected by rolling motion. But the flowing similarity of turbulent flow in adiabatic and non-adiabatic can not be affected. If the rolling period is small, the radial additional force can make the parameter profiles, the turbulent flowing and heat transfer change greatly. At rolling motion, as the pitch to diameter ratio decreases, especially if it is less than 1.1, the flowing and heat transfer of turbulent flow at rolling motion change significantly. The variation of pitch to diameter ratio can change the profiles of secondary flow and turbulent kinetic energy in cross-section greatly. (authors)
Heat transfer and pressure drop in flow boiling in microchannels
Saha, Sujoy Kumar
2016-01-01
This Brief addresses the phenomena of heat transfer and pressure drop in flow boiling in micro channels occurring in high heat flux electronic cooling. A companion edition in the Springer Brief Subseries on Thermal Engineering and Applied Science to “Critical Heat Flux in Flow Boiling in Micro channels,” by the same author team, this volume is idea for professionals, researchers and graduate students concerned with electronic cooling.
International Nuclear Information System (INIS)
Nourgaliev, R.R.; Dinh, A.T.; Dinh, T.N.; Sehgal, B.R.
1999-01-01
This paper presents results of numerical investigation of turbulent natural convection in an internally-heated oxidic pool, and in a metallic layer heated from below and cooled from top and sidewalls. Emphasis is placed upon applicability of the existing heat transfer correlations (obtained from simulant-material experiments) in assessments of a prototypic severe reactor accident. The objectives of this study are (i) to improve the current understanding of the physics of unstably stratified flows, and (ii) to reduce uncertainties associated with modeling and assessment of natural convection heat transfer in the above configuration. Prediction capabilities of different turbulence modeling approaches are first examined and discussed, based on extensive results of numerical investigations performed by present authors. Findings from numerical modeling of turbulent natural convection flow and heat transfer in melt pools and metallic layers are then described. (authors)
Estimation of respiratory heat flows in prediction of heat strain among Taiwanese steel workers.
Chen, Wang-Yi; Juang, Yow-Jer; Hsieh, Jung-Yu; Tsai, Perng-Jy; Chen, Chen-Peng
2017-01-01
International Organization for Standardization 7933 standard provides evaluation of required sweat rate (RSR) and predicted heat strain (PHS). This study examined and validated the approximations in these models estimating respiratory heat flows (RHFs) via convection (C res ) and evaporation (E res ) for application to Taiwanese foundry workers. The influence of change in RHF approximation to the validity of heat strain prediction in these models was also evaluated. The metabolic energy consumption and physiological quantities of these workers performing at different workloads under elevated wet-bulb globe temperature (30.3 ± 2.5 °C) were measured on-site and used in the calculation of RHFs and indices of heat strain. As the results show, the RSR model overestimated the C res for Taiwanese workers by approximately 3 % and underestimated the E res by 8 %. The C res approximation in the PHS model closely predicted the convective RHF, while the E res approximation over-predicted by 11 %. Linear regressions provided better fit in C res approximation (R 2 = 0.96) than in E res approximation (R 2 ≤ 0.85) in both models. The predicted C res deviated increasingly from the observed value when the WBGT reached 35 °C. The deviations of RHFs observed for the workers from those predicted using the RSR or PHS models did not significantly alter the heat loss via the skin, as the RHFs were in general of a level less than 5 % of the metabolic heat consumption. Validation of these approximations considering thermo-physiological responses of local workers is necessary for application in scenarios of significant heat exposure.
Exhaust bypass flow control for exhaust heat recovery
Reynolds, Michael G.
2015-09-22
An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.
Cryogenic Heat Exchanger with Turbulent Flows
Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard
2012-01-01
An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…
CHF multiplier of subcooled flow boiling for non-uniform heating conditions in swirl tube
International Nuclear Information System (INIS)
Inasaka, F.; Nariai, H.
1994-01-01
The high heat flux components of fusion reactors, such as divertor plates and beam dumps of neutral beam injectors, are estimated to be subjected to very high heat loads more than 10 MW/m 2 . Critical heat flux (CHF), which determines the upper limit of heat removal, is one of the most important problems in designing cooling systems. For practical applications in cooling systems, subcooled flow boiling in water combined with swirl-flow in tubes with internal twisted tape is thought to be the most superior for CHF characteristics in fusion reactor components, heat by irradiation comes in from one side of the wall, and cooling channel is then under circumferentially non-uniform heating condition. Authors have conducted the experiments on the CHF with internal twisted tapes under circumferentially non-uniform heating conditions and showed that when the intensity of non-uniformity increased, q cH (peak heat flux at burnout under nonuniform heating condition) in tube with internal twisted tape increased above the q c,unif (CHF under uniform heating condition), though the average qualities were the same for both cases. They also showed that this CHF enhancement was not seen in smooth tubes without tape under the same average qualities
Thermal performance modeling of cross-flow heat exchangers
Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria
2014-01-01
This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges
Heat Source Models in Simulation of Heat Flow in Friction Stir Welding
DEFF Research Database (Denmark)
Schmidt, Henrik Nikolaj Blich; Hattel, Jesper
2004-01-01
The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in Friction Stir Welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms....... The convective heat transfer due to the material flow affects the temperature fields. Models presented previously in literature allow the heat to flow through the probe volume, and the majority of them neglect the influence of the contact condition as the sliding condition is assumed. In the present work......, a number of cases are established. Each case represents a combination of a contact condition, i.e. sliding and sticking, and a stage of refinement regarding the heat source distribution. In the most detailed models the heat flow is forced around the probe volume by prescribing a velocity field in shear...
Heat source models in simulation of heat flow in friction stir welding
DEFF Research Database (Denmark)
Schmidt, Henrik Nikolaj Blich; Hattel, Jesper
2004-01-01
The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in friction stir welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms....... The convective heat transfer due to the material flow affects the temperature fields. Models presented previously in the literature allow the heat to flow through the probe volume, and the majority neglects the influence of the contact condition as the sliding condition is assumed. In this work, a number...... of cases is established. Each case represents a combination of a contact condition, i.e. sliding and sticking, and a stage of refinement regarding the heat source distribution. In the most detailed models, the heat flow is forced around the probe volume by prescribing a velocity field in shear layers...
Heating patterns during cancer heat therapy as a function of blood flow
International Nuclear Information System (INIS)
Mendecki, J.; Friedenthal, E.; Botstein, C.; Sterzer, F.; Paglione, R.W.
1984-01-01
Heating patterns as a function of regional blood flow were evaluated in healthy tissues with different vascular characteristics as well as in a variety of tumors submitted to microwave and RF-induced hyperthermia. Generally, faster heating and slower cooling was demonstrated for tumors. Definite correlation was found between the power needed to heat given tissue volume to a specific temperature and the ability of this tissue to dissipate heat via vascular flow. The measurements show that during the early phase of heating of tumors temperature rises slowly up to about 40 0 C. indicating good heat exchanges but that at this level rapid increase of temperature occurs for relatively small increments of power input. It is suggested that blood flow in malignant tissue remains competent and responsive to low grade heating, but that at higher temperature levels, in contrast to normal tissue, tumor blood flow rapidly decreases indicating compromised vascular system. Implication for treatment protocols are discussed
Experimental investigation on Heat Transfer Performance of Annular Flow Path Heat Pipe
International Nuclear Information System (INIS)
Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol
2015-01-01
Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heat pipe design cases was studied to determine the heat pipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heat pipes, and the transient performance of high temperature sodium heat pipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heat pipes cooling system using loop heat pipes for decay heat removal cooling and analysis of heat pipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heat pipe is the combination of the heat pipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heat pipe containing neutron absorber material, B 4 C. The main objective is to investigate the effect of the inner structure in heat pipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B 4 C pellet as cylindrical structures. The thermal performances of each heat pipes were measured experimentally. Among them, concentric heat pipe showed the best performance compared with others. 1. Annular evaporation section heat pipe and annular flow path heat pipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer coefficient of
Heat transfer and flow structure evaluation of a synthetic jet emanating from a planar heat sink
International Nuclear Information System (INIS)
Manning, Paul; Persoons, Tim; Murray, Darina
2014-01-01
Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.
International Nuclear Information System (INIS)
Vitorello, I.
1978-01-01
Heat flow and heat production results are reported from nineteen widely spaced sites in eastern and central parts of Brazil. Three sites in the stable Sao Francisco Craton comprising rocks with Transamazonic ages (2600 to 1800 Ma) or older present an average heat flow of 41.8 +- 4.6 (standard error of the mean=sem) mW m -2 , typical of shield areas; eight sites located in the Late Precambrian Braziliane metamorphic belt have an average heat flow of 54.7 +- 3.8 (sem) mW m -2 ; and four sites in the Parana basin, locus of a Late Jurassic-Early Cretaceous basaltic volcanicity, have a mean heat flow of 70.1 +- 5.9 (sem) mW m -2 . Heat flow results from the Late Cretaceous-Early Tertiary alkalic intrusion of Pocos de Caldas have yielded a site mean of 55.3 mW m -2 . These results indicate a systematic decrease of heat flow with increasing age of the last tectonothermal event. As an explanation for this pattern, a model comprising three main heat flow components is advanced: radiogenic heat from the crust (40%), with the decrease of this contribution with time being achieved by erosional removal of radioactive material; a residual heat from a transient thermal perturbation associated with tectogenesis; and a uniform heat flow of about 28 mW m -2 from deeper sources. The Coastal Brazilian Shield is characterized by ordinary surface and reduced heat flow, but its heat production appears to be less concentrated near the surface, and distributed over a greater depth. Because of the variation in plate thickness, relative movements between the South American plate and the underlying mantle material are possibly constrained to depths exceeding 400 km
Flow and heat transfer in a curved channel
Brinich, P. F.; Graham, R. W.
1977-01-01
Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.
Heat transfer and flow characteristics on a gas turbine shroud.
Obata, M; Kumada, M; Ijichi, N
2001-05-01
The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.
Heat flow during sawtooth collapse in tokamak plasmas
International Nuclear Information System (INIS)
Hanada, Kazuaki
1994-01-01
Heat flow during sawtooth collapse was studied on the WT-3 tokamak by using temporal evolution of soft X-ray intensity profile in the poloidal cross section in a lower hybrid current driven plasma as well as an electron cyclotron heated plasma. Two phase in sawtooth collapses were observed. In the first phases, the hottest spot that is the peak of the soft X-ray distribution approaches the inversion surface and heat flows out through a narrow gate on the inversion surface. In the second phase, the hottest spot stays on the inversion surface, and heat flows out through the whole inversion surface. This suggests that magnetic reconnection as predicted by Kadomtsev's model occurs in the first phase, but in the second phase, a different mechanism dominates heat flow. (author)
Temperature-gated thermal rectifier for active heat flow control.
Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang
2014-08-13
Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage.
Piezoelectric Energy Harvesting in Internal Fluid Flow
Directory of Open Access Journals (Sweden)
Hyeong Jae Lee
2015-10-01
Full Text Available We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA showed fatigue failure was imminent due to stress concentrations near the bimorph’s clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well.
Piezoelectric energy harvesting in internal fluid flow.
Lee, Hyeong Jae; Sherrit, Stewart; Tosi, Luis Phillipe; Walkemeyer, Phillip; Colonius, Tim
2015-10-14
We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph's clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well.
Multiple flow patterns and heat transfer in confined jet impingement
International Nuclear Information System (INIS)
Li Xianchang; Gaddis, J. Leo; Wang Ting
2005-01-01
The flow field of a 2-D laminar confined impinging slot jet is investigated. Numerical results indicate that there exist two different solutions in some range of geometric and flow parameters. The two steady flow patterns are obtained under identical boundary conditions but only with different initial flow fields. Two different exit boundary conditions are investigated with two commercial software packages to eliminate artificial or computational effects. The different flow patterns are observed to significantly affect the heat transfer. A flow visualization experiment is carried out to verify the computational results and both flow patterns are observed. The bifurcation mechanism is interpreted and discussed
First international workshop on fundamental aspects of post-dryout heat transfer: proceedings
International Nuclear Information System (INIS)
Lee, R.
1984-12-01
The purpose of the First International Workshop on Fundamental Aspects of Post-Dryout Heat Transfer was to review recent developments and the state of art in the field of post-dryout heat transfer. The workshop centered on interchanging ideas, reviewing current research results, and defining future research needs. The following five sessions dealing with the fundamental aspects of post-dryout heat transfer were held. A Computer Code Modeling and Flow Phenomena session was held dealing with flow rgimes, drop size, drop formation and behavior, interfacial area, interfacial drag, and computer modeling. A Quenching Phenomena session was held dealing with nature of rewetting, maximum wetting temperature, Leidenfrost phenomenon and heat transfer in the vicinity of quench front. A Low-Void Heat Transfer session was held dealing with inverted annular-flow heat transfer, inverted slug-flow heat transfer thermal non-equilibrium and computer modeling. A Dispersed-Flow Heat Transfer session was held dealing with drop interfacial heat transfer, vapor convection, thermal non-equilibrium and correlations and models
A simplified method of calculating heat flow through a two-phase heat exchanger
Energy Technology Data Exchange (ETDEWEB)
Yohanis, Y.G. [Thermal Systems Engineering Group, Faculty of Engineering, University of Ulster, Newtownabbey, Co Antrim, BT37 0QB Northern Ireland (United Kingdom)]. E-mail: yg.yohanis@ulster.ac.uk; Popel, O.S. [Non-traditional Renewable Energy Sources, Institute for High Temperatures, Russian Academy of Sciences, 13/19 Izhorskaya str., IVTAN, Moscow 125412 (Russian Federation); Frid, S.E. [Non-traditional Renewable Energy Sources, Institute for High Temperatures, Russian Academy of Sciences, 13/19 Izhorskaya str., IVTAN, Moscow 125412 (Russian Federation)
2005-10-01
A simplified method of calculating the heat flow through a heat exchanger in which one or both heat carrying media are undergoing a phase change is proposed. It is based on enthalpies of the heat carrying media rather than their temperatures. The method enables the determination of the maximum rate of heat flow provided the thermodynamic properties of both heat-carrying media are known. There will be no requirement to separately simulate each part of the system or introduce boundaries within the heat exchanger if one or both heat-carrying media undergo a phase change. The model can be used at the pre-design stage, when the parameters of the heat exchangers may not be known, i.e., to carry out an assessment of a complex energy scheme such as a steam power plant. One such application of this model is in thermal simulation exercises within the TRNSYS modeling environment.
A simplified method of calculating heat flow through a two-phase heat exchanger
International Nuclear Information System (INIS)
Yohanis, Y.G.; Popel, O.S.; Frid, S.E.
2005-01-01
A simplified method of calculating the heat flow through a heat exchanger in which one or both heat carrying media are undergoing a phase change is proposed. It is based on enthalpies of the heat carrying media rather than their temperatures. The method enables the determination of the maximum rate of heat flow provided the thermodynamic properties of both heat-carrying media are known. There will be no requirement to separately simulate each part of the system or introduce boundaries within the heat exchanger if one or both heat-carrying media undergo a phase change. The model can be used at the pre-design stage, when the parameters of the heat exchangers may not be known, i.e., to carry out an assessment of a complex energy scheme such as a steam power plant. One such application of this model is in thermal simulation exercises within the TRNSYS modeling environment
Development of Compact, Modular Lunar Heat Flow Probes
Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.
2014-01-01
Geothermal heat flow measurements are a high priority for the future lunar geophysical network missions recommended by the latest Decadal Survey and previously the International Lunar Network. Because the lander for such a mission will be relatively small, the heat flow instrumentation must be a low-mass and low-power system. The instrument needs to measure both thermal gradient and thermal conductivity of the regolith penetrated. It also needs to be capable of excavating a deep enough hole (approx. 3 m) to avoid the effect of potential long-term changes of the surface thermal environment. The recently developed pneumatic excavation system can largely meet the low-power, low-mass, and the depth requirements. The system utilizes a stem which winds out of a pneumatically driven reel and pushes its conical tip into the regolith. Simultaneously, gas jets, emitted from the cone tip, loosen and blow away the soil. The thermal sensors consist of resistance temperature detectors (RTDs) embedded on the stem and an insitu thermal conductivity probe attached to the cone tip. The thermal conductivity probe consists of a short 'needle' (2.4-mm diam. and 15- to 20-mm length) that contains a platinum RTD wrapped in a coil of heater wire. During a deployment, when the penetrating cone reaches a desired depth, it stops blowing gas, and the stem pushes the needle into the yet-to-be excavated, undisturbed bottom soil. Then, it begins heating and monitors the temperature. Thermal conductivity of the soil can determined from the rate of temperature increase with time. When the measurement is complete, the system resumes excavation until it reaches the next targeted depth.
International Workshop on Traffic and Granular Flow
Herrmann, Hans; Schreckenberg, Michael; Wolf, Dietrich; Social, Traffic and Granular Dynamics
2000-01-01
"Are there common phenomena and laws in the dynamic behavior of granular materials, traffic, and socio-economic systems?" The answers given at the international workshop "Traffic and Granular Flow '99" are presented in this volume. From a physical standpoint, all these systems can be treated as (self)-driven many-particle systems with strong fluctuations, showing multistability, phase transitions, non-linear waves, etc. The great interest in these systems is due to several unexpected new discoveries and their practical relevance for solving some fundamental problems of today's societies. This includes intelligent measures for traffic flow optimization and methods from "econophysics" for stabilizing (stock) markets.
Heat transfer critical conditions in two-plase flow
International Nuclear Information System (INIS)
Assis, M.C.V. de.
1980-02-01
The critical heat flux for forced-convection flow of water inside an uniformly heated circular channel is analysed, taking into account several flow patterns usually met in this type of investigation. Comments about nomenclature, experimental methods and influence of operational parameters used in the description of this phenomenon are made. The experimental results from 187 tests of critical heat flux at low pressure are presented. One empirical correlation between the critical heat flux and the independent parameters, was developed. Some correlations developed in other laboratories in the same range of parameters are mentioned and compared with present one. (Author) [pt
Holographic aids for internal combustion engine flow studies
Regan, C.
1984-01-01
Worldwide interest in improving the fuel efficiency of internal combustion (I.C.) engines has sparked research efforts designed to learn more about the flow processes of these engines. The flow fields must be understood prior to fuel injection in order to design efficient valves, piston geometries, and fuel injectors. Knowledge of the flow field is also necessary to determine the heat transfer to combustion chamber surfaces. Computational codes can predict velocity and turbulence patterns, but experimental verification is mandatory to justify their basic assumptions. Due to their nonintrusive nature, optical methods are ideally suited to provide the necessary velocity verification data. Optical sytems such as Schlieren photography, laser velocimetry, and illuminated particle visualization are used in I.C. engines, and now their versatility is improved by employing holography. These holographically enhanced optical techniques are described with emphasis on their applications in I.C. engines.
Internal wave structures in abyssal cataract flows
Makarenko, Nikolay; Liapidevskii, Valery; Morozov, Eugene; Tarakanov, Roman
2014-05-01
We discuss some theoretical approaches, experimental results and field data concerning wave phenomena in ocean near-bottom stratified flows. Such strong flows of cold water form everywhere in the Atlantic abyssal channels, and these currents play significant role in the global water exchange. Most interesting wave structures arise in a powerful cataract flows near orographic obstacles which disturb gravity currents by forced lee waves, attached hydraulic jumps, mixing layers etc. All these effects were observed by the authors in the Romanche and Chain fracture zones of Atlantic Ocean during recent cruises of the R/V Akademik Ioffe and R/V Akademik Sergei Vavilov (Morozov et al., Dokl. Earth Sci., 2012, 446(2)). In a general way, deep-water cataract flows down the slope are similar to the stratified flows examined in laboratory experiments. Strong mixing in the sill region leads to the splitting of the gravity current into the layers having the fluids with different densities. Another peculiarity is the presence of critical layers in shear flows sustained over the sill. In the case under consideration, this critical level separates the flow of near-bottom cold water from opposite overflow. In accordance with known theoretical models and laboratory measurements, the critical layer can absorb and reflect internal waves generated by the topography, so the upward propagation of these perturbations is blocked from above. High velocity gradients were registered downstream in the vicinity of cataract and it indicates the existence of developed wave structures beyond the sill formed by intense internal waves. This work was supported by RFBR (grants No 12-01-00671-a, 12-08-10001-k and 13-08-10001-k).
Flow-excursion-induced dryout at low-heat-flux
International Nuclear Information System (INIS)
Khatib-Rahbar, M.; Cazzoli, E.G.
1983-01-01
Flow-excursion-induced dryout at low-heat-flux natural-convection boiling, typical of liquid-metal fast-breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of Ledinegg instability leading to flow excursion and subsequent dryout in agreement with experimental data. A flow-regime-dependent dryout heat flux relationship based upon saturated boiling criterion is also presented. Transient analysis indicates that premature flow excursion can not be ruled out and sodium boiling is highly transient dependent. Analysis of a high-heat-flux forced convection, loss-of-flow transient shows a significantly faster flow excursion leading to dryout in excellent agreement with parallel calculations using the two-dimensional THORAX code. 17 figures
The optimization of longitudinal convective fins with internal heat generation
International Nuclear Information System (INIS)
Razelos, P.
1979-01-01
The solution of the optimization problem for longitudinal convective fins of constant thickness, triangular or parabolic profile, and uniform internal heat generation, is presented. The cases considered are those of a given heat generation density, total heat generation and heat generation per unit width of the fin, when either the heat dissipation or the width of the fin is prescribed. The results are set forth in a nondimensional form, which are presented graphically. The effect of the fin's thermal conductivity upon the optimum dimensions is discussed, and limiting values for the heat generation and the heat dissipation, which may be imposed on the fin for a feasible optimization, are also obtained. (Auth.)
Predicting critical heat flux in slug flow regime of uniformly heated ...
African Journals Online (AJOL)
Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (CHF) of forced convective flow of water in a vertical heated channel. The code was based on the liquid sub-layer model, with the assumption that CHF occurred when the liquid film thickness between the heated surface and vapour ...
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
Flow film boiling heat transfer in water and Freon-113
International Nuclear Information System (INIS)
Liu, Qiusheng; Shiotsu, Masahiro; Sakurai, Akira
2002-01-01
Experimental apparatus and method for film boiling heat transfer measurement on a horizontal cylinder in forced flow of water and Freon-113 under pressurized and subcooled conditions were developed. The experiments of film boiling heat transfer from single horizontal cylinders with diameters ranging from 0.7 to 5 mm in saturated and subcooled water and Freon-113 flowing upward perpendicular to the cylinders were carried out for the flow velocities ranging from 0 to 1 m/s under system pressures ranging from 100 to 500 kPa. Liquid subcoolings ranged from 0 to 50 K, and the cylinder surface superheats were raised up to 800 K for water and 400 K for Freon-113. The film boiling heat transfer coefficients obtained were depended on surface superheats, flow velocities, liquid subcoolings, system pressures and cylinder diameters. The effects of these parameters were systematically investigated under wider ranges of experimental conditions. It was found that the heat transfer coefficients are higher for higher flow velocities, subcoolings, system pressures, and for smaller cylinder diameters. The observation results of film boiling phenomena were obtained by a high-speed video camera. A new correlation for subcooled flow film boiling heat transfer was derived by modifying authors' correlation for saturated flow film boiling heat transfer with authors' experimental data under wide subcooled conditions. (author)
Heat transfer in a counterflow heat exchanger at low flow rates
International Nuclear Information System (INIS)
Hashimoto, A.; Hattori, N.; Naruke, K.
1995-01-01
A study was made of heat transfer in a double-tube heat exchanger at low flow rates of water. The temperatures of fluid and tube walls in the axial direction of tube were measured precisely at flow rate ratios of annulus to inner tube (or flow rate ratios of inner tube to annulus W i /W a , Re i approx. = 80 - 4000), W a /W i =0.1 - 1.1. In parallel with experiment, numerical calculation for forced-convection heat transfer was also carried out for laminar flows in the same tube configuration as experiment. Average over-all coefficients of heat transfer, obtained by experiments, indicate the same characteristics as numerical calculation in the examined range of flow rate ratio. Their experimental values, however, are somewhat larger than those of calculation at small values of flow rate ratio. (author)
Fluid flow and heat transfer in rotating porous media
Vadasz, Peter
2016-01-01
This Book concentrates the available knowledge on rotating fluid flow and heat transfer in porous media in one single reference. Dr. Vadasz develops the fundamental theory of rotating flow and heat transfer in porous media and introduces systematic classification and identification of the relevant problems. An initial distinction between rotating flows in isothermal heterogeneous porous systems and natural convection in homogeneous non-‐isothermal porous systems provides the two major classes of problems to be considered. A few examples of solutions to selected problems are presented, highlighting the significant impact of rotation on the flow in porous media.
Analysis on flow characteristic of nuclear heating reactor
International Nuclear Information System (INIS)
Jiang Shengyao; Wu Xinxin
1997-06-01
The experiment was carried out on the test loop HRTL-5, which simulates the geometry and system design of a 5 MW Nuclear heating reactor. The analysis was based on a one-dimensional two-phase flow drift model with conservation equations for mass, steam mass, energy and momentum. Clausius-Clapeyron equation was used for the calculation of flashing front in the riser. A set of ordinary equation, which describes the behavior of two-phase flow in the natural circulation system, was derived through integration of the above conservation equations in subcooled boiling region, bulk boiling region in the heated section and in the riser. The method of time-domain was used for the calculation. Both static and dynamic results are presented. System pressure, inlet subcooling and heat flux are varied as input parameters. The results show that, firstly, subcooled boiling in the heated section and void flashing in the riser have significant influence on the distribution of the void fraction, mass flow rate and stability of the system, especially at lower pressure, secondly, in a wide range of two-phase flow conditions, only subcooled boiling occurs in the heated section. For the designed two-phase regime operation of the 5 MW nuclear heating reactor, the temperature at the core exit has not reaches its saturation value. Thirdly, the mechanism of two-phase flow oscillation, namely, 'zero-pressure-drop', is described. In the wide range of inlet subcooling (0 K<ΔT<28 K) there exists three regions for system flow condition, namely, (1) stable two-phase flow, (2) bulk and subcooled boiling unstable flow, (3) subcooled boiling and single phase stable flow. The response of mass flow rate, after a small disturbance in the heat flux, is showed in the above inlet subcooling range, and based on it the instability map of the system is given through experiment and calculation. (3 refs., 9 figs.)
International Nuclear Information System (INIS)
Liu, Qiusheng; Fukuda, Katsuya
2003-01-01
The transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured under wide experimental conditions. The platinum cylinder with a diameter of 1.0 mm was used as test heater and heated by electric current with an exponentially increasing heat input of Q 0 exp(t/τ). The gas flow velocities ranged from 5 to 35 m/s, the gas temperatures ranged from 25 to 80degC, and the periods of heat generation rate, τ, ranged from 40 ms to 20 s. The surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The transient heat transfer shows less dependence on the gas flowing velocity when the period becomes very shorter. The gas temperature in this study shows little influence on the heat transfer coefficient. Semi-empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data. The ratios of transient Nusselt number Nu tr to quasi-steady-state Nusselt number Nu st at various periods, flow velocities, and gas temperatures were obtained. The heat transfer shifts to the quasi-steady-state heat transfer for longer periods and shifts to the transient heat transfer for shorter periods at the same flow velocity. It also approaches the quasi-steady-state one for higher flow velocity at the same period. Empirical correlation for transient heat transfer was also obtained based on the experimental data. (author)
RISKS AND CONTRADICTORY OF INTERNATIONAL CAPITAL FLOWS IN BANKING
Directory of Open Access Journals (Sweden)
V. Shevchenko
2014-03-01
Full Text Available The content of the international capital flows are studied, its contradictor influence on global and national processes. Some theoretical approaches on contradictory impact of capital flows. The major risks of international capital flows in banking sector are determined including financial, currency, assets value decrease, credit rating etc. The capital flows reversal flows are explained. The modern changes of international capital flows to banking sector of Ukraine are discovered.
Frictional strength and heat flow of southern San Andreas Fault
Zhu, P. P.
2016-01-01
Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault
Critical heat flux and exit film flow rate in a flow boiling system
International Nuclear Information System (INIS)
Ueda, Tatsuhiro; Isayama, Yasushi
1981-01-01
The critical heat flux in a flowing boiling system is an important problem in the evaporating tubes with high thermal load such as nuclear reactors and boilers, and gives the practical design limit. When the heat flux in uniformly heated evaporating tubes is gradually raised, the tube exit quality increases, and soon, the critical heat flux condition arises, and the wall temperature near tube exit rises rapidly. In the region of low exit quality, the critical heat flux condition is caused by the transition from nucleating boiling, and in the region of high exit quality, it is caused by dry-out. But the demarcation of both regions is not clear. In this study, for the purpose of obtaining the knowledge concerning the critical heat flux condition in a flowing boiling system, the relation between the critical heat flux and exit liquid film flow rate was examined. For the experiment, a uniformly heated vertical tube supplying R 113 liquid was used, and the measurement in the range of higher heating flux and mass velocity than the experiment by Ueda and Kin was carried out. The experimental setup and experimental method, the critical heat flux and exit quality, the liquid film flow rate at heating zone exit, and the relation between the critical heat flux and the liquid film flow rate at exit are described. (Kako, I.)
The effects of radiogenic heat on groundwater flow
International Nuclear Information System (INIS)
Beddoes, R.J.; Tammemagi, H.Y.
1986-03-01
The effects of radiogenic heat released by a nuclear waste repository on the groundwater flow in the neighbouring rock mass is reviewed. The report presents an overview of the hydrogeologic properties of crystalline rocks in the Canadian Shield and also describes the mathematical theory of groundwater flow and heat transfer in both porous media and fractured rock. Numerical methods for the solution of the governing equations are described. A number of case histories are described where analyses of flow systems have been performed both with and without radiogenic heat sources. A number of relevant topics are reviewed such as the role of the porous medium model, boundary conditions and, most importantly, the role of complex coupled processes where the effects of heat and water flow are intertwined with geochemical and mechanical processes. The implications to radioactive waste disposal are discussed
Enhanced two phase flow in heat transfer systems
Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D
2013-12-03
A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1996-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators
Energy Technology Data Exchange (ETDEWEB)
Yanagihara, J I; Rodriques, R Jr [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering
1997-12-31
Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)
Heat transfer in window frames with internal cavities
Energy Technology Data Exchange (ETDEWEB)
Gustavsen, Arild
2001-07-01
Heat transfer in window frames with internal air cavities is studied in this thesis. Investigations focus on two- and three-dimensional natural convection effects inside air cavities, the dependence of the emissivity on the thermal transmittance, and the emissivity of anodized and untreated aluminium profiles. The investigations are mostly conducted on window frames which are the same size as real frames found in residential buildings. Numerical and experimental investigations were performed to study the effectiveness of one commercial Computational Fluid Dynamics (CFD) program for simulating combined natural convection and heat transfer in simple three-dimensional window frames with internal air cavities. The accuracy of the conjugate CFD simulations was evaluated by comparing results for surface temperature on the warm side of the specimens to results from experiments that use infrared (IR) thermography to map surface temperatures during steady-state thermal tests. In general, there was good agreement between the simulations and experiments. Two-dimensional computational fluid dynamic and conduction simulations are performed to study the difference between treating air cavities as a fluid and as a solid when calculating the thermal transmittance of window frames. The simulations show that traditional software codes, simulating only conduction and using equivalent conductivities for the air cavities, give Uvalues that compare well with results from fluid flow simulations. The difference between the two models are mostly limited to the temperature distribution inside air cavities. It is also found that cavities with an interconnection less than about 7 mm can be treated as separate cavities. Three-dimensional natural convection effects in simple and custom-made PVC and thermally broken aluminum window frames with one open internal cavity were studied, with the use of CFD simulations and thermography experiments. Focus was put on corner effects and heat transfer
International Nuclear Information System (INIS)
Venkataraman, N.S.; Cardoso, H.P.; Oliveira Filho, O.B. de
1981-01-01
The conductive heat transfer in a rectangular plate with nonuniform internal heat generation, with one end convectively cooled and a part of the opposite end subjected to external heat flux is considered. The remaining part of this end as well as the other two sides are thermally insulated. The governing differential equation is solved by a finite difference scheme. The variation of the thermal resistance with Biot modulus, the plate geometry, the internal heat generation parameter and the type of profile of internal heat generation is discussed. (author) [pt
Micro-channel convective boiling heat transfer with flow instabilities
International Nuclear Information System (INIS)
Consolini, L.; Thome, J.R.
2009-01-01
Flow boiling heat transfer in micro-channels has attracted much interest in the past decade, and is currently a strong candidate for high performance compact heat sinks, such as those required in electronics systems, automobile air conditioning units, micro-reactors, fuel cells, etc. Currently the literature presents numerous experimental studies on two-phase heat transfer in micro-channels, providing an extensive database that covers many different fluids and operating conditions. Among the noteworthy elements that have been reported in previous studies, is the sensitivity of micro-channel evaporators to oscillatory two-phase instabilities. These periodic fluctuations in flow and pressure drop either result from the presence of upstream compressibility, or are simply due to the interaction among parallel channels in multi-port systems. An oscillating flow presents singular characteristics that are expected to produce an effect on the local heat transfer mechanisms, and thus on the estimation of the two-phase heat transfer coefficients. The present investigation illustrates results for flow boiling of refrigerants R-134a, R-236fa, and R-245fa in a 510 μm circular micro-channel, exposed to various degrees of oscillatory compressible volume instabilities. The data describe the main features of the fluctuations in the temperatures of the heated wall and fluid, and draw attention to the differences in the measured unstable time-averaged heat transfer coefficients with respect to those for stable flow boiling. (author)
Micro-channel convective boiling heat transfer with flow instabilities
Energy Technology Data Exchange (ETDEWEB)
Consolini, L.; Thome, J.R. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab. de Transfert de Chaleur et de Masse], e-mail: lorenzo.consolini@epfl.ch, e-mail: john.thome@epfl.ch
2009-07-01
Flow boiling heat transfer in micro-channels has attracted much interest in the past decade, and is currently a strong candidate for high performance compact heat sinks, such as those required in electronics systems, automobile air conditioning units, micro-reactors, fuel cells, etc. Currently the literature presents numerous experimental studies on two-phase heat transfer in micro-channels, providing an extensive database that covers many different fluids and operating conditions. Among the noteworthy elements that have been reported in previous studies, is the sensitivity of micro-channel evaporators to oscillatory two-phase instabilities. These periodic fluctuations in flow and pressure drop either result from the presence of upstream compressibility, or are simply due to the interaction among parallel channels in multi-port systems. An oscillating flow presents singular characteristics that are expected to produce an effect on the local heat transfer mechanisms, and thus on the estimation of the two-phase heat transfer coefficients. The present investigation illustrates results for flow boiling of refrigerants R-134a, R-236fa, and R-245fa in a 510 {mu}m circular micro-channel, exposed to various degrees of oscillatory compressible volume instabilities. The data describe the main features of the fluctuations in the temperatures of the heated wall and fluid, and draw attention to the differences in the measured unstable time-averaged heat transfer coefficients with respect to those for stable flow boiling. (author)
New terrestrial heat flow measurements on the Nazca Plate
Energy Technology Data Exchange (ETDEWEB)
Anderson, R N [Columbia Univ., Palisades, NY; Langseth, M G; Vacquier, V; Francheteau, J
1976-03-01
Sixty-seven new heat flow measurements on the Nazca Plate are reported, and the thermal regimes of three specific areas on the plate are examined. The Nazca Ridge is an aseismic ridge which may have been generated as an ''island trail'' from the Easter Island ''hot spot'' and/or may be a fossil transform fault. The Nazca Ridge has lower heat flow than the surrounding sea floor implying that the ridge might have low ''effective'' thermal conductivity causing heat to preferentially flow or refract to surrounding ocean crust which has higher conductivity, or, the low heat flow values may be caused by hydrothermal circulation on the ridge. The Carnegie Plateau is an elevated region south of the Carnegie Ridge on the northeastern Nazca Plate with high heat flow and shallow topography consistent with an age of less than 20 m.y. B.P. The central Nazca Plate is an area of highly variable heat flow which is possibly related to thin sediment and to rough regional topography.
Directory of Open Access Journals (Sweden)
B.S. Bhadauria
2014-12-01
Full Text Available In this paper, a theoretical investigation has been carried out to study the combined effect of rotation speed modulation and internal heating on thermal instability in a temperature dependent viscous horizontal fluid layer. Rayleigh–Bénard momentum equation with Coriolis term has been considered to describe the convective flow. The system is rotating about it is own axis with non-uniform rotational speed. In particular, a time-periodic and sinusoidally varying rotational speed has been considered. A weak nonlinear stability analysis is performed to find the effect of modulation on heat transport. Nusselt number is obtained in terms of amplitude of convection and internal Rayleigh number, and depicted graphically for showing the effects of various parameters of the system. The effect of modulated rotation speed is found to have a stabilizing effect for different values of modulation frequency. Further, internal heating and thermo-rheological parameters are found to destabilize the system.
Thermosolutal MHD flow and radiative heat transfer with viscous ...
African Journals Online (AJOL)
This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...
Miniaturized heat flux sensor for high enthalpy plasma flow characterization
International Nuclear Information System (INIS)
Gardarein, Jean-Laurent; Battaglia, Jean-Luc; Lohlec, Stefan; Jullien, Pierre; Van Ootegemd, Bruno; Couzie, Jacques; Lasserre, Jean-Pierre
2013-01-01
An improved miniaturized heat flux sensor is presented aiming at measuring extreme heat fluxes of plasma wind tunnel flows. The sensor concept is based on an in-depth thermocouple measurement with a miniaturized design and an advanced calibration approach. Moreover, a better spatial estimation of the heat flux profile along the flow cross section is realized with this improved small sensor design. Based on the linearity assumption, the heat flux is determined using the impulse response of the sensor relating the heat flux to the temperature of the embedded thermocouple. The non-integer system identification (NISI) procedure is applied that allows a calculation of the impulse response from transient calibration measurements with a known heat flux of a laser source. The results show that the new sensor leads to radially highly resolved heat flux measurement for a flow with only a few centimetres in diameter, the so far not understood non-symmetric heat flux profiles do not occur with the new sensor design. It is shown that this former effect is not a physical effect of the flow, but a drawback of the classical sensor design. (authors)
Creeping Viscous Flow around a Heat-Generating Solid Sphere
DEFF Research Database (Denmark)
Krenk, Steen
1981-01-01
The velocity field for creeping viscous flow around a solid sphere due to a spherically symmetric thermal field is determined and a simple thermal generalization of Stokes' formula is obtained. The velocity field due to an instantaneous heat source at the center of the sphere is obtained in closed...... form and an application to the storage of heat-generating nuclear waste is discussed....
Local heat transfer coefficient for turbulent flow in rod bundles
International Nuclear Information System (INIS)
Fernandez y Fernandez, E.; Carajilescov, P.
1983-03-01
The correlation of the local heat transfer coefficients in heated triangular array of rod bundles, in terms of the flow hydrodynamic parameters is presented. The analysis is made first for fluid with Prandtl numbers varying from moderated to high (Pr>0.2), and then extended to fluids with low Prandtl numbers (0.004 [pt
Measuring Gravity in International Trade Flows
Directory of Open Access Journals (Sweden)
E. Young Song
2004-12-01
Full Text Available The purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of income levels of countries, and in trade of most manThe purpose of this paper is two-fold. One is to clarify the concept of gravity in international trade flows. The other is to measure the strength of gravity in international trade flows in a way that is consistent with a well-defined concept of gravity. This paper shows that the widely accepted belief that specialization is the source of gravity is not well grounded on theory. We propose to define gravity in international trade as the force that makes the market shares of an exporting country constant in all importing countries, regardless of their sizes. In a stochastic context, we should interpret it as implying that the strength of gravity increases i as the correlation between market shares and market sizes gets weaker and ii as the variance of market shares gets smaller. We estimate an empirical gravity equation thoroughly based on this definition of gravity. We find that a strong degree of gravity exists in most bilateral trade, regardless of
Heat transfer and fluid flow in nuclear systems
International Nuclear Information System (INIS)
Fenech, H.
1981-01-01
The present publication is an attempt to provide a bridge between fundamental principles and current design practice. It is intended to serve the need of: engineers, scientists and graduate students active in thermal and hydraulics problems and to those interested to keep abreast of the field. The text is addressed to readers with previous knowledge in heat transfer and fluid flow equvalent to a one year university graduate course in that field. Because of the high degree of specialization covered in the six chapters of the book, individual authors of international reputation and active in their respective area of specialization were selected to contribute their knowledge. Each of the six chapters or sub-chapters are self-contained. They are followed by problem sets to enable the reader to check his level of comprehension of the material presented. The nuclear systems covered in separate chapters include: the pressurized and boiling water reactors (PWR, BWR), the helium cooled high temperature reactors (HTGR and HTR), the breeders helium cooled (GCFR) and sodium cooled (LMFBR). In addition the heat-exchangers and steam generators commonly associated with the above systems are covered in Chapter 6
International Nuclear Information System (INIS)
Gang Wu; Bi Qincheng; Yang Zhendong; Wang Han; Zhu Xiaojing; Hao Hou; Leung, L.K.H.
2011-01-01
Highlights: → Two annular test sections were constructed with annular gaps of 4 and 6 mm. → Two heat transfer regions have been observed: normal and deteriorated heat transfer. → The spacer enhances the heat transfer at downstream locations. → The Jackson correlation agrees quite closely with the experimental data. - Abstract: An experiment has recently been completed at Xi'an Jiaotong University (XJTU) to obtain wall-temperature measurements at supercritical pressures with upward flow of water inside vertical annuli. Two annular test sections were constructed with annular gaps of 4 and 6 mm, respectively, and an internal heater of 8 mm outer diameter. Experimental-parameter ranges covered pressures of 23-28 MPa, mass fluxes of 350-1000 kg/m 2 /s, heat fluxes of 200-1000 kW/m 2 , and bulk inlet temperatures up to 400 deg. C. Depending on the flow conditions and heat fluxes, two distinctive heat transfer regimes, referring to as the normal heat transfer and deteriorated heat transfer, have been observed. At similar flow conditions, the heat transfer coefficients for the 6 mm gap annular channel are larger than those for the 4 mm gap annular channel. A strong effect of spiral spacer on heat transfer has been observed with a drastic reduction in wall temperature at locations downstream of the device in the annuli. Two tube-data-based correlations have been assessed against the experimental heat transfer results. The Jackson correlation agrees with the experimental trends and overpredicts slightly the heat transfer coefficients. The Dittus-Boelter correlation is applicable only for the normal heat transfer region but not for the deteriorated heat transfer region.
Saturated flow boiling heat transfer in water-heated vertical annulus
International Nuclear Information System (INIS)
Sun Licheng; Yan Changqi; Sun Zhonning
2005-01-01
This paper describes the saturated flow boiling heat transfer characteristics of water at 1 atm and low velocities in water-heated vertical annuli with equivalent diameters of 10 mm and 6 mm. Test section is consisted of two concentric circular tubes outer of which is made of quartz, so the whole test courses can be visualized. There are three main flow patterns of bubble flow, churn flow and churn-annular flow in the annuli, most important of which is churn flow. Flooding is the mechanism of churn flow and churn can enhance the heat transport between steam and water; Among the three factors of mass flux, inlet subcooling and annulus width, the last one has great effect on heat transport, moderately decreasing the annulus width can enhance the heat transfer; Combined annular flow model with theory of flooding and turbulent Prandtl Number, the numerical value of heat flux is given, the shape of test boiling curve and that of calculated by model is very alike, but there is large discrepancy between test data and calculated results, the most possible reason is that some parameters given by fluid flooding model are based on experimental data of common circular tubes, but not of annuli. Doing more research on flooding in annulus, particularly narrow annulus, is necessary for calculating the saturated boiling in annulus. (authors)
Heat transfer in vapour-liquid flow of carbon dioxide
International Nuclear Information System (INIS)
Yagov, V.V.
2009-01-01
During the last decade a number of studies of boiling heat transfer in carbon dioxide notably increase. As a field of CO 2 practical using corresponds to high reduced pressures, and a majority of available experimental data on CO 2 flow boiling even in submillimetric channels relate to turbulent liquid flow regimes, a possibility arises to develop sufficiently general method for HTC predicting. Under the above conditions nucleate boiling occurs up to rather high flow quality, even in annular flow regime due to extremely small size of an equilibrium vapour bubble. This conclusion is in agreement with the available experimental data. The predicting equation for nucleate boiling heat transfer developed by the present author in 1988 is valid for any nonmetallic liquid. A contribution of forced convection in heat transfer is calculated according to the Petukhov et al. equation with correction factor, which accounted for an effect of velocity increase due to evaporation. This effect can be essential at relatively small heat fluxes and rather high mass flow rates. The Reynolds analogy and homogeneous model are used in order to account for the convective heat transfer augmentation in two-phase flow. Due to low ratio of liquid and vapour densities at high reduced pressures the homogeneous approximation of two-phase flow seems to be warranted. A total heat transfer coefficient is calculated as an interpolated value of boiling and convective HTCs. The experimental data on CO 2 flow boiling related to regimes before heated wall dryout incipience are in rather good agreement with the calculations. (author)
Flow visualization in heat-generating porous media
International Nuclear Information System (INIS)
Lee, D.O.; Nilson, R.H.
1977-11-01
The work reported is in support of the Sandia Post-Accident Heat Removal Program, in which simulated LMFBR beds will be subjected to in-pile heating in the ACPR (Annular Core Pulsed Reactor). Flow visualization experiments were performed to gain some insight into the flow patterns and temperature distributions in a fluid-saturated heat-generating porous medium. Although much of the information presented is of a qualitative nature, it is useful in the recognition of the controlling transport process and in the formulation of analytic and numerical models
SCEPTIC, Pressure Drop, Flow Rate, Heat Transfer, Temperature in Reactor Heat Exchanger
International Nuclear Information System (INIS)
Kattchee, N.; Reynolds, W.C.
1975-01-01
1 - Nature of physical problem solved: SCEPTIC is a program for calculating pressure drop, flow rates, heat transfer rates, and temperature in heat exchangers such as fuel elements of typical gas or liquid cooled nuclear reactors. The effects of turbulent and heat interchange between flow passages are considered. 2 - Method of solution: The computation procedure amounts to a nodal of lumped parameter type of calculation. The axial mesh size is automatically selected to assure that a prescribed accuracy of results is obtained. 3 - Restrictions on the complexity of the problem: Maximum number of subchannels is 25, maximum number of heated surfaces is 46
Heat flow characteristics of Xiangshan uranium mine
International Nuclear Information System (INIS)
Huang Guoming
1996-01-01
By studying Xiangshan uranium mine on the heat generation of radioactive element, the author expounds its geothermal character and evaluates the influence on geothermal flux, geothermal gradient and geothermal field. The results show that the geothermal structure is changed due to the enrichment of radioactive elements, but the geothermal field is slightly influenced
Heat Transfer Enhancement in Separated and Vortex Flows
Energy Technology Data Exchange (ETDEWEB)
Richard J. Goldstein
2004-05-27
This document summarizes the research performance done at the Heat Transfer Laboratory of the University of Minnesota on heat transfer and energy separation in separated and vortex flow supported by DOE in the period September 1, 1998--August 31, 2003. Unsteady and complicated flow structures in separated or vortex flows are the main reason for a poor understanding of heat transfer under such conditions. The research from the University of Minnesota focused on the following important aspects of understanding such flows: (1) Heat/mass transfer from a circular cylinder; (2) study of energy separation and heat transfer in free jet flows and shear layers; and (3) study of energy separation on the surface and in the wake of a cylinder in crossflow. The current study used three different experimental setups to accomplish these goals. A wind tunnel and a liquid tunnel using water and mixtures of ethylene glycol and water, is used for the study of prandtl number effect with uniform heat flux from the circular cylinder. A high velocity air jet is used to study energy separation in free jets. A high speed wind tunnel, same as used for the first part, is utilized for energy separation effects on the surface and in the wake of the circular cylinder. The final outcome of this study is a substantial advancement in this research area.
Analysis of the internal heat losses in a thermoelectric generator
DEFF Research Database (Denmark)
Bjørk, Rasmus; Christensen, Dennis Valbjørn; Eriksen, Dan
2014-01-01
and radiative heat losses, including surface to surface radiation. For radiative heat losses it is shown that for the temperatures considered here, surface to ambient radiation is a good approximation of the heat loss. For conductive heat transfer the module efficiency is shown to be comparable to the case...... of radiative losses. Finally, heat losses due to internal natural convection in the module is shown to be negligible for the millimetre sized modules considered here. The combined case of radiative and conductive heat transfer resulted in the lowest efficiency. The optimized load resistance is found...... to decrease for increased heat loss. The leg dimensions are varied for all heat losses cases and it is shown that the ideal way to construct a TEG module with minimal heat losses and maximum efficiency is to either use a good insulating material between the legs or evacuate the module completely, and use...
Studies of heat transport to forced-flow He II
International Nuclear Information System (INIS)
Dresner, L.; Kashani, A.; Van Sciver, S.W.
1985-01-01
Analytical and experimental studies of heat transport to forced-flow He II are reported. The work is pertinent to the transfer of He II in space. An analytical model has been developed that establishes a condition for two-phase flow to occur in the transfer line. This condition sets an allowable limit to the heat leak into the transfer line. Experimental measurements of pressure drop and flow meter performances indicate that turbulent He II can be analyzed in terms of classical pressure drop correlations
Numerical prediction of flow, heat transfer, turbulence and combustion
Spalding, D Brian; Pollard, Andrew; Singhal, Ashok K
1983-01-01
Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion: Selected Works of Professor D. Brian Spalding focuses on the many contributions of Professor Spalding on thermodynamics. This compilation of his works is done to honor the professor on the occasion of his 60th birthday. Relatively, the works contained in this book are selected to highlight the genius of Professor Spalding in this field of interest. The book presents various research on combustion, heat transfer, turbulence, and flows. His thinking on separated flows paved the way for the multi-dimensional modeling of turbu
Investigation of the tube side flow distribution in heat exchangers
International Nuclear Information System (INIS)
AbuRomia, M.M.; Pyare, R.
1977-01-01
The tube side flow distribution in heat exchangers is being investigated through the solution of the governing equations of fluid mechanics with distributed resistances that simulate the presence of the tubes. The modeling scheme used in the analysis and the numerical methods of solving the governing equations are described. The analysis is applied to the CRBRP-Intermediate Heat Exchanger (IHX), where its tube side plenum is simulated by several models that approximate its spherical boundary. The flow field within the plenum and the distribution of the total flow rate among the tubes are determined by the analysis
Lunar heat flow: Regional prospective of the Apollo landing sites
Siegler, M. A.; Smrekar, S. E.
2014-01-01
reexamine the Apollo Heat Flow Experiment in light of new orbital data. Using three-dimensional thermal conduction models, we examine effects of crustal thickness, density, and radiogenic abundance on measured heat flow values at the Apollo 15 and 17 sites. These models show the importance of regional context on heat flux measurements. We find that measured heat flux can be greatly altered by deep subsurface radiogenic content and crustal density. However, total crustal thickness and the presence of a near-surface radiogenic-rich ejecta provide less leverage, representing only minor (<1.5 mW m-2) perturbations on surface heat flux. Using models of the crust implied by Gravity Recovery and Interior Laboratory results, we found that a roughly 9-13 mW m-2 mantle heat flux best approximate the observed heat flux. This equates to a total mantle heat production of 2.8-4.1 × 1011 W. These heat flow values could imply that the lunar interior is slightly less radiogenic than the Earth's mantle, perhaps implying that a considerable fraction of terrestrial mantle material was incorporated at the time of formation. These results may also imply that heat flux at the crust-mantle boundary beneath the Procellarum potassium, rare earth element, and phosphorus (KREEP) Terrane (PKT) is anomalously elevated compared to the rest of the Moon. These results also suggest that a limited KREEP-rich layer exists beneath the PKT crust. If a subcrustal KREEP-rich layer extends below the Apollo 17 landing site, required mantle heat flux can drop to roughly 7 mW m-2, underlining the need for future heat flux measurements outside of the radiogenic-rich PKT region.
Heat transfer in tube bundles of heat exchangers with flow baffles induced forced mixing
International Nuclear Information System (INIS)
AbuRomia, M.M.; Chu, A.W.; Cho, S.M.
1976-01-01
Thermal analysis of shell-and-tube heat exchangers is being investigated through geometric modeling of the unit configuration in addition to considering the heat transfer processes taking place within the tube bundle. The governing equations that characterize the heat transfer from the shell side fluid to the tube side fluid across the heat transfer tubewalls are indicated. The equations account for the heat transfer due to molecular conduction, turbulent thermal diffusion, and forced fluid mixing among various shell side fluid channels. The analysis, though general in principle, is being applied to the Clinch River Breeder Reactor Plant-Intermediate Heat Exchanger, which utilizes flow baffles appropriately designed for induced forced fluid mixing in the tube bundle. The results of the analysis are presented in terms of the fluid and tube wall temperature distributions of a non-baffled and baffled tube bundle geometry. The former case yields axial flow in the main bundle region while the latter is associated with axial/cross flow in the bundle. The radial components of the axial/cross flow yield the necessary fluid mixing that results in reducing the thermal unbalance among the heat transfer to the allowable limits. The effect of flow maldistribution, present on the tube or shell sides of the heat exchangers, in altering the temperature field of tube bundles is also noted
Analytical modeling for heat transfer in sheared flows of nanofluids.
Ferrari, Claudio; Kaoui, Badr; L'vov, Victor S; Procaccia, Itamar; Rudenko, Oleksii; ten Thije Boonkkamp, J H M; Toschi, Federico
2012-07-01
We developed a model for the enhancement of the heat flux by spherical and elongated nanoparticles in sheared laminar flows of nanofluids. Besides the heat flux carried by the nanoparticles, the model accounts for the contribution of their rotation to the heat flux inside and outside the particles. The rotation of the nanoparticles has a twofold effect: it induces a fluid advection around the particle and it strongly influences the statistical distribution of particle orientations. These dynamical effects, which were not included in existing thermal models, are responsible for changing the thermal properties of flowing fluids as compared to quiescent fluids. The proposed model is strongly supported by extensive numerical simulations, demonstrating a potential increase of the heat flux far beyond the Maxwell-Garnett limit for the spherical nanoparticles. The road ahead, which should lead toward robust predictive models of heat flux enhancement, is discussed.
Transient heat transfer for forced convection flow of helium gas
International Nuclear Information System (INIS)
Liu, Qiusheng; Fukuda, Katsuya; Sasaki, Kenji; Yamamoto, Manabu
1999-01-01
Transient heat transfer coefficients for forced convection flow of helium gas over a horizontal cylinder were measured using a forced convection test loop. The platinum heater with a diameter of 1.0 mm was heated by electric current with an exponential increase of Q 0 exp(t/τ). It was clarified that the heat transfer coefficient approaches the steady-state one for the period τ over 1 s, and it becomes higher for the period of τ shorter than 1 s. The transient heat transfer shows less dependent on the gas flowing velocity when the period becomes very shorter. Semi-empirical correlations for steady-state and transient heat transfer were developed based on the experimental data. (author)
Instability of flow of liquid film over a heated surface
International Nuclear Information System (INIS)
Sha, W.T.
1994-01-01
Fundamental concepts and basic equations of a flowing thin liquid film cooling a heated surfaced by its vaporization and the effect of dry patches were treated. Stable film flow prior to the appearance of dry patches on the heated surface is maintained by a balance of various forces due to surface tension, shear stress, heat and mass transfer, and gravity. Film splitting at a critical film thickness produces dry patches due to perturbation by waves on a perfect surface, and often by surface imperfection and uneven heating. This work is primarily motivated by the design of next-generation nuclear reactors, which employ many novel passive heat-removal systems via natural circulation. These systems are design to prevent damage to the reactor core and containment without action by the reactor operators during or after a design basis accident such as a loss of coolant accident (LOCA) or a main steam-line break (MSLB) accident
A novel compact heat exchanger using gap flow mechanism.
Liang, J S; Zhang, Y; Wang, D Z; Luo, T P; Ren, T Q
2015-02-01
A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.
National and international graduate migration flows.
Mosca, Irene; Wright, Robert E
2010-01-01
This article examines the nature of national and international graduate migration flows in the UK. Migration equations are estimated with microdata from a matched dataset of Students and Destinations of Leavers from Higher Education, information collected by the Higher Education Statistical Agency. The probability of migrating is related to a set of observable characteristics using multinomial logit regression. The analysis suggests that migration is a selective process with graduates with certain characteristics having considerably higher probabilities of migrating, both to other regions of the UK and abroad.
Flow and heat transfer regimes during quenching of hot surfaces
International Nuclear Information System (INIS)
Barnea, Y.; Elias, E.
1993-05-01
Reflooding experiments have been performed to study flow and heat transfer regimes in a heated annular vertical channel under supercooled inlet conditions. A gamma densitometer was employed to determine the void fraction as a function of the distance from the quench front. Surface heat fluxes were determined by fast measurements of the temperature spatial distribution. Two quench front is shown to lie in the transition boiling region which spreads into the dry and wet segments of the heated surface. (authors) 5 refs, 3 figs
Convective heat transfer in supercritical flows of CO_2 in tubes with and without flow obstacles
International Nuclear Information System (INIS)
Eter, Ahmad; Groeneveld, Dé; Tavoularis, Stavros
2017-01-01
Highlights: • Measurements of supercritical heat transfer in tubes equipped with obstacles were obtained and compared with results in base tubes. • In general, flow obstacles improve supercritical heat transfer, but under certain conditions have a negative effect on it. • New correlations describing obstacle-enhanced supercritical heat transfer in the liquid-like and gas-like regimes are fitted to the data. - Abstract: Heat transfer measurements to CO_2-cooled tubes with and without flow obstacles at supercritical pressures were obtained at the University of Ottawa’s supercritical pressure test facility. The effects of obstacle geometry (obstacle pitch, obstacle shape, flow blockage) on the wall temperature and heat transfer coefficient were investigated. Tests were performed for vertical upward flow in a directly heated 8 mm ID tube for a pressure range from 7.69 to 8.36 MPa, a mass flux range from 200 to 1184 kg/m"2 s, and a heat flux range from 1 to 175 kW/m"2. The results are presented graphically in plots of wall temperature and heat transfer coefficient vs. bulk specific enthalpy of the fluid. The effects of flow parameters and flow obstacle geometry on supercritical heat transfer for both normal and deteriorated heat transfer are discussed. A comparison of the measurements with leading prediction methods for supercritical heat transfer in bare tubes and for spacer effects is also presented. The optimum increase in heat transfer coefficient was found to be for blunt obstacles, having a large flow blockage, and a short obstacle pitch.
CFD investigation of flow through internally riffled boiler tubes
DEFF Research Database (Denmark)
Rasmussen, Christian; Houbak, Niels; Sørensen, Jens Nørkær
1997-01-01
In this paper we show how to model the swirling flow in an internally riffled boiler tube. The flow field is visualized and the results are compared with measurements.......In this paper we show how to model the swirling flow in an internally riffled boiler tube. The flow field is visualized and the results are compared with measurements....
The Determinants of International News Flow: A Network Analysis.
Kim, Kyungmo; Barnett, George A.
1996-01-01
Examines the structure of international news flow and its determinants. Reveals inequality of international news flow between core and periphery, with Western industrialized countries at the center. Finds that the news flow network is structured into eight geographic-linguistic groups. Indicates flow is influenced by a country's economic…
Liquid metal heat transfer in heat exchangers under low flow rate conditions
International Nuclear Information System (INIS)
Mochizuki, Hiroyasu
2015-01-01
The present paper describes the liquid metal heat transfer in heat exchangers under low flow rate conditions. Measured data from some experiments indicate that heat transfer coefficients of liquid metals at very low Péclet number are much lower than what are predicted by the well-known empirical relations. The cause of this phenomenon was not fully understood for many years. In the present study, one countercurrent-type heat exchanger is analyzed using three, separated countercurrent heat exchanger models: one is a heat exchanger model in the tube bank region, while the upper and lower plena are modeled as two heat exchangers with a single heat transfer tube. In all three heat exchangers, the same empirical correlation is used in the heat transfer calculation on the tube and the shell sides. The Nusselt number, as a function of the Péclet number, calculated from measured temperature and flow rate data in a 50 MW experimental facility was correctly reproduced by the calculation result, when the calculated result is processed in the same way as the experiment. Finally, it is clarified that the deviation is a superficial phenomenon which is caused by the heat transfer in the plena of the heat exchanger. (author)
Flow boiling heat transfer at low liquid Reynolds number
International Nuclear Information System (INIS)
Weizhong Zhang; Takashi Hibiki; Kaichiro Mishima
2005-01-01
Full text of publication follows: In view of the significance of a heat transfer correlation of flow boiling at conditions of low liquid Reynolds number or liquid laminar flow, and very few existing correlations in principle suitable for such flow conditions, this study is aiming at developing a heat transfer correlation of flow boiling at low liquid Reynolds number conditions. The obtained results are as follows: 1. A new heat transfer correlation has been developed for saturated flow boiling at low liquid Reynolds number conditions based on superimposition of two boiling mechanisms, namely convective boiling and nucleate boiling. In the new correlation, two terms corresponding to the mechanisms of nucleate boiling and convective boiling are obtained from the pool boiling correlation by Forster and Zuber and the analytical annular flow model by Hewitt and Hall-Taylor, respectively. 2. An extensive database was collected for saturated flow boiling heat transfer at low liquid Reynolds number conditions, including data for different channels geometries (circular and rectangular), flow orientations (vertical and horizontal), and working fluids (water, R11, R12, R113). 3. An extensive comparison of the new correlation with the collected database shows that the new correlation works satisfactorily with the mean deviation of 16.6% for saturated flow boiling at low liquid Reynolds number conditions. 4. The detailed discussion reveals the similarity of the newly developed correlation for flow boiling at low liquid Reynolds number to the Chen correlation for flow boiling at high liquid Reynolds number. The Reynolds number factor F can be analytically deduced in this study. (authors)
Heat transfer in rotating serpentine passages with trips normal to the flow
Wagner, J. H.; Johnson, B. V.; Graziani, R. A.; Yeh, F. C.
1991-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.
Heat flow, heat transfer and lithosphere rheology in geothermal areas: Features and examples
Ranalli, G.; Rybach, L.
2005-10-01
Surface heat flow measurements over active geothermal systems indicate strongly positive thermal anomalies. Whereas in "normal" geothermal settings, the surface heat flow is usually below 100-120 mW m - 2 , in active geothermal areas heat flow values as high as several watts per meter squared can be found. Systematic interpretation of heat flow patterns sheds light on heat transfer mechanisms at depth on different lateral, depth and time scales. Borehole temperature profiles in active geothermal areas show various signs of subsurface fluid movement, depending on position in the active system. The heat transfer regime is dominated by heat advection (mainly free convection). The onset of free convection depends on various factors, such as permeability, temperature gradient and fluid properties. The features of heat transfer are different for single or two-phase flow. Characteristic heat flow and heat transfer features in active geothermal systems are demonstrated by examples from Iceland, Italy, New Zealand and the USA. Two main factors affect the rheology of the lithosphere in active geothermal areas: steep temperature gradients and high pore fluid pressures. Combined with lithology and structure, these factors result in a rheological zonation with important consequences both for geodynamic processes and for the exploitation of geothermal energy. As a consequence of anomalously high temperature, the mechanical lithosphere is thin and its total strength can be reduced by almost one order of magnitude with respect to the average strength of continental lithosphere of comparable age and thickness. The top of the brittle/ductile transition is located within the upper crust at depths less than 10 km, acts as the root zone of listric normal faults in extensional environments and, at least in some cases, is visible on seismic reflection lines. These structural and rheological features are well illustrated in the Larderello geothermal field in Tuscany.
Chaotic advection and heat transfer enhancement in Stokes flows
International Nuclear Information System (INIS)
Lefevre, A.; Mota, J.P.B.; Rodrigo, A.J.S.; Saatdjian, E.
2003-01-01
The heat transfer rate from a solid boundary to a highly viscous fluid can be enhanced significantly by a phenomenon which is called chaotic advection or Lagrangian turbulence. Although the flow is laminar and dominated by viscous forces, some fluid particle trajectories are chaotic due either to a suitable boundary displacement protocol or to a change in geometry. As in turbulent flow, the heat transfer rate enhancement between the boundary and the fluid is intimately linked to the mixing of fluid in the system. Chaotic advection in real Stokes flows, i.e. flows governed by viscous forces and that can be constructed experimentally, is reviewed in this paper. An emphasis is made on recent new results on 3-D time-periodic open flows which are particularly important in industry
Ashwal, L. D.; Morgan, P.; Kelley, S. A.; Percival, J. A.
1987-01-01
Concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100-km transect of the Superior Province of the Canadian Shield have been obtained. The relatively large variation in heat production found among the silicic plutonic rocks is shown to correlate with modal abundances of accessory minerals, and these variations are interpreted as premetamorphic. The present data suggest fundamental differences in crustal radioactivity distributions between granitic and more mafic terrains, and indicate that a previously determined apparently linear heat flow-heat production relationship for the Kapuskasing area does not relate to the distribution of heat production with depth.
Brine flow in heated geologic salt.
Energy Technology Data Exchange (ETDEWEB)
Kuhlman, Kristopher L.; Malama, Bwalya
2013-03-01
This report is a summary of the physical processes, primary governing equations, solution approaches, and historic testing related to brine migration in geologic salt. Although most information presented in this report is not new, we synthesize a large amount of material scattered across dozens of laboratory reports, journal papers, conference proceedings, and textbooks. We present a mathematical description of the governing brine flow mechanisms in geologic salt. We outline the general coupled thermal, multi-phase hydrologic, and mechanical processes. We derive these processes governing equations, which can be used to predict brine flow. These equations are valid under a wide variety of conditions applicable to radioactive waste disposal in rooms and boreholes excavated into geologic salt.
Transient convective heat transfer to laminar flow from a flat plate with constant heat capacity
International Nuclear Information System (INIS)
Hanawa, Juichi
1980-01-01
Most basic transient heat transfer problem is the transient response characteristics of forced convection heat transfer in the flow along a flat plate or in a tube. In case of the laminar flow along a flat plate, the profile method using steady temperature distribution has been mostly adopted, but its propriety has not been clarified yet. About the unsteady heat transfer in the laminar flow along a flat plate, the analysis or experiment evaluating the heat capacity of the flat plate exactly was never carried out. The purpose of this study is to determine by numerical calculation the unsteady characteristics of the boundary layer in laminar flow and to confirm them by experiment concerning the unsteady heat transfer when a flat plate with a certain heat capacity is placed in parallel in uniform flow and given a certain quantity of heat generation suddenly. The basic equation and the solution are given, and the method of numerical calculation and the result are explained. The experimental setup and method, and the experimental results are shown. Both results were in good agreement, and the response of wall temperature, the response of Nusselt number and the change of temperature distribution in course of time were able to be determined by applying Laplace transformation and numerical Laplace inverse transformation to the equation. (Kako, I.)
Multilevel Flow Modeling of Domestic Heating Systems
DEFF Research Database (Denmark)
Hu, Junjie; Lind, Morten; You, Shi
2012-01-01
the operation on fault analysis and control. A significant improvement of the MFM methodology has been recently proposed, where the “role” concept was introduced to enable the representation of structural entities and the conveyance of important information for building up knowledge bases, with the purpose...... i.e. supplying and transferring thermal energy, it is off interest to use MFM to investigate similarities and differences between different implementations. In this paper, three typical domestic European heating systems, which differ from each other in the number of temperature sensors and auxiliary...
DEFF Research Database (Denmark)
Alberdi Pagola, Maria; Poulsen, Søren Erbs; Loveridge, Fleur
2018-01-01
This paper investigates the applicability of currently available analytical, empirical and numerical heat flow models for interpreting thermal response tests (TRT) of quadratic cross section precast pile heat exchangers. A 3D finite element model (FEM) is utilised for interpreting five TRTs by in...
FOREWORD: International Symposium of Cavitation and Multiphase Flow (ISCM 2014)
Wu, Yulin
2015-01-01
multiphase flow detection Fluid-structure interaction induced by cavitation and multiphase flow Multi-scale modelling of cavitating flows and Multiphase Flow Cavitation nuclei: theory and experiments Supercavitation and its applications Synergetic effects of cavitation and silt-laden erosion Shock waves and microjets generated by cavitation Nonlinear oscillations of gas and vapour bubbles Fundamentals of physics of acoustic cavitation Sonochemistry and sonoluminescence Biomedical applications of cavitation effects Ultrasonic cavitation for molten metal treatment Cavitation for enhanced heat transfer The ISCM 2014 brought together 95 scientists, researchers and graduate students from 11 countries, affiliated with universities, technology centers and industrial firms to debate topics related to advanced technologies for cavitation and Multiphase Flow, which would enhance the sustainable development of cavitation and Multiphase Flow in interdisciplinary sciences and technology. The technical committee selected 54 technical papers on the following topics: (i) Hydrodynamic Cavitation, (ii) Super Cavitation, (iii) Pump Cavitation, (iv) Acoustic Cavitation, (v) Interdisciplinary Research of Cavitation and Multi-Phase Flows, and 13 invited plenary and invited forum lectures, which were presented at the symposium, to be included in the proceedings. All the papers of ISCM 2014, which are published in this Volume of IOP Conference Series: Materials Science and Engineering, had been peer reviewed through processes administered by the editors of the ISCM 2014, those are Yulin WU, Shouqi YUAN, Zhengwei WANG, Shuhong LIU, Xingqi LUO, Fujun WANG and Guoyu WANG. The papers published in this Volume include 54 technical papers and 3 full length texts of the invited lectures. We sincerely hope that the International Symposium on Cavitation and Multiphase Flow is a significant step forward in the world wide efforts to address the present challenges in the modern science and technology. Professor
International Symposium of Cavitation and Multiphase Flow (ISCM 2014)
International Nuclear Information System (INIS)
Wu, Yulin
2015-01-01
multiphase flow detection Fluid-structure interaction induced by cavitation and multiphase flow Multi-scale modelling of cavitating flows and Multiphase Flow Cavitation nuclei: theory and experiments Supercavitation and its applications Synergetic effects of cavitation and silt-laden erosion Shock waves and microjets generated by cavitation Nonlinear oscillations of gas and vapour bubbles Fundamentals of physics of acoustic cavitation Sonochemistry and sonoluminescence Biomedical applications of cavitation effects Ultrasonic cavitation for molten metal treatment Cavitation for enhanced heat transfer The ISCM 2014 brought together 95 scientists, researchers and graduate students from 11 countries, affiliated with universities, technology centers and industrial firms to debate topics related to advanced technologies for cavitation and Multiphase Flow, which would enhance the sustainable development of cavitation and Multiphase Flow in interdisciplinary sciences and technology. The technical committee selected 54 technical papers on the following topics: (i) Hydrodynamic Cavitation, (ii) Super Cavitation, (iii) Pump Cavitation, (iv) Acoustic Cavitation, (v) Interdisciplinary Research of Cavitation and Multi-Phase Flows, and 13 invited plenary and invited forum lectures, which were presented at the symposium, to be included in the proceedings. All the papers of ISCM 2014, which are published in this Volume of IOP Conference Series: Materials Science and Engineering, had been peer reviewed through processes administered by the editors of the ISCM 2014, those are Yulin WU, Shouqi YUAN, Zhengwei WANG, Shuhong LIU, Xingqi LUO, Fujun WANG and Guoyu WANG. The papers published in this Volume include 54 technical papers and 3 full length texts of the invited lectures. We sincerely hope that the International Symposium on Cavitation and Multiphase Flow is a significant step forward in the world wide efforts to address the present challenges in the modern science and technology. Professor
Transient heat transfer to laminar flow from a flat plate with heat capacity
International Nuclear Information System (INIS)
Hanawa, Juichi
1975-01-01
As the most basic problem in transient heat transfer, a plate with heat capacity was studied, which is placed in uniform laminar flow in parallel with it, is initially at the same temperature as that of the fluid, and then abruptly is given a specific heating value. The equation of transient heat transfer in this case was solved by numerical calculation. The following matters were revealed. (1) The equation was able to be solved by the application of Laplace transformation and numerical inverse transformation. (2) Wall temperature when the heat capacity of a plate was zero initially agreed well with heat conduction solution. With increase of the heat capacity, the delay in wall temperature rise was increased. (3) Heat transfer rate in case of the heat capacity of zero initially agreed well with the heat-conduction solution. With increase of the heat capacity, the Nusselt number increased. (4) Temperature distribution in case of the heat capacity of zero initially agreed well with the heat-conduction solution. (Mori, K.)
Computation of turbulent flow and heat transfer in subassemblies
International Nuclear Information System (INIS)
Slagter, W.
1979-01-01
This research is carried out in order to provide information on the thermohydraulic behaviour of fast reactor subassemblies. The research work involves the development of versatile computation methods and the evaluation of combined theoretical and experimental work on fluid flow and heat transfer in fuel rod bundles. The computation method described here rests on the application of the distributed parameter approach. The conditions considered cover steady, turbulent flow and heat transfer of incompressible fluids in bundles of bare rods. Throughout 1978 main efforts were given to the development of the VITESSE program and to the validation of the hydrodynamic part of the code. In its present version the VITESSE program is applicable to predict the fully developed turbulent flow and heat transfer in the subchannels of a bundle with bare rods. In this paper the main features of the code are described as well as the present status of development
Local Heat Transfer and CHF for Subcooled Flow Boiling - Annual Report 1993
International Nuclear Information System (INIS)
Boyd, Ronald D.
2000-01-01
Subcooled flow boiling in heated coolant channels is an important heat transfer enhancement technique in the development of fusion reactor components, where high heat fluxes must be accommodated. As energy fluxes increase in magnitude, additional emphasis must be devoted to enhancing techniques such as sub cooling and enhanced surfaces. In addition to subcooling, other high heat flux alternatives such as high velocity helium and liquid metal cooling have been considered as serious contenders. Each technique has its advantages and disadvantages [1], which must be weighed as to reliability and reduced cost of fusion reactor components. Previous studies [2] have set the stage for the present work, which will concentrate on fundamental thermal hydraulic issues associated with the h-international Thermonuclear Experimental Reactor (ITER) and the Engineering Design Activity (EDA). This proposed work is intended to increase our understanding of high heat flux removal alternatives as well as our present capabilities by: (1) including single-side heating effects in models for local predictions of heat transfer and critical heat flux; (2) inspection of the US, Japanese, and other possible data sources for single-side heating, with the aim of exploring possible correlations for both CHF and local heat transfer; and (3) assessing the viability of various high heat flux removal techniques. The latter task includes: (a) sub-cooled water flow boiling with enhancements such as twisted tapes, and hypervapotrons, (b) high velocity helium cooling, and (c) other potential techniques such as liquid metal cooling. This assessment will increase our understanding of: (1) hypervapotron heat transfer via fins, flow recirculation, and flow oscillation, and (2) swirl flow. This progress report contains selective examples of ongoing work. Section II contains an extended abstract, which is part of and evolving technical paper on single-side f heating. Section III describes additional details
International symposium on transient convective heat transfer: book of abstracts
International Nuclear Information System (INIS)
1996-01-01
The international symposium on convective heat transfer was held on 19-23 August 1996, in Cesme, Izmir, Turkey. The spesialists discussed forced convection, heat exchangers, free convection and multiphase media and phase change at the meeting. Almost 53 papers were presented in the meeting
International Nuclear Information System (INIS)
Kinoshita, Hidetaka; Yoshida, Takuya; Nariai, Hideki; Inasaka, Fujio
1998-01-01
Effect of heated length on the Critical Heat Flux (CHF) of subcooled flow boiling with water was experimentally investigated by using direct current heated tube made of stainless steel a part of whose wall thickness was axially cut for realizing nonuniform heat flux condition. The higher enhancement of the CHF was derived for shorter tube length. The effective heated length was determined for the tube under axially nonuniform heat flux condition. When the lower heat flux part below the Net Vapor Generation (NVG) heat flux exists at the middle of tube length, then the effective heated length becomes the tube length downstream the lower heat flux parts. However, when the lower heat flux part is above the NVG, then the effective heated length is full tube length. (author)
Modelling of convective heat and mass transfer in rotating flows
Shevchuk, Igor V
2016-01-01
This monograph presents results of the analytical and numerical modeling of convective heat and mass transfer in different rotating flows caused by (i) system rotation, (ii) swirl flows due to swirl generators, and (iii) surface curvature in turns and bends. Volume forces (i.e. centrifugal and Coriolis forces), which influence the flow pattern, emerge in all of these rotating flows. The main part of this work deals with rotating flows caused by system rotation, which includes several rotating-disk configurations and straight pipes rotating about a parallel axis. Swirl flows are studied in some of the configurations mentioned above. Curvilinear flows are investigated in different geometries of two-pass ribbed and smooth channels with 180° bends. The author demonstrates that the complex phenomena of fluid flow and convective heat transfer in rotating flows can be successfully simulated using not only the universal CFD methodology, but in certain cases by means of the integral methods, self-similar and analyt...
Flow analysis of an innovative compact heat exchanger channel geometry
International Nuclear Information System (INIS)
Vitillo, F.; Cachon, L.; Reulet, F.; Millan, P.
2016-01-01
Highlights: • An innovative compact heat transfer technology is proposed. • Experimental measurements are shown to validate the CFD model. • CFD simulations show various flow mechanisms. • Flow analysis is performed to study physical phenomena enhancing heat transfer. - Abstract: In the framework of CEA R&D program to develop an industrial prototype of sodium-cooled fast reactor named ASTRID, the present work aims to propose an innovative compact heat exchanger technology to provide solid technological basis for the utilization of a Brayton gas-power conversion system, in order to avoid the energetic sodium–water interaction if a traditional Rankine cycle was used. The aim of the present work is to propose an innovative compact heat exchanger channel geometry to potentially enhance heat transfer in such components. Hence, before studying the innovative channel performance, a solid experimental and numerical database is necessary to perform a preliminary thermal–hydraulic analysis. To do that, two experimental test sections are used: a Laser Doppler Velocimetry (LDV) test section and a Particle Image Velocimetry (PIV) test section. The acquired experimental database is used to validate the Anisotropic Shear Stress Transport (ASST) turbulence model. Results show a good agreement between LDV, PIV and ASST data for the pure aerodynamic flow. Once validated the numerical model, the innovative channel flow analysis is performed. Principal and secondary flow has been analyzed, showing a high swirling flow in the bend region and demonstrating that mixing actually occurs in the mixing zone. This work has to be considered as a step forward the preposition of a reliable high-performance component for application to ASTRID reactor as well as to any other industrial power plant dealing needing compact heat exchangers.
Heat transfer and fluid flow in regular rod arrays with opposing flow
International Nuclear Information System (INIS)
Yang, J.W.
1979-01-01
The heat transfer and fluid flow problem of opposing flow in the fully developed laminar region has been solved analytically for regular rod arrays. The problem is governed by two parameters: the pitch-to-diameter ratio and the Grashof-to-Reynolds number ratio. The critical Gr/Re ratios for flow separation caused by the upward buoyancy force on the downward flow were evaluated for a large range of P/D ratios of the triangular array. Numerical results reveal that both the heat transfer and pressure loss are reduced by the buoyancy force. Applications to nuclear reactors are discussed
Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam;
2013-01-01
Flow boiling and condensation have been identified as two key mechanisms for heat transport that are vital for achieving weight and volume reduction as well as performance enhancement in future space systems. Since inertia driven flows are demanding on power usage, lower flows are desirable. However, in microgravity, lower flows are dominated by forces other than inertia (like the capillary force). It is of paramount interest to investigate limits of low flows beyond which the flow is inertial enough to be gravity independent. One of the objectives of the Flow Boiling and Condensation Flight Experiment sets to investigate these limits for flow boiling and condensation. A two-phase flow loop consisting of a Flow Boiling Module and two Condensation Modules has been developed to experimentally study flow boiling condensation heat transfer in the reduced gravity environment provided by the reduced gravity platform. This effort supports the development of a flow boiling and condensation facility for the International Space Station (ISS). The closed loop test facility is designed to deliver the test fluid, FC-72 to the inlet of any one of the test modules at specified thermodynamic and flow conditions. The zero-g-aircraft tests will provide subcooled and saturated flow boiling critical heat flux and flow condensation heat transfer data over wide range of flow velocities. Additionally, these tests will verify the performance of all gravity sensitive components, such as evaporator, condenser and accumulator associated with the two-phase flow loop. We will present in this paper the breadboard development and testing results which consist of detailed performance evaluation of the heater and condenser combination in reduced and normal gravity. We will also present the design of the reduced gravity aircraft rack and the results of the ground flow boiling heat transfer testing performed with the Flow Boiling Module that is designed to investigate flow boiling heat transfer and
Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers
Directory of Open Access Journals (Sweden)
Hanuszkiewicz-Drapała Małgorzata
2016-03-01
Full Text Available A cross-flow, tube and fin heat exchanger of the water – air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.
Heat transfer enhancement in cross-flow heat exchanger using vortex generator
International Nuclear Information System (INIS)
Yoo, S. Y.; Kwon, H. K.; Kim, B. C.; Park, D. S.; Lee, S. S.
2003-01-01
Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator
Heat transfer in intermediate heat exchanger under low flow rate conditions
International Nuclear Information System (INIS)
Mochizuki, H.
2008-01-01
The present paper describes the heat transfer in intermediate heat exchangers (IHXs) of liquid metal cooled fast reactors when flow rate is low such as a natural circulation condition. Although empirical correlations of heat transfer coefficients for IHX were derived using test data at the fast reactor 'Monju' and 'Joyo' and also at the 50 MW steam generator facility, the heat transfer coefficient was very low compared to the well known correlation for liquid metals proposed by Seban-Shimazaki. The heat conduction in IHX was discussed as a possible cause of the low Nusselt number. As a result, the heat conduction is not significant under the natural circulation condition, and the heat conduction term in the energy equation can be neglected in the one-dimensional plant dynamics calculation. (authors)
Computational simulation of heat transfer in laser melted material flow
International Nuclear Information System (INIS)
Shankar, V.; Gnanamuthu, D.
1986-01-01
A computational procedure has been developed to study the heat transfer process in laser-melted material flow associated with surface heat treatment of metallic alloys to improve wear-and-tear and corrosion resistance. The time-dependent incompressible Navier-Stokes equations are solved, accounting for both convective and conductive heat transfer processes. The convection, induced by surface tension and high surface temperature gradients, sets up a counterrotating vortex flow within the molten pool. This recirculating material flow is responsible for determining the molten pool shape and the associated cooling rates which affect the solidifying material composition. The numerical method involves an implicit triple-approximate factorization scheme for the energy equation, and an explicit treatment for the momentum and the continuity equations. An experimental setup, using a continuous wave CO 2 laser beam as a heat source, has been carried out to generate data for validation of the computational model. Results in terms of the depth, width, and shape of the molten pool and the heat-affected zone for various power settings and shapes of the laser, and for various travel speeds of the workpiece, compare very well with experimental data. The presence of the surface tension-induced vortex flow is demonstrated
Preliminary heat flow map of Europe. Explanatory text
Energy Technology Data Exchange (ETDEWEB)
Cermak, V.; Hurtig, E.
1977-08-08
A preliminary heat flow map of Europe was prepared, based on data contained in 401 references. The map was prepared on a scale of 1:5,000,000 and shows broad-scale geological structure (e.g., platforms, shields, foredeeps) and specialized rock suites (ophiolites, volcanites). Primary faults and thrust faults are indicated, and contours showing the depth of crystalline basement are given. Heat flow is plotted using 10.0 mW/m/sup 2/ isotherms. The accompanying explanatory text describes data acquisition and techniques of correction, and discusses some implications of the results.
International Nuclear Information System (INIS)
Chasanov, M.G.; Gunther, W.H.; Baker, L. Jr.
1977-01-01
The capability for removal of heat from a pool of molten fuel under postaccident conditions is an important consideration in liquid-metal fast breeder reactor safety analysis. No experimental data for pool heat transfer from molten UO 2 under conditions simulating internal heat generation by fission product decay have been reported previously in the literature. An apparatus to provide such data was developed and used to investigate heat transfer from pools containing up to 7.5 kg of UO 2 ; the internal heat generation rates and pool depths attained cover most of the ranges of interest for postaccident heat removal analysis. It was also observed in these studies that the presence of simulated fission products corresponding to approximately 150,000 kW-day/kg burnup had no significant effect on the observed heat transfer
Thermal heat-balance mode flow-to-frequency converter
Pawlowski, Eligiusz
2016-11-01
This paper presents new type of thermal flow converter with the pulse frequency output. The integrating properties of the temperature sensor have been used, which allowed for realization of pulse frequency modulator with thermal feedback loop, stabilizing temperature of sensor placed in the flowing medium. The system assures balancing of heat amount supplied in impulses to the sensor and heat given up by the sensor in a continuous way to the flowing medium. Therefore the frequency of output impulses is proportional to the heat transfer coefficient from sensor to environment. According to the King's law, the frequency of those impulses is a function of medium flow velocity around the sensor. The special feature of presented solution is total integration of thermal sensor with the measurement signal conditioning system. Sensor and conditioning system are not the separate elements of the measurement circuit, but constitute a whole in form of thermal heat-balance mode flow-to-frequency converter. The advantage of such system is easiness of converting the frequency signal to the digital form, without using any additional analogue-to-digital converters. The frequency signal from the converter may be directly connected to the microprocessor input, which with use of standard built-in counters may convert the frequency into numerical value of high precision. Moreover, the frequency signal has higher resistance to interference than the voltage signal and may be transmitted to remote locations without the information loss.
Models for fluid flows with heat transfer in mixed convection
International Nuclear Information System (INIS)
Mompean Munhoz da Cruz, G.
1989-06-01
Second order models were studied in order to predict turbulent flows with heat transfer. The equations used correspond to the characteristic scale of turbulent flows. The order of magnitude of the terms of the equation is analyzed by using Reynolds and Peclet numbers. The two-equation model (K-ε) is applied in the hydrodynamic study. Two models are developed for the heat transfer analysis: the Prt + teta 2 and the complete model. In the first model, the turbulent thermal diffusivity is calculated by using the Prandtl number for turbulent flow and an equation for the variance of the temperature fluctuation. The second model consists of three equations concerning: the turbulent heat flow, the variance of the temperature fluctuation and its dissipation ratio. The equations were validated by four experiments, which were characterized by the analysis of: the air flow after passing through a grid of constant average temperature and with temperature gradient, an axysymmetric air jet submitted to high and low heating temperature, the mixing (cold-hot) of two coaxial jets of sodium at high Peclet number. The complete model is shown to be the most suitable for the investigations presented [fr
Coupled heat and groundwater flow in porous rock
International Nuclear Information System (INIS)
Rae, J.; Robinson, P.C.; Wickens, L.M.
1983-01-01
There are a number of technical areas where coupled heat and flow problems occur for water in porous rock. The area of most interest to the authors has been the possible disposal underground of high-level radioactive waste. High-level waste can emit enough heat to drive significant flows by buoyancy effects and groundwater flow is expected to be the chief transport process for solute leached from such a repository. The possible disposal of radioactive waste under the seabed raises many similar questions and needs similar techniques to find answers. Other areas where related questions arise are the storage and retrieval of hot water in underground reservoirs, the attempts to extract useful geothermal energy by pumping water into fracture systems in hot rock and in certain thermal techniques for persuading oil to flow in tight reservoirs. The authors address questions in a rather general way and give examples which lie more in the area of waste disposal
Directory of Open Access Journals (Sweden)
Yasuhisa Shinmoto
2017-11-01
Full Text Available The use of immiscible liquids for cooling of surfaces with high heat generation density is proposed based on the experimental verification of its superior cooling characteristics in fundamental systems of pool boiling and flow boiling in a tube. For the purpose of practical applications, however, heat transfer characteristics due to flow boiling in narrow rectangular channels with different small gap sizes need to be investigated. The immiscible liquids employed here are FC72 and water, and the gap size is varied as 2, 1, and 0.5 mm between parallel rectangular plates of 30 mm × 175 mm, where one plate is heated. To evaluate the effect of gap size, the heat transfer characteristics are compared at the same inlet velocity. The generation of large flattened bubbles in a narrow gap results in two opposite trends of the heat transfer enhancement due to thin liquid film evaporation and of the deterioration due to the extension of dry patch in the liquid film. The situation is the same as that observed for pure liquids. The latter negative effect is emphasized for extremely small gap sizes if the flow rate ratio of more-volatile liquid to the total is not reduced. The addition of small flow rate of less-volatile liquid can increase the critical heat flux (CHF of pure more-volatile liquid, while the surface temperature increases at the same time and assume the values between those for more-volatile and less-volatile liquids. By the selection of small flow rate ratio of more-volatile liquid, the surface temperature of pure less-volatile liquid can be decreased without reducing high CHF inherent in the less-volatile liquid employed. The trend of heat transfer characteristics for flow boiling of immiscible mixtures in narrow channels is more sensitive to the composition compared to the flow boiling in a round tube.
Flow instability and critical heat flux in a ribbed annulus
International Nuclear Information System (INIS)
Yang, B.W.; Dougherty, T.; Fighetti, C.; Kokolis, S.; Reddy, G.D.; McAssey, E.V. Jr.; Coutts, A.
1993-01-01
An experimental program has been conducted to determine the onset of flow instability point in a heated annulus which is divided into four sub channels by non-conducting ribs. The onset of flow instability is identified by the minimum point in the pressure drop-velocity curve. Comparison with a ribless annulus show that the presence of ribs increases the minimum point velocity. In addition, data are presented which show that under certain conditions premature CHF can be induced by the ribs
Elovic, E. (Editor); O'Brien, J. E. (Editor); Pepper, D. W. (Editor)
1988-01-01
The present conference on heat transfer characteristics of gas turbines and three-dimensional flows discusses velocity-temperature fluctuation correlations at the flow stagnation flow of a circular cylinder in turbulent flow, heat transfer across turbulent boundary layers with pressure gradients, the effect of jet grid turbulence on boundary layer heat transfer, and heat transfer characteristics predictions for discrete-hole film cooling. Also discussed are local heat transfer in internally cooled turbine airfoil leading edges, secondary flows in vane cascades and curved ducts, three-dimensional numerical modeling in gas turbine coal combustor design, numerical and experimental results for tube-fin heat exchanger airflow and heating characteristics, and the computation of external hypersonic three-dimensional flow field and heat transfer characteristics.
Modeling heat efficiency, flow and scale-up in the corotating disc scraped surface heat exchanger
DEFF Research Database (Denmark)
Friis, Alan; Szabo, Peter; Karlson, Torben
2002-01-01
A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer...... performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key...
Heat flow at the Platanares, Honduras, geothermal site
Meert, Joseph G.; Smith, Douglas L.
1991-03-01
Three boreholes, PLTG-1, PLTG-2 and PLTG-3, were drilled in the Platanares, Honduras geothermal system to evaluate the geothermal energy potential of the site. The maximum reservoir temperature was previously estimated at 225-240°C using various types of chemical and isotopic geothermometry. Geothermal gradients of 139-239°C/km, calculated from two segments of the temperature-depth profile for borehole PLTG-2, were used to project a minimum depth to the geothermal reservoir of 1.2-1.7 km. Borehole PLTG-1 exhibited an erratic temperature distribution attributed to fluid movement through a series of isolated horizontal and subhorizontal fractures. The maximum measured temperature in borehole PLTG-1 was 150.4°C, and in PLTG-2 the maximum measured temperature was 104.3°C. PLTG-3 was drilled after this study and the maximum recorded temperature of 165°C is similar to the temperature encountered in PLTG-1. Heat flow values of 392 mWm -2 and 266 mWm -2 represent the first directly-measured heat flow values for Honduras and northen Central America. Radioactive heat generation, based on gamma-ray analyses of uranium, thorium and potassium in five core samples, is less than 2.0 μWm -3 and does not appear to be a major source of the high heat flow. Several authors have proposed a variety of extensional tectonic environments for western Honduras and these heat flow values, along with published estimates of heat flow, are supportive of this type of tectonic regime.
Flow Boiling and Condensation Experiment (FBCE) for the International Space Station
Mudawar, Issam; O'Neill, Lucas; Hasan, Mohammad; Nahra, Henry; Hall, Nancy; Balasubramaniam, R.; Mackey, Jeffrey
2016-01-01
An effective means to reducing the size and weight of future space vehicles is to replace present mostly single-phase thermal management systems with two-phase counterparts. By capitalizing upon both latent and sensible heat of the coolant rather than sensible heat alone, two-phase thermal management systems can yield orders of magnitude enhancement in flow boiling and condensation heat transfer coefficients. Because the understanding of the influence of microgravity on two-phase flow and heat transfer is quite limited, there is an urgent need for a new experimental microgravity facility to enable investigators to perform long-duration flow boiling and condensation experiments in pursuit of reliable databases, correlations and models. This presentation will discuss recent progress in the development of the Flow Boiling and Condensation Experiment (FBCE) for the International Space Station (ISS) in collaboration between Purdue University and NASA Glenn Research Center. Emphasis will be placed on the design of the flow boiling module and on new flow boiling data that were measured in parabolic flight, along with extensive flow visualization of interfacial features at heat fluxes up to critical heat flux (CHF). Also discussed a theoretical model that will be shown to predict CHF with high accuracy.
Flow and Convective Heat Transfer of Cylinder Misaligned from Aerodynamic Axis of Cyclone Flow
Directory of Open Access Journals (Sweden)
I. L. Leukhin
2008-01-01
Full Text Available The paper provides and analyzes results of experimental investigations on physical specific features of hydrodynamics and convective heat transfer of a cyclone flow with a group of round cylinders located symmetrically relative to its aerodynamic axis, calculative equations for average and local heat transfer factors at characteristic sections of cylinder surface.
Local heat transfer where heated rods touch in axially flowing water
International Nuclear Information System (INIS)
Kast, S.J.
1983-05-01
An anlaytic model is developed to predict the azimuthal width of a stablesteam blanket region near the line of contact between two heated rods cooled by axially flowing water at high pressure. The model is intended to aid analysis of reduced surface heat transfer capability for the abnormal configuration of nuclear fuel rods bowed into contact in the core of a pressurized water nuclear reactor. The analytic model predicts the azimuthal width of the steam blanket zone having reduced surface heat transfer as a function of rod average heat flux, subchannel coolant conditions and rod dimensions. The analytic model is developed from a heat balance between the heat generated in the wall of a heated empty tube and the heat transported away by transverse mixing and axial convection in the coolant subchannel. The model is developed for seveal geometries including heated rods in line contact, a heated rod touching a short insulating plane and a heated rod touching the inside of a metal guide tube
History of heat pumps - Swiss contributions and international milestones
Energy Technology Data Exchange (ETDEWEB)
Zogg, M
2008-05-15
Compared to conventional boilers, heating by heat pumps cuts down fuel consumption and CO{sub 2} emissions to about 50%. Compared to electric resistance heating, the energy consumption is even reduced up to 80%. Therefore, the impressive market penetration growth of heat pumps will continue. Swiss pioneers were the first to realize functioning vapour recompression plants. The first European heat pumps were realized in Switzerland. To date it remains one of the heat pump champions. Swiss pioneering work in the development of borehole heat exchangers, sewage heat recovery, oil free piston compressors and turbo compressors is well known. The biggest heat pump ever built comes from Switzerland. Although there is a fairly comprehensive natural gas distribution grid, 75% of the new single-family homes built in Switzerland are currently heated by heat pumps. This paper presents some of the highlights of this success story focusing on Swiss developments and relating them to the international milestones. In order to indicate the direction in which the future development might go to, some recent Swiss research projects are presented as well. (author)
Heat flow in Indian Gondwana basins and heat production of their basement rocks
Energy Technology Data Exchange (ETDEWEB)
Rao, G.V.; Rao, R.U.M.
1983-01-01
Temperatures have been measured in eight boreholes (ranging from 260 to 800 m in depth) in five Gondwana basins of the Damodar and Son valleys. With the aid of about 250 thermal conductivity determinations on core samples from these holes, heat flow has been evaluated. Measurements of radioactive heat generation have been made on samples of Precambrian gneisses constituting the basement for the Sonhat (Son valley) and Chintalapudi (Godavari valley) basins. Heat-flow values from all of the Damodar valley basins are within the narrow range of 69-79 mW/m exp(2). The value from the Sonhat basin (107 mW/m exp(2)) is significantly higher. The generally high heat flows observed in Gondwana basins of India cannot be attributed to the known tectonism or igneous activity associated with these basins. The plots of heat flow vs. heat generation for three Gondwana basins (Jharia, Sonhat and Chintalapudi) are on the same line as those of three regions in the exposed Precambrian crystalline terrains in the northern part of the Indian shield. This indicates that the crust under exposed regions of the Precambrian crystalline rocks as well as the Gondwana basins, form an integral unit as far as the present-day geothermal character is concerned. (5 figs., 14 refs., 4 tables).
Heat flow in Indian Gondwana basins and heat production of their basement rocks
Rao, G. V.; Rao, R. U. M.
1983-01-01
Temperatures have been measured in eight boreholes (ranging from 260 to 800 m in depth) in five Gondwana basins of the Damodar and Son valleys. With the aid of about 250 thermal conductivity determinations on core samples from these holes, heat flow has been evaluated. Measurements of radioactive heat generation have been made on samples of Precambrian gneisses constituting the basement for the Sonhat (Son valley) and Chintalapudi (Godavari valley) basins. Heat-flow values from all of the Damodar valley basins are within the narrow range of 69-79 mW/m 2. The value from the Sonhat basin (107 mW/m 2) is significantly higher. The generally high heat flows observed in Gondwana basins of India cannot be attributed to the known tectonism or igneous activity associated with these basins. The plots of heat flow vs. heat generation for three Gondwana basins (Jharia, Sonhat and Chintalapudi) are on the same line as those of three regions in the exposed Precambrian crystalline terrains in the northern part of the Indian shield. This indicates that the crust under exposed regions of the Precambrian crystalline rocks as well as the Gondwana basins, form an integral unit as far as the present-day geothermal character is concerned.
International Nuclear Information System (INIS)
Yang Ruichang; Liu Ruolei; Zhong Yong; Liu Tao
2006-01-01
This paper reports on an experimental study on transitional heat transfer of water flow in a heated vertical tube under natural circulation conditions. In the experiments the local and average heat transfer coefficients were obtained. The experimental data were compared with the predictions by a forced flow correlation available in the literature. The comparisons show that the Nusselt number value in the fully developed region is about 30% lower than the predictions by the forced flow correlation due to flow laminarization in the layer induced by co-current bulk natural circulation and free convection. By using the Rayleigh number Ra to represent the influence of free convection on heat transfer, the empirical correlations for the calculation of local and average heat transfer behavior in the tube at natural circulation have been developed. The empirical correlations are in good agreement with the experimental data. Based on the experimental results, the effect of the thermal entry-length behavior on heat transfer design in the tube under natural circulation was evaluated
Flow induced vibration in shell and tube heat exchangers
International Nuclear Information System (INIS)
Soper, B.M.H.
1981-01-01
Assessing heat exchanger designs, from the standpoint of flow induced vibration, is becoming increasingly important as shell side flow velocities are increased in a quest for better thermal performance. This paper reviews the state of the art concerning the main sources of vibration excitation, i.e. vortex shedding resonance, turbulent buffeting, fluidelastic instability and acoustic resonance, as well as the structural dynamics of the tubes. It is concluded that there are many areas which require further investigation but there are sufficient data available at present to design, with reasonable confidence, units that will be free from flow induced vibration. Topics which are considered to be key areas for further work are listed
Gravity influence on heat transfer rate in flow boiling
Baltis, C.H.M.; Celata, G.P.; Cumo, M.; Saraceno, L.; Zummo, G.
2012-01-01
The aim of the present paper is to describe the results of flow boiling heat transfer at low gravity and compare them with those obtained at earth gravity, evaluating possible differences. The experimental campaigns at low gravity have been performed with parabolic flights. The paper will show the
Characterizing the Heat Flow from Between Enceladus' Tiger Stripes
Howett, C.; Spencer, J. R.; Verbiscer, A.
2017-12-01
Enceladus' heat flow provides a fundamental constraint on its tidal dissipation mechanisms, orbital evolution, and the physical processes that generate the plumes. Determining the total amount of emission is proving difficult, as different techniques produce differing constraints. For example, an initial estimate of this value, 5.8±1.3 GW, was made by Spencer et al. (2006) using Cassini Composite Infrared Spectrometer (CIRS) 600 to 1100 cm-1 observations, which was refined using 10 to 600 cm-1 CIRS observations to 15.8±3.1 GW by Howett et al. (2011). However, recent reanalysis of high-spatial resolution 10 to 1100 cm-1 CIRS observations of Enceladus' active south polar region conducted by Spencer and Howett gives a heat flow of 4.64±0.23 GW. Whilst all of these heat flow estimates are much larger than those expected in a steady state, 1.1 GW (Meyer and Wisdom, 2007), their obvious discrepancy is a puzzle. In this work we seek to help understand these discrepancies by determining how much endogenic heat flow is coming from the funiscular terrain between Enceladus active tiger stripes.
Occurrence of critical heat flux during blowdown with flow reversal
International Nuclear Information System (INIS)
Leung, J.C.M.
1976-04-01
A small-scale experiment using Freon-11 at 130 0 F and 65 psia in a well-instrumented transparent annular test section was used to study the occurrence of critical heat flux (CHF) during blowdown with flow reversal. The inner stainless steel tube of the annulus was uniformly heated over its 2 ft length. Inlet and exit void fractions were measured by a capacitance technique. Flow regime transition was observed with high speed photography. A 1-hr contact time between Freon-11 and nitrogen at 130 0 F and 60 psig was found to greatly affect the steady-state subcooled boiling initial conditions. Delay in bubble growth was observed in adiabatic blowdown runs. This was caused by the thermodynamic nonequilibrium conditions required for the unstable bubble growth. For the diabatic runs, equilibrium was more closely approached in the test section during the early phase of blowdown. Critical heat flux did not occur immediately during the flow decay in an approximately 60 msec reversal period. The first or early CHF which occurred at about 400 msec was independent of the blowdown volume and did not propagate upward. An annular flow pattern appeared at the onset of this CHF which occurred only at the lower 8 in. of the heated zone
On the Curvature and Heat Flow on Hamiltonian Systems
Directory of Open Access Journals (Sweden)
Ohta Shin-ichi
2014-01-01
Full Text Available We develop the differential geometric and geometric analytic studies of Hamiltonian systems. Key ingredients are the curvature operator, the weighted Laplacian, and the associated Riccati equation.We prove appropriate generalizations of the Bochner-Weitzenböck formula and Laplacian comparison theorem, and study the heat flow.
Direct numerical simulation of particulate flow with heat transfer
Tavassoli Estahbanati, H; Kriebitzsch, S.H.L.; Hoef, van der M.A.; Peters, E.A.J.F.; Kuipers, J.A.M.
2013-01-01
The Immersed Boundary (IB) method proposed by Uhlmann for Direct Numerical Simulation (DNS) of fluid flow through dense fluid-particle systems is extended to systems with interphase heat transport. A fixed Eulerian grid is employed to solve the momentum and energy equations by traditional
Time-Dependent Natural Convection Couette Flow of Heat ...
African Journals Online (AJOL)
Time-Dependent Natural Convection Couette Flow of Heat Generating/Absorbing Fluid between Vertical Parallel Plates Filled With Porous Material. ... The numerical simulation conducted for some saturated liquids reveled that at t ≥ Pr the steady and unsteady state velocities (as well as the temperature of the fluid) ...
EFFECTS OF HEAT-FLOW AND HYDROTHERMAL FLUIDS FROM ...
African Journals Online (AJOL)
Volcanic intrusions and hydrothermal activity have modified the diagenetic minerals. In the Ulster Basin, UK, most of the authigenic mineralization in the Permo-Triassic sandstones pre-dated tertiary volcanic intrusions. The hydrothermal fluids and heat-flow from the volcanic intrusions did not affect quartz and feldspar ...
Geothermal heat exchanger with coaxial flow of fluids
Directory of Open Access Journals (Sweden)
Pejić Dragan M.
2005-01-01
Full Text Available The paper deals with a heat exchanger with coaxial flow. Two coaxial pipes of the secondary part were placed directly into a geothermal boring in such a way that geothermal water flows around the outer pipe. Starting from the energy balance of the exchanger formed in this way and the assumption of a study-state operating regime, a mathematical model was formulated. On the basis of the model, the secondary circle output temperature was determined as a function of the exchanger geometry, the coefficient of heat passing through the heat exchange areas, the average mass isobaric specific heats of fluid and mass flows. The input temperature of the exchanger secondary circle and the temperature of the geothermal water at the exit of the boring were taken as known values. Also, an analysis of changes in certain factors influencing the secondary water temperature was carried out. The parameters (flow temperature of the deep boring B-4 in Sijarinska Spa, Serbia were used. The theoretical results obtained indicate the great potential of this boring and the possible application of such an exchanger.
Study on boiling heat transfer of subcooled flow under oscillatory flow condition
International Nuclear Information System (INIS)
Ohtake, Hiroyasu; Yamazaki, Satoshi; Koizumi, Yasuo
2004-01-01
The Onset of Nucleate Boiling, the point of Net Vapor Generation and Critical Heat Flux on subcooled flow boiling under oscillatory flow, focusing on liquid velocity, amplitude and frequency of oscillatory flow were investigated experimentally and analytically. Experiments were conducted using a copper thin-film and subcooled water in a range of the liquid velocity from 0.27 to 4.07 m/s at 0.10MPa. The liquid subcooling was 20K. Frequency of oscillatory flow was 2 and 4 Hz, respectively; amplitude of oscillatory flow was 25 and 50% in a ratio of main flow rate, respectively. Temperatures at Onset of Nuclear Boiling and Critical Heat Flux obtained in the experiments decreased with the oscillatory flow. The decrease of liquid velocity by oscillatory flow caused the ONB and the CHF to decrease. On the other hand, heat flux at Net Vapor Generation decreased with oscillatory flow; the increase of liquid velocity by oscillatory flow caused the NVG to decrease. (author)
Buoyancy induced convective flow in porous media with heat source
International Nuclear Information System (INIS)
Hwang, I.T.
1978-01-01
An unbounded fluid layer in a porous medium with an internal heat source and uniformly heated from below is studied. The layer is in the gravitational field. Linear theory predicts that the disturbances of infinitesimal amplitude will start to grow when the Rayleigh number exceeds its critical value. These disturbances do not grow without limit; but by advecting heat and momentum, the disturbances alter their forms to achieve a finite amplitude. Just like infinitesimal amplitude disturbances the degeneracies of possible solutions persist for finite amplitude solutions. This study evaluates these various forms of solutions. The small parameter method of Poincare is used to treat the problem in successive order
Experimental and analytical study of natural-convection heat transfer of internally heated liquids
International Nuclear Information System (INIS)
Green, G.A.
1982-08-01
Boundary heat transfer from a liquid pool with a uniform internal heat source to a vertical or inclined boundary was investigated. The experiments were performed in an open rectangular liquid pool in which the internal heat source was generated by electrical heating. The local heat flux was measured to a boron nitride test wall which was able to be continuously inclined from vertical. Gold plated microthermocouples of 0.01 inch outside diameter were developed to measure the local surface temperature, both front and back, of the boron nitride. The local heat flux and, thus, the local heat transfer coefficient was measured at nineteen locations along the vertical axis of the test plate. A theoretical analysis of the coupled nonlinear boundary layer equations was performed. The parametric effect of the Prandtl number and the dimensionless wall temperature on the boundary heat transfer were investigated When the analytical model was used to calculate the boundary heat transfer data, agreement was achieved with the experimental data within 3% for the local heat transfer and within 2% for the average heat transfer
A review of the heat flow data of NE Morocco
Chiozzi, Paolo; Barkaoui, Alae-Eddine; Rimi, Abdelkrim; Verdoya, Massimo; Zarhloule, Yassine
2016-04-01
The Atlas chain is characterised by a SW-NE trending volcanic belt roughly extending from the Atlantic to the Mediterranean Sea and showing activity that spans in age mainly from Middle Miocene to Quaternary (14.6-0.3 Ma). The geochemical features of volcanism are mostly intraplate and alkaline with the exception of the northeastern termination of the belt where calc-alkaline series crop out. Lithospheric thermal and density models so far proposed, constrained by heat flow, gravity anomalies, geoid, and topography data, show that the Atlas chain is not supported isostatically by a thickened crust and a thin, hot and low-density lithosphere explains the high topography. One of the possible explanations for lithospheric mantle thinning, possibly in relation with the observed alkaline volcanism, is thermal erosion produced by either small-scale convection or activation of a small mantle plume, forming part of a hot and deep mantle reservoir system extending from the Canary Islands. This paper focuses on the several geothermal data available in the northeastern sector of the volcanic belt. The occurrence of an extensive, often artesian, carbonatic reservoir hosting moderately hot groundwater might boost the temperature gradient in the overlying impermeable cover, and consequently mask the deep thermal regime. We therefore revised the available dataset and investigated the contribution of advection. Temperature data available from water and oil wells were reprocessed and analysed in combination with thermal conductivity measurements on a wide set of lithotypes. Data were filtered according to rigid selection criteria, and, in the deeper boreholes, the heat flow was inferred by taking into account the porosity variation with depth and the temperature effect on the matrix and pore-filling fluid conductivity. Moreover, the possible effect of advection was evaluated with simple analytical models which envisage the carbonatic layers as confined aquifers heated by the
A study on heat transfer enhancement using flow channel inserts for thermoelectric power generation
International Nuclear Information System (INIS)
Lesage, Frédéric J.; Sempels, Éric V.; Lalande-Bertrand, Nathaniel
2013-01-01
Highlights: • Thermal enhancement in a thermoelectric liquid generator is tested. • Thermal enhancement is brought upon by flow impeding inserts. • CFD simulations attribute thermal enhancement to velocity field alterations. • Thermoelectric power enhancement is measured and discussed. • Power enhancement relative to adverse pressure drop is investigated. - Abstract: Thermoelectric power production has many potential applications that range from microelectronics heat management to large scale industrial waste-heat recovery. A low thermoelectric conversion efficiency of the current state of the art prevents wide spread use of thermoelectric modules. The difficulties lie in material conversion efficiency, module design, and thermal system management. The present study investigates thermoelectric power improvement due to heat transfer enhancement at the channel walls of a liquid-to-liquid thermoelectric generator brought upon by flow turbulating inserts. Care is taken to measure the adverse pressure drop due to the presence of flow impeding obstacles in order to measure the net thermoelectric power enhancement relative to an absence of inserts. The results illustrate the power enhancement performance of three different geometric forms fitted into the channels of a thermoelectric generator. Spiral inserts are shown to offer a minimal improvement in thermoelectric power production whereas inserts with protruding panels are shown to be the most effective. Measurements of the thermal enhancement factor which represents the ratio of heat flux into heat flux out of a channel and numerical simulations of the internal flow velocity field attribute the thermal enhancement resulting in the thermoelectric power improvement to thermal and velocity field synergy
Surface roughness effects on heat transfer in Couette flow
International Nuclear Information System (INIS)
Elia, G.G.
1981-01-01
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.)
Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube
International Nuclear Information System (INIS)
Boscary, J.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance
1997-03-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)
Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow
International Nuclear Information System (INIS)
Boscary, J.
1995-10-01
The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs
Heat transfer 1990. Proceedings of the ninth international heat transfer conference
International Nuclear Information System (INIS)
Hetsroni, G.
1990-01-01
This book contains the proceedings of the Ninth International Heat Transfer Conference. Included in Volume 3 are the following chapters: Refrigerant vapor condensation on a horizontal tube bundle. Local heat transfer in a reflux condensation inside a closed two-phase thermosyphon and surface temperature by means of a pulsed photothermal effects
Nonlinear throughflow and internal heating effects on vibrating porous medium
Directory of Open Access Journals (Sweden)
Palle Kiran
2016-06-01
Full Text Available The effect of vertical throughflow and internal heating effects on fluid saturated porous medium under gravity modulation is investigated. The amplitude of modulation is considered to be very small and the disturbances are expanded in terms of power series of amplitude of convection. A weakly nonlinear stability analysis is proposed to study stationary convection. The Nusselt number is obtained numerically to present the results of heat transfer while using Ginzburg–Landau equation. The vertical throughflow has dual effect either to destabilize or to stabilize the system for downward or upward directions. The effect of internal heat source (Ri>0 enhances or sink (Ri<0 diminishes heat transfer in the system. The amplitude and frequency of modulation have the effects of increasing or diminishing heat transport. For linear model Venezian approach suggested that throughflow and internal heating have both destabilizing and stabilizing effects for suitable ranges of Ω. Further, the study establishes that heat transport can be controlled effectively by a mechanism that is external to the system throughflow and gravity modulation.
Free convection flow and heat transfer in pipe exposed to cooling
Energy Technology Data Exchange (ETDEWEB)
Mme, Uduak Akpan
2010-10-15
One of the challenges with thermal insulation design in subsea equipment is to minimize the heat loss through cold spots during production shut down. Cold spots are system components where insulation is difficult to implement, resulting in an insulation discontinuity which creates by nature a thermal bridge. It is difficult to avoid cold spots or thermal bridges in items like sensors, valves, connectors and supporting structures. These areas of reduced or no insulation are referred to as cold spots. Heat is drained faster through these spots, resulting in an increased local fluid density resulting in an internal fluid flow due to gravity and accelerated cool- down. This natural convection flow is important for both heat loss and internal distribution of the temperature. This thesis is presenting both experimental work and modelling work. A series of cool down tests and Computational Fluid Dynamics (CFD) simulations of these tests are presented. These tests and simulations were carried out in order to understand the flow physics involved in heat exchange processes caused by free convection flow in pipe exposed to cooling. Inclination of the pipe relative to the direction of gravity and temperature difference between cooling water and internal pipe water are the two main parameters investigated in this study. The experimental heat removal and temperature field is discussed and further interpreted by means of computational fluid dynamics. For prediction of the evolvement of the local temperature and heat flow, selection of an appropriate turbulence model is critical. Hence, different models and wall functions are investigated. The predicted temperature profiles and heat extraction rates are compered to the experiments for the selected turbulence models. Our main conclusions, supported by our experimental and CFD results, include: (i) Heat transfer from a localized cold spot in an inclined pipe is most efficient when the pipe orientation is close to horizontal. As the
Analysis of fluid flow and heat transfer in a double pipe heat exchanger with porous structures
International Nuclear Information System (INIS)
Targui, N.; Kahalerras, H.
2008-01-01
A numerical study of flow and heat transfer characteristics is made in a double pipe heat exchanger with porous structures inserted in the annular gap in two configurations: on the inner cylinder (A) and on both the cylinders in a staggered fashion (B). The flow field in the porous regions is modelled by the Darcy-Brinkman-Forchheimer model and the finite volume method is used to solve the governing equations. The effects of several parameters such as Darcy number, porous structures thickness and spacing and thermal conductivity ratio are considered in order to look for the most appropriate properties of the porous structures that allow optimal heat transfer enhancement. It is found that the highest heat transfer rates are obtained when the porous structures are attached in configuration B especially at small spacing and high thicknesses
Heat conduction boundary layers of condensed clumps in cooling flows
International Nuclear Information System (INIS)
Boehringer, H.; Fabian, A.C.
1989-01-01
The structure of heat conduction boundary layers of gaseous condensations embedded in the hot intergalactic gas in clusters of galaxies is investigated by means of steady, one-dimensional, hydrodynamic models. It is assumed that heat conduction is effective only on scales much smaller than the total region of the cooling flow. Models are calculated for an arbitrary scaling factor, accounting for the reduction in heat conduction efficiency compared to the classical Spitzer case. The results imply a lower limit to the size spectrum of the condensations. The enhancement of cooling in the ambient medium due to heat conduction losses is calculated for a range of clump parameters. The luminosity of several observable emission lines, the extreme ultraviolet (EUV) and soft X-ray emission spectrum, and the column density of some important ions are determined for the model boundary layers and compared with observations. (author)
An Engineering Aerodynamic Heating Method for Hypersonic Flow
Riley, Christopher J.; DeJarnette, Fred R.
1992-01-01
A capability to calculate surface heating rates has been incorporated in an approximate three-dimensional inviscid technique. Surface streamlines are calculated from the inviscid solution, and the axisymmetric analog is then used along with a set of approximate convective-heating equations to compute the surface heat transfer. The method is applied to blunted axisymmetric and three-dimensional ellipsoidal cones at angle of attack for the laminar flow of a perfect gas. The method is also applicable to turbulent and equilibrium-air conditions. The present technique predicts surface heating rates that compare favorably with experimental (ground-test and flight) data and numerical solutions of the Navier-Stokes (NS) and viscous shock-layer (VSL) equations. The new technique represents a significant improvement over current engineering aerothermal methods with only a modest increase in computational effort.
Heat transfer in laminar flow for a finned double - tube
International Nuclear Information System (INIS)
Colle, S.
1977-01-01
An analitical study of the steady-state heat transfer in laminar flow in finned double-tube heat exchangers is presented. The fins are plane, straight and continous, equally spaced and are fixed over the external surface of the inner tube. A constant peripheral temperature distribution is assumed to apply over the inner tube surface and each fin, and a constant peripheral heat flux is assumed to apply over the outer tube surface, while the overall heat flux is suposed to be uniform in the longitudinal direction of the duct. The prediction of the thermal performance of the finned double-tube is made by means of the relationship between the Nusselt number, the boundary conditions and the geometric characteristcs of the duct. (author) [pt
Analysis of flow induced vibration in heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Beek, A.W. van [Institute for Mechanical Constructions TNO, Delft (Netherlands)
1977-12-01
A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)
Analysis of flow induced vibration in heat exchangers
International Nuclear Information System (INIS)
Beek, A.W. van
1977-01-01
A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)
On dryout heat flux and pressure drop of a submerged inductively heated bed flow from below
International Nuclear Information System (INIS)
Tsai, F.F.; Catton, I.
1983-01-01
An experimental investigation of dryout heat flux in a saturated porous medal with forced flow from below has been conducted using methanol as a coolant. The mass flux varied from 0 to 0.557 kg/m 2 sec. Particle sizes were 590-790 μm, 1.6 mm, 3.2 mm, and 4.8 mm. The dryout heat flux increases as the mass flux increases, and asymptotically goes to the total evaporation energy of the inlet flow. The pressure drop across the bed changed very rapidly near the dryout point due to the formation of dry zone
International Nuclear Information System (INIS)
Meng Xianke; Sun Zhongning; Xu Guangzhan
2012-01-01
Graphical abstract: The core of the water-cooled pebble bed reactor is the porous channels which stacked with spherical fuel elements. The gaps between the adjacent fuel elements are complex because they are stochastic and often shift. We adopt electromagnetic induction heating method to overall heat the pebble bed. By comparing and analyzing the experimental data, we get the rule of power distribution and the rule of heat transfer coefficient with particle diameter, heat flux density, inlet temperature and working fluid's Re number. Highlights: ► We adopt electromagnetic induction heating method to overall heat the pebble bed to be the internal heat source. ► The ball diameter is smaller, the effect of the heat transfer is better. ► With Re number increasing, heat transfer coefficient is also increasing and eventually tends to stabilize. ► The changing of heat power makes little effect on the heat transfer coefficient of pebble bed channels. - Abstract: The reactor core of a water-cooled pebble bed reactor includes porous channels that are formed by spherical fuel elements. This structure has notably improved heat transfer. Due to the variability and randomness of the interstices in pebble bed channels, heat transfer is complex, and there are few studies regarding this topic. To study the heat transfer characters of pebble bed channels with internal heat sources, oxidized stainless steel spheres with diameters of 3 and 8 mm and carbon steel spheres with 8 mm diameters are used in a stacked pebble bed. Distilled water is used as a refrigerant for the experiments, and the electromagnetic induction heating method is used to heat the pebble bed. By comparing and analyzing the experimental results, we obtain the governing rules for the power distribution and the heat transfer coefficient with respect to particle diameter, heat flux density, inlet temperature and working fluid Re number. From fitting of the experimental data, we obtain the dimensionless average
Network model of free convection within internally heated porous media
International Nuclear Information System (INIS)
Conrad, P.W.
1977-01-01
A hypothetical core-disruptive accident (HCDA) in a liquid metal fast breeder reactor (LMFBR) may result in the formation of an internally heated debris bed. Considerable attention has been given to postulated mechanisms by which such beds may be cooled. It is the purpose of the work described to demonstrate a method for computing the heat transfer from such a bed to the overlying sodium pool due to single-phase, free convection
Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed
International Nuclear Information System (INIS)
Honda, Ryosuke; Umekawa, Hisashi; Ozawa, Mamoru
2009-01-01
Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.
Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed
Energy Technology Data Exchange (ETDEWEB)
Honda, Ryosuke [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Umekawa, Hisashi [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)], E-mail: umekawa@kansai-uac.jp; Ozawa, Mamoru [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)
2009-06-21
Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.
A high performance cocurrent-flow heat pipe for heat recovery applications
Saaski, E. W.; Hartl, J. C.
1980-01-01
By the introduction of a plate-and-tube separator assembly into a heat pipe vapor core, it has been demonstrated that axial transport capacity in reflux mode can be improved by up to a factor of 10. This improvement is largely the result of eliminating the countercurrent shear that commonly limits reflux heat pipe axial capacity. With benzene, axial heat fluxes up to 1800 W/sq cm were obtained in the temperature range 40 to 80 C, while heat flux densities up to 3000 W/sq cm were obtained with R-11 over the temperature range 40 to 80 C. These very high axial capacities compare favorably with liquid metal limits; the sonic limit for liquid sodium, for example, is 3000 W/sq cm at 657 C. Computational models developed for these cocurrent flow heat pipes agreed with experimental data within + or - 25%.
Enhancing heat transfer in microchannel heat sinks using converging flow passages
International Nuclear Information System (INIS)
Dehghan, Maziar; Daneshipour, Mahdi; Valipour, Mohammad Sadegh; Rafee, Roohollah; Saedodin, Seyfolah
2015-01-01
Highlights: • The fluid flow and conjugate heat transfer in microchannel heat sinks are studied. • The Poiseuille and Nusselt numbers are presented for width-tapered MCHS. • Converging walls are found to enhance the thermal performance of MCHS. • The optimum performance of MCHS for fixed inlet and outlet pressures is discussed. • For the optimum configuration, the pumping power is reduced up to 75%. - Abstract: Constrained fluid flow and conjugate heat transfer in microchannel heat sinks (MCHS) with converging channels are investigated using the finite volume method (FVM) in the laminar regime. The maximum pressure of the MCHS loop is assumed to be limited due to constructional or operational conditions. Results show that the Poiseuille number increases with increased tapering, while the required pumping power decreases. Meanwhile, the Nusselt number increases with tapering as well as the convection heat transfer coefficient. The MCHS having the optimum heat transfer performance is found to have a width-tapered ratio equal to 0.5. For this tapering configuration and at the maximum pressure constraint of 3000 Pa, the pumping power reduces by a factor of 4 while the overall heat removal rate is kept fixed in comparison with a straight channel
Directory of Open Access Journals (Sweden)
Mikielewicz Dariusz
2014-09-01
Full Text Available In the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for flow boiling and also flow condensation for some recent data collected from literature for such fluids as R404a, R600a, R290, R32,R134a, R1234yf and other. The modification of interface shear stresses between flow boiling and flow condensation in annular flow structure are considered through incorporation of the so called blowing parameter. The shear stress between vapor phase and liquid phase is generally a function of nonisothermal effects. The mechanism of modification of shear stresses at the vapor-liquid interface has been presented in detail. In case of annular flow it contributes to thickening and thinning of the liquid film, which corresponds to condensation and boiling respectively. There is also a different influence of heat flux on the modification of shear stress in the bubbly flow structure, where it affects bubble nucleation. In that case the effect of applied heat flux is considered. As a result a modified form of the two-phase flow multiplier is obtained, in which the nonadiabatic effect is clearly pronounced.
Heat Flow, Regional Geophysics and Lithosphere Structure In The Czech Republic
Safanda, J.; Cermak, V.; Kresl, M.; Dedecek, P.
Paper summarises and critically revises heat flow data that have been collected in the Czech Republic to date. The regional heat flow density map was prepared in view of all existing heat flow data completed with the similar in the surrounding countries and taking into consideration also temperature measurements in deep boreholes. Crustal temperature profiles were calculated by using the available geological information, results of deep seismic sounding and the laboratory data on radiogenic heat produc- tion and thermal conductivity. Special attention was paid to numerous temperature logs in two sedimentary basins, namely in the Cheb and Ostrava-Karvina coal basins, for which detailed heat flow patterns were proposed. Relationships between heat flow distribution and the crustal/lithosphere evolution, between heat flow and the heat pro- duction of the crustal rocks, heat flow and crustal thickness and the steady-state vs. transient heat transport are discussed.
Heat Transfer Enhancement in Turbulent Flows by Blocked Surfaces
Directory of Open Access Journals (Sweden)
Onur YEMENİCİ
2013-04-01
Full Text Available In this study, the heat transfer analyses over flat and blocked surfaces were carried out in turbulent flow under the influence of the block height. A constant-temperature hot wire anemometer was used to the velocity and turbulent intensity measurements, while temperature values were measured by copper-constantan thermocouples. The average Stanton numbers for block heights of 15 and 25 mm were higher than those of flat surface by %38 and %84, respectively. The results showed that the presence of the blocks increased the heat transfer and the enhancement rose with block heights
Heat transfer and fluid flow in nuclear systems
Fenech, Henri
1982-01-01
Heat Transfer and Fluid in Flow Nuclear Systems discusses topics that bridge the gap between the fundamental principles and the designed practices. The book is comprised of six chapters that cover analysis of the predicting thermal-hydraulics performance of large nuclear reactors and associated heat-exchangers or steam generators of various nuclear systems. Chapter 1 tackles the general considerations on thermal design and performance requirements of nuclear reactor cores. The second chapter deals with pressurized subcooled light water systems, and the third chapter covers boiling water reacto
Steady parallel flow in an evaporating fluid heated from sidewalls
International Nuclear Information System (INIS)
Das, Kausik S.
2009-01-01
Evaporation is ubiquitous in nature, but very few attempts have been made in the past to couple the effects of evaporation with fluid flow behavior. In this theoretical paper we have discussed the effects of evaporation on the dynamics of steady state thermocapillary convection in a two-dimensional rectangular container. The liquid is heated by differentially heated sidewalls and mass loss from the interface due to evaporation is compensated by the liquid entering into the container through a lower inlet, thus keeping the thickness of the liquid layer constant. We show that for an evaporating liquid one can obtain a plane parallel base state profile which depends on the evaporative mass flux.
Heat and mass transfer in porous cavity: Assisting flow
Energy Technology Data Exchange (ETDEWEB)
Badruddin, Irfan Anjum [Dept. of Mechanical Engineering, University of Malaya, Kuala Lumpur, 50603 (Malaysia); Quadir, G. A. [School of Mechatronic Engineering, University Malaysia Perlis, Pauh Putra, 02600 Arau, Perlis (Malaysia)
2016-06-08
In this paper, investigation of heat and mass transfer in a porous cavity is carried out. The governing partial differential equations are non-dimensionalised and solved using finite element method. The left vertical surface of the cavity is maintained at constant temperature and concentration which are higher than the ambient temperature and concentration applied at right vertical surface. The top and bottom walls of the cavity are adiabatic. Heat transfer is assumed to take place by natural convection and radiation. The investigation is carried out for assisting flow when buoyancy and gravity force act in same direction.
International Nuclear Information System (INIS)
Peyghambarzadeh, S.M.; Sarafraz, M.M.; Vaeli, N.; Ameri, E.; Vatani, A.; Jamialahmadi, M.
2013-01-01
Highlights: ► The cooling performance of water and n-heptane is compared during subcooled flow boiling. ► Although n-heptane leaves the heat exchanger warmer it has a lower heat transfer coefficient. ► Flow rate, heat flux and degree of subcooling have direct effect on heat transfer coefficient. ► The predictions of some correlations are evaluated against experimental data. - Abstract: In this research, subcooled flow boiling heat transfer coefficients of pure n-heptane and distilled water at different operating conditions have been experimentally measured and compared. The heat exchanger consisted of vertical annulus which is heated from the inner cylindrical heater with variable heat flux (less than 140 kW/m 2 ). Heat flux is varied so that two different flow regimes from single phase forced convection to nucleate boiling condition are created. Meanwhile, liquid flow rate is changed in the range of 2.5 × 10 −5 –5.8 × 10 −5 m 3 /s to create laminar up to transition flow regimes. Three subcooling levels including 10, 20 and 30 °C are also considered. Experimental results demonstrated that subcooled flow boiling heat transfer coefficient increases when higher heat flux, higher liquid flow rate and greater subcooling level are applied. Furthermore, influence of the operating conditions on the bubbles generation on the heat transfer surface is also discussed. It is also shown that water is better cooling fluid in comparison with n-heptane
Energy Technology Data Exchange (ETDEWEB)
Park, Chang-Seok; Lim, Hee-Chang [Pusan Nat’l Univ., Busan (Korea, Republic of)
2017-01-15
Thermal Marangoni flow has been observed inside droplets on heated surfaces, finally resulting in a coffee stain effect. This study aims to visualize and control the thermal Marangoni flow by employing periodic vertical vibration. The variations in the contact angle and internal volume of the droplet as it evaporates is observed by using a combination of continuous light and a still camera. With regard to the internal velocity, the particle image velocimetry system is applied to visualize the internal thermal Marangoni flow. In order to estimate the internal temperature gradient and surface tension on the surface of a droplet, the theoretical model based on the conduction and convection theory of heat transfer is applied. Thus, the internal velocity increases with an increase in plate temperature. The flow directions of the Marangoni and gravitational flows are opposite, and hence, it may be possible to control the coffee stain effect.
Two-phase flow and heat transfer under low gravity
Frost, W.
1981-01-01
Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.
Heat stress redistributes blood flow in arteries of the brain during dynamic exercise.
Sato, Kohei; Oue, Anna; Yoneya, Marina; Sadamoto, Tomoko; Ogoh, Shigehiko
2016-04-01
We hypothesized that heat stress would decrease anterior and posterior cerebral blood flow (CBF) during exercise, and the reduction in anterior CBF would be partly associated with large increase in extracranial blood flow (BF). Nine subjects performed 40 min of semirecumbent cycling at 60% of the peak oxygen uptake in hot (35°C; Heat) and thermoneutral environments (25°C; Control). We evaluated BF and conductance (COND) in the external carotid artery (ECA), internal carotid artery (ICA), and vertebral artery (VA) using ultrasonography. During the Heat condition, ICA and VA BF were significantly increased 10 min after the start of exercise (P Heat. Compared with the Control, either BF or COND of ICA and VA at the end of Heat tended to be lower, but not significantly. In contrast, ECA BF and COND at the end of Heat were both higher than levels in the Control condition (P Heat, a reduction in ICA BF appears to be associated with a decline in end-tidal CO2 tension (r = 0.84), whereas VA BF appears to be affected by a change in cardiac output (r = 0.87). In addition, a change in ECA BF during Heat was negatively correlated with a change in ICA BF (r = -0.75). Heat stress resulted in modification of the vascular response of head and brain arteries to exercise, which resulted in an alteration in the distribution of cardiac output. Moreover, a hyperthermia-induced increase in extracranial BF might compromise anterior CBF during exercise with heat stress. Copyright © 2016 the American Physiological Society.
Blood flow in curved pipe with radiative heat transfer
International Nuclear Information System (INIS)
Ogulu, A.; Bestman, A.R.
1992-03-01
Blood flow in a curved pipe such as the aorta is modelled in this study. The aorta is modelled as a curved pipe of slowly varying cross-section. Asymptotic series expansions about a small parameter δ, which is a measure of the curvature ratio is employed to obtain the velocity and temperature distributions. The study simulates the effect of radio-frequency heating, for instance during physiotherapy, on the flow of blood in the cardiovascular system assuming an external constant pressure gradient; and our results agree very well with results obtained by Pedley. (author). 9 refs, 2 figs
Numerical simulation of two phase flows in heat exchangers
International Nuclear Information System (INIS)
Grandotto Biettoli, M.
2006-04-01
The author gives an overview of his research activity since 1981. He first gives a detailed presentation of properties and equations of two-phase flows in heat exchangers, and of their mathematical and numerical investigation: semi-local equations (mass conservation, momentum conservation and energy conservation), homogenized conservation equations (mass, momentum and enthalpy conservation, boundary conditions), equation closures, discretization, resolution algorithm, computational aspects and applications. Then, he reports the works performed in the field of turbulent flows, hyperbolic methods, low Mach methods, the Neptune project, and parallel computing
Critical heat flux of forced flow boiling in a narrow one-side heated rectangular flow channel
Energy Technology Data Exchange (ETDEWEB)
Limin, Zheng [Shanghai Nuclear Engineering Research and Design Inst., SH (China); Iguchi, Tadashi; Kureta, Masatoshi; Akimoto, Hajime
1997-08-01
The present work deals with the critical heat flux (CHF) under subcooled flow boiling in a narrow one-side uniformly heated rectangular flow channel. The range of interest of parameters such as pressure, flow velocity and subcooling is around 0.1 MPa, 5-15 ms{sup -1} and 50degC, respectively. The rectangular flow channel used is 50 mm long, 12 mm in width and 0.2 to 3 mm in height. Test conditions were selected by combination of the following parameters: Gap=0.2-3.0 mm (D{sub hy}=0.3934-4.8 mm); flow length, 50.0 mm; water mass flux, 4.94-14.82 Mgm{sup -2}s{sup -1} (water flow velocity, 5-15 ms{sup -1}); exit pressure, 0.1 MPa; inlet temperature, 50degC, inlet coolant subcooling, 50degC. Over 40 CHF stable data points were obtained. CHF increased with the gap and flow velocity in a non-linear fashion. HTC increased with flow velocity and decreasing gap. Based on the experimental results, an empirical correlation was developed, indicating the dependence of CHF on the gap and flow velocity. All of data points predicted within {+-}18% error band for the present experimental data. On the other hand, another similitude-based correlation was also developed, indicating the dependence of Boiling number (Bo) on Reynolds number (Re) and the variable of Gap/La, where La is a characteristic length known as Laplace capillary constant. For the limited present experimental data, all of data points were predicted within {+-}16%. (author)
Critical heat flux of forced flow boiling in a narrow one-side heated rectangular flow channel
International Nuclear Information System (INIS)
Zheng Limin; Iguchi, Tadashi; Kureta, Masatoshi; Akimoto, Hajime.
1997-08-01
The present work deals with the critical heat flux (CHF) under subcooled flow boiling in a narrow one-side uniformly heated rectangular flow channel. The range of interest of parameters such as pressure, flow velocity and subcooling is around 0.1 MPa, 5-15 ms -1 and 50degC, respectively. The rectangular flow channel used is 50 mm long, 12 mm in width and 0.2 to 3 mm in height. Test conditions were selected by combination of the following parameters: Gap=0.2-3.0 mm (D hy =0.3934-4.8 mm); flow length, 50.0 mm; water mass flux, 4.94-14.82 Mgm -2 s -1 (water flow velocity, 5-15 ms -1 ); exit pressure, 0.1 MPa; inlet temperature, 50degC, inlet coolant subcooling, 50degC. Over 40 CHF stable data points were obtained. CHF increased with the gap and flow velocity in a non-linear fashion. HTC increased with flow velocity and decreasing gap. Based on the experimental results, an empirical correlation was developed, indicating the dependence of CHF on the gap and flow velocity. All of data points predicted within ±18% error band for the present experimental data. On the other hand, another similitude-based correlation was also developed, indicating the dependence of Boiling number (Bo) on Reynolds number (Re) and the variable of Gap/La, where La is a characteristic length known as Laplace capillary constant. For the limited present experimental data, all of data points were predicted within ±16%. (author)
FLECHT-SEASET 21-rod bundle flow blockage heat transfer during reflood
International Nuclear Information System (INIS)
Loftus, M.; Hochreiter, L.; Lee, N.
1983-01-01
The effect of various flow blockage shapes and distributions during a PWR reflood was investigated using six 21-rod bundles with full length, internally heated, cosine power-shaped electrical rods. The flow blockage shapes, simulating the fuel rod clad ballooning, were made of thin-wall stainless steel tubes hydroformed into a short, concentric shape and along, nonconcentric shape. The blockage sleeves were distributed both coplanar, with all sleeves located at the same elevation, and non-coplanar. The initial and boundary conditions were varied to include parametric effects of pressure, inlet water temperature, and primarily, flooding rate. The initial mid-plane rod temperature was 871 0 C (1600 0 F) in all tests. Rod and vapor temperature measurements were made throughout the rod bundle with emphasis on the blockage region. The rod heat transfer downstream of the blockage was found to be greater for rods in a blocked bundle than for similar rods in an unblocked bundle. The heat transfer improvement decreases both with time after flood initiation and as the distance increased downstream of the blockage. The improvement in the heat transfer is attributed primarily to the breakup of the water droplets entrained in the steam flow. The smaller droplets subsequently evaporate and desuperheat the steam, which then improves the heat transfer between the rods and the steam in and downstream of the blockage zone
2018-01-01
Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous "must read" chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a "must have" reference together with Sets I and II for thermal engineering researchers and practitioners.
International Nuclear Information System (INIS)
Li, Si-Ning; Zhang, Hong-Na; Li, Xiao-Bin; Li, Qian; Li, Feng-Chen; Qian, Shizhi; Joo, Sang Woo
2017-01-01
Highlights: • Heat transfer performance of non-Newtonian fluid flow in a MHS is studied. • Pseudo-plastic fluid flow can clearly promote the heat transfer efficiency in MMC. • Heat transfer enhancement is attributed to the emergence of secondary flow. • The heat transfer uniformity can also be improved by pseudo-plastic fluid flow. - Abstract: As the miniaturization and integration become the leading trend of the micro-electro-mechanical systems, it is of great significance to improve the microscaled heat transfer performance. This paper presents a three-dimensional (3D) numerical simulation on the flow characteristics and heat transfer performance of non-Newtonian fluid flow in a manifold microchannel (MMC) heat sink and traditional microchannel (TMC) heat sink. The non-Newtonian fluid was described by the power-law model. The analyses concentrated on the non-Newtonian fluid effect on the heat transfer performance, including the heat transfer efficiency and uniformity of temperature distribution, as well as the influence of inlet/outlet configurations on fluid flow and heat transfer. Comparing with Newtonian fluid flow, pseudo-plastic fluid could reduce the drag resistance in both MMC and TMC, while the dilatant fluid brought in quite larger drag resistance. For the heat transfer performance, the introduction of pseudo-plastic fluid flow greatly improved the heat transfer efficiency owing to the generation of secondary flow due to the shear-thinning property. Besides, the temperature distribution in MMC was more uniform by using pseudo-plastic fluid. Moreover, the inlet/outlet configuration was also important for the design and arrangement of microchannel heat sinks, since the present work showed that the maximum temperature was prone to locating in the corners near the inlet and outlet. This work provides guidance for optimal design of small-scale heat transfer devices in many cooling applications, such as biomedical chips, electronic systems, and
Are international fund flows pro- or counter-cyclical?
Li, Suxiao; de Haan, Jakob; Scholtens, Bert; Yang, Haizhen
2015-01-01
We investigate whether international fund flows are pro-or counter-cyclical by employing a concordance index. International fund flows are investments in bond and equity markets by institutional investors, such as mutual funds, exchange traded funds, closed-end funds and hedge funds. We find that
Fluid flow with heat transfer in a fix-bed
International Nuclear Information System (INIS)
Gasparetto, C.A.
1982-01-01
Tests with two different fluids, water and air, flowing in a bed with irregular particles of silica were done. The bed was confined inside a tube, which was heated by an external jacket. The bed is characterized by permeability and porosity. The tests showed a wall effect face to the relation between the tube diameter and the medium dimension of the particles. The results are presented as a relation between Nusselt number / Peclet number. (E.G.) [pt
Heat Flow In Cylindrical Bodies During Laser Surface Transformation Hardening
Sandven, Ole A.
1980-01-01
A mathematical model for the transient heat flow in cylindrical specimens is presented. The model predicts the temperature distribution in the vicinity of a moving ring-shaped laser spot around the periphery of the outer surface of a cylinder, or the inner surface of a hollow cylinder. It can be used to predict the depth of case in laser surface transformation hardening. The validity of the model is tested against experimental results obtained on SAE 4140 steel.
Nonstationary heat flow in the piston of the turbocharged engine
Directory of Open Access Journals (Sweden)
Piotr GUSTOF
2010-01-01
Full Text Available In this study the numeric computations of nonstationary heat flow in form of temperature distribution on characteristic surfaces of the piston of the turbocharged engine at the beginning phase its work was presented. The computations were performed for fragmentary load engine by means of the two-zone combustion model, the boundary conditions of III kind and the finite elements method (FEM by using of COSMOS/M program.
Heat and Groundwater Flow in the San Gabriel Mountains, California
Newman, A. A.; Becker, M.; Laton, W. R., Jr.
2017-12-01
Groundwater flow paths in mountainous terrain often vary widely in both time and space. Such systems remain difficult to characterize due to fracture-dominated flow paths, high topographic relief, and sparse hydrologic data. We develop a hydrogeologic conceptual model of the Western San Gabriel Mountains in Southern California based on geophysical, thermal, and hydraulic head data. Boreholes are located along the San Gabriel Fault Zone (SGFZ) and cover a wide range of elevations to capture the heterogeneity of the hydrogeologic system. Long term (2016-2017) monitoring of temperature and hydraulic head was carried out in four shallow (300-600m depth) boreholes within the study area using fiber-optic distributed temperature sensing (DTS). Borehole temperature profiles were used to assess the regional groundwater flow system and local flows in fractures intersecting the borehole. DTS temperature profiles were compared with available borehole geophysical logs and head measurements collected with grouted vibrating wire pressure transducers (VWPT). Spatial and temporal variations in borehole temperature profiles suggest that advective heat transfer due to fluid flow affected the subsurface thermal regime. Thermal evidence of groundwater recharge and/or discharge and flow through discrete fractures was found in all four boreholes. Analysis of temporal changes to the flow system in response to seasonal and drilling-induced hydraulic forcing was useful in reducing ambiguities in noisy datasets and estimating interborehole relationships. Acoustic televiewer logs indicate fractures were primarily concentrated in densely fractured intervals, and only a minor decrease of fracture density was observed with depth. Anomalously high hydraulic gradients across the SGFZ suggest that the feature is a potential barrier to lateral flow. However, transient thermal anomalies consistent with groundwater flow within the SGFZ indicate this feature may be a potential conduit to vertical flow
Density based topology optimization of turbulent flow heat transfer systems
DEFF Research Database (Denmark)
Dilgen, Sümer Bartug; Dilgen, Cetin Batur; Fuhrman, David R.
2018-01-01
The focus of this article is on topology optimization of heat sinks with turbulent forced convection. The goal is to demonstrate the extendibility, and the scalability of a previously developed fluid solver to coupled multi-physics and large 3D problems. The gradients of the objective and the con...... in the optimization process, while also demonstrating extension of the methodology to include coupling of heat transfer with turbulent flows.......The focus of this article is on topology optimization of heat sinks with turbulent forced convection. The goal is to demonstrate the extendibility, and the scalability of a previously developed fluid solver to coupled multi-physics and large 3D problems. The gradients of the objective...
SIMSOL, Multiphase Fluid and Heat Flow in Porous Media
International Nuclear Information System (INIS)
Doughty, C.
2001-01-01
1 - Description of program or function: SIMSOL calculates transient fluid and heat flow for a uniform geologic medium containing water (in both liquid and vapor phases) and air, surrounding a constant- strength linear heat source. 2 - Method of solution: SIMSOL simplifies the partial differential governing equations involving time and a radial spatial coordinate to ordinary differential equations via a similarity transformation. The resulting coupled ordinary differential equations form a two- point boundary problem which is numerically integrated using an iterative Newton-Raphson scheme. 3 - Restrictions on the complexity of the problem: SIMSOL is limited to problems with highly idealized geometry: radial symmetry, uniform material properties and initial conditions, infinite radial extent, constant-strength heat source
Prediction of critical heat flux in vertical pipe flow
International Nuclear Information System (INIS)
Levy, S.; Healzer, J.M.; Abdollahian, D.
1981-01-01
A previously developed semi-empirical model for adiabatic two-phase annular flow ix extended to predict the critical heat flux (CHF) in a vertical pipe. The model exhibits a sharply declining curve of CHF versus steam quality (X) at low X, and is relatively independent of the heat flux distribution. In this region, vaporization of the liquid film controls. At high X, net deposition upon the liquid film becomes important and CHF versus X flattens considerably. In this zone, CHF is dependent upon the heat flux distribution. Model predictions are compared to test data and an empirical correlation. The agreement is generally good if one employs previously reported mass transfer coefficients. (orig.)
Restoration of the Apollo Heat Flow Experiments Metadata
Nagihara, S.; Stephens, M. K.; Taylor, P. T.; Williams, D. R.; Hills, H. K.; Nakamura, Y.
2015-01-01
Geothermal heat flow probes were deployed on the Apollo 15 and 17 missions as part of the Apollo Lunar Surface Experiments Package (ALSEP). At each landing site, the astronauts drilled 2 holes, 10-m apart, and installed a probe in each. The holes were 1- and 1.5-m deep at the Apollo 15 site and 2.5-m deep at the Apollo 17 sites. The probes monitored surface temperature and subsurface temperatures at different depths. At the Apollo 15 site, the monitoring continued from July 1971 to January 1977. At the Apollo 17 site, it did from December 1972 to September 1977. Based on the observations made through December 1974, Marcus Langseth, the principal investigator of the heat flow experiments (HFE), determined the thermal conductivity of the lunar regolith by mathematically modeling how the seasonal temperature fluctuation propagated down through the regolith. He also determined the temperature unaffected by diurnal and seasonal thermal waves of the regolith at different depths, which yielded the geothermal gradient. By multiplying the thermal gradient and the thermal conductivity, Langseth obtained the endogenic heat flow of the Moon as 21 mW/m(exp 2) at Site 15 and 16 mW/m(exp 2) at Site 17.
An analytical wall-function for turbulent flows and heat transfer over rough walls
International Nuclear Information System (INIS)
Suga, K.; Craft, T.J.; Iacovides, H.
2006-01-01
This paper reports the development of a refined wall-function strategy for the modelling of turbulent forced convection heat transfer over smooth and rough surfaces. In order to include the effects of fine-grain surface roughness, the present study extends a more fundamental work by Craft et al. [Craft, T.J., Gerasimov, A.V., Iacovides, H., Launder, B.E., 2002. Progress in the generalisation of wall-function treatment. Int. J. Heat Fluid Flow 23, 148-160] on the development of advanced wall-functions of general applicability. The presently proposed model is validated through comparisons with data available for internal flows through channels and for external flows over flat and curved plates with both smooth and rough surfaces. Then, its further validation in separating flows over a sand dune and a sand-roughened ramp is discussed. The validation results suggest that the presently proposed form can be successfully applied to a wide range of attached and separated turbulent flows with heat transfer over smooth and fine-grain rough surfaces
Internal flow measurement in transonic compressor by PIV technique
Wang, Tongqing; Wu, Huaiyu; Liu, Yin
2001-11-01
The paper presents some research works conducted in National Key Laboratory of Aircraft Engine of China on the shock containing supersonic flow measurement as well as the internal flow measurement of transoijc compressor by PIC technique. A kind of oil particles in diameter about 0.3 micrometers containing in the flow was discovered to be a very good seed for the PIV measurement of supersonic jet flow. The PIV measurement in over-expanded supersonic free jet and in the flow over wages show a very clear shock wave structure. In the PIV internal flow measurement of transonic compressor a kind of liquid particle of glycol was successful to be used as the seed. An illumination periscope with sheet forming optics was designed and manufactured, it leaded the laser shot generated from an integrate dual- cavity Nd:YAG laser of TSI PIV results of internal flow of an advanced low aspect ratio transonic compressor were shown and discussed briefly.
Heat and mass transfer from the mantle: heat flow and He-isotope constraints
Directory of Open Access Journals (Sweden)
B. G. Polyak
2005-06-01
Full Text Available Terrestrial heat flow density, q, is inversely correlated with the age, t, of tectono-magmatic activity in the Earth's crust (Polyak and Smirnov, 1966; etc.. «Heat flow-age dependence» indicates unknown temporal heat sources in the interior considered a priori as the mantle-derived diapirs. The validity of this hypothesis is demonstrated by studying the helium isotope ratio, 3He/4He = R, in subsurface fluids. This study discovered the positive correlation between the regionally averaged (background estimations of R- and q-values (Polyak et al., 1979a. Such a correlation manifests itself in both pan-regional scales (Norhtern Eurasia and separate regions, e.g., Japan (Sano et al., 1982, Eger Graben (Polyak et al., 1985 Eastern China rifts (Du, 1992, Southern Italy (Italiano et al., 2000, and elsewhere. The R-q relation indicates a coupled heat and mass transfer from the mantle into the crust. From considerations of heat-mass budget this transfer can be provided by the flux consisting of silicate matter rather than He or other volatiles. This conclusion is confirmed by the correlation between 3He/ 4He and 87Sr/86Sr ratios in the products of the volcanic and hydrothermal activity in Italy (Polyak et al., 1979b; Parello et al., 2000 and other places. Migration of any substance through geotemperature field transports thermal energy accumulated within this substance, i.e. represents heat and mass transfer. Therefore, only the coupled analysis of both material and energy aspects of this transfer makes it possible to characterise the process adequately and to decipher an origin of terrestrial heat flow observed in upper parts of the earth crust. An attempt of such kind is made in this paper.
6th International Workshop on Model Reduction in Reactive Flow
2018-01-01
reduction in reacting flow . Registration DateRegistration TypeFirst Name Middle NameLast Name Affiliation US State /Canadian ProvinceState/Province/R gion...Report: 6th International Workshop on Model Reduction in Reactive Flow The views, opinions and/or findings contained in this report are those of the...Agreement Number: W911NF-17-1-0121 Organization: Princeton University Title: 6th International Workshop on Model Reduction in Reactive Flow Report Term
International Energy Agency Solar Heating and Cooling Program
Brooks, A. J.
This trip was undertaken to participate in and represent the United States Industry at the International Energy Agency (IEA) Solar Heating and Cooling Program (SHCP) Task 14 Workshop. The meeting took place at the A1 Bani Hotel in Rome Italy.
Development of low flow critical heat flux correlation for HANARO
International Nuclear Information System (INIS)
Park, Cheol; Chae, Hee Taek; Hang, Gee Yang.
1997-07-01
A low flow CHF correlation was developed for the safe operation of HANARO during the natural circulation cooling and the assessment of safety during the low flow condition of accident. The analytical model was applied to estimate the heat flux and the temperature distributions along the periphery of the fin at CHF conditions, and the predicted wall temperature at the sheath between the fins by the model agreed well with the measured one. The parametric trends of the CHF data for the finned geometry agreed with the general understanding from the previous studies for the unfinned annulus or tube geometries. It is revealed that the fin does not affect the CHF for low flow condition, although it increase the critical power due to larger heat transfer area. As the existing CHF correlation is proposed to predict the CHF for both finned and unfinned geometries at low flow and low pressure conditions. The developed correlation predicts the experimental CHF data with RMS errors of 13.7 %. (author). 19 refs., 3 tabs., 23 figs
Development of low flow critical heat flux correlation for HANARO
Energy Technology Data Exchange (ETDEWEB)
Park, Cheol; Chae, Hee Taek; Hang, Gee Yang
1997-07-01
A low flow CHF correlation was developed for the safe operation of HANARO during the natural circulation cooling and the assessment of safety during the low flow condition of accident. The analytical model was applied to estimate the heat flux and the temperature distributions along the periphery of the fin at CHF conditions, and the predicted wall temperature at the sheath between the fins by the model agreed well with the measured one. The parametric trends of the CHF data for the finned geometry agreed with the general understanding from the previous studies for the unfinned annulus or tube geometries. It is revealed that the fin does not affect the CHF for low flow condition, although it increase the critical power due to larger heat transfer area. As the existing CHF correlation is proposed to predict the CHF for both finned and unfinned geometries at low flow and low pressure conditions. The developed correlation predicts the experimental CHF data with RMS errors of 13.7 %. (author). 19 refs., 3 tabs., 23 figs.
Modelling of flow and heat transfer in PV cooling channels
Energy Technology Data Exchange (ETDEWEB)
Diarra, D.C.; Harrison, S.J. [Queen' s Univ., Kingston, ON (Canada). Dept. of Mechanical and Materials Engineering Solar Calorimetry Lab; Akuffo, F.O. [Kwame Nkrumah Univ. of Science and Technology, Kumasi (Ghana). Dept. of Mechanical Engineering
2005-07-01
Under sunny conditions, the temperature of photovoltaic (PV) modules can be 20 to 30 degrees C above the ambient air temperature. This affects the performance of PV modules, particularly in regions with hot climates. For silicon solar cells, the maximum power decreases between 0.4 and 0.5 per cent for every degree C of temperature increase above a reference value. In an effort to address this issue, this experimental and numerical study examined an active PV panel evaporative cooling scheme that is typically used in hot arid climates. The cooling system circulated cool air behind the PV modules, extracting heat and lowering solar cell temperature. A fluid dynamic and thermal model of the combined system was developed using the EES program in order to study the configuration of the cooling channel and the characteristics of the cooling flow. Heat transfer and flow characteristics in the cooling channel were then calculated along with pressure drop and fan power associated with the air-circulation. The net power output was also calculated. The objective was to design a cost efficient cooling system and to optimize its flow and pressure drop in order to maximize power output. The study demonstrated how the performance of the PV panel is influenced by the geometry of the cooling channel, the inlet air temperature and the air flow rate. 2 refs.
Falling film flow, heat transfer and breakdown on horizontal tubes
International Nuclear Information System (INIS)
Rogers, J.T.
1980-11-01
Knowledge of falling film flow and heat transfer characteristics on horizontal tubes is required in the assessment of certain CANDU reactor accident sequences for those CANDU reactors which use moderator dump as one of the shut-down mechanisms. In these reactors, subsequent cooling of the calandria tubes is provided by falling films produced by sprays. This report describes studies of falling film flow and heat transfer characteristics on horizontal tubes. Analyses using integral methods are given for laminar and turbulent flow, ignoring and accounting for momentum effects in the film. Preliminary experiments on film flow stability on horizontal tubes are described and various mechanisms of film breakdown are examined. The work described in this report shows that in LOCA with indefinitely delayed ECI in the NPD or Douglas Point (at 70 percent power) reactors, the falling films on the calandria tubes will not be disrupted by any of the mechanisms considered, provided that the pressure tubes do not sag onto the calandria tubes. However, should the pressure tubes sag onto the calandria tubes, film disruption will probably occur
Natural convection heat transfer between vertical channel with flow resistance at the lower end
International Nuclear Information System (INIS)
Iwamoto, S.; Nishimura, S.; Ishihara, I.
2003-01-01
For natural convection in the geometrically complicated channel, the convection flow is suppressed by flow resistance due to such channel itself and the lopsided flow may take place. This could result in serious influences on the heat transfer in the channel. In order to investigate fundamentally the natural convection flow and heat transfer in such the channel, the vertical channel in which wall was heated with uniform heat flux and the flow resistance was given by small clearance between the lower end of channel and a wide horizontal floor. Flow pattern was observed by illuminating smoke filled in the channel and heat transfer rate was measured. (author)
Interfacial heat transfer in countercurrent flows of steam and water
International Nuclear Information System (INIS)
Megahed, M.M.
1987-04-01
A study was conducted to examine the departure from equilibrium conditions with respect to direct contact condensation. A simple analytical model, which used an equilibrium factor, K, was derived. The model was structured to represent the physical dimensions of a nuclear reactor downcomer annulus, water subcooling, wall temperature, and water flow rate. In a two step process the model was first used to isolate the average interfacial heat transfer coefficient from vertical countercurrent steam/water data of Cook et al., with the aid of a Stanton number correlation. In the second step the model was assessed by regeneration of measured steam flow rates in the experiments by Cook et al., and an additional experiment of Kim. This report documents the analytical model, the derived Stanton number correlation, and the comparison of the calculated and measured steam flow rates by which the accuracy of the model was assessed
Two-phase flow regimes and mechanisms of critical heat flux under subcooled flow boiling conditions
International Nuclear Information System (INIS)
Le Corre, Jean-Marie; Yao, Shi-Chune; Amon, Cristina H.
2010-01-01
A literature review of critical heat flux (CHF) experimental visualizations under subcooled flow boiling conditions was performed and systematically analyzed. Three major types of CHF flow regimes were identified (bubbly, vapor clot and slug flow regime) and a CHF flow regime map was developed, based on a dimensional analysis of the phenomena and available experimental information. It was found that for similar geometric characteristics and pressure, a Weber number (We)/thermodynamic quality (x) map can be used to predict the CHF flow regime. Based on the experimental observations and the review of the available CHF mechanistic models under subcooled flow boiling conditions, hypothetical CHF mechanisms were selected for each CHF flow regime, all based on a concept of wall dry spot overheating, rewetting prevention and subsequent dry spot spreading. Even though the selected concept has not received much attention (in term or theoretical developments and applications) as compared to other more popular DNB models, its basis have often been cited by experimental investigators and is considered by the authors as the 'most-likely' mechanism based on the literature review and analysis performed in this work. The selected modeling concept has the potential to span the CHF conditions from highly subcooled bubbly flow to early stage of annular flow and has been numerically implemented and validated in bubbly flow and coupled with one- and three-dimensional (CFD) two-phase flow codes, in a companion paper. [Le Corre, J.M., Yao, S.C., Amon, C.H., in this issue. A mechanistic model of critical heat flux under subcooled flow boiling conditions for application to one and three-dimensional computer codes. Nucl. Eng. Des.].
Directory of Open Access Journals (Sweden)
Sabanskis A.
2016-04-01
Full Text Available Monitoring of temperature, humidity and air flow velocity is performed in 5 experimental buildings with the inner size of 3×3×3 m3 located in Riga, Latvia. The buildings are equipped with different heating systems, such as an air-air heat pump, air-water heat pump, capillary heating mat on the ceiling and electric heater. Numerical simulation of air flow and heat transfer by convection, conduction and radiation is carried out using OpenFOAM software and compared with experimental data. Results are analysed regarding the temperature and air flow distribution as well as thermal comfort.
Flow and heat transfer behaviour of nanofluids in microchannels
Directory of Open Access Journals (Sweden)
James Bowers
2018-04-01
Full Text Available Flow and heat transfer of aqueous based silica and alumina nanofluids in microchannels were experimentally investigated. The measured friction factors were higher than conventional model predictions at low Reynolds numbers particularly with high nanoparticle concentrations. A decrease in the friction factor was observed with increasing Reynolds number, possibly due to the augmentation of nanoparticle aggregate shape arising from fluid shear and alteration of local nanoparticle concentration and nanofluid viscosity. Augmentation of the silica nanoparticle morphology by fluid shear may also have affected the friction factor due to possible formation of a core/shell structure of the particles. Measured thermal conductivities of the silica nanofluids were in approximate agreement with the Maxwell-Crosser model, whereas the alumina nanofluids only showed slight enhancements. Enhanced convective heat transfer was observed for both nanofluids, relative to their base fluids (water, at low particle concentrations. Heat transfer enhancement increased with increasing Reynolds number and microchannel hydraulic diameter. However, the majority of experiments showed a larger increase in pumping power requirements relative to heat transfer enhancements, which may hinder the industrial uptake of the nanofluids, particularly in confined environments, such as Micro Electro-Mechanical Systems (MEMS. Keywords: Nanofluid, Microchannel, Heat transfer, Pressure drop, Friction factor, Thermal conductivity, Viscosity
Heat transfer and flow in solar energy and bioenergy systems
Xu, Ben
The demand for clean and environmentally benign energy resources has been a great concern in the last two decades. To alleviate the associated environmental problems, reduction of the use of fossil fuels by developing more cost-effective renewable energy technologies becomes more and more significant. Among various types of renewable energy sources, solar energy and bioenergy take a great proportion. This dissertation focuses on the heat transfer and flow in solar energy and bioenergy systems, specifically for Thermal Energy Storage (TES) systems in Concentrated Solar Power (CSP) plants and open-channel algal culture raceways for biofuel production. The first part of this dissertation is the discussion about mathematical modeling, numerical simulation and experimental investigation of solar TES system. First of all, in order to accurately and efficiently simulate the conjugate heat transfer between Heat Transfer Fluid (HTF) and filler material in four different solid-fluid TES configurations, formulas of an e?ective heat transfer coe?cient were theoretically developed and presented by extending the validity of Lumped Capacitance Method (LCM) to large Biot number, as well as verifications/validations to this simplified model. Secondly, to provide design guidelines for TES system in CSP plant using Phase Change Materials (PCM), a general storage tank volume sizing strategy and an energy storage startup strategy were proposed using the enthalpy-based 1D transient model. Then experimental investigations were conducted to explore a novel thermal storage material. The thermal storage performances were also compared between this novel storage material and concrete at a temperature range from 400 °C to 500 °C. It is recommended to apply this novel thermal storage material to replace concrete at high operating temperatures in sensible heat TES systems. The second part of this dissertation mainly focuses on the numerical and experimental study of an open-channel algae
Energy Technology Data Exchange (ETDEWEB)
Li, Zhigang [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Huai, Xiulan; Tao, Yujia; Chen, Huanzhuo [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China)
2007-12-15
Three-dimensional conjugate numerical simulations using the inlet, average and variable thermal properties respectively were performed for the laminar water flow and heat transfer in rectangular microchannels with D{sub h} of 0.333 mm at Re of 101-1775. Both average and variable properties are adopted in data reduction. The calculated local and average characteristics of flow and heat transfer are compared among different methods, and with the experiments, correlations and simplified theoretical solution data from published literatures. Compared with the inlet property method, both average and variable property methods have significantly lower f{sub app}, but higher convective heat transfer coefficient h{sub z} and Nu{sub z}. Compared with the average property method, the variable property method has higher f{sub app}Re{sub ave} and lower h{sub z} at the beginning, but lower f{sub app}Re{sub ave} and higher h{sub z} at the later section of the channel. The calculated Nu{sub ave} agree well with the Sieder-Tate correlation and the recently reported experiment, validating the traditional macroscale theory in predicting the flow and heat transfer characteristics in the dimension and Re range of the present work. (author)
International Nuclear Information System (INIS)
Dzarasov, Yu.I.
1976-01-01
Results of studies for a vapour-water dispersive-ring flow in the heated tore channel are presented. The work area has been a vertical tore channel with external and internal cross-section diameters equal to 12 and 6 mm, respectively, and with the internal heated wall of 1000 mm and 2500 mm long, respectively. The medium moves upward with the pressure 35 and 70 bar. Local heat emission factors α as a function of the channel height have been determined with measuring wall-flow temperature difference at the outlet cross-section. It has been noted that in addition to dependence of the α factor from heat emission q, the factor is also greatly affected by the mass speed and steam content X with the growth of which α increases. The model of the flow explaining the effect of X upon α has been proposed. It has been found that convective heat emission under boiling of the vapour-water mixture in the channels is determined not only by the flow rate but by the amount of liquid in the flow and particular, by the amount of liquid setting at the heating surface
Modeling of a District Heating System and Optimal Heat-Power Flow
Directory of Open Access Journals (Sweden)
Wentao Yang
2018-04-01
Full Text Available With ever-growing interconnections of various kinds of energy sources, the coupling between a power distribution system (PDS and a district heating system (DHS has been progressively intensified. Thus, it is becoming more and more important to take the PDS and the DHS as a whole in energy flow analysis. Given this background, a steady state model of DHS is first presented with hydraulic and thermal sub-models included. Structurally, the presented DHS model is composed of three major parts, i.e., the straight pipe, four kinds of local pipes, and the radiator. The impacts of pipeline parameters and the environment temperature on heat losses and pressure losses are then examined. The term “heat-power flow” is next defined, and the optimal heat-power flow (OHPF model formulated as a quadratic planning problem, in which the objective is to minimize energy losses, including the heat losses and active power losses, and both the operational constraints of PDS and DHS are respected. The developed OHPF model is solved by the well-established IPOPT (Interior Point OPTimizer commercial solver, which is based on the YALMIP/MATLAB toolbox. Finally, two sample systems are served for demonstrating the characteristics of the proposed models.
Viscous dissipation and Joule heating effects in MHD 3D flow with heat and mass fluxes
Muhammad, Taseer; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed
2018-03-01
The present research explores the three-dimensional stretched flow of viscous fluid in the presence of prescribed heat (PHF) and concentration (PCF) fluxes. Mathematical formulation is developed in the presence of chemical reaction, viscous dissipation and Joule heating effects. Fluid is electrically conducting in the presence of an applied magnetic field. Appropriate transformations yield the nonlinear ordinary differential systems. The resulting nonlinear system has been solved. Graphs are plotted to examine the impacts of physical parameters on the temperature and concentration distributions. Skin friction coefficients and local Nusselt and Sherwood numbers are computed and analyzed.
The onset of flow instability for a downward flow of a non-boiling heated liquid
International Nuclear Information System (INIS)
Babelli, Ibrahim; Ishii, Mamoru
1999-01-01
A procedure for predicting the onset of flow instability (OFI) in downward flows at low-pressure and low-flow conditions without boiling is presented in this paper. It is generally accepted that the onset of significant void in subcooled boiling precedes, and is a precondition to, the occurrence of static flow instability. A detailed analysis of the pressure drop components for a downward flow in a heated channel reveals the possibility of unstable transition from single-phase flow to high-quality two-phase flow, i.e., flow excursion. Low flow rate and high subcooling are the two important conditions for the occurrence of this type of instability. The unstable transition occurs when the resistance to the downward flow caused by local (orifice), frictional, and thermal expansion pressure drops equalizes the driving force of the gravitational pressure drop. The inclusion of the thermal expansion pressure drop is essential to account for this type of transition. Experimental data are yet to be produced to verify the prediction of the present analysis. (author)
International symposium on radiative heat transfer: Book of abstracts
International Nuclear Information System (INIS)
1995-01-01
The international symposium on radiative heat transfer was held on 14-18 August 1995 Turkey. The specialists discussed radiation transfer in materials processing and manufacturing, solution of radiative heat transfer equation, transient radiation problem and radiation-turbulence interactions, raditive properties of gases, atmospheric and stellar radiative transfer , radiative transfer and its applications, optical and radiative properties of soot particles, inverse radiation problems, partticles, fibres,thermophoresis and waves and modelling of comprehensive systems at the meeting. Almost 79 papers were presented in the meeting
Unsteady Flow in a Supersonic Turbine with Variable Specific Heats
Dorney, Daniel J.; Griffin, Lisa W.; Huber, Frank; Sondak, Douglas L.; Turner, James (Technical Monitor)
2001-01-01
Modern high-work turbines can be compact, transonic, supersonic, counter-rotating, or use a dense drive gas. The vast majority of modern rocket turbine designs fall into these Categories. These turbines usually have large temperature variations across a given stage, and are characterized by large amounts of flow unsteadiness. The flow unsteadiness can have a major impact on the turbine performance and durability. For example, the Space Transportation Main Engine (STME) fuel turbine, a high work, transonic design, was found to have an unsteady inter-row shock which reduced efficiency by 2 points and increased dynamic loading by 24 percent. The Revolutionary Reusable Technology Turbopump (RRTT), which uses full flow oxygen for its drive gas, was found to shed vortices with such energy as to raise serious blade durability concerns. In both cases, the sources of the problems were uncovered (before turbopump testing) with the application of validated, unsteady computational fluid dynamics (CFD) to the designs. In the case of the RRTT and the Alternate Turbopump Development (ATD) turbines, the unsteady CFD codes have been used not just to identify problems, but to guide designs which mitigate problems due to unsteadiness. Using unsteady flow analyses as a part of the design process has led to turbine designs with higher performance (which affects temperature and mass flow rate) and fewer dynamics problems. One of the many assumptions made during the design and analysis of supersonic turbine stages is that the values of the specific heats are constant. In some analyses the value is based on an average of the expected upstream and downstream temperatures. In stages where the temperature can vary by 300 to 500 K, however, the assumption of constant fluid properties may lead to erroneous performance and durability predictions. In this study the suitability of assuming constant specific heats has been investigated by performing three-dimensional unsteady Navier
5th International Conference on Jets, Wakes and Separated Flows
2016-01-01
This volume collects various contributions from the 5th International Conference on Jets, Wakes and Separated Flows (ICJWSF2015) that took place in Stockholm during June 2015. Researchers from all around the world presented their latest results concerning fundamental and applied aspects of fluid dynamics. With its general character, the conference embraced many aspects of fluid dynamics, such as shear flows, multiphase flows and vortex flows, for instance. The structure of the present book reflects the variety of topics treated within the conference i.e. Jets, Wakes, Separated flows, Vehicle aerodynamics, Wall-bounded and confined flows, Noise, Turbomachinery flows, Multiphase and reacting flows, Vortex dynamics, Energy-related flows and a section dedicated to Numerical analyses.
Entropy generation of nanofluid flow in a microchannel heat sink
Manay, Eyuphan; Akyürek, Eda Feyza; Sahin, Bayram
2018-06-01
Present study aims to investigate the effects of the presence of nano sized TiO2 particles in the base fluid on entropy generation rate in a microchannel heat sink. Pure water was chosen as base fluid, and TiO2 particles were suspended into the pure water in five different particle volume fractions of 0.25%, 0.5%, 1.0%, 1.5% and 2.0%. Under laminar, steady state flow and constant heat flux boundary conditions, thermal, frictional, total entropy generation rates and entropy generation number ratios of nanofluids were experimentally analyzed in microchannel flow for different channel heights of 200 μm, 300 μm, 400 μm and 500 μm. It was observed that frictional and total entropy generation rates increased as thermal entropy generation rate were decreasing with an increase in particle volume fraction. In microchannel flows, thermal entropy generation could be neglected due to its too low rate smaller than 1.10e-07 in total entropy generation. Higher channel heights caused higher thermal entropy generation rates, and increasing channel height yielded an increase from 30% to 52% in thermal entropy generation. When channel height decreased, an increase of 66%-98% in frictional entropy generation was obtained. Adding TiO2 nanoparticles into the base fluid caused thermal entropy generation to decrease about 1.8%-32.4%, frictional entropy generation to increase about 3.3%-21.6%.
Fluid flow and heat transfer modeling for castings
International Nuclear Information System (INIS)
Domanus, H.M.; Liu, Y.Y.; Sha, W.T.
1986-01-01
Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach. In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process. 14 refs., 13 figs
Experimental and Numerical Design and Optimization of a Counter-Flow Heat Exchanger
Directory of Open Access Journals (Sweden)
Bahrami Salman
2018-01-01
Full Text Available A new inexpensive counter-flow heat exchanger has been designed and optimized for a vapor-compression cooling system in this research. The main aim is to experimentally and numerically evaluate the effect of an internal heat exchanger (IHX adaptation in an automotive air conditioning system. In this new design of IHX, the high-pressure liquid passes through the central channel and the low-pressure vapor flows in several parallel channels in the opposite direction. The experimental set-up has been made up of original components of the air conditioning system of a medium sedan car, specially designed and built to analyze vehicle A/C equipment under real operating conditions. The results show that this compact IHX may achieve up to 10% of the evaporator capacity while low pressure drop will be imposed on this refrigeration cycle. Also, they confirm considerable decrease of compressor power consumption (CPC, which is intensified at higher evaporator air flow. A significant improvement of the coefficient of performance (COP is achieved with the IHX employment too. The influence of operating conditions has been also discussed in this paper. Finally, numerical analyses have been briefly presented, which bring more details of the flow behavior and heat transfer phenomena, and help to determine the optimal arrangement of channels.
Flow visualization study of inverted annular flow of post dryout heat transfer region
International Nuclear Information System (INIS)
Ishii, M.; De Jarlais, G.
1985-01-01
The inverted annular flow is important in the area of LWR accident analysis in terms of the maximum cladding temperature and effectiveness of the emergency core cooling. However, the inverted annular flow thermal-hydraulics is not well understood due to its special heat transfer condition of film boiling. In view of this, the inverted flow is studied in detail experimentally. A new experimental apparatus has been constructed in which film boiling heat transfer can be established in a transparent test section. Data on liquid core stability, core break-up mechanism, and dispersed-core liquid slug and droplet sizes are obtained using F 113 as a test fluid. Both high speed movies and flash photographs are used
Turbulence modeling and surface heat transfer in a stagnation flow region
Wang, C. R.; Yeh, F. C.
1987-01-01
Analysis for the turbulent flow field and the effect of freestream turbulence on the surface heat transfer rate of a stagnation flow is presented. The emphasis is on modeling and its augmentation of surface heat transfer rate. The flow field considered is the region near the forward stagnation point of a circular cylinder in a uniform turbulent mean flow.
Directory of Open Access Journals (Sweden)
Imad Khan
Full Text Available Current work highlights the computational aspects of MHD Carreau nanofluid flow over an inclined stretching cylinder with convective boundary conditions and Joule heating. The mathematical modeling of physical problem yields nonlinear set of partial differential equations. A suitable scaling group of variables is employed on modeled equations to convert them into non-dimensional form. The integration scheme Runge-Kutta-Fehlberg on the behalf of shooting technique is utilized to solve attained set of equations. The interesting aspects of physical problem (linear momentum, energy and nanoparticles concentration are elaborated under the different parametric conditions through graphical and tabular manners. Additionally, the quantities (local skin friction coefficient, local Nusselt number and local Sherwood number which are responsible to dig out the physical phenomena in the vicinity of stretched surface are computed and delineated by varying controlling flow parameters. Keywords: MHD, Carreau nanofluid, Inclined stretching cylinder, Joule heating, Shooting technique
Energy Technology Data Exchange (ETDEWEB)
Liu, P., E-mail: pinliu@aust.edu.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); School of Mechanical Engineering, Anhui University of Science and Technology, Huainan 232001 (China); Peng, X.B., E-mail: pengxb@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Song, Y.T. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Fang, X.D. [Institute of Air Conditioning and Refrigeration, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Huang, S.H. [University of Science and Technology of China, Hefei 230026 (China); Mao, X. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)
2016-11-15
Highlights: • The Eulerian multiphase models coupled with Non-equilibrium Boiling model can effectively simulate the subcooled water flow boiling. • ONB and FDB appear earlier and earlier with the increase of heat fluxes. • The void fraction increases gradually along the flow direction. • The inner CuCrZr tube deteriorates earlier than the outer tungsten layer and the middle OFHC copper layer. - Abstract: In order to remove high heat fluxes for plasma facing components in International Thermonuclear Experimental Reactor (ITER) divertor, a numerical simulation of subcooled water flow boiling heat transfer in a vertically upward smooth tube was conducted in this paper on the condition of one-sided high heat fluxes. The Eulerian multiphase model coupled with Non-equilibrium Boiling model was adopted in numerical simulation of the subcooled boiling two-phase flow. The heat transfer regions, thermodynamic vapor quality (x{sub th}), void fraction and temperatures of three components on the condition of the different heat fluxes were analyzed. Numerical results indicate that the onset of nucleate boiling (ONB) and fully developed boiling (FDB) appear earlier and earlier with increasing heat flux. With the increase of heat fluxes, the inner CuCrZr tube will deteriorate earlier than the outer tungsten layer and the middle oxygen-free high-conductivity (OFHC) copper layer. These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor.
Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity
Jiang, Fei
2018-04-01
We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.
Analytical methods for heat transfer and fluid flow problems
Weigand, Bernhard
2015-01-01
This book describes useful analytical methods by applying them to real-world problems rather than solving the usual over-simplified classroom problems. The book demonstrates the applicability of analytical methods even for complex problems and guides the reader to a more intuitive understanding of approaches and solutions. Although the solution of Partial Differential Equations by numerical methods is the standard practice in industries, analytical methods are still important for the critical assessment of results derived from advanced computer simulations and the improvement of the underlying numerical techniques. Literature devoted to analytical methods, however, often focuses on theoretical and mathematical aspects and is therefore useless to most engineers. Analytical Methods for Heat Transfer and Fluid Flow Problems addresses engineers and engineering students. The second edition has been updated, the chapters on non-linear problems and on axial heat conduction problems were extended. And worked out exam...
Large eddy simulations of turbulent flows with heat transfer
International Nuclear Information System (INIS)
Chatelain, Alexandre
2004-01-01
LES of turbulent flows with heat transfer was used within the framework of conjugate heat transfer problems. The objective of this work lies not only in identifying the various elements likely to impair temperature fluctuations estimations at the fluid/solid interface but also to introduce adequate wall modeling. The choice of a proper convection scheme for the transport of passive scalars led to the adoption of a high order upwind scheme with slope limiter. The use of classical wall models having shown some weaknesses as for the estimation of parietal temperature fluctuations, two new approaches are proposed and tested. The first one relies on a complete resolution of the Navier-Stokes equations on a refined grid close to the wall making it possible to rebuild the temperature fluctuations near the wall. The second one relies on the simultaneous and one dimensional resolution of a turbulent boundary layer equation and a variance transport equation near the wall. (author) [fr
Heat transfer to MHD oscillatory dusty fluid flow in a channel filled ...
Indian Academy of Sciences (India)
The flow of fluids through porous media has become ... convection-radiation interaction with heat transfer in boundary layer flow over a flat plate sub- ... Unsteady MHD free convection flow of a compressible fluid past a moving vertical plate in.
Fuel cell with internal flow control
Haltiner, Jr., Karl J.; Venkiteswaran, Arun [Karnataka, IN
2012-06-12
A fuel cell stack is provided with a plurality of fuel cell cassettes where each fuel cell cassette has a fuel cell with an anode and cathode. The fuel cell stack includes an anode supply chimney for supplying fuel to the anode of each fuel cell cassette, an anode return chimney for removing anode exhaust from the anode of each fuel cell cassette, a cathode supply chimney for supplying oxidant to the cathode of each fuel cell cassette, and a cathode return chimney for removing cathode exhaust from the cathode of each fuel cell cassette. A first fuel cell cassette includes a flow control member disposed between the anode supply chimney and the anode return chimney or between the cathode supply chimney and the cathode return chimney such that the flow control member provides a flow restriction different from at least one other fuel cell cassettes.
Energy Technology Data Exchange (ETDEWEB)
El-Sebaii, A.A. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt)]. E-mail: aasebaii@yahoo.com; Aboul-Enein, S. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt); Ramadan, M.R.I. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt); Khallaf, A.M. [Department of Physics, Faculty of Science, Tanta University, Tanta 31527 (Egypt)
2006-05-15
The thermal performance of a shallow solar pond (SSP) under an open cycle continuous flow heating mode for heat extraction has been investigated. A serpentine heat exchanger (HE), either welded to the absorber plate or immersed in the pond water, has been used for extracting the heat. Suitable computer programs have been developed based on analytical solutions of the energy balance equations for the various elements of the SSP in the presence of the HE. Numerical calculations have been performed to study the effect of different operational and configurational parameters on the pond performance. In order to improve the pond performance, optimization of the various dimensions of the pond with the HE has been performed. The effects of the design parameters of the HE's tube, i.e. length L{sub he}, diameter D and mass flow rate m-bar {sub f} of the fluid flowing through the HE, on the pond performance have been investigated. The outlet temperature of the HE's fluid T{sub fo} is found to increase with increase of the HE length L{sub he}, and it decreases with increase of the mass flow rate of the HE's fluid m-bar {sub f} up to typical values for these parameters. Typical values for L{sub he} and m-bar {sub f} are found to be 4m and 0.004kg/s beyond which the change in T{sub fo} becomes insignificant. Experiments have been performed for the pond under different operational conditions with a HE welded to the absorber plate. To validate the proposed mathematical models, comparisons between experimental and theoretical results have been performed. Good agreement has been achieved.
Energy Technology Data Exchange (ETDEWEB)
Park, Chun Dong; Lee, Dong Hyun; Park, Byung-Sik; Choi, Jaejoon [Korea Institute of Energy Research (KIER), Daejeon (Korea, Republic of)
2017-02-15
In this study, the flow and heat transfer characteristics of the finned annular passage were investigated numerically. The annular passage simulates co-axial geothermal heat exchanger, and fins are installed on its inner wall to reduce heat loss from the production passage (annulus) to injection passage (inner pipe). A commercial CFD program, Ansys Fluent, was used with SST k-ω turbulence model. The effects of the geometric parameters of the fin on the inner tube were analyzed under the periodic boundary condition. The result indicated that most parameters had a tendency to increase with an increase in the height and angle of the fin. However, it was confirmed that the Nusselt number of the inner tube on the coaxial 15, 5, 0.3 was lower than that of the smooth tube. Additionally, the Nusselt number of the inner tube exhibited a tendency of decreasing with a decrease in the spacing in Coaxial 15, S{sub f}, 0.3.
Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity
Tassone, A.; Nobili, M.; Caruso, G.
2017-11-01
The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.
Summary of flow and heat transfer in RPV under PTS
International Nuclear Information System (INIS)
Lu Donghua; Wang Haijun; Chen Tingkuan; Luo Yushan
2003-01-01
PTS under loss of coolant accident (LOCA) has great effect on the safety of RPV. Many research works focusing on flow and heat transfer in RPV under PTS have been done in developed countries for many years, and a lot of results have been got both on experiment and numerical simulation. The safety of nuclear power plant is enhanced greatly by these research works. With the developing of nuclear power technology in China, RPV integration under PTS has been studied. The author summarizes research works at home and abroad in recent years. The problems existed in present work and research direction in the future are discussed
8th International Symposium on Heating, Ventilation and Air Conditioning
Zhu, Yingxin; Li, Yuguo; Vol.1 Indoor and Outdoor Environment; Vol.2 HVAC&R Component and Energy System; Vol.3 Building Simulation and Information Management
2014-01-01
Proceedings of the 8th International Symposium on Heating, Ventilation and Air Conditioning is based on the 8th International Symposium of the same name (ISHVAC2013), which took place in Xi’an on October 19-21, 2013. The conference series was initiated at Tsinghua University in 1991 and has since become the premier international HVAC conference initiated in China, playing a significant part in the development of HVAC and indoor environmental research and industry around the world. This international conference provided an exclusive opportunity for policy-makers, designers, researchers, engineers and managers to share their experience. Considering the recent attention on building energy consumption and indoor environments, ISHVAC2013 provided a global platform for discussing recent research on and developments in different aspects of HVAC systems and components, with a focus on building energy consumption, energy efficiency and indoor environments. These categories span a broad range of topics, and the proce...
Heat up and potential failure of BWR upper internals during a severe accident
Energy Technology Data Exchange (ETDEWEB)
Robb, Kevin R [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-01-01
In boiling water reactors, the steam dome, steam separators, and dryers above the core are comprised of approximately 100 tons of stainless steel. During a severe accident in which the coolant boils away and exothermic oxidation of zirconium occurs, gases (steam and hydrogen) are superheated in the core region and pass through the upper internals. Historically, the upper internals have been modeled using severe accident codes with relatively simple approximations. The upper internals are typically modeled in MELCOR as two lumped volumes with simplified heat transfer characteristics, with no structural integrity considerations, and with limited ability to oxidize, melt, and relocate. The potential for and the subsequent impact of the upper internals to heat up, oxidize, fail, and relocate during a severe accident was investigated. A higher fidelity representation of the shroud dome, steam separators, and steam driers was developed in MELCOR v1.8.6 by extending the core region upwards. This modeling effort entailed adding 45 additional core cells and control volumes, 98 flow paths, and numerous control functions. The model accounts for the mechanical loading and structural integrity, oxidation, melting, flow area blockage, and relocation of the various components. The results indicate that the upper internals can reach high temperatures during a severe accident; they are predicted to reach a high enough temperature such that they lose their structural integrity and relocate. The additional 100 tons of stainless steel debris influences the subsequent in-vessel and ex-vessel accident progression.
Heat Transfer and Fluid Flow in Naturally Ventilated Greenhouses
Directory of Open Access Journals (Sweden)
M. Elashmawy
2017-08-01
Full Text Available In this paper, heat transfer and fluid flow in naturally ventilated greenhouses are studied numerically for tow configuration according to the number and positions of the opening. The equations governing the phenomenon are developed using the stream function-vorticity formalism and solved using the finite volume method. The aim of the study is to investigate how buoyancy forces inﬂuence airﬂow and temperature patterns inside the greenhouse. Rayleigh number is the main parameter which changes from 103 to 106 and Prandtl number is ﬁxed at Pr=0.71. Results are reported in terms of stream function, isotherms and average Nusselt number. It is found that the flow structure is sensitive to the value of Rayleigh number and the number of openings. Also, that using asymmetric opening positions improve the natural ventilation and facilitate the occurrence of buoyancy induced upward cross-airflow inside the greenhouse.
Turbulent flow heat transfer in ET-RR-1
International Nuclear Information System (INIS)
Khattab, M.; Mina, A.R.
1990-01-01
In nuclear reactors the effect of heat transfer coefficient, which depends on the constant C. Is primordial in calculating the clad surface temperatures. To determine the constant C of ET-RR-1 fuel bundles based on in-pile measurements different well known and recommended values of C are verified. A computer program is written to calculate steady thermal core characteristics at different operating conditions. The total flow rate is distributed considering same pressure drop across the core irrespective of bundle location. The total reactor power is readily distributed as Bessel function. The flow and power per bundle are equally distributed among the fuel rods irrespective of their positions inside the bundle. It is found that the constant C equals 0.047 gives acceptable compatibility between measurements and calculations. The maximum clad surface temperature is shifted from the core center
Couette flow regimes with heat transfer in rarefied gas
Energy Technology Data Exchange (ETDEWEB)
Abramov, A. A., E-mail: alabr54@mail.ru; Butkovskii, A. V., E-mail: albutkov@mail.ru [Zhukovski Central Aerohydrodynamics Institute (Russian Federation)
2013-06-15
Based on numerical solution of the Boltzmann equation by direct statistic simulation, the Couette flow with heat transfer is studied in a broad range of ratios of plate temperatures and Mach numbers of a moving plate. Flow regime classification by the form of the dependences of the energy flux and friction stress on the Knudsen number Kn is proposed. These dependences can be simultaneously monotonic and nonmonotonic and have maxima. Situations are possible in which the dependence of the energy flux transferred to a plate on Kn has a minimum, while the dependence of the friction stress is monotonic or even has a maximum. Also, regimes exist in which the dependence of the energy flux on Kn has a maximum, while the dependence of the friction stress is monotonic, and vice versa.
Flow regimes and heat transfer in vertical narrow annuli
International Nuclear Information System (INIS)
Ulke, A.; Goldberg, I.
1993-01-01
In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ''isolated'' bubbles, ''coalesced'' bubbles and liquid deficient regions have been defined
International Nuclear Information System (INIS)
Khattab, M.S.; Mariy, A.H.; Hilal, M.M.; El-Morshdy, S.E.
1999-01-01
The phenomena of two-phase flow through horizontal, vertical and inclined tubes has many engineering applications in heat exchangers, boilers, nuclear reactors, steam generators and refrigerators..etc. In the present investigation, two-phase flow heat transfer and pressure drop have been experimentally studied at different orientations of an annular channel test section subjected to uniform heat flux. The annular test section was internally heated by a DC power supply. The experimental investigation has been classified onto three steady state groups of (heat flux, mass flux, and inlet temperature). The first group was at 522.41 kw/m 2 , 310 kg/m 2 s and 89.4 degree C; the second was at 779.72 kw/m 2 , 507 Hg/m 2 s and 94.3 degree C and the third was at 1019.97 kw/m 2 s 701 kg/m 2 100 degree C. The effect of inclination on the two-phase heat transfer coefficient and pressure drop are presented and discussed. The present experimental results are compared with some existing correlations for two phase flow boiling heat transfer in horizontal and vertical tubes at their range of validity. The comparison shows a good agreement. The behavior of the two-phase mean heat transfer coefficient shows a small enhancement due to inclination from horizontal to vertical orientation. The enhancement factor relating the two-phase heat transfer coefficient with the inclination angle is predicted
DEFF Research Database (Denmark)
Trangmar, Steven J; Chiesa, Scott T; Llodio, Iñaki
2015-01-01
Dehydration hastens the decline in cerebral blood flow (CBF) during incremental exercise, whereas the cerebral metabolic rate for O2 (CMRO2 ) is preserved. It remains unknown whether CMRO2 is also maintained during prolonged exercise in the heat and whether an eventual decline in CBF is coupled...... to fatigue. Two studies were undertaken. In study 1, 10 male cyclists cycled in the heat for ∼2 h with (control) and without fluid replacement (dehydration) while internal and external carotid artery blood flow and core and blood temperature were obtained. Arterial and internal jugular venous blood samples...... were assessed with dehydration to evaluate CMRO2 . In study 2, in 8 male subjects, middle cerebral artery blood velocity was measured during prolonged exercise to exhaustion in both dehydrated and euhydrated states. After a rise at the onset of exercise, internal carotid artery flow declined...
Mathematics of flexible risers including pressure and internal flow affects
Energy Technology Data Exchange (ETDEWEB)
Seyed, F.B. (John Brown Engineers and Constructors Ltd., London (GB)); Patel, M.H. (University Coll., London (GB). Dept. of Mechanical Engineering)
1992-01-01
Derivations are presented for calculation of pressure and internal flow induced forces on flexible risers and other curved pipes using a mathematically rigorous approach. Approximate and exact methods are presented for calculation of pressure forces on straight and curved pipes in two dimensions. The mathematical identity of these equations with those for effective tension is illustrated. The force arising from the flow of an internal fluid of constant density is then calculated and combined with those for pressure forces in derivation of the catenary equations including pressure and internal flow terms. It is shown that internal flow contributes a new term to the expression for effective tension. These governing equations are then reduced for the specific cases of simple catenary, steep-S, lazy-S, steep-wave and lazy-wave risers. In each case, the solution method has been presented and the governing equilibrium and geometric compatability conditions cited. (author).
CFD Study of Deteriorated Turbulent Heat Transfer in Upward Flow
International Nuclear Information System (INIS)
Nietiadi, Yohanes Setiawan; Lee, Jeong Ik; Addad, Yacine
2014-01-01
DTHT regime can be induced by two effects: buoyancy and acceleration. Apart from these two deteriorating effects, another unique behavior of fluid in the DTHT regime is that the convective heat transfer rate will continue to deteriorate until it reaches certain point. The downstream of this point, is known as the recovery region, where the convective heat transfer rate returns back to the high values by recovering turbulence. We called this phenomena as re-turbulization.. The map of the DTHT regime can be seen from fig. 2, where the x-axis is the buoyancy parameter and y-axis is the acceleration parameter which is the agreed governing non-dimensional numbers among the researchers to illustrate the phenomena. The Buoyancy parameter is defind in Eq. (1) and the acceleration parameter is defined in Eq. (2), respectively. The threshold value for both effects to move from the forced turbulent heat transfer to the DTHT regime are found to be Bo* ≥ 2x10 -6 and Kv ≥ 2.5x10 -6 in the previous works. Bo * =Gr q /Re 3 '. 425 Pr 0 '. 8 (1). K v =4q + /Re (2). Many experiments and simulation have been done to investigate this phenomenon and the boundary of the regime. However, very limited number of experiment was conducted in the regime where buoyancy effect and acceleration effect are in the same order of magnitude and high enough to cause DTHT (mixed DTHT). Some important experimental researches that have been done in the gas DTHT regime is Lee et al. who investigated the heat transfer of gas flow in the range of buoyancy parameter from 3x10 -9 to 10 -5 and acceleration parameter span from 6x10 -8 to 5x10 -6 and presented the behavior of Nusselt number ratio from the experiment as fig. 3 and fig. 4. This paper will discuss a Computational Fluid Dynamics analysis on DTHT by assuming hypothetical boundary conditions especially on the mixed DTHT regime. It has been found that a gas cooled fast reactor has a tendency to operate in the Deteriorated Turbulent Heat
CFD analysis of flow and heat transfer in Canadian supercritical water reactor bundle
International Nuclear Information System (INIS)
Podila, K.; Rao, Y.F.
2015-01-01
Highlights: • Flow and heat transfer in SCWR fuel bundle design by AECL is studied using CFD. • Bare-rod bundle geometry is tested at 23.5, 25 and 28 MPa using STAR-CCM+ code. • SST k–ω low-Re model was used to study occurrence of heat transfer deterioration. - Abstract: Within the Gen-IV International Forum, AECL is leading the effort in developing a conceptual design for the Canadian SCWR. AECL proposed a new fuel bundle design with two rings of fuel elements placed between central flow tube and the pressure tube. In line with the scope of the conceptual design, the objective of the present CFD work is to aid in developing a bundle heat transfer correlation for the Canadian SCWR fuel bundle design. This paper presents results from an ongoing effort in determining the conditions favorable for occurrence of HTD in the supercritical bundle flows. In the current investigation, bare-rod bundle geometry was tested for the proposed fuel bundle design at 23.5, 25 and 28 MPa using STAR-CCM+ CFD code. Taking advantage of the design symmetry of the fuel bundle, only 1/32 of the computational domain was simulated. The low-Reynolds number modification of SST k–ω turbulence model along with y + < 1 was used in the simulations. For lower mass flow simulations, the increase of inlet temperature and operational pressure was found effective in reducing the occurrence of HTD. For higher mass flow simulations, normal heat transfer behaviour was observed except for the lower pressure range (23.5 MPa)
The effect of buoyancy on flow and heat transfer in curved pipes
Mochizuki, Munekazu; Ishigaki, Hiroshi; 望月 宗和; 石垣 博
1994-01-01
Fully developed laminar flow in a heated horizontal curved pipe is studied numerically. The thermal boundary conditions at the wall are uniform wall heat flux axially and uniform wall temperature peripherally. Flow and heat transfer are governed by Dean number, Prandtl number and buoyancy number. Detailed prediction of the friction factor, average heat transfer rate, velocity profile, temperature profile and secondary-flow streamlines are given.
Volcanic eruptions on Io: Heat flow, resurfacing, and lava composition
Blaney, Diana L.; Johnson, Torrence V.; Matson, Dennis L.; Veeder, Glenn J.
1995-01-01
We model an infrared outburst on Io as being due to a large, erupting lava flow which increased its area at a rate of 1.5 x 10(exp 5)/sq m and cooled from 1225 to 555 K over the 2.583-hr period of observation. The inferred effusion rate of 3 x 10(exp 5) cu m/sec for this eruption is very high, but is not unprece- dented on the Earth and is similar to the high eruption rates suggested for early lunar volcanism. Eruptions occur approxi- mately 6% of the time on Io. These eruptions provide ample resurfacing to explain Io's lack of impact craters. We suggest that the large total radiometric heat flow, 10(exp 14) W, and the size and temperature distribution of the thermal anomalies (McEwen et al. 1992; Veeder et al. 1994) can be accounted for by a series of silicate lava flows in various stages of cooling. We propose that the whole suite of Io's currently observed thermal anomalies was produced by multiple, high-eruptive-rate silicate flows within the past century.
Performance and internal flow characteristics of a cross-flow turbine by guide vane angle
International Nuclear Information System (INIS)
Chen, Z M; Choi, Y D
2013-01-01
This study attempts to investigate the performance and internal flow characteristics of a cross-flow turbine by guide vane angle. In order to improve the performance of a cross flow turbine, the paper presents a numerical investigation of the turbine with air supply and discusses the influence of variable guide vane angle on the internal flow. A newly developed air supply from air suction Hole is adopted. To investigate the performance and internal flow of the cross-flow turbine, the CFD software based on the two-phase flow model is utilized. The numerical grids are made in two-dimensional geometry in order to shorten the time of two-phase calculations. Then a series of CFD analysis has been conducted in the range of different guide vane angle. Moreover, local output power is divided at different stages and the effect of air layer in each stage is examined
William T. Simpson
2004-01-01
Equations for a two-dimensional finite difference heat flow analysis were developed and applied to ponderosa pine and Douglas-fir square timbers to calculate the time required to heat the center of the squares to target temperature. The squares were solid piled, which made their surfaces inaccessible to the heating air, and thus surface temperatures failed to attain...
Nagihara, Seiichi; Zacny, Kris; Hedlund, Magnus; Taylor, Patrick T.
2012-01-01
Geothermal heat flow measurements are a high priority for the future lunar geophysical network missions recommended by the latest Decadal Survey of the National Academy. Geothermal heat flow is obtained as a product of two separate measurements of geothermal gradient and thermal conductivity of the regolith/soil interval penetrated by the instrument. The Apollo 15 and 17 astronauts deployed their heat flow probes down to 1.4-m and 2.3-m depths, respectively, using a rotary-percussive drill. However, recent studies show that the heat flow instrument for a lunar mission should be capable of excavating a 3-m deep hole to avoid the effect of potential long-term changes of the surface thermal environment. For a future robotic geophysical mission, a system that utilizes a rotary/percussive drill would far exceed the limited payload and power capacities of the lander/rover. Therefore, we are currently developing a more compact heat flow system that is capable of 3-m penetration. Because the grains of lunar regolith are cohesive and densely packed, the previously proposed lightweight, internal hammering systems (the so-called moles ) are not likely to achieve the desired deep penetration. The excavation system for our new heat flow instrumentation utilizes a stem which winds out of a pneumatically driven reel and pushes its conical tip into the regolith. Simultaneously, gas jets, emitted from the cone tip, loosen and blow away the soil. Lab tests have demonstrated that this proboscis system has much greater excavation capability than a mole-based heat flow system, while it weighs about the same. Thermal sensors are attached along the stem and at the tip of the penetrating cone. Thermal conductivity is measured at the cone tip with a short (1- to 1.5-cm long) needle sensor containing a resistance temperature detector (RTD) and a heater wire. When it is inserted into the soil, the heater is activated. Thermal conductivity of the soil is obtained from the rate of temperature
Hoekstra, Arjen Ysbert; Hung, P.Q.
2005-01-01
The water that is used in the production process of a commodity is called the ‘virtual water’ contained in the commodity. International trade of commodities brings along international flows of virtual water. The objective of this paper is to quantify the volumes of virtual water flows between
International Nuclear Information System (INIS)
Mehta, Balkrishna; Khandekar, Sameer
2014-01-01
Highlights: • Infra-red thermographic study of Taylor bubble train flow in square mini-channel. • Design of experiments for measurement of local streamwise Nusselt number. • Minimizing conjugate heat transfer effects and resulting errors in data reduction. • Benchmarking against single-phase flow and three-dimensional computations. • Local heat transfer enhancement up to two times due to Taylor bubble train flow. -- Abstract: In mini/micro confined internal flow systems, Taylor bubble train flow takes place within specific range of respective volume flow ratios, wherein the liquid slugs get separated by elongated Taylor bubbles, resulting in an intermittent flow situation. This unique flow characteristic requires understanding of transport phenomena on global, as well as on local spatio-temporal scales. In this context, an experimental design methodology and its validation are presented in this work, with an aim of measuring the local heat transfer coefficient by employing high-resolution InfraRed Thermography. The effect of conjugate heat transfer on the true estimate of local transport coefficients, and subsequent data reduction technique, is discerned. Local heat transfer coefficient for (i) hydrodynamically fully developed and thermally developing single-phase flow in three-side heated channel and, (ii) non-boiling, air–water Taylor bubble train flow is measured and compared in a mini-channel of square cross-section (5 mm × 5 mm; D h = 5 mm, Bo ≈ 3.4) machined on a stainless steel substrate (300 mm × 25 mm × 11 mm). The design of the setup ensures near uniform heat flux condition at the solid–fluid interface; the conjugate effects arising from the axial back conduction in the substrate are thus minimized. For benchmarking, the data from single-phase flow is also compared with three-dimensional computational simulations. Depending on the employed volume flow ratio, it is concluded that enhancement of nearly 1.2–2.0 times in time
Shang, De-Yi
2012-01-01
This book presents recent developments in our systematic studies of hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, as well as accelerating film flow of non-Newtonian power-law fluids (FFNF). These new developments provided in this book are (i) novel system of analysis models based on the developed New Similarity Analysis Method; (ii) a system of advanced methods for treatment of gas temperature- dependent physical properties, and liquid temperature- dependent physical properties; (iii) the organically combined models of the governing mathematical models with those on treatment model of variable physical properties; (iv) rigorous approach of overcoming a challenge on accurate solution of three-point boundary value problem related to two-phase film boiling and condensation; and (v) A pseudo-similarity method of dealing with thermal boundary layer of FFNF for greatly simplifies the heat-transfer analysis and numerical calculati...
Are international fund flows related to exchange rate dynamics?
Li, Suxiao; de Haan, Jakob; Scholtens, Bert
2018-01-01
Employing monthly data for 53 countries between 1996 and 2015, we investigate the relationship between international fund flows and exchange rate dynamics. We find strong co-movement between funds flows (as measured with the EPFR Global data base) and bilateral real exchange rates vis-à-vis the USD.
Numerical fluid flow and heat transfer calculations on multiprocessor systems
Energy Technology Data Exchange (ETDEWEB)
Oehman, G.A.; Malen, T.E.; Kuusela, P.
1989-01-01
The first part of the report presents the basic principles of parallel processing, and factors influencing tbe efficiency of practical applications are discussed. In a multiprocessor computer, different parts of the program code are executed in parallel, i.e. simultaneous with respect to time, on different processors, and thus it becomes possible to decrease the overall computation time by a factor, which in the ideal case is equal to the number of processors. The application study starts from the numerical solution of the twodimesional Laplace equation, which describes the steady heat conduction in a solid plate and advances through the solution of the three dimensional Laplace equation to the case of study laminar fluid flow in a twodimensional box at Reynolds numbers up to 20. Hereby the stream function-vorticity method is first applied and the SIMPLER method. The conventional (sequential) numerical algoritms for these fluid flow and heat transfer problems are found not to be ideally suited for conversion to parallel computation, but sped-up ratios considerably above 50 % of the theoretical maximum are regularly achieved in the runs. The numerical procedures we coded in the OCCAM-2 language and the test runs were performed at who Akademi on the imperimental HATHI-computers containing 16 T4l4 and 100 INMOS T800 transputers respectively.
Numerical fluid flow and heat transfer calculations on multiprocessor systems
Energy Technology Data Exchange (ETDEWEB)
Oehman, G.A.; Malen, T.E.; Kuusela, P.
1989-12-31
The first part of the report presents the basic principles of parallel processing, and factors influencing tbe efficiency of practical applications are discussed. In a multiprocessor computer, different parts of the program code are executed in parallel, i.e. simultaneous with respect to time, on different processors, and thus it becomes possible to decrease the overall computation time by a factor, which in the ideal case is equal to the number of processors. The application study starts from the numerical solution of the twodimesional Laplace equation, which describes the steady heat conduction in a solid plate and advances through the solution of the three dimensional Laplace equation to the case of study laminar fluid flow in a twodimensional box at Reynolds numbers up to 20. Hereby the stream function-vorticity method is first applied and the SIMPLER method. The conventional (sequential) numerical algoritms for these fluid flow and heat transfer problems are found not to be ideally suited for conversion to parallel computation, but sped-up ratios considerably above 50 % of the theoretical maximum are regularly achieved in the runs. The numerical procedures we coded in the OCCAM-2 language and the test runs were performed at who Akademi on the imperimental HATHI-computers containing 16 T4l4 and 100 INMOS T800 transputers respectively.
Occurrence of critical heat flux during blowdown with flow reversal
International Nuclear Information System (INIS)
Leung, J.C.M.
1977-01-01
A small-scale experiment using Freon-11 at 130 0 F (54.4 0 C) and 65 psia (0.45 MPa) in a well-instrumented, transparent annular test section was used to study the occurrence of critical heat flux (CHF) during blowdown with flow reversal. The inner stainless steel tube of the annulus was uniformly heated over its 61-cm length. Inlet and exit void fractions were measured by a capacitance technique. Flow-regime transition was observed with high-speed photography. A 1-hr contact time between Freon-11 and nitrogen at 130 0 F (54.4 0 C) and 60 psig (0.517 MPa) was found to greatly affect the steady-state subcooled-boiling initial conditions. Delay in bubble growth was observed in adiabatic blowdown runs. This was caused by the conditions of thermodynamic nonequilibrium required for the unstable bubble growth. For the diabatic runs, equilibrium was more closely approached in the test section during the early phase of blowdown
Effects of variable specific heat on energy transfer in a high-temperature supersonic channel flow
Chen, Xiaoping; Li, Xiaopeng; Dou, Hua-Shu; Zhu, Zuchao
2018-05-01
An energy transfer mechanism in high-temperature supersonic turbulent flow for variable specific heat (VSH) condition through turbulent kinetic energy (TKE), mean kinetic energy (MKE), turbulent internal energy (TIE) and mean internal energy (MIE) is proposed. The similarities of energy budgets between VSH and constant specific heat (CSH) conditions are investigated by introducing a vibrational energy excited degree and considering the effects of fluctuating specific heat. Direct numerical simulation (DNS) of temporally evolving high-temperature supersonic turbulent channel flow is conducted at Mach number 3.0 and Reynolds number 4800 combined with a constant dimensional wall temperature 1192.60 K for VSH and CSH conditions to validate the proposed energy transfer mechanism. The differences between the terms in the two kinetic energy budgets for VSH and CSH conditions are small; however, the magnitude of molecular diffusion term for VSH condition is significantly smaller than that for CSH condition. The non-negligible energy transfer is obtained after neglecting several small terms of diffusion, dissipation and compressibility related. The non-negligible energy transfer involving TIE includes three processes, in which energy can be gained from TKE and MIE and lost to MIE. The same non-negligible energy transfer through TKE, MKE and MIE is observed for both the conditions.
Flow regimes and mechanistic modeling of critical heat flux under subcooled flow boiling conditions
Le Corre, Jean-Marie
Thermal performance of heat flux controlled boiling heat exchangers are usually limited by the Critical Heat Flux (CHF) above which the heat transfer degrades quickly, possibly leading to heater overheating and destruction. In an effort to better understand the phenomena, a literature review of CHF experimental visualizations under subcooled flow boiling conditions was performed and systematically analyzed. Three major types of CHF flow regimes were identified (bubbly, vapor clot and slug flow regime) and a CHF flow regime map was developed, based on a dimensional analysis of the phenomena and available data. It was found that for similar geometric characteristics and pressure, a Weber number (We)/thermodynamic quality (x) map can be used to predict the CHF flow regime. Based on the experimental observations and the review of the available CHF mechanistic models under subcooled flow boiling conditions, hypothetical CHF mechanisms were selected for each CHF flow regime, all based on a concept of wall dry spot overheating, rewetting prevention and subsequent dry spot spreading. It is postulated that a high local wall superheat occurs locally in a dry area of the heated wall, due to a cyclical event inherent to the considered CHF two-phase flow regime, preventing rewetting (Leidenfrost effect). The selected modeling concept has the potential to span the CHF conditions from highly subcooled bubbly flow to early stage of annular flow. A numerical model using a two-dimensional transient thermal analysis of the heater undergoing nucleation was developed to mechanistically predict CHF in the case of a bubbly flow regime. In this type of CHF two-phase flow regime, the high local wall superheat occurs underneath a nucleating bubble at the time of bubble departure. The model simulates the spatial and temporal heater temperature variations during nucleation at the wall, accounting for the stochastic nature of the boiling phenomena. The model has also the potential to evaluate
Electroosmotic flow and Joule heating in preparative continuous annular electrochromatography.
Laskowski, René; Bart, Hans-Jörg
2015-09-01
An openFOAM "computational fluid dynamic" simulation model was developed for the description of local interaction of hydrodynamics and Joule heating in annular electrochromatography. A local decline of electrical conductivity of the background eluent is caused by an electrokinetic migration of ions resulting in higher Joule heat generation. The model equations consider the Navier-Stokes equation for incompressible fluids, the energy equation for stationary temperature fields, and the mass transfer equation for the electrokinetic flow. The simulations were embedded in commercial ANSYS Fluent software and in open-source environment openFOAM. The annular gap (1 mm width) contained an inorganic C8 reverse-phase monolith as stationary phase prepared by an in situ sol-gel process. The process temperature generated by Joule heating was determined by thermal camera system. The local hydrodynamics in the prototype was detected by a gravimetric contact-free measurement method and experimental and simulated values matched quite well. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Meng Xianke; Sun Zhongning; Zhou Ping; Xu Guangzhan
2012-01-01
The water-cooled pebble bed reactor core is the porous channels stacked with spherical fuel elements, having evident effect on enhancing heat transfer. Owing to the variability and randomness characteristics of it's interstice, pebble bed channels have a very complex heat transfer situation and have little correlative research. In order to research the heat transfer characters of pebble bed channels with internal heat source, electromagnetic induction heating method was adopted for overall heating the pebble bed which was composed of 8 mm diameter steel balls, and the internal heat transfer characteristics were researched. By comparing and analyzing the experimental data, the rule of power distribution and heat transfer coefficient with heat flux density, inlet temperature and working fluid's Re were got. According to the experimental data fitting, the dimensionless average heat transfer coefficient correlation criteria was got. The fitting results are good agreement with the experimental results within 12% difference. (authors)
South Korea's Experience with International Capital Flows
Marcus Noland
2005-01-01
South Korea%u2019s experience is unparalleled in its combination of sustained prosperity, capital controls, and financial crisis. Over several decades, South Korea experienced rapid sustained growth in the presence of capital controls. These controls and the de-linking of domestic and international financial markets were an essential component of the country's state-led development strategy. As the country developed, opportunities for easy technological catch-up eroded, requiring more sophist...
International Nuclear Information System (INIS)
Lin, Yueh-Hung; Li, Guang-Cheng; Yang, Chien-Yuh
2015-01-01
This study provides an Infrared Thermal Image observation on the evaporation heat transfer of refrigerant R-410A in plate heat exchanger with various flow arrangement and exit superheat conditions. An experimental method was derived for estimating the superheat region area of two-phase refrigerant evaporation in plate heat exchanger. The experimental results show that the superheat region area for parallel flow is much larger than that for counter flow as that estimated by Yang et al. [9]. There is an early superheated region at the central part of the plate heat exchanger for parallel flow arrangement. This effect is not significant for counter flow arrangement. The Yang et al. [9] method under estimated the superheat area approximately 40%–53% at various flow rates and degree of exit superheat. Even though the flow inside a plate heat exchanger is extremely turbulent because of the chevron flow passages, the assumption of uniform temperature distribution in the cross section normal to the bulk flow direction will cause significant uncertainties for estimating the superheat area for refrigerant evaporating in a plate heat exchanger
International Nuclear Information System (INIS)
Siddiqui, Faisal A.; Dasgupta, Engr Sarbadaman; Fartaj, Amir
2012-01-01
Highlights: ► Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. ► Hot ethylene glycol–water mixture (50:50) at constant mass flow rate is used against varying air flow. ► Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. ► General correlations are proposed for air side heat transfer and fluid flow parameters. - Abstract: Air side force convective heat transfer and flow characteristics of cross-flow mesochannel heat exchanger are investigated experimentally. A series of experiments representing 36 different operating conditions have been conducted on a finned mesochannel heat exchanger through the fully automated dynamic single-phase experimental facility which is capable of handling a wide variety of working fluids in air-to-liquid cross-flow orientation. The mesochannel heat exchanger is made of 15 aluminum slabs with arrays of wavy fins between slabs; 68 one millimeter circular diameter port located at each slab, and the air side frontal area of 304-mm × 304-mm. The ethylene glycol–water mixture as the working fluid in the liquid side was forced to flow through mesochannels maintaining constant inlet temperature and flow rate at 74 °C and 0.0345 kg/s respectively whereas the inlet flowing air into the arrays of wavy fins was changed at four different temperature levels from 28 °C to 43 °C. Frontal air velocity was altered in nine steps from 3 m/s to 11 m/s at each temperature level corresponding range of Reynolds number 752 a a ) and Colburn factor (j a ) were found higher in comparison with other studies.
Computation of high Reynolds number internal/external flows
Cline, M. C.; Wilmoth, R. G.
1981-01-01
A general, user oriented computer program, called VNAP2, was developed to calculate high Reynolds number, internal/ external flows. The VNAP2 program solves the two dimensional, time dependent Navier-Stokes equations. The turbulence is modeled with either a mixing-length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack Scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented.
Computation of high Reynolds number internal/external flows
International Nuclear Information System (INIS)
Cline, M.C.; Wilmoth, R.G.
1981-01-01
A general, user oriented computer program, called VNAP2, has been developed to calculate high Reynolds number, internal/external flows. VNAP2 solves the two-dimensional, time-dependent Navier-Stokes equations. The turbulence is modeled with either a mixing-length, a one transport equation, or a two transport equation model. Interior grid points are computed using the explicit MacCormack scheme with special procedures to speed up the calculation in the fine grid. All boundary conditions are calculated using a reference plane characteristic scheme with the viscous terms treated as source terms. Several internal, external, and internal/external flow calculations are presented
A mechanistic model of heat transfer for gas-liquid flow in vertical wellbore annuli.
Yin, Bang-Tang; Li, Xiang-Fang; Liu, Gang
2018-01-01
The most prominent aspect of multiphase flow is the variation in the physical distribution of the phases in the flow conduit known as the flow pattern. Several different flow patterns can exist under different flow conditions which have significant effects on liquid holdup, pressure gradient and heat transfer. Gas-liquid two-phase flow in an annulus can be found in a variety of practical situations. In high rate oil and gas production, it may be beneficial to flow fluids vertically through the annulus configuration between well tubing and casing. The flow patterns in annuli are different from pipe flow. There are both casing and tubing liquid films in slug flow and annular flow in the annulus. Multiphase heat transfer depends on the hydrodynamic behavior of the flow. There are very limited research results that can be found in the open literature for multiphase heat transfer in wellbore annuli. A mechanistic model of multiphase heat transfer is developed for different flow patterns of upward gas-liquid flow in vertical annuli. The required local flow parameters are predicted by use of the hydraulic model of steady-state multiphase flow in wellbore annuli recently developed by Yin et al. The modified heat-transfer model for single gas or liquid flow is verified by comparison with Manabe's experimental results. For different flow patterns, it is compared with modified unified Zhang et al. model based on representative diameters.
Flow vibrations and dynamic instability of heat exchanger tube bundles
International Nuclear Information System (INIS)
Granger, S.; Langre, E. de
1995-01-01
This paper presents a review of external-flow-induced vibration of heat exchanger tube bundles. Attention is focused on a dynamic instability, known as ''fluidelastic instability'', which can develop when flow is transverse to the tube axis. The main physical models proposed in the literature are successively reviewed in a critical way. As a consequence, some concepts are clarified, some a priori plausible misinterpretations are rejected and finally, certain basic mechanisms, induced by the flow-structure interaction and responsible for the ultimate onset of fluidelastic instability, are elucidated. Design tools and methods for predictive analysis of industrial cases are then presented. The usual design tool is the ''stability map'', i.e. an empirical correlation which must be interpreted in a conservative way. Of course, when using this approach, the designer must also consider reasonable safety margins. In the area of predictive analysis, the ''unsteady semi-analytical models'' seem to be a promising and efficient methodology. A modern implementation of these ideas mix an original experimental approach for taking fluid dynamic forces into account, together with non-classical numerical methods of mechanical vibration. (authors). 20 refs., 9 figs
Unstable fluid flow in a water-cooled heating channel
International Nuclear Information System (INIS)
Delayre, R.; Saunier, J.P.
1961-01-01
Experimental investigations of the instable behavior of a pressurized water flow in forced convection in a heating channel, with subcooled or bulk boiling have been carried. Tests were conducted at 1140, 850 and 570 psi. The test section was 35 in. high, surmounted by a 25.4 in. riser, these sections were by-passed by a pipe where the flow was between 1 and 4 times the flow in the test section. The water velocity (in the test section) was between 1.6 and 6.6 ft/s. Under certain conditions oscillations with a period of several seconds and perfectly stable have been observed. A mathematical model has been defined and a good agreement obtained for the main characteristics of the oscillations. It seems that the dimensions of the riser have a determining effect: the inception of bulk boiling gives an important variation of the driving head which can generate oscillations due to the non-zero delay for the system to reach its equilibrium. (author) [fr
Flow visualization study of inverted annular flow of post dryout heat transfer region
International Nuclear Information System (INIS)
Ishii, M.; De Jarlais, G.
1985-01-01
The inverted annular flow is important in the area of LWR accident analysis in terms of the maximum cladding temperature and effectiveness of the emergency core cooling. However, the inverted annular flow thermal-hydraulics is not well understood due to its special heat transfer condition of film boiling. The review of existing data indicates further research is needed in the areas of basic hydrodynamics related to liquid core disintegration mechanisms, slug and droplet formation, entrainment, and droplet size distributions. In view of this, the inverted flow is studied in detail experimentally. A new experimental apparatus has been constructed in which film boiling heat transfer can be established in a transparent test section. The test section consists of two coaxial quartz tubes. The annular gap between these two tubes is filled with a hot, clear fluid (syltherm 800) so as to maintain film boiling temperatures and heat transfer rates at the inner quartz tube wall. Data on liquid core stability, core break-up mechanism, and dispersed-core liquid slug and droplet sizes are obtained using F 113 as a test fluid. Both high speed movies and flash photographs (3 μsec) are used
Numerical modelling of convective heat transport by air flow in permafrost talus slopes
Directory of Open Access Journals (Sweden)
J. Wicky
2017-06-01
Full Text Available Talus slopes are a widespread geomorphic feature in the Alps. Due to their high porosity a gravity-driven internal air circulation can be established which is forced by the gradient between external (air and internal (talus temperature. The thermal regime is different from the surrounding environment, leading to the occurrence of permafrost below the typical permafrost zone. This phenomenon has mainly been analysed by field studies and only few explicit numerical modelling studies exist. Numerical simulations of permafrost sometimes use parameterisations for the effects of convection but mostly neglect the influence of convective heat transfer in air on the thermal regime. In contrast, in civil engineering many studies have been carried out to investigate the thermal behaviour of blocky layers and to improve their passive cooling effect. The present study further develops and applies these concepts to model heat transfer in air flows in a natural-scale talus slope. Modelling results show that convective heat transfer has the potential to develop a significant temperature difference between the lower and the upper parts of the talus slope. A seasonally alternating chimney-effect type of circulation develops. Modelling results also show that this convective heat transfer leads to the formation of a cold reservoir in the lower part of the talus slope, which can be crucial for maintaining the frozen ground conditions despite increasing air temperatures caused by climate change.
Energy Technology Data Exchange (ETDEWEB)
Ranganayakulu, C. [Aeronautical Development Agency, Bangalore (India); Seetharamu, K.N. [School of Mechanical Engineering, Univ. of Southern Malaysia (KCP), Tronoh (Malaysia)
2000-05-01
An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effect of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow distribution on both hot and cold fluid sides is carried out using a finite element method. Using the fluid flow maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of wall longitudinal heat conduction and inlet fluid flow nonuniformity on crossflow plate-fin heat exchanger. (orig.)
Internal flow of acoustically levitated drops undergoing sectorial oscillations
International Nuclear Information System (INIS)
Shen, C.L.; Xie, W.J.; Yan, Z.L.; Wei, B.
2010-01-01
We present the experimental observation and theoretical analysis of fluid flow in acoustically levitated water drop undergoing sectorial oscillations. The fluid always flows between the extended sections and the compressed sections. The magnitude of fluid velocity decreases from the equatorial fringe to the centre of levitated drop. The maximum fluid velocity is 60-160 mm/s and the Reynolds number of the oscillations is estimated to be 137-367. The internal flow of the drop is analyzed as potential flow, and the fluid velocity is found to be horizontal. In the equatorial plane, the calculated stream lines and velocity profiles agree well with the experimental observations.
International Nuclear Information System (INIS)
Berezin, A.N.; Grabezhnaya, V.A.; Mikheev, A.S.; Parfenov, A.S.
2014-01-01
The results of the work to determine the heat transfer coefficient in crossflow by lead of pipes are presented. The study was conducted at supercritical pressure in the water circuit. There was a significant inequality in the distribution of the heat flow in different rows of the bundle of heat exchange tubes of corridor location at crossflow their lead. The experimentally determined heat transfer coefficients from the lead differ substantially from those generally accepted recommendations for the calculation of heat transfer at cross flow of rod bundle by liquid metal. The experimental results are close to those obtained earlier on the model with cross flow of heat exchanger tubes bundle by lead alloy with bismuth [ru
The heat-transfer performance of gas—solid trickle flow over a regularly stacked packing
Verver, A.B.; van Swaaij, Willibrordus Petrus Maria
1986-01-01
The heat-transfer behaviour of a countercurrent gas—solid trickle flow contactor is studied, using coarse sand particles as the solids phase. Experimental data on the overall heat-transfer rate constant between the gas flow and the solid particle flow were obtained in a 0.15 m square cross-section
Void fraction distribution in a heated rod bundle under flow stagnation conditions
Energy Technology Data Exchange (ETDEWEB)
Herrero, V.A.; Guido-Lavalle, G.; Clausse, A. [Centro Atomico Bariloche and Instituto Balseiro, Bariloche (Argentina)
1995-09-01
An experimental study was performed to determine the axial void fraction distribution along a heated rod bundle under flow stagnation conditions. The development of the flow pattern was investigated for different heat flow rates. It was found that in general the void fraction is overestimated by the Zuber & Findlay model while the Chexal-Lellouche correlation produces a better prediction.
International Nuclear Information System (INIS)
Tsang, C.F.
1986-01-01
A summary is given of the authors recent studies in the verification, validation and application of a coupled heat and fluid flow code. Verification has been done against eight analytic and semi-analytic solutions. These solutions include those involving thermal buoyancy flow and fracture flow. Comprehensive field validation studies over a period of four years are discussed. The studies are divided into three stages: (1) history matching, (2) double-blind prediction and confirmation, (3) design optimization. At each stage, parameter sensitivity studies are performed. To study the applications of mathematical models, a problem proposed by the International Energy Agency (IEA) is solved using this verified and validated numerical model as well as two simpler models. One of the simpler models is a semi-analytic method assuming the uncoupling of the heat and fluid flow processes. The other is a graphical method based on a large number of approximations. Variations are added to the basic IEA problem to point out the limits of ranges of applications of each model. A number of lessons are learned from the above investigations. These are listed and discussed
Directory of Open Access Journals (Sweden)
Butrymowicz Dariusz
2016-09-01
Full Text Available The theoretical basis for the indirect measurement approach of mean heat transfer coefficient for the packed bed based on the modified single blow technique was presented and discussed in the paper. The methodology of this measurement approach dedicated to the matrix of the rotating regenerative gas heater was discussed in detail. The testing stand consisted of a dedicated experimental tunnel with auxiliary equipment and a measurement system are presented. Selected experimental results are presented and discussed for selected types of matrices of regenerative air preheaters for the wide range of Reynolds number of gas. The agreement between the theoretically predicted and measured temperature profiles was demonstrated. The exemplary dimensionless relationships between Colburn heat transfer factor, Darcy flow resistance factor and Reynolds number were presented for the investigated matrices of the regenerative gas heater.
Flow visualization study of inverted annular flow of post dryout heat transfer region
International Nuclear Information System (INIS)
Ishii, M.; De Jarlais, G.
1987-01-01
The inverted annular flow is important in the area of LWR accident analysis in terms of the maximum cladding temperature and effectiveness of the emergency core cooling. However, the inverted annular flow thermal-hydraulics is not well understood due to its special heat transfer condition of film boiling. In view of this, the inverted flow is studied in detail experimentally. A new experimental apparatus has been constructed in which film boiling heat transfer can be established in a transparent test section. Data on liquid core stability, core break-up mechanism, and dispersed-core liquid slug and droplet sizes are obtained using F 113 as a test fluid. Both high speed movies and flash photographs are used. The inlet section consists of specially designed coaxial nozzles for gas and liquid such that the ideal inverted annular flow can be generated. The roll wave formation, droplet entrainment from wave crests, agitated sections with large interfacial areas, classical sinuous jet instability, jet break-up into multiple liquid ligaments and drop formation from liquid ligaments have been observed in detail. (orig.)
Incorporation of Condensation Heat Transfer in a Flow Network Code
Anthony, Miranda; Majumdar, Alok
2002-01-01
Pure water is distilled from waste water in the International Space Station. The distillation assembly consists of an evaporator, a compressor and a condenser. Vapor is periodically purged from the condenser to avoid vapor accumulation. Purged vapor is condensed in a tube by coolant water prior to entering the purge pump. The paper presents a condensation model of purged vapor in a tube. This model is based on the Finite Volume Method. In the Finite Volume Method, the flow domain is discretized into multiple control volumes and a simultaneous analysis is performed.
Flow visualization study of post-critical heat flux in inverted flow
International Nuclear Information System (INIS)
Babelli, I.; Revankar, S.T.; Ishii, M.
1994-01-01
A visual study of film boiling was carried out to determine the flow regime transition in the post-CHF region for a transient bottom reflooding of a hot transparent test section. The effect of test liquid subcooling and inlet velocity on flow transition as well as on the quench front propagation was investigated. The respective ranges for liquid velocity and subcooling were 1.8-26.8 cm/s, and 20-45 C, respectively. The test liquid was Freon 113 which was introduced into the bottom of the quartz test section whose walls were maintained well above the film boiling temperature of the test liquid, via a transparent heat transfer fluid. The flow regimes observed down stream of the upward moving quench front were the rough wavy, the agitated, and the dispersed droplet/ligaments in agreement with a steady state, two-phase core injection study carried on recently by one of the authors. A correlation for the flow regime transition between the inverted annular and the dispersed droplet/ligament flow patterns was developed. The correlation showed a marked dependence on the void fraction at the CHF location and hence on the flow regime encountered in the pre-CHF region. (orig.)
A way to visualise heat transfer in 3D unsteady flows
Speetjens, M.F.M.
2009-01-01
Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by
Whitesides, R. Harold; Majumdar, Alok K.; Jenkins, Susan L.; Bacchus, David L.
1990-01-01
A series of cold flow heat transfer tests was conducted with a 7.5-percent scale model of the Space Shuttle Rocket Motor (SRM) to measure the heat transfer coefficients in the separated flow region around the nose of the submerged nozzle. Modifications were made to an existing 7.5 percent scale model of the internal geometry of the aft end of the SRM, including the gimballed nozzle in order to accomplish the measurements. The model nozzle nose was fitted with a stainless steel shell with numerous thermocouples welded to the backside of the thin wall. A transient 'thin skin' experimental technique was used to measure the local heat transfer coefficients. The effects of Reynolds number, nozzle gimbal angle, and model location were correlated with a Stanton number versus Reynolds number correlation which may be used to determine the convective heating rates for the full scale Space Shuttle Solid Rocket Motor nozzle.
Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes
Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi
Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.
International Trade Modelling Using Open Flow Networks: A Flow-Distance Based Analysis.
Shen, Bin; Zhang, Jiang; Li, Yixiao; Zheng, Qiuhua; Li, Xingsen
2015-01-01
This paper models and analyzes international trade flows using open flow networks (OFNs) with the approaches of flow distances, which provide a novel perspective and effective tools for the study of international trade. We discuss the establishment of OFNs of international trade from two coupled viewpoints: the viewpoint of trading commodity flow and that of money flow. Based on the novel model with flow distance approaches, meaningful insights are gained. First, by introducing the concepts of trade trophic levels and niches, countries' roles and positions in the global supply chains (or value-added chains) can be evaluated quantitatively. We find that the distributions of trading "trophic levels" have the similar clustering pattern for different types of commodities, and summarize some regularities between money flow and commodity flow viewpoints. Second, we find that active and competitive countries trade a wide spectrum of products, while inactive and underdeveloped countries trade a limited variety of products. Besides, some abnormal countries import many types of goods, which the vast majority of countries do not need to import. Third, harmonic node centrality is proposed and we find the phenomenon of centrality stratification. All the results illustrate the usefulness of the model of OFNs with its network approaches for investigating international trade flows.
Experimental study of supercritical water flow and heat transfer in vertical tube
International Nuclear Information System (INIS)
Li Hongbo; Yang Jue; Lu Donghua; Gu Hanyang; Zhao Meng
2012-01-01
The experiment of flow and heat transfer of supercritical water has been performed on the supercritical water multipurpose test loop co-constructed by China Guangdong Nuclear Power Group and Shanghai Jiao Tong University with a 7.6 mm vertical tube. Heat transfer experimental data is obtained. The results of experimental research of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: (1) Heat transfer enhancement occurs when the bulk temperature reaches pseudo-critical point with low mass flow velocity; (2) The heat transfer co- efficient and Nusselt number are decreased with the increasing of heat flux; (3) The wall temperature is decreased, but the heat transfer coefficient and Nusselt number are increased with the increasing of mass flow velocity; (4) The wall temperature is increased, but the heat transfer coefficient and Nusselt number are decreased with the increasing of sys- tem pressure. (authors)
Simultaneous integrated optimal energy flow of electricity, gas, and heat
International Nuclear Information System (INIS)
Shabanpour-Haghighi, Amin; Seifi, Ali Reza
2015-01-01
Highlights: • Integration of electrical, natural gas, and district heating networks is studied. • Part-load performances of units are considered in modeling. • A modified teaching–learning based optimization is used to solve the problem. • Results show the advantages of the integrated optimization approach. - Abstract: In this paper, an integrated approach to optimize electrical, natural gas, and district heating networks simultaneously is studied. Several interdependencies between these infrastructures are considered in details including a nonlinear part-load performance for boilers and CHPs besides the valve-point effect for generators. A novel approach based on selecting an appropriate set of state-variables for the problem is proposed that eliminates the addition of any new variable to convert irregular equations into a regular set while the optimization problem is still solvable. As a large optimization problem, the optimal solution cannot be achieved by conventional mathematical techniques. Hence, it is better to use evolutionary algorithms instead. In this paper, the well-known modified teaching–learning based optimization algorithm is utilized to solve the multi-period optimal power flow problem of multi-carrier energy networks. The proposed scheme is implemented and applied to a typical multi-carrier energy network. Results are compared with some other conventional heuristic algorithms and the applicability and superiority of the proposed methodology is verified
Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics
LaGraff, John E.; Povinelli, Louis A.; Gostelow, J. Paul; Glauser, Mark
2010-01-01
Topics covered include: Flow Physics and control for Internal and External Aerodynamics (not in TOC...starts on pg13); Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design; Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading; DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines; Cavitation, Flow Structure and Turbulence in the Tip Region of a Rotor Blade; Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows; Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions; Closed-Loop Control of Vortex Formation in Separated Flows; Global Instability on Laminar Separation Bubbles-Revisited; Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers; Instability of a Supersonic Boundary-Layer With Localized Roughness; Active Control of Open Cavities; Amplitude Scaling of Active Separation Control; U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities; Some Issues Related to Integrating Active Flow Control With Flight Control; Active Flow Control Strategies Using Surface Pressure Measurements; Reduction of Unsteady Forcing in a Vaned, Contra-Rotating Transonic Turbine Configuration; Active Flow Control Stator With Coanda Surface; Controlling Separation in Turbomachines; Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets; Reduced Order Modeling Incompressible Flows; Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow; Periodic Forcing of a Turbulent Axisymmetric Wake; Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing; External and Turbomachinery Flow Control Working Group; Boundary Layers, Transitions and Separation; Efficiency Considerations in Low Pressure Turbines; Summary of Conference; and Final Plenary Session
Numerical simulation of internal flow in mixed-flow waterjet propulsion
International Nuclear Information System (INIS)
Wu, T T; Pan, Z Y; Zhang, D Q; Jia, Y Y
2012-01-01
In order to reveal the internal flow characteristic of a mixed-flow waterjet propulsion, a mixed-flow waterjet propulsion under different conditions was simulated based on multi-reference frame(MRF), the standard k − ε turbulent model and SIMPLEC algorithm. The relationship between pump performance instability and internal flow was obtained. The numerical results showed that characteristic instability occurred at 0.65-0.67Q BEP , the reason is that the backflow on the vaned diffuser hub-side blocks the downstream flow from the impeller. Therefore, the flow separates on the pressure surface of the impeller outlet and a strong vortex is generated, then the characteristic instability appeared due to the instability of internal flow. Backflow was found in diffuser passage at 0.65 Q BEP and 0.85 Q BEP , as flow rate decreases, the backflow region and velocity increases. Pressure fluctuation at diffuser inlet and diffuser passages was severe at at 0.65 Q BEP . According to the numerical simulation, the mixed-flow waterjet propulsion has characteristic instability at partial flow rate condition.
International Nuclear Information System (INIS)
Wang Junfeng; Huang Yanping; Wang Yanlin; Song Mingliang
2012-01-01
Highlights: ► Flow regimes were visually investigated in a heated narrow rectangular channel. ► Bubbly, churn, and annular flow were observed. Slug flow was never observed. ► Flow regime transition boundary could be predicted by existing criteria. ► Churn zone in present flow regime maps were poorly predicted by existing criteria. - Abstract: Flow regimes are very important in understanding two-phase flow resistance and heat transfer characteristics. In present work, two-phase flow regimes for steam–water flows in a single-side heated narrow rectangular channel, having a width of 40 mm and a gap of 3 mm, were visually studied at relatively low pressure and low mass flux condition. The flow regimes observed in this experiment could be classified into bubbly, churn and annular flow. Slug flow was never observed at any of the conditions in our experiment. Flow regime maps at the pressure of 0.7 MPa and 1.0 MPa were developed, and then the pressure effect on flow regime transition was analyzed. Based on the experimental results, the comparisons with some existing flow regime maps and transition criteria were conducted. The comparison results show that the bubbly transition boundary and annular formation boundary of heated steam–water flow were consistent with that of adiabatic air–water flow. However, the intermediate flow pattern between bubbly and annular flow was different. Hibiki and Mishima criteria could predict the bubbly transition boundary and annular formation boundary satisfactorily, but it poorly predicted churn zone in present experimental data.
Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.
2012-01-01
Geothermal heat flow is obtained as a product of the geothermal gradient and the thermal conductivity of the vertical soil/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey and previously the International Lunar Network. One of the difficulties associated with lunar heat flow measurement on a robotic mission is that it requires excavation of a relatively deep (approx 3 m) hole in order to avoid the long-term temporal changes in lunar surface thermal environment affecting the subsurface temperature measurements. Such changes may be due to the 18.6-year-cylcle lunar precession, or may be initiated by presence of the lander itself. Therefore, a key science requirement for heat flow instruments for future lunar missions is to penetrate 3 m into the regolith and to measure both thermal gradient and thermal conductivity. Engineering requirements are that the instrument itself has minimal impact on the subsurface thermal regime and that it must be a low-mass and low-power system like any other science instrumentation on planetary landers. It would be very difficult to meet the engineering requirements, if the instrument utilizes a long (> 3 m) probe driven into the ground by a rotary or percussive drill. Here we report progress in our efforts to develop a new, compact lunar heat flow instrumentation that meets all of these science and engineering requirements.
Energy Technology Data Exchange (ETDEWEB)
Eter, Ahmad, E-mail: eng.eter@yahoo.com; Groeneveld, Dé, E-mail: degroeneveld@gmail.com; Tavoularis, Stavros, E-mail: stavros.tavoularis@uottawa.ca
2017-03-15
Highlights: • Measurements of supercritical heat transfer in tubes equipped with obstacles were obtained and compared with results in base tubes. • In general, flow obstacles improve supercritical heat transfer, but under certain conditions have a negative effect on it. • New correlations describing obstacle-enhanced supercritical heat transfer in the liquid-like and gas-like regimes are fitted to the data. - Abstract: Heat transfer measurements to CO{sub 2}-cooled tubes with and without flow obstacles at supercritical pressures were obtained at the University of Ottawa’s supercritical pressure test facility. The effects of obstacle geometry (obstacle pitch, obstacle shape, flow blockage) on the wall temperature and heat transfer coefficient were investigated. Tests were performed for vertical upward flow in a directly heated 8 mm ID tube for a pressure range from 7.69 to 8.36 MPa, a mass flux range from 200 to 1184 kg/m{sup 2} s, and a heat flux range from 1 to 175 kW/m{sup 2}. The results are presented graphically in plots of wall temperature and heat transfer coefficient vs. bulk specific enthalpy of the fluid. The effects of flow parameters and flow obstacle geometry on supercritical heat transfer for both normal and deteriorated heat transfer are discussed. A comparison of the measurements with leading prediction methods for supercritical heat transfer in bare tubes and for spacer effects is also presented. The optimum increase in heat transfer coefficient was found to be for blunt obstacles, having a large flow blockage, and a short obstacle pitch.
A finite volume procedure for fluid flow, heat transfer and solid-body stress analysis
Jagad, P. I.
2018-04-12
A unified cell-centered unstructured mesh finite volume procedure is presented for fluid flow, heat transfer and solid-body stress analysis. An in-house procedure (A. W. Date, Solution of Transport Equations on Unstructured Meshes with Cell-Centered Colocated Variables. Part I: Discretization, International Journal of Heat and Mass Transfer, vol. 48 (6), 1117-1127, 2005) is extended to include the solid-body stress analysis. The transport terms for a cell-face are evaluated in a structured grid-like manner. The Cartesian gradients at the center of each cell-face are evaluated using the coordinate transformation relations. The accuracy of the procedure is demonstrated by solving several benchmark problems involving different boundary conditions, source terms, and types of loading.
A review and development of correlations for base pressure and base heating in supersonic flow
Energy Technology Data Exchange (ETDEWEB)
Lamb, J.P. [Texas Univ., Austin, TX (United States). Dept. of Mechanical Engineering; Oberkampf, W.L. [Sandia National Labs., Albuquerque, NM (United States)
1993-11-01
A comprehensive review of experimental base pressure and base heating data related to supersonic and hypersonic flight vehicles has been completed. Particular attention was paid to free-flight data as well as wind tunnel data for models without rear sting support. Using theoretically based correlation parameters, a series of internally consistent, empirical prediction equations has been developed for planar and axisymmetric geometries (wedges, cones, and cylinders). These equations encompass the speed range from low supersonic to hypersonic flow and laminar and turbulent forebody boundary layers. A wide range of cone and wedge angles and cone bluntness ratios was included in the data base used to develop the correlations. The present investigation also included preliminary studies of the effect of angle of attack and specific-heat ratio of the gas.
Energy Technology Data Exchange (ETDEWEB)
Suphanit, B. [Department of Chemical Engineering, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Pracha Utit Rd., Tungkru, Bangkok 10140 (Thailand)
2010-03-15
The internally heat-integrated distillation column (HIDiC) is a complex column configuration which is more energy efficient than the equivalent conventional column or the distillation column with direct vapor recompression scheme (VRC). Exploiting the heat integration between two diabatic sections operating at different pressures of the HIDiC can greatly enhance the energy performance of the system. On the other hand, the design and optimization of HIDiC is more difficult than those of the conventional distillation column or the column with VRC. The former involves many design parameters, and the most critical one is the pressure ratio between both diabatic sections. However, the heat distribution along the diabatic sections is also another significant factor not yet thoroughly investigated. In this work, two typical distribution schemes, i.e. uniform heat transfer area and uniform heat distribution, are studied by applying a novel approach to solve the simulation problem in Aspen Plus 2004.1. The comparison of both distributing schemes is discussed via two widely-used case studies, namely benzene-toluene separation and propylene-propane splitter. (author)
Two-phase flow heat transfer in nuclear reactor systems
International Nuclear Information System (INIS)
Koncar, Bostjan; Krepper, Eckhard; Bestion, Dominique; Song, Chul-Hwa; Hassan, Yassin A.
2013-01-01
Complete text of publication follows: Heat transfer and phase change phenomena in two-phase flows are often encountered in nuclear reactor systems and are therefore of paramount importance for their optimal design and safe operation.The complex phenomena observed especially during transient operation of nuclear reactor systems necessitate extensive theoretical and experimental investigations. This special issue brings seven research articles of high quality. Though small in number, they cover a wide range of topics, presenting high complexity and diversity of heat transfer phenomena in two-phase flow. In the last decades a vast amount of research has been devoted to theoretical work and computational simulations, yet the experimental work remains indispensable for understanding of two-phase flow phenomena and for model validation purposes. This is reflected also in this issue, where only one article is purely experimental, while three of them deal with theoretical modelling and the remaining three with numerical simulations. The experimental investigation of the critical heat flux (CHF) phenomena by means of photographic study is presented in the paper of J. Park et al. They have used a high-speed camera system to observe the transient boiling characteristics on a thin horizontal cylinder submerged in a pool of water or highly wetting liquid. Experiments show that the initial boiling process is strongly affected by the properties and wettability of the liquid. The authors have stressed the importance of the local scale observation leading to better understanding of the transient CHF phenomena. In the article of G. Espinosa-Paredes et al. a theoretical work concerning the derivation of transport equations for two-phase flow is presented. The author proposes a novel approach based on derivation of nonlocal volume averaged equations which contain new terms related to nonlocal transport effects. These non-local terms act as coupling elements between the phenomena
Energy Technology Data Exchange (ETDEWEB)
Sundberg, Jan; Back, Paer-Erik; Laendell, Maerta; Sundberg, Anders (GEO INNOVA AB, Linkoeping (Sweden))
2009-06-15
This report presents modelling of temperature and temperature gradients in boreholes in Laxemar and Forsmark and fitting to measured temperature data. The modelling is performed with an analytical expression including thermal conductivity, thermal diffusivity, heat flow, internal heat generation and climate events in the past. As a result of the fitting procedure it is also possible to evaluate local heat flow values for the two sites. However, since there is no independent evaluation of the heat flow, uncertainties in for example thermal conductivity, diffusivity and the palaeoclimate temperature curve are transferred into uncertainties in the heat flow. Both for Forsmark and Laxemar, reasonably good fits were achieved between models and data on borehole temperatures. However, none of the general models achieved a fit within the 95% confidence intervals of the measurements. This was achieved in some cases for the additional optimised models. Several of the model parameters are uncertain. A good model fit does not automatically imply that 'correct' values have been used for these parameters. Similar model fits can be expected with different sets of parameter values. The palaeoclimatically corrected surface mean heat flow at Forsmark and Laxemar is suggested to be 61 and 56 mW/m2 respectively. If all uncertainties are combined, including data uncertainties, the total uncertainty in the heat flow determination is judged to be within +12% to -14% for both sites. The corrections for palaeoclimate are quite large and verify the need of site-specific climate descriptions. Estimations of the current ground surface temperature have been made by extrapolations from measured temperature logging. The mean extrapolated ground surface temperature in Forsmark and Laxemar is estimated to 6.5 deg and 7.3 deg C respectively. This is approximately 1.7 deg C higher for Forsmark, and 1.6 deg C higher for Laxemar compared to data in the report SKB-TR-06-23. Comparison with
International Nuclear Information System (INIS)
Sundberg, Jan; Back, Paer-Erik; Laendell, Maerta; Sundberg, Anders
2009-05-01
This report presents modelling of temperature and temperature gradients in boreholes in Laxemar and Forsmark and fitting to measured temperature data. The modelling is performed with an analytical expression including thermal conductivity, thermal diffusivity, heat flow, internal heat generation and climate events in the past. As a result of the fitting procedure it is also possible to evaluate local heat flow values for the two sites. However, since there is no independent evaluation of the heat flow, uncertainties in for example thermal conductivity, diffusivity and the palaeoclimate temperature curve are transferred into uncertainties in the heat flow. Both for Forsmark and Laxemar, reasonably good fits were achieved between models and data on borehole temperatures. However, none of the general models achieved a fit within the 95% confidence intervals of the measurements. This was achieved in some cases for the additional optimised models. Several of the model parameters are uncertain. A good model fit does not automatically imply that 'correct' values have been used for these parameters. Similar model fits can be expected with different sets of parameter values. The palaeoclimatically corrected surface mean heat flow at Forsmark and Laxemar is suggested to be 61 and 56 mW/m 2 respectively. If all uncertainties are combined, including data uncertainties, the total uncertainty in the heat flow determination is judged to be within +12% to -14% for both sites. The corrections for palaeoclimate are quite large and verify the need of site-specific climate descriptions. Estimations of the current ground surface temperature have been made by extrapolations from measured temperature logging. The mean extrapolated ground surface temperature in Forsmark and Laxemar is estimated to 6.5 deg and 7.3 deg C respectively. This is approximately 1.7 deg C higher for Forsmark, and 1.6 deg C higher for Laxemar compared to data in the report SKB-TR-06-23. Comparison with air
SGS Modeling of the Internal Energy Equation in LES of Supersonic Channel Flow
Raghunath, Sriram; Brereton, Giles
2011-11-01
DNS of fully-developed turbulent supersonic channel flows (Reτ = 190) at up to Mach 3 indicate that the turbulent heat fluxes depend only weakly on Mach number, while the viscous dissipation and pressure dilatation do so strongly. Moreover, pressure dilatation makes a significant contribution to the internal energy budget at Mach 3 and higher. The balance between these terms is critical to determining the temperature (and so molecular viscosity) from the internal energy equation and so, in LES of these flows, it is essential to use accurate SGS models for the viscous dissipation and the pressure dilatation. In this talk, we present LES results for supersonic channel flow, using SGS models for these terms that are based on the resolved-scale dilatation, an inverse timescale, and SGS momentum fluxes, which intrinsically represent this Mach number effect.
International Nuclear Information System (INIS)
Moon, S.K.; Chun, S.Y.; Choi, K.Y.; Yang, S.K.
2001-01-01
An experimental study on transient critical heat flux (CHF) under flow coast-down has been performed for water flow in a non-uniformly heated vertical annulus under low flow and a wide range of pressure conditions. The objectives of this study are to systematically investigate the effect of the flow transient on the CHF and to compare the transient CHF with steady state CHF. The transient CHF experiments have been performed for three kinds of flow transient modes based on the coast-down data of the Kori 3/4 nuclear power plant reactor coolant pump. Most of the CHFs occurred in the annular-mist flow regime. Thus, it means that the possible CHF mechanism might be the liquid film dryout in the annular-mist flow regime. For flow transient mode with the smallest flow reduction rate, the time-to-CHF is the largest. At the same inlet subcooling, system pressure and heat flux, the effect of the initial mass flux on the critical mass flux can be negligible. However, the effect of the initial mass flux on the time-to-CHF becomes large as the heat flux decreases. Usually, the critical mass flux is large for slow flow reduction. There is a pressure effect on the ratio of the transient CHF data to steady state CHF data. Some conventional correlations show relatively better CHF prediction results for high system pressure, high quality and slow transient modes than for low system pressure, low quality and fast transient modes. (author)
Internal Flow of Contra-Rotating Small Hydroturbine at Off- Design Flow Rates
SHIGEMITSU, Toru; TAKESHIMA, Yasutoshi; OGAWA, Yuya; FUKUTOMI, Junichiro
2016-11-01
Small hydropower generation is one of important alternative energy, and enormous potential lie in the small hydropower. However, efficiency of small hydroturbines is lower than that of large one. Then, there are demands for small hydroturbines to keep high performance in wide flow rate range. Therefore, we adopted contra-rotating rotors, which can be expected to achieve high performance. In this research, performance of the contra-rotating small hydroturbine with 60mm casing diameter was investigated by an experiment and numerical analysis. Efficiency of the contra-rotating small hydroturbine was high in pico-hydroturbine and high efficiency could be kept in wide flow rate range, however the performance of a rear rotor decreased significantly in partial flow rates. Then, internal flow condition, which was difficult to measure experimentally, was investigated by the numerical flow analysis. Then, a relation between the performance and internal flow condition was considered by the numerical analysis result.
Critical heat flux in a vertical annulus under low upward flow and near atmospheric pressure
International Nuclear Information System (INIS)
Schoesse, T.; Aritomi, Masanori; Lee, Sang-Ryoul; Kataoka, Yoshiaki; Yoshioka, Yuzuru; Chung, Moon-Ki.
1997-01-01
As future boiling water reactors (BWR), concepts of evolutional ABWR (ABWR-IER) and natural circulation BWR (JSBWR) have been investigated in order to reduce their construction cost and simplify their maintenance and inspection procedures. One of the promised features of the design of the evolutional ABWR is to reduce the number of internal pumps and to remove the Motor Generation (MG) sets. These design changes may induce boiling transition in the fuel rods of reactor core during a pump trip transient due to the more rapid flow coastdown characteristics than these of the present design. In addition, the understanding of critical heat flux (CHF) is one important subject to grasp safety margin during the start-up for the natural circulation BWR and to establish the rational start-up procedure in which thermo-hydraulic instabilities can be suppressed. The present study is to clarify CHF characteristics under low velocity conditions. CHF measurements were conducted in a vertical upward annulus channel composed of an inner heated rod and an outer tube made of glass. CHF data were obtained repeatedly under the condition of stable inlet flow to examine statistically their reproducibility. The flow regime was investigated from flow observation and measurement of differential pressure fluctuation. The CHF data are correlated with the flow regime transition. It was clear from the obtained flow pattern and the CHF data that the CHF behavior could be classified into specified regions by the mass flux and inlet subcooling conditions. A CHF correlation was developed and agreed with other researchers' data within acceptable error. (author)
Flow and Heat Transfer in Cooling Microchannels with Phase-Change
Energy Technology Data Exchange (ETDEWEB)
Peles, Y P; Yarin, L P; Hetsroni, G [Technion, Israel Institute of Technology, Haifa (Israel) Faculty of Engineering
1998-05-19
The subject of the present work is the parametrical investigation of hydrodynamic and thermal characteristics of laminar flow with phase-change in a heating microchannels. The study is based on the quasi-one-dimensional model of non-isothermal capillary flow. This model takes into account the evolution of flow, heating and evaporation of the liquid, as well as the influence of capillary, inertia, friction and gravity forces. The effect of various parameters (sizes of microchannel, initial temperature of cooling liquid, wall heat flux etc.) on hydrodynamic and thermal structures of the flow, the length of heating, evaporation and superheat regions is studied. Thc specific features of the phenomena is discussed.
Flow and Heat Transfer in Cooling Microchannels with Phase-Change
International Nuclear Information System (INIS)
Peles, Y.P.; Yarin, L.P.; Hetsroni, G.
1998-01-01
The subject of the present work is the parametrical investigation of hydrodynamic and thermal characteristics of laminar flow with phase-change in a heating microchannels. The study is based on the quasi-one-dimensional model of non-isothermal capillary flow. This model takes into account the evolution of flow, heating and evaporation of the liquid, as well as the influence of capillary, inertia, friction and gravity forces. The effect of various parameters (sizes of microchannel, initial temperature of cooling liquid, wall heat flux etc.) on hydrodynamic and thermal structures of the flow, the length of heating, evaporation and superheat regions is studied. Thc specific features of the phenomena is discussed
Numerical Heat Transfer Prediction for Laminar Flow in a Circular Pipe with a 90° Bend
Patro, Pandaba; Rout, Ani; Barik, Ashok
2018-06-01
Laminar air flow in a 90° bend has been studied numerically to investigate convective heat transfer, which is of practical relevance to electronic systems and refrigeration piping layout. CFD simulations are performed for Reynolds number in the range 200 to 1000 at different bend radius ratios (5, 10 and 20). The heat transfer characteristics are found to be enhanced in the curved pipe compared to a straight pipe, which are subjected to the same flow rate. The curvature and buoyancy effectively increase heat transfer in viscous laminar flows. The correlation between the flow structure and the heat transfer is found to be strong.
Analysis of Turbulence Models in a Cross Flow Pin Fin Micro-Heat Exchanger
National Research Council Canada - National Science Library
Lind, Eric
2002-01-01
... of their physical significance to the complex flow environment of a pin fin, cross flow, micro-heat exchanger. Applications of this research include cooling of turbine blades and of closely spaced electronics.
Cao, Guoliang; Han, Dongmei; Currell, Matthew J.; Zheng, Chunmiao
2016-09-01
Groundwater flow in deep sedimentary basins results from complex evolution processes on geological timescales. Groundwater flow systems conceptualized according to topography and/or groundwater table configuration generally assume a near-equilibrium state with the modern landscape. However, the time to reach such a steady state, and more generally the timescales of groundwater flow system evolution are key considerations for large sedimentary basins. This is true in the North China Basin (NCB), which has been studied for many years due to its importance as a groundwater supply. Despite many years of study, there remain contradictions between the generally accepted conceptual model of regional flow, and environmental tracer data. We seek to reconcile these contractions by conducting simulations of groundwater flow, age and heat transport in a three dimensional model, using an alternative conceptual model, based on geological, thermal, isotope and historical data. We infer flow patterns under modern hydraulic conditions using this new model and present the theoretical maximum groundwater ages under such a flow regime. The model results show that in contrast to previously accepted conceptualizations, most groundwater is discharged in the vicinity of the break-in-slope of topography at the boundary between the piedmont and central plain. Groundwater discharge to the ocean is in contrast small, and in general there are low rates of active flow in the eastern parts of the basin below the central and coastal plain. This conceptualization is more compatible with geochemical and geothermal data than the previous model. Simulated maximum groundwater ages of ∼1 Myrs below the central and coastal plain indicate that residual groundwater may be retained in the deep parts of the basin since being recharged during the last glacial period or earlier. The groundwater flow system has therefore probably not reached a new equilibrium state with modern-day hydraulic conditions. The
Analysis of diabatic flow modification in the internal boundary layer
DEFF Research Database (Denmark)
Floors, Rogier; Gryning, Sven-Erik; Pena Diaz, Alfredo
2011-01-01
Measurements at two meteorological masts in Denmark, Horns Rev in the sea and Høvsøre near the coastline on land, are used to analyze the behaviour of the flow after a smooth-to-rough change in surface conditions. The study shows that the wind profile within the internal boundary layer is control......Measurements at two meteorological masts in Denmark, Horns Rev in the sea and Høvsøre near the coastline on land, are used to analyze the behaviour of the flow after a smooth-to-rough change in surface conditions. The study shows that the wind profile within the internal boundary layer...
Aero-Heating of Shallow Cavities in Hypersonic Freestream Flow
Everhart, Joel L.; Berger, Karen T.; Merski, N. R., Jr.; Woods, William A.; Hollingsworth, Kevin E.; Hyatt, Andrew; Prabhu, Ramadas K.
2010-01-01
The purpose of these experiments and analysis was to augment the heating database and tools used for assessment of impact-induced shallow-cavity damage to the thermal protection system of the Space Shuttle Orbiter. The effect of length and depth on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These rapid-response experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated immediately prior to the launch of STS-114, the initial flight in the Space Shuttle Return-To-Flight Program, and continued during the first week of the mission. Previously-designed and numerically-characterized blunted-nose baseline flat plates were used as the test surfaces. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process and the two-dimensional flow assumptions used for the data analysis. The experimental boundary layer state conditions were inferred using the measured heating distributions on a no-cavity test article. Two test plates were developed, each containing 4 equally-spaced spanwise-distributed cavities. The first test plate contained cavities with a constant length-to-depth ratio of 8 with design point depth-to-boundary-layer-thickness ratios of 0.1, 0.2, 0.35, and 0.5. The second test plate contained cavities with a constant design point depth-to-boundary-layer-thickness ratio of 0.35 with length-to-depth ratios of 8, 12, 16, and 20. Cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary results indicate that the floor-averaged Bump Factor (local heating rate nondimensionalized by upstream reference) at the tested conditions is approximately 0.3 with a standard deviation of 0.04 for laminar-in/laminar-out conditions when the cavity length-to-boundary-layer thickness is between 2.5 and 10 and for
Thermosyphon analysis of a repository: A simplified model for vapor flow and heat transfer
International Nuclear Information System (INIS)
Manteufel, R.D.; Powell, M.W.
1994-01-01
A simplified model is developed for thermally-driven buoyant gas flow in an unsaturated repository such as that anticipated at Yucca Mountain. Based on a simplified thermosyphon model, the strength of buoyant gas flow is related to key thermal-hydraulic parameters (e.g., bulk permeability and maximum repository temperature). The effects of buoyant gas flow on vapor flow and heat transport near the repository horizon are assessed, namely: (i) the strength of buoyant flow through the repository, (ii) the effect of buoyant flow on vapor transfer, and (iii) the effect of buoyant flow on heat transfer
Directory of Open Access Journals (Sweden)
B. R. Rout
2013-01-01
Full Text Available This paper aims to investigate the influence of chemical reaction and the combined effects of internal heat generation and a convective boundary condition on the laminar boundary layer MHD heat and mass transfer flow over a moving vertical flat plate. The lower surface of the plate is in contact with a hot fluid while the stream of cold fluid flows over the upper surface with heat source and chemical reaction. The basic equations governing the flow, heat transfer, and concentration are reduced to a set of ordinary differential equations by using appropriate transformation for variables and solved numerically by Runge-Kutta fourth-order integration scheme in association with shooting method. The effects of physical parameters on the velocity, temperature, and concentration profiles are illustrated graphically. A table recording the values of skin friction, heat transfer, and mass transfer at the plate is also presented. The discussion focuses on the physical interpretation of the results as well as their comparison with previous studies which shows good agreement as a special case of the problem.
Directory of Open Access Journals (Sweden)
I. G. Zorina
2016-01-01
Full Text Available To use the renewable power sources such as solar, wind, biogas, and others is complicated because of their sporadic supply. Thus and so, energy accumulation makes the user independent on the operating mode of the power source.Some of the heat accumulation methods can be realized with accumulators using phase transitions and based on the heat storage materials that change their state of aggregation during storage and rejection of thermal energy. In comparison with the gravel or liquid heat accumulators these devices are compact and provide high density of stored energy. To intensify heat exchange in such devices, are used highly heat-conductive metallic inсlusions of different shape, capsular laying or heat storage materials placed in the form of inserts, extended heat exchange surfaces, etc.Heat transfer of accumulator using phase transitions is calculated through solving a nonlinear Stefan problem. For calculation, are, usually, used various sufficiently time-consuming methods.The paper presents a heat transfer calculation when changing the aggregation state of substance. Its recommendation is to use the analytical dependences that allow calculation of heat exchange characteristics with charging phase transition accumulators of a capsular type in which a heat storage material is in cross-inserts.It is assumed that heat transfer in the coolant flow is one-dimensional, thermal and physical properties of heat storage material and coolant are constant, and heat transfer in the accumulator using phase transitions is quasi-stationary.
Study on drop pressure and flow distribution of double-tube heat exchanger
International Nuclear Information System (INIS)
Liu Junqiang; Chen Minghui; Hu Yumin; Li Rizhu; Kong Dechun; Zhang Weijie
2007-01-01
The parallel connection channel pressure drop characters of the double-tube bundle heat exchange were experimentally investigated in this paper in order to find out how the flow of the heat exchanger is distributed and then to optimize the structure of heat exchanger according to the flow distribution. A double-tube bundle heat exchanger was built according to the similarity criteria. The experiment system was also built to test the optimization of the heat exchanger. The experiment results reveal that the calculating model is reliable and decreasing pipe space to optimize the heat exchanger is reasonable. (authors)
Molten corium concrete interaction: investigation of heat transfer in two-phase flow
International Nuclear Information System (INIS)
Amizic, Milan
2014-01-01
In the context of severe accident research for the second and the third generation of nuclear power plants, there are still open issues concerning some aspects of the concrete cavity ablation during the molten corium - concrete interaction (MCCI). The determination of heat transfer along the interfacial region between the molten corium pool and the ablating basemat concrete is crucial for the assessment of concrete ablation progression and eventually the basemat melt through. For the purpose of experimental investigation of thermal hydraulics inside a liquid pool agitated by gas bubbles, the CLARA project has been launched. The CLARA experiments are performed using simulant materials and they reveal the influence of superficial gas velocity, liquid viscosity and pool geometry on the heat transfer coefficient between the internally heated liquid pool and vertical and horizontal pool walls maintained at uniform temperature. The first test campaign has been conducted with the small pool configuration (50 cm * 25 cm * 25 cm). The tests have been performed with liquids covering a wide range of dynamic viscosity from approximately 1 mPa s to 10000 mPa s and the superficial gas velocity is varied up to 8 cm/s. This thesis comprises a brief description of MCCI phenomenology, literature reviews on the existing heat transfer correlations for two phase flow and the void fraction, a description of CLARA setup, experimental results and their interpretation. The experimental results are compared with existing models and some new models for the assessment of heat transfer coefficient in two-phase flow. (author) [fr
CFD simulation of flow and heat transfer in Canadian SCWR bundles
International Nuclear Information System (INIS)
Podila, K.; Rao, Y.F.
2014-01-01
Within the Generation-IV (Gen-IV) International Forum, Atomic Energy of Canada Limited (AECL) is leading the effort in developing a conceptual design for the Canadian supercritical water-cooled reactor (SCWR). AECL proposed a new fuel bundle design with two rings of fuel elements placed between central flow tube and the pressure tube. In line with the scope of the conceptual design, the objective of the present CFD work is to aid in developing a bundle heat transfer correlation for the Canadian SCWR fuel bundle design. This paper presents results from an ongoing effort in determining the conditions favorable for possible occurrence of heat transfer deterioration (HTD) in the supercritical bundle flows. In the current investigation, a bare-rod bundle geometry was tested for the proposed fuel bundle design at 23.5, 25 and 28 MPa using STAR-CCM+ CFD code. Taking advantage of the design symmetry of the fuel bundle, only 1/32 of the computational domain was simulated. The SST k-ω turbulence model along with y + <1 was used in the simulations. For lower mass flow simulations, the increase of inlet temperature and operational pressure was found effective in reducing the occurrence of HTD. For higher mass flow simulations, normal heat transfer behaviour was observed except for the lower pressure range (23.5MPa). Ultimately, the goal of this study is to aid the development of a criterion for the onset of HTD in the proposed SCWR bundles, which is planned in the next phase of the project. (author)
Analytical Simulation of Flow and Heat Transfer of Two-Phase Nanofluid (Stratified Flow Regime
Directory of Open Access Journals (Sweden)
Mohammad Abbasi
2014-01-01
Full Text Available Nanofluids have evoked immense interest from researchers all around the globe due to their numerous potential benefits and applications in important fields such as cooling electronic parts, cooling car engines and nuclear reactors. An analytical study of fluid flow of in-tube stratified regime of two-phase nanofluid has been carried out for CuO, Al2O2, TiO3, and Au as applied nanoparticles in water as the base liquid. Liquid film thickness, convective heat transfer coefficient, and dryout length have been calculated. Among the considered nano particles, Al2O3 and TiO2 because of providing more amounts of heat transfer along with longer lengths of dryout found as the most appropriate nanoparticles to achieve cooling objectives.
2nd International Conference on Multiphase Flow - ICMF '95
Fukano, T; Bataille, Jean
1995-01-01
There is increasing world-wide interest in obtaining an understanding of various multiphase flow phenomena and problems in terms of a common language of multiphase flow. This volume contains state-of-the-art papers which have been contributed from all over the world by experts working on all aspects of multiphase flows. The volume also highlights international technology-sharing in the fields of energy, environment and public health, in order to create a brighter and sustainable future for man and for all life in the next century. It is intended that this volume will serve as a major source of
Geometric optimization of cross-flow heat exchanger based on dynamic controllability
Directory of Open Access Journals (Sweden)
Alotaibi Sorour
2008-01-01
Full Text Available The operation of heat exchangers and other thermal equipments in the face of variable loads is usually controlled by manipulating inlet fluid temperatures or mass flow rates, where the controlled variable is usually one of the output temperatures. The aim of this work is to optimize the geometry of a tube with internal flow of water and an external cross-flow of air, based on its controllability characteristics. Controllability is a useful concept both from theoretical and practical perspective since it tells us if a particular output can be controlled by a particular input. This concept can also provide us with information about the easiest operating condition to control a particular output. A transient model of a tube in cross-flow is developed, where an implicit formulation is used for transient numerical solutions. The aspect ratio of the tube is optimized, subject to volume constraints, based on the optimum operation in terms of controllability. The reported optimized aspect ratio, water mass flow rate and controllability are studied for deferent external properties of the tube.
International Conference on Instability and Control of Massively Separated Flows
Soria, Julio
2015-01-01
This book contains the outcome of the international meeting on instability, control and noise generated by massive flow separation that was organized at the Monash Center, in Prato, Italy, September 4-6, 2013. The meeting served as the final review of the EU-FP7 Instability and Control of Massively Separated Flows Marie Curie travel grant and was supported by the European Office of Aerospace Research and Development. Fifty leading specialists from twelve countries reviewed the progress made since the 50s of the last century and discussed modern analysis techniques, advanced experimental flow diagnostics, and recent developments in active flow control techniques from the incompressible to the hypersonic regime. Applications involving massive flow separation and associated instability and noise generation mechanisms of interest to the aeronautical, naval and automotive industries have been addressed from a theoretical, numerical or experimental point of view, making this book a unique source containing the stat...
Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.
Zhou, Zhanru; Fang, Xiande; Li, Dingkun
2013-01-01
The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.
Heat transfer to a particle exposed to a rarefield ionized-gas flow
International Nuclear Information System (INIS)
Chen, X.; He, P.
1986-01-01
Analytical results are presented concerning the heat transfer to a spherical particle exposed to a high temperature, ionized- gas flow for the extreme case of free-molecule flow regime. It has been shown that the presence of relative velocity between the particle and the ionized gas reduces the floating potential on the particle, enhances the heat flux and causes appreciably non-uniform distribution of the local heat flux. Pronounced difference is found between metallic and non-metallic particles in the floating potential and the local heat flux distributions, in particular for the case with high gas-flow temperature. Relative contribution of atoms to the total heat flux is dominant for the case of low gas-flow temperature, while the heat flux is mainly caused by ions and electrons for the case of high gas-flow temperature
Plate heat exchanger - inertia flywheel performance in loss of flow transient
International Nuclear Information System (INIS)
Abou-El-Maaty, Talal; Abd-El-Hady, Amr
2009-01-01
One of the most versatile types of heat exchangers used is the plate heat exchanger. It has principal advantages over other heat exchangers in that plates can be added and/or removed easily in order to change the area available for heat transfer and therefore its overall performance. The cooling systems of Egypt's second research reactor (ETRR 2) use this type of heat exchanger for cooling purposes in its primary core cooling and pool cooling systems. In addition to the change in the number of heat exchanger cooling channels, the effect of changing the amount of mass flow rate on the heat exchanger performance is an important issues in this study. The inertia flywheel mounted on the primary core cooling system pump with the plate heat exchanger plays an important role in the case of loss of flow transients. The PARET code is used to simulate the effect of loss of flow transients on the reactor core. Hence, the core outlet temperature with the pump-flywheel flow coast down is fed into the plate heat exchanger model developed to estimate the total energy transferred to the cooling tower, the primary side heat exchanger temperature variation, the transmitted heat exchanger power, and the heat exchanger effectiveness. In addition, the pressure drop in both, the primary side and secondary side of the plate heat exchanger is calculated in all simulated transients because their values have limits beyond which the heat exchanger is useless. (orig.)
International Nuclear Information System (INIS)
Hussein, H.M.S.
2007-01-01
In this work, a wickless heat pipes flat plate solar collector with a cross flow heat exchanger was investigated theoretically and experimentally under the meteorological conditions of Cairo, Egypt. The author's earlier simulation program of wickless heat pipes flat plate solar water heaters was modified to be valid for the present type of wickless heat pipes solar collector by including the solution of the dimensionless governing equations of the present analysis. For verifying the modified simulation program, a wickless heat pipes flat plate solar collector with a cross flow heat exchanger was designed, constructed, and tested at different meteorological conditions and operating parameters. These parameters include different cooling water mass flow rates and different inlet cooling water temperatures. The comparison between the experimental results and their corresponding simulated ones showed considerable agreement. Under different climatic conditions, the experimental and theoretical results showed that the optimal mass flow rate is very close to the ASHRAE standard mass flow rate for testing conventional flat plate solar collectors. Also, the experimental and theoretical results indicated that the number of wickless heat pipes has a significant effect on the collector efficiency
Dry-out heat fluxes of falling film and low-mass flux upward-flow in heated tubes
International Nuclear Information System (INIS)
Koizumi, Yasuo; Ueda, Tatsuhiro; Matsuo, Teruyuki; Miyota, Yukio
1998-01-01
Dry-out heat fluxes were investigated experimentally for a film flow falling down on the inner surface of vertical heated-tubes and for a low mass flux forced-upward flow in the tubes using R 113. This work followed the study on those for a two-phase natural circulation system. For the falling film boiling, flow state observation tests were also performed, where dry-patches appearing and disappearing repeatedly were observed near the exit end of the heated section at the dry-out heat flux conditions. Relation between the dry-out heat flux and the liquid film flow rate is analyzed. The dry-out heat fluxes of the low mass flux upflow are expressed well by the correlation proposed in the previous work. The relation for the falling film boiling shows a similar trend to that for the upflow boiling, however, the dry-out heat fluxes of the falling film are much lower, approximately one third, than those of the upward flow. (author)
Numerical Investigation of the Internal Flow in a Banki Turbine
Directory of Open Access Journals (Sweden)
Jesús De Andrade
2011-01-01
Full Text Available The paper refers to the numerical analysis of the internal flow in a hydraulic cross-flow turbine type Banki. A 3D-CFD steady state flow simulation has been performed using ANSYS CFX codes. The simulation includes nozzle, runner, shaft, and casing. The turbine has a specific speed of 63 (metric units, an outside runner diameter of 294 mm. Simulations were carried out using a water-air free surface model and k-ε turbulence model. The objectives of this study were to analyze the velocity and pressure fields of the cross-flow within the runner and to characterize its performance for different runner speeds. Absolute flow velocity angles are obtained at runner entrance for simulations with and without the runner. Flow recirculation in the runner interblade passages and shocks of the internal cross-flow cause considerable hydraulic losses by which the efficiency of the turbine decreases significantly. The CFD simulations results were compared with experimental data and were consistent with global performance parameters.
Hybrid continuum–molecular modelling of multiscale internal gas flows
International Nuclear Information System (INIS)
Patronis, Alexander; Lockerby, Duncan A.; Borg, Matthew K.; Reese, Jason M.
2013-01-01
We develop and apply an efficient multiscale method for simulating a large class of low-speed internal rarefied gas flows. The method is an extension of the hybrid atomistic–continuum approach proposed by Borg et al. (2013) [28] for the simulation of micro/nano flows of high-aspect ratio. The major new extensions are: (1) incorporation of fluid compressibility; (2) implementation using the direct simulation Monte Carlo (DSMC) method for dilute rarefied gas flows, and (3) application to a broader range of geometries, including periodic, non-periodic, pressure-driven, gravity-driven and shear-driven internal flows. The multiscale method is applied to micro-scale gas flows through a periodic converging–diverging channel (driven by an external acceleration) and a non-periodic channel with a bend (driven by a pressure difference), as well as the flow between two eccentric cylinders (with the inner rotating relative to the outer). In all these cases there exists a wide variation of Knudsen number within the geometries, as well as substantial compressibility despite the Mach number being very low. For validation purposes, our multiscale simulation results are compared to those obtained from full-scale DSMC simulations: very close agreement is obtained in all cases for all flow variables considered. Our multiscale simulation is an order of magnitude more computationally efficient than the full-scale DSMC for the first and second test cases, and two orders of magnitude more efficient for the third case
Numerical Simulation of a Coolant Flow and Heat Transfer in a Pebble Bed Reactor
International Nuclear Information System (INIS)
In, Wang-Kee; Kim, Min-Hwan; Lee, Won-Jae
2008-01-01
Pebble Bed Reactor(PBR) is one of the very high temperature gas cooled reactors(VHTR) which have been reviewed in the Generation IV International Forum as potential sources for future energy needs, particularly for a hydrogen production. The pebble bed modular reactor(PBMR) exhibits inherent safety features due to the low power density and the large amount of graphite present in the core. PBR uses coated fuel particles(TRISO) embedded in spherical graphite fuel pebbles. The fuel pebbles flow down through the PBR core during a reactor operation and the coolant flows around randomly distributed spheres. For the reliable operation and the safety of the PBR, it is important to understand the coolant flow structure and the fuel pebble temperature in the PBR core. There have been few experimental and numerical studies to investigate the fluid and heat transfer phenomena in the PBR core. The objective of this paper is to predict the fluid and heat transfer in the PBR core. The computational fluid dynamics (CFD) code, STAR-CCM+(V2.08) is used to perform the CFD analysis using the design data for the PBMR400
Turbulent flow and heat transfer in channels with combined rough and smooth surfaces
International Nuclear Information System (INIS)
Aytekin, A.
1978-01-01
A two-part experimental investigation is reported on the effects of transverse square rib roughening on fluid flow and heat transfer in channels with uniform and non-uniform boundary conditions. The first part of the experimental programme consisted of providing detailed measurements of mean and basic turbulent characteristics of fully developed flow in two rectangular ducts of aspect ratios 1.63 and 3.0. In each duct only one wall was roughened. In channels having low aspect ratios secondary flows play an important part in momentum transfer, and an interpretation of their effect on the measured Reynolds shear stress distribution has been attempted. In the second part of the experimental programme mean velocity and temperature profiles, friction factors and Stanton numbers were measured in an internally roughened pipe and annuli composed of a rough inner rod and either a smooth or a rough outer pipe. Heating was always applied on the outer surface. In all the geometries the mean velocities near the rough walls were found to be represented by logarithmic straight lines. The gradients of these lines were independent of Reynolds number but differed for various geometries. The mean temperature profiles, measured in the rough pipe and the fully rough annulus, showed that these could also be represented by logarithmic straight lines, but the slopes of these profiles were markedly different from those of the velocity profiles. (author)
E.Hemalatha; N. Bhaskar Reddy
2015-01-01
This paper analyzes the radiation and chemical reaction effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of internal heat generation and convective boundary condition. It is assumed that lower surface of the plate is in contact with a hot fluid while a stream of cold fluid flows steadily over the upper surface with a heat source that decays exponentially. The Rosseland approximation is used to desc...
International Nuclear Information System (INIS)
Kerns, J.A.; Wong, R.L.
1989-01-01
The toroidal field (TF) coils in the International Thermonuclear Experimental Reactor (ITER) will operate with varying heat loads generated by ac losses and nuclear heating. The total heat load is estimated to be 2 kW per TF coil under normal operation and can be higher for different operating scenarios. Ac losses are caused by ramping the poloidal field (PF) for plasma initiation, burn, and shutdown; nuclear heating results from neutrons that penetrate into the coil past the shield. Present methods to reduce or eliminate these losses lead to larger and more expensive machines, which are unacceptable with today's budget constraints. A suitable solution is to design superconductors that operate with high heat loads. The cable-in-conduit conductor (CICC) can operate with high heat loads. One CICC design is analyzed for its thermal performance using two computer codes developed at LLNL. One code calculates the steady state flow conditions along the flow path, while the other calculates the transient conditions in the flow. We have used these codes to analyze the superconductor performance during the burn phase of the ITER plasma. The results of these analyses give insight to the choice of flow rate on superconductor performance. 4 refs., 5 figs
Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E
2014-12-01
We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.
Energy Technology Data Exchange (ETDEWEB)
Surducan, E.; Surducan, V.; Neamtu, C., E-mail: camelia.neamtu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies (INCDTIM), 67-103 Donat St., 400293, Cluj‑Napoca (Romania); Limare, A.; Di Giuseppe, E. [Institut de Physique du Globe de Paris (IPGP), Univ. Paris Diderot, UMR CNRS 7154, 1 rue Jussieu, 75005, Paris (France)
2014-12-15
We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm{sup 3} convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.
A study on the flow induced vibration in two phase flow under heating and non-heating conditions
International Nuclear Information System (INIS)
Kim, Dae Hun
2007-02-01
Critical heat flux (CHF) enhancement devices, like a spacer grid with mixing vane, cause flow-induced vibration (FIV) due to turbulence made by structural resistance. CHF enhancement and FIV reduction are usually studied separately. The main purpose of this article is to investigate the relationship between CHF and FIV. Information of flow-induced vibration due to wire coil design, is experimentally presented in this study by detecting flow-induced vibration under the two-phase flow condition with wire coil inserts. CHF experiments were performed in an upward vertical annulus tube under controlled vibration conditions to determine the effect of vibration on CHF. FIV was measured in an upward vertical tube with various wire coil inserts using air-water as flow material. CHF experiments were performed at one atmosphere with mechanically controlled vibration. A quartz tube (inner diameter of 17 mm, thickness of 2mm and length of 0.72 m) was used for outer tube and a SUS-304 tube (outer diameter of 6.35 mm, thickness of 0.89 mm and length of 0.7 m) was used for the inner heater. Vibration of the heater tube with an amplitude range of 0.1 mm to 0.5 mm and a frequency range of 10 Hz to 50 Hz was carried out at a mass flux of 115 kg/m 2 s and 215 kg/m 2 s. CHF was enhanced by vibration with a maximum ratio of 16.4 %. CHF was increased with increased amplitude and quality. The CHF correlation was developed with R (coefficient of correlation) of 0.903. FIV measuring experiments were performed at one atmosphere by changing the inserted wire coil type. An acrylic tube was used for the test section with inner diameter of 25 mm, thickness of 10 mm and length of 0.5 m. Four types of wire coil, which have a thickness of between 2 mm and 3 mm and pitch length of between 25 mm and 50 mm, were used. FIV and dynamic pressure were detected in water mass flux range of 100 ∼ 3060 kg/m 2 s and air mass flux range of 5.02 ∼ 60.3 kg/m 2 s. Vibration increased along with mass flux and
International Nuclear Information System (INIS)
French, R.T.
1975-08-01
Selected experimental data pertinent to piping heat transfer, transient fluid flow regimes, and steam generator heat transfer obtained during the Semiscale Mod-1 isothermal blowdown test series (Test Series 1) are analyzed. The tests in this first test series were designed to provide counterparts to the LOFT nonnuclear experiments. The data from the Semiscale Mod-1 intact and broken loop piping are evaluated to determine the surface heat flux and average heat transfer coefficients effective during the blowdown transient and compared with well known heat transfer correlations used in the RELAP4 computer program. Flow regimes in horizontal pipe sections are calculated and compared with data obtained from horizontal and vertical densitometers and with an existing steady state flow map. Effects of steam generator heat transfer are evaluated quantitatively and qualitatively. The Semiscale Mod-1 data and the analysis presented in this report are valuable for evaluating the adequacy and improving the predictive capability of analytical models developed to predict system response to piping heat transfer, piping flow regimes, and steam generator heat transfer during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). 16 references. (auth)
Flow Patterns and Thermal Drag in a One-Dimensional Inviscid Channel with Heating or Cooling
Institute of Scientific and Technical Information of China (English)
无
1993-01-01
In this paper investigations on the flow patterns and the thermal drag phenomenon in one -dimensional inviscid channel flow with heating or cooling are described and discussed:expressions of flow rate ratio and thermal drag coefficient for different flow patterns and its physical mechanism are presented.
The flow distribution in the parallel tubes of the cavity receiver under variable heat flux
International Nuclear Information System (INIS)
Hao, Yun; Wang, Yueshe; Hu, Tian
2016-01-01
Highlights: • An experimental loop is built to find the flow distribution in the parallel tubes. • With the concentration of heat flux, two-phase flow makes distribution more uneven. • The total flow rate is chosen appropriately for a wider heat flux distribution. • A suitable system pressure is essential for the optimization of flow distribution. - Abstract: As an optical component of tower solar thermal power station, the heliostat mirror reflects sunlight to one point of the heated surface in the solar cavity receiver, called as one-point focusing system. The radiation heat flux concentrated in the cavity receiver is always non-uniform temporally and spatially, which may lead to extremely local over-heat on the receiver evaporation panels. In this paper, an electrical heated evaporating experimental loop, including five parallel vertical tubes, is set up to evaluate the hydrodynamic characteristics of evaporation panels in a solar cavity receiver under various non-uniform heat flux. The influence of the heat flux concentration ratio, total flow rate, and system pressure on the flow distribution of parallel tubes is discussed. It is found that the flow distribution becomes significantly worse with the increase of heat flux and concentration ratio; and as the system pressure decreased, the flow distribution is improved. It is extremely important to obtain these interesting findings for the safe and stable operation of solar cavity receiver, and can also provide valuable references for the design and optimization of operating parameters solar tower power station system.
Heat flow at the proposed Appalachian Ultradeep Core Hole (ADCOH) Site: Tectonic implications
Costain, John K.; Decker, Edward R.
The heat flow in northwestern South Carolina at the Appalachian Ultradeep Core Hole (ADCOH) site area is approximately 55 mW/m². This data supplements other data to the east in the Piedmont and Atlantic Coastal Plain provinces where heat flows > 55 mW/m² are characteristic of post- and late-synmetamorphic granitoids. Piedmont heat flow and heat generation data for granites, metagranites, and one Slate Belt site, in a zone approximately parallel to major structural Appalachian trends, define a linear relation. Tectonic truncation of heat-producing crust at a depth of about 8 km (a depth equal to the slope of the heat flow-heat production line) is proposed to explain the linear relation. Using the value of reduced heat flow estimated from this empirical relation, and assuming thicknesses of heat-producing crust defined by new ADCOH seismic data, the heat flow and heat production at the ADCOH site are consistent with a depth to the base of the Inner Piedmont crystalline allochthon of about 5.5 km. Seismic data at the ADCOH site confirm that the Inner Piedmont is tectonically truncated at about 5.5 km by the Blue Ridge master decollement. Temperatures at 10 km at the ADCOH site are predicted to be less than 200 °C.
Ventilation and internal structure effects on naturally induced flows in a static aircraft wing
International Nuclear Information System (INIS)
Moore, Daithi; Newport, David; Egan, Vanessa; Lacarac, Vesna
2012-01-01
The ventilation performance within an aircraft wing leading edge is investigated for a number of enclosure and ventilation configurations. The natural convection regime present is found to be highly sensitive to enclosure conditions, particularly the introduction of a partition. The presence of a partition reduced the overall heat exhausted from the cavity by up to 60%. The optimum ventilation strategy is also changed from a forward biased vent orientation (found for the unpartitioned case), to one where both the rear and front vents within the enclosure had the same open area. Cylinder plume effects dominate within the enclosure and were the main driver of the convective regime, with steady-state enclosure conditions highly dependent upon cylinder placement and plume orientation. An externally heated enclosure with internal heat source, combined with ventilation and an internal structure produced a complex natural convection regime which is sensitive to enclosure conditions. Hence an adequate knowledge of such conditions is necessary in order to fully appreciate the convective regime. - Highlights: → Optimum ventilation strategy changed between unpartitioned and partitioned cases. → Flow path and plume orientation are important to consider when analysing ventilation. → Bleed duct placement significantly alters flow path and temperature distribution. → Enclosure partitioning reduced heat exhaustion by 60%.
Internally heated mantle convection and the thermal and degassing history of the earth
Williams, David R.; Pan, Vivian
1992-01-01
An internally heated model of parameterized whole mantle convection with viscosity dependent on temperature and volatile content is examined. The model is run for 4l6 Gyr, and temperature, heat flow, degassing and regassing rates, stress, and viscosity are calculated. A nominal case is established which shows good agreement with accepted mantle values. The effects of changing various parameters are also tested. All cases show rapid cooling early in the planet's history and strong self-regulation of viscosity due to the temperature and volatile-content dependence. The effects of weakly stress-dependent viscosity are examined within the bounds of this model and are found to be small. Mantle water is typically outgassed rapidly to reach an equilibrium concentration on a time scale of less than 200 Myr for almost all models, the main exception being for models which start out with temperatures well below the melting temperature.
THEORETICAL AND EXPERIMENTAL ANALYSIS OF A CROSS-FLOW HEAT EXCHANGER
Directory of Open Access Journals (Sweden)
R. Tuğrul OĞULATA
1996-03-01
Full Text Available In this study, cross-flow plate type heat exchanger has been investigated because of its effective use in waste heat recovery systems. For this purpose, a heat regain system has been investigated and manufactured in laboratory conditions. Manufactured heat exchanger has been tested with an applicable experimental set up and temperatures, velocity of the air and the pressure losses occuring in the system have been measured and the efficiency of the system has been determined. The irreversibility of heat exchanger has been taken into consideration while the design of heat exchanger is being performed. So minimum entropy generation number has been analysied with respect to second law of thermodynamics in cross-flow heat exchanger. The minimum entropy generation number depends on parameters called optimum flow path length, dimensionless mass velocity and dimensionless heat transfer area. Variations of entropy generation number with these parameters have been analysied and introduced their graphics with their comments.
International Nuclear Information System (INIS)
Hossain, Md. Anwar; Rees, D.A.S.
2002-05-01
The effect of surface tension on unsteady laminar natural convection flow of a viscous incompressible fluid in a rectangle enclosure with internal heat generation and in presence of a uniform transverse magnetic field acting in the direction normal to the gravity has been investigated. The top horizontal surface of the rectangular cavity is assumed to be free and the bottom ones insulated; whereas the left vertical wall is cold and the right one is uniformly hot. The equations are non-dimensionalized and solved numerically by an upwind finite difference method together with a successive over-relaxation (SOR) technique. The effects of heat generation together with the combined effects of the magnetic field and the surface tension are presented graphically in terms of isotherms, streamlines and velocity vector plots. The effects of varying the physical parameters on the rate of heat transfer from the heated surface of the enclosure are also depicted. The fluid here has Prandtl number Pr=0.054 while the value of the Grashof number is 2x10 4 . (author)
Gas flow characteristics of a time modulated APPJ: the effect of gas heating on flow dynamics
International Nuclear Information System (INIS)
Zhang, S; Sobota, A; Van Veldhuizen, E M; Bruggeman, P J
2015-01-01
This work investigates the flow dynamics of a radio-frequency (RF) non-equilibrium argon atmospheric pressure plasma jet. The RF power is at a frequency of 50 Hz or 20 kHz. Combined flow pattern visualizations (obtained by shadowgraphy) and gas temperature distributions (obtained by Rayleigh scattering) are used to study the formation of transient vortex structures in initial flow field shortly after the plasma is switched on and off in the case of 50 Hz modulation. The transient vortex structures correlate well with observed temperature differences. Experimental results of the fast modulated (20 kHz) plasma jet that does not induce changes of the gas temperature are also presented. The latter result suggests that momentum transfer by ions does not have dominant effect on the flow pattern close to the tube. It is argued that the increased gas temperature and corresponding gas velocity increase at the tube exit due to the plasma heating increases the admixing of surrounding air and reduces the effective potential core length. With increasing plasma power a reduction of the effective potential core length is observed with a minimum length for 5.6 W after which the length extends again. Possible mechanisms related to viscosity effects and ionic momentum transfer are discussed. (paper)
International Nuclear Information System (INIS)
Raisson, Claude
1968-01-01
This research thesis reports the experimental study of flows and of their evolution until critical heating by using appropriate measurement instruments. The objective is to understand how flow evolution may condition critical heating. After a recall of some notions and values related to the study of two-phase flows, and an overview of published works on flow configurations and on critical heating, the author describes test installation and measurement devices, presents the typical test process, reports instrument calibration, and flow configuration tests with water-air flow under low pressure. Results are reported. The author proposes explanations regarding observed phenomena, and a possible scheme to explain the flow evolution until critical heating [fr
International fund flows: surges, sudden stops, and cyclicality
Li, Suxiao
2017-01-01
International fund flows are cross-border investments in domestic equity and bond markets by global investment funds. They have increased dramatically since the 1990s and played an increasingly important role in the transmission of shocks. In this thesis, we examine the drivers of large changes in
Particle flow calorimetry at the international linear collider
Indian Academy of Sciences (India)
Particle flow calorimetry at the international linear ... It is widely believed that the most promising strategy for achieving a jet ... this level of performance for two main reasons. Firstly ... (i) Tracking: For the studies presented in this paper, the track pattern ... that particles propagating outward from the interaction region will cross ...
International Nuclear Information System (INIS)
Fieg, G.
1977-01-01
The present paper deals with the application of various measuring methods in model experiments for studying the steady heat transport from volume-heated liquid films by natural convection. The aim of these model experiments is to test computing models for temperature and flow behavior of internally heated liquid films at different boundary conditions. Therefore, besides pure heat transfer measurements, temperature as well as velocity fields must be experimentally determined. Determination of the temperature fields is carried our with suitable thermoelements of small size, the velocity fields are determined by the laser-Doppler method as well as the stroboscopic method for photographically visualizing the flow. (orig.) [de
GPU accelerated study of heat transfer and fluid flow by lattice Boltzmann method on CUDA
Ren, Qinlong
,000 US dollars. The release of NVIDIA's CUDA architecture which includes both hardware and programming environment in 2007 makes GPU computing attractive. Due to its highly parallel nature, lattice Boltzmann method is successfully ported into GPU with a performance benefit during the recent years. In the current work, LBM CUDA code is developed for different fluid flow and heat transfer problems. In this dissertation, lattice Boltzmann method and immersed boundary method are used to study natural convection in an enclosure with an array of conduting obstacles, double-diffusive convection in a vertical cavity with Soret and Dufour effects, PCM melting process in a latent heat thermal energy storage system with internal fins, mixed convection in a lid-driven cavity with a sinusoidal cylinder, and AC electrothermal pumping in microfluidic systems on a CUDA computational platform. It is demonstrated that LBM is an efficient method to simulate complex heat transfer problems using GPU on CUDA.
Hong, Bong Hwan; Jung, In Su
2017-07-01
A water target was designed to enhance cooling efficiency using a thermosyphon, which is a system that uses natural convection to induce heat exchange. Two water targets were fabricated: a square target without any flow channel and a target with a flow channel design to induce a thermosyphon mechanism. These two targets had the same internal volume of 8 ml. First, visualization experiments were performed to observe the internal flow by natural convection. Subsequently, an experiment was conducted to compare the cooling performance of both water targets by measuring the temperature and pressure. A 30-MeV proton beam with a beam current of 20 μA was used to irradiate both targets. Consequently, the target with an internal flow channel had a lower mean temperature and a 50% pressure drop compared to the target without a flow channel during proton beam irradiation. Copyright © 2017 Elsevier Ltd. All rights reserved.
Beam Flutter and Energy Harvesting in Internal Flow
Tosi, Luis Phillipe; Colonius, Tim; Sherrit, Stewart; Lee, Hyeong Jae
2017-11-01
Aeroelastic flutter, largely studied for causing engineering failures, has more recently been used as a means of extracting energy from the flow. Particularly, flutter of a cantilever or an elastically mounted plate in a converging-diverging flow passage has shown promise as an energy harvesting concept for internal flow applications. The instability onset is observed as a function of throat velocity, internal wall geometry, fluid and structure material properties. To enable these devices, our work explores features of the fluid-structure coupled dynamics as a function of relevant nondimensional parameters. The flutter boundary is examined through stability analysis of a reduced order model, and corroborated with numerical simulations at low Reynolds number. Experiments for an energy harvester design are qualitatively compared to results from analytical and numerical work, suggesting a robust limit cycle ensues due to a subcritical Hopf bifurcation. Bosch Corporation.
Jiang, Q. F.; Zhuang, M.; Zhu, Z. G.; Y Zhang, Q.; Sheng, L. H.
2017-12-01
Counter-flow plate-fin heat exchangers are commonly utilized in cryogenic applications due to their high effectiveness and compact size. For cryogenic heat exchangers in helium liquefaction/refrigeration systems, conventional design theory is no longer applicable and they are usually sensitive to longitudinal heat conduction, heat in-leak from surroundings and variable fluid properties. Governing equations based on distributed parameter method are developed to evaluate performance deterioration caused by these effects. The numerical model could also be applied in many other recuperators with different structures and, hence, available experimental data are used to validate it. For a specific case of the multi-stream heat exchanger in the EAST helium refrigerator, quantitative effects of these heat losses are further discussed, in comparison with design results obtained by the common commercial software. The numerical model could be useful to evaluate and rate the heat exchanger performance under the actual cryogenic environment.
CCC, Heat Flow and Mass Flow in Liquid Saturated Porous Media
International Nuclear Information System (INIS)
Mangold, D.C.; Lippmann, M.J.; Bodvarsson, G.S.
1982-01-01
1 - Description of problem or function: The numerical model CCC (conduction-convection-consolidation) solves the heat and mass flow equations for a fully, liquid-saturated, anisotropic porous medium and computes one-dimensional (vertical) consolidation of the simulated systems. The model has been applied to problems in the fields of geothermal reservoir engineering, aquifer thermal energy storage, well testing, radioactive waste isolation, and in situ coal combustion. The code has been validated against analytic solutions for fluid and heat flow, and against a field experiment for underground storage of hot water. 2 - Method of solution: The model employs the Integrated Finite Difference Method (IFDM) in discretizing the saturated porous medium and formulating the governing equations. The sets of equations are sol- ved by an iterative solution technique. The vertical deformation of the medium is calculated using the one-dimensional consolidation theory of Terzaghi. 3 - Restrictions on the complexity of the problem: Maximum of 12 materials. It is assumed that: (a) Darcy's law adequately describes fluid movement through fractured and porous media. (b) The rock and fluid are in thermal equilibrium at any given time. (c) Energy changes due to the fluid compressibility, acceleration and viscous dissipation are neglected. (d) One-dimensional consolidation theory adequately describes the vertical deformation of the medium
Numerical simulation of flow field in shellside of heat exchanger in nuclear power plant
International Nuclear Information System (INIS)
Wang Xinliang; Qiu Jinrong; Gong Zili
2010-01-01
Heat exchanger is the important equipment of nuclear power plant. Numerical simulation can give the detail information inside the heat exchange, and has been an effective research method. The geometric structure of shell-and-tube heat exchanger is very complex and it is difficult to simulate the whole flow field presently. According to the structure characteristics of the heat exchanger, a periodic whole-section calculation model was presented. The numerical simulation of flow field in shellside of heat exchange of a nuclear power plant was done by using this model. The results of simulation show that heat transfer in the periodic section of the heat exchange is uniform, the heat transfer is enhanced by using baffles in heat exchange, and frictional resistance is primary from the effect of segmental baffles. (authors)
DEFF Research Database (Denmark)
Vejen, Niels Kristian
1997-01-01
A low flow solar heating system for space heating and domestic hot water supply from Aidt Miljø A/Swas tested in a laboratory test facility.......A low flow solar heating system for space heating and domestic hot water supply from Aidt Miljø A/Swas tested in a laboratory test facility....
International Nuclear Information System (INIS)
Peletier, Mark A.; Redig, Frank; Vafayi, Kiamars
2014-01-01
We consider three one-dimensional continuous-time Markov processes on a lattice, each of which models the conduction of heat: the family of Brownian Energy Processes with parameter m (BEP(m)), a Generalized Brownian Energy Process, and the Kipnis-Marchioro-Presutti (KMP) process. The hydrodynamic limit of each of these three processes is a parabolic equation, the linear heat equation in the case of the BEP(m) and the KMP, and a nonlinear heat equation for the Generalized Brownian Energy Process with parameter a (GBEP(a)). We prove the hydrodynamic limit rigorously for the BEP(m), and give a formal derivation for the GBEP(a). We then formally derive the pathwise large-deviation rate functional for the empirical measure of the three processes. These rate functionals imply gradient-flow structures for the limiting linear and nonlinear heat equations. We contrast these gradient-flow structures with those for processes describing the diffusion of mass, most importantly the class of Wasserstein gradient-flow systems. The linear and nonlinear heat-equation gradient-flow structures are each driven by entropy terms of the form −log ρ; they involve dissipation or mobility terms of order ρ 2 for the linear heat equation, and a nonlinear function of ρ for the nonlinear heat equation
Analysis of the convective heat transfer of a fluid flow over an ...
African Journals Online (AJOL)
Convective heat transfer in a homogeneous fluid flow Reynolds number of order less than 2000 over an immersed axi-symmetrical body with curved surfaces has been investigated. The fluid flow in consideration was unsteady and of constant density .This study analysed the extent to which convective heat transfer has on ...
Probabilistic tectonic heat flow modelling for basin maturation: method and applications
van Wees, J.D.A.M.; van Bergen, F.; David, P.; Nepveu, M.; Beekman, W.W.W.; Cloetingh, S.A.P.L.; Bonte, D.D.P.
2009-01-01
Tectonic modeling is often neglected in the basin modeling workflow and heat flow is most times considered a user input. Such heat flows can, therefore, result in erroneous basin modeling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify
Probabilistic tectonic heat flow modeling for basin maturation: Assessment method and applications
Wees, J.D. van; Bergen, F. van; David, P.; Nepveu, M.; Beekman, F.; Cloetingh, S.; Bonté, D.
2009-01-01
Tectonic modeling is often neglected in the basin modeling workflow and heat flow is most times considered a user input. Such heat flows can, therefore, result in erroneous basin modeling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify
Turbulent heat transfer to longitudinal flow through a triangular array of circular rods
International Nuclear Information System (INIS)
Pfann, J.
1975-01-01
Temperature distribution and heat transfer to longitudinal turbulent, fully developed flow through triangular arrays of smooth circular rods are analysed for liquids with Prandtl number approximately 1 and << 1. Nusselt number is plotted versus pitch and turbulence for constant heat flow and for constant temperature on the rod surface, and the optimum pitch is determined. The influence of Prandtl number is analysed. (Auth.)
Directory of Open Access Journals (Sweden)
Xue Xiang
2010-08-01
Full Text Available The boundary heat flow has important significance for the microstructures of directional solidified binary alloy. Interface evolution of the directional solidified microstructure with different boundary heat flow was discussed. In this study, only one interface was allowed to have heat flow, and Neumann boundary conditions were imposed at the other three interfaces. From the calculated results, it was found that different boundary heat flows will result in different microstructures. When the boundary heat flow equals to 20 W·cm-2, the growth of longitudinal side branches is accelerated and the growth of transverse side branches is restrained, and meanwhile, there is dendritic remelting in the calculation domain. When the boundary heat flow equals to 40 W·cm-2, the growths of the transverse and longitudinal side branches compete with each other, and when the boundary heat flow equals to 100-200 W·cm-2, the growth of transverse side branches dominates absolutely. The temperature field of dendritic growth was analyzed and the relation between boundary heat flow and temperature field was also investigated.
Wees, J.D. van; Bonte, D.; Nelskamp, S.
2009-01-01
Basement heat flow is one of the most influential parameters on basin maturity. Although rapid progress has been made in the development of tectonic models capable of modelling the thermal consequences of basin formation, these models are hardly used in basin modelling. To better predict heat flows
Comparison of heat transfer in straight and corrugated minichannels with two-phase flow
Directory of Open Access Journals (Sweden)
Peukert P.
2014-03-01
Full Text Available Measurements of heat transfer rates performed with an experimental condensation heat exchanger are reported for a corrugated minichannel tube and for a straight minichannel tube. The two cases were compared at same flow regimes. The corrugation appears advantageous for relatively low steam pressures and flow rates where much higher heat transfer rates were observed close to the steam entrance, thus allowing shortening the heat exchanger with the associated advantages of costs lowering and smaller built-up space. At high steam pressures and high flow rates both tubes performed similarly.
Experimental determination of heat transfer in a Poiseuille-Rayleigh-Bénard flow
Taher, R.; Abid, C.
2018-05-01
This paper deals with an experimental study of heat transfer in a Poiseuille-Rayleigh-Bénard flow. This situation corresponds to a mixed convection phenomenon in a horizontal rectangular channel uniformly heated from below. Flow visualisation and temperature measurements were achieved in order to describe the flow regimes and heat transfer behaviour. The classical measurement techniques such employing thermocouples give local measurement on one hand and on other hand they often disturb the flow. As the flow is three-dimensional, these techniques are not efficient. In order to not disturb the flow, a non-intrusive method is used for thermal measurement. The Planar laser Induced Fluorescence (PLIF) was implemented to determine thermal fields in the fluid. Experiments conducted for various Reynolds and Rayleigh numbers allow to determine the heat transfer and thus to propose correlation for Nusselt number for a mixed convection flow in Poiseuille-Rayleigh-Bénard configuration. First a description of the use of this technique in water flow is presented and then the obtained results for various Reynolds and Rayleigh numbers allow to propose a correlation for the Nusselt number for such configuration of mixed convection. The comparison between the obtained heat transfer and the pure forced convection one confirms the well-known result that the convective heat transfer is greatly enhanced in mixed convection. Indeed, secondary flow induced by buoyant forces contributes to the refreshment of thermal boundary layers and so acts like mixers, which significantly enhances heat transfer.
Directory of Open Access Journals (Sweden)
Zonghao Yang
2017-12-01
Full Text Available In the passive residual heat removal system of a molten salt reactor, one of the residual heat removal methods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residual heat of fuel salts. An experimental loop is designed and built with a single heat transfer element to analyze the heat transfer and flow characteristics. In this research, the influence of the size of a three-layer thimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are used to obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gas gap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gas gap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. In addition, a natural circulation startup process is described in this paper. Finally, flashing natural circulation instability has been observed in this thimble-type heat transfer element.
DEFF Research Database (Denmark)
Shibasaki, M.; Rasmussen, P.; Secher, Niels H.
2009-01-01
as an absence of sweating and cutaneous vasodilatation during a whole-body heat stress. Upon this confirmation, adenosine was perfused through one of the microdialysis probes to increase skin blood flow similar to that of the unblocked site. After internal temperature increased approximately 0.7 degrees C......During heat stress, isometric handgrip (IHG) exercise causes cutaneous vasoconstriction, but it remains controversial whether neural mechanisms are responsible for this observation. The objective of this study was to test the hypothesis that cutaneous vasoconstriction during IHG exercise in heat...... stressed individuals occurs via a neural mechanism. An axillary nerve blockade was performed to block efferent nerve traffic to the left forearm in seven healthy subjects. Two intradermal microdialysis probes were placed within forearm skin of the blocked area. Forearm skin blood flow was measured by laser...
International migration flows. Framework for understanding and current features.
Directory of Open Access Journals (Sweden)
Colectivo IOÉ
2016-10-01
Full Text Available The present article aims to outline a framework for the understanding of the present international migratory flows as well as to outline their main traits. In order to do this, we first group together the different migratory flows produced since the sixteenth century up to the mid seventies in the twentieth century, stopping then for a closer look at the present situation which register the impact of economic globalization, translating it into an increase of said flows and, above all, to their enormous diversification. To end, we make a brief balance of the present period and a critical evaluation on the meaning of one of the flows which attracts most attention, economic migrations south-north, because these are the ones which have the most impact on developed countries.
Application of two-equation turbulence models to turbulent gas flow heated by a high heat flux
International Nuclear Information System (INIS)
Kawamura, Hiroshi
1978-01-01
Heat transfer in heated turbulent gas flow is analyzed using two-equation turbulence models. Four kinds of two-equation models are examined; that is, k-epsilon model by Jones-Launder, k-w model by Wilcox-Traci, k-kL model by Rotta, k-ω model by Saffman-Wilcox. The results are compared with more than ten experiments by seven authors. The k-kL model proposed originally by Rotta and modified by the present author is found to give relatively the best results. It well predicts the decrease in the heat transfer coefficient found in the heated turbulent gas flow; however, it fails to predict the laminarization due to a strong heating. (author)
Azhar, Waqas Ali; Vieru, Dumitru; Fetecau, Constantin
2017-08-01
Free convection flow of some water based fractional nanofluids over a moving infinite vertical plate with uniform heat flux and heat source is analytically and graphically studied. Exact solutions for dimensionless temperature and velocity fields, Nusselt numbers, and skin friction coefficients are established in integral form in terms of modified Bessel functions of the first kind. These solutions satisfy all imposed initial and boundary conditions and reduce to the similar solutions for ordinary nanofluids when the fractional parameters tend to one. Furthermore, they reduce to the known solutions from the literature when the plate is fixed and the heat source is absent. The influence of fractional parameters on heat transfer and fluid motion is graphically underlined and discussed. The enhancement of heat transfer in such flows is higher for fractional nanofluids in comparison with ordinary nanofluids. Moreover, the use of fractional models allows us to choose the fractional parameters in order to get a very good agreement between experimental and theoretical results.
Critical heat-flux experiments under low-flow conditions in a vertical annulus
International Nuclear Information System (INIS)
Mishima, K.; Ishii, M.
1982-03-01
An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam-water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn-turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding-limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF
International Nuclear Information System (INIS)
Kurganov, V.A.; Gladuntsov, A.I.
1977-01-01
Analysed are the experimental data obtained for heat transfer to gaseous dissociating ammonium (NH 3 ) under heating in round pipes (steel Kh18N10T) at developed eddying input flow and marginal condition of heat supply gsub(c) approximately equal to const in the ranges of the following parameters: p=3-10 atm; Tsub(input)=310-720 K; Tsub(c) ( 3 ; gsub(c)/-anti rho W 8.8 kJ/kg; gsub(c)/(anti rho WCsub(p) sub(input)Tsub(input)) (<=) 0.0104; 1/d (<=) 150 (where Tsub(c) is the wall temperature, gsub(c) the heat flow density on wall, and anti rho W velocity). The discussion involves phenomena of worsened heat transfer at high heat loads. The authors show the basic relationship between these phenomena and laminarization of the near-wall flow at the input site of the pipe. The regularities of heat transfer were noted to undergo substantial transformation under laminarized flow
Semi-empirical model for heat transfer coefficient in liquid metal turbulent flow
International Nuclear Information System (INIS)
Fernandez y Fernandez, E.; Carajilescov, P.
1982-01-01
The heat transfer by forced convection in a metal liquid turbulent flow for circular ducts is analyzed. An analogy between the momentum and heat in the wall surface, is determined, aiming to determine an expression for heat transfer coefficient in function of the friction coefficient. (E.G.) [pt
Thermal mechanical analysis of applications with internal heat generation
Govindarajan, Srisharan Garg
The radioactive tracer Technetium-99m is widely used in medical imaging and is derived from its parent isotope Molybedenum-99 (Mo-99) by radioactive decay. The majority of Molybdenum-99 (Mo-99) produced internationally is extracted from high enriched uranium (HEU) dispersion targets that have been irradiated. To alleviate proliferation risks associated with HEU-based targets, the use of non-HEU sources is being mandated. However, the conversion of HEU to LEU based dispersion targets affects the Mo-99 available for chemical extraction. A possible approach to increase the uranium density, to recover the loss in Mo-99 production-per-target, is to use an LEU metal foil placed within an aluminum cladding to form a composite structure. The target is expected to contain the fission products and to dissipate the generated heat to the reactor coolant. In the event of interfacial separation, an increase in the thermal resistance could lead to an unacceptable rise in the LEU temperature and stresses in the target. The target can be deemed structurally safe as long as the thermally induced stresses are within the yield strength of the cladding and welds. As with the thermal and structural safety of the annular target, the thermally induced deflection of the BORALRTM-based control blades, used by the University of Missouri Research Reactor (MURRRTM ), during reactor operation has been analyzed. The boron, which is the neutron absorber in BORAL, and aluminum mixture (BORAL meat) and the aluminum cladding are bonded together through powder metallurgy to establish an adherent bonded plate. As the BORAL absorbs both neutron particles and gamma rays, there is volumetric heat generation and a corresponding rise in temperature. Since the BORAL meat and aluminum cladding materials have different thermal expansion coefficients, the blade may have a tendency to deform as the blade temperature changes and the materials expand at different rates. In addition to the composite nature of the
Investigation of heat transfer of tube line of staggered tube bank in two-phase flow
Jakubcionis, Mindaugas
2015-06-01
This article presents the results of experimental investigation of heat transfer process, carried out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exchanger model consisted of staggered tube bank. Experimental results are presented with the focus on influence of tube position in the line of the bank, volumetric void component and velocity of gas component of the foam. The phenomena of liquid draining in cellular foam flow and its influence on heat transfer rate has also been discussed. The experimental results have been generalized by relationship between Nusselt, Reynolds and Prandtl numbers.
Nigodjuk, V. E.; Sulinov, A. V.
2018-01-01
The article presents the results of experimental studies of hydrodynamics and those of loobman single-phase and two-phase flows in capillary nozzle elements propellant thrusters and the proposed method of their calculation. An experimental study was performed in capillaries with a sharp entrance edge of the internal diameter of 0.16 and 0.33 mm and a relative length 188 and 161, respectively, in pouring distilled water and acetone in the following range of parameters Reynolds number Re = (0,3 ... 10) · 103, Prandtl number Pr = (2 ... 10), pressure p = (0,1 ... 0,3) MPa, the heat flux q = (0...2)×106 W/m2, the difference of temperature under-heating of liquid Δtn = (5 ... 80)K. The dependences for calculation of single phase boundaries, the undeveloped and the developed surface of the bubble and film key singing of subcooled liquid. It is shown theoretically and experimentally confirmed the virtual absence of areas of undeveloped nucleate boiling in laminar flow. The dependence for calculation of hydraulic resistance and heat transfer in the investigated areas of current. It is shown that in the region of nucleate boiling surface in the flow in capillary tubes, influence of the formed vapor phase on the hydrodynamics and heat transfer substantially higher than in larger diameter pipes.
Stretched flow of Oldroyd-B fluid with Cattaneo-Christov heat flux
Directory of Open Access Journals (Sweden)
T. Hayat
Full Text Available The objective of present attempt is to analyse the flow and heat transfer in the flow of an Oldroyd-B fluid over a non-linear stretching sheet having variable thickness. Characteristics of heat transfer are analyzed with temperature dependent thermal conductivity and heat source/sink. Cattaneo-Christov heat flux model is considered rather than Fourier’s law of heat conduction in the present flow analysis. Thermal conductivity varies with temperature. Resulting partial differential equations through laws of conservation of mass, linear momentum and energy are converted into ordinary differential equations by suitable transformations. Convergent series solutions for the velocity and temperature distributions are developed and discussed. Keywords: Oldroyd-B fluid, Variable sheet thickness, Cattaneo-Christov heat flux model, Heat source/sink, Temperature dependent thermal conductivity
Mathematical modelling of thermal and flow processes in vertical ground heat exchangers
Directory of Open Access Journals (Sweden)
Pater Sebastian
2017-12-01
Full Text Available The main task of mathematical modelling of thermal and flow processes in vertical ground heat exchanger (BHE-Borehole Heat Exchanger is to determine the unit of borehole depth heat flux obtainable or transferred during the operation of the installation. This assignment is indirectly associated with finding the circulating fluid temperature flowing out from the U-tube at a given inlet temperature of fluid in respect to other operational parameters of the installation.
Systematic heat flow measurements across the Wagner Basin, northern Gulf of California
Neumann, Florian; Negrete-Aranda, Raquel; Harris, Robert N.; Contreras, Juan; Sclater, John G.; González-Fernández, Antonio
2017-12-01
A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ∼1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220 ± 60, 99 ± 14, 889 ± 419 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Moreover, heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.
An analytical solution to the heat transfer problem in thick-walled hunt flow
International Nuclear Information System (INIS)
Bluck, Michael J; Wolfendale, Michael J
2017-01-01
Highlights: • Convective heat transfer in Hunt type flow of a liquid metal in a rectangular duct. • Analytical solution to the H1 constant peripheral temperature in a rectangular duct. • New H1 result demonstrating the enhancement of heat transfer due to flow distortion by the applied magnetic field. • Analytical solution to the H2 constant peripheral heat flux in a rectangular duct. • New H2 result demonstrating the reduction of heat transfer due to flow distortion by the applied magnetic field. • Results are important for validation of CFD in magnetohydrodynamics and for implementation of systems code approaches. - Abstract: The flow of a liquid metal in a rectangular duct, subject to a strong transverse magnetic field is of interest in a number of applications. An important application of such flows is in the context of coolants in fusion reactors, where heat is transferred to a lead-lithium eutectic. It is vital, therefore, that the heat transfer mechanisms are understood. Forced convection heat transfer is strongly dependent on the flow profile. In the hydrodynamic case, Nusselt numbers and the like, have long been well characterised in duct geometries. In the case of liquid metals in strong magnetic fields (magnetohydrodynamics), the flow profiles are very different and one can expect a concomitant effect on convective heat transfer. For fully developed laminar flows, the magnetohydrodynamic problem can be characterised in terms of two coupled partial differential equations. The problem of heat transfer for perfectly electrically insulating boundaries (Shercliff case) has been studied previously (Bluck et al., 2015). In this paper, we demonstrate corresponding analytical solutions for the case of conducting hartmann walls of arbitrary thickness. The flow is very different from the Shercliff case, exhibiting jets near the side walls and core flow suppression which have profound effects on heat transfer.
Heat transfer to air-water two-phase flow in slug/churn region
International Nuclear Information System (INIS)
Wadekar, V.V.; Tuzla, K.; Chen, J.C.
1996-01-01
Measured heat transfer data for air-water two-phase flow in the slug/churn flow region are reported. The measurements were obtained from a 1.3 m tall, 15.7 mm diameter vertical tube test-section. It is observed that the data exhibit different heat transfer characteristics to those predicted by the standard correlations for the convective component of flow boiling heat transfer. Comparison with the predictions of a slug flow model for evaporation shows a significant overprediction of the data. The reason for the overprediction is attributed to the sensible heating requirement of the gas phase. The slug flow model is therefore suitably modified for non-evaporating two-phase flow. This specially adapted model is found to give reasonably good predictions of the measured data
Analysis of the one-dimensional transient compressible vapor flow in heat pipes
Jang, Jong H.; Faghri, Amir; Chang, Won S.
1991-01-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds as well as high mass flow rates are successfully predicted.
Experimental investigation of natural convection induced by internal heat generation
International Nuclear Information System (INIS)
Tasaka, Y; Kudoh, Y; Takeda, Y; Yanagisawa, T
2005-01-01
Dilatation of a convection cell with respect to its Rayleigh number, one of the problems in internally heated convection, was quantitatively investigated by analyzing temperature field in a cell. The temperature field visualized by a thermo-chromic liquid crystal (TLC) expresses the cell dilatation. A calibration system was developed to convert the visualized photographs of the temperature field to the temperature field. A calibration curve correlating color information extracted from the photograph and temperature was determined from the approximately linear temperature distribution in the horizontal fluid layer using the hue method. Photos taken at various internal Rayleigh numbers were converted to the temperature field by the obtained curve. Extracting individual cells from a temperature field achieves a quantitative expression of the cell dilatation as the variation of the wavenumber of the cell with Rayleigh number increases. The temperature profile in a cell shows that high temperature areas appear at the apexes of the cell, largely different from the profile obtained by linear theory
Analysis of Tube Bank Heat Transfer In Downward Directed Foam Flow
Directory of Open Access Journals (Sweden)
Jonas Gylys
2004-06-01
Full Text Available Apparatus with the foam flow are suitable to use in different technologies like heat exchangers, food industry, chemical and oil processing industry. Statically stable liquid foam until now is used in technologic systems rather seldom. Although a usage of this type of foam as heat transfer agent in foam equipment has a number of advantages in comparison with one phase liquid equipment: small quantity of liquid is required, heat transfer rate is rather high, mass of equipment is much smaller, energy consumption for foam delivery into heat transfer zone is lower. The paper analyzes the peculiarities of heat transfer from distributed in staggered order and perpendicular to foam flow in channel of rectangular cross section tube bundle to the foam flow. It was estimated the dependence of mean gas velocity and volumetric void fraction of foam flow to heat transfer in downward foam flow. Significant difference of heat transfer intensity from front and back tubes of tube row in laminar foam flow was noticed. Dependence of heat transfer on flow velocity and volumetric void fraction of foam was confirmed and estimated by criterion equations.
International Nuclear Information System (INIS)
Salem, Ahmed M.
2007-01-01
The problem of flow and heat transfer of an electrically conducting viscoelastic fluid over a continuously stretching sheet in the presence of a uniform magnetic field is analyzed for the case of power-law variation in the sheet temperature. The fluid viscosity and thermal conductivity are assumed to vary as a function of temperature. The basic equations comprising the balance laws of mass, linear momentum, and energy modified to include the electromagnetic force effect, the viscous dissipation, internal heat generation or absorption and work due to deformation are solved numerically
International Nuclear Information System (INIS)
Sahin, Ahmet Z.
2012-01-01
Highlights: ► The optimality in both heat and fluid flow systems has been investigated. ► A new thermodynamic property has been introduced. ► The second law of thermodynamics was extended to present the temheat balance that included the temheat destruction. ► The principle of temheat destruction minimization was introduced. ► It is shown that the rate of total temheat destruction is minimized in steady heat conduction and fluid flow problems. - Abstract: Heat transfer and fluid flow processes exhibit similarities as they occur naturally and are governed by the same type of differential equations. Natural phenomena occur always in an optimum way. In this paper, the natural optimality that exists in the heat transfer and fluid flow processes is investigated. In this regard, heat transfer and fluid flow problems are treated as optimization problems. We discovered a thermodynamic quantity that is optimized during the steady heat transfer and fluid flow processes. Consequently, a new thermodynamic property, the so called temheat, is introduced using the second law of thermodynamics and the definition of entropy. It is shown, through several examples, that overall temheat destruction is always minimized in steady heat and fluid flow processes. The principle of temheat destruction minimization that is based on the temheat balance equation provides a better insight to understand how the natural flow processes take place.
Heat flows and energetic behavior of a telecommunication radio base station
International Nuclear Information System (INIS)
Petraglia, Antonio; Spagnuolo, Antonio; Vetromile, Carmela; D'Onofrio, Antonio; Lubritto, Carmine
2015-01-01
This paper shows a study on energetic consumption of BTSs (Base Transceiver Stations) for mobile communication, related to conditioning functions. An energetic “thermal model” of a telecommunication station is proposed and studied. The results have been validated with a BTS in central Italy, showing good agreement. Findings show a substantial high internal-external temperature difference in the containing shelter, particularly during daytime and warm months, due to sources of heat (equipment, external temperature and sun radiation) and to the difficulty in spread the warmth out. The necessity to keep the operating temperatures within a given range for the correct functioning of the electronic equipment requires the use of conditioning setups, and this significantly increases the energetic demand of the whole system. The analysis of thermal flows across the shelter can help to gather further data on its temperature behavior and to devise practical measures to lower the power demand, while keeping the operating parameters in the suggested ranges. The investigation of some operating parameters of the equipment and of the shelter, such as threshold set-points, air vent area, external wall transmittance and reflectivity, suggests annual energy savings between 10% and 30%. - Highlights: • A heat flow model for a telecommunication shelter was created. • Successful matching of the model and real-life cases was obtained. • The model addresses how each parameter affects energy consumption. • Reasonably savings of up to 30% of consumed energy can be expected