A Study of High-Temperature Heat Pipes With Multiple Heat Sources and Sinks: Part II—Analysis of Continuum Transient and Steady-State Experimental Data With Numerical Predictions

1991 ◽  
Vol 113 (4) ◽  
pp. 1010-1016 ◽  
Author(s):  
A. Faghri ◽  
M. Buchko ◽  
Y. Cao
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Heat Pipe ◽  
Pipe Wall ◽  
Heat Sources ◽  
Maximum Heat ◽  
Sources And Sinks ◽  
Numerical Predictions ◽  
Wick Structure ◽  
Transient And Steady State

The experimental data presented in Part I were analyzed concerning the heat pipe performance characteristics and design. Postexperiment examination of the loosely wrapped screen wick revealed annular gaps both between the wick and the heat pipe wall and between adjacent screen layers, which greatly enhanced the maximum heat capacity of the heat pipe compared to the analytical capillary limit for a tightly wrapped screen wick. A numerical simulation for transient heat pipe performances including the vapor region, wick structure, and the heat pipe wall is given. Numerical results for continuum transient and steady-state operations with multiple heat sources were compared with experimental results and found to be in good agreement.

scholarly journals Numerical simulation of flattened heat pipe with double heat sources for CPU and GPU cooling application in laptop computers

2020 ◽  
Author(s):  
Wisoot Sanhan ◽  
Kambiz Vafai ◽  
Niti Kammuang-Lue ◽  
Pradit Terdtoon ◽  
Phrut Sakulchangsatjatai
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Graphics Processing Unit ◽  
Processing Unit ◽  
Heat Sources ◽  
Final Thickness ◽  
Laptop Computers ◽  
Central Processing ◽  
Graphics Processing ◽  
Good Agreement

Abstract An investigation of the effect of the thermal performance of the flattened heat pipe on its double heat sources acting as central processing unit and graphics processing unit in laptop computers is presented in this work. A finite element method is used for predicting the flattening effect of the heat pipe. The cylindrical heat pipe with a diameter of 6 mm and the total length of 200 mm is flattened into three final thicknesses of 2, 3, and 4 mm. The heat pipe is placed under a horizontal configuration and heated with heater 1 and heater 2, 40 W in combination. The numerical model shows good agreement compared with the experimental data with the standard deviation of 1.85%. The results also show that flattening the cylindrical heat pipe to 66.7 and 41.7% of its original diameter could reduce its normalized thermal resistance by 5.2%. The optimized final thickness or the best design final thickness for the heat pipe is found to be 2.5 mm.

The Heat Transport Capacity of Micro Heat Pipes

1998 ◽  
Vol 120 (4) ◽  
pp. 1064-1071 ◽  
Author(s):  
J. M. Ha ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Original Model ◽  
Semiempirical Model ◽  
Transport Capacity ◽  
Predictive Tool ◽  
Maximum Heat ◽  
Micro Heat Pipes

The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

Design and Research of Flat Micro Heat Pipe with Glass Fiber Wick

2011 ◽  
Vol 483 ◽  
pp. 603-606
Author(s):  
Tian Han ◽  
Xiao Wei Liu ◽  
Chao Wang
Keyword(s):  
Glass Fiber ◽  
Heat Pipe ◽  
Experimental Testing ◽  
Governing Equations ◽  
Maximum Heat ◽  
One Dimensional ◽  
Micro Heat Pipe ◽  
Wick Structure

A kind of flat micro heat pipe with glass fiber wick structure is designed and fabricated. The structure of the wick is presented and also the excellence of the structure is described. For the glass fiber wick, the maximum heat transports is calculated by one-dimensional steady governing equations. Experimental testing is performed for the fabricated micro heat pipe in vacuum. The testing results is presented and analyzed.

Transient Damped Wave Conduction and Relaxation in Human Skin and Thermal Wear During Winter

2008 ◽  
Author(s):  
Kal Renganathan Sharma
Keyword(s):  
Steady State ◽  
Human Skin ◽  
Separation Of Variables ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Transient Temperature ◽  
Heat Sources ◽  
Maximum Heat ◽  
Steady State Temperature ◽  
Fabric Layer

Damped wave conduction and relaxation in the human skin layer and thermal fabric layer are modeled with a temperature dependent heat source in the human tissue layer. Steady state temperature profiles are derived from the Fourier heat conduction equation. The general solution for the temperature is assumed to be a sum of the transient temperature and steady state temperature. This makes the boundary conditions in space for the skin and fabric layers homogeneous for the transient temperarature. The hyperbolic PDE is solved for by the method of separation of variables. The use of final condition in time in addition to the initial temperature condition leads to bounded infinite Fourier series solutions. These solutions are bounded and does not violate second law of thermodynamics. The model can be used to interpret experimental observations of maximum heat flux that is a parameter of the warm/cool feeling of human skin in winter. For large relaxation times of human skin tissue, τrs>(1+U*)2(b−a)216π2αs, the transient temperature can be expected to undergo oscillations. These oscillations will be supercritical and grow with time for strong heat sources, U* > 1 and may be subcritical damped oscillatory for weak heat sources, U* < 1. For large thermal relaxation times of thermal fabric material, τrf>a24π2αs, the transient temperature in the thermal fabric layer may be expected to be subcritical damped oscillatory.

A Study of Multiple Heat Sources on a Flat Plate Heat Pipe Using Point Source Approach

1999 ◽  
Author(s):  
Tan Boon Keng
Keyword(s):  
Flat Plate ◽  
Heat Pipe ◽  
Delta Function ◽  
Point Sources ◽  
Heat Sources ◽  
Plate Heat ◽  
Dirac Delta ◽  
Wick Structure ◽  
Optimum Heat ◽  
Flat Plate Heat Pipe

Abstract An analytical approach has been employed to study liquid flows in an isotropic wick structure of a flat plate heat pipe with multiple heat sources so as to determine the optimum heat pipe performance. In this study, the heat sources have been modeled as point sources using the Dirac Delta function to describe the heat distribution. The two dimensional pressure and velocity distribution are shown and discussed. The study has been extended to locate the positions of the multiple heat sources for optimum heat pipe performance. The optimum performance of the heat pipe is accomplished when the minimum pressure drop is attained across the wick structure.

The Effect of Working Fluid Inventory on the Performance of Revolving Helically Grooved Heat Pipes

2000 ◽  
Vol 123 (1) ◽  
pp. 120-129 ◽  
Author(s):  
R. Michael Castle ◽  
Scott K. Thomas ◽  
Kirk L. Yerkes
Keyword(s):  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Maximum Heat ◽  
Limit Model ◽  
Filling Station ◽  
Capillary Limit ◽  
Helical Groove ◽  
Wick Structure ◽  
Evaporative Heat Transfer

The results of a recently completed experimental and analytical study showed that the capillary limit of a helically-grooved heat pipe (HGHP) was increased significantly when the transverse body force field was increased. This was due to the geometry of the helical groove wick structure. The objective of the present research was to experimentally determine the performance of revolving helically-grooved heat pipes when the working fluid inventory was varied. This report describes the measurement of the geometry of the heat pipe wick structure and the construction and testing of a heat pipe filling station. In addition, an extensive analysis of the uncertainty involved in the filling procedure and working fluid inventory has been outlined. Experimental measurements include the maximum heat transport, thermal resistance and evaporative heat transfer coefficient of the revolving helically grooved heat pipe for radial accelerations of |a⃗r|=0.0, 2.0, 4.0, 6.0, 8.0, and 10.0-g and working fluid fills of G=0.5, 1.0, and 1.5. An existing capillary limit model was updated and comparisons were made to the present experimental data.

TRANSIENT AND STEADY STATE PROPERTIES OF THE INVERSE FARADAY EFFECT — SIMULATION AND THEORY

1991 ◽  
Vol 05 (22) ◽  
pp. 1533-1542 ◽  
Author(s):  
M.W. EVANS
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Steady State ◽  
Laser Pulse ◽  
Kerr Effect ◽  
Faraday Effect ◽  
Inverse Faraday Effect ◽  
Visible Frequency ◽  
Frequency Laser ◽  
Transient And Steady State

A computer simulation of the inverse Faraday effect in a chiral and achiral ensemble has shown the presence of dynamic magnetisation and second order orientational rise/fall transients due to the conjugate product of a circularly polarised visible frequency laser pulse. Neither effect is known analytically, and the simulated transients are potentially directly comparable with experimental data using modified Kerr effect apparatus.

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