Transport in Flat Heat Pipes at High Heat Fluxes From Multiple Discrete Sources

A three-dimensional model has been developed to analyze the transient and steady-state performance of flat heat pipes subjected to heating with multiple discrete heat sources. Three-dimensional flow and energy equations are solved in the vapor and liquid regions, along with conduction in the wall. Saturated flow models are used for heat transfer and fluid flow through the wick. In the wick region, the analysis uses an equilibrium model for heat transfer and a Brinkman-Forchheimer extended Darcy model for fluid flow. Averaged properties weighted with the porosity are used for the wick analysis. The state equation is used in the vapor core to relate density change to the operating pressure. The density change due to pressurization of the vapor core is accounted for in the continuity equation. Vapor flow, temperature and hydrodynamic pressure fields are computed at each time step from coupled continuity/momentum and energy equations in the wick and vapor regions. The mass flow rate at the interface is obtained from the application of kinetic theory Predictions are made for the magnitude of heat flux at which dryout would occur in a flat heat pipe. The input heat flux and the spacing between the discrete heat sources are studied as parameters. The location in the heat pipe at which dryout is initiated is found to be different from that of the maximum temperature. The location where the maximum capillary pressure head is realized also changes during the transient. Axial conduction through the wall and wick are seen to play a significant role in determining the axial temperature variation.

[1]  N. Zhu.  Analytical modeling of the startup characteristics of asymmetrical flat-plate and disk-shaped heat pipes , 2003 .

[2]  Kambiz Vafai,et al.  Analytical modeling of the startup characteristics of asymmetrical flat-plate and diskshaped heat pipes , 1998 .

[3]  Suresh V. Garimella,et al.  Recent Advances in the Modeling and Applications of Nonconventional Heat Pipes , 2001 .

[4]  Amir Faghri,et al.  An analysis of the vapor flow and the heat conduction through the liquid-wick and pipe wall in a heat pipe with single or multiple heat sources , 1990 .

[5]  Yiding Cao,et al.  TRANSIENT TWO-DIMENSIONAL COMPRESSIBLE ANALYSIS FOR HIGH-TEMPERATURE HEAT PIPES WITH PULSED HEAT INPUT , 1991 .

[6]  T. Shimura,et al.  The aluminum flat heat pipe using cyclopentane as working fluid , 2002, ITherm 2002. Eighth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.02CH37258).

[7]  Yvan Avenas,et al.  Silicon heat pipes used as thermal spreaders , 2002, ITherm 2002. Eighth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.02CH37258).

[8]  Qiang Li,et al.  Investigation on transient behaviors of flat plate heat pipes , 2004 .

[9]  M. J. Rightley,et al.  Innovative wick design for multi-source, flat plate heat pipes , 2003, Microelectron. J..

[10]  J. Tournier,et al.  Transient experiments of an inclined copper-water heat pipe , 1995 .

[11]  S. Patankar.  Numerical Heat Transfer and Fluid Flow , 2018, Lecture Notes in Mechanical Engineering.

[12]  Louis C. Chow,et al.  Detailed model for transient liquid flow in heat pipe wicks , 1991 .

[13]  N. Ghoniem,et al.  Vapor Dynamics of Heat Pipe Start-Up , 1991 .

[14]  Suresh V. Garimella,et al.  Transient Analysis of Flat Heat Pipes , 2003 .

[15]  Charles J. Hoogendoorn,et al.  Vapor Flow Calculations in a Flat-Plate Heat Pipe , 1979 .

[16]  Mohamed S. El-Genk,et al.  A heat pipe transient analysis model , 1994 .

[17]  N. Ghoniem,et al.  ANALYSIS OF HEAT PIPE VAPOR DYNAMICS , 1989 .

[18]  C. Tien,et al.  Analysis of the effects of vapor pressure drop on heat pipe performance , 1974 .