An Analytical and Experimental Model for a Thermosyphon That Employs Solid/Liquid Phase Change Materials

2000 ◽  
Author(s):  
A. G. Agwu Nnanna ◽  
Kendall T. Harris ◽  
A. Haji-Sheikh
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Phase Change ◽  
Analytical Method ◽  
Practical Importance ◽  
Melting Process ◽  
Passive Cooling ◽  
Efficient Design ◽  
Quick Method ◽  
Solid Liquid

Abstract Application of solid/liquid phase change material (PCM) for passive cooling of electronic modules is on the increase. A simplified method of predicting the thermal performance of passive cooling systems is needed for efficient design of thermal storage systems. This paper presents an experimental and approximate analytical method for quick estimation of the rate of thermal transport in solid/liquid PCM during and after the melting process. However, the emphasis of this paper is on the transport phenomena after the melting process is completed. This research is motivated in part by the need for a simplified analytical method of predicting the rate of heat transfer in buoyancy-driven fluids within a partitioned enclosure, and the need for a fundamental understanding of the rate of heat transfer in liquid melt after the phase change phenomena. These needs are of practical importance for efficient design of a thermal energy storage system. The approximate analytical model serves as a quick method of studying the performance of a thermosyphon system.

Macroscale modeling of solid-liquid phase change in metal foam/paraffin composite: Effects of paraffin density treatment, thermal dispersion and interstitial heat transfer

2020 ◽  
pp. 1-32
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Phase Change ◽  
Equilibrium Model ◽  
Metal Foam ◽  
Thermal Dispersion ◽  
Dispersion Effect ◽  
Solid Paraffin ◽  
Solid Liquid ◽  
Non Equilibrium

Abstract This work focuses on macroscale modeling of solid-liquid phase change in metal foam/paraffin composite (MFPC), addressing the treatment of paraffin density (under distinct paraffin filling conditions in metal foam), thermal dispersion effect and influence of thermal diffusion dominated interstitial heat transfer. To this end, a macroscale thermal non-equilibrium model for melting in MFPC with fluid convection is developed by employing the enthalpy-porosity technique and volume averaging approach. Meanwhile, visualized experiments on melting of MFPC sample are carried out to validate the modeling results. Comparing the numerical modeling and experimental visualization results, it is found that for MFPC with an initially saturated filling condition in metal foam using solid paraffin, the varied paraffin density is preferred to be employed for developing accurate phase change model. However, for MFPC that can be just filled with liquid paraffin after melting (i.e., non-saturated filling condition using solid paraffin), Boussinesq approximation is preferred to achieve satisfying phase change simulation. Thermal dispersion effect in MFPC is proved to be negligible, which should not be overvalued to avoid inducing physical distortions of heat transfer and fluid flow. Consideration of diffusion dominated interstitial heat transfer in the thermal non-equilibrium model is vital to accurately capture phase interface evolutions as well as to reasonably simulate the mushy zone of paraffin; and the model only incorporating the convection induced interstitial heat transfer will predict quite inaccurate phase change process. This study can provide useful guidance in macroscale modeling of phase change in MFPC.

Sign in / Sign up

Export Citation Format

Share Document