Numerical Simulation on Phase-Change Heat Transfer Within Microencapsulated Phase Change Material

2003 ◽  
Author(s):  
Yu Rao ◽  
Guiping Lin

A source item-based computation model is developed for analysing phase-change heat transfer within Microencapsulated PCM suspending in a flowing carrier fluid to enhance convective heat transfer, with the consideration of phase-change temperature range and varying thermal properties. Solution is obtained by developing a control volume-based finite difference code, in which TDMA method combined with under-relaxation is used to solve a strong nonlinear equation. The code developed for this study can be used for evaluating Microencapsulated PCM suspension and instructing the preparation of Microencapsulated PCM.

Author(s):  
James A. Howard ◽  
Patrick A. Walsh

This paper investigates laminar heat transfer characteristic of two-phase microencapsulated phase change material (MPCM) suspension flows within mini-channels under a constant wall heat flux boundary. Capsules containing paraffin wax with phase change temperature between 35.1°C and 44°C are examined and found to be well suited for electronics cooling applications using liquid cold plate technologies. In particular, it is shown that the large thermal capacity of MPCM slurries around the phase change temperature can lead towards greater isothermality of isoflux systems, a characteristic of significant interest to telecommunication, laser and biomedical applications. The principal focus of the study is to examine heat transfer characteristics within standard tube flow geometries, quantify the heat transfer augmentation/degradation observed and finally, elucidate the mechanisms from which these result. Through the study volume concentrations of the MPCM slurry were varied between 30.2% and 5.03%. High resolution local heat transfer measurements were obtained using infrared thermography and results presented in terms of local Nusselt number versus inverse Graetz parameter. These spanned both the thermal entrance and the fully developed flow regions with inverse Graetz number ranging from 10−3 to 100. Results show that significant heat transfer enhancements are attainable via the use of MPCM slurries over conventional single phase coolants. Overall, the study highlights mechanisms that lead to significant heat transfer enhancements in heat exchange devices employing micro-encapsulated phase change material slurries.


1999 ◽  
Author(s):  
J. C. Mulligan ◽  
D. K. Boyer

Abstract A numerical formulation of the energy equation is developed for the laminar flow of a MEPCM fluid in a tube at a constant velocity and subjected to a constant and uniform wall heat flux. MEPCM fluids are phase-change fluids that are suspensions comprised of particles of microencapsulated phase-change material (MEPCM) in a carrier fluid. The thermodynamic behavior of MEPCM fluids is modeled for both melting and crystallization and included in an enthalpy formulation of the energy exchanges. A particular phase-change case involving a microPCM fluid is then solved for conditions that produce melting and crystallization of the phase-change material. Heat transfer results are presented which show that the MEPCM phase-change characteristics, along with system parameters, have significant effects on the potential of MEPCM fluids to improve heat transfer and facilitate enhanced temperature control in pumped loops.


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