Phase change material based heat sink for thermal management of electronic devices

Abstract

The present dissertation reports the theoretical and experimental studies on the thermal behavior of phase change materials (PCMs) during the melting and solidification process. The objective of the present investigation is to identify the best PCMs for thermal management application and study the thermal performance of PCM-based heat sinks with different thermal conductivity enhancers for thermal management of electronic components. Initially, multi attribute decision making (MADM) technique is proposed to obtain the optimal PCM for the thermal management of electronic components. Three MADM techniques, namely technique for order of preference by similarity to ideal solution (TOPSIS), fuzzy TOPSIS, and VIKOR, are employed to estimate the best PCM. The analytic hierarchy process (AHP) method is employed to obtain the weight of the attributes used for PCM selection. Different types of PCMs, namely organic, inorganic, and eutectics with their important attributes as applicable for thermal management systems, are pre-screened for the analysis. Based on their properties, thirty PCMs and eleven attributes are considered for the analysis. The results show that MADM techniques such as TOPSIS, fuzzy TOIPSIS, and VIKOR can be used for the optimal selection of PCM. In addition, thermal performance of various heat sink configurations involving different numbers of cavities (1, 4, 9, 16, 25, and 36), formed by cross plate fins arrangement, as applicable to thermal management of electronic components, are studied numerically by employing pressure-based finite volume method. Here, the mass and thermal capacity of each PCM-based heat sink configuration is kept the same for all the cases. The performance of various heat sink configurations is evaluated based on the transient temperature variation of the heat sink base, PCM melt fraction, average Nusselt number, and energy absorbed by PCM through both latent and sensible heat. The study also investigates the effect of various PCM materials on the thermal performance of heat sinks. The performance of the heat sink is found to increase with the increase in number of cross fins. Efforts have also been made to investigate the hollow fins filled with PCM to characterize the heat transfer performance. Furthermore, a test facility has been developed to evaluate the heat transfer performance of PCM-based heat sinks for thermal management of the electronic device. Tests are carried out to investigate the thermal performance of various PCM-based heat sinks involving without and with parallel plate fins, cross plate fins, circular pin fins, and square pin fins. Efforts have been made to incorporate copper oxide nanoparticles in PCM to estimate the effect of nano-enhanced PCM (NePCM) on thermal performance. In addition, the thermal performance of heat sinks is estimated with foam-PCM composite; both metallic (copper) and non metallic (carbon) foam are used in the analysis. Effect of various input parameters such as heat flux, the volume fraction of thermal conductivity enhancer (TCE), the volume fraction of PCM, mass fraction of nanoparticles, and set point temperature (SPT) on the thermal performance of various heat sink configurations are studied through experimental investigation. Enhancement ratios are obtained for various heat sink configurations. The performance of various heat sinks is compared. It is found that the heat sink with carbon foam (CF)-PCM composite can be utilized for the effective cooling of electronic components. Keywords: Thermal management, thermal energy storage, phase change materials, melting/solidification, melt fraction, heat sink, enhancement ratio, set point temperature, foam-PCM composite, nano-enhanced phase change material.