Experimental Investigation of Foam-Phase Change Material Interactions for Thermal Energy Storage
High-density electronics and avionics such as Insulated gate bipolar transistor (IJBTs) and transistors, as well as vehicles themselves, generate excess heat, which must be dissipated to prevent overheating and failure. Phase change materials (PCMs) both rapidly dissipate heat through melting and can store this useful thermal energy for future use. The effectiveness of PCMs is limited by low thermal conductivity, thus, high conductivity metal foams are often introduced to improve the thermal storage performance. In the first part of this thesis, the melting and solidification behavior of a phase change material in a single millimeter-scale cavity is investigated with high resolution infrared (IR) microscopy and compared to numerical models. In the second part of this thesis, the melting and solidification behavior of PCM embedded in commercially available metal foams is explored with high-resolution infrared microscopy. The primary objective of the first experiment is to experimentally evaluate melting and solidification in small individual pockets of phase change material. In particular, we investigated phase change dynamics in cylindrical cavities of varying diameter. The melt/solidification front was tracked and radial temperature distribution curves were obtained to understand phase change in small pockets. This is a precursor to the study of phase change in foams with multiple pores. In the second part, IR microscopy directly observes the impact of foams on the phase change process. Since this work concentrates on heat recovery, more attention is given to the solidification behavior than to the melting behavior. The interface between the foam and PCM is closely observed to understand the thermal interaction between the solid high thermal conductivity scaffold and the phase change material. The foams significantly reduce the solidification times by approximately a factor of 3 due to localization of phase change within the pores and the high effective thermal conductivity of the composite which aids in efficient heat spreading. Decreasing the pore size (increasing the pores per inch within the available range) has little effect on the phase change time. Ultimately, this work provides new insight into the phase change dynamics assisted by high conductivity metal foams for better heat spreading which ultimately will enable the design of better, more efficient thermal storage systems with improved phase change response
Marconnet, Purdue University.
Thermodynamics|Materials science|Mechanical engineering
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