Objective oriented phase change material composite heat sink design

Abstract

While phase change material based heat sinks have been shown to act as highly efficient transient cooling devices, the effective implementation of these components is prevented by a lack of design guidelines. Here, we develop an analytical framework for optimizing the design of rectangular and cylindrical phase change material composite heat sinks. This is accomplished through the definition of two design objectives: (1) maximize thermal buffering capacity at a given time, and (2) maximize the time the system can achieve a minimum thermal buffering capacity threshold. In this context, thermal buffering capacity can be quantified in terms of heat absorption rate or temperature, depending on the boundary condition applied. We demonstrate that, in finite volumes, there exist two design regimes where the thermal buffering capacity is either limited by the rate at which the system can absorb thermal energy or by the total thermal capacitance of the system. We present analytical expressions describing the optimal volume fraction for each combination of design objectives, form factors, and boundary conditions derived from appropriate analytical solutions for the melting problem. Analytically predicted optimal volume fractions are validated with numerical and experimental results from existing literature and original work. This collective toolbox enables thermal engineers to make rational decisions on architecture to optimize components under specific thermal loads and specific system constraints.