Fluid Properties of Microencapsulated Phase Change Material Slurries

Electrochemical energy conversion and storage devices are becoming a large part of the renewable energy market. For these systems to operate optimally over a wide range of operating and environmental conditions, advanced strategies for thermal management must be developed. Incorporating microencapsulated phase change materials (MEPCM), which utilize latent heat storage, into coolant fluids has been shown to increase the fluid's thermal capacity. This mitigates the temperature gradient between the coolant loop inlet and outlet which is important in systems such as fuel cells and batteries where sensitivity to temperature directly impacts the electrochemical reaction, transport processes, and component lifetimes. The use of MEPCMs may allow for lower coolant flow rates which may reduce parasitic pumping power, further increasing overall system efficiency. In this work MEPCM material is added to liquid water at several mass concentration ratios, and an analytical study was conducted to determine pressure drop and channel power requirements. The viscosity of the slurry is measured along with its density, conductivity, and heat capacity as a function of temperature. Inlet and outlet channel slurry temperatures are monitored, flow rate is controlled, and the heat flux can be varied to simulate waste heat outputs of various devices. From this data the optimal conditions for the slurry flow can be assessed and thermal management strategies can be designed for specific devices.