Title: Heat transfer analysis in an electrocaloric refrigeration tube producing large temperature span

Abstract

Electrocaloric (EC) refrigeration is believed to be the next-generation cooling technology due to its low global warming gas emission and high energy utilization. EC materials generate heat and cold capacities that could be alternately utilized under a periodically varying electric field, which needs a heat transfer medium to carry heat. Here we built a simulation model in which the EC material surrounded a tube and microfluid working medium was inside the tube to achieve the utilization of heat and cold capacities. The tube was enclosed between hot and cold ends connecting to a peristatic pump to drive the microfluid. Under a periodical electric field, the EC material generated heat and cold, accompanied by the reciprocating flow of microfluidics, which causes a temperature span between hot and cold ends. In this work, we analyzed the influence of heat transfer between the EC material, tube, and microfluid medium on the cooling performance of the tube. For EC materials, organic P(VDF-TrFE-CFE)-based polymer and inorganic BZT-based EC-active ceramic were studied to find how the thermal conductivity influence the heat transfer processes. As heat transfer between the EC materials and the tube needs a limited time, fluxing velocities of the microfluid and working frequency are also parameters influencing the heat transfer, which were studied in detail. In total, we found how thermal conductivity and working frequency affect the performance of the EC refrigeration tube in this work, and got a largest adiabatic temperature span between hot and cold ends under the specified adiabatic EC temperature change of EC materials.