Preliminary experimental study of a bio-inspired, phase-change particle capillary heat exchanger

In this study a new cooling concept using encapsulated phase-change particles flowing with water in a parallel-plate mini-channel is presented. This novel concept is inspired by the gas exchange process in alveolar capillaries, where red blood cells (RBCs) flow with blood plasma, yielding very high gas transfer efficiency. Another important characteristic of alveolar capillary blood flow, which is related to the high efficiency of the lungs, is the snug fitting of the RBCs into the capillaries. Hence, preliminary results of experimental tests using particles with diameter similar to the flow channel spacing flowing with water through a heated parallel-plate channel test module are presented and analyzed. The particles are octadecane paraffin (C18H38), a phase-change material, encapsulated in a thin melamine shell. The temperature distribution along the heated surface of the channel is measured for various water flow rates, with and without particles, and with different number of particles. Results are reported in terms of the channel heated surface average temperature and the average heat transfer coefficient, showing a sensible increase (over 20%) in the latter as compared to a clear (of particles) flow. There is strong evidence the increase in heat transfer efficiency to result from a combination of the extra mixing flow effect caused by the presence of particles in the flow and the phase-change effect caused by the EPCM inside the particles.