Design of additively manufactured hybrid PCM-air heat sink with a two-stage channel for enhancing thermal performance

The heat sink combining solid-liquid phase change and cooling fluid is a feasible thermal management method for aerospace electric equipment with the fluctuating cyclic heat load with long duration, to achieve structural weight reduction and miniaturization. Large temperature variation along the flow direction can lead to local overheating, which limits the effect of lowering the maximum temperature of the heating surface by the PCM and results in a reduction of the solidification rate of the melted PCM. In this study, an innovative structural design for a hybrid PCM-air heat sink (HPHS) with a two-stage channel is proposed to enhance temperature uniformity, reduce the maximum temperature, and maximize the solidification rate for a fluctuating cyclic heat load with long duration. The test sample, consisting of one PCM storage chamber and one two-stage channel with one large and four small channels along the flow direction, is fabricated by additive manufacturing. The experimental data are used to verify the validity of the numerical method for simulating the coupled heat transfer of PCM and cooling air. The heat transfer performance of three design schemes including air-cooled heat sink (AHS), HPHS with a single channel, and HPHS with a two-stage channel is studied based on equal pump power. The results show that the presence of PCM significantly reduces the maximum temperature and improves the temperature uniformity of the heating surface for HPHS compared with AHS. The thermal performance of HPHS is further improved by the replacement of a single channel with a two-stage channel. When the PCM melts almost completely at 130 s, an approximate 13.5 degrees C decrease in maximum temperature is obtained, and the difference between the maximum and minimum temperature on the heating surface is also dropped from 15.8 to 3.5 degrees C. Furthermore, the corresponding solidification time of the melted PCM is shortened by 32.34%.