查看更多>>摘要：Experiments were conducted to investigate the characteristics of two-phase flow behavior in a horizontal multiport flat tube. A single horizontal smooth multi-port flat tube is used in this paper. The visualization apparatus is set up at the outlet of the heated test section to observe the two-phase flow behavior by a high-speed video camera. Mass flux is in a range from 25 to 200 kg·m~(-2)·s~(-1) and vapor quality is in a range from 0.1 to 0.9. Plug/slug flow regime dominates when mass flux is lower than 100 kg·m~(-2)·s~(-1) while annular flow regime is mainly observed when mass flux is higher than 100 kg·m~(-2)·s~(-1). Besides, the flow regime transitions from plug/slug to annular flows are clearly observed with increasing vapor quality. The relevance between flow pattern and heat transfer characteristics is also discussed.
查看更多>>摘要：In this work, polyvinyl alcohol (PVA) hydrogel has been employed for the fabrication of a heat sink based on evaporative cooling: evaporation of water from the hydrogel's surface causes a cooling effect on the bulk material, which can be used for decreasing the temperature of a stream of hot water flowing through a channel present in the hydrogel. A heat sink (5 cm x 5 cm x 0.5 cm) made entirely of PVA hydrogel was obtained by drop casting and freeze-thaw method. The purpose of this work is to measure the cooling power of the hydrogel heat sink under several conditions and understand its potential as efficient and sustainable cooling device. It was observed that the cooling power could be augmented of +58% by flowing air on its upper surface and it was demonstrated experimentally that the contribution to cooling is mainly related to water evaporation.
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