Condensation characteristics of a propylene loop heat pipe working in 193 K-283 K

A cryogenic loop heat pipe (CLHP) is an effective means of temperature control at low temperatures. However, the physical properties of cryogenic working fluids are quite different from those of room-temperature working fluids, and their phase change and heat transfer characteristics need to be further studied. In this paper, a test system for evaluating the loop heat pipe’s (LHP) heat transfer performance and visualizing the condensation phenomenon in the condenser was fabricated. The performance of a propylene LHP under 10 W of heating power was tested as the condenser temperature was varied from 283 to 193 K, and the flow patterns and heat transfer characteristics during condensation were obtained. The experimental results show that with decreasing condenser temperature, the length of the two-phase region decreased, and the main flow patterns of LHP with low power include stratified, wavy and slug flow. The comparison with the heat transfer correlation shows that Cavallini correlation can predict the condensation heat transfer coefficient well.