Assessment of heat transfer and flow characteristics of a two-phase closed thermosiphon

摘要

In this study, comprehensive modeling and simula-tions were developed and carried out to perform the investigation of the thermal performance of the en-closed thermosiphon through pool boiling in the evaporator sector and the condensation of the liquid film in the condenser part. To simulate these phe-nomena, the volume of fluid model was utilized. The simulation modeling using the computational fluid dynamics (CFD) technique was validated with exist-ing experimental results, and a good agreement was reached. The simulation results were presented and evaluated in terms of temperature profiles and con-tours, the volume of fraction contours, and velocity vector distribution. Moreover, the thermal perfor-mance (ie, the heat transfer coefficient and thermal resistance) through the thermosiphon operation was analyzed. From the simulation results, it is found that the thermosiphon performance can be improved by the tilt angle and fill ratio. The results indicated that the optimal performance (ie, a high heat transfer coefficient and a low thermal resistance) was attained at a power input of 250 W, tilt angle of 90°, and fill ratio of 0.5. The established CFD simulations effec-tively predicted the formation of two-phase flow pattern and boiling and condensation zones with water at a low power input, termed as geyser boiling.