Numerical analysis of loop heat pipe using nucleate boiling model in evaporator core

Loop heat pipes (LHPs) are two-phase heat transfer devices that can transport a large amount of heat over long distances. Owing to their high heat transfer performance, many LHPs have been used for thermal control in spacecraft. Most evaporators in LHPs are cylindrical, and nucleate boiling may occur in the evaporator core. Nucleate boiling in the evaporator core is considered to increase the heat leak from the evaporator to the reservoir and decrease the heat transfer performance of an LHP. However, only a few models can reproduce nucleate boiling in the evaporator core, and the effect of nucleate boiling in the evaporator core has not been quantitatively evaluated. In this study, a new steady-state model that reproduces temperature distribution and nucleate boiling in the evaporator core was developed, and the effect of nucleate boiling in the evaporator core was investigated. First, the calculation results of the model with nucleate boiling were compared with the results of the experiments in which nucleate boiling in the evaporator core was visualized. The calculation results agreed well with the experimental results. A parametric study was conducted to understand the conditions under which nucleate boiling did not occur. The results of the parametric study also showed that when the amount of heat conducted through the wick was small, such as when the thermal conductivity of the wick was low or when the latent heat of the working fluid was high, nucleate boiling did not occur in the evaporator core.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Loop heat pipes (LHPs) are efficient two-phase heat transfer devices widely used in spacecraft thermal control. A new steady-state model was developed to investigate the effect of nucleate boiling in the evaporator core, and the conditions under which nucleate boiling does not occur were identified.