Analysis of the thermal resistance of a loop heat pipe based on the P-T diagram of the working fluid operating cycle.

A thermodynamic analysis of the operation of a loop heat pipe (LHP) as a two-phase heat transfer device with the circulation of a working fluid in a closed loop due to capillary forces is presented. The conditions for the LHP operation as part of the “heat source - LHP - heat sink” system are formulated. Based on the P-T diagram of the working fluid operating cycle, a graphical interpretation and analysis of the thermal resistance of the LHP and its main components as well as the thermal resistance of the “heat source - LHP - heat sink” system are given. The effect of vapor overheating on the evaporator thermal resistance is demonstrated.