A novel flat rectangular evaporator with the optimized heat leakage paths to improve the heat transfer capability of the loop heat pipe

Heat leakage from the evaporator can cause the loop heat pipes (LHPs) to fail to start up or reduce their heat transfer performance, limiting the application of LHPs. To promote the application of LHPs in the thermal management of ground electronics, it is necessary to solve the adverse effects of heat leakage on the heat transfer performance. In this paper, a novel evaporator structure that reduces heat leakage to the compensation chamber (CC) is proposed, while utilizing heat leakage through the shell to extend the heating surface. The evaporator features bifacial heating surfaces sharing the same CC and vapor chamber. It was tested in the horizontal direction to evaluate thermal performance in three different heating modes. When the bottom heat source 1 (HS1) was individually heated. As the heat load increased, the LHP transitioned from a variable thermal conductivity mode to a constant thermal conductivity mode, and finally, the wick approached dry-out conditions, resulting in a sharp increase in the temperature of the heat source. When the top heat source 2 (HS2) was individually heated. The heat transfer performance of LHP was improved and the evaporator inlet temperature remained low. Gravity assisted vapor escaped upwards, maintaining a stable temperature and pressure difference over the wick, enabling the LHP to dissipate a heat load of up to 300 W with the heat source temperature remaining below 80 degrees C. When HS2 and HS1 were simultaneously heated with equal heat load of 80 W. The bifacial heating surfaces of the evaporator switched from a heat extension relationship to a heat sharing relationship, and the difference in the temperature between the bifacial heating surfaces was less than 0.3 degrees C when the LHP was operating stably. Under the same heat load, the thermal resistance of LHP was the lowest when HS2 was individually heated, ranging from 0.536 degrees C/W to 0.216 degrees C/W, and the minimum value was reached at heat load of 250 W.