Experimental Study on a Multi-Evaporator Loop Heat Pipe with a Dual-Layer Structure Condenser

A loop heat pipe (LHP) is a kind of passive heat transfer device that uses the latent heat of the working fluid and the capillary forces of the capillary wicks. It demonstrates high heat transfer efficiency, long-distance heat transfer, and high pipeline flexibility. The multi-evaporator loop heat pipe (MeLHP) is a special loop heat pipe with multiple evaporators so that heat collection and emission from multiple heat sources can be achieved. In this paper, a new type of the multi-evaporator loop heat pipe prototype with a dual-layer condenser was designed, which can ensure the uniform and symmetrical layout of pipelines. The working temperature was 20 degrees C, and propylene was used as the working fluid. The performance of the same evaporator in a single-loop LHP was considered as a reference. The experiment was conducted under two heating modes, i.e. single-evaporator heating and multi-evaporator heating, and the working stability of the prototype was verified by applying periodic heating power change and adverse elevation condition. It was observed that the prototype can be successfully started in different heating modes with a heat transfer limit of 230 W. In the test, the four loops were different in heat transfer limit due to the differences of flow resistance, and less power distribution to the loop with lowest heat transfer limit was considered to be beneficial to the prototype's performance. Meanwhile, the prototype showed good heat sharing characteristic as the maximum temperature difference is low (smaller than 2 K in single-evaporator heating mode and 0.5 K in multi-evaporator heating mode). The prototype was of good operational reliability and found to be adaptable to the adverse elevation and cyclic variation of the heating power to a certain extent.