Testing of a Loop Heat Pipe with Two Evaporators and Two Condensers 2001-01-2190

Most existing loop heat pipes (LHPs) consist of one single evaporator and one single condenser. LHPs with multiple evaporators are very desirable for cooling multiple heat sources or a heat source with large thermal footprints. Extending the current LHP technology to include multiple evaporators and multiple condensers faces some challenges, including operating temperature stability, adaptability of loop operation to rapid power and sink temperature transients, and sizing of the compensation chambers (CCs). This paper describes an overview of an extensive testing program for an LHP with two evaporators and two condensers. Tests performed include start-up, power cycle, sink temperature cycle, CC temperature cycle, and capillary limit. Test results showed that the loop could be started successfully in most cases, and the operating temperature was a function of the total heat load, heat load distribution between the two evaporators, condenser sink temperature and ambient temperature. Under most conditions, only one CC contained two-phase fluid and the other CC was completely liquid filled. Moreover, control of the loop operating temperature could switch from one CC to the other as the test condition changed. In spite of the many factors that could affect the loop operation, the LHP demonstrated very robust operation even when subjected to fast transients.