Loop heat pipes (LHPs) present the same working principle as for conventional heat pipes, the heat is transferred, from a heat source to a heat sink, by means of the phase change of a working fluid. However, in this case, the liquid and vapor working fluid phases flow in separate tubes, forming a one-direction flow loop so that the evaporator and the condenser can be apart. They have a liquid reservoir, which must be filled with liquid. Another characteristic of LHPs is that the wick structures are mostly concentrated on the evaporator, reducing the internal pressure drop of the device.
Loop heat pipes (LHPs) serve as an effective solution for transferring significant amounts of heat over long distances. Their design optimizes the flow of the working fluid, preventing countercurrent movement between the liquid and vapor phases.