Mathematical Modeling of a Miniature Loop Heat Pipe With Two Evaporators and Two Condensers

A loop heat pipe (LHP) analytical model that simulates the steady state and transient thermal behaviors of LHPs with multiple evaporators and multiple condensers has recently been developed. It can be used as a stand-alone computer code or as a subroutine to general spacecraft thermal analyzers. Multi-evaporator and multi-condenser LHPs are more complex in their operation when compared to single-evaporator LHPs because of the thermal and fluid interactions among the evaporators, compensation chambers, and condensers. This analytical model has been used to simulate the thermal performance of a miniature loop heat pipe (MLHP) with two evaporators and two condensers in laboratory and thermal vacuum tests. In addition, the MLHP was tested in the laboratory under five different configurations where the relative elevations and tilts among loop components were varied so as to investigate the gravity effects on the loop performance and to verify the analytical model’s capability to predict such effects. The MLHP performance tests that were simulated included start-up, high power, heat transport limit, and heat load sharing between the two evaporators. In all tests that were modeled, the LHP analytical model accurately predicted the steady state and transient behaviors of the LHP. Furthermore, the model was run-time efficient and yielded stable solutions in all cases.