Thermal Vacuum Testing of a Proto-flight Miniature Loop Heat Pipe with Two Evaporators and Two Condensers

Abstract

This paper describes thermal vacuum testing of a proto-flight miniature loop heat pipe (MLHP) with two evaporators and two condensers designed for future small systems applications requiring low mass, low power and compactness. Each evaporator contains a wick with an outer diameter of 6.35 mm, and each has its own integral compensation chamber (CC). Miniaturization of the loop components reduces the volume and mass of the thermal system. Multiple evaporators provide flexibility for placement of instruments that need to be maintained at the same temperature, and facilitate heat load sharing among instruments, reducing the auxiliary heater power requirement.

A review of thermal performance in multiple evaporators loop heat pipe

“…been verified with excellent agreement between the model predictions and the experimental results for the ME-LHP breadboard and proto-flight unit in the laboratory and thermal vacuum environments[15,[39][40]. To the author's knowledge, this is themost specific transient analytical model for ME-LHP in the open literature.…”

“…The evaporator with no heat load can share the heat of other heat-loaded evaporators because the capillary pressure generated in the powered evaporator will drive the vapor flow to the cold and low pressure unpowered evaporator. This is referred to as heat load sharing [39][40].…”

“…The evaporator with a titanium wick showed three times weaker in capillary limit than the evaporator with a nickel wick. The capillary limit tested in open literatures for LHP with two evaporators is 240W in Chang and Nagano [44], 120 W in Ku and Ottenstein [39], 110-140W in Maydanik et al [34], 100 W for miniature 2E-2C-LHP with 8mm evaporator diameter in Habtour [49], 120-140 W for 2E-2C-LHP with evaporator outer diameter of 15mm in Ku [50].…”