Operating characteristics of a flat evaporator loop heat pipe having a flexible heat transport path

In this work, a flat-evaporator loop heat pipe (FELHP) having a flexible heat transport path was constructed and tested. The operating characteristics were investigated in terms of the operating temperatures and various thermal resistances using different working fluids (e.g. ethanol, acetone, and distilled water) and at different elevations. Regarding the effect of the working fluid, acetone showed the lowest thermal resistance at lower heat loads (e.g., 0.25 KW −1 ±0.07 KW −1 at 60 W), whereas the water-filled FELHP resulted in the widest operating range with the lowest thermal resistance of 0.25 KW −1 ±0.05 KW −1 at 320 W. A significant effect of elevation change was observed due to the prevailing hydrostatic head loss over the frictional pressure loss; the lowest thermal resistances at different elevations varied from 0.64 KW −1 ±0.11 KW −1 to 0.11 KW −1 ±0.03 KW −1 with decreasing elevation.