Experimental study of loop heat pipes with different working fluids in 190–260 K

Abstract

This research evaluated the working fluids for the loop heat pipes (LHPs) at the working temperature of 190–260 K and verified the using of the figures of merit (FOM) to evaluate the working fluids for LHPs. Ethane, propylene and the rarely reported ethylene, were selected as the working fluids. The thermal resistance and heat transfer limits of two geometrical different LHPs under various operating temperatures and heat loads were investigated. The thermal resistances of the LHPs charged with ethylene were lower than those charged with ethane and propylene under the same heat loads, and the thermal resistances decreased as the operating temperature increased, which is consistent with the predicted results of the Joung Parameter. The experimental heat transfer limits of the two LHPs significantly deviating from the predictions using the Dunbar Parameter and the Mishkinis Criterion. This deviation was analyzed and corrected by considering the pressure loss and contact angle in the derivation of the updated FOM. The experimental heat transfer limit of the LHPs are in good agreement with the updated FOM with different contact angles at different temperatures, and the experimental data is overall closer to the theoretical estimation by the updated FOM than the Mishkinis Criterion which indicates errors up to 70%. The Joung Parameter and the updated FOM in this work may help evaluating and selecting a working fluid suitable for the LHP to meet the design goals of low thermal resistances and significant heat transfer limits, respectively.