Comparison of thermal performances of water-filled, SiC nanofluid-filled and SiC nanoparticles-coated heat pipes

• Effects of SiC nanoparticles on thermal performances of heat pipe were studied experimentally.
• Deteriorated boiling heat transfers were observed in heat pipes with SiC nanoparticles.
• Three types of heat pipes showed similar condensation heat transfer and overall heat transfer.

In the present study, thermal performances of water-filled and 0.01 and 0.1 vol% SiC/water nanofluids-filled heat pipes with a screen mesh wick and water-filled heat pipe with a SiC nanoparticles-coated screen mesh wick were compared in order to investigate the effects of nanoparticles depositions on inner surface structures of heat pipes. The wall temperatures of the SiC nanoparticles-coated heat pipe were found to be higher than those of an uncoated heat pipe while the thermal performance for the heat pipe using a SiC/water nanofluid was not enhanced compared to the heat pipe using water as a working fluid. Also, the heat pipes containing SiC/water nanofluids and SiC-coated wick showed slight increases in evaporator thermal resistances, but minute changes in condenser thermal resistances compared to the water-filled heat pipe. Moreover, the overall thermal resistances of the heat pipes with the SiC/water nanofluids and SiC-coated wick were similar with those of the heat pipe charged with water. In terms of heat transfer performance, the boiling heat transfer of the evaporator zone is explained by changes of the number of activated nucleation sites due to nanoparticle deposition on the wick structure, whereas heat transfer characteristics of the adiabatic and condenser zones are attributed to the liquid film layer which is formed on the wick structure by capillary wicking and is considerable as additional thermal resistance. The SEM images for wicks of heat pipes with nanoparticles-coated layers support the thermal performance characteristics of three types of heat pipes investigated in the study.