Thermal performance of a novel helically coiled oscillating heat pipe (HCOHP) for isothermal adsorption. An experimental study

The results showed there were critical heat fluxes which varied with heat input amount at the evaporator, beyond which dry-out commenced and thermal resistance increased. These heat fluxes were ≤70W for the ethanol HCOHP and ≤105W for both the methanol and deionized water HCOHPs. Performance instabilities owing to liquid phase of the working fluid transitioning in the drying-out stage was observed for the methanol HCOHP beyond 234W. The variation of the effective thermal conductivities at the evaporators were found to influence the thermal contact resistance experienced at the contact interface of integration and the maximum heat input amount at the evaporators. Optimum performance between the HCOHPs was observed with the deionized water type. Overall, the HCOHPs were capable of managing relatively large amounts of heat input due to their helically coiled sections creating comparatively larger evaporator sections holding relatively more working fluid than the conventional serpentine single turn closed loop OHP system of the same volume and fill ratio. Investigations involving the visualization of the internal flow dynamics is recommended for future studies.