Experimental study on the thermo-hydrodynamic characteristics of a nitrogen pulsating heat pipe

Abstract

A simultaneous thermal and visual experiment is conducted on a silicon-based flat-plate nitrogen pulsating heat pipe (PHP) for the first time. The PHP operates successfully with six filling ratios (FRs) between 25% ∼ 76% under bottom heating mode. Start-up and quasi-steady state performances are analyzed. Two types of start-up processes induced by bubble nucleation and interface evaporation are observed, and different start-up mode results in different degrees of thermal performance hysteresis phenomenon. The optimal thermal resistance with different FRs is always lower in a lower FR working condition, but a lower FR results in a lower heat transfer limit. The optimal FR rises with increasing heat load range. The fluid flow data are quantified in two aspects, which are flow intensity and velocity, and coupled with the heat transfer data for analysis. It is inferred that the latent heat transfer efficiency in the nitrogen PHP is higher than that of the sensible heat transfer.