Experimental investigation and a new predictive tool for thermal performance of pulsating heat pipes

Abstract

In the present study, binary-fluid-charged uniform and nonuniform flat plate closed loop pulsating heat pipes (FP-CLPHP) are experimentally investigated in comparative manner, and a novel correlation with innovative point of view is derived over a consolidated database. In the experimental process, three different filling ratio (30%, 50%, 70%), three different volumetric mixing ratio (W:M = 1:1, W:M = 1:3, W:M = 3:1) and two different inclination angle (0 degrees and 90 degrees) are taken into consideration. The angles represent the conditions with and without gravity support, and the mixtures are constituted by mixing water (W) and methanol (M). It is concluded that uniform FP-CLPHP cannot operate at horizontal position (0 degrees), while nonuniform design can operate nearly independent from orientation or gravity support. The mixture of W:M = 1:3 provides optimum conditions from the perspective of thermal performance. A new-type-correlation including cross-sectional ratio is proposed in the form of non-dimensional thermal resistance (R-Nth). The mean absolute error of the correlation is 14.7%, and it can successfully predict 90.7% of the experimental data in +/- 30% error band. The correlation directly gives useful information about a FP-CLPHP can work or not work, and how its performance can be improved. The values of R-Nth lower than 0.65 correspond to successful operation of FP-CLPHPs.