Experimental evaluations of the critical heat flux in terms of the heater dimensions, orientation, and surface morphology

Abstract

Pool boiling experiments to evaluate the critical heat flux (CHF) have been conducted for decades. Although experimental results for the analyses of a myriad of parameters affecting the CHF have been reported steadily, the CHF results have a large discrepancy between them. This study attempts to acquire reliable CHF data by improving the methodology for pool boiling experiments in a direct heating method. In particular, contact resistance is carefully managed to attain the reliable data in every case of experiments. The experiments are performed with various parameters, namely, heater dimensions, orientation and surface morphology. The dimension effect on the CHF is evaluated with stainless steel heaters with widths of 10, 30, and 50 mm and lengths of 10, 30, and 100 mm. With the suggested size of the heaters for the practical application to real industry, the CHF is evaluated considering a change in the surface process: polishing with sandpaper, wire brushing, and buffing. As a result, unique CHF trends are observed, including CHF deterioration, and surface analyses are conducted using surface analysis instruments. Last, the effects of orientation (0 ~ 180) on the CHF are evaluated, and the results are compared with the extant correlations and experimental data.