Experimental flow boiling heat transfer in a small polyimide channel

Abstract

New experimental flow boiling heat transfer results averaged along a very low thermal conductivity polyimide channel are presented. The experimental setup consists of a horizontal, 300 mm-long, 2.689 mm inner diameter polyimide tube, heated by a counter-current, external water flow. R245fa is the working fluid, at mass fluxes ranging from 100 to 500 kg m-2 s-1 , heat fluxes from 15 to 55 kW m-2 , and three saturation temperatures: 35, 41 and 47°C. Heat transfer coefficient results are presented averaged over the whole polyimide channel for mean vapor qualities ranging from 0.05 to 0.8. High-speed flow visualization was possible downstream of the polyimide tube. Parametric analysis of the results revealed a strong dependence of the heat transfer coefficients on mass flux and vapor quality, and mild influence of the heat flux and the saturation temperature. The experimental database is compared with results obtained for metallic tubes of comparable size in similar experimental facilities. Last, experimental results are contrasted with several heat transfer methods, of which a convective model for annular flow well predicts the heat transfer coefficient values and convective boiling trends.

Development of FEM Calculation Methods to Analyse Subcooled Boiling Heat Transfer in Minichannels Based on Experimental Results

“…The authors of [3] focused on experimental boiling heat transfer during the R-245fa flow in a small circular channel. In the test section, there was a horizontal polyimide tube of 2.689 mm inner diameter and 285 mm long, heated by a counter-current water flow in an annulus around the test tube.…”