Experimental study of nucleate pool boiling heat transfer on microporous structured by chemical etching method

Abstract

Cooling of high heat flux devices and electronics devices with a high heat dissipation system uses Boiling Heat Transfer (BHT). In this paper, a pool boiling heat transfer experiments conducted on saturated distilled water for a bare and microstructured copper surface prepared through chemical etching at atmospheric pressure. A two-step chemical etching process is used for the fabrication of copper microstructure. In the first step, HNO3 and CTAB are used, and in the second step, NaOH and (NH4)2S2O8 are used. This practice comes up with simple management of various surface properties that influence critical heat flux (CHF) and boiling heat transfer coefficient (BHTC) like porosity, roughness, contact angle, etc. These properties are examined with the help of required equipment and are found better. The result of the experiment shows a significant enhancement for BHTC. The maximum BHTC is 82.7 kW/m2K, which is a 60 % increment compared to the bare copper surface. The enhancement of BHTC is due to the microstructure formed on the copper surface through chemical etching. Because of this microstructure, surface properties like roughness, surface wettability are improved in favor of boiling heat transfer performance. But due to the hydrophobic nature, chemically etched surfaces show less CHF than the bare copper surface. For repeatability performance, the surfaces' heat transfer coefficient shows a 4.8 % deviation after a four times repeated test.