Experimental investigation of saturated nucleate pool boiling heat transfer characteristics of R245fa on a copper foam covered surface

Abstract

This paper presents an experimental investigation of saturated nucleate pool boiling heat transfer characteristics of copper foam covered surfaces and plain copper surfaces. Six copper foam covered surfaces with different pore sizes and thicknesses and two plain copper surfaces with different roughnesses were used as the boiling test surfaces, all oriented horizontally. The refrigerant R245fa, which has potential to be used as an electronic coolant, was selected as the test fluid. The saturation temperature for the boiling experiments was about 18.5°C ±1°C. The results showed that the copper foam coating on the plain copper surface effectively increased the boiling heat transfer coefficient by up to 381.7% and the CHF by 196.7 %, while the increased roughness of the plain copper surfaces only slightly improved the heat transfer coefficient. The copper foam covered surface triggered nucleation at lower wall superheats with the ONB (Onset of nucleate boiling) point as low as about 2°C for R245fa on the 0.5 mm thick copper foam covered surface with a pore size of 400 PPI. The increased copper foam layer thicknesses did not further improve the pool boiling heat transfer performance, which closely depended on the relationship between the size of the copper foam pores and the active nucleation sites.