An experimental study on pool boiling of R-600a on Cu@Gr composite-coated patterned surfaces

Abstract

Two-step electro-co-deposited Cu@Gr composite coatings on patterned surfaces (HSI, HSII, HSIII and HSIV) were used to improve the pool boiling heat transfer performance of R-600a. The pattern design was varied to vary the geometrical parameters, which affected the heat transfer area, capillary action and stable active nucleation sites. These copper patterned surfaces of four different designs (PI, PII, PIII and PIV) were fabricated using wire EDM method, and copper patterned surfaces were integrated with microporous Cu@Gr composite coatings. The experimental results showed that the heat transfer coefficient (HTC) augmented with the increase in heat transfer area. The HTCs of all the Cu@Gr composite-coated patterned surfaces were significantly improved compared with those of the bare Cu surface. The maximum BHT coefficient ratio (hER) belonging to HSI, HSII, HSIII and HSIV was 2.86, 2.99, 3.15 and 3.36, respectively. The improvement in pool BHT can be attributed to the integration of patterned surfaces and microporous Cu@Gr composite coatings contributed to the significant increase in active nucleation sites, more liquid replenishment for surface rewetting and increased heat transfer area.