Fabrication of nano-copper surfaces by thermal evaporation technique to investigate nucleate pool boiling heat transfer performance of R-141b

Abstract

In the present work, nano-Cu particle coatings, which were fabricated on a bare Cu surface using various thickness coating through a thermal evaporation technique, were used as heating surfaces to study the pool BHT performance of refrigerant R-141b. The heating surfaces, viz, 50 nm, 100 nm, 150 nm, and 200 nm thick nano-Cu particle coated surfaces over bare Cu heating surface are used in this experimentation. To reveal the formation of crystal structure on coated surfaces, scanning electron microscope (SEM) was used. Electron Discharge Spectroscopy (EDS) technology was employed to measure the percentage distribution of elements in the coating surfaces. Maximum heat transfer coefficient (HTC) enhancements of 10.5%, 15.7%, 26.6%, and 45.2% are observed for all the coated surfaces of thicknesses of 50 nm, 100 nm, 150 nm, and 200 nm when compared with bare Cu surfaces. Increases in HTC in nano-Cu coated surfaces were attributed to creation of high-density active nucleation sites and enhanced surface roughness. Other published data were used to predict the experimental data, with some deviations observed in the HTC. Thus, this paper is expected to gain importance due to the development of surface engineering with respect to energy conversion management and heating applications.