Department of Mechanical engineering
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Item Experimental Investigation of Pool BHT Performance of R-141b on Micro/Nano-Porous Copper Coating Prepared by a Two-stage Electrodeposition Method(IEI Conferences, 2021) Belgamwar, Sachin U.Pool boiling heat transfer (BHT) of R-141b on po-rous Cu coated heating surface was experimentally studied. Porous Cu coating was fabricated on a plain Cu heating sur-face through a two-stage electrodeposition method. Surface characterization of Cu coating confirmed the successful syn-thesis of micro/nano-porous Cu coating. Experimental re-sults showed that the Cu coated heating surface introduced a significant enhancement in heat transfer coefficient (HTC) and a great reduction in wall superheat compared to the plain Cu surface. The maximum enhancement in HTC for the Cu coated heating surface was approximately 53% compared to the uncoated heating surface. This is believed to have re-sulted from the increase in active surface area, nucleation site density and cavitation activity owing to the microporous structure of Cu coating. Obtained results showed that the mi-croporous Cu coated heating surface could be employed in modern heat transfer applications.Item Pool Boiling Heat Transfer Performance of R-134a on Microporous Al Surfaces Electrodeposited from AlCl3/Urea Ionic Liquid(Springer, 2022-12) Belgamwar, Sachin U.Development of smart heating surfaces to enhance the performance of pool boiling heat transfer (BHT) has great significance in pool boiling applications. This paper presents the results of a study of improved pool BHT performance of R-134a on horizontal Al surfaces with microporous coating (diameter = 9 mm) at saturation temperature. Microporous Al coatings were fabricated by electrodeposition using AlCl3/urea ionic liquid (IL). The effect of various electrolyte temperatures (30°C, 40°C, 50°C, and 60°C) on the morphology, microstructure, porosity, thickness, and surface roughness of Al coatings was investigated. The pool BHT experiments were performed for increase in the heat flux, varying from 9.51 kW/m2 to 75.14 kW/m2. For the microporous Al coating electrodeposited at an electrolyte bath temperature of 30°C, 40°C, 50°C, and 60°C, the heat transfer coefficient (HTC) value was increased by 58%, 75%, 92%, and 109%, respectively, compared with the bare Al surface. The differences in the HTC augmentation for Al-coated surfaces can be explained by variations in the thickness of the microporous structure and in their surface characteristics such as porosity and surface roughness.Item Pool boiling of R-134a on ZnO nanostructured surfaces: and heat transfer(CRC Press, 2023) Belgamwar, Sachin U.An experimental study was carried out to investigate the pool boiling performance of R-134a onZnO nanostructured heating surfaces. ZnO nanostructured heating surfaces were fabricated by the thermal evaporation technique followed by heat treatment. Nanostructured ZnO thin films were applied on the bare aluminum heating substrate, furthermore pool boiling performance was carried out with R-134a. Experimental data were recorded at heat fluxes ranging from 9.37 to 72.23 kW/m2k. It was found that with a rise in the thickness of nanostructured ZnO thin film, the wall superheat was decreased and the maximum decrement in wall superheat was observed for nanostructure ZnO thin film with 300 nm thickness. It was also observed that the heat transfer coefficient (HTC) of the ZnO nanostructured surfaces increased with the rise in thickness of coating. The highest value of HTC for ZnO-300 surface was61% greater than the bare Al heating surface.Item Pool boiling heat transfer of R-600a on plain copper and Cu@GPL porous composite coating surfaces(CRC Press, 2023) Belgamwar, Sachin U.In this work, nucleate pool boiling experiments were performed on the plain copper and graphene nanoplatelets reinforced Cu matrix (Cu@GPL) porous composite coatings using saturated refrigerant R-600a. The Cu@GPL porous composite coatings were fabricated by a two-step electrodeposition technique. Copper sulfate pentahydrate as a source of Cu and graphene nanoplatelets (GPL) as reinforcing element were used as starting materials for fabrication of Cu@GPL porous composite coatings. The effect of coating parameters such as surface roughness, coating thickness, and porosity on the heat transfer coefficients (HTCs) and boiling characteristics of refrigerants was investigated and presented in detail. The heat transfer coefficient of Cu@GPL porous composite coating was enhanced approximately 2.36 times than that of the plain copper heating surface. The augmentation in the HTCs is primarily due to an increase in surface roughness, coating thickness, porosity and active nucleation of the Cu@GPL porous composite coatings.Item Fabrication of Cu@G composite coatings and their pool boiling performance with R-134a and R-1234yf(Taylor & Francis, 2022-01) Belgamwar, Sachin U.The present work explores the pool-boiling performance of refrigerants (R-134 and R-1234yf) on the plain Cu and graphene nanoplatelets (G) reinforced Cu matrix (Cu@G) composite coated heating surface. A two-step electrodeposition technique was employed to prepare microporous Cu@G composite coatings. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) studies confirmed the successful fabrication of microporous structure of Cu@G composite coatings. Surface profilometer investigation was done to know the surface roughness of prepared Cu@G composite coatings. Pool boiling experiments were carried out with increasing heat flux from 8.80 kW/m2 to 61.25 kW/m2 at a saturation temperature of 10°C. Test results of R-134 and R-1234yf were compared. The experimental results revealed that the heat transfer coefficients (HTCs) of R-134a were higher than R-1234yf for plain Cu and Cu@G composite coated heating surfaces.Item Experimental investigation of pool boiling heat transfer performance of refrigerant R-134a on differently roughened copper surfaces(Elsevier, 2021) Belgamwar, Sachin U.Pool boiling heat transfer of refrigerant R-134a at saturation temperature of 5 °C was investigated experimentally on copper. The effect of surface roughness was studied at various average roughness (Ra) values ranging from 0.130 to 0.274 µm. All experimental samples were vertically oriented, and experiments were carried out at varying heat flux ranges between 10 and 70 kW/m2. The investigations are carried out to calculate the boiling heat transfer coefficient (h), wall superheat (ΔT) and heat flux (q) for different roughness of heat transfer surfaces. The obtained results revealed that the Cu surface with Ra = 0.274 µm showed outstanding heat transfer performance compared to other Cu surfaces. The overall boiling performances enhanced with an increase in roughness value of the heat transfer surface owing to the increased number of cavities.Item Enhancement of Pool Boiling Heat Transfer Performance of R-134a on Microporous Al@GNPs Composite Coatings(Springer, 2022-01) Belgamwar, Sachin U.Pool boiling has been widely employed in electronic, power production and refrigeration systems due to its high efficiency in heat transfer. However, the investigation and application of microporous Al matrix composite coatings to enhance the pool boiling heat transfer (BHT) are very limited. In this study, graphene nanoplatelets reinforced Al matrix (Al@GNPs) composite coatings are fabricated by combining mechanical milling, screen printing and sintering techniques to investigate the pool boiling heat transfer using R-134 as working fluid. The experimental data were obtained at a saturation temperature of 10 °C for heat fluxes ranging from 9.04 kW·m−2 to 73.57 kW·m−2. The effect of various coating thicknesses on boiling characteristics and heat transfer coefficient (HTC) of R-134a were studied and presented in detail. Our results demonstrate that the HTC obtained for Al@GNPs-4 composite coated heating surface is 143% higher than the plain Al heating surface. Enhanced nucleation sites and increased bubble pumping action are the main reasons for the augmented BHT performance on the Al@GNPs composite coated heating surfaces.