Enhancement Of Subcooled Flow Boiling Heat Transfer With Electrodeposited Microporous Coatings

Growing miniaturization of modern-day heat transfer devices has led to the need to have an efficient way of removing high heat fluxes over a very small area. Phase change heat transfer and more so, flow boiling heat transfer has the capacity to remove high heat fluxes over small areas compared to other conventional methods. Many researchers have favored surface modification to enhance flow boiling heat transfer performance. In this work, a two-step electrodeposition technique was used to enhance heat transfer on a plain copper surface.Subcooled flow boiling was investigated over porous copper plates with dimensions 20mm by 20mm fixed into a rectangular channel of dimensions 30mm by 30mm by 300mm. Deionized water was propelled through the channel by means of a pump at flow rates ranging from 3301/h to 5001/h and at three inlet subcoolings:10℃, 20℃ and 40℃. The porous copper plate was fabricated through a two-step electrodeposition process where the first step involved high current densities for a short duration (15sec) and the second stage involved a low current density applied for a longer duration (80min). The wetting characteristics as well as the surface morphology of the porous surfaces were determined using contact angle measurements and SEM imaging respectively. Their performances were compared with that of a bare copper plate.The heat transfer performance of the plates in the nucleate boiling region was enhanced for all the plates compared with the copper plate. An increase in initial current density led to a better performing surface up to the surface made with 1A/cm2, after which it deteriorated. The SEM images indicated there was an obvious change in surface morphology at this point. The CHF of the porous plates deteriorated compared to the reference plate except the plate fabricated with the highest current density (CHF not attained). The reduced wettability of the plates led to the deterioration of CHF.