Implementation of metal-based microchannel heat exchangers in a microrefrigeration cycle, and numerical and experimental investigation of surface roughness effects on flow boiling

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2015
Jafari Khousheh Mehr, Rahim
A microscale vapor compression refrigeration cycle has been constructed for possible application in the thermal management of compact electronic components. The micro-evaporator and micro-condenser components have been fabricated using wire electron discharge machining and micromilling, respectively. Three microevaporators have been manufactured with different surface roughness for the experimental and numerical investigation of roughness effect on nucleate flow boiling in microchannels. In the numerical part of the study, two different techniques have been employed to simulate the evaporation in the microchannels. Firstly, the Arbitrary LagrangianEulerian Method is used to investigate the hydrodynamics and heat transfer vi characteristics of a vaporized elongated bubble, and two successive bubbles in a microtube. Then, phase-field method is utilized, uniquely, for the simulation of saturated and subcooled water boiling in the microchannels with different size of cavities as a preliminary model for the surface roughness. Manufacturing experiments with various process parameters have been conducted to create the different surface roughness values in the oxygen free copper microevaporator channels. In the experimental evaluation part, the hydrodynamics and heat transfer performance of the three microchannel evaporators of the same dimensions and different surface roughness have been compared at variously imposed heat fluxes and mass fluxes. R134a has been used as the refrigerant with saturation temperature of 10 & at mass fluxes of 85 and 200 kg/(m2Âs). The results demonstrated that roughness yields up to 45% enhancement in two-phase heat transfer coefficient at low to moderate heat flux values ranging from 0 to 48 W/cm2.
Citation Formats
R. Jafari Khousheh Mehr, “Implementation of metal-based microchannel heat exchangers in a microrefrigeration cycle, and numerical and experimental investigation of surface roughness effects on flow boiling,” Ph.D. - Doctoral Program, Middle East Technical University, 2015.