Experimental investigation of surface roughness effects on flow behavior and heat transfer characteristics for circular microchannels |
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Institution: | National Key Laboratory of Science and Technology on Aero-Engine, Beihang University, Beijing 100083, China; Collaborative Innovation Center for Advanced Aero-Engine of China of Aerodynamics, Beihang University, Beijing 100083, China |
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Abstract: | This paper experimentally investigates the effect of surface roughness on flow and heat transfer characteristics in circular microchannels. All test pieces include 44 identical, parallel circu-lar microchannels with diameters of 0.4 mm and 10 mm in length. The surface roughness of the microchannels is Ra=0.86, 0.92, 1.02 lm, and the Reynolds number ranges from 150 to 2800. Results show that the surface roughness of the circular microchannels has remarkable effects on the performance of flow behavior and heat transfer. It is found that the Poiseuille and Nusselt num-bers are higher when the relative surface roughness is larger. For flow behavior, the friction factor increases consistently with the increasing Reynolds number, and it is larger than the constant the-oretical value for macrochannels. The Reynolds number for the transition from laminar to turbu-lent flow is about 1500, which is lower than the value for macrochannels. For the heat transfer property, Nusselt number also increases with increasing Reynolds number, and larger roughness contributes to higher Nusselt number. |
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Keywords: | Circular Flow behavior Heat transfer Microchannels Roughness |
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