Experimental Study on Flow Maldistribution and Performance of Carbon Dioxide Microchannel Evaporator
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The effects of three inlet parameters on flow distribution and performance of a microchannel evaporator are investigated experimentally. The three research factors are evaporation pressure, inlet mass flow rate and dryness. The configuration is made of brazed aluminum microchannel flat tubes with multi-louver fin structure using CO2 as the refrigerant. Those 19 parallel flat tubes are divided into 9 intervals, and 72 temperature measurement points are set. The unevenness standard deviation is adapted to evaluate the unevenness of each interval. It is found that mass flow rate has the greatest influence on the flow maldistribution for a CO2 microchannel evaporator, followed by inlet dryness and evaporation temperature. The position of the inlet header has a great influence on the flow maldistribution of the heat exchanger and its performance. For a CO2 microchannel evaporator, the unevenness of flow maldistribution is reduced when increasing the inlet dryness or decreasing the mass flow rate. Moreover, the inlet dryness has much greater impact on performance than the mass flow rate and evaporation temperature. The CO2 microchannel evaporator is more apt to uneven flow maldistribution when the load is large, which will seriously affect its performance under extreme conditions.
KeywordsMicrochannel evaporator Flow maldistribution Heat transfer distribution CO2
- 4.Choi, J.M., et al. Effects of nonuniform refrigerant and air flow distribution on finned tube evaporator performance. In: International Congress of Refrigeration, pp. 1–8, Washington, D.C., USA (2003)Google Scholar
- 7.Pettersen, J.: TWo-phase flow pattern, heat transfer, and pressure drop in microchannel vaporization of CO2. ASHRAE Trans. (Symp.) 109 (1), 523–532 (2003)Google Scholar
- 10.Habib, M.A., et al.: Evaluation of flow maldistribution in air-cooled heat exchangers. Comput. Fluids 8(3), 655–690 (2009)Google Scholar
- 11.Ducoulombie, M., Colasson, S.: Carbon dioxide flow boiling in a single microchannel-partII:heat transfer. Exp. Thermal Fluid Sci. 35, 595–611 (2011)Google Scholar