A Mechanistic Model of Two-Phase Pressure Drop in Microchannels (original) (raw)
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As microchannel heat exchangers have become more sophisticated in their design, more exact understanding of the flow inside them is necessary. A decrease in diameter enhances the heat transfer (which takes place at the inner walls of the tubes), but also increases the pressure drop (as the diameter decreases, it becomes like drinking a milkshake through a coffee stirrer). The inclusion of even small amounts of oil in circulation can have a significant effect as well. Historical correlations and studies of two-phase flow have been shown to be insufficient for predicting pressure drops in the smaller channels, due to the different fluid physics that are relevant in flows of small diameter. This study is aimed at understanding the fluid property effects that contribute to pressure drop and flow regime. Two-phase pressure drop data for four refrigerants (R134a, R410A, R290 and R717) were measured in a channel with hydraulic diameter of 148 ¹m. These data were combined with previous two-...
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Evaporators with mini and micro channels are one of the main focuses in the design and development of equipment applied to compact refrigeration systems. The objective of this work is to investigate pressure drop of natural refrigerant, isobutane (R-600a), in the single-phase flow through two small tubes, with 1.0 mm and 2.6 mm of internal diameter. Also, the pressure drop was analyzed in the boiling flow in a 2.6 mm internal diameter tube. The experimental tests included mass velocities of 188, 240, 280 and 370 kg/(m²s), heat fluxes in the range from 0 to 134 kW/m² and boiling flow the saturation temperature of 22 ºC and vapor quality up to 0.8. It was possible to observe the significant influence of the diameter and mass velocity on the total pressure drop and the frictional pressure drop, respectively. The experimental frictional pressure drop in flow boiling in 2.6 mm of internal diameter was compared with four different correlations in literature.
IJERT-CFD Analysis of Fluid Flow and Heat Transfer in Two Phase Flow Microchannels
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/cfd-analysis-of-fluid-flow-and-heat-transfer-in-two-phase-flow-microchannels https://www.ijert.org/research/cfd-analysis-of-fluid-flow-and-heat-transfer-in-two-phase-flow-microchannels-IJERTV2IS80747.pdf This paper presents the computational fluid dynamic Analysis of fluid flow and heat transfer in two phase flow microchannel. In this paper void fraction, pressure drop and heat transfer coefficient is described. The microchannel is of 0.5mm hydraulic diameter and a length of 100mm. The first simulation is done on mass flow rate ranges from 0.1 g/s to 0.4g/s and the 1000 W/ 2 is the uniform heat flux along the length of the microchannel. The temperature at the inlet is the saturation temperature of 30ºC and the pressure at the inlet is atm pressure. The second simulation is done on mass flow rate of 0.5 g/s to 0.8 g/s and 3000 W/ 2 is the uniform heat flux along the length of the microchannel. The temperature at the inlet is again the saturation temperature of 35ºC and atm pressure. The coolant used on both the simulation is the refrigerant R-134a.The simulation results predict the void fraction, pressure drop and heat transfer coefficient in a two-phase flow microchannel. Keywords. Microchannel, two phase flow, void fraction, pressure drop and heat transfer coefficient etc.