Two-phase pressure drop due to friction in micro-channel

Abstract

This paper deals with an experimental investigation to measure the frictional pressure drops for two-phase flow boiling in a micro-channel with a hydraulic diameter of 500 µm. First, the experimental study is performed under the test conditions: heat fluxes ranging from 100 to 400 kW/m2, vapor qualities from 0 to 0.2, and mass fluxes of 200, 400 and 600 kg/m2s. Then, the frictional pressure drop during flow boiling is estimated using two models: the homogeneous model and the separated flow model. The experimental results show that the two-phase multiplier decreases with the increase of mass flux. In addition, the measured pressure drops are compared with those from a few correlation models available for macro-scales and mini/micro-scales. Finally, the present paper proposes a new correlation for two-phase frictional pressure drops in mini/micro-scales. This correlation model is developed based on the Chisholm constant C as a function of two-phase Reynolds and Weber numbers. It is found that the new correlation satisfactorily predicts the experimental data within mean absolute error (MAE) of 3.9%.

Pressure drop characteristics for two-phase flow of FC-72 in microchannel

“…During the two-phase flow boiling in a microchannel, bubbles in bubble flow and slug flow cannot grow normally because they are pressed by channel walls. Therefore, they form elongated slug flow [10][11][12][13][14][15][16][17][18][19][20][21][22] and transforms into annular flow in a lower vapor quality than that in a macrochannel. 13,22 Consequently, it is hard to apply the flow transition criteria developed from macrochannels to the microchannel environment.…”

“…Moreover, some researchers have reported very different results depending on the experimental conditions and the properties of the working fluid. 9,19 It is necessary to confirm the thermal flow characteristics in a microchannel for designing and operating a cooling system by applying the micro-heat-sink technology. In particular, it is essential to precisely predict the magnitude of the pressure drop occurring in a heat sink to calculate the required power.…”

“…Moreover, some researchers have reported very different results depending on the experimental conditions and the properties of the working fluid. 9,19…”

Clogging behavior of an elongated bubble in uniform and diverging microchannel

“…Lim et al. 3 have experimentally measured the pressure drop during flow boiling in a single microchannel and claimed that two-phase friction factor multiplier increases with vapor quality, but reverse effect is seen with mass flux. Rider et al.…”

“…They observed that for low capillary number, the pressure drop across the bubble was equal to the pressure drop across an isolated bubble showing negligible channel confinement effect. Lim et al 3 have experimentally measured the pressure drop during flow boiling in a single microchannel and claimed that two-phase friction factor multiplier increases with vapor quality, but reverse effect is seen with mass flux. Rider et al 4,5 developed an algorithm to track the interface of droplet/bubble using piecewise linear interpolation scheme (PLIC) in volume-offluid (VOF) method.…”