Experiments were carried out to investigate the pressure drop and heat transfer behaviors of a microchannel condenser. The effects of gravity on the condensation of steam in the microchannels were investigated for both horizontal and vertical cases. For the experimental results, the pressure drop of vertical microchannels in the condenser is lower than for horizontal microchannels. In the case of the horizontal microchannel, as the mass flow rate of steam increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 1.5 kPa to 50 kPa, respectively. While the mass flow rate of steam in the vertical microchannel case increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 2.0 kPa to 44 kPa, respectively. This clearly indicates that the gravitational acceleration affects the pressure drop. The pressure drop of the vertical microchannel is lower than that obtained from the horizontal microchannel. In addition, the capacity of the condenser is the same in both cases. This leads to the performance index obtained from the vertical microchannel condenser being higher than that obtained from the horizontal microchannel condenser. These results are important contributions to the research on the condensation of steam in microchannels.

Abstract. The heat transfer characteristics of a microchannel condenser in the phase change from the vapor phase to the liquid phase depend on many factors such as the physical parameters of the working fluid, the cooling fluid, etc. In this paper, the numerical results are clearly presented for the condensation profile, the density change, and the temperature of condensed water. Based on the results in this study, a function was suggested for predicting a relationship between the temperature of condensed water and the mass flow rate of steam from 0.01 g/s to 0.1 g/s. Moreover, the results of numerical simulation are in good agreement with the experimental data. In addition, the results showed that the condensation profile is not strongly affected the gravitational force.

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