Effect of number of channels on the fluctuations and distribution of humid-nitrogen condensing flow in a parallel flow field

Pressure drop and flow rate fluctuations of condensation-induced gas–liquid two-phase flow through a single microchannel have been widely recognized, which are quite different from that through parallel-connected multiple microchannels, as in the flow field of proton exchange membrane fuel cells and heat exchangers. This work investigates the effects of the number of channels on the fluctuations of the humid-nitrogen condensing flow and the uniformity of the flow rate distribution across the channels. A parallel flow field with eight channels is designed; the arrangement of these channels is axisymmetric, ensuring identical flow routes and thermal boundary conditions among individual channels. The number of open channels in the flow field could be adjusted from one to eight. The observed pressure drop fluctuated between 0.20 kPa and 0.68 kPa in the single-channel flow field, compared to 0.22 kPa to 0.43 kPa in the two-channel flow field and 0.28 kPa to 0.48 kPa in the eight-channel flow field. This indicates that the amplitude of pressure drop fluctuations decreases as the number of channels increases. In contrast, both the flow rate fluctuation and maldistribution are most significant in the eight-channel arrangement. It is also found that the effect of channel number on condensing flow dynamics is noticeable when both the velocity and humidity of the inlet gas are low.