Experimental investigation on steam flow loss characteristics in microchannels

Abstract

In this paper, experiments were performed to investigate the flow loss characteristics of steam through different microchannels. The microchannels were assembled from stainless steel machined flange assemblies and pipes. The inlet pressure was 20 kPa, and the outlet pressure was adjusted between 5 kPa and 16 kPa (absolute pressure). The steam flow rate in microchannels was obtained by condensing the steam through a condenser coil, and the effects of microchannels of different structures and dimensions on the friction factor were studied by experiment. Experimental results show that the gas flow is not choking, even if the pressure ratio between the inlet and the outlet is as high as 4. In addition, a new correlation between the volumetric flow rate and the pressure difference was derived, and the error between the prediction curve and experimental data is within 20%. Besides, the microchannels’ structure effects on flow loss were investigated. The single most striking observation to emerge from the data comparison was that the gas flow phenomena in grooved channels with different hydraulic diameters were contrary. For microchannels with a hydraulic diameter of 300 µm, higher steam outlet velocities are found when steam flows in specially constructed microchannels. However, the opposite phenomena were observed in microchannels with a hydraulic diameter of 500 µm.