Refrigerant Droplet Size Measurements in Conjunction with a Novel Method for Improving Flow Distribution in Evaporators

Maldistribution of two-phase flow in evaporators is known to significantly affect their performance. To reduce refrigerant maldistribution, a pressure-swirl atomizer is used to distribute R-134a in the header of a typical evaporator. A phase-doppler particle analyzer is used to characterize the spray along the centerline of the header for 1, 2, and 3 g/s total mass flow rate. The thermodynamic quality is varied in the header from 0% to 15%. The centerline droplet size is found to decrease with increasing quality and to decrease with increasing distance downstream of the nozzle. Flow distribution is found to be more uniform when the atomizer is used as the expansion device when compared to a typical expansion valve and pipe inlet.