Effects of nozzle configuration on a shell-and-tube spray evaporator with liquid catcher

Abstract

Using R-141b as a coolant, this study investigates the efficiency of impact spray cooling heat transfer in a heat exchanger system comprising a horizontal low-finned tube bundle with a triangular-pitch and a fin count of 1000 fins/m. Each copper tube has a base diameter of 19.1 mm (3/4 in.) and is heated by an electrical resistor. The average heat transfer coefficients are calculated by measuring the mean tube surface temperature and the vapor temperature. Six different nozzle configurations are tested to investigate the effect of the nozzle configuration on the spray evaporation heat transfer performance. It is found that the shell-side heat transfer performance depends significantly on the nozzle orifice diameter, the heat flux rate, and the spray mass flow rate, but is influenced only slightly by the height of the nozzle above the upper row of tubes in the bundle. The dry-out phenomenon is observed as the surface heat flux increases. Under these conditions, the spray cooling heat transfer coefficients are less than those obtained in pool boiling. To overcome the dry-out problem, this study fits liquid catchers beneath each tube. The experimental results show that the heat transfer performance for spray cooling with liquid catchers is superior to that of pool boiling under both low and high heat fluxes. Moreover, the influence of the nozzle configuration on the heat transfer performance is significantly reduced when liquid catchers are attached.