Performance of nozzle-sprayed ammonia evaporator with square-pitch plain-tube bundle

A spray evaporation experiment was conducted using commercial nozzles distributing liquid ammonia on a horizontal, 3 by 3 square pitch, 1.25 pitch ratio, plain-tube bundle composed of stainless-steel tubes of 0.75 in. (19.1 mm) diameter. The saturation temperature test range was from -10°F (-23°C) to 50°F (10°C), with corresponding pressure from 23.7 to 89.2 psia (164 to 615 kPa). Heat transfer coefficient data were collected within the heat flux range from 1,000 to 11,000 Btu/h·ft² (3.2 to 35 kW/m²). The effects of heat flux, saturation temperature, spray flow rate, nozzle heights, and nozzle type (standard angle or wide angle) were investigated. The spray evaporation heat transfer performance was compared with pool boiling heat transfer performance of the same tube bundle. A correlation was developed based on the spray evaporation experimental data.