Abstract:

An experimental investigation of vertical out-tube falling film heat transfer with different inlet spray densities of ammonia water mixture and inlet hot water temperatures was conducted. The falling film evaporator had a total height of 6000mm and the cycling working fluids were high concentration 60% and 50% ammonia water. We mainly studied the influence of spray density and inlet temperature of hot water on heat transfer coefficient，ammonia vapor amount and evaporation pressure. The experiment showed that heat transfer coefficient and ammonia vapor amount increased first and then decreased with increasing inlet spray density. The higher the hot water temperature，the higher the evaporation pressure. Heat transfer coefficient increased lineany with increasing hot water temperature. The experimental heat transfer coefficient of ammonia water solution was significantly higher than that of water reported in literature. For 50% water，optimum spray density was between 0.2200 and 0.2500 kg/(m·s)；for 60% ammonia water，optimum spray density was between 0.2600 and 0.2900 kg/(m·s). In this experiment，heat transfer performance of 60% ammonia water was better than 50% ammonia water.