Experimental and numerical study of a falling film heat exchanger used in a vapour absorption refrigeration system

Abstract Falling film evaporators have found applications in a wide range of industries, varying from chemical industries, petroleum refinery, desalination and food process industries. These heat exchangers are preferred mainly because of high heat exchange rates with low temperature difference between the heat exchange fluids at low film fluid flow rates with low evaporation temperature. This study is focused on numerical and experimental investigation of vapour generator (falling film heat exchanger) of a vapour absorption refrigeration (VAR) system. The influence of key operating parameters like mass flow rate of fluid, inlet temperature and the concentration of the thermic fluid as well as the coolant, are experimentally studied and are compared with the numerical results. The deviation between the experimental and numerical results was found to be 8.72%, with a lesser deviation at lower temperatures. The minimum percentage error is 2.15%, for a thermic fluid temperature at 50 °C. There is a stronger agreement in the results for lower values of the glycol water mixture inlet temperature, than at high temperatures. A maximum of 1000 W/m2 heat is transferred to the aqua-ammonia with ammonia concentration of 0.6 by volume is observed for thermic fluid inlet temperatures of 80 °C. The effect of various operating parameters were numerically studied and interpreted. The results obtained were in correlation with the concepts of heat transfer.