An investigation into a falling film type cooling tower

A model for a falling film type cooling tower has been developed to investigate the effect of tower parameters as well as the effect of liquid-side thermal resistance on the tower performance. The energy equation is used to determine the temperature distribution across the liquid film. The heat and mass transfer processes between the liquid film and air bulk are described using three ordinary differential equations. The energy equation was solved using a finite difference Crank-Nicolson scheme. The heat and mass transfer equations were solved using the Runge-Kutta method. The results obtained show that an increase in tower characteristic K alpha V/L under the same conditions improves the tower performance. The converse is true in the case of increased water to air mass flowrate ratio, L/G. The Lewis number, Le, shows no significant effect on the tower performance. The effect of tower parameters as well as the water inlet temperature on the liquid-side Nusselt number and the tower effectiveness was also studied. The results show very insignificant changes in Nusselt number, whereas the effectiveness increases with increasing K alpha V/L and reduces with L/G, but very insignificant changes occur with Le. The present model is also compared with Merkel's equation. Under the same conditions and with Le equal to unity, the results of the Merkel equation shows a smaller approach than that obtained by the present model.