Specific heat capacity of dry air and water vapour are 1.005 and 1.88 kJ kg^-1K^-1, respectively. In an energy conserving system, 1 kg s^-1air at 30 °C with constant absolute humidity of 0.02 kg water (kg dry air)^-1 is heated up to 65 °C. Water at the wet bulb temperature of air is then sprayed into the air so that the final temperature of the air-water vapour mixture is 40 °C. Latent heat of vapourization of water at 70 °C and 40 °C are 2334 and 2407 kJ kg^-1, respectively. The thermal energy supplied per second during heating in kW is