Air at atmospheric pressure at a dry bulb temperature of 40d

Air (at atmospheric pressure) at a dry bulb temperature of 40degree C and wet bulb temperature of 20degreeC is humidified with liquid water spray. The difference between the wet bulb and dry bulb temperature (Twb-T) at the exit is 25% of thet at the inlet. The dry bulb temperature at the exit is closest to (in Celsius) (A) 10 (B) 20 (C) 25 (D) 30 (E) 35

Solution

Twb-T=25/100*(20-40)=-5

T=Twb+5=25 (c)