A Heat Exchanger Is Used to Heat Cold Water at 8°C

Multiple Choice

A heat exchanger is used to heat cold water at 8°C entering at a rate of 1.2 kg/s by hot air at 90°C entering at rate of 2.5 kg/s. The heat exchanger is not insulated, and is loosing heat at a rate of 28 kJ/s. If the exit temperature of hot air is 20°C, the exit temperature of cold water is (use constant specific heats at room temperature)

A) 43.1°C
B) 48.6°C
C) 78.0°C
D) 37.5°C
E) 27.5°C