A 10 m2 system for solar water heating consists of absorber tubes and a mixing tank. Water at T1 = 20C enters the absorber tubes at a constant flow rate of m1 = 50g/s. The absorber tubes transfer 60% of incident solar irradiation to the water. The incident solar irradiation is qsun = 1000W/m2. Water exiting the absorber tubes then enters the mixing tank where it is mixed with water entering the tank at T3 = 30C and m3 = 5 kg/s. Assume the average boundary temperature of the tubes is 27C and the reference conditions are T0 = 25C and p0 = 101.3 kPa. Approximate liquid properties with saturated liquid properties.
Question:
a) Calculate the temperature of the water exiting the absorber tubes
b) Calculate the rate of exergy transfer accompanying the heat transferred from the absorber tubes to the water
c) Calculate the amount of exergy destroyed in the absorber tubes
d) For the mixing tank, calculate the temperature of the exiting water and the rate of exergy destruction.