1. Calculate the solar collectors area needed to heat a 50 m² swimming pool given that measured velocity at a height of 0.3 m is 0.5 m/s, water temperature is 22 °C, ambient temperature is 10 °C, sky temperature is at 4 °C, make up water is at 8 °C, the incident solar irradiation per unit area per day is 12 MJ, a = 0.85, the efficiency of collector is 70%, and from steam tables: Pw = 3.166 kPa, 1.22 kPa, and hfg = 2442 kJ/kg Pa =