Water at 10 c enters a thin walled aluminum tube with a diameter of 3 cm at a rate of 2 kg/s. the outer surface of the tube is subject to solar radiation at a rate of 300 w/m. find the required length of the tube for the water exit temperature to reach 90 c assuming that 10% of the radiation energy on the tube is lost to the surrounding.

Air (c-1.006 kj/kg. k, r-0.287 kj/kg. k) enters a nozzle steadily at 280 kpa and 77°c with a velocity of 50 m/s and exits at 85 kpa and 320 m/s. the heat losses from the nozzle to the surrounding medium at 20°c are estimated to be 3.2 kj/kg. determine (a) the exit temperature and (b) the total entropy change for this process. solve this problem using constant specific heats.