680 W/m2.K and that at the condensing zone 5280 W/m2.K. Calculate (a) the mass flow rate of bled steam, (b) the number of tubes, and (c) the pressure drop in the heater. 5. A condensing only feed water heater uses 7/8-in-OD 90-10 copper-nickel tubes. It receives 10.6 kg/s of 95% quality bled steam at 138 kPa and 20 kg/s of drain from the next higher pressure heater at 115 °C. 490 kg/s of feed water goes through the heater at 2 m/sec. 13790 kPa and 90°C. The terminal temperature difference is 2.5 °C. Determine the size, length, and number of tubes based on a U-tube design. Take a maximum allowable design stress in the tubes of 103420 kPa. B.N. estion (1) (8 marks) 10°C Amx4mx5m Strat al A well-insulated 4-m x 4-m x 5-m room initially at 10°C is heated by the radiator of a steam heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 200°C. At this moment both the inlet and the exit Valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 30 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine the average temperature of air in 30 min. Assume the air pressure in the room remains constant at 100 kPa. Question (2) (6 marks)