Refrigerant-134a at 1 mpa and 90°c is to be cooled to 1 mpa and 30°c in a condenser by air. the air enters at 100 kpa and 27°c with a volume flow rate of 640 m3/min and leaves at 95 kpa and 60°c. determine the mass flow rate of the refrigerant. the gas constant of air is 0.287 kpa·m3/kg·k. the constant pressure specific heat of air is cp = 1.005 kj/kg·°c. the enthalpies of the r-134a at the inlet and the exit states are 324.66 kj/kg and 93.58 kj/kg.

Water at 55c flows across a flat plate whose surface temperature is held constant at 95c. if the temperature gradient at the plate's surface for a given value of x is 18 c/mm, find a) local heat transfer coefficient. b) heat flux

Compute the pressure drop of 30°c air flowing with a mean velocity of 8 m/s in a circular sheet-metal duct 300 mm in diameter and 15 m long. use a friction factor, f 0.02, and pair = 1.1644 kg/m a. 37.26 pa b. 25.27 pa n c. 29.34 pa d. 30.52 pa

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]