Refrigerant 134a is too accelerated in a steady flow nozzle to a velocity of 250 mpa. At the nozzle inlet the pressure and temperature of the refrigerant are 1.6mpa and 150 degrees celcius and the inlet velocity is neglible. The pressure at the nozzle exit at 0.5mpa. Calculate the heat transfer per unit mass during the expansion if the exit temperature is 50 degrees Celsius.