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Steam flows in a reducing valve: What diameters of inlet and outlet pipes is required?

Steam flows into a reducing valve with a pressure of 1400kpa+ dryness fraction ).98. It leaves the valve with a pressure of 150kpa. What diameters of inlet and outlet pipes would be required for a flow of 2270kg per hour with a velocity of 15m/s both before and after the reducing valve? Assume no losses+ enthalpy per kg steam before throttling = enthalpy after. Assume also that the specific heat of superheated steam at 150kpa is 2KJ/deg celsius.

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Because dryness = 0.98
and mass rate:
dM/dt = 2270/3600 = 0.63 kg/sec
therefore pure vapour = 0.63 * 0.98 = 0.617 kg/sec
and pure liquid = 0.63 * 0.02 = .013 kg/sec
therefore, discharge at 1400 kPa ( specific volume taken from steam table):
dV/dt = Qi = (0.14073 * ...

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