73. In an open feedwater heater for a steam plant, saturated steam at 7 bar is mixed with

subcooled liquid at 7 bar and 25°C. Just enough steam is supplied to ensure that the mixed

steam leaving the heater will be saturated liquid at 7 bar when heater efficiency is 95%.

Calculate the mass flow rate of the subcooled liquid if steam flow rate is 0.865 kg/s.

Steam properties:

@ 7 bar, saturated vapor: hg = 2763.5 kJ/kg

@ 7 bar and 25°C: hf = 105.5 kJ/kg

@ 7 bar, saturated liquid: hf = 697.22 kJ/kg

A. 2.725 kg/s B. 3.356 kg/s C. 2.869 kg/s

D. 3.948 kg/s