Question

Steam at 361 kPa and 150°C is condensed at its saturation temperature. What is the temperature of the condensate? How much energy is produced by the process?

Answer 1

(1) Considering 361 kPa as the absolute pressure.

From steam tables:
[Refer to McCab and Smith (Appendix 7: Properties of Saturated Steam and Water)
Convert pressure to Imperial units.
361 kPa = 52.358 lb_f/in²
Use interpolation to find saturation temperature
(57.53-52.358)/(57.53-49.18) = (290-T)/(290-280)
T = 283.8 deg F
T = 139.9 deg C]

Saturation temperature at 361 kPa = 139.9 deg C
The saturation temperature is the temperature of the condensate.

(2) From the saturation temperature, we can clearly see that the steam us superheated.
The superheated steam will first cool to it's saturation temperature. Then it will undergo condensation.

Assuming 1 kg of steam:

From the steam tables:
Enthalpy of superheated steam = 2.75599*10⁶ kJ/kg
Enthalpy of saturated steam = 2733.38 kJ/kg
Enthalpy of saturated water = 588.99 kJ/kg

Superheat removal = (2.75599*10⁶ - 2733.38)
= 2753256 kJ/kg
Condensation = (2733.38-588.99)
= 2144 kJ/kg

Total heat released for 1 kg steam = 2755400 kJ