Thermodynamics - Steam and Two Phase Systems

aali42

Steam at a pressure of 1.25 MN/m² and with a dryness fraction of 0.96 flows through a steam mains of 150mm diameter with a velocity of 26 m/s. The steam is throttled to 0.12 MN/m². After throttling, 5kg of steam is blown into a tank of 98kg water, the original temperature of which is 16ºC. Take the specific heat capacity of steam at constant pressure to be 2.09 kJ/kg K and neglect heat losses.

Determine
(a) mass flow rate of steam through the mains in kg/s
[Answer = 3.04 kg/s]

(b) temperature of steam after throttling
[Answer = 115.1ºC]

(c) temperature of water in the tank after receiving 5kg blown steam
[Answer = 48.54ºC]

STEAM TABLES Extract (Use for solution)

P = 0.12MN/m² , Saturation Temperature = 104.8ºC, hf = 439.4kJ/kg, hfg = 2244.1kJ/kg, Specific volume = 1.478 m³/kg

P = 1.25MN/m² , Saturation Temperature = 189.8ºC, hf = 806.7kJ/kg, hfg = 1977.4kJ/kg, Specific volume = 0.1569 m³/kg