4. a). Liquid water at 24oC is fed into a boiler and leaves as saturated steam a

Question

4. a). Liquid water at 24oC is fed into a boiler and leaves as saturated steam at 25 bar. If the heat input to the boiler is 550 kW, calculate the mass and volumetric flow rates of steam produced. Comment on how typically and industrially the heat input to the boiler is generated? b). Determine the temperature at which wet steam at 10 bar and a quality of 80 % can be dried to yield 60 m3/h dry steam. Determine also the enthalpies of the wet and dry process streams, the mass flow rate of steam and the heat input required.

Explanation / Answer

Q = m* (h1 - h2 )

550 = m * (2801 - 100.6)

m = 0.2036 kg/sec = 732.96 kg/h

v = m / 1000 = 0.73296 m3/h

at 10 bar hf = 762.6 kj/kg (wet enthalpy)

h = 762.6 + 0.8 * 2013.6 = 2373.48 kj/kg

v = 60/3600 = 0.01667 m3/s

mass of steam = 16.67 kg/s

Q = 16.67(2373.48 - 762.6 ) = 26.85 KW

h = cp T

2373.48 = 4.2 * T

T = 565 K

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