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tiny-mole [99]
3 years ago
12

Liquid water is fed to a boiler at 24°C and 10 bar is converted at a constant pressure to saturated steam.

Engineering
1 answer:
zepelin [54]3 years ago
4 0

We can find the change in the enthalpy through the tables A5 for Saturated water, pressure table.

For 1bar=1000kPa:

T_{sat}=179.88\°c

H_{fg} = 2014.6kJ/kg

c_p=4.18 kJkg^{-1}{K^{-1}

\nu_g = 0.19436m^3/kg

Replacing,

\Delta h = h_{fg}+c_p(T_{sat}-T_{inlet})

\Delta h = 2014.6+4.18(179.88-24)

\Delta h=2666.17kJ/kg

With the specific volume we know can calculate the mass flow, that is

\dot{m}=\frac{\frac{15000}{3600}}{0.19436}

\dot{m} = 21.4378kg/s

Then the heat required in input is,

Q=\dot{m}\Delta h

Q=21.4378*2666.17

Q=57157.036kW

With the same value required of 15000m^3/h, we can calculate the velocity of the water, that is given by,

V= \frac{\dotV}{A}

V = \frac{\frac{15000}{3600}}{\pi /4 *(0.15)^2}

V=235.79m/s

Finally we can apply the steady flow energy equation, that is

\dot{m}(h_1+\frac{V^2}{2000})+Q = \dot{m}h_2

Re-arrange for Q,

Q=\dot{m}(h_2-h_1-\frac{V^2}{2000})

Q=\dot{m}(\Delta h-\frac{V^2}{2000})

Q= (21.4378)(2666.17-\frac{235.79^2}{2000})

Q= 56560.88kW

We can note that consider the Kinetic Energy will decrease the heat input.

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