A proposal is made to use a geothermal supply of hot water to operate a steam turbine, as shown in Fig. P4.125. The high pressure water at 200 lbf/in.^2, 350 F, is throttled into a flash evaporator chamber, which forms liquid and vapor at a lower pressure of 60 lbf/in.^2. The liquid is discarded

Question

A proposal is made to use a geothermal supply of hot water to operate a steam turbine, as shown in Fig. P4.125. The high pressure water at 200 [latex]lbf / in .^{2}[/latex], 350 F, is throttled into a flash evaporator chamber, which forms liquid and vapor at a lower pressure of 60 [latex]lbf / in .^{2}[/latex]. The liquid is discarded while the saturated vapor feeds the turbine and exits at 1 [latex]lbf / in .^{2}[/latex], 90% quality. If the turbine should produce 1000 hp, find the required mass flow rate of hot geothermal water in pound-mass per hour.

Accepted Answer

Separation of phases in flash-evaporator constant h in the valve flow so

Table F.7.3: [latex]h _{1}=321.8 Btu / lbm[/latex]

[latex]h _{1}=321.8=262.25+ x imes 915.8[/latex]

[latex]\Rightarrow x =0.06503=\dot{ m }_{2} / \dot{ m }_{1}[/latex]

Table F.7.2: [latex]h _{2}=1178.0 Btu / lbm[/latex];

Table F.7.1: [latex]h _{3}=69.74+0.9 imes 1036=1002.1 Btu / lbm[/latex]

[latex]\dot{ W }=\dot{ m }_{2}\left( h _{2}- h _{3} ight) \quad \Rightarrow \quad \dot{ m }_{2}=\frac{1000 imes 2545}{1178.0-1002.1}=14472 lbm / h[/latex]

[latex]\Rightarrow \quad \dot{ m }_{1}=222539 lbm / h[/latex]

Notice conversion 1 hp = 2445 Btu/h from Table A.1

Question 4.203E: A proposal is made to use a geothermal supply of hot water t...

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