For the same steam power plant as shown in Fig. P4.118 and Problem 4.198E determine the rate of heat transfer in the economizer which is a low temperature heat exchanger and the steam generator. Determine also the flow rate of cooling water through the condenser, if the cooling water increases from

Question

For the same steam power plant as shown in Fig. P4.118 and Problem 4.198E determine the rate of heat transfer in the economizer which is a low temperature heat exchanger and the steam generator. Determine also the flow rate of cooling water through the condenser, if the cooling water increases from 55 to 75 F in the condenser.

Accepted Answer

Condenser: [latex]A _{7}=\pi D _{7}^{2} / 4=0.0491 ft ^{2}, v _{7}=0.01617 ft ^{3} / lbm[/latex]

[latex]V _{7}=\dot{ m } v _{7} / A _{7}=\frac{200000 imes 0.01617}{3600 imes 0.0491}=18 ft / s[/latex]

[latex]q=78.02-1028.7+\frac{18^{2}-600^{2}}{2 imes 25037}=-957.9 Btu / lbm[/latex]

[latex]\dot{ Q }_{ COND }=200000(-957.9)=-1.916 imes 10^{8} Btu / h[/latex]

Economizer [latex]V _{3} \approx V _{2}[/latex] since liquid v is constant: [latex]v_{3} \approx v_{2} ext { and } A_{3}=A_{2}[/latex],

[latex]q = h _{3}- h _{2}=323.0-85.3=237.7 Btu / lbm[/latex]

[latex]\dot{ Q }_{ ECON }=200000(237.7)= 4 . 7 5 imes 1 0 ^{7} Btu / h[/latex]

Generator: [latex]A _{4}=\pi D _{4}^{2} / 4=0.349 ft ^{2}, \quad v _{4}=0.9595 ft ^{3} / lbm[/latex]

[latex]V _{4}=\dot{ m } v _{4} / A _{4}=\frac{200000 imes 0.9505}{3600 imes 0.349}=151 ft / s[/latex]

[latex]A _{3}=\pi D _{3}^{2} / 4=0.349 ft ^{2}, \quad v _{3}=0.0491 ft ^{3} / lbm[/latex]

[latex]V _{3}=\dot{ m } v _{3} / A _{3}=\frac{200000 imes 0.0179}{3600 imes 0.0491}=20 ft / s[/latex],

[latex]q =1467.8-323.0+\frac{151^{2}-20^{2}}{2 imes 25037}=1145.2 Btu / lbm[/latex]

[latex]\dot{Q}_{ GEN }=200000 imes(1145.2)= 2 . 2 9 1 imes 1 0 ^{8} Btu / h[/latex]

Question 4.199E: For the same steam power plant as shown in Fig. P4.118 and P...

Related Answered Questions