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Quantity of Heat

Common Data:C...

Question

Common Data:
Consider a steam power plant using a reheat cycle as shown. Steam leaves the boiler and enters the turbine at $4 M P a, 350^{o} C (h_{3} = 3095 k J / k g)$ . After expansion in the turbine to $400 k P a (h_{4} = 2609 k J / k g$ , the steam is reheated to $350^{o} C (h_{5} = 3170 k J / k G)$ , and then expanded in a low pressure turbine to $10 k P a (h_{6} = 2165 k J . k g)$ the specific volume of liquid handle by the pump can be assumed to be

The enthalpy at the pump discharge $(h_{2})$ is

A

0.33 k J / k g

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B

33.33 k J / k g

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C

4.0 k J / k g

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D

33.3 k J / k g

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Solution

The correct option is D $33.3 k J / k g$
Method - I:
Enthalpy at exit of pump must be greater than enthalpy at inlet of pump i.e., $h_{2}$ must be greater then $h_{1} = 29.3 k J / k g$ . Among the given four options only option is greater than $h_{1} = 29.3 k J / k g$ which is $33.3 k J / k g$ . Hence opiton (d) is correct.

Method - II:
Enthalpy at pump discharge $h_{2}$
$= h_{1} + v (p_{2} - p_{1})$
$= 29.3 + 0.0010025 (400 - 10)$
$33.2999 k J / k g$
$= 33.3 k J / k g$

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