The thermal efficiency of the plant neglecting pump work

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Direction: Consider a steam power plant using a reheat cycle as shown. Steam leaves the boiler and enters the turbine at 4 MPa, 350°C (h₃ = 3095 kJ/kg). After expansion in the turbine to 400 kPa (h₄ = 2609 kJ/kg), the steam is reheated to 350°C (h₅ = 3170 kJ/kg), and then expanded in a low pressure turbine to 10 kPa (h₆ = 2165 kJ/kg) the specific volume of liquid handled by the pump can be assumed to be

The thermal efficiency of the plant neglecting pump work is

1. 15.8%
2. 41.1%
3. 48.5%
4. 58.6%

Correct Option: B

Given: h₁ = 29.3 kJ/kg
h₂ =?
h₃ = 3095 kJ/kg
h₄ = 2609 kJ/kg
h₅ = 3170 kJ/kg
h₆ = 2165 kJ/kg

Turbine work
W_T = (h₃ – h₄) + (h₅ – h₆)
= (3095 – 2609) + (3170 – 2165) =
1491 kJ/kg
Q = Heat input = (h₃ – h₁) + (h₅ – h₄)
= (3095 – 29.3) + 3(3170 – 2609) = 3626.7 kJ/kg
∴ Thermal efficiency of the plant

=	1491	= 41.11%
	3226.7