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You have access to two sources of energy that can be used to turn a steam turbine in a heat engine (a steam turbine is a device that converts thermal energy into mechanical work):
1. Superheated steam at 400°C and 20 bar
2. Superheated steam at 600°C and 20 bar
Which of these two energy sources can be converted into more mechanical work per unit mass of flowing steam in a heat engine? You may assume that each steam source will leave the turbine at 200°C and 1 bar.

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xero099

Answer:

Option 2.

Explanation:

A turbine produces mechanical work at the expense of fluid energy, that is to say according to the First Law of the Thermodynamics:

[tex]w_{out} = h_{in}-h_{out}[/tex]

The conditions at inlet and outlet are, respectively:

Inlet - Option 1 (Superheated Steam)

[tex]h=3248.4\,\frac{kJ}{kg}[/tex]

Inlet - Option 2 (Superheated Steam)

[tex]h=3690.7\,\frac{kJ}{kg}[/tex]

Outlet (Superheated Steam)

[tex]h = 2875.5\,\frac{kJ}{kg}[/tex]

The mechanical work per unit mass of each option is determined hereafter:

[tex]w_{out, 1} = 3248.4\,\frac{kJ}{kg} - 2875.5\,\frac{kJ}{kg}[/tex]

[tex]w_{out, 1} = 372.9\,\frac{kJ}{kg}[/tex]

[tex]w_{out, 2} = 3690.7\,\frac{kJ}{kg} - 2875.5\,\frac{kJ}{kg}[/tex]

[tex]w_{out, 2} = 815.2\,\frac{kJ}{kg}[/tex]

The second option offers more mechanical work per unit mass.

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