P

The net useful work done is

This means that the net work is exactly that owing to the isothermal expansion of the gas.

Example

Choose pi = 1 MPa and assume that T1 = Tatm = 298 K and p3 = Patm = 0.1 MPa. The expansion ratio, r = p1/p3, is 10:1. The net work per kilomole of "fuel" is 5.7MJ/kmole of N2 or 204kJ/kg of N2.

It may be difficult to achieve isothermal expansion; it would require an additional heat exchanger to warm up the nitrogen as it forces the piston down. However, something similar is required in a Stirling engine, so it is possible.

Let us examine the case of adiabatic expansion that is easier to achieve. If no heat is added during the expansion, the temperature will fall:

Here, y = 1.4 for nitrogen. The work during the expansion is

For the example with p1 = 1 MPa, we get Ts = 154 K and W2s = 3 MJ/kmole.

When the volume, vs, is reached, the gas will have cooled to Ts so that vs = n-3. (3.36)

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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