100 200 300

Power output Ibhp) (b)

Fig. 8.6. Performance characteristics ol 4811 kW (360 hp) 4-cyliiider Philips Stirling engine, type 4-S12I0 with hydrogen and helium as the working lluids. Engine speeds were 1200 and request of the Electromotive Division of General Motors for evaluation by the U.S. Navy. The engine, designated the Philips Type 4-S1210, is described in Chapters 12 and 13. Loflus ran the engine first with hydrogen as the working fluid and then with helium. No significant changes were made in the engine parts or experimental set-up. Some of his results with the two working fluids are reproduced in l;ig. 8.6. He found that the engine produced more work at a higher efficiency when running with hydrogen as the working fluid than when running with helium.

Thermophysical properties

What then are the reasons for one gas to be better than another for the working fluid in Stirling engines? The answer lies in what are called the 'transport properties' of the fluid including the viscosity, thermal conductivity. specific heat, and density. Table S.I contains comparative data of these properties for hydrogen, helium, air, and carbon dioxide.

The properties are important in two ways as regards heat transfer and aerodynamic-friction losses. Heat capacity, also called the specific heat, and the thermal conductivity arc parameters which principally control ihc

Tabic 8.1. Thermophysical data for air. hydrogen, helium, carbon dioxide, and water vapour (Irom TkermodynGntic unci transport properties of fluid.* (SI uuifx), Y. R. Mayhew and G. F. C. Rogers, Hassi Blackwell, Oxford)



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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