and since we have seen above that p « A7 then

Hall (1958) is at pains to point out the severe limitations oJ the analysis particularly with regard to finned surfaces. Despite this, the author finds it a useful measure for comparing the relative merits of working fluids for Stirling engines.

Consider, for example, the live fluids whose properties are given in Table I: hydrogen, helium, air. carbon dioxide, and water vanour. The

The specific heals are 14, 5, 1, 0.8, and 1.8kJ/kg-K (3.35, 1.2. 0.24, 0.192. and 0.43 Blu/lbm°R) respectively. Therefore, from eqn (8.17) above the comparative heat transfer O for a given f'/O ratio is: Hydrogen Oh: 104 Helium Ohc: 44

Air Oa: 29

Carbon dioxide Qc0;: 31 Water vapour 0M.0: 44. On this basis of comparison, hydrogen is clearly the preferred heat transfer fluid with helium or water vapour a second choice and air or carbon dioxide a rather poor third choice.

Water vapour has not been used extensively as the working fluid in a Stirling engine. It can exist at temperatures of 50 to 60 °C (122 to 140°F) (characteristic of automotive engine cooler temperatures) as a vapour only if the pressure is very low, whereas high pressures are necessary to attain a high power density. Water vapour is a candidate for use in a Stirling engine with a compound or multiphase working fluid as described later. The fluid then changes phase from liquid in the compression space to vapour in the hot expansion space. It may or may not operate in association with a gaseous carrier component such as hydrogen or helium.

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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