West number
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The West number is a parameter used to characterize the performance of Stirling engines, and other Stirling systems. It is very similar to the Beale number where a larger number indicates higher performance; however, the West number includes temperature compensation. The West number is often used to approximate of the power output of a Stirling engine. The average value is (0.25) [1], but may range up to (0.35) [2], particularly for engines operating with a high temperature differential.
The West number may be defined as:
where:
- Wn is the West number
- Wo is the power output of the engine (watts)
- P is the mean average gas pressure (Pa) or (MPa, if volume is in cm3)
- V is swept volume of the expansion space (m3) or (cm3, if pressure is in MPa)
- N is the engine cycle frequency (Hz)
- TH is the absolute temperature of the expansion space or heater (Kelvin)
- TK is the absolute temperature of the compression space or cooler (Kelvin)
To estimate the power output of a new engine design, nominal values are assumed for the West number, pressure, swept volume and frequency, and the power is calculated as follows:
[edit] Also See
[edit] External links
- [http://www.bekkoame.ne.jp/~khirata/academic/simple/simplee.htm Stirling Engine Performance Calculator
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