Heat Engine Efficiency
A heat engine is a system that converts heat or thermal energy to mechanical energy, which can then be used to do mechanical work.
The thermal efficiency equals 1 minus the ratio of the waste heat flowing out of the engine into a low\[Hyphen]temperature reservoir to heat flowing into the engine from a high\[Hyphen]temperature reservoir.
Formula
![QuantityVariable["η", "Unitless"] == 1 - QuantityVariable[Subscript["Q", "2"], "Heat"]/QuantityVariable[Subscript["Q", "1"], "Heat"]](https://www.wolframcloud.com/objects/resourcesystem/marketplacestorage/resources/fb7/fb78a392-b3fd-4089-a20a-347da6320928/Webpage/FormulaImage.png "Copy to Clipboard")
| symbol | description | physical quantity |
|---|---|---|
| η | efficiency | "Unitless" |
| Q1 | heat flowing into an engine from a hightemperature reservoir | "Heat" |
| Q2 | waste heat flowing out of an engine into a lowtemperature reservoir | "Heat" |