Newton's
Laws of Motion
Are exactly what drives Heat Engines and Thermodynamics.
In an engine, Work is stored in heated compressed vapor. As that vapor expands, the Work is transferred to the engine parts.
When engines compress air, work is again stored in the air as heat.
When engines add heat to air that has been compressed, the air pressure is multiplied proportionally to the heat added. (Ideal Gas Law.) If the air pressure is 1 atmosphere, or 15 pounds per square inch, and enough heat energy is added to double the temperature (and so double the pressure), the air pressure is doubled, or 30 pounds per square inch.
By first compressing the air, so the air pressure is for example, 100 pounds per square inch, doubling the pressure yields 200 pounds per square inch, a much larger force in a much smaller volume. It does not increase efficiency, it reduces engine size. Compression's main purpose is to create a more powerful engine in a smaller space.
|
Work = Force times Distance
above directly from Newton's Laws of motion. Heat engines are driven by pressure and changing volumes. How do you relate Newton's Laws of Motion formula of Work to an Expanding Vapor Engine?
Force = Pressure times Area
Volume = Area time Distance
So Work = Force times Distance = (Pressure times Area) times Distance
or ... Pressure times (Area times Distance)
or ... Pressure times Volume.
Work = Pressure times Volume
Note: It is important to recall that both Distance and Volume in these equations refer to a CHANGE in distance or volume.
The same amount of work is done in either direction.
Increase volume - (Expansion) air gives work to engine. Air loses heat.
Decrease volume - (Compression) engine gives work to air. Air gains heat. |
