Template 1

Heat Engine

http://www.grc.nasa.gov/WWW/k-12/UEET/StudentSite/engines.html

Heat engines are used to create work output in an airplane. Jet fuel is stored in fuel tanks and is supplied to the engine, but as we know we will never be able to have the process be perfectly efficient. This is very important to factor in, because an airplane cannot simply pull over on the side of the road and wait for extra fuel to arrive. It is very important the the plane has enough fuel to make it to its destination while still having a surplus. At the same time the airlines do not want the excess weight of too much extra fuel, because it lowers their payload and ability to make extra money hauling passengers and baggage. This is the reason being able to calculate efficiency is very important and can help create safe, and economical travel.

http://en.wikipedia.org/wiki/Heat_engine

Efficiency: Here are a few equations to see how efficiency is calculated based on the diagram to the left.

Thermal Efficiency: n = (Work Out)/(Qh)
n = 1-(Qh/Ql)

Maximum efficiency is also called Carnot efficiency, no real engines have ever been able to reach this, but it puts an upper limit on what is theoretically possible. We will never reach this because there will always be heat lost to the environment and there has to be some exhaust to the cold sink to create a possible engine. These equations should be used when finding theoretical maximum work and efficiency (Knight, 2004).

Carnot Efficiency: n=1-(Tc/Th)