Efficiency of Machines Flashcards
The less energy that is ‘wasted’…
The more efficient the device is
What is a machine?
A device that turns one type of energy into another
How do you work out efficiency? (Energy)
Efficiency = Useful Energy Out / Total Energy In
How do you work out efficiency? (Power)
Efficiency = Useful Power Out / Total Power In
Can a device be 100% efficient?
No, and the wasted energy is usually spread out as heat
What will all energy eventually become?
Heat energy
What is the exception to ‘no device can be 100% efficient’?
Electric heaters as all the energy is converted into useful heat
Useful energy is…
Concentrated energy
What happens with waste energy?
It eventually becomes heat energy
The heat is transferred to cooler surroundings, which then become warmer. As the heat energy is transferred to cooler surroundings, the energy becomes less concentrated - its dissipates
What do you need to work out cost - effectiveness?
Payback time
What can USE waste energy?
Heat exchangers
Explain how heat exchangers work
They reduce the amount of heat energy ‘lost’ by pumping a cool fluid through the escaping heat.
The temp of this fluid rises as it gains heat energy.
The heat energy in the fluid can then be converted into a form of energy that’s useful again - either in the original device or for other functions
