27-01-2016, 10:39 AM
Thermodynamics
The science of thermodynamics deals with the relationship between heat and work.
It is governed by two laws, neither of which have ever been proved.
On the other hand no violations of either law have ever been observed.
First Law of Thermodynamics
The energy that can be extracted from a process can never be more than the energy put into the process.
In other words
Energy out = Energy in.
This is essentially the law of conservation of energy, i.e.
Energy can be neither created nor destroyed, it can only be converted from one form to another.
The second law of thermodynamics
The first law is concerned with the totality of energy in a process
The second law tells us how much work we can extract from a given amount of heat.
Carnot’s statement was to the effect that we cannot convert all the the available heat into work.
The second law is also concerned with whether a process can occur at all. For example,
Heat will always flow from a high to a low temperature
A gas under pressure will expand; compression does not occur naturally
Heat Engines
A heat engine is a device for extracting work from a hot fluid. For example
A car engine extracts power from the combustion of fuel with air
A steam steam turbine extracts power from steam
Both of these function by allowing a hot fluid to expand so as to cause motion in a critical component of the engine.
In the process, high grade energy is said to be degraded to lower grade energy.