Energy, heat and work transfer

Energy transfer

The transfer of energy can be :
a.    From system to surrounding.
b.    From surrounding to system.

Heat transfer

The transfer of energy without the transfer of mass because of difference in temperature between system and surroundings is called heat transfer. It is path function.
It is denoted by Q. (δQ in differential form)

Sign Convention : [ It depends on the student but needs to be consistent.]
a.    Heat supplied to the system is taken as +ve heat transfer.
b.    Heat supplied to the surrounding(Heat lost by the system) is taken as –ve heat transfer.

Work transfer

The transfer of energy without the transfer of mass because of property difference other than temperature is called work transfer. It is also a path function.
It is denoted by W. (Δw in differential form)

Sign convention : [ It depends on the student but needs to be consistent.]
a.    Work done by the system is taken as +ve work transfer.
b.    Work done on the system is taken as –ve work transfer.
It is a high grade energy.
Work transfer is calculated by the area under the curve in P-V diagram.