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W=the amount of work delivered
Qh=the heat extracted from the high temperature reservoir
Ql= the heat added to the low temperature reservoir
So the total entropy change of the process will be:
delta S = Qh/T - Ql /Tref
the second law says that the total of entropy changes in such a closed system is larger than or equal to zero. Now, let us first assume that we have an ideal process, where the entropy does not increase: delta S = 0.
For ideal processes the following formula can be used:
W= (1-Tref/T) x Qh
we can conclude that for this ideal process, the maximum amount of work produced is always smaller than the heat extracted from the reservoir, which brings us back to our first formulation of the second law of thermodynamics.
delta S = entropy change
delta Q= heat extraction
T = Temperature
E=internal energy (also often indicated with the letter U)
for solids and liquids, the difference between H and E is very small, but for gases the difference cannot generally be neglected
water = H20