Concept of cycle efficiency
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Diagrams of thermal machines
The concept of
effectiveness, or efficiency
, is used to characterize the overall performance of a cycle, when establishing its energy balance. For a thermal machine intended to transform
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
, this is the ratio between the power produced and the heat supplied to the machine: η = τ/Q.
In general, when we are dealing with relatively complex cycles, we are led to adopt a broader definition of effectiveness or efficiency: it is the ratio of
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
to
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
.
η = (useful energy) / (purchased energy)
-
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
generally represents the sum of all the energies that we had to provide to the cycle from outside;
-
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
represents the net balance of useful energies of the cycle, that is to say the algebraic sum of energies
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
participating in the useful energy effect;
This approach has the advantage of remaining valid in all cases, both for power cycles and for cycles working in reverse. In the latter case, we no longer speak of efficiency because its value generally becomes greater than 1, but rather of
COefficient of Performance COP
heat into mechanical power
produced and consumed within it
purchased energy
the purchased energy
the useful energy effect
useful energy
.
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