Performance evaluation of cycles

Performance evaluation of cycles: comparisons with the ideal Carnot heat engine that is a totally reversible heat engine or pump.

Q °c T of reservoir (absolute scale)

(1) “Efficiency” (r)) of a Heat Engine

Carnot cycle. "HCamot 1 rp , ^1 Real Process ^ ^1 Carnot

"H Real Process ^ ^

Real irreversibilities:

• Friction, electrical resistance, heat transfer across finite temperature difference, …

(2) “Coefficient of Performance” (COP) of a Heat Pump

Heating conditions (heat pump):

O

Carnot cycle: COPHeat Camot

Cooling conditions (refrigeration): O

T

Carnot cycle: COPCoolCarnot ~——

Th-tl

For energy exchange with the same two thermal reservoirs: O

COP ‘Actual Pump A Carnot

Carnot efficiency of a heat pump: r

Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning