SECOND LAW OF THERMODYNAMICS
Thermodynamics
Summary
The important information from this chapter is summarized below.
Second Law of Thermodynamics Summary
•
Planck’s statement of the Second Law of Thermodynamics is:
It is impossible to construct an engine that will work in a
complete cycle and produce no other effect except the raising of
a weight and the cooling of a heat reservoir.
•
The Second Law of Thermodynamics demonstrates that the maximum possible
efficiency of a system is the Carnot efficiency written as:
h = (TH - TC)/TH
•
The maximum efficiency of a closed cycle can be determined by calculating the
efficiency of a Carnot cycle operating between the same value of high and low
temperatures.
•
The efficiency of a component can be calculated by comparing the work
produced by the component to the work that would have been produced by an
ideal component operating isentropically between the same inlet and outlet
conditions.
•
An isentropic expansion or compression process will be represented as a vertical
line on a T-s or h-s diagram. A real expansion or compression process will look
similar, but will be slanted slightly to the right.
•
Efficiency will be decreased by:
Presence of friction
Heat losses
Cycle inefficiencies
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