Page 136 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

4.0 SECOND LAW OF THERMODYNAMICS

4.1 Apply the concept of the second law of thermodynamics.

4.1.1 Explain the second law of thermodynamics

According to the First Law of Thermodynamics as stated in chapter 3, when a system

undergoes a complete cycle, then the net heat supplied is equal to the net work

done.

 dQ =  dW
This is based on the conservation of energy principle, which follows from the observation

on natural events.

The Second Law of Thermodynamics, which is also a natural law, indicates that;

Although the net heat supplied in a cycle is equal to the net work done, the gross

heat supplied must be greater than the work done; some heat must always be

rejected by the system.

…The Second Law of Thermodynamics

In symbols,

Q1 – Q2 = W (4.1)

To enable the second law to be considered more fully, the heat engine must be discussed.

4.1.2 Explain the principles of a heat engine and a reverse heat engine heat

pump

We know from experience that work can be converted to heat directly and completely,

but converting heat to work requires the use of some special devices. These devices are
called heat engines.

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