Page 67 - DJJ20063- Thermodynamics 1
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DJJ20063- Thermodynamics 1
Example 2.11
A quantity of a certain perfect gas is heated at a constant temperature from an initial
3
2
2
state of 0.22 m and 325 kN/m to a final state of 170 kN/m . Calculate the final
volume of the gas.
Solution to Example 2.11
From equation P1V1 = P2V2
2
P 325 kN/m
V = V x 1 = (0.22 m 3 ) 2 = 0.421 m 3
1
2
P 2 170 kN/m
b. Charles’ Law
The Charles’s Law may be stated as follows:
Provided the pressure P of a given mass of gas remains constant, then the volume V of
the gas will be directly proportional to the absolute temperature T of the gas, i.e.
V T, or V = constant x T. Therefore V/T = constant, for constant pressure P.
If gas changes from state 1 to state 2 during a constant pressure process, then
V 1 = V 2 = constant (2.10)
T 1 T 2
If the process is represented on a P – V diagram as before, the result will be as shown in
Fig. 2.4.2-3
P
1 2
V
0
V1 V2
Figure 2.4.2-3 P-V graph for constant pressure process
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