Interpretation:
Determine the entropy change for propane gas caused by the given process.
Concept Introduction:
Since at first the gas is not ideal gas, so the actual path of the process is divided into two step process in which at first step the gas will convert from real gas into ideal gas at given
The entropy change is calculated as:
And the temperature change for an ideal gas during throttling is zero because throttling process is isenthalpic and for an ideal gas enthalpy is the function of temperature only, so the temperature does not change during throttling process for an ideal gas.
Answer to Problem 6.54P
Entropy change is
Explanation of Solution
Given information:
It is given that propane is at
It is also given that at final state gas is assumed to be an ideal gas.
Step 1,
A hypothetical process that transforms a real propane gas into an ideal gas at
The entropy and enthalpy change for this process are:
and
Where
And
For pure species propane, the properties can be written down using Appendix B, Table B.1
So, at above values of
At
At
At
At
And
At
At
At
At
Applying linear interpolation of two independent variables, From linear double interpolation, if
And
Now, from equation,
Or
And
Or
For Step 2
Enthalpy will not change during throttling of propylene, so
Enthalpy of propylene which is now in ideal state is same in final state and hence
Where
Values of above constants forpropane in above equation are given in appendix C table C.1 and noted down below:
And
Hence
Now for entropy change
Values of above constants for propane in above equation are given in appendix C table C.1 and noted down below:
Hence,
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Chapter 6 Solutions
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