Can anybody tell me what are Residual property and Excess property in thermodynamics for?
Residual functions are used to calculate properties of substances at non ideal gas states. I have never heard of the Excess property myself. Perhaps someone else can answer that for you.
Hopefully this link works:
Source: http://imartinez.etsin.upm.es/bk3/c07/Excess functions.htm
This essentially means that it is a way to "adjust" your model so that it matches the natural phenomenon that you are modeling more closely.
It's like using a polytropic process with n=1.2 instead of 1.4 to allow for losses due to a gas having thermal losses/gains or doing some amount of work, etc.
A Residual property is a a measure of the deviation from the value that some property would have for an ideal gas at the same conditions.
For example, if M is the actual value of a thermodynamic property (like the Gibbs free nergy) for a nonideal gas, and Mig is the value the property will have if the gas was ideal at the same T & P, then the residual property MR is defined as,
MR = M - Mig
Excess properties are usually used with liquid solutions, or when we want to measure deviations from a nonideal solution. The excess property is similarly defined as
ME = M - Mid
ie, the difference between the value of a thermodynamic property of the actual solution and an ideal solution at the same T,P and composition.
If you want a reference text, try Chapter 11 of "Chemical Engineering Thermodynamics" by Smith, Van Ness and Abbot.
Separate names with a comma.