How to calculate the latent heat when there is a boiling temperature range?

Question

I have a DME (dimethyl ether)- methanol - water mixture with the mol fraction composition: DME 0.4295, methanol 0.1353, water 0.4351.

This mixture has a boiling temperature range: dew point 141.6 °C and bubble point 69.95 °C, and the heat applied for the phase change (condensation) is a latent heat. How can I calculate it?

I know that for pure compounds, during the condensation process, there's no temperature change, so the latent heat is the result of:

Q = mass flow * latent enthalpy (constant value)

For a mixture that has a condensation temperature range, can I use the same equation? If this is not the case, how can I calculate the latent enthalpy for a mixture in function of the temperature?

Answer 1

Conceptually, it is possible to calculate the enthalpy of any mixture of these three compounds in the vapor phase and in the liquid phase. So heat balances on pieces of equipment can thereby be properly carried out. But, in the case of such a multi-component mixture, the concept of latent heat ceases to have realistic meaning and applicability in practice.