2 replies to this topic

[naimkauf]

Hello, I am currently designing a total condenser for a distillation column. I know that my outlet temperature will be at bubble temperature but I'm not sure how to calculate or estimate my feed temperature for an energy balance. How should I proceed with this?

[Bobby Strain]

The feed temperature will be close to the overhead vapor temperature at the top tray pressure.

 

Bobby

[Pilesar]

In real life, condensers are purchased with more area than absolutely necessary. This is so they will continue to function acceptably as the heat transfer surfaces foul. Extra area also serves as a safety factor for design uncertainties. Process condensate from higher in the exchanger drips down to a heat transfer surface lower in the exchanger where it continues to cool. So most of the time, this extra surface area is still actively transferring heat and the outlet temperature will be below the bubble point. Usually, no one really cares how much the liquid is subcooled so the bubble point temperature is used in the design calcs. One tricky part of condenser design comes when the exchanger outlet must be subcooled a specific amount in order to be considered successful. There are several ways to build a condenser to also intentionally subcool, but it is much easier to design a separate exchanger to reliably subcool the liquid and the economics need to be considered.