temperature difference between tube wall temperature and bubble point

[bpat]

Hi,

Does anyone know that what should be the temperature difference between tube wall temperature and bubble point for falling film evaporator? We have ethylene glycol on tube side and Dowtherm A on shell side. usaually I consider 230°C In/220°C for HTF and 200°C as bubble point, but for one of the application requires 265°C IN and 202°C OUT for HTF. Does anyone has experience with this?

Please advise.

 

[unclesyd]

This doesn't answer your question.

We use Dowtherm A and Therminol VP1 at similar temperature and conditions on a very large scale with the exception that we use the vapor instead of the liquid. The temperature control is accomplished by varying the pressure on HTF. We only use the latent heat and reboil the condensate that is returned almost at the boiling point.
We never use either material at these temperatures as a straight liquid heating media.

Both Dow and Solutia have excellent design manuals for these materials.