During many industrial process operations, temperature evolution (increase) can occur:
When a vessel containing a volatile liquid and a non-condensable gas (e.g. air) is heated at constant pressure, the vapour space gas undergoes expansion and a portion of the gas phase leaves the vessel through the vent. Additionally, the saturated vapour pressures for the volatile liquid components increase.
Envmodels propose two standard different models for estimating emissions during temperature evolution processes:
The two approaches yield similar results when the amount of heat-up is small, and the final temperature is well below the boiling point of the liquid mixture. However, the disparity between the results from the two options increases as the final temperature approaches the boiling point in this case heating model is the better choice).
The hypotheses assumed for the use of these models are following: