Hello everyone.
I am working on one of the reboilers in our plant.
My project is to develop a model to calculate and show at what rate the fouling factor is increasing.
I have developed a model of reboiler in HTRI. The reboiler is a forced flow reboiler. I have matched the geometry with the as built.
At the start of the operation, the steam chest pressure is 2.5 barG (Saturation temp: ~139 degC) and end of operation is 7 barG (Saturation temp: ~170 degC)
So, as the reboiler fouls, the steam CV opening increases and chest pressure increases and similarly the saturation temp increases. Thus, due to this LMTD across the reboiler also increases.
While predicting fouling factor by hit & trial method to match process outlet temperature in the model, the fouling factor predicted is on lower side. This is wrong practically.
This is a bit confusing. So stating example:
Case 1: Steam chest pressure:3 barG. Process outlet temp: 120 degC. Calculated Fouling factor: 0.003 m2-hr-C/Btu
Case 2: Steam chest pressure: 5barG, Process outlet temp: 120.5 degC. Calculated Fouling factor: 0.0028 m2-hr-C/Btu
The heat transfer coefficient also increases due to better LMTD in Case 2. Case 2 is showing that my fouling has decreased which is not correct.
Please help me how can i calculate a correct fouling factor in HTRI or by calculation?