Seeking help with sensitivity
Thread Content
Problems arose when attempting to simulate the relationship between the molar concentration of the target product at the top of the tower and the reflux ratio (i.e., X-R). In the previous state, the results were available; now, there is a sensitivity issue. Row 19 of the XR block starts as follows: Block: B1, Model: RADFRAC. *** SEVERE ERROR: The specified value for the reflux ratio is less than the built-in limit of 1E-15. * WARNING: The rest of this block has been bypassed due to this severe error. ** ERROR: Block B1 is not in mass balance – mass flow rate at the inlet is 0.79903890E+00, while the mass flow rate at the outlet is 0.00000000E+00; the absolute difference is 0.79903890E+00. Row 20 of the sensitivity block starts as follows: * WARNING: The sampled variable “C8” has not been calculated; its value is missing. Block: B1, Model: RADFRAC. Convergence iterations: Iteration 1: Error/Tolerance = 4527.1; Iteration 2: 9.6152; Iteration 3: 0.18443E-04. ** ERROR: Some rows were completed with errors. ** ERROR: Some rows were completed with errors. ** ERROR: Some rows were completed with errors.
The specified value for the reflux ratio is less than the built-in limit of 1E-15; the reflux ratio has reached the lower limit.
Reply to 2# emirateyi: I’m sorry for my ignorance; could you please explain it in more detail? The reflux ratio has reached its lower limit. Does this mean that I should increase the lower limit value for the reflux ratio in the sensitivity analysis? Let’s change to something else instead, thank you, kind person.
For sensitivity analysis, check the results after an error occurs; some cases show \"OK\" while others show \"Error\". If this is the case, it indicates that there is a problem with the variable range or initial values. As the friend on the 2nd floor said, adjust it and try again.
When simulating the relationship between the tower diameter and the height of the packing bed (i.e., the D-H relationship), the status bar turns blue after the calculation, indicating that the result is available. However, the following message appears: * WARNING SAMPLED VARIABLE “DIA” HAS NOT BEEN CALCULATED. VALUE IS MISSING. When viewing the results, there is data in the column corresponding to the bed height, but no data in the column corresponding to the tower diameter. I’m not sure what’s going on; could someone with more experience please help me?