WHITE PAPER — The Big 6 flowmeter technologies: Where to use them and why Flow is one of the most frequently measured process variables throughout industry, and one where the choice in measurement technology is critical. In fact, no single flowmeter…
More detail needed for VLE method
I read with interest Mr. Bahadori’s article in Chemical Engineering (August 2007; pp. 47 – 51) on the above subject. His new approach stated the algorithm for determining K i’s, x i’s and y i’s. However, he didn’t provide the constant values of A i, B i, C i, and D i or state where or how these constant values in Eq. (2 – 6) can be obtained or determined. Further the range of applicability of this new method in relation to reduced temperature ( T r) and pressure ( P r) was not mentioned and should in fact be provided since these constants ( A i, B i, C i, and D i) are dependent on the reduced parameters. Obviously, it’s essential for the reader to note where the available parameters in the polynomial equations are determined/obtained and their limitations in order to confirm the viability and accuracy of the technique. I didn’t observe these things in Mr Bahadori’s article. I hope that such important information will be provided in due course.
Jubail Industrial College, Saudi Arabia
An expanded procedure for determining tuning coefficients (Steps 1 – 4) is provided below. These coefficients can be tuned using the least-squares method for any experimental data set so that the model will predict a wide range of data accurately.
This approach has two main advantages in comparison to other models:
We can retune the coefficients based on some available data to zoom for VLE calculations in a specific range of pressure and temperature.
These coefficients can be retuned if more accurate data are reported in the future for a multicomponent system.
Determining tuning coefficients (Steps 1 – 4 revised). Repeat the following procedure for each component i:
Step 1. For each temperature (numbered from 1 to j), plot the experimental data x i as a function of partial pressure and use the least squares method to curve fit it per the following equation: x i = A ij + B ij P r + C ij P r 2 + D ij P r 3 This will yield j sets of A, B, C, and D coefficients for the given component.
Step 2. Next, plot all the A’s versus temperature and use the least squares method to curve fit them as a function of temperature (numbered from 1 to j) to determine the A temperature tuning coefficients ( A Aij, B Aij, C Aij and D Aij) for use in Equation (2)
Step 3. Repeat Step 2 for the B, C, and D coefficients to determine the B temperature tuning coefficients ( A Bij, B Bij, C Bij, D Bij) for use in Equation (3), the C temperature tuning coefficients ( A Cij, B Cij, C Cij, D Cij) for use in Equation (4) and the D temperature tuning coefficients ( A Dij, B Dij, C Dij and D Dij) for use in Equation (5).
Step 4. Repeat Steps 1 through 4 for each component
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