Gas Processing Journal
Volume:11 Issue: 1, Winter 2023

Two different coefficient approximation methods are implemented during a Proper Orthogonal Decomposition (POD) approach to analyze a Multi-Stream Heat Exchanger used in cold boxes. Variable-property three-dimensional modeling is used to collect snapshots. Fluid-solid domains are modeled conjugately, and a dimensionless vector-valued approach is suggested for the bases. The Kriging (KRG) and Inverse-Distance Weighted (IDW) methods are employed to approximate the base coefficients according to the Reynolds numbers of streams, and the results are compared. The field is reconstructed for a full interpolation of the POD weighting coefficients and also for a partial extrapolation of them. CFD solution is the criterion for the calculation of deviations. Based on the total heat exchange and exit temperature prediction , the KRG method outperforms the IDW method in 83% of the cases. IDW has better results in some extrapolated cases, although the deviation is substantial for both approaches in these cases. The necessary number of bases depends on the required post-processing for the intended parameter.

In this research, leaking flow from inside the cylinder-piston space to the crankcase through the very narrow passage in the stuffing box is numerically simulated. Two distinguish geometries are considered, and it is assumed the flow is steady, three-dimensional, non-isothermal, laminar, and compressible. The governing equations (including the mass, momentum, and energy conservations) are solved simultaneously along with the ideal equation of state by finite volume method. It is demonstrated that the Mach number is under 0.8 in the majority of the domain. Therefore, the pressure-based strategy is selected to have faster convergence. It is found that the maximum leakage rate for one-row and two-row packing is respectively 49.6 and 41 g/s obtained for a pressure difference of 70 bar. Also, it is shown that the presence of the second row is mandatory to be in safe condition. The percentage of leak control by the second row is much higher for lower pressure differences. Strictly speaking, the second row of rings decreases the leakage rate depending on the pressure difference from 7.9% to 60.7%. To the best of the authors' knowledge, this would be the first time the flow through the stuffing box is simulated.

Accurate determination of the natural gas compressibility factor is crucial for reservoir simulation and material balance computations in petroleum engineering. The data-driven AI techniques, like artificial neural networks, fuzzy systems, and neuro-fuzzy systems, are gaining momentum in estimating fluid properties. An adaptive neuro-fuzzy inference system (ANFIS) is applied here to develop a model to estimate the compressibility factor of two natural gas types. The Takagi-Sugeno fuzzy inference system serves as the foundation for constructing the ANFIS model, where the triangular membership functions are applied. The training data consists of 80% of the available data selected randomly, and the remaining 20% is applied in testing. This developed model is of high accuracy in estimating the compressibility factors of natural gas types, with an average absolute relative deviation of 0.05% and a maximum absolute relative deviation of 0.55% difference between the estimated and experimental value data. Comparing the findings here with the correlations indicates that the ANFIS model in terms of accuracy outperforms its counterparts in this realm.

The conventional distillation columns and a DWCD system, are simulated in this paper. The parameters are optimized through the sensitivity analysis for both processes to reduce the reboilers’ and condensers’ heat duties with considering the products’ purity. The feed contains 2,3-Butanediol (2,3-BD), 1,2-Butanediol (1,2-BD), and 1,4-Butanediol (1,4-BD) components. To simulate the DWCD process, a model consisting of two Absorbers, one Rectifier, one Stripper, and two vapor and liquid splitter columns is adopted. The parameters studied include the number of the column stages, the number of the feed stages, the side product stage number, the reflux ratio, and vapor and liquid split ratios. The findings indicate that the DWCD process has 18.32% and 25.18% energy savings for the reboiler and the condenser heat duties, respectively, compared to the conventional process composed of two distillation columns.