Determination of Individual Diffusion Coefficients of C3H8/<i>n</i>-C4H10/CO2/Heavy-Oil Systems at High Pressures and Elevated Temperatures by Dynamic Volume Analysis
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Bibliographic record
Abstract
Summary By coupling heat and mass transfer for C3H8/n-C4H10/CO2/heavy-oil systems as well as by treating heavy oil as multiple pseudocomponents, a new technique together with its computational scheme has been developed to determine individual diffusion coefficients of alkane solvents and CO2 in heavy oil at high pressures and elevated temperatures by dynamic volume analysis (DVA). Experimentally, well-designed diffusion tests have been conducted for an n-C4H10/heavy-oil system, a CO2/heavy-oil system, an n-C4H10/CO2/heavy-oil system, and a C3H8/n-C4H10/CO2/heavy-oil system by using a visualized pressure/volume/temperature (PVT) setup. The volume change of liquid phase is monitored and recorded during the measurements, whereas the gas-chromatography (GC) method is used to determine the compositions of gas mixtures at the beginning and the end of the diffusion tests. Theoretically, the volume-translated Peng-Robinson (PR) equation of state (EOS) characterizing heavy oil as multiple pseudocomponents has been incorporated to develop a 2D heat-and-mass-transfer model for the aforementioned systems. The alternating-direction-implicit algorithm is applied to solve the 2D difference equations into which a moving gas/liquid interface has been successfully incorporated. The discrepancy between the measured and calculated dynamic-volume change and the discrepancy between the measured and calculated gas compositions at the end of diffusion tests have been minimized to determine the individual diffusion coefficients. Alkane solvents diffuse faster than CO2 in heavy oil, whereas addition of alkane solvent(s) into the CO2 stream not only enhances mass transfer, but also achieves an improved swelling effect of heavy oil. Among the four diffusion tests, the largest dynamic swelling factor at the end of the diffusion test is measured to be 1.118 for the C3H8/n-C4H10/CO2/heavy-oil system.
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Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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