EFFECTS OF BUOYANCY ON THE PERFORMANCE OF A VERTICAL DOUBLE-PIPE HEAT EXCHANGER
Bibliographic record
Abstract
CFD simulations of heat transfer between two fluids in a parallel-flow vertical double-pipe heat exchanger, taking into consideration conduction in the walls, viscous dissipation, variable fluid properties, and axial diffusion in the fluids, illustrate the effects of buoyancy on the velocity and temperature profiles as well as on the Nusselt numbers and friction coefficients. In particular, the results show that flow reversal occurs at different positions depending on the flow direction. In the developing region, the fluid bulk temperatures, the wall temperature, and the local Nusselt numbers for both fluids depend on the flow direction. For the conditions under consideration, the Nusselt number for the fully developed flow in the inner pipe lies between the corresponding forced convection values for the constant heat flux and constant temperature conditions, while the one in the annulus is smaller than both these forced convection values. It is established that the flow and thermal fields in the inner cylinder and the annulus cannot be predicted correctly by studying each one separately since the thermal condition at the solid wall separating the two fluids depends on flow characteristics such as the Richardson number in the inner tube.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".