Experimental Investigation of Double Pipe Heat Exchangers for Cryogenic Applications
Bibliographic record
Abstract
This study aims to directly recover cold energy from liquid nitrogen evaporation for cooling applications utilizing a doublepipe heat exchanger.The double-pipe heat exchanger has an inner tube inner diameter of 10.7mm, an inner tube outer diameter, an outer tube inner diameter of 20mm, and an outer tube outer diameter of 24mm.Experiments were carried out with saturated liquid nitrogen with an inlet temperature of 93 K and mass flux of 66, 144, and 238 kg/s-m 2 flowing at the tube side while simultaneously being heated by a heat transfer fluid (HTF) at the annular side of the heat exchanger.Ethylene glycol-water mixture (35% wt.) with inlet temperatures ranging from 295 to 300 K and flow rates ranging from 0.03 to 0.22 kg/s.The annulus side of the double-pipe heat exchanger was split into three sections to avoid severe ice accumulation due to the inevitable decrease in the HTF temperature as the HTF flows along.The results show that the outer surface heat flux of the inner tube increases substantially with the increase of liquid nitrogen flow rate, which suggests that the flowing nitrogen is in the film boiling region.Furthermore, experimental results show the feasibility of utilizing film boiling for liquid nitrogen cold energy recovery.The vapor blanket formed at the wall surface prevents the wall temperature from overcooling while recovering large amounts of cold energy due to the immense temperature difference between the HTF and nitrogen.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".