A Numerical and Experimental Analysis of a Transcritical, CO2 Heat Pump Water Heater
Bibliographic record
Abstract
Due to the environmental concerns regarding traditional refrigerants, carbon dioxide (CO2) is being studied as an alternative refrigerant in HPWHs.In this study, a commercially available, transcritical CO2 HPWH was numerically and experimentally assessed.This included developing a model of the CO2 HPWH and calibrating it with experimental data.The model was theoretically verified and utilized to predict the cycle pressures and compressor isentropic efficiency.While the predicted discharge pressures were within the expected range, the significant biases indicate that further work is required to increase the model accuracy.Additionally, study of the control system indicated that the water outlet temperature controls the water pump, the ambient temperature controls the compressor and evaporator fan, and that the expansion valve controls the high side pressure.Lastly, the performance data shows that the HPWH achieves the best performance at ambient air temperatures above 0°C and at water inlet temperatures below 30°C. νVolumetric efficiency of compressor 𝑊 ̇compCompressor work (kW)
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".