Experimental investigations of low-temperature driven ejector for isobutane.
Bibliographic record
Abstract
The paper describes experimental and numerical investigation of ejection refrigeration system dedicated for short time storage of food products for local retail market, especially in rural areas. This work was sponsored by US Dept. of Agriculture under Phase I SBIR program. This novel method does not use electricity and is cleaner for the environment than other refrigeration techniques. One of the crucial problems of the retail market of perishable foodstuff is a lack of efficient and appropriate refrigerated storage capacity. The existing technology in most cases uses conventional refrigeration systems that consume a large amount of electricity, they are expensive as well as use harmful working substances (usually artificial GHG gases that have high greenhouse warming potential in comparison with most of the natural substances). In addition, ensuring required storage conditions in terms of the stability of the product temperature and humidity may be a challenge for most of the existing short time storage refrigerators.  Responding to these challenges we developed an ejector based refrigeration system that 1) utilizes solar or waste heat (below 100C temperature) as a main source of energy, 2) eliminates the mechanical compressor, which is a main user of electricity and the main contributor to maintenance and reliability issues in cooling systems and 3) operates without any ozone depletion effects and any greenhouse gas (GHG) emissions, when used with natural refrigerants. Until recently, ejector use in refrigeration systems was considered as controversial because most of the research conducted in the past has yielded only theoretical results without visible, commercial products. The main issue was a relatively low value of coefficient of performance (COP) in comparison with classical compression systems. Selection of the working fluid for the refrigeration or air-conditioning system is the crucial problem because the system efficiency is strongly influenced by the thermodynamic properties of the refrigerant. We found that the maximum efficiency can be achieved with natural refrigerants, of which isobutane is by far the most favorable. However, primarily due to its flammable nature, isobutane is not currently allowed in commercial systems in USA and Canada although it has been used for many years in all domestic refrigerators in Germany and other EU countries where appropriate safety precautions and regulations were developed. For US market, we identified two other environmentally friendly equivalents to isobutane: R245fa and R1234ze both with zero ozone depletion potential. The research described here had overcome another limitation - a lack of appropriate methods for the design of ejector geometry. Such methodology was developed and tested in a variety of thermodynamic cycles for cooling, heating and heat pumps. The test stand and the experimental results of investigation for isobutane as a working fluid along with CFD modelling results are shown and discussed in the paper in details.Â
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".