Product performance is critical to achieving system reliability and energy efficiency. However, correct product selection and good system design hinges on accurate manufacturer data. Without it, refrigeration systems may underperform. To gain insight into the correlation between data and product performance, Eurovent Certification put two uncertified CO₂ gas coolers through a comprehensive evaluation process including laboratory tests, data analysis and evaluation via a professional design tool. This case study explores the research, its aims, methodology and results.
Aims and methodology
The aim was to ascertain:
- If there were any discrepancies between manufacturer declared data and measured performance.
- The accuracy of Eurovent Certification’s correction factors: calculations applied to tests at standard conditions to simulate the efficiency of CO2 units across different climate zones.
It was critical for the research to follow an authentic customer journey. A project specification was created and submitted to independent distributors for an offer. Eurovent Certification received five (5) offers from the distributors based on the specification.
The offers included heat rejection capacity of the units under standard and different market conditions as follows:
- Condition 1: Standard transcritical condition (known as SC20)
- Condition 2: Market transcritical condition at High ambient T with 2K approach used in warm weather areas
- Condition 3: Market transcritical condition with 3K approach used in the Central and Northern European market
- Condition 4: Market transcritical condition with 2K approach used in the Central and Northern European market
- Condition 5: Standard subcritical condition (Condenser) known as SC25.
Table 1: Operating conditions in transcritical mode
| Condition in transcritical mode | Gas Cooler inlet pressure | Gas Cooler inlet temperature | Air Inlet temperature | Gas Cooler outlet temperature | DT (temperature approach) |
| Condition 1 (standard condition SC20) | 90 bar | 110 °C | 30 °C | 35 °C | 5 K |
| Condition 2 | 92 bar | 110 °C | 35 °C | 37 °C | 2K |
| Condition 3 | 80 bar | 100 °C | 29 °C | 32 °C | 3 K |
| Condition 4 | 80 bar | 100 °C | 30 °C | 32 °C | 2 K |
Table 2: Operating conditions in subcritical mode (operating as a Condenser)
| Condition in subcritical mode | Air inlet temperature | Condensing temperature | Refrigerant inlet temperature | Subcooling |
| Standard condition SC25 | 5°C | 15°C | 60°C | <3 K |
A design tool was used to calculate the predicted heat rejection capacity of the units under these standard and market conditions.
Design simulation results
The results from the design software simulations suggested that, while units behaved reliably at Standard Condition (SC20), performance may deviate from declared values when operating under non-standard conditions. Conditions 3 and 4 saw significant underperformances:
- At condition 4, the average underperformance was 32% and maximum underperformance 41%
- At condition 3, the average underperformance was 26% and maximum underperformance 28%.
The two CO2 gas coolers displaying the most significant performance gap were selected for laboratory testing.
Independent laboratory tests
The gas coolers undertook an identical evaluation process based on the Eurovent Certified Performance for Heat Exchangers programme, using the test standard EN327 to measure:
- Heat rejection capacity: testing under both subcritical / transcritical conditions
- Fan power consumption
- Air flow rate
- For the sound measurement, the test standard EN 13487:2019-11 and EN ISO 9614-1:2009-11 was used.
To ensure impartial testing, Eurovent Certification had no direct contact with the tested units, or the laboratory testing process, which was handled by an independent Legal Officer (French Bailiff).
The laboratory results
The units displayed material deviations from declared performance under non-standard conditions:
- At condition 4 the average underperformance was 51.5% for both units and the maximum underperformance 53%.
- At condition 3 the average underperformance was 40% across both units and the maximum underperformance 41%.
- At condition 2 the average underperformance across both units was 35% and the maximum underperformance 37%.
- When operating as a condenser (subcritical) the average underperformance of both units was 27.5% with a maximum underperformance of 32%.
Figure 1: Deviations between declared and measured heat rejection capacity under transcritical conditions
Notably, the independent laboratory tests showed that actual measured performance under the tested operating conditions exceed the shortfalls predicted by the design tool simulations.
Correction factors
One aim of the laboratory tests was to evaluate the correction factors used by Eurovent Certification to calculate gas cooler performance at different market conditions (climates). To comply, tested results had to be within a 15% tolerance of the values available within the Heat Exchanger Technical Certification Rules (TCR).
Table 3: Gas Coolers correction factors comparison
| Calculated from the test results | Calculated from the design tool | Available in TCR | ||
| Correction factor for Condition 3 | Unit 1 | 0,56 | 0,58 | 0,62 |
| Unit 2 | 0,54 | 0,58 | ||
| Mean value | 0,55 | 0,58 | ||
| Correction factor for Condition 4 | Unit 1 | 0,46 | 0,47 | 0,52 |
| Unit 2 | 0,43 | 0,48 | ||
| Mean value | 0,45 | 0,48 |
The tested results fell into the 15% tolerance. Correction factors therefore provide a reliable method for calculating CO2 performance across different climates.
Conclusion
The study found a correlation between accurate data and product performance. The uncertified CO2 gas coolers were found to have significant deviations between declared and measured performance across non-standard conditions, especially those related to Central and Northern European climates. In contrast, Eurovent Certification’s CO2 testing protocol and correction factors were validated – showing that third-party verification can help provide transparent, accurate performance data across multiple climates.
Want to know more? A new white paper from Eurovent Certification explores the impact of heat rejection equipment underperformance. Download Beyond the brochure: Exposing the reality of refrigeration product underperformance for free at www.eurovent-certification.com
