PARTNER FOCUS
Simulating system underperformance
In the June issue of ACR News, the article ‘Exposing the performance gap’, presented research fi ndings from Eurovent Certifi cation on uncertifi ed CO2
"The results show that even a small under-
performance can have a large impact over the lifecycle of a product."
T
he research highlighted potential gaps between declared performance data and laboratory-measured capacity, fi nding that the tested uncertifi ed units underperformed
by up to 53% in Central and Northern European climates and up to 37% in warmer climates. While those results are striking, examining them in isolation does not refl ect whole system impact. Building on these fi ndings and earlier research on uncertifi ed HFC air-cooled condensers, Eurovent Certifi cation simulated the impact of a single underperforming heat rejection component on a full supermarket refrigeration system. These are the results of those simulations.
Case study aims The aim was to:
Ascertain the potential impact of underperformance in terms of: ■Additional energy consumption ■Additional running costs ■Additional CO2
emissions.
Simulate underperformance at diff erent rates to evaluate impact over 1-year, 10-years and 15-years (whole life cycle).
Method
Using simulation software, the impact of underperformance was calculated using two representative technical solutions for a supermarket application based in Munich, Germany: ■System 1: CO2
transcritical installation
■ System 2: Medium temperature (MT) and low temperature (LT) HFC installation.
Subcritical mode (condenser)
-32% gas coolers. Here, Eurovent examines these results within a simulated case study.
The full system set up can be found in the white paper, ‘Beyond the brochure: Exposing the reality of refrigeration product underperformance,’ downloadable from
www.eurovent-certifi
cation.com Both systems were put through a range of simulations to calculate the impact of underperformance.
System 1: CO2 transcritical installation In this system, heat rejection is performed by a CO2 gas cooler
with a 51.5% underperformance while in transcritical mode and a 32% underperformance while in subcritical mode. The performance was evaluated according to the conditions listed in Table 1, which are based on the average underperformance fi ndings from the ‘Exposing the performance gap’ case study. Underperformance is expressed as increased delta T for the simulations. This translates the lost capacity into a reduced temperature change across the gas cooler. This results in a signifi cantly higher outlet temperature, which may lead to increased high-side pressure and compressor energy consumption, and may reduce overall system capacity and effi ciency.
Operating Conditions Av. deviation Increased delta T + 2.6 K (CO2 Transcritical mode -51.5% outlet
Temperature 34.6°C instead of 32°C)
+ 3.5 K (CO2 condensing
Temperature 18.5 °C instead of 15°C)
Table 1: Underperformance according to each condition based on test results
The gas cooler operates as a condenser for T ambient ≤18°C and in transcritical mode when T ambient >18°C.
Results
The simulations evaluated additional energy consumption, running costs and CO2
year period. emissions over a 1-year, 10-year and 15-
12 July 2026 •
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