High-efficiency refrigeration systems with CO2 as a natural fluids in warm climates

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CO2 systems in southern-Europe with Enjector®

It is well known that the efficiency of a simple CO2-only refrigeration system, the so-called "transcritical system", drops significantly when ambient temperatures is higher than 30°C.
Enex has developed a simple and reliable solution for all Europe, especially suitable for warm climates.
Warm cycle

    The complete system developed by Enex combines three well-proven design solutions:
  • Evaporator overfeeding;
  • Auxiliary compressors for flash vapor re-compression;
  • Pre-compression with ejectors.

Due to the first one of the above solution the evaporating temperature can be increased as much as 6K. The measured energy saving is in the range of 13-15% when combined with an optimized control logic for suction pressure (see enjector page) . The advantage given by the second solution is due to the fact that the flash vapor produced during the first expansion stage is compressed before reaching the lowest pressure of the cycle. In a typical summer day in southern Europe, the energy saving given by flash vapor recompression can be as high as 15%. Maximum benefit is attained by including ejectors to support auxiliary compressors. The overall efficiency gain of the complete solution, as measured in real plants, reaches 30% in the warmest climates. The above design solutions are also extremely beneficial in the climate conditions of northern Europe, during heat recovery season


The complete thermodynamic cycle for a booster system is shown below. A standard cycle is compared with the new one. Evaporator overfeeding is also available for low temperature users. Warm cycle