Enex upgrades commercial CO2 system
r744.com, September 20, 2017
An upgraded commercial HVAC&R CO2 system from Italian designer and producer of refrigeration systems Enex allows for summer cooling and winter heating in a supermarket, using the energy from the compressors in a refrigeration system.
The CO2 system has been upgraded and “is especially for commercial refrigeration,” according to Enex president Sergio Girotto.
The new concept can be used for any type of shop, whether it is a small or medium-sized supermarket and for large shops as well.
For smaller shops the system uses heat transfer technology to directly exchange heat between the CO2 refrigerant and the ambient air. In larger shops the system uses an indirect loop with water instead of air.
The system also provides direct space heating and cooling, setting it apart from other systems, according to Girotto. “It is a heat recovery system in winter, but the advantage over existing systems is that there is direct heat transfer,” he explains.
Efficiency advantages
Enex argues that integrating refrigeration and space heating offers several advantages:
- Heat is recovered for the whole store and for free, so the cost of heating is zero.
- Larger units work with ejector technology, allowing the store to be air-conditioned more efficiently.
- Only one contractor is needed to take care of the whole installation, making it easier to integrate the air conditioning and heating with the refrigeration system.
- The direct heat transfer (DHT) concept avoids any potential problem caused by the corrosion of coils using water.
- The new concept allows for the immediate transfer of knowledge and experience about using the natural refrigerant CO2 for air conditioning and space heating.
The system changes from heating to cooling automatically in the store, Girotto explains. In winter, CO2 is directed – either totally or partially – into the heat exchanger to recover the heat. If the heat recovered is not sufficient, then one or more compressors can be “switched” to compress the vapour produced by an external evaporator. It is the so-called “false load” which in reality consists of operating part of the system as a heat pump.
In summer when space cooling of the store is needed, the evaporator’s plate heat exchanger evaporates liquid at the pressure of the intermediate receiver. The same compressors used for flash gas recompression manage the vapour.
The same concept can also be used also in direct heat transfer coils. The coils can be installed directly on the ceiling of the sales area or inside one or more AHUs (air handling units). “Direct transfer coils can be used where there is no space for air ducts (low ceilings). Air handling units can be used in other cases, allowing a better air quality control,” Girotto told R744.com.
He argues that the CO2 heating cooling system solves the problem of “which refrigerant to use” for commercial shops, allowing end users to take immediate advantage of all the experience made so far with CO2 in refrigeration, air conditioning and space heating.