Enex Srl / Enjector

CO2 systems improvement

Enjector technology improves CO2 systems efficiency, by permitting the energy recovery of the high-pressure fluid outgoing the condenser/gas cooler. Thereafter, the recovered energy is used to obtain the so-called “zero overheating” in the evaporators, without incurring the cost and complexity related to the refrigerant pumping.

This innovation eliminates the suction pressure increase’s main limit. In fact, the current solutions require maintaining a temperature 7-10K gap between air and evaporation, in order to prevent the liquid in the suction ducts from breaking down the compressors. Whereas, with the Enjector technology, the evaporating temperature is always the maximum allowable by the thermal load.

Solution without ENJECTOR®
Solution with ENJECTOR®

Enjector technology

Enjector system eliminates the suction pressure increase’s main limit and, in this way, the evaporating temperature is always the maximum allowable by the thermal load.

Main characteristics:

Maximum COP (performance coefficient) and, consequently, minimum energy consumption;

Maximum ease: requirement of just one temperature sensor per evaporator

Minimum cost: easier installation and smaller compressors capacity

Maximum reliability: no return of liquid to the compressors

No further maintenance: Enjector is a static component without movable parts and is not subject to wear and tear

Refrigerating cycle with ENJECTOR®

System configuration:

– Intermediate receiver
– low pressure receiver/evaporator
– liquid/vapour ejector


In traditional units the electrical supply to the evaporators is controlled by overheating and the evaporation pressure is low because of the inefficient utilisation of the thermal exchange surface.


With the liquid ejector it is possible to “pump” the excess liquid into the intermediate receiver and increase the evaporation pressure by reducing the power consumption.


The vapour ejector allows to transfer vapour flow from the main compressors to the auxiliary compressor further reducing energy consumption.

Evaporator overfeeding is a simple method to improve performance; in fact, the effect on system efficiency is immediate.

Since 2011, Enex has been developing an innovative method to slightly overfeed evaporators. Given that the thermal exchange surface is fully used at the temperature of evaporation, the pressure of the evaporator can be easily increased. As a result, the same performance in terms of air temperature is obtained, and any increase in evaporation temperature is positively reflected on COP.

Enex has developed and tested a method that includes the use of bi-phase ejectors to reintroduce into circulation the excess liquid that comes out of the evaporators (fig. 2). The ejector is a reliable and convenient device to pump liquid for free.

Now, the next step in the recovery of energy is to use the ejectors to support the refrigeration cycle with an economizzatore, so that the highest amount of energy is recovered, even during the winter. Thanks to the ejectors, the mass flow processed by the auxiliary compressors increases, while the quantity of mass flow processed by compressors with a lower suction temperature decreases. Such configuration is extremely flexible, while the regulation capacity of the system is not compromised by the ejector performance.

Figure 2
Figure 3