AMMONIA DIRECT EXPANSION
Refrigeration systems that use Ammonia as a refrigerant usually have Evaporators with the fluid mechanically pumped, (Pump Evaporator).
In these cases, the pumped Ammonia travels through the bottom to top, entering the lower tubes the fluid rises through the parallel tube circuits and exits through the upper collector. These Evaporators (pumped) generally use tubes with large diameters (19 mm or even up to 25 mm) and consequent large internal volume.
Projects of Evaporators with these characteristics, large internal volume of tubes, parallel circuits and pumped Ammonia generate a Evaporators with a very high charge of refrigerant.
Decrease the refrigerant charge in the evaporator and in the cooling system. refrigeration is a worldwide trend and demand from end customers, obvious reasons such as lower risk of contamination to the environment and the people due to leaks.
Using Evaporator with direct expansion in Ammonia is an excellent solution to decrease the refrigerant charge of the evaporator and the system, direct or dry expansion, as it is called, can reduce up to 40 times the Ammonia charge compared to conventional Ammonia pumped. It also reduces the diameter of liquid lines and the initial cost due to fewer containers needed to maneuver the system. The system with Dry Expansion Ammonia provides excellent efficiency in heat transfer being proper design and use of expansion valves is necessary electronics.
