Extreme low charge refrigeration systems with R-717

HFC refrigerants are common refrigerants, but also strong global warming gases which will be phased out going forward. The more recent developed HFOs, although not being strong greenhouse gases, are often questioned due to other environmental and safety concerns. As a result, users are turning more to systems using natural refrigerants.  R-717 is for example one of the most efficient natural refrigerants available, with wide usage possibilities from high to low temperatures and up to very large capacities. Apart being a natural substance, the use of R-717 opens for possibilities to reduce energy consumption, and secure for long term cost efficiency and sustainability.
One important and growing type of installation is low-charge ammonia refrigeration systems. These systems utilize the highly energy efficient and natural R-717 as refrigerant but with much lower quantities than in traditional ammonia systems of the past. This means installations becomes also very safe.   
Thera are a few different types of these low charge R-717 systems.  
- Advanced DX systems
- Distributed systems
- Cascade system
- Secondary system

The presentation will describe shortly the various system categories and talk more in detail about the two last ones. The importance of the heat exchanger selection to reduce the charge while achieving high energy efficiency will be described with case stories.