Efficiency enhancement by combining the carbon dioxide process with a water-loop using water as refrigerant.

As a consequence of the F-Gas regulation R404A is no longer a viable option for commercial refrigeration applications. Therefore, this paper focuses on natural refrigerants. There are some alternatives like carbon dioxide, but with an energy efficiency penalty at increasing ambient temperatures. A promising alternative is the combination of carbon dioxide with a water-loop using water as refrigerant at the same time. The benefit is a constant heat sink temperature of the carbon dioxide process all over the year and consequently, the potential to optimize the system for constant operational conditions. Finally the annual COP values of a standard and water-loop system will be discussed.