FEATURE

INCORPORATING COLD CHAIN

By eurammon

According to an analysis by the Umweltbundesamt( German federal environmental agency) in 2014, refrigeration alone accounts for 14 % of Germany’ s overall energy consumption, and is responsible for about 5 % of direct and indirect greenhouse gas emissions. In consideration of national and international climate protection goals, it is imperative that climatefriendliness in the refrigeration sector be improved. An important contribution can be made by using natural refrigerants such as R723, which is particularly environmentally friendly with an ozone depletion potential( ODP) of 0 and a global warming potential( GWP) of 8. It also offers great investment security for operators of refrigeration systems, since the refrigerant bans of the EU regulation on fluorinated greenhouse gases don’ t apply to it.

Efficient for low refrigerating capacity ranges

The refrigerant ammonia dimethyl ether consists of 60 %( by mass) of ammonia( R717) and 40 % of dimethyl ether( RE170)— a propellant gas whose refrigerant properties are similar to those of isobutane. Thanks to its azeotropic boiling behaviour, the mixture can be used like a mono-refrigerant, that is, there is no concentration shift during evaporation or condensation. R723 is particularly efficient in the low capacity range up to 100kW.

The circulating volume flow rate of the vapour phase is about 150 % of that of ammonia, which means acceptable pipe cross sections and flow velocities even for lower refrigerating capacities. Also, R723 has a higher volumetric refrigerating capacity than ammonia, so it is possible to obtain considerably higher refrigeration capacities with the same quantity of R723. In refrigerating systems tested with both ammonia and R723, the coefficient of performance( COP) improved by 7 % when using the latter. Besides its energy efficiency, the azeotropic mixture also features a high

The environmentally friendly and cost-efficient refrigerant R723 convinced the foodproducing company Herrmannsdorfer Landwerkstätten.

performance coefficient and good oil solubility.“ In principle, ammoniabased cooling systems can be filled and operated with R723. However, the individual application must always be taken into consideration— this is why the conversion should always be clarified with the individual component manufacturers,” explains Bernd Kaltenbrunner, member of eurammon and CEO of KWN Engineering GmbH.

The energy efficiency of the azeotropic mixture is complemented by a high performance coefficient and a high level of oil solubility. A further great advantage results in the about 15K lower

1 2

1. Th. WITT Kältemaschinenfabrik GmbH installed a chilled-brine compact refrigeration unit, tailormade for the specific requirements of Herrmannsdorfer Landwerkstätten.