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Free Cooling by Circuit of Refrigerant

EuroNorm GmbH - INNO-KOM-Ost - MF130061

11/2013 - 03/2016

Dr.-Ing. Peter Röllig


Free Cooling, Circuit of Refrigerant CO2

Aim of Project

Currently Free Cooling is usually implemented by means of an intermediate circuit of a cooling medium.  Aim of the project was the development of a Free Cooling process as a refrigerant circulating system (analog heat pipe principle), but without such an additional intermediate circuit. In that way the annual share of Free Cooling could increased by approximately 20%. Primarily this is the effect of non-use of intermediate circuit.


The aim of the project was achieved. A Free Cooling process with pump circulation of refrigerant was developed. For this a common refrigerant circuit is expanded substantially by a vertical pipe (refrigerant collector) and a refrigerant pump. For ecological but also technical reasons CO2 is used as refrigerant in this circuit. A prototype was constructed. Measurement tests were performed. The function of this Free Cooling system was demonstrated. The change over switching between the compressor operation and Free Cooling operation was successfully tested. A variety of measurements were carried out.

Areas of application 

The practical implementation of this Free Cooling system could be for year-round full load cooling applications (direct expansion systems). For example: cooling of electrical switchgear, information technology, server rooms, data centers etc.


Further investigations are planned. For achieving Free Cooling load even in times with high outside temperatures an additional component for adiabatic humidification of the air will be installed at the outdoor heat exchanger. Measurement tests will performed. 

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Institut für Luft- und Kältetechnik - Gemeinnützige Gesellschaft mbH
Bertolt-Brecht-Allee 20, 01309 Dresden

Secretary to the Management



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