Transcritical applications

Transcritical systems with R744 are the state of the art in commercial refrigeration. The systems are increasingly developing into complete integrated solutions with low and medium temperature applications, air conditioning and heating by means of heat recovery. In addition, measures are increasingly being taken to further improve efficiency while also reducing the cost of the systems. The optimal interaction, or the best possible control of the individual system components, forms the basis for year-round system efficiency, a long compressor lifetime and thus a high level of operational reliability.

The long-term, fault-free operation of a compressor can only be ensured if:

• The quality, design and suitability, as well as the perfect material condition and function of all components of the compressor are guaranteed.
• The permitted operating conditions are complied with.
• A control of the refrigerant mass flow is ensured which is not too dynamic.
• The oil supply/lubrication is ensured (pay attention to oil temperature and refrigerant concentration in the oil). This also includes a stable oil return from the system and a functioning oil management system (Ölmanagement), especially in compound systems with extended pipe works.
• Harmful foreign substances in the system, such as moisture, non condensable gas, dirt, chemical residue, metal oxides and swarf are minimised.

The following chapters provide information and instructions on how to classify system characteristics such as the quality of the control (control accuracy), the selected coverage of the minimum load, the type of desuperheating of the suction gas and the oil management – even in the case of conflicting requirements – and how to act accordingly.