SEPCOO - Simulation-based development of charge-minimized propane modules to improve the performance of CO2 refrigeration systems

Project: Research project

Project Details


Due to the provision of the F-Gases Regulation, natural refrigerants such as carbon dioxide (CO2 or R744) and propane (R290) are finding increasing use in refrigeration. R744 as a refrigerant has found its way into refrigeration and deep-freeze systems in the industrial sector, especially in food production and processing. Variable loads and the dynamic behaviour of the overall system during operation lead on the one hand to challenges in the control and design of the components, and on the other hand to reduced efficiency. However, the dissipation of waste heat from industrial refrigeration systems in the event of a short-term increase in cooling capacity or higher outside temperatures (above approx. 27 °C), above which a transcritical mode of operation of R744 refrigeration systems occurs, leads to a significant increase in flash gas during throttling. This causes a drop in the R744 refrigeration capacity or an effort in compression due to the strongly dependent efficiency on the outside temperature. To achieve the desired refrigeration capacity at all operating conditions, a larger sizing of the refrigeration system is required. To improve the efficiency of R744 refrigeration systems, especially in transcritical operation or at higher outdoor temperatures, and thus to increase their areas of application or to smooth load fluctuations, various "subcooling methods" for lowering the R744 temperature before throttling have been investigated in recent years - mainly theoretically. In the food industry, cooling capacities of approx. 70 - 100 kW are usually required, resulting in a necessary "subcooler capacity" of approx. 10 - 30 kW to achieve a sufficiently low R744 temperature. In this project, the subcooling by utilizing R290 refrigeration cycles (R290 modules) shall be investigated by means of simulation and experiment. The possible increase in capacity can be used to cover peak loads, which means that the R744 refrigeration system can be better designed for the predominantly occurring partial load. As a result, the plant can be designed more compactly, built more cost-efficiently and the operational reliability during load fluctuations can be increased due to the subcooling, which is independent of the outside temperature.
Effective start/end date1/12/2131/05/24


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