Optimization of parallel compression systems.

Trans-critical CO2 systems with parallel compression already represent state-of-the-art technology in commercial refrigeration. Different measures are currently being evaluated in order to further improve the efficiency, especially with respect to different ambient and therefore, different operating conditions. The systems turn more and more into integrated solutions, for low- and medium temperature load as well as air conditioning and heating, in order to cope efficiently with different ambient conditions and offering at the same time high annual energy efficiencies. Perfect interaction between and control of the individual system
components are the basis for optimum system efficiency throughout the entire year for a given location. An important factor in this respect is the intermediate pressure inside the receiver and its effect on the overall efficiency of the system. This paper provides an analytical and experimental study of different control strategies and their effects on the annual energy efficiency. The experimental facility utilized, is a newly designed trans-critical CO2 booster system which is installed by BITZER at its Rottenburg site for practical
training seminars.