Performance improvements of supermarket R744 systems by pivoting compressor arrangements

Abstract

The adoption of the EU F-Gas regulation 517/2014 and the development of the Multi Ejector concept have led CO2 to take center stage as one of the preferred solutions in several applications, at the expense of synthetic refrigerants. Despite the expected significant energy saving in warm climates using the Multi Ejector, the increase in investment costs and level of complexity would hinder its spread. In this work a numerical and experimental campaign have been performed to explore the implementation of “pivoting” compressors, i.e. a technique that enables the medium temperature (MT) and parallel (IT) compressors in a booster system to be interchangeable according to cooling loads, ambient conditions and ejector capacity. The novel configuration presented in this work helps to downsize the installed compressor capacity in ejector-supported systems while maintaining all the benefits due to the ejector. The basic version of the solution is based on: i) MT and low temperature (LT) compressors, ii) high pressure controlled through a Multi Ejector both during summer and winter conditions. The tests performed in the laboratory proved how the “pivoting” solution is beneficial to attain a higher degree of flexibility with more compact systems while maintaining the efficiency and justifying economically the ejector implementation. An additional solution called LT “pivoting”, i.e. connecting LT compressors either to MT or IT compressors, proved to be particularly useful for energy saving.

Performance improvements of supermarket R744 systems by pivoting compressor arrangements