injection scroll compressor, variable speed, intermediate conditions, compressor correlation
Vapor-injection scroll compressors (SCVI) are present in the market since many years. There are several studies in the literature dealing with their proper characterization and the development of correlation in order to estimate properly its intermediate working conditions. The main objective of these correlations is the prediction of the compressor behavior for any condition based on a reduced number of test. Derived from that a correlation would be better as less parameter it will require, as this will imply less number of test in order to determine it. Nowadays, variable speed SCVI are being installed more widely but not so much studies are available for these type of compressors. In this work, based on previous correlations obtained for constant speed SCVI, a correlation for variable SCVI has been obtained. In order to do that, a set of experimental calorimetric test has been conducted for different condensing and evaporating temperatures and 4 different compressor speeds. From these data, it has been possible to obtain a correlation depending in four parameters able to predict the intermediate conditions (pressure and temperature), the mass flow rates and the energy consumption with an error lower than 3%. The correlation has been checked with other sources of data available in the public literature obtaining similar deviations from the measured values. Finally and based on these results, the optimum intermediate operation conditions for an injection heat pump with an economizer has been determined in different external conditions. From the optimization process an improvement in COP up to 5% could be expected from the theoretical analysis.