Analysis of the Energy Efficiency of Technical Solutions of the Heat-Driven Ship Ejector Refrigeration Machine for Obtaining Sub-Zero Temperatures

Abstract

Marine refrigeration machines are responsible for large amounts of electricity consumption, as well as direct emissions of high global warming potential (GWP) refrigerants, so they need to be gradually upgraded. The possibility of using a ship ejector refrigeration machine with two-stage compression, consuming waste heat, as well as a cascade compression-ejector refrigeration machine to obtain the temperatures of minus 28–27 °C was analyzed. It was shown that the traditional indicator of the efficiency of heat-driven refrigeration machines COPtherm ot be recommended for the selection of energy-efficient modes of operation of ejector refrigeration machines that consume waste heat. As a criterion for the energy efficiency of ejector refrigeration machines that consume waste heat, it is proposed to analyze COPmechTot, which takes into account the electric power of pumps, fans, as well as units that provide “feeding” the refrigeration machine with waste heat. A two-stage ejector refrigeration machine that consumes waste heat with a temperature of 95–45 °C and is intended for the operation of a ship ice generator (boiling temperature — 28 °C) loses to a traditional vapor compression refrigeration machine in terms of energy consumption: COPmechTot = 1.266 vs. COPmechTot = 1.52. A cascade vapor compression ejector refrigeration machine that consumes waste heat with a temperature of 85–95 °C and is designed to provide refrigeration (boiling temperature — 27 °C) of ship provision chambers is more attractive than a traditional vapor compression one: COPmechTot = 2.37 vs. COPmechTot = 1.82. An alternative technical solution for the production of sub-zero temperatures on ships, which the authors plan to consider in further research, is a refrigeration machine with two-stage compression. It uses a compressor in the first stage and an ejector in the second stage. Bibl. 26, Fig. 7, Tab. 1.