R744 REFRIGERATION SYSTEM CONFIGURATIONS FOR SUPERMARKETS IN WARM CLIMATES

摘要

Commercial refrigeration systems applying R744 as the only refrigerant still have a large potential inrndevelopment regarding energy efficiency, heat recovery and cost efficiency. Special focus and emphasis hasrnto be given to the system architecture with respect to increase the system efficiency when these units arernoperated at elevated ambient temperatures. The objective of this thorough theoretical study is to investigaternthe energy required for different R744 refrigeration systems at 25-50-75-100% cooling load conditions. AllrnR744 system configurations are assumed to operate at high ambient temperatures (from 30 to 42 ℃) whichrnmean only transcritical operations are considered for the following system configurations. Some alternativesrnare sustainable and viable competitors to conventional HFC supermarket refrigeration systems, up to nowrnapplied in warm climates:rn1.Standard booster cycle (baseline)rn2.Expander cycle (expander → electrical generator)rn3.R744 booster cycle with a mechanical subcooler (MS) unit: working fluid MS: hydrocarbonrn4.Economiser I cycle (with a flash tank, i.e. parallel compression)rn5.Economiser II cycle (without a flash tank; i.e. parallel compression)rn6.Ejector supported parallel compression systemrnThese different cycles are evaluated with advanced spreadsheets assuming realistic componentrnperformances.