抄録
The demand for cooling has increased in the world, which causes increase in electric power consumption. The reduction of carbon dioxide emissions caused by the generation of electricity is important to inhibit global warming. As a solution, we can use ejector refrigeration cycles driven by thermal energy such as solar energy and exhaust heat. This report aims to evaluate ejector refrigeration cycles by using exergetic efficiency. Two evaluation methods by using exergetic efficiency are applied. The first one is that exergetic efficiency of the system, which is not included heat exchanger part, is calculated under constant temperatures at a generator, an evaporator and the environment for comparing other performances reported so far. The second one considers the temperature change of external fluids in the heat-exchangers in a generator and an evaporator for analyzing the details in the system. The experiments with R-245fa were conducted in the low generating temperature range from 60°C to 72°C. We can operate the ejector refrigeration cycle in the lower generating temperature range compared with the other reports. The operations at the lower-temperature heat sources indicate the possibility of utilization of solar heat and exhaust heat of air-compressors in the industrial fields. The exergetic efficiency is lower than that of the other reports using the higher generating temperature because the technology for using smaller exergy of lower-temperature heat source becomes difficult. Another exergy in the case of changing the temperature of working fluids in the process of heat transfer becomes about a half of the exergy of constant-temperature calculation.
