ICR2007: CO2 in the limelight

Among the 876 papers presented at the IIR International Congress of Refrigeration in Beijing, 82 were on CO2 as a refrigerant or secondary fluid. Many dealt with new components for CO2, the lack of such components being currently still one of the main obstacles to a wider use. Here is a glimpse of the new developments presented: - Toublanc et al. have presented a new CO2 cycle based on isothermal compression used in different ways: oil injection increases the overall efficiency by 30% depending on the injection rate and multistage intercooler compression is promising for high cooling rates, as the COP rises 38% when using 5 compression stages. - Jakobsen et al. have presented promising results of tests on a 40 kW liquid chiller using CO2 which can reject heat both to air and water. - Reinhold et al. have presented results of tests on the optimization of an industrial CO2 cascade system, spiral freezer and ice-cream freezer. - Boulaws Ksayer et al. have presented a CO2 ejector which should improve the COP of the transcritical cycle by more than 15% compared with the basic transcritical cycle for typical air-conditioning operating conditions. - Zha et al. have also presented CO2 transcritical ejectors for residential air-conditioning units which look promising even if a lot of investigation is still needed. - Zeng et al. and Yang et al. have presented the test results obtained using CO2 rolling piston expander which could replace throttle valves as an effective method of improving the performance of the CO2 transcritical refrigeration cycle. Order the ICR2007 proceedings: www.iifiir.org