Briefs: Reducing the TEWI by reducing channel size

The TEWI (Total Equivalent Warming Impact) makes it possible to measure the total impact of a system on global warming. The direct effect is produced by refrigerant loss. The indirect effect is produced by the CO2 released when producing the electricity operating the system. In order to minimize this, Cemagref is seeking to reduce the overall TEWI of refrigeration systems by reducing the size of the exchangers' channels. The studies aimed primarily at demonstrating that the use of mini-channels was compatible with thermal and energy efficiency. Fundamental research concentrated on pressure drops in small-diameter pipes and modelization of energy efficiency and consumption. This led to the construction of a prototype allowing for a 10-fold reduction in refrigerant for the same energy efficiency. The applications concerned account for 16 000 tonnes of refrigerant, which could be reduced to 2000 tonnes, not to mention potential air-conditioning applications. The direct TEWI could be reduced by 90% and the indirect TEWI by 10-20% which led to an expected overall TEWI reduction of approximately 50%. Applying this technology to the 600 000 systems in France alone could lower CO2 equivalent annual emissions by up to 1 200 000 tonnes, i.e. approximately 2% of the French energy sector's greenhouse gas emissions.