Topical Article: Project to develop Next-Generation Refrigerants and Refrigeration and Air-Conditioning Technology to achieve Energy Conservation and Mitigate Global Warming

The New Energy and Industrial Technology Development Organization (NEDO) in Japan conduct research and development to establish safety and risk assessment methods for next-generation refrigerants used in commercial refrigeration and freezing equipment as well as residential air-conditioners. Support is provided for product development and the development of ultra-low GWP refrigerants to solve technical issues that hinder the practical application and dissemination of next-generation refrigerants. Synopsis of the different research and development activities are provided below.

Evaluation of thermal characteristics, heat transfer characteristics, and basic cycle performance of next-generation refrigerants used in small and medium-sized refrigeration and air conditioning equipment. Based on the physical property values measured in this project and other research data, the equation of state for a next-generation refrigerant is being developed.

Safety evaluation of low-GWP, low-combustible refrigerant mixtures. In this research, a mixture of a highly combustible refrigerant having three or fewer carbon atoms, such as fluoroolefin, and a low-combustible refrigerant, such as fluoroalkane, is targeted as a next-generation refrigerant for refrigeration and air-conditioning equipment. Mixtures are selected considering total GWP, boiling point difference and availability, and the mixing rules for the combustion characteristics of the refrigerants are experimentally and accurately evaluated.

Research and development of practical evaluations for next-generation refrigeration and air conditioning technology using low-GWP refrigerants. This research aims to develop technologies capable of high-accuracy theoretical and test evaluation of the performance of air-conditioning and refrigeration equipment that introduces next-generation refrigerants. Furthermore, to predict the performance of next-generation refrigerants, a performance simulator is being developed.

Development of safety/risk assessment methods for next-generation refrigerants. In this research, items necessary for the safety/risk assessment of flammable next-generation refrigerants have been evaluated and establish safety/risk assessment methods through numerical calculations, laboratory experiments, and outdoor experiments. Research is also being conducted on the suppression of disproportionation reactions.

Establishment of physical risk evaluation method for combustion of next-generation refrigerants considering ignition sources in an actual use environment. In this research, equipment and phenomena capable of acting as ignition sources are extracted when a highly flammable hydrocarbon refrigerant, expected to serve as a next-generation refrigerant, is used. In evaluations of the combustion effects of split air-conditioner indoor units, an ignition test is conducted by installing a steel container at the field test site.

Eiji Hihara*1, Toru Sano*2, *1 Project Leader at NEDO, *2 Project Manager, NEDO Environment Department

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