Airflow to disperse refrigerant leaks from hydrocarbon refrigeration systems✰.

• Theoretical and experimental characterisation of the dilution process of leaks in indoor unit airflow. • Formulae to determine minimum indoor unit airflow to dilute leaks to below LFL. • Measurements to examine dilution of stratified layer of refrigerant-air mixture in room. • Methodology developed to determine response time and leak rate for initiating airflow. Whilst R290 is currently used to a limited extent in room air conditioners there is a desire for wider application due to its excellent performance and negligible global warming potential. The product standard IEC 60335–2–40 specifies requirements to limit the allowable refrigerant charge in such a way that it obstructs the wider use of R290. Airflow of an indoor unit can be used to dilute a refrigerant leak, enabling substantially greater charge quantities to be used. A numerical model based on entrainment theory was developed and supported by analysing the behaviour of experimentally simulated releases under various conditions with indoor unit airflow. The work determines the minimum airflow rate necessary to prevent formation of a flammable concentration within the room. Further, the work includes determination of appropriate response time and leak rate to initiate airflow once a leak has begun. The developed methodology can equally be applied to commercial refrigeration units and other flammable refrigerants. [ABSTRACT FROM AUTHOR]