MINIMUM AIRFLOW RATES TO DILUTE 8290 CONCENTRATIONS ARISING FROM LEAKS IN ROOM AIR CONDITIONERS

Currently R290 is used to a limited extent in room air conditioners, such as split, portable and window types. The product standard IEC 60335-2-40 currently specifies requirements to limit the charge of flammable refrigerants in such a way that it obstructs the wider use of R290. This is particularly challenging in warm countries where the heat load is greater and thus charge sizes need to be larger for a given room size, inferring higher concentrations in the event of a leak. Relying on the airflow of an indoor unit can be used to dilute a refrigerant leak and thus prevent flammable concentrations forming, despite the charge quantity being substantially greater than that currently permitted in the current standard. Research has been carried out to determine the minimum airflow rate from an air conditioner necessary to achieve sufficient dilution. A numerical model based on entrainment theory was developed and supported by experimentally analysing the behaviour of releases under various conditions with RACS airflow.