Les risques d'inflammabilité des conditionneurs d'air utilisant le R290 (propane)

Le R290 (propane) suscite beaucoup d'intérêt en tant que frigorigène alternatif aux HCFC pour les conditionneurs d'air individuels, du fait de son GWP négligeable, de ses performances et de son coût modéré. Cependant, il fait l'objet de questions liées à son inflammabilité.
R290 (propane) attracts a lot of interest as a replacement refrigerant of high-GWP HFCs – mainly R410A – and HCFCs for household air conditioners, due to its negligible GWP, favourable system performance and relatively low cost. However, it raises some questions due to its flammability.

A recent article presented in the International Journal of Refrigeration (IJR) provides valuable information on this issue. W. Zhang et al. report* on the results of a project – funded by the Ministry of Environmental Protection of China – including an extensive series of experimental and numerical sub-studies carried out to examine the flammability hazards of using R290 in room air conditioners.

Based on these investigations, the following general conclusions are drawn by the authors: the flammable range of a release of R290 is only located within the close locality of the indoor unit, implying that only sources of ignition present in the immediate vicinity of the indoor unit have the possibility to ignite a refrigerant leak.
It is only possible for ignition to occur when the leak mass flow rate is extremely high and there are some means by which the release can be diffused to a sufficiently large flammable volume.
In the event of ignition, the maximum overpressure within the room is about 6.5 kPa, which was insufficient to damage doors or windows.
The most dangerous situation is if R290 is ignited during the leak process and continuous burning of the refrigerant occurs. Under this scenario, it is feasible that the secondary event of the plastic casing of the indoor unit could be ignited.
If this occurs, a lot of smoke can be generated which can have a significant impact on personal safety of room occupants. If an external fire was to engulf the air conditioner charged with R290, the total heat release of the burning indoor unit may increase by about 12%, compared to one charged with no refrigerant.
The heat release is about 1000 kW. It is observed that the refrigerant piping joints can give way soon after the indoor unit is ignited, acting as a sort of pressure-relief device, leading to a release of refrigerant, avoiding a dangerous build-up of high pressure.

* Research on the flammability hazards of an air conditioner using refrigerant R-290, W. Zhang et al., IJR, Volume 36, Issue 5, August 2013

This article can be downloaded via the IIR’s Fridoc database (free for IIR members within the framework of their quota of free downloads): http://www.iifiir.org/clientBookline/service/reference.asp?INSTANCE=exploitation&OUTPUT=PORTAL&DOCID=IFD_REFDOC_0008138&DOCBASE=IFD_REFDOC_EN&SETLANGUAGE=EN
Remember to log in or register first!