Research on the flammability hazards of an air conditioner using refrigerant R-290

• Different hazards of R-290 applied as a refrigerant are studied.
• R-290 concentrations arising from a leak under different scenarios were measured.
• Developments of concentrations which may approach the LFL are found.
• The severity of a secondary fire from ignition of a leaked R-290 is emphasized.
• The effect of an external fire which ignites an R-290 air conditioner is shown.

Currently, hydrochlorofluorocarbons and hydrofluorocarbons are the most common refrigerants used for air conditioners. Due to ozone depletion and high global warming potential, environmentally benign options such as hydrocarbons are under consideration. Whilst R-290 (propane) has favourable system performance, environmental characteristics and cost, it is a flammable substance, thereby posing additional risks. This study addresses the associated flammability concerns through a number of risk-related sub-studies. These include evaluating the distribution of R-290 following a leak in room, overpressure arising from ignition of a flammable mixture, severity of a secondary fire and total heat release rate in the event of an external fire imposed upon an R-290 system. It is found that the possibility of refrigerant existing within the flammable range is limited only to the region very close to the indoor unit. Besides, low overpressures in the event of ignition and limited additional heat flux in the event of external fire were registered.

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