Flammable refrigerant leakage hazards control for split-type household air conditioners

Propane (R290) is expected to be employed in air conditioners and heat pumps, whereas the flammability slows down its uptake. In this study, the leakage hazards control of an R290 split-type household air conditioner (STHAC) with 5 mm diameter finned-tube heat exchangers under off-mode were investigated through concen-tration measurement and ignition experiments. The critical releasable charges under which a fire may or may not occur at different installation heights were obtained and examined through ignition test. A refrigerant pump -down method was proposed to evacuate the R290 in the indoor unit (IDU) by the compressor to below the critical releasable charge under off-mode. Therefore, the leakage hazards would be enormously decreased, and it could be equally used for other flammable refrigerants or commercial refrigeration units. Besides, a deconvo-lution method was employed to correct the deviation of measured R290 concentration caused by response time. It is found that the critical releasable charge was 4.3 g and 8 g under a 1 mm leak hole at 1.8 m and 2.2 m installation height of IDU respectively with 1.5 m ignition height from the floor. A formula was proposed to acquire the number of compressor revolutions during the pump-down process. Moreover, the deconvolution method could effectively correct the deviation caused by the response time, but the deconvoluted concentration was still lower than the actual concentration due to the "averaging" effect at the inlet and sample cell of the detector, especially under a small releasable charge below 17.8 g.