Theoretical And Experimental Research On The Flammability Hazards Of An Air Conditioner System Using Refrigerant R290 And R32

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 R32 and hydrocarbon refrigerant R290 are under consideration.Whilst R290(propane)and R32 have favourable system performance,environmental characteristics,they are flammable substance,thereby posing additional risks.This study addresses the associated flammability concerns through a number of risk-related sub-studies as below.The explosion parameters explosion pressure and explosion pressure rise rate of R290 and R32 were studied by using 20 L ball explosion experimental device.It is found that the maximum explosion pressure of R32 is slightly higher than R290 when the initial pressure is atmospheric environment.In order to evaluate the likelihood and consequences of ignition,it was necessary to first study the distribution of R290 after it has leaked in the room.The study was done in a specially built a test room.In these tests,we measured R290 concentrations arising from a leak under different scenarios in order to understand the development of concentrations which may approach the LFL.It is found that 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 leak of refrigerant.To determine the potential range of damage arising from ignition of a leak,a number of experiments were conducted to ignite R290.After R290 leak and encounter an ignition source may explode,the maximum explosion 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 peak heat release rate is about 1000 kW.The plastic shell of indoor unit is the main source of heat of combustion and smoke.The blasting consequences were studied after the outdoor unit leakage.The blasting occurred near the outdoor unit and in the outdoor unit has not significant damage to the adjacent outdoor unit and itself.But in the process of R290 leakage encountered an ignition source,a continuous burning of the R290 refrigerant occurs.Under this scenario it is feasible that the outdoor unit bruned completely.The combustion products was studied after the indoor unit ignited by an external fire when the air conditioner using R290 and R22.The CO2 and CO were measured in these experiments.In addition,the concentration of HF that was produced by combustion or thermal decomposition was analyzed.