Explosion Hazard Evaluation On Refrigerants R32/R1234ze(E)

Under the requirements of environment development,refrigerant as the important working fluid is constantly updating in the refrigeration industry.R32?CH₂F₂?and R1234ze?E??CHF=CHCF₃?are promising mildly flammable?A2L?environmental refrigerants that do not deplete ozone.R32 has been applied to household air conditioners by air conditioners enterprises such as Daikin and Gree.The addition of the R1234ze?E?can decrease the greenhouse potential and improve the performance of the refrigerant.During the operation and installation of the air conditioner,the blockage of the circulation flow path and the leakage of the refrigerants may cause a mildly flammable refrigerant explosion accident.To evaluate the explosion hazard of R32 and R32/R1234ze?E?,the open-space gas cloud explosion experimental system is built and the soap bubble method is used in the cloud explosion experiments.Limiting oxygen contents?LOC?of various equivalence ratios???,flame propagation behaviors and explosion pressure behaviors of various?and oxygen contents(x_O2)are obtained.Combustion reaction mechanism of HFCs provided by NIST is used to calculate parameters of chemical reaction kinetics and to conduct the sensitivity analysis.According to change of adiabatic flame temperature,thermal expansion ratio,Lewis number and flame thickness,the effects of?and x_O2 on the mechanisms of the flame instability are revealed.The maximum explosion pressure,the maximum rate of pressure rise,positive pressure impulse,negative pressure impulse,laminar burning velocity?S_L?of different?and x_O22 are analyzed and the factors affecting S_L are revealed.The explosion hazard of refrigerants systems with various blending ratios of R1234ze?E?as 0,10%and 20%is evaluated.Flame propagation speed decreases with the decrease of x_O2.Buoyance force shows significant effects at low oxygen content conditions due to the low S_L.Diffusional-thermal instability and hydrodynamic instability lead the flame instability at high oxygen content conditions.Due to the increasing ratio of fluorine to hydrogen atoms and C=C in the mixture of R32 and R1234ze?E?,deficient combustion produces plenty of soot which decreases the rate of combustion and the temperature of flame.With the decreasing?,flame color changes in blue,green and orange.The explosion hazard of the system rises first and then falls with the addition of R1234ze?E?.The 90%R32/10%R1234ze?E?system is most damaging with lower LOCs and higher pressure destructive.CHF₂+O₂=>CF₂:O+O+H and H+O₂<=>O+OH are important elementary reactions with positive effects on S_L while CHF₂+H=CHF+HF,CF₂:O+H=CF:O+HF,CF₂+O=CF:O+F and CF+O=CO+F show significant negative effects.