Explosion risk analysis of isobutane leakage in the freeze and cold storage system

Abstract

The leakage and explosion of flammable refrigerant in household air-conditioning, domestic refrigerators, and heat pump system, which could pose huge threats to the building, ecological environment and the human health. Isobutane (R600a) is expected to be employed in the small-sized freeze and cold storage (FCS) system, nevertheless, the flammability slows down its development. Leakage, diffusion, distribution, and deposited characteristics of refrigerant in limited space are essential for explosion risk analysis in public places. To promote the safety application of R600a, a three-dimensional refrigerant leakage numerical model based on refrigerant leakage and diffusion (RLD) is established for RLD process, and the reliability of the model is verified by the experimental results. On this basis, the effects of different factors on the RLD process are analyzed by the numerical simulation. The results indicate that there is pessimism in the fan speed of the supply-air fan to obtain the highest average R600a concentration of defrost heater (DH) in the deposition process. The refrigerant explosion risk with the system door opened in the deposition process is markedly superior to that of the system door closed. As the leakage hole diameter increases from 1.0 mm to 2.5 mm, the average R600a concentration of the DH at the simulated time of 300 s is increased by 1.71 vol%. This study, not only reaffirms the benefit of using a three-dimensional refrigerant leakage numerical model for flammable refrigerant of the FCS system in a limited space, but also provides some rules of the RLD process with different factors.