Effects of temperature and pressure on quenching distances of difluoromethane (R32) and ammonia (R717)

Abstract

Temperature and pressure effects on quenching distance have been studied for difluoromethane (R32) and ammonia (R717), two mildly flammable refrigerant gases. By studying ignition and quenching behavior in conditions beyond standard test conditions, the authors aimed at understanding whether combustion takes place in practical situations. First, the quenching distance of R32 and R717 in the temperature range of 298 to 333 K and pressure range of 0.79 to 1.12 atm was measured. The quenching distance decreased slowly with increasing temperature and decreased steeply with increasing pressure. Second, the authors examined the relationship between quenching distance and burning velocity at various temperature and pressure. It was found that quenching distance is essentially related to (unburned gas density × burning velocity)−1, and changes in quenching distance observed in the present experiment can be explained by the temperature and pressure dependences of burning velocity and unburned gas density. It was also found that the quenching distance and burning velocity for R32 were not affected much by the humidity of air in the practical condition.