Investigation of the application safety of R-290 in residential air conditioning systems

Abstract

In the context of energy conservation and reduction of greenhouse gas emissions, there has been considerable attention focused on the application of the natural refrigerant R-290 (propane) in residential air conditioning (AC) systems. An ignition event can occur once R-290 is released from residential AC systems and encounters an ignition source within an indoor environment. For studying the application safety of cabinet AC systems, this paper employs Computational Fluid Dynamics (CFD) to simulate the release of R-290 in residential rooms and derive the real-time flammable volume during release. The most hazardous cases are identified by analysing the effects of practical influences such as release rate, release location, air supply velocity, room size, and furniture arrangement. On this basis, the frequency of ignition events is calculated under the selected leak hole in conjunction with a quantitative risk assessment methodology. The results show that when the airflow is off, the most hazardous case is the flow of refrigerant into the room after being obstructed by the enclosure, whereas when the airflow is on, the most hazardous case is the direct release of refrigerant from the air supply outlet into the indoor space. With the charge limits required by the IEC standard, the frequency of indoor ignition events in R-290 cabinet AC systems does not exceed 10−10 triennially. This study investigates the flammable volume and the frequency of ignition events associated with R-290 leakage, which is useful for analysing the safety measures for R-290 applications in residential AC systems.