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Comparative risk assessment of hydrocarbon refrigerant in a refrigerator and split air conditioner
Abstract
The use of flammable refrigerants, such as HC-290 (propane) as an alternative to HCFC-22 in room split air conditioners (SACs) is being pursued. However, there are concerns that at present the experience with SACs using HC-290 is small compared to the potential scale of use. Having said this, there is extensive experience with hydrocarbons (HCs) in domestic and small commercial refrigeration globally, where the market for HC-600a (iso-butane) appliances is several times that of SACs; such experience can be used to extrapolate the safety implications to the wider use of HCs in SACs. This study uses established quantitative risk assessment (QRA) methods to estimate the frequency and severity of ignition of HC-600a refrigeration appliances, which corresponds to the risk so far based on experience. The same methods are similarly applied to SACs using HC-290, adjusting for their particular physical and operational characteristics, to estimate a corresponding risk for the projected market of these appliances. The results show that the frequency and severity of ignition of the SACs are much lower than that for refrigerators on account of the installation characteristics of the SAC being more conducive for dispersion of leaked refrigerant and less potential for confinement in the event of deflagration.
A major challenge in industrial fire protection is controlling the impact from large, open hydrocarbon fires. The primary mechanism for injury of damage from such fires is thermal radiation. Depending on the circumstances and conditions leading to such an event, a different type of open fire may result. For example, ignited releases can produce pool fires, jet flames, vapor cloud fires, or fireballs, all of which behave differently and exhibit markedly different radiation characteristics. This chapter presents detailed techniques for calculating impacts from large, open hydrocarbon fires. Examples are included throughout this chapter to illustrate the application of these expressions. © Society of Fire Protection Engineers 2016. All rights reserved.
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This study addresses the flammability risk of hydrocarbon (HC) refrigerants within horizontal type ice cream cabinets (ICC). Quantitative risk assessment (QRA) is used to estimate the likelihood of ignition of leaked refrigerant and severity of the consequences. Variables were evaluated including effect of room size, positioning of ICC, compressor compartment fan airflow and ignition source distribution. To strengthen the QRA, tests were carried out for refrigerant leakage and effects of ignition to validate dispersion and consequence models. Ignition frequency is between 1 × 10−8 and 2 × 10−13 per year. The maximum overpressure and thermal intensity within the room is 3 kPa and 200 s (kW m−2)4/3, respectively and 6.5 kPa and 20 s (kW m−2)4/3 from within the compressor compartment. The risks were found to be negligible compared to background and other reference values.
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 hydrocarbons are under consideration. Whilst R-290 (propane) has favourable system performance, environmental characteristics and cost, it is a flammable substance, thereby posing additional risks. This study addresses the associated flammability concerns through a number of risk-related sub-studies. These include evaluating the distribution of R-290 following a leak in room, overpressure arising from ignition of a flammable mixture, severity of a secondary fire and total heat release rate in the event of an external fire imposed upon an R-290 system. It is found that the possibility of refrigerant existing within the flammable range is limited only to the region very close to the indoor unit. Besides, low overpressures in the event of ignition and limited additional heat flux in the event of external fire were registered.
Hydrocarbon refrigerants present are fire and explosion hazards due to their flammability. This paper describes a quantitative risk assessment (QRA) model to evaluate the potential for ignition when hydrocarbons are employed in stationary refrigeration and air-conditioning equipment. QRA enables examination of the effects that design, installation of equipment and external conditions on the frequency of ignition of the refrigerant and its consequences. Part I of this study presents the modelling approach for ignition frequencies, sub-models for refrigerant leakage and development of flammable concentration, and the associated consequences, being overpressures and thermal radiation. Part II provides recommended empirical input data and example results generated from the model.
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