Refrigerant leak detector, flammable refrigerant, A2L safety, concentration change, experimental step change response, modeling
As the HVAC&R industry is moving towards low-GWP refrigerants, many flammable working fluids are being considered. While these refrigerants perform quite well in terms of capacity and efficiency, the widespread use of flammable fluids will require changes to the way systems are designed and manufactured to address new safety codes and guidelines related to building design, HVAC&R installation and service requirements. This paper presents the results of a recently completed AHRTI study aimed at exploring the suitability of different leak detectors when exposed to A2L refrigerants. The sensing principles investigated include NDIR, micromachined membranes, MOS, and thermal conductivity-based sensors. R32 was used as the test fluid. An experimental facility to investigate sensor response to a step change in concentration has been designed and put into service. In order to evaluate sensor response to more realistic refrigerant release scenarios, research has also been conducted to address time-varying concentration profiles that would be encountered, for example, during release in a machinery room or residential setting. The paper also presents modeling results in which experimental step change responses were used to perform sensor characterization. This data can then be used to accurately predict the performance of the same sensor when exposed to a realistic, time-varying concentration.