This research was sponsored by ASHRAE Technical Committee (TC) 4.3. The purpose of the research is to update ASHRAE Standard 15, especially the calculation of the required ventilation rate in 8.11.5. A search for the historical roots of the basis of this approach indicates that this formula was likely developed before 1930. The current formula suggests that the appropriate ventilation rate to flush a refrigerant during a leak is proportional to the square root of the mass of the refrigerant in the largest system in the room. This equation does not account for variations in the maximum acceptable concentration (if refrigerant concentration limit – RCL), does not account for the difference in refrigerant properties such as boiling point, vapor pressure, molecular weight, and does not account for different room sizes. A more rigorous and scientifically sound approach yields a technically defensible rationale for ventilation requirements in refrigeration machinery rooms to maintain safety.
This research examines recorded accident scenarios to develop an appropriate leakage scenario and a ventilation requirement that takes into account several important parameters: the mass of the refrigerant, refrigerant properties, the volume of the room, the delay in detections, and the recommended concentration limit suggested for health and safety purposes. After determining an appropriate, time-varying emission rate, a mass balance e equation is used to determine the concentrations of the refrigerant in the room. The refrigerant concentration in the room is kept below the recommended concentration limit by adjusting the ventilation rate.
A simple formula is provided to calculate the ventilation rate using several constants that are specified or calculated based on room and refrigerant characteristics. The needed constants have been provided for refrigerants with RCL values and thermodynamic properties. A suggested proposed addendum to Standard 15 and Standard 34 (the refrigerant property tables) is provided.
Product Details
- Published:
- 2013
- Number of Pages:
- 157
- File Size:
- 1 file , 8.5 MB
- Product Code(s):
- D-RP-1448
