Description

Flammability risk can be lowered by controlling the potential for forming a mixture that can reach the lower flammability limit (LFL) by limiting the refrigerant charge in HVACR products that can leak into a confined space. Unfortunately defining the space or room volume is not a straight forward exercise in real life situations. Defining the height of a room can be simple enough, but defining the effective floor area of the room to calculate the room volume can be quite difficult, time consuming and variable depending a large number of factors including obstacles or restricted spaces in the room. Factors to consider are room fill, adjacent spaces, leak release height and natural convection to name a few.

This paper will describe an effective approach to use to calculate the room area. Computational fluid dynamic (CFD) analysis was performed to support the justification for the methodology in this paper. Different approaches will be described for determining the room area for unventilated and ventilated spaces and demonstrate that areas above partition walls, drop ceilings, or ductwork connecting rooms shall not be considered as connecting the adjacent spaces. Natural ventilation as well as forced air circulation will be defined to determine the maximum floor area to consider for calculating the room volume. A majority of the work was conducted to simulate refrigerant leaks from a wall mounted unit at height of 1.8 meters (5.9 feet). A few additional points were run at 0.6 meters (2 feet) to validate the methodology but a detailed analysis was not conducted for these scenarios. Various safety factors will be considered based on the application to determine the maximum refrigerant charge allowed for using ASHRAE Standard 34 Class A2L flammable refrigerants. Maximum refrigerant charges for a large number of ASHRAE 34 classified refrigerants will be summarized for comparison purposes at various LFL endpoints.

Citation: 2017 Annual Conference, Long Beach, CA, Conference Papers

Product Details

Published:

2017

Number of Pages:

8

Units of Measure:

Dual

File Size:

1 file , 1.8 MB

Product Code(s):

D-LB-17-C023