Application of jet fans in emergency tunnel ventilation, as an economically attractive alternative to traditional fan plants, has become more popular in the US over the past years. Also, recent literature indicates that transportation tunnels are facing increased fire loads. For example the latest (2008) Edition of the NFPA 502, Standard for Road Tunnels, Bridges, and Other Limited Access Highways, indicates peak Fire Heat-Release Rate (FHRR) of 200-300 MW (683 â 1025 MBtu/hr) for tankers carrying flammable and combustible liquids. This is two to three times the values reported in the 2004 Edition of the same standard. Larger design FHRR increases the need for accuracy in accounting for the heat loads on the emergency ventilation equipment such as jet fans in order to avoid significant over design of these equipment and demonstrate their feasibility. Fortunately, this trend continues to grow parallel to reduced cost of computational power. Therefore, it is inevitable that more sophisticated computational analysis tools are used in the analysis of jet fan performance under fire emergency conditions with large design fire sizes of order 100MW. This paper presents a case study, where the three dimensional CFD analysis is used in conjunction with one dimensional SES analysis in order to establish the jet fan configuration and demonstrate performance/compliance of jet fans for the emergency ventilation requirements of a road tunnel.
Citation: ASHRAE Conference Papers, Las Vegas, NV