1、15.1CHAPTER 15ENCLOSED VEHICULAR FACILITIESTunnels . 15.1Parking Garages 15.18Automotive Repair Facilities 15.21Bus Garages. 15.22Bus Terminals. 15.24Tollbooths . 15.26Diesel Locomotive Facilities 15.27Equipment 15.33National and International Safety Standards and Guidelines 15.38NCLOSED vehicular f
2、acilities include buildings and infra-Estructure through which vehicles travel, are stored, or are re-paired, and can include vehicles driven by internal combustionengines or electric motors. Ventilation requirements for these fa-cilities are provided for climate and temperature control, contam-inan
3、t level control, and emergency smoke management. Designapproaches for various natural and mechanical ventilation sys-tems are covered in this chapter.The chapter is structured to address general tunnel issues first andthen address the unique aspects of rail and road tunnels, rail stations,bus garage
4、s, bus terminals, and enclosed spaces for equipment main-tenance later in the chapter. Finally, information on applicable ven-tilation equipment is presented.1. TUNNELSTransport tunnels are unique, in that vehicles travel at normalspeeds, possibly carrying cargo (which may be unknown in road tun-nel
5、s), and may include the traveling public (as passengers and/ormotorists) during both normal and emergency operations. A tunnelis a linear-configured facility, as opposed to most buildings, whichare typically more rectangular. This concept is important when con-fronting the need to fight a fire withi
6、n a tunnel. A tunnel cannot becompartmentalized as readily as a building, which means the fire canonly be fought from within the actual fire zone. Limited access andcompartmentation create difficulties with containing and suppress-ing a fire. This combination of circumstances requires unique designa
7、pproaches to both normal and emergency operation.Tunnel Ventilation ConceptsTunnel ventilation must accommodate normal, congested, andemergency conditions. In some cases, temporary ventilation mayalso be necessary.Normal Mode. Normal ventilation is required during normaloperations to control tempera
8、ture, provide comfort, or control levelof pollutants in the facility during normal operations and under nor-mal operating conditions, primarily to protect the health and providecomfort for the patrons and employees.Congested Mode. Congested ventilation is required during serviceperiods where traffic
9、 is slow moving, leading to a reduction or elimi-nation of piston effect. The goals are the same as for normal mode.Emergency Mode. Emergency ventilation is required during anemergency to facilitate safe evacuation and to support firefightingand rescue operations. This is often due to a fire, but it
10、 can be anynonnormal incident that requires unusual control of the environmentin the facility. This includes control of smoke and high temperaturefrom a fire, control of exceedingly high levels of contaminants, and/or control of other abnormal environmental conditions.Temporary Mode. Temporary venti
11、lation is needed during orig-inal construction or while maintenance-related work is carried outin a tunnel, usually during nonoperational hours. The temporaryventilation is typically removed after construction or after the main-tenance work is completed. Ventilation requirements for such tem-porary
12、systems are specified by either state or local mining laws,industrial codes, or the U.S. Occupational Safety and HealthAdministration (OSHA) and are not addressed specifically in thischapter.Tunnel Ventilation SystemsThere are two categories of ventilation systems used in most tun-nels: natural and
13、mechanical.Natural Ventilation. Naturally ventilated facilities rely primar-ily on atmospheric conditions to maintain airflow and provide a sat-isfactory environment in the facility. The chief factor affecting thefacility environment is the pressure differential created by differ-ences in elevation,
14、 ambient air temperature, or wind effects at theboundaries of the facility. Unfortunately, most of these factors arehighly variable with time, and thus the resultant natural ventilation isoften neither reliable nor consistent. If vehicles are moving througha tunnel-type facility, the piston effect c
15、reated by the moving vehi-cles may provide additional natural airflow.Mechanical Ventilation. A tunnel that is long, has a heavy trafficflow, or experiences frequent adverse atmospheric conditionsrequires fan-based mechanical ventilation. Among the alternativesavailable are longitudinal and transver
16、se ventilation.Longitudinal Ventilation. This type of ventilation introduces orremoves air from the tunnel at a limited number of points, primarilycreating longitudinal airflow along its length. Longitudinal ventila-tion can be accomplished either by injection, using central fans,using jet fans moun
17、ted in the facility, or a combination of injectionand extraction at intermediate points.Transverse Ventilation. Transverse ventilation uses both a supplyduct system and an exhaust duct system to uniformly distribute supplyair and collect vitiated air throughout the length of the facility. The sup-pl
18、y and exhaust ducts are served by a series of fixed fans, usually housedin a ventilation building or structure. A variant of this type of ventilationis semitransverse ventilation, which uses either a supply or exhaustduct, not both. The balance of airflow is made up via the tunnel portals.Design App
19、roachGeneral Design Criteria. The air quality and correspondingventilation system airflow requirements in enclosed vehicularspaces are determined primarily by the type and quantity of contam-inants that are generated or introduced into the tunnel and theamount of ventilation needed to limit the high
20、 air temperatures orconcentrations of these contaminants to acceptable levels for thespecific time exposures.Normal and Congested Modes. The maximum allowable concen-trations and levels of exposure for most contaminants are determinedby national governing agencies such as the U.S. EnvironmentalProte
21、ction Agency (EPA), OSHA, and the American Conference ofGovernmental Industrial Hygienists (ACGIH).The contaminant generators can be as varied as gasoline or dieselautomobiles, diesel or compressed natural gas (CNG) buses and trucks,and diesel locomotives. Even heat generated by air conditioning onT
22、he preparation of this chapter is assigned to TC 5.9, Enclosed VehicularFacilities.15.2 2015 ASHRAE HandbookHVAC Applicationselectric trains stopped at stations and the pressure transients generatedby rapid-transit moving trains can be considered contaminants, theeffects of which need to be mitigate
23、d.Emergency Mode. Design provisions may be necessary to man-age smoke and other products of combustion released during fires toallow safe evacuation, to support fire fighting and rescue operations,and to protect the tunnel structure and station infrastructure duringfires (Bendelius 2008).In designin
24、g for fires, the design fire scenario and associated fireheat release rate needs to be quantified. Depending on the level ofanalysis, the generation of smoke and other products of combustionmay also need to be quantified. As a minimum, design for life safetyduring fires must conform to the specific
25、standards or guidelines ofthe National Fire Protection Association (NFPA), where applicable.NFPAs ventilation requirements are for systems to maintain a “ten-able environment along the pathway of egress from the fire.” NFPAStandard 130 defines a tenable environment as “an environment thatpermits sel
26、f-rescue of occupants for a specific period of time”;NFPA Standard 502 includes a similar definition.Other NFPA codes and standards; ICC (2009a, 2009b, 2009c)building, mechanical, and fire codes; and other statutory require-ments may apply. Separation and pressurization requirementsbetween adjacent
27、facilities should also be considered.Temporary. A temporary mode may be necessary during con-struction or other special condition.Technical Approach. The technical approach differs dependingon facility type; however, there are many similarities in the initialstages of the design process.Determining
28、the length, gradient, and cross section for tunnels isan important first step. Establishing the facilitys dynamic clearanceenvelope is of extreme importance, especially for a tunnel, becauseall appurtenances, equipment, ductwork, jet fans, etc., must belocated outside the envelope, and this may even
29、tually determine thetype of ventilation system used.Vehicle speeds, vehicle cross-sectional areas, vehicle design firescenarios, and fuel-carrying capacity are important considerationsfor road tunnels, as are train speeds, train headway, and rail car com-bustibility and design fire scenarios for rap
30、id transit and railroadtunnels.Types of cargo to be allowed through the facility, and their re-spective design fire scenarios, should be investigated to determinethe ventilation rates and the best system for the application. Simi-larly, for railroad tunnels, it should be determined whether passen-ge
31、r or freight or both types of trains will be using the facility and ifthe passenger trains will be powered by diesel/electric power or byelectric traction power.The emergency ventilation approach must be fully coordinatedwith the overall fire protection strategy, the evacuation plan, and theemergenc
32、y response plan, providing a comprehensive overall lifesafety program for the tunnel or station. Egress systems must pro-vide for safe evacuation under a wide range of emergency condi-tions. The emergency response plan must help facilitate evacuationand allow for appropriate response to emergencies.
33、Rail and bus stations are large unique structures designed to allowefficient movement of large populations and to serve occupants thatoften arrive in large groups. Stations can be below ground, aboveground, or at grade. Although each type of station poses specificchallenges, underground facilities t
34、end be the most challenging.Stations can be further complicated by connections to non-transitstructures (Tubbs and Meacham 2007).Rail and road tunnels pose a different set of evacuation chal-lenges. These facilities are long, narrow, and underground, oftenwith limited opportunities for stairwells to
35、 grade. The linear naturelimits initial evacuation, which can pose challenges to the ventila-tion design. Further, the trackway in rail tunnels can be a dangerousenvironment for untrained occupants.The ventilation and other protection systems must support theevacuation plan. NFPA Standards 502 and 1
36、30 provide specific cri-teria for components of the life safety and evacuation systems, butare not universally adopted by authorities. Where road and railinfrastructure interface with buildings, the International BuildingCodeand International Fire Codemay apply. Several documentsare available to pro
37、vide additional guidance on life safety concepts,evacuation strategies, and calculation methodologies (Bendelius2008; Colino and Rosenstein 2006; Fruin 1987; Gwynne andRosenbaum 2008; Proulx 2008; Tubbs and Meacham 2007). Critical Velocity. Manual calculations and resources for theemission and combu
38、stion data are given in the respective sectionsfor each enclosed vehicular facility type. A first step in determiningthe order of magnitude for the ventilation rate required to control themovement of the heat and smoke layer generated by a fire in a tunnelis to apply the critical velocity criterion.
39、 This approach is describedhere, and can be used for all types of tunnel applications.The simultaneous solution of Equations (1) and (2), by iteration,determines the critical velocity (Kennedy et al. 1996), which is theminimum steady-state average bulk velocity of ventilation air mov-ing toward the
40、fire needed to prevent backlayering:VC= K1KG(1)TF= + T (2)whereVC= critical velocity, ft/sTF= average temperature of fire site gases, RK1=0.606KG= grade factor (see Figure 1)g = acceleration caused by gravity, ft/s2H = height of duct or tunnel at fire site, ftq = heat that fire adds directly to air
41、at fire site, Btu/s = average density of approach (upstream) air, lb/ft3cp= specific heat of air, Btu/lbRA = area perpendicular to flow, ft2T = temperature of approach air, RIt is usual to study several alternative ventilation schemes, eachusing different variants and/or combinations of ventilation
42、systems(longitudinal, transverse, etc.). Some types of systems, such as fullytransverse, are almost exclusively used on road tunnels only.When selecting ventilation equipment and the number of fansand types of drives, consideration should be given to efficiency,reliability, and noise. Most of these
43、equipment attributes are re-flected in a life-cycle cost analysis of the alternatives.gHqcpATF-1/3qcpAVC-Fig. 1 Roadway Grade FactorEnclosed Vehicular Facilities 15.3If the effectiveness of the system to provide for fire life-safety con-ditions is not evident from the manual analysis or one-dimensio
44、nalcomputer models such as subway environment simulation (SES), thedesigner should investigate using a computational fluid dynamics(CFD) program to accurately determine the smoke and temperaturedistribution in both the steady-state and transient conditions.Computer Modeling and Simulation. The appli
45、cable NFPAstandards for road tunnels (NFPA Standard 502) and for railroadrapid transit tunnels (NFPA Standard 130) require engineering anal-ysis for tunnels greater than a certain length, to prove that the smokeand heat layer is controlled. Often the best way to show that the re-quirements are met i
46、s by using a CFD program with post-processingcapabilities that feed the results into another program capable of pro-ducing a still picture and/or animated graphical representation of theresults. All the commonly used computer programs and their specificcapabilities are discussed in the following par
47、agraphs.SES. The predominant worldwide tool for analyzing the aero-thermodynamic environment of rapid transit rail tunnels is theSubway Environment Simulation (SES) computer program (DOT1997a). SES is a one-dimensional network model that is used toevaluate longitudinal airflow in tunnels. The model
48、predicts air-flow rates, velocities and temperatures in the subway environmentcaused by train movement or fans, as well as the station coolingloads required to maintain the public areas of the station to prede-termined design conditions throughout the year. This programcontains a fire model that can
49、 simulate longitudinal airflowrequired to overcome backlayering and control smoke movementin a tunnel. Output from the SES can be applied as boundary or ini-tial conditions for three-dimensional CFD modelling of the tunneland station environments. The SES program is in the publicdomain, available from the Volpe National Transportation Sys-tems Center in Cambridge, MA.TUNVEN. This program solves coupled one-dimensional, steady-state tunnel aerodynamic and advection equations. It can predictquasi-steady-state longitudinal air veloci
