| Appendix 3.7b | Detailed Calculation of In-Tunnel Air Quality | |||||||||
| for the Full Enclosure at the slip road to Siu Lam Interchange | ||||||||||
| - | Worse case | |||||||||
| Tunnel Parameter | ||||||||||
| Tunnel length (m), L | = | 76 | ||||||||
| Tunnel height (m), H | = | 5.5 | ||||||||
| Tunnel width (m), W | = | 15 | ||||||||
| Tunnel size (m2), At | = | H * W | ||||||||
| 82.5 | ||||||||||
| Equivalent diameter (m), dt | = | (4*At/p)^0.5 | ||||||||
| 10.24902 | ||||||||||
| Effective length of the tunnel (m), Le | = | L + 2*3*dt | ||||||||
| 137.4941 | ||||||||||
| Emission Data | ||||||||||
| Traffic Breakdown (%) | ||||||||||
| Traffic flow (veh/hr) | Petrol | L.Diesel | H.Diesel | LGV | HGV | |||||
| Tunnel traffic | 2240 | 62 | 7 | 31 | 0 | 0 | ||||
| Q (veh/hr) | 1390 | 159 | 691 | 0 | 0 | |||||
| Petrol | L.Diesel | H.Diesel | LGV | HGV | ||||||
| Emission Factor (g/km) - EURO3 | 0.71 | 1.54 | 6.8 | 1.23 | 3.84 | |||||
| Weighted NOX E.F. (g/km/veh) | = | 2.648189 | ||||||||
| NO2 emission factor per unit length (g/m/s), w | = | 0.00033 | ||||||||
| Vehicle Data | ||||||||||
| Nominal dimensions of vehicles are given in Transport Planning and Design Manual, Vol. 2 as: | ||||||||||
| W | H | L | ||||||||
| Pertol | 1.7 | 1.5 | 4.6 | |||||||
| L.Diesel | 2.1 | 1.6 | 5.2 | |||||||
| H.Diesel | 2.5 | 4.6 | 16 | |||||||
| HGV | ||||||||||
| Nominal cross-sectional area (m2) | = | (1.7*1.5*(0.62)+(2.5*4.6*0.31)+(2.1*1.6*0.07) | ||||||||
| = | 5.369282 | |||||||||
| Number of lanes per direction, nl | = | 1 | ||||||||
| Equivalent cross-sectional area for each direction (m2), Av | = | 5.369282 | ||||||||
| Equivalent diameter of vehicle (m), dv | = | (4*Av/p)^0.5 | ||||||||
| = | 2.614649 | |||||||||
| Equivalent length of each vehicle (m) | = | (4.6*(0.62))+(5.2*0.07)+(16*0.31) | ||||||||
| = | 8.160357 | |||||||||
| Distance between vehicle (m) | = | 1 | (worst case) | |||||||
| Head to head distance on a lane (m), l | = | 9.160357 | ||||||||
| Traffic density (traffic flow /s), N | = | 0.622222 | ||||||||
| Average vehicle speed (m/s), v | = | l*N/(2*nl) | ||||||||
| = | 2.849889 | |||||||||
| Diffusion Parameters | ||||||||||
| Reynolds number, Re | = | (v*dv)/s | where s = 15.6*10^-6 | |||||||
| = | 477657.6 | |||||||||
| According to Figure 16 (Ohashi and Koso) | ||||||||||
| Since | l / dt | = | 0.893779 | |||||||
| D / (N * dt^2 * Re^0.13) | = | 0.18 | ||||||||
| Longitudinal | ||||||||||
| diffusion coefficient (m2/s) , D | = | 0.18 * (N * dt^2 * Re^0.13) | ||||||||
| = | 64.3973 | |||||||||
| Maximum Concentration of NO2 | ||||||||||
| Cmax (µg/m3) | = | w * Le^2 / (8 * D * At) | ||||||||
| (without background) | = | 146.5822 | ||||||||