| Appendix 3.7b | Detailed Calculation of In-Tunnel Air Quality | ||||||||||
| for the Full Enclosure at the slip road to Siu Lam Interchange | |||||||||||
| - | Normal speed | ||||||||||
| 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 | ||||||||
| Tunnel traffic | 2240 | 62 | 7 | 31 | |||||||
| Q (veh/hr) | 1390 | 159 | 691 | ||||||||
| Petrol | L.Diesel | H.Diesel | |||||||||
| Emission Factor (g/km) - EURO3 | 0.71 | 1.54 | 6.8 | ||||||||
| Weighted NOX E.F. (g/km/veh) | = | 2.648189 | |||||||||
| NO2 emission factor per unit length (g/m/s), w | = | 0.0003296 | |||||||||
| 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 | ||||||||||
| Traffic density (traffic flow /s), N | = | 0.622222 | |||||||||
| Average vehicle speed (m/s), v | = | 50 km/hr | |||||||||
| = | 13.88889 | ||||||||||
| Head to head distance on a lane (m), l | = | 2*nl*v/N | |||||||||
| = | 44.64286 | ||||||||||
| Diffusion Parameters | |||||||||||
| Reynolds number, Re | = | (v*dv)/s | where s = 15.6*10^-6 | ||||||||
| = | 2327857 | ||||||||||
| According to Figure 16 (Ohashi and Koso) | |||||||||||
| Since | l / dt | = | 4.355818 | ||||||||
| D / (N * dt^2 * Re^0.13) | = | 0.36 | |||||||||
| Longitudinal | |||||||||||
| diffusion coefficient (m2/s) , D | = | 0.36 * (N * dt^2 * Re^0.13) | |||||||||
| = | 158.2402 | ||||||||||
| Maximum Concentration of NO2 | |||||||||||
| Cmax (µg/m3) | = | w * Le^2 / (8 * D * At) | |||||||||
| (without background) | = | 59.65296 | |||||||||