5.3 Natural Ventilation
165
Conversely, in the case of Fig. (b), the air column in the small shaft (B
C
), is not
capable of compensating the analogous column in on the deep shaft. Therefore, air
circulates from the long shaft to the short shaft.
5.3.1 Calculation by the Static Method
It is a simplified calculation method. The system in Fig. 5.2, consists of two vertical
P1, T1
P4, T4
P2,T2
P3, T3
Hd, Tmd, Pmd
H u , T mu, P mu
Fig. 5.2 Ventilation scheme for a simplified mine composed of two shafts of equal depth and a
gallery
shafts connected by a horizontal gallery.
The following parameters are defined in it, namely:
• T 1 : Dry-bulb temperature at the inlet of the downcast (K),
• T 2 : Dry-bulb temperature at the bottom of the downcast shaft (K),
• T 3 : Dry-bulb temperature at the bottom of the upcast (K),
• T 4 : Exhaled dry-bulb temperature (K),
• T md : Average dry-bulb temperature in the downcast shaft (K), and
• T mu : Average dry-bulb temperature in the upcast shaft (K).
The pressure of the air column at the bottom of the downcast and upcast shafts (points
2 and 3) is:
P 2 = ρ (1−2) gh d = γ (1−2) h d ; P 3 = ρ (3−4) gh u = γ (3−4) h u
So if P 2 > P 3 , the air flows from 2 to 3.
The Natural Ventilation Pressure (NVP or P n ) must be (Eq. 5.2):
165
Conversely, in the case of Fig. (b), the air column in the small shaft (B
C
), is not
capable of compensating the analogous column in on the deep shaft. Therefore, air
circulates from the long shaft to the short shaft.
5.3.1 Calculation by the Static Method
It is a simplified calculation method. The system in Fig. 5.2, consists of two vertical
P1, T1
P4, T4
P2,T2
P3, T3
Hd, Tmd, Pmd
H u , T mu, P mu
Fig. 5.2 Ventilation scheme for a simplified mine composed of two shafts of equal depth and a
gallery
shafts connected by a horizontal gallery.
The following parameters are defined in it, namely:
• T 1 : Dry-bulb temperature at the inlet of the downcast (K),
• T 2 : Dry-bulb temperature at the bottom of the downcast shaft (K),
• T 3 : Dry-bulb temperature at the bottom of the upcast (K),
• T 4 : Exhaled dry-bulb temperature (K),
• T md : Average dry-bulb temperature in the downcast shaft (K), and
• T mu : Average dry-bulb temperature in the upcast shaft (K).
The pressure of the air column at the bottom of the downcast and upcast shafts (points
2 and 3) is:
P 2 = ρ (1−2) gh d = γ (1−2) h d ; P 3 = ρ (3−4) gh u = γ (3−4) h u
So if P 2 > P 3 , the air flows from 2 to 3.
The Natural Ventilation Pressure (NVP or P n ) must be (Eq. 5.2):