28
1 Fundamental Concepts of Fluid Mechanics for Mine Ventilation
Table 1.2 Coefficients of total permanent losses for some system elements. Note that X 1 and X 2
represent loss coefficients referring to A 1 and A 2, respectively. Modified from Schauenburg Ltd
Element
Angle (θ°) Loss coefficients (X, X 1 , X 2 )
Gradual contraction
X 2
30
0.02
45
0.04
60
0.07
Equal area transformations
X
≤14
0.15
Sharp-edged (flush) entrance
X
–
0.34
Plain (open) entrance
X
–
0.85
Bell-mouth (formed) entrance
X
–
0.03
Gradual expansion
X 1
5
0.17
7
0.22
10
0.28
20
0.45
30
0.59
40
0.73
Sharp-edged discharge
X
1
Fig. 1.14 Static (P s ), total
(P T ) and permanent (P p )
pressure losses in a
sharp-edged entrance
P
P T
P s
P p
Vena
contracta
1 Fundamental Concepts of Fluid Mechanics for Mine Ventilation
Table 1.2 Coefficients of total permanent losses for some system elements. Note that X 1 and X 2
represent loss coefficients referring to A 1 and A 2, respectively. Modified from Schauenburg Ltd
Element
Angle (θ°) Loss coefficients (X, X 1 , X 2 )
Gradual contraction
X 2
30
0.02
45
0.04
60
0.07
Equal area transformations
X
≤14
0.15
Sharp-edged (flush) entrance
X
–
0.34
Plain (open) entrance
X
–
0.85
Bell-mouth (formed) entrance
X
–
0.03
Gradual expansion
X 1
5
0.17
7
0.22
10
0.28
20
0.45
30
0.59
40
0.73
Sharp-edged discharge
X
1
Fig. 1.14 Static (P s ), total
(P T ) and permanent (P p )
pressure losses in a
sharp-edged entrance
P
P T
P s
P p
Vena
contracta