Page 78 - Advanced Mine Ventilation

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5
Ventilation Network Analysis

Chapter Outline

5.1 Network Analysis for Air Quantities and Pressure 63
5.1.1 Kirchoff’s First Law 63
5.1.2 Kirchoff’s Second Law 63
5.1.3 Emission Rates 64
5.1.4 Dilution and Distribution Model 64
5.1.4.1 Branch Calculations 64
5.1.4.2 Junction Calculation 66
5.2 Introduction to the Ventilation Network Analyzer 67
5.2.1 Output Results 67
5.2.2 Program Testing on a Hypothetical Case 68
5.3 Veriﬁcation of the Ventilation Network Analyzer in a Working Mine 68
Problems 77
References 77

Air ﬂows in a single airway as well as in several airways in parallel or in series were
discussed earlier. A typical mine is, however, a network of hundreds of airways with
all kinds of combinations. Analytical solutions of simple ventilation networks exist in
literature [1,2]; but for larger networks, computers must be used. Many computer pro-
grams were developed to just calculate the airﬂow and ventilation pressure losses in
coal and metal mines [3,4] in 1970s. Thakur [5] developed an advanced program
that not only calculated the airﬂow and pressure losses in each branch of a ventilation
network but also calculated the steady-state distribution of diesel exhaust pollutants,
such as, carbon monoxide, carbon dioxide, and nitrogen compounds in the network.
It also calculated the air index utilizing the concentrations of gases and their respective
threshold limit values (TLVs).
To illustrate a model problem, a hypothetical mine is illustrated in Fig. 5.1A.
To be able to solve any mine ventilation network mathematically, it must be con-
verted into a linear network and mathematical model in that order. Fig. 5.1B shows a
linear network analogue of the hypothetical mine under discussion.
The main assumptions, in this case, are as follows:
1. Turbulent ﬂow of air in the roadways with a uniform velocity distribution. Consequently, the
gaseous pollutants are assumed to be uniformly mixed across the whole cross section of road-
ways and junctions in the network. Components of diesel exhaust are used in this example.
2. The ﬂow of air and diesel exhaust is steady.

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