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12COMPUTER SIMULATION

The use of computers is having a phenomenal effect on the mining industry. One of the mostexciting trends in computer applications is the explosive development of microcomputers beginningaround the mid–1970s. Today, more microcomputers and desktop computers are around thanterminals.

One reason for this increased popularity of microcomputers is their growing computing powerand decreasing cost. It is now possible to put a mainframe computer – which took up much of anentire floor in the 1960s – on every desktop. Today, microcomputers are commonly equipped with32 to 64 megabytes of RAM (or more), 500 megabytes or even up to several gigabytes of diskstorage, and a sophisticated operating system that permits multiple, simultaneous tasks, andmultiple users when networked.

Using powerful PCs, more and more computer applications in recent years have found theirway into the field of environmental simulation (Edwards and Greuer, 1982; Deliac, 1985; Abbasand Scheck, 1991; Greuer and Laage, 1994), interactive network analysis (Agioutantis and Topuz,1985; Srivastava, et al., 1995; McDaniel and Laage, 1996), monitoring, and centralized control(Firganek, et al., 1975; Tominaga and Umeki, 1991). In ventilation, a small mine with fewworking faces, problems are simple and easily solved by choosing the appropriate fan. In larger,more complex mines the problem of supplying the working faces with fresh air is beyond thescope of "finger in the wind" analysis. In today's climate of stiffer government regulation andmining company's concern for safety, computer programs which analyze ventilation networks arehelping mining companies satisfy their needs.

1 . History of Computer Simulation in Ventilation1

Ventilation network calculations have been performed for several centuries. Due to mathematicaldifficulties caused by diagonal airways, the preferred method had been a trial and error approach inwhich junction and mesh equations were made compatible. Then a large number of methods ofsuccessive approximation were developed. These methods, while surprisingly efficient in oneinstance, can become frustratingly inefficient in another. Atkinson's solution in 1854 for a singlediagonal airway and Cross's method (1936), with its general applicability and simplicity, becamethe two most widely known examples. Some of the methods were based on the linearization of thequadratic resistance equation and used in electric analog computers. Practically all of the methodswere tested for their utility with digital computers when these became available (Laage, et al.,1995).

1 A portion of this section was written by Dr. Rudolf E. Greuer, Professor of Department of Mining Engineering,Michigan Technological University, Houghton, Michigan, with references cited by the author.

Chapter 12 Computer Simulation

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The use of computers to simulate a mine ventilation system dates to the early days of the elec-tric analogue, which derived from the works using fluid flow models. The electric analogue, basedon the similarity between node and mesh equations in ventilation networks with Kirchhoff's lawsof electric networks, was a large set-up. This consisted of several resistors, rheostats, voltagesources, and radio valves and was used to simulate the performance of a ventilation network. Thisanalogue method reportedly was used by Pavlovsky in 1918 to study the seepage of water. Thefirst patent for using electric analog computer for water and gas networks was awarded in 1941 inGermany. This computer used filament bulb resistance to model the second power resistance func-tion in the network calculations. Its first use in mining was reported in Germany in 1952, and in1954 in the U.S. (McElroy, 1954).

In 1951-52, the University of Nottingham (UK) pioneered the idea of combining an electricnetwork simulation of the nodes and mesh equations of ventilation networks with a manualapproximation method for the resistance equation. This led to the design of the commerciallyavailable "National Coal Board Network Analyzer," which found a wide distribution. Home-builtmodels and modifications, using different approximation methods for the resistance equation, wereused in almost all mining countries (Laage, et al., 1995).

An electromechanical analog computer, in which the approximation of the resistance equationwas automatically performed, was first developed in 1950 at a German coal mine and becamecommercially available in 1952. Thirteen of these computers were installed in German coal mines,and a larger number were installed abroad, for mining as well as gas and water companies. In1959, electronic function generators for the simulation of the resistance equation were introducedin Japan; in 1960 the German manufacturer adopted this principle. In 1964, a British modelbecame commercially available and may be the only one still on the market. In 1962, the Frenchbuilt an electronic model which was used for several decades in French coal mines (Laage, et al.,1995).

Although powerful ventilation planning tools, fully-automatic analog computers are singlepurpose machines. All-purpose digital computers became commercially available in the late 1950sand, predictably, replaced the majority of the analog computers. The first network calculations withdigital computers were performed for waterworks in the U.S. in 1957. The first digital ventilationnetwork calculations were reported in Belgium in 1958 and in Germany in 1959. Following thelead of gas and water companies, efforts to replace the expensive analog computers with digitalcomputers began in Germany in 1958. The same coal company which had pioneered the use ofelectromechanical analog computers performed almost all of their network calculations on digitalcomputers by the end of 1959. By the end of 1969, the majority of analog computer users,representing 80% of the German coal production, had switched to digital computers.

From 1961 on, it became customary to include natural ventilation obtained from information ontemperatures and elevations in every mesh. Fan characteristics were treated in different ways asstorage allowed. A FORTRAN version of a type of standard program became a part of the IBMprogram library in 1966; in 1967 it was adopted by the British National Coal Board for ventilationplanning purposes at its divisional computer centers. It has been used for instructional purposes atMichigan Technological University (MTU) since 1967. Although many enhancements and attemptsat improvements were made, it basically is still in its original form and is the core of the MFIREprogram (Greuer and Laage, 1994).

As the availability of digital computers increased, the number of users doing creative work inventilation planning increased tremendously Unfortunately, much of the work went unreportedbecause of personal, societal, or company constraints. Some of the work that was reported


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included: an advanced program capable of performing high speed calculations for large networks inuse in France in 1961; a storage saving program based on the Cross method of flow rate balancingintroduced in 1967; network calculations with digital computers started in 1961 in Japan;convergence-improving mesh assemblies reported in 1969; in Russia, attempts with digitalcomputers made in 1963; in 1965 and 1967, reports on different approximation methods; in GreatBritain, the first network calculations with the meshes assembled manually reported in 1964; aprogram with automatic mesh assembly described in 1965; and in the United States, the firstprogram to prove the usefulness of digital computers described in 1963 and an improved versionallowing the inclusion of fan characteristics reported in 1964. Both these programs still requiredthe manual assembly of meshes. Some of the other earlier papers in this area include those byHartman and Trafton, 1963; Wang and Hartman 1967; Wang and Saperstein, 1970; Stefanko andRamani, 1972 and 1973; Barnes, 1975; McPherson 1974 and 1976; Hall, Unsted and Lintott,1976; and Tien in 1976. Many other papers have been written since then and can be referred to atthe end of this chapter.

As of today, the three most commonly encountered network calculation programs in the U.S.are (1) The Michigan Tech. Program, originally developed in Germany in the 1950s. (Afterrevision and addition by R.E. Greuer and X.T. Chang in the 70s and 80s, this became known asthe MFIRE, Version 2.2 program.); (2) The Penn. State Simulator, originally developed by Y.J.Wang in the late 1960s, and widely used in the field; And (3) M.J. McPherson, originally from theUnited Kingdom, wrote a simulation program in the mid to late 1960s, later turning it intoVNETPC. The latest version of this is the VNETPC for Windows, Version 1.0. Other programsalso were developed in Japan, the former U.S.S.R., France, and South Africa. By 1970, severalof these models were available.

Over the past two decades efforts focused on: (1) replacing the Cross method with more effi-cient approximation methods; (2) combining network calculation for optimization purposes withoperations research approaches; (3) making the programs more user friendly, in particular by usinginteractive graphics; (4) combining network calculations with temperature and concentration calcu-lations; and (5) extending network calculations to transient state conditions. The first objective hasbeen a continual goal since the first days of digital computer use. So far, all results seem to confirmthat the Cross method for networks of ordinary size and complexity is as good or better than othermethods. The second objective is a very valid one since network calculations are only a means toan end. The third objective is probably the most important one.

Efforts to combine ventilation network calculations with the precalculation of temperatures andhumidities started in Japan in 1969. An early program which included temperatures, humidity,methane and dust concentrations, plus a transient state methane simulator, originated at theUniversity of Pittsburgh in 1972. In 1975, at the First International Mine Ventilation Congress, re-ports were seen on four programs from the U.S. and Great Britain for a combined network,temperature and humidity calculations. At the Third Congress in 1984, a program for temperature,humidity, and radon concentrations was introduced from Australia.

Litigation connected with the Sunshine mine fire in the mid-1970s showed that existing pro-grams could only partially simulate the interaction of mine fires and ventilation systems. Althoughmanual non-steady-state temperature precalculations had become a common feature, and steady-state fume concentrations were easy to add as long as no recirculation occurred, manual insertionsof thermal draft and throttling effects proved to be cumbersome, and the handling of recirculationto be impossible (Greuer, 1977 & 1979).

This led to the development of a new program at MTU in 1975 and 1976. The goals of this


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program were to determine the equilibrium between fires and ventilation systems in steady-stateconditions at any given time. The crucial heat exchange between rock and air was calculated undernon-steady-state conditions. The program was based on mass flow rates and considered naturalventilation in all meshes and throttling effects in all airways. Airflow reversal and fume recircula-tion also were calculated. This program, sometimes referred to as the MTU/BOM code, was thefirst building block of MFIRE (Greuer and Laage, 1994).

2 . Principles of Network Simulation

Currently, there are well established models for ventilation network simulation, as well as for thestudy of other parameters in mine ventilation. They enable the ventilation engineer to simulateseveral system alternatives and select the most efficient and cost effective ventilation system. Allthese programs are based on the Hardy Cross iteration method, which basically is a series ofsuccessive approximations based upon two Kirchhoff's laws for electrical circuits and theAtkinson's Equation (Cross, 1936). These laws state that continuity of flow must hold at junctions(conservation of mass), that total change in pressure in a closed circuit must be zero (continuity ofpotential), and that airflow follows the relationship of head loss equals resistance times thatquantity squared, H = RQ2 (Atkinson's Equation). Recent developments in micro- and mini-computers have further facilitated input/output, real time simulation (Pomroy and Laage, 1988;McDaniel and Wallace, 1997), user interaction, and user-friendliness (Greuer and Laage, 1994;Hartcastle, et al., 1997). They have enabled ventilation engineers to further extend their applicationinto evaluation of underground refrigeration, environmental simulation, and others.

Ventilation problems that can be solved by the computer program include:

❏ solving complex ventilation systems with many entries, shafts, fans, and working faces;❏ fan selection;❏ determining optimal fan settings for efficient operation;❏ determining the amount of regulation required to control airflow;❏ determining the effect of air leakage on the overall system;❏ selecting optimal fan locations; and,❏ determining possible effects of improvements to airways, such as cleaning rock falls,

smoothing airways, and other means of decreasing airway resistance.

Progress in the development of hardware and software will continue apace. There will befurther improvements in the computing abilities (speed and memory capacity) of personalcomputers and the power of today's supercomputers will be available in the office machines oftomorrow. One of the most significant recent advances has been the advent of the parallelprocessor computer. The current generation of machines utilizes a single microchip processorthrough which passes all of the calculations in sequence; the binary data being transferred from andto memory as directed by the program. Even with the enhanced speed of modern computer chips,the single processor has become a bottleneck. The computing time for one iteration of the completenetwork is the time taken for every mesh (a closed loop formed by several airways in the network)to pass through the processor, one after the other. The corresponding time on a parallel processorwill be reduced to that required for one iteration on the largest mesh only. For example, on currentpersonal computers, a 500-branch (airway) network typically may take several minutes to analyze.On a parallel processor this will be reduced to a few seconds. (McPherson, 1988).

The next generation of network programs will provide powerful optimization features. In addi-tion to giving distributions of airflow, pressure drops, airpower losses, etc., such programs will


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give direct advice on the duties and locations of fans and regulators, and the recommended sizes ofproposed new arterial airways. Embryotic but practical versions of this type of application forselecting the optimum combination of fans and regulators are already at the testing stage.

While ventilation network analysis programs, and variations on them, have dominated softwaredevelopment and application, other programs also continue to be produced. These increasingly willenable ventilation engineers to conduct sophisticated analysis, including shaft design (Rose andBluhm, 1992; Greyvenstein, et al., 1992), gas drainage system analysis (Zuber, 1997), and airconditioning configurations (Partyka and Koxzkodaj, 1987; Rose and Bluhm, 1992; Marks,1994). All these will help in working toward the ultimate goal – ventilation automation.

3 . Post Survey Calculations

Computer analysis of an existing ventilation system requires accurate input data which are devel-oped only by detailed ventilation pressure air quantity surveys. For new mine projections, the rec-ommended practice is to use friction values obtained from operating mines in the same area undersimilar conditions so that pressure loss calculations are representative.

1) Air Quantity –

Air quantity is obtained by multiplying corrected air velocity (by using calibration chart) andcross-sectional area (after subtracting body area).

2) Air Pressure –

Air in any section of an airway possesses energy by virtue of the static pressure under which itexists, its elevation above certain datum level of potential energy, and additional velocity energy ifit is in motion (Equation 4-1, HT = Hs + Hv + Hz ). By carefully choosing measuring locationswhere air velocity is less than 400 fpm, the effect of air velocity can be ignored (§3.6: Air PressureMeasurement). For temperatures of 70°F or less, air density corrections can be neglected withoutsignificantly affecting final outcome, since the difference between dry and saturated air densityunder such temperatures is less than 1%. The remaining pressure would be the combination ofstatic pressure and potential pressure (§3.6: Air Pressure Measurement).

There is another critical element in pressure reading: the effect of surface barometric pressure.The effect of barometric pressure fluctuations on underground pressure systems is instant andsignificant (McIntosh, 1957; Stevenson and Kingery, 1966; Bruzewski and Aughenbaugh, 1977;Anon., 1988; Neethling, 1989). It has been reported that a powerful thunderstorm has beencapable of causing a short term rate of change as high as 0.018 in. Hg per hour (Francart andBeiter, 1997). To determine true ventilation pressure, this element must be corrected.

Figure 12-1 shows a close correlation between the pressure fluctuation underground andbarometric change in one year (Kennedy, 1989).


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30

25

20

15

10

5

0

– 5

Time (1,000 hours)

0 2 4 6 8

Baormeter

Underground

Figure 12-1. Correlation between pressure fluctuation underground andbarometric change in a period of one year.

Many forms are available for recording pressure survey data. A simplified pressure recordingform is shown in Figure 12-2.

Barometric Change Correction (ft)

Base Rdg.Base Change (3) - (3)s

Station Time

Surface

Elev.

Instrument Reading (ft)

Instrument Change (ft) (1) - (1)s

Elevation Change Correction (ft)

Ventilating Pressure

Change(5) - (5)s

1s 3s 5s

In. W.G.(7)x( -0 .014)

Air Col, ft(2) - (4) - (6)

1 2 3 4 5 6 7 8

Figure 12-2. A Simplified sample pressure survey form.


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3) Constructing schematics

A schematic is a simplified line diagram of the mine. A ventilation network can be viewed as a bigplumbing system. The main intakes and exhausts are plotted first, followed by the horizontalconnections between the two and, finally, by the raises and ramps between the horizontal levels.Junctions are established wherever two or more branches connect. All branches must have ajunction in and out, and each junction must have at least two connecting branches. After thenetwork is plumbed together, the fans and regulators are placed in their respective positions.Constructing the network for an existing mine is fairly easy and straightforward.

Any complex circuit can be reduced to one or more branches between the surface and the fan,but avoid over-simplification. Any branch in the mine network can consist of one or more non-isolated entries and still be represented as a single line on the schematic, as shown in a four-unitcoal mine in Fig 12-3.

Neutral Airflow Unit-1

Unit-2

Unit-3

Unit-4

Slope IntakeAirshaft

Mine Fan

Intake Airflow

Return Airflow

Figure 12-3. Schematic showing a four-unit coal mine.

Network construction for a new mine is undertaken after completion of the mining plan and theinitial ventilation planning. By this time, the airflow requirements have been specified and layout ofthe shafts and levels completed. The network is then put together in much the same manner as withan existing mine. Since fans and regulators do not yet exist, these are placed at "best guess"locations initially, and then checked by subsequent simulations. The designer must keep in mindany possible future expansions. The network for a new mine tends to have fewer branches than thenetwork for an existing mine.

Selecting the optimum number of branches may be the most delicate part of constructing a net-work. Too few will not simulate the mine properly and too many will prove cumbersome.Accuracy is not necessarily a function of the number of branches. Some rules-of-thumb for normalbranch selection are as follows (Marks and Deen, 1993):

❏ The total number of branches must be smaller than the number allowed by the program.Enough capacity should be left for running simulations. If more branches are desired, some ofthe airways might have to be combined, or the dimension arrays within the program modified.If the designer does not have access to the computer code, the program supplier should be


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approached for a custom version.

❏ An individual branch should be input if it carries ≥ 1% of the total mine airflow. For example,if a mine is ventilated by 1,000,000 cfm, branches containing more than 10,000 cfm should beinput. Branches with less airflow can be grouped into series/parallel sets.

❏ It is sometimes best to split single, long, vertical branches of more than 2,000 feet into two ormore branches for more accurate thermodynamics and psychrometrics; specifically, to assist inresistance or natural ventilation pressure (NVP) calculations. Density changes are non-linearwith depth, and heat transfer and evaporation/condensation are functions of site-specificconditions.

❏ Individual branches are often placed where a special process is taking place, such as a signifi-cant heat addition, air-conditioning process, or gas inflow. Fans are often located in their ownbranches. Special branches are used on the tops of exhausts to dissipate heat to atmosphere andto assist in natural ventilation pressure calculations. Special branches also can account for hard-to-measure leakage, and can be placed to check the effects of circuit changes on neutral points.

❏ Additional branches may be placed in areas of intense activity, or to set up or aid future simula-tions.

Junctions are then systematically numbered by one to several digit numbers, with the surface acommon number. In addition, maximum flexibility also should be given for updating the schematicas the ventilation layout or conditions change since each segment of the ventilation system caneasily be identified. The final schematic usually is a trade-off between simplified computer inputand requirements for a user oriented output. Most importantly, the network is left as closely aspossible in the form of the line diagram to maintain a resolution of the various airways. Evaluationof the quantity flow in any branch in the system is then simply a matter of checking the computeroutput.

The air quantities and pressure readings calculated previously now are transferred to theschematic for resistance calculations. Different colors usually are used to differentiate between thetwo readings.

4) Resistance Calculations

Once the air quantity and pressure information are transferred on a schematic map, the resistancefor each airway branch in the schematic can be calculated using R = H/Q 2, where H is the pressurein inches of W.G. and Q is the quantity in 10,000 cfm (for instance, Q = 0.65 means Q = 65,000cfm; see §4.6). Figure 12-4 is a suggested form for such a purpose.

Branch Length No. of Starting, Ending, Ave Q, Gain/ R K in ft. Entries Q, cfm Q, cfm in cfm losses factor

Figure 12-4. Table used to calculate mine resistance and K values.


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Keep in mind that altimeters could easily be misread up to 2-ft and errors in elevation canaccount for an additional 5-ft or more, plus the base altimeter error. Therefore, pressure valuescould be off as much as 0.1 in. W.G. Pressure readings which are completely out of character fora given location in the mine usually are disregarded entirely, and other readings are averaged toprovide a replacement.

Also, the quantity of air coming into a mine based on field measurement will rarely equal thequantity exiting the mine, even if allowances are made for methane or compressed air input to thesystem. The reason for the apparent discrepancies is the accuracy of the indicated quantities, whichin turn are based on the accuracy of the individual velocity and area measurements. Even with mea-surements following the guidelines described in the previous section on quantity measurement, thisdiscrepancy can be minimized, but not eliminated. As a result, the ventilation system must bebalanced carefully so that it will satisfy the law of flow continuity: the quantity in equals thequantity out. Realizing also that pressure readings were possibly taken on different days, minoradjustments derived from the common point readings should be applied.

5) Simulation Input

Simulation input is prepared using field measurements, complemented by mine records, refer-ences, and measured or manufacturer's data on fan curves. Depending on the particular programused, input format could vary, but the basic features usually required in the simulation are branchdata, fan data, junction data, and/or special data.

Branch Data

Depending on the program used and the options desired, branch data can include the type (normal,fixed quantity, fan, airflow inject or reject, dummy, atmospheric), the junction connections in andout (starting and ending), calculated resistance (friction and/or shock losses), or values generatedby the program based on the airway's physical characteristics (length, shape, K-factor), andwhether or not natural ventilation pressures are present. Of these variables, the resistance is themost critical.

The resistance at actual density, R , must be input. For most programs, the actual resistance istaken directly from field measurements or it is derived from knowing the resistance at standarddensity, Rs , and the average branch density. The usual method for obtaining Rs is to look up a K-factor at standard density in references such as McElroy. K-factors should, however, be derivedfrom actual measurements from similar openings whenever possible. McElroy's K-factors,measured in the 1920s and 30s, have been found to be slightly high when compared to today'smines, mainly due to the smaller airways used at the time since the K-factor is not merely afunction of airway roughness but also of the ratio of airway roughness to the diameter of theopening. The actual resistance can be calculated after obtaining resistance values at standard airdensity (either calculated using Equation 4-10 or directly from field measurement):

R = Rs w

0.075 (12-1)

where w = average density, w i +we

2 , lb/ft3.

In VNETPC, using imperial units, the branch pressure drop is reported in milli-inches of water


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and the quantity in kcfm (cfm/1,000). Resistance therefore must follow suit. Resistance is input in"practical units", (milli-inches water per kcfm2). The 10-10 exponent is avoided.

To convert resistance units from regular Atkinson's units, Rs, to practical units, RPU:

RPU = (0.1)(Rs x 1010) (12-2)

As an example, a drift has a resistance value of 2 x 1010 in.min2/ft6. The resistance in practicalunits would be 0.2 milli-inches water per kcfm2.

The Michigan Tech program works on a mass flow basis, and reports the output quantity ascfm at a reference density. Three densities and three resistance therefore are involved:

ws = standard density, 0.075 lb/ft3;w = actual density;wR = reference density;Rs = resistance at standard density;R = resistance at actual density; andRR = resistance at reference density.

The resistance input to the computer is the reference density, and this is calculated as:

RR = Rs wR

3

0.075w 2 (12-3)

Computer runs also are used for existing mines to derive the equivalent resistance of a complexset of individual branches in series/parallel combination. This must be done before the network isready to be used for ventilation planning because existing mines may contain thousands ofindividual airways and it would be far too cumbersome to include all of them in a computernetwork. When a set of series/parallel branches is to be replaced by a single equivalent branch, thenetwork should be run and the resistance assigned to the equivalent branch modified until thesimulated branch airflow matches the actual measured airflow. The network then can be used innormal manner, as long as changes within the set of series/parallel branches are not undertaken.

Junction Data

This includes elevations and, in some programs, air state point data (temperatures and densities).Junction data are usually required only in programs that calculate NVP internally.

Fan Data

For each fan, there should be a fan identification number, branch location (where the fan islocated), and information on the fan curve (number of points, method of curve-fitting, and thepressure-quantity relationship). The user's manual of each program contains details on how toinput fan curves. For most cases, ten points are recommended for each curve since, the more thepoints, the more accurately the program can re-create the curve.


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All fan curves provided by fan manufacturing companies are plotted based on standard airdensity (0.075 lb/ft3). If fans are used at locations that do not have standard density, fan curvesmust be adjusted accordingly. For the pressure-quantity relationship, the abscissa (quantity) is leftconstant and the pressure is adjusted by:

P = Ps w

0.075 (12-4)

If special simulations, such as fire modeling, are planned, fan curve input should extend intothe second and fourth quadrants.

Special Data

This category of input is reserved for "real time" analyses. These simulate the spread of gas con-centrations from sources such as a methane inflow or from a fire and the heat transfer between airand wallrock. The changing NVP effects caused by a fire on a ventilation system can be simulated.Besides checking system response to an unplanned event, these programs can help in specifyingthe locations of fire detection sensors, although much of this work is still in the validation stage(Greuer and Laage, 1994).

4 . To Start A Simulation

Once the network has been constructed and the data input, the network is ready to run. Because ofthe complexity of the ventilation network (for example, because every single stopping is a potentialsource for air leakage, resulting in another "airway" in parallel) a considerable number ofundefined airways are to be expected. Consequently, there is always the possibility of either over-or under-estimating the airway resistance values. Resistance modifications are thus necessary todetermine actual representative values before actual planning. Often, the line between this dataadjustment or resistance balancing and full use is hazy. A network usually is a continually-evolving tool and must be updated regularly.

Field Data Adjustment

The logical way to correct this is to plug in the measured data and adjust the resistance figure bycomparing the airflow distribution results with the actual field measurements. The user must ac-quire confidence in the program before specifying fans or calling for new airways. The procedureis demonstrated as follows:

First Computer Printout:

Airway R Airflow H, in. W.G.200 0.018 508,000 0.465201 0.093 103,000 0.099202 0.002 765,000 0.117203 0.041 453,000 0.841

Field Measurements

Airway Airflow200 483,000


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201 195,000202 613,000203 391,000

R Values Are Then Changed to:

Airway Formula Used Calculations New R

200 R = H

Actual Q2 0.465/(4.83)2 0.020

201 0.099/(1.95)2 0.026202 0.117/(6.13)2 0.003203 0.841/(3.91)2 0.055

Second Computer Printouts with New R Values:


R Values Are Then Changed to:

Airway Formula Used Calculations New R

200 R = H

Actual Q2 0.490/(4.83)2 0.021

201 0.056/(1.95)2 0.015202 0.151/(6.13)2 0.003203 0.581/(3.91)2 0.038

Third Computer Printout with New R. Values


These modifications should be repeated until airflow falls into a reasonably close range to theairflow measured in the field. With an existing mine, the airflow predicted by the computer shouldcome within 10% of the actual flows measured in the mine before the program is used for ventila-tion planning (Gaines, 1978). For major branches, even better accuracy is desired. A convenientexpression for checking the balance of a network program is (Marks and Deen, 1993):


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If |S(QPRED – Q ACT)SQACT

| ≤ 0.10, then the network is balanced well enough.

where QPRED = the computer-predicted quantity flowing in a branch.QACT = actual measured quantity in a branch.

Branch resistance are adjusted to help attain balance. If the branch resistance in question wereactually measured with good confidence underground, they should not be changed without a verycompelling reason. They should be re-measured. Frequently, a problem with balancing involvesthe regulators in the circuit. The resistance of regulators should be measured with the gage andtube. If not, a number of computer runs might be necessary to converge on the actual resistance.

Even when airflows balance well, the indicated fan pressure may not. The balancing period fora new network often involves trouble at the fan sites. Usually, fixed-quantity branches in the fanlocations are used during this time, with the fan curves inputted later. If, for example, the airflowsbalance well, but the fixed-quantity pressures are low, certain branch resistances might be too low.A more common occurrence is when fixed quantity pressures are too high. This might imply thatcertain branch resistances are too high. Perhaps the NVPs haven't been calculated properly.Perhaps a couple of parallel branches were forgotten. Unaccounted for leakage can disrupt anetwork during the airway resistance adjusting period (Marks and Deen, 1993).

Typically, a freshly-constructed network contains more branches than necessary. This is a le-gitimate step in the evolution of a network that should not be bypassed. During or after the break-inperiod, the number of branches can be reduced through the use of "equivalent" branches.However, too many equivalent branches tend to reduce the resolution of the network.

5 . Use of the Program for Planning

Computer network simulation provides two things: how the airflows are distributed throughout thenetwork and how much pressure it takes to do the job. Results from a computer run can revealwhere resistance bottlenecks are located and which branches might be subject to unacceptably highair velocities. These revelations, in turn, indicate how fans should be sized, and where regulators,parallel airways, or section boosters might be placed (Tien, 1976; Marks and Deen, 1993).

Just as the name implies, it is only a simulation. The program simulates, based on the inputprovided, what the airflow and pressure distribution likely would be in the network. A mediumsize network containing, say, 800 branches will not be able to simulate with a high degree of con-fidence what a small rise in one of the mining sections actually will do. This is especially true whena good percentage of the network branches are "equivalent" branches, or single branchescomposed of a set of individual branches in series/parallel combinations. The larger the proposedchange, the more accurate the projection (Marks and Deen, 1993). The potential effects of smallchanges are often best evaluated by means other than computer simulation. The computer is a won-derful tool for simulating "what if" scenarios based on the same set of data. Interpretation is just asimportant as the actual running of the simulation. The computer is merely a tool that tests thedifferent hypotheses of the ventilation planner. The human is still responsible for the thinkingcomponent of ventilation planning.

Assuming that all the bugs have been eradicated, computer-projected airflow balanced well


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with actual measurements, and computer-projected operating points of all circuit fans closely ap-proximating measured operating points, the network is ready for mine ventilation planning. It wasstated earlier that the main purpose of network analysis is to test the hypotheses of the designer. Alist of possible modeling jobs includes:

❏ New mines;❏ New airways in existing mines;❏ Stripping old airways to a larger cross-section;❏ Closing off old airways;❏ Paralleling existing airways;❏ New fans, or new fan positions;❏ Fan blade changes or speed changes;❏ Removing existing fans;❏ Expanding primary circuits;❏ Downsizing primary circuits;❏ Connecting with other mines or primary circuits;❏ Testing the effects of heat loads or air conditioning on NVP;❏ Projecting the spread of contaminants;❏ Conducting fire preplanning exercises;❏ Determining the best locations for fire detection sensors;❏ Playing "what-if" (shafts cave in, fires, etc.); and❏ Conducting sensitivity studies.


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EMPIRICAL RESISTANCE VALUESAppendix 12-1

1) Resistance Values Developed by MSHA

The following table was calculated from field data by Denver Health and Safety TechnologyCenter, Ventilation Division, MSHA.2 Most of the data were obtained during routine pressuresurveys in numerous coal mines over a period of 15 years.

Table 12-1 Resistance Values for Underground Coal Mines.

Type of Airway or Resistance Values,Ventilation Structure in. W.G. min2/ft6

Intake entry, 100 ft. 0.0189Return entry, 100 ft 0.0284Belt entry, 100 ft 0.0568Main fan discharge stack1/ 0.01 to 0.20Leakage path-intake side of main fan 6 to 1.078Single masonry stopping 2/ 5x103 to 7x106

Single seal 10,000+Leakage path-multiple stoppings 8 to 650Single overcast 0.007 to 0.150Longwall face, 100 ft. 0.0380 to 1.3240

1/ For 72-in and larger diameter fans equipped with stacks specified by the manufac-turer.

2/ For 7-ft high by 20-ft wide masonry stopping in good condition with no visible oraudible leakage paths.

The following summary further described MSHA's findings:

a) Resistance for Intakes, Returns, and Belt Entries❏ The friction factors found by experience to be the most useful are from the McElroy table

for straight airways excavated in sediments (or coal). A K value of 50 is a good average forintake entries and a value of 75 for return entries, which typically are more obstructed thanintake entries.

❏ A limited amount of MSHA data available on air-carrying belt entries showed a wide rangeof variation in K factors, from 75 to 275, with K = 150 being the average.

b) Resistance for Mine Fans❏ The discharge duct of a main fan used in the U.S. often is only 90 to 95% efficient in

reducing the air velocity (the fans typically will expand 12 in. for every 80-in length, or an

2 Values are extracted from the paper presented by W. Bruce and T. Koenning at the 3rd U.S. Mine VentilationSymposium, Penn. State University, Oct., 1987.


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angle of 4.29°). It constitutes a significant resistance which needs to be accounted for inmost ventilation systems.

❏ If the fan has no discharge duct, a duct other than specified for the fan, or if the fan diame-ter is smaller than 72 in., then the duct resistance must be computed from the velocity at themouth, taking into account the inefficiency of the duct.

Example 12-1: Calculate the resistance for a 60-in diameter fan equipped with a 160-in long ductwith an 84-in diameter at the mouth of the duct, and having 150,000 cfm of air passing throughthe duct.

Solution: To convert inches to feet, 84-in/12 = 7-ft

Duct area at mouth =( 72 )2

x π = ( 3.5 )2 x 3.1416 = 38.48 ft 2

Velocity at duct mouth = 15000038.48 = 3,898 fpm

or = 4,103 fpm at 95% efficiency

Pressure loss in duct, H = ( 41034009 )2

= 1.047 in. W.G.

Resistance, R = H

Q 2 = 1.0471.52 = 0.465

Which is outside the range shown in the table.

c) Resistance to Simulate Mine Fan Leakage❏ For an exhausting main fan, it is quite common to have substantial air leakage from the at-

mosphere into the return air stream in the vicinity of the intake ductwork and the connectionto the return air entry. Such leakage should always be accounted for in computer simula-tion.

❏ The air leakage can be determined from the difference between the air quantity measured(using a pitot tube) within the fan and the air quantity measured just inside the mine. Once

the leakage is quantified, resistance values R can be calculated using R = H

Q 2

d) Resistance for Masonry Stoppings❏ Values listed in the table are for individual masonry stoppings in good condition. If the

stoppings have experienced some deformation, the individual stopping resistance may be aslow as 1,000.

❏ Single seals will have a resistance value equivalent to the most resistive stoppings.❏ Less substantial stoppings, or stoppings constructed of brattice cloth, may have resistance

values in the range of 10 to 1,000.

e) Resistance for Multiple Stoppings❏ For simplicity, resistance values for stoppings while simulating are best grouped together

and represented by one single resistance path. The values given in the table usuallyrepresent 10 to 20 stoppings.

f) Resistance for Overcast❏ Resistance values for a single overcast in the table. It is the average of 18 overcast values

ranging from 0.007 to 0.15, or 0.033.


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g) Resistance for Longwall Face❏ Figures given in the table represent an average of nine operating longwall faces ranging

from 0.19 to 6.62, with the average being 2.97. The coal seams in the nine mines variedfrom about 48-in to 8-ft in height.

❏ The resistances in the table account for only the face resistance.3

2) R-values for Illinois and Ohio

Resistance values usually are expressed in per 1,000 feet. The following two sets of resistances arefor two room-and-pillar operations, one located in Illinois and the other in Ohio.

Mine X (Illinois)

Intake Airways:5 entries – 0.0184 entries – 0.0283 entries – 0.0502 entries – 0.1771 entry – 0.708

Return Airways:5 entries – 0.0044 entries – 0.0073 entries – 0.0832 entries – 0.1871 entry – 0.748

Neutral Airways:Main entries – 0.141Submain entries – 2.716Panel entries – 6.368

Mine Y (Ohio)

MainsIntake Airways (2-entries) – 0.256Return Airways (2-entries) – 0.283Neutral Airways (2-entries) – 0.144

Submains -Intake Airways (2-entries) – 0.807Return Airways (2-entries) – 0.932

Panels -Neutral Airways (2 entries) – 6.006

Single Set of Overcast (2 in a row - regular type with 5-ft x 12-ft opening)Resistance – 0.326

3 Based on theoretical analysis and empirical data, it appears to have a significant amount of resistance present justupstream from the intake end of the longwall face and also downstream from the return end.


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3) R-Values for Longwall Mining in Colorado

The following longwall face resistance values and K-factors are based on a study of a Coloradocoal mine having a 483-ft longwall face (divided into nine sections):

Table 12-2: Resistance on the Longwall Face

Sec. no. Length, ft R R/ft Remarks1 70 0.735 0.0105 Stageloader & Electricals2 58 2.035 0.0351 Maingate end of face3 58 0.664 0.01144 58 0.598 0.01035 58 0.410 0.00716 58 0.414 0.00717 20 0.221 0.0111 Face widens8 45 0.665 0.0148 Shearer9 58 2.356 0.0406 Tailgate

The above values are summarized as follows:

Table 12-3: Summary of Longwall Face Resistance

Stage Loader/Electricals 0.735Face Ends & Tailgate 4.391Face Line 2.972

Calculated friction factors are tabulated as follows:

Table 12-4: Friction Factors

Sec. no. R K-factors3 0.664 1874 0.598 2745 0.410 2126 0.414 347

The above values for a mechanized longwall face can be summarized as:

Table 12-5: K-factors

Condition K-factorGood 200Normal 275Rough 350


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4) K Factor for Longwall System in Illinois

In a study of longwall operations in the Illinois Basin (Jain and Mutmansky, 1987), the followingvalues were suggested

K factors:Intake airways: 60 x 10-10

Return airways: 80 x 10-10

Concrete-lined airshafts: 25 x 10-10

Concrete airshafts with buntons: 93,000,000 x 10-10

Stopping Leakage Factors (typical conditions measured in the field):❏ For less than two-year old stoppings: 250 cfm/100 ft2/1 in. W.G. (or 20 x 10-3 m3/s per

m2 of stopping area per kPa of pressure difference across the stoppings).❏ For more than two-year old stoppings: 500 cfm/100 ft2/1 in. W.G. (or 40 x 10-3 m3/s

per m2 of stopping area per kPa of pressure difference across the stoppings).❏ The exponent of the leakage4 calculation was assumed at a value of 1.43 for the stop-

pings.

Resistance Value for Longwall Gobs:❏ A suggested rule-of-thumb is: 10 x 10-10 in. W.G./(cfm)2/100 ft of gob measured

along the diagonal.❏ The leakage exponent is assumed to be 1.01 .

4 Experiments showed that stopping leakage increased with the pressure differential across the stopping accordingto the following relationship:

Q = a P n

where Q is air leakage per 100 sq ft stopping, in cfm;P is pressure differential, in inch water gage;a is air leakage at a 1-in. pressure differential, cfm; andn is the exponent which varied from 0.3 to 1.2, depending on the material which the air is leaking.


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CALCULATING RESISTANCE VALUESAppendix 12-2

1) Estimating Longwall Face Resistance

a) Determine the length, L, mean cross-sectional area, A, and perimeter, O, of the face andestimate K-factor from Table 14-4. Then determine face resistance values, Rf using equa-tion:

Rf = KOL

5.2A 3

b) For each face-end, determine the following shock loss factors where applicable.

Sharp right angled bend: X b = 1.4Sudden contraction at inlet end: X c = 0.184

Face-end Obstruction: X ob = [ A0.7(A –a ) – 1]

2

where A is the cross-sectional area of face and a is the cross-section of obstruction fac-ing the airflow.

Note: For the majority of longwall faces in the US, the height of the face is the same asthat of the airways. No allowance need be made for an expansion loss at the returnend unless there is a concentration of equipment at this location.

c) Use a shock loss factor of X shear = 4 for each shearer on the face.

d) Sum all shock loss factors to give X Total

e) Determine the equivalent resistance of the shock losses:

Rx = (6.211)(X Total )

A 2

f) Determine total resistance values for face:

R = Rf + Rx

g) The resistance of the main gate and tail gate should be determined separately, also from:

Rf = KOL

5.2A 3

using values of friction factor, K, appropriate to the conditions expected, and taking intoaccount the location of equipment close to the face.


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Having determined the full face resistance, including those adjoining lengths of mainand tail gates that contain equipment, the resistance may then be used in network simulationfor ventilation planning purposes.

2. Stopping Line Leakage

For quick estimation purposes, the following figures for stopping leakage can be used:

❏ 3,000 cfm per 1,000 feet in main entries having 2 to 4 in. W.G. pressure differential acrossstopping line;

❏ 1,500 cfm per 1,000 feet in submains having 1 in. W.G. pressure differential across thestopping line.

3. Vent Pipe Resistance

In metal and non-metal mines, ventilation tubings are usually used at the mining face to assist faceventilation. In the case of coal mining, vent tubing in and around the face area is not very common,probably due to space limitations. But it is quite common to use ventilation tubing during the slopesinking stage before the permanent ventilation circuit is established. Depending on the length of theslope, the tubing used sometimes can be quite long. There is a considerable amount of friction lossin long lines of any type duct, resulting in insufficient ventilation at the bottom of slope.

Tubing manufacturers usually supply tubing friction data to help ventilation engineers select theright size tubing to deliver the required amount of air. In order to compensate for laboratory data, acorrection factor should be used in calculating pipe resistance:

❏ For blowing system: multiply by 3

❏ For exhausting system: multiply by 7, then use Peabody ABC5 Resistance Chart

❏ For corrugated pipe:

For a 3-in by 1-in corrugated pipe: reduce effective diameter by 1-in

For a 3-in by 2-in corrugated pipe: reduce effective diameter by 2-in

When there are obstructions in the airway:

Effective Area = 0.492OA (A' )

where O = perimeter;A = Original area; and,A' = Actual area.

5 Peabody ABC, Warsaw, Indiana.


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CURRENTLY AVAILABLE SIMULATION PROGRAMSAppendix 12-3

Most of the ventilation programs currently available provide an interactive, understandable interfacewith the user. They can be categorized into two major groups: mainframe ventilation programs andmicrocomputer ventilation programs.

1) Michigan Tech. Ventilation Program

This program is derived from early versions of programs developed in West Germany in the1960s. The program, using Hardy Cross iterative technique to balance the network, is very similarto the program of the British National Coal Board issued in 1967. Modifications made includeidentifications of airways, calculations of natural ventilation pressure, efficient fan curveapproximations, and streamlined output.

2) MFIRE 2.2 – Bureau of Mines

This program is derived from early versions of programs developed at Michigan TechnologicalUniversity. It is currently in the microcomputer version and, like its predecessor, is capable ofsimulating routine mine ventilation network problems and also models the response of ventilationnetwork under the influence of thermal disturbances, such as mine fires (both fuel rich and oxygenrich type) and cooling stations. Fires can be specified as a fixed source of output heat and productsof combustion, or allowed to vary as a function of oxygen delivery. In addition, the programcalculates the concentration, distribution, and propagation of contaminants in a ventilation system,such as fumes of a fire. Unlike previous network programs, MFIRE accommodates both steadyand transient disturbances, including unplanned events, such as fires, and routine events, such asfans starting and stopping or doors opening and closing. The program has extremely flexible inputrequirements and output options. Natural ventilation, recirculation, and positive and negative ther-mal and mechanical energy inputs to the ventilation system are accommodated. Mass-based flowrates are utilized with reference to a known temperature and air density at a specified location.Methane evolution also can be specified.

3) Mine Ventilation Services, VNETPC 3.1, CLIMSIM

This is an interactive network analysis program with graphic output provided for a pen plotter, butnot on the CRT screen. Four methods of entering or calculating resistance are provided. VNETPC,which runs on a mainframe computer, is a similar program for large networks .

The CLIMSIM program simulates variations in psychrometric conditions along any mine air-way, shaft, or slope that affect climatic conditions in mines. Data requirements include airflow andwet bulb/dry bulb temperatures at inlet, airway geometry and age, rock thermal properties, andpower and positions of equipment and cooling plant. Other programs available from MineVentilation Services include:

❏ NETCOR, correlation between measured airflow and computed airflow;❏ PSYCHRO, psychrometric table or chart replacement;❏ GASSIM, gas emissions and concentrations;❏ BARSUR, thermodynamic relationships for pressure drops, airway resistance, and natural


237

ventilating pressures; and❏ LEAKAGE, air leakage through a line of stoppings/doors between intake and return air-

ways.

Other programs include calculations of rock thermal properties, flow in compressed air pipe,isentropic fan efficiency, optimum shaft size, and rate of methane desorption for coal.

4) Floyd C. Bossard and Associates, MIVENDES

In addition to the ordinary airway resistance values and horsepower requirements, the MIVENDESprogram also provides:

❏ Heating and cooling of air – Sources of heat include adiabatic compression, electromechan-ical equipment, explosives, and natural oxidation processes. Heating of mine inlet air andcooling of air on the surface or underground by indirect cooling or evaporative coolingtechniques are built in.

❏ Air psychrometry – Psychrometric properties temperatures, humidity, moisture, apparentand specific air volume, gas constant, vapor pressure of water, and dry air pressure.

❏ Diesel exhaust gases – Concentrations of carbon monoxide, carbon dioxide, nitrous ox-ides, and nitrogen dioxide are predicted.

❏ Primary and booster fans, airflow, methane, and radon emissions.

5) Geomin, Ventilation Design

This package provides an interactive design capability for three-dimensional networks with forcedventilation, natural ventilation, or both. The program is interactive and includes 3-D graphics dis-play capabilities. Fans may be internal or external and can be treated as either constant or variablepressure sources. The user can specify minimum airflow requirements in network branches, suchas for working faces. The output is flagged if the analytical results do not meet, or exceed, thepredetermined value.

6) Hall, MINVENT, VENTDAT

The VENTDAT program is used to create the data file for MINVENT, the network analysis pro-gram. MINVENT uses the Hardy Cross principles and an incompressible flow network. Leakageis handled differently, because it is not accounted for in the final balance. The quantity of airleaving the mine does not have to equal that entering.

The program allows for changes in specific volume of the air caused by pressure, temperature,or humidity changes; addition of compressed air; leakage through old workings or broken ground;and errors in the ventilation survey. Natural ventilation pressure can be included.

A user commented that the program works well if the network is fine tuned. Input is tediousbecause 12 items per airway are required, although the program documentation states that it is notnecessary to enter all the values.

7) HTME (Cerchar), P.C.Vent, VENDIS

The VENDIS program provides network calculations and an interactive graphic display. Networkdata can be entered by a combination of keyboard and digitizer entry. User input includes depth,resistance, temperature, and node (junction) location in three dimensions.


238

Results can be displayed on the graphic screen and the user can modify the resistance andtemperature and display the new results. The scale of the network can be changed and theviewpoint can be changed. When the network is displayed at certain angles, the result appears 3-dimensional. The network also can be output to a pen plotter for a paper copy.

8) MSHA, PENVEN, IDCEPS

The IDCEPS program interactively asks the user for data needed as input to the PENVEN pro-gram. The PENVEN program uses the ventilation program developed by Y. J. Wang and includesmodifications added by MSHA. The changes include:

❏ The program was broken into modules.❏ The input method was changed to a more flexible data acceptance.❏ Conversion factors can be specified for input data.❏ Fan curves are fitted with an unweighted least-squares fit and Newton's divided difference

interpolating polynomial techniques is used.❏ The user specifies the presumed operating point of each fan along with upper and lower

limits.❏ Total pressures can be printed for all junctions.❏ The user can input a starting guess at the balanced quantity distribution. The program will

also construct a first guess.

The program is in FORTRAN and has been run on a microcomputer by at least one company.

9) Penn. State University, MICROVENT (Disk #2)

The mainframe code version is available in many conference proceedings and government contractreports. A microcomputer version, named MICROVENT, available on Disk #2 for the Apple com-puter is a limited version of the mainframe program.

The micro version accepts only 50 branches and 5 different fans. Other programs on the diskinclude ventilation pressure survey calculation, network balancing, regulator sizing, ventilation of a5-entry section, and cost analysis of ventilation shafts.

10) Virginia Tech, VENTSIM

The VENTSIM calculates air quantities, airway resistance, pressure drops, and horsepowerrequirements. A program list is available in government publications and a copy of a tape with theprogram also is available. The program was written for the mainframe and Virginia Tech developeda version for the microcomputer.

11) Chamber of Mines Research Organization (COMRO), ENVIRON (former HEATFLOW &VENTFLOW)

The ENVIRON, released in 1986, combined both HEATFLOW and VENTFLOW into oneprogram. It is an interactive computer program for the simultaneous analysis of heat loads andmine ventilation systems at all mining depths on both local and a mine-wide basis. It provides a fullthermodynamic analysis of the mine and can be used to simulate existing ventilation and refrigera-tion systems, to identify the optimum mix of ventilation and refrigeration requirements, and to


239

carry out "what-if" studies. The program takes into account air density changes in deep mines,including automatic adjusting of fan characteristics, natural ventilation pressures throughout thenetwork, energy losses, associated costs for each airway, and the energy consumption and runningcost of each fan.

12) MINE FIRE SIMULATOR – Strata Mechanics Research Inst., Polish Academy of Science,Cracow, Poland

The MINE FIRE SIMULATOR was developed by the Polish Academy of Science and was codedin Pascal. The program integrates three parts: a conventional network calculation program; a pro-gram to simulate the fire source (real-time heat and combustion products simulator); and a programto calculate the air temperature changes due to a fire. The package provides a dynamic (animated)representation of the fire's progress, a color-graphic visualization of the spread of combustionproducts, temperature, flow, and other parameters throughout the ventilation system in real time.The program is fully interactive. All data are entered from the keyboard during program execution.

13) Other In-house Programs

CONSOL, Inc. has developed its in-house stand-alone ventilation simulation program. Theprogram is based on MFIRE, but with all editing and plotting features similar to that of theAUTOCAD. It provides a powerful tool for simulation and planning.

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Ventilation Networks," Proc. 6th Int'l Mine Ventilation Cong., Ramani, R.V., ed.,SME/AIME, New York, pp. 395-402.

Bruzewski, R.G. and Aughenbaugh, N.B. (1977) Effects of Weather on Mine Air," Min. Cong.Journ., Sep., pp. 23-25.

Cross, H. (1936) Analysis of Flow in Networks of Conduits or Conductors, Bull. 286,Engineering Experiment Station, University of Illinois, Nov., 29 pp.

Deliac, E. P., (1985) "Development of Ventilation Software on PC in France and the Applicationto the Simulation of Mine Fires," Proc. 2nd U. S. Mine Vent Sympo, Mousset-Jones, P., ed.,A.A. Balkema, Rotterdam, pp. 19-27.

Edwards, J. C., and R. E. Greuer, (1982) "Real-time Calculation of Product-of-CombustionSpread in a Multi-level Mine," USBM, Information Circular No. 8901, 117 pp.

Firganek, B. et al. (1975) "Control of Ventilation Processes in Coal Mines," Proc. 1st Int'l MineVent Cong., Mine Vent. Soc. South Africa, Johannesburg, South Africa, Sep., 9 pp.

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Ventilation Systems under the Influence of Mine Fires," USBM Contract No. S0241032,Mich. Tech Univ., USBM OFR 115 (1)-78, 165 pp.

Greuer, R. E. (1979) "A New Program for the Design of Ventilation Emergency Plans," Proc. 2ndInt'l Mine Vent Cong., Mousset-Jones, P., ed., SME, New York, pp. 129-134.

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Greyvenstein, G.P., et al. (1992) "The Optimization of Ventilation Ducting in an Upcast MineShaft Tee Junction and Fan Drifts with Computational Fluid Dynamics," Proc. 5th Int'l MineVentilation Cong., Howes, M.J. and Jones, M.J., ed., Inst. Min. and Metall., London, pp.359-362.

Hardcastle, S. G., Dasys, A. and Leung, E. (1997) "Integrated Mine Ventilation ManagementSystems," Proc. 7th Int'l Mine Vent. Cong., Ramani, R.V., ed., SME, Littleton, CO, pp. 19-24.

Jain, S. and Mutmansky, J.M. (1987) "Comparative Analysis of An Innovative Ventilation Systemfor Large-Scale Longwall Mining," Proc. 3rd U.S. Mine Ventilation Sympo., Mutmansky,J.M., ed., SME, Littleton, CO, pp. 75-84.

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McPherson, M.J. (1988) "Subsurface Environmental Engineering – A Look into the Future,"Proc. 4th Int'l Mine Ventilation Cong., Gillies, A.D.S., ed., Australasian Inst. Min. Metall.,Melbourne, Australia, pp. 19-27.

Neethling, A.F. (1989) "Practical Consideration when Ventilating the Goaf," Journ. MineVentilation Soc. S.A., Feb., pp. 35-39.

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Ren, T.X., Edwards, J.S. and Jozefowicz, R.R. (1997) "CFD Modeling of Methane Flow aroundLongwall Coal Faces," Proc. 6th Int'l Mine Ventilation Cong., Ramani, R.V., ed., SME, NewYork, pp. 247-251.

Rose, H.J.M. and Bluhm, S.J. (1992) "Ventilation and Refrigeration Design for a New Shaft


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System at Impala Platinum Limited," Proc. 5th Int'l Mine Ventilation Cong., Howes, M.J. andJones, M.J., ed., Inst. Min. and Metall., London, pp. 1-9.

Srivastava, S.C., et al. (1995) "On-Line Ventilation Network Analysis and Graphic Representationof Ventilation Parameters – Part I, Planned, Desired and Current Air Quantities," Inst. Min.Engrs., Nov., pp. 349-351.

Stevenson, J.W. and Kingery, D.S. (1966) "Effects of Bleeder Entries During AtmosphericPressure Changes," USBM Rpt Investigation No. 6786, 15 pp.

Tien, J. and Bjork, J. (1976) "Computer Helps Mine Ventilation Planning at White Pine Mine,"E&MJ, Aug, pp. 77-81.

Tominaga, Y. and Y. Umeki (1991) "Mine Ventilation Control by Using a Transition Diagram ofAirflow Rate," Proc. 5th U.S. Mine Vent. Sympo, Wang, Y.J., ed., Littleton, CO, pp. 528-533.

Zhber, M.D. (1997) "Application of Coalbed Methane Reservoir Simulation for Estimation ofMethane Emissions in Longwall Mining," Proc. 6th Int'l Mine Ventilation Cong., Ramani,R.V., ed., SME, New York, pp. 435-440.

Other Related Information

Barnes, R. J. and Rellier, F. (1989) "Adjustment of Mine Ventilation System Parameters," Proc.4th U.S. Mine Vent Sympo, McPherson, M.J., ed., SME, Littleton, CO, pp. 113–121.

Bossard, F. C. (1985) "Designing Mine Ventilation Systems - Case Studies," Proc. 2nd U. S.Mine Vent Sympo, Mousset-Jones, P., ed., A.A. Balkema, Rotterdam, pp. 393-401.

Brown, J. R. et al (1979) "The Development, Application, and Correlation of ComputerSimulation Techniques of the Mount Isa Ventilation System," Proc. 2nd U. S. Mine VentSympo,, Mousset-Jones, P., ed., A.A. Balkema, Rotterdam, pp. 135-147.

Bruce, W. E. and Koenning, T. H. (1987) "Computer Modeling of Underground Coal MineVentilation Circuits: Selection and Application of Airway Resistance Values," Proc. 3rd MineVent Sympo, Mutmansky, J.M., ed., SME, Littleton, CO, pp. 519-525.

Calizaya, F. and Mousset-Jones, P. (1994) "A Computer Program for Solving Complex AuxiliaryVentilation Systems," SME/AIME Annual Meeting, Reno, NV, Preprint # 94-187, 9 pp.

Crous, S. J. et al (1984) "Review of Ventilation on South African Coal Mines," Proc. 1st Int'lMine Vent Cong, Johannesburg, South Africa, Sep, 8 pp.

Didyk, M., et al, (1977) "Mine Ventilation Network Theory, User's Manual for PSU/MVS,"Final report to USBM Cont. No. H0133046.

Edwards, J. C. and Li, J. S. (1984) "Computer Simulation of Ventilation in Multilevel Mines,"Proc. 3rd Int'l Mine Vent Cong, Howes, M.J. and Jones, M.J., ed., Inst. Min. and Metall.,Harrogate, England, pp. 47-51.

Gaines, P.A. (1978) "Practical Applications of the Michigan Technological University MineVentilation Program," M.S. Thesis, Michigan Tech. University, 175 pp.

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242

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243

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Trutwin, W, et al. (1992) "Computer Simulation of Transients in Mine Ventilation," Proc. 5th Int'lVent. Cong., Hemp, R., ed., Mine Ventilation Soc. S.A., Johannesburg, pp. 193-200.

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Wang, X. and Liu, X. (1989) "One Cast Adjustment over the Mine Ventilation Measurements,"Proc. 4th U.S. Mine Vent Sympo, McPherson, M.J., ed., SME, Littleton, CO, pp. 128–133.

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Wang, Y. J. (1982) "Critical Path Approach to Mine Ventilation Networks with Controlled flow,"Trans. SME-AIME, Vol. 272, No. 4, pp. 1862-1872.

Wang, Y. J. (1983) "Minimizing Power Consumption in Multiple-Fan Networks by EqualizingFan Pressure," Int'l Journ of Rock Mech. and Min. Sci, Vol. 20, No. 4, pp. 171-179.

Wang, Y. J. and Hartman, H. L. (1967) "Computer Solution of Three Dimensional MineVentilation Networks with Multiple Fans and Natural Ventilation," Intl. J. Rock Mech. Min.Sci., Vol. 4, pp. 129-154.

Wang, Y. J. and Saperstein, L. W. (1971) "Computer-Aided Solution of Complex VentilationNetworks," Trans. SME/AIME, Vol. 247, Sep., pp. 238-250.

Wheeler, A. J. and Notley, K. R. (1984) "Computer Modeling of Radon-Related Contamination ina Mine Ventilation Network," Proc. 3rd Int'l Mine Vent Cong, Howes, M.J. and Jones, M.J.,ed., Inst. Min. and Metall., pp. 115-120.

Wu, X. and Topuz, E. (1987) "The Determination of Booster Fan Locations in UndergroundMines," Proc. 3rd U.S. Mine Vent Sympo, Mutmansky, J.M., ed., SME, Littleton, CO, pp.401-407.

Wu, X. and Topuz, E. (1989) "Comparison of Methods for Determination of Booster FanLocations in Underground Mines," Proc. 4th U.S. Mine Vent. Sympo, Mutmansky, J.M.,ed., Littleton, CO, pp. 355-362.

Note: References on face ventilation and related subjects are abundant and can be found in manysources. Refer to those sources for further entries.

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