8
This improvement resulted in an efficiency rise from 4%
in Layout-I to 8.4% in Layout-II. Nonetheless, a marginal
effect on the in-place stopping layouts was noticed at other
areas, specifically faces D and F, whereas no impact was
observed at faces F and G.
Air recirculation at crosscuts (X1, X2, etc.) has been
computed and is presented in Table 2. This computation
illustrates the percentage of air recirculation within specific
cross-sections compared to the total airflow entering the
inlets. Overall, Layout-II showed a higher circulation of air
around the outby stoppings (X1 and X2).
SUMMARY
NIOSH researchers conducted two air ventilation surveys
in an underground limestone mine in Pennsylvania to vali-
date CFD model for simulating air flow in large opening
stone mines. The collaborated mine used a split ventilation
system with two intake and one return entrances, featuring
9.15-m height and 15.24-m width entries, and two 1.83-m
propeller booster fans. The intake fan directed external air
into the mine, while the exhaust fan facilitated air outflow.
The first survey involved 60-second anemometer traverses
at 33 stations within the mine. Smoke tubes visualized
airflow patterns, including stagnant areas. In the second
survey, more traverses were conducted, and it was noted
ongoing production activities, altered mine boundaries,
and reorientation of intake booster fan.
The study utilized ANSYS-Fluent, a widely accepted
software tool in underground ventilation engineering, to
investigate fluid-flow and heat transfer issues. The study
employed a 3D, steady-state, incompressible Navier-Stokes
equation solution with Reynolds-averaged (RANS) equa-
tions and the k-epsilon turbulence model. Pressure bound-
ary conditions were assigned at the model’s inlets and
outlet. Booster fans were simulated with constant pressure
gradients. The model featured various wall conditions,
and gravity was considered. Convergence was achieved
within 200–300 iterations. The study recommended a
k-epsilon turbulence model approach for large-opening
stone mines and a scalable wall function for varied y-plus
values. Meshing involved polyhedral cells with specific layer
configurations.
Conducting a mesh independence study is crucial to
optimize computational speed and model accuracy. This
study evaluated three mesh sizes (coarse, medium, and
fine) with 7.6 M, 13.2 M, and 30.1 M cells, respectively.
Mesh refinement was applied in the surface meshing stage
with different surface mesh sizes. Velocity profiles at vari-
ous stations in a mine were analyzed, leading to the selec-
tion of the medium mesh size for CFD modeling due to its
consistency.
A CFD model’s validity was assessed by comparing it to
data from a mine ventilation survey. Results showed good
correlation (R-square =0.83) with 33 winter survey loca-
tions. In a spring survey with 50 locations, there was a good
correlation (R-square =0.57).
This research paper investigates the influence of differ-
ent in-place stone stopping arrangements on face ventila-
tion efficiency and air recirculation at crosscuts between
exhaust and intake entries. Two layouts, Layout-I and
Layout-II were simulated. Layout-I features shorter stone
stoppings, while Layout-II has longer stone stoppings.
The study adjusted various factors based on spring venti-
lation findings, including intake fan orientation and inlet
portal mass flow conditions. Airflow patterns were similar
for Layout-I and Layout-II, with most airflow from Inlet-1
moving through crosscut (X1). Ventilation efficiency nota-
bly improved in Layout-II at advanced faces (A, B, and
C), increasing from 4% to 8.4% compared to Layout-I.
Other faces (D, E, F, and G) showed no significant impact.
Layout-II demonstrated increased air recirculation at outby
stoppings.
STUDY LIMITATIONS
In this research, the CFD models were validated using a
small mine layout without benching and was not verified
to be applied to a larger fully developed mine, mines with
different entry and/or pillar sizes, or to one that employs
benching. The effect of vehicle movement on airflow was
not considered in the model. The primary objective of the
modeling exercise was to assess the influence of hypothetical
layouts of in-place stone stopping on ventilation efficiency.
Despite hypothetical modeling results indicating potential
for improved ventilation efficiency, these proposed layouts
for in-place stopping have not yet been validated through
field testing.
DISCLAIMER
The findings and conclusions in this study are those of
the authors and do not necessarily represent the official
Table 2. Airflow and percentages of air recirculation at
the crosscuts between exhaust and intake entries in both
Layout-I and Layout-II.
This improvement resulted in an efficiency rise from 4%
in Layout-I to 8.4% in Layout-II. Nonetheless, a marginal
effect on the in-place stopping layouts was noticed at other
areas, specifically faces D and F, whereas no impact was
observed at faces F and G.
Air recirculation at crosscuts (X1, X2, etc.) has been
computed and is presented in Table 2. This computation
illustrates the percentage of air recirculation within specific
cross-sections compared to the total airflow entering the
inlets. Overall, Layout-II showed a higher circulation of air
around the outby stoppings (X1 and X2).
SUMMARY
NIOSH researchers conducted two air ventilation surveys
in an underground limestone mine in Pennsylvania to vali-
date CFD model for simulating air flow in large opening
stone mines. The collaborated mine used a split ventilation
system with two intake and one return entrances, featuring
9.15-m height and 15.24-m width entries, and two 1.83-m
propeller booster fans. The intake fan directed external air
into the mine, while the exhaust fan facilitated air outflow.
The first survey involved 60-second anemometer traverses
at 33 stations within the mine. Smoke tubes visualized
airflow patterns, including stagnant areas. In the second
survey, more traverses were conducted, and it was noted
ongoing production activities, altered mine boundaries,
and reorientation of intake booster fan.
The study utilized ANSYS-Fluent, a widely accepted
software tool in underground ventilation engineering, to
investigate fluid-flow and heat transfer issues. The study
employed a 3D, steady-state, incompressible Navier-Stokes
equation solution with Reynolds-averaged (RANS) equa-
tions and the k-epsilon turbulence model. Pressure bound-
ary conditions were assigned at the model’s inlets and
outlet. Booster fans were simulated with constant pressure
gradients. The model featured various wall conditions,
and gravity was considered. Convergence was achieved
within 200–300 iterations. The study recommended a
k-epsilon turbulence model approach for large-opening
stone mines and a scalable wall function for varied y-plus
values. Meshing involved polyhedral cells with specific layer
configurations.
Conducting a mesh independence study is crucial to
optimize computational speed and model accuracy. This
study evaluated three mesh sizes (coarse, medium, and
fine) with 7.6 M, 13.2 M, and 30.1 M cells, respectively.
Mesh refinement was applied in the surface meshing stage
with different surface mesh sizes. Velocity profiles at vari-
ous stations in a mine were analyzed, leading to the selec-
tion of the medium mesh size for CFD modeling due to its
consistency.
A CFD model’s validity was assessed by comparing it to
data from a mine ventilation survey. Results showed good
correlation (R-square =0.83) with 33 winter survey loca-
tions. In a spring survey with 50 locations, there was a good
correlation (R-square =0.57).
This research paper investigates the influence of differ-
ent in-place stone stopping arrangements on face ventila-
tion efficiency and air recirculation at crosscuts between
exhaust and intake entries. Two layouts, Layout-I and
Layout-II were simulated. Layout-I features shorter stone
stoppings, while Layout-II has longer stone stoppings.
The study adjusted various factors based on spring venti-
lation findings, including intake fan orientation and inlet
portal mass flow conditions. Airflow patterns were similar
for Layout-I and Layout-II, with most airflow from Inlet-1
moving through crosscut (X1). Ventilation efficiency nota-
bly improved in Layout-II at advanced faces (A, B, and
C), increasing from 4% to 8.4% compared to Layout-I.
Other faces (D, E, F, and G) showed no significant impact.
Layout-II demonstrated increased air recirculation at outby
stoppings.
STUDY LIMITATIONS
In this research, the CFD models were validated using a
small mine layout without benching and was not verified
to be applied to a larger fully developed mine, mines with
different entry and/or pillar sizes, or to one that employs
benching. The effect of vehicle movement on airflow was
not considered in the model. The primary objective of the
modeling exercise was to assess the influence of hypothetical
layouts of in-place stone stopping on ventilation efficiency.
Despite hypothetical modeling results indicating potential
for improved ventilation efficiency, these proposed layouts
for in-place stopping have not yet been validated through
field testing.
DISCLAIMER
The findings and conclusions in this study are those of
the authors and do not necessarily represent the official
Table 2. Airflow and percentages of air recirculation at
the crosscuts between exhaust and intake entries in both
Layout-I and Layout-II.