The developed water supply strategy was implemented on Mine A’s WRS for validation. The simulated strategy was compared with the actual results obtained from the mining operation.
Water demands were used to represent the mining water demand. As mentioned, existing infrastructure was identified and reconfigured to develop the return pipeline. Therefore, no additional expenditure was added as this was done by the mine personnel. Table 11 compares the average errors between the simulation and actual results.
0 5000 10000 15000 20000
Power [kW]
Time [hh:mm]
Refrigeration power consumption
Baseline Simulation
High pressure water supply strategy for mine bulk air coolers 85 Table 11: Average error between the simulated and test/actual data for the chosen KPIs
KPI Actual Simulated Error [%]
CBAC inlet water flow 65.97 64.87 1.70
CBAC inlet water temperature 12.25 13.02 5.92
CBAC outlet air temperature 20.82 21.45 2.93
100L hot water dams’ level 79.13 83.61 5.36
71L hot water dam level 95.65 92.56 3.34
92L cold water dam level 87.45 91.07 3.98
71L cold water dam level 77.61 79.59 2.48
Pumping power consumption 13 994.27 14 093.48 0.70 Refrigeration power consumption 17 531.41 16 609.20 5.55
Table 11 shows that the largest errors between the simulated and actual results were for inlet water temperature, several dam levels, and refrigeration power consumption. The reasons for the errors will be provided below. The following graphs illustrate the actual and simulated KPIs.
Figure 52 shows the CBAC inlet water flow. An average error of 1.70% was obtained when comparing the simulation and actual results.
Figure 52: Actual CBAC inlet water flow compared with the simulation results 50
55 60 65 70 75
Water flow [ℓ/s]
Time [hh:mm]
CBAC inlet water flow
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 86
The small error was due to the water demand component that was used to represent the mining water flow. The impact of opening the return valve to a position of 15% was the same for the actual and simulation results, meaning that the correct inlet water flow was obtained.
Figure 53 illustrates the CBAC’s inlet water temperature. A percentage error of 5.92% was observed between the actual and simulation results.
Figure 53: Actual CBAC inlet water temperature compared with the simulation results
A certain amount of heat had to be added to the simulation to compensate for the hot conditions underground affecting uninsulated pipelines. Therefore, the error was attributed to the heat added to the pipes, which was identified during the simulation verification and selected based on the conditions at that time. These conditions were not changed while simulating the control strategy as an accurate prediction could not be made, which resulted in the error experienced between the actual and simulation results.
Figure 54 depicts the outlet air temperature of the CBAC for the simulated and actual results.
A percentage error of 2.93% was observed.
0 2 4 6 8 10 12 14 16
Temperature [°C]
Time [hh:mm]
CBAC inlet water temperature
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 87 Figure 54: Actual CBAC outlet air temperature compared with the simulation results
The error was relatively small and outlet air temperatures were simulated accurately.
Therefore, it was assumed that the CBACs were calibrated accurately.
The following figures show the impacts on the hot and cold water dam levels. The percentage errors for the different dam levels were due to the actual dam levels being controlled by control room operators. However, the simulated dam levels were controlled by step controllers, which controlled the dam levels between the given set points. Therefore, the errors were attributed to the difficult incorporation of human interface. However, all dam levels were within acceptable ranges.
Figure 55 shows the dam level for the actual and simulated results for the 100L hot water dams. A percentage error of 5.35% was observed.
0 5 10 15 20 25
Temperature [°C]
Time [hh:mm]
CBAC outlet air temperature
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 88 Figure 55: Actual 100L hot water dams’ level compared with the simulation results
Figure 56 compares the actual 71L hot water dam level with the simulation results. An average percentage error of 3.34% was observed. From 19:00, the actual dam level remained constant until 24:00 due to no water being transferred to the 71L refrigeration plants as control operators switched off these refrigeration plants as part of an existing DSM initiative. This was also done as sufficient water was available in the 71L cold water dam to supply the CBAC with additional water. Again, operators switched equipment on/off as they deemed fit, whereas the simulation had a set of prescribed limits and/or set points according to which the simulation was controlled.
Figure 56: Actual 71L hot water dam level compared with the simulation results 0
20 40 60 80 100
Level [%]
Time [hh:mm]
100L hot water dams' level
Simulation Actual
0 20 40 60 80 100
Level [%]
Time [hh:mm]
71L hot water dam level
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 89
Figure 57 illustrates the 92L cold water dam level for the actual and simulation results. An average percentage error of 3.98% was observed.
Figure 57: Actual 92L cold water dam level compared with the simulation results
Figure 58 depicts the actual and simulated results for the 71L cold water dam level with an average error of 2.48%. The initial dam level again differed based on the initial dam level that was set in the simulation.
Figure 58: Actual 71L cold water dam level compared with the simulation results
Figure 59 illustrates the actual and simulated power consumption of the dewatering pumps.
Even though only a small error of 0.5% was observed, profiles differed significantly throughout the 24-hour period. This was attributed to the step and PI controllers that were used in the
0 20 40 60 80 100
Level [%]
Time [hh:mm]
92L cold water dam level
Simulation Actual
0 20 40 60 80 100
Level [%]
Time [hh:mm]
71L cold water dam level
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 90
simulation to mimic human interface. Thus, for the actual results, control room operators had control over pumping to switch pumps on/off as they deemed fit. However, for the simulation, pumps were switched on/off based on water dam levels.
Figure 59: Actual pumping power consumption compared with the simulation results
Figure 60 shows the refrigeration power consumption. An average error of 5.55% was observed between the actual and simulation results due to simulation switching refrigeration plants on/off based on a temperature set point. However, control room operators use these machines differently. Furthermore, the simulation switched components on/off instantaneously whereas during the actual tests, machines may have cut back or be used at a lower slide vane angle. The reasons stated above resulted in the rather large error that was observed between the actual and simulated results.
0 5 000 10 000 15 000 20 000 25 000
Power [kW]
Time [hh:mm]
Pumping power consumption
Simulation Actual
High pressure water supply strategy for mine bulk air coolers 91 Figure 60: Actual refrigeration power consumption compared with the simulation results
However, the simulation was deemed accurate with a rather small percentage error of 3.55%
between the KPIs of the simulated and actual results. The next step was to implement the strategy on the WRS of Mine A.