VERIFICATION AND CALIBRATION OF VENTILATION NETWORK MODELS Frank von Glehn, Wynand Marx and Steven Bluhm BBE Consulting

1. VERIFICATION AND CALIBRATION OF VENTILATION NETWORK MODELS Frank von Glehn, Wynand Marx and Steven Bluhm BBE Consulting South Africa

2. Two approaches to calibrate network Potential errors Some results using 2nd approach Real-time network analysis

3. Network simulators have come a long way from Analogue engines Card input data on ‘digital’ computers Early progams on personal or desktop computers 21st century systems, full graphics, real-time data, web based Powerful for what-if analyses

5. Two main approaches to verify simulation networks Do full pressure survey and calculate an R or modified Atkinson k factor for each branch. Use standard k factors and only do spot measurements to check predictions. Modify chosen k factors until predictions match measurements.

6. Detailed full-mine pressure surveys are important for: Training in terms of basic ventilation practice, measurement techniques, instrument handling Understanding the mine on micro scale

7. First approach Advantages: First-hand knowledge of whole mine Individual k factors for each branch Disadvantages: Requires big team to do measurements Requires many instruments Significant time spent on site

8. Second approach Advantages: Fewer people, instruments Short time Use modern PC power for efficient use of time Disadvantages Not every branch visited No ‘direct’ check of prediction for each branch

9. First approach measurement accuracy Consider 3 m x 3 m airway, 500 m long, average density 1.07 kg/m3, flow 37 m³/s, pressure drop 100 Pa Calculated Atkinson k factor 0.01 Ns2/m4 Accuracy of pressure reading is +-20 Pa (2mm or 0.079” water gauge), 20% Accuracy of flow reading is 10%

10. Atkinson equation dP = k L C Q² ρ A31.2 Atkinson equation dP = k L C Q² ρ A31.2 ∂k/k = ∂P/P + 2 . ∂Q/Q = 20% + 2 . 10% = 40%

11. Second approach measurement accuracy Consider pressure measurement across door with dP 3000 Pa (300 mm water gauge) Accuracy is still +-20 Pa, but error < 1 % % Error in larger flow generally also less Define k at a higher level of precision, rather than attempting to measure it directly

12. Examples of application

13. Coal mine

15. Deep gold mine

17. Real-time network analysis Place instruments all over mine?

18. Real-time network analysis Place instruments all over mine? Rather identify a few strategic locations and then predict what happens in rest of network Use second approach to calibrate network on on-going basis

19. Application in Energy management projects Monitor what happens in network when reduce flow to mine Ensure that no critical conditions reached If necessary, flow can be re-set

22. Conclusions Evaluate effect of k on the network rather than attempting to measure it directly Use measurements with low error potential to verify network Make efficient use of computing power to do what-if analyses