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Application of MULTIFLUX for air, heat, and moisture flow simulations

Application of MULTIFLUX for air, heat, and moisture flow simulations. Dr. George Danko, Professor and Davood Bahrami, Research Fellow Department of Mining Engineering Mackay School of Earth Sciences and Engineering College of Science University of Nevada, Reno

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Application of MULTIFLUX for air, heat, and moisture flow simulations

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  1. Application of MULTIFLUX for air, heat, and moisture flow simulations Dr. George Danko, Professor and Davood Bahrami, Research Fellow Department of Mining Engineering Mackay School of Earth Sciences and Engineering College of Science University of Nevada, Reno 2008 12th US/North American Mine Ventilation Symposium June 9-11, 2006, Reno, Nevada.

  2. Goals • Increase accuracy in predictability of temperature, humidity, and pollutant concentration related to safety and health. • Reduce energy consumption for ventilation and air cooling

  3. MULTIFLUX: A coupled, air, heat, and moisture flow simulation- air contaminant transport can be added Heat and moisture distribution Air distribution Pollutant distribution

  4. Thermal-Hydrological-Airflow-Contaminant Modelling with MULTIFLUX Air flow Model Selection (THC) In-Rock Transport Model Selection (THC) FLUENT Textbook Empirical MF CFD TOUGH or NUFT Gibbson’s Age Function Analytical User’s selection for NTCF surrogate Rock Model Abstraction model-building Numerical Transport Code Function alligator Air Flow and Transport Model Abstraction: Lumped-parameter CFD model Coupled Model Solver Lumped-parameter CFD DISAC NTCF OUTPUT: Temperature field Humidity field Heat flow field Moisture flow field • MF CFD – Multiflux Computational Fluid dynamics • LLNL – Lawrence Livermore National Laboratory • NTCF – Numerical Transport Code Functionalization

  5. Rockmass NTCF Matrix Model • NTCF model: • qh = F1(T, P,...) • qm = F2(T, P, wf,...) with wf = f1(T,P,...) For example: T, P, qh, qm T, P, qh, qm T, P, qh, qm F1 , F2: time-invariant, dynamic operators T ,P : wall temperature and partial vapor pressure vectors qh, qm:heat and moisture fluxes To , Po :initial values qho, qmo : initial fluxes for To and Po hh , hm : dynamic admittance matrices for heat flow determined by MULTIFLUX mh, mm : dynamic admittance matrices for moisture flow determined by MULTIFLUX

  6. In-drift heat, moisture, and air flow models: lumped-parameter Computational Fluid Dynamics (CFD). F3, F4, and F5 are matrices determined by MULTIFLUX from governing equations:

  7. Mine-wide heat moisture and air flow model with MULTIFLUX Air flow network model Heat flow network model NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF NTCF Moisture flow network model

  8. Example of heat sources and transport connections in the proposed underground nuclear waste repository at YM

  9. Air intake shaft rockmass Temperature and humidity measurement Station 2 dry surface 247 m air wet surface cooling water Airflow temperature and humidity measurement Station 1 Air exhaust extension Hydraulic diameter, Dh =2.7333 m Example – Comparison with CLIMSIMPlan view and cross sectional view of a 247-m drift segment in the CLIMSIM validation case.

  10. Example – Heat and Moisture Flow Model in MULTIFLUX for Comparison with CLIMSIM NTCF model from Gibbson’s function Heat Tdry Tdry Tair Twet Heat loss Station 1 Twet Tcooling water Tcooling water NTCF model from Gibbson’s function Station 2 13 elements Moisture Station 1 P=Psat P=Psat at surface temperature Qm=0 in-role NTCF model

  11. Input Data for the Test Case – Same as in CLIMSIM

  12. Air temperatures and flow tables at drift entrance same as in CLIMSIM

  13. Measured and simulated air temperatures at drift exit

  14. Root-Mean-Square Error of fit between models and measurement Root-Mean-Square difference between MULTIFLUX and CLIMSIM modes

  15. Air temperature at drift exit

  16. Relative humidity at drift exit

  17. Comparison of total strata heat

  18. Comparison of sigma heat

  19. Conclusions • MF is designed with great flexibility for solving large-scale problems such as a ventilated underground mine or a high-level nuclear waste repository. • For example, a 760m-long emplacement drift with hundreds of heat sources with it, has also been modeled with MF for the proposed nuclear waste repository at Yucca Mountain • The software can be used to solve for the coupled (1) thermal, (2) hydrologic and (3) air flow problems simultaneously. • All relevant processes of the multi-physics problem are modeled in air space: • (1) heat conduction, radiation, convection, latent heat, viscous dissipation, auto compression for heat; • (2) moisture convection, diffusion, dispersion, condensation evaporation for moisture; and • (3) laminar or turbulent, powered or natural flow for air flow. • The presented test case shows that MF captures the relevant heat and moisture transport processes excellently.

  20. Questions

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