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Darren Woolf, Hoare Lea, London (UK) “How flow can you go?”

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The Future Envelope 12
Interreg IT-AU FACEcamp project
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Conference on Building Envelopes
20-21 May 2019, NOI Techpark, Bolzano (Italy)
"It’s all about performances".

Published in: Technology
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Darren Woolf, Hoare Lea, London (UK) “How flow can you go?”

  1. 1. The Future Envelope 12 It’s all about performances How flow can you go? Prof Darren Woolf Hoare Lea / Loughborough University www.interreg.net FACEcamp final event | Bolzano, 20-21 May 2019 FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.
  2. 2. Contents Ventilation flow: • Case study 1: Simulating wind pressures (driving force for air flow through façade) • Case study 2: Calculating pressure losses (effective areas & discharge coefficients) and resulting flow through façade openings Heat flow: • Case study 3: Heat flow through complex glazing systems • Case study 4: Impact of glass temperature on room air flow • Case study 5: Heat transfer with multiple phases (solid, air, water) and condensation risk The Future Envelope 12 final event 20-21 May 2019, Bolzano
  3. 3. Case study 1: Local wind pressure at a crack or opening The Future Envelope 12 final event 20-21 May 2019, Bolzano Wind flow around buildings is very complex. ‘Steady-state’ CFD calculation (no gusts, averaged flow).
  4. 4. Case study 1: Local wind pressure at a crack or opening The Future Envelope 12 final event 20-21 May 2019, Bolzano Pressure on horizontal plane 20m above ground level Positive and negative pressures with different magnitudes on different areas of façade. One connected pressure-flow system.
  5. 5. Case study 1: Local wind pressure at a crack or opening The Future Envelope 12 final event 20-21 May 2019, Bolzano Natural ventilation flow highly dependent on pressure differential between connected openings (e.g. across an apartment from one window to another).
  6. 6. The Future Envelope 12 final event 20-21 May 2019, Bolzano Case study 1: Local wind pressure at a crack or opening Dynamic thermal model Positive pressure predicted Uniform horizontally Negative pressure predicted (sheltered) Non-uniform horizontally CFD model WINDWARD FAÇADE:
  7. 7. The Future Envelope 12 final event 20-21 May 2019, Bolzano Case study 1: Local wind pressure at a crack or opening LEEWARD FAÇADE: Dynamic thermal model Negative pressure predicted CFD model Positive pressure predicted
  8. 8. The Future Envelope 12 final event 20-21 May 2019, Bolzano Case study 1: Local wind pressure at a crack or opening Dynamic thermal model settings for wind pressure coefficient: • Building type • Exposure • Height up facade Apartment results: Compliance test for overheating risk in living room / kitchen changed from ‘marginal fail’ to ‘pass’ using CFD-based wind pressure coefficients. Both bedrooms also improved.
  9. 9. Top-hung The Future Envelope 12 final event 20-21 May 2019, Bolzano Side-hung Discharge coefficient and effective area Bottom-hung Free areaDischarge coefficient (Cd) Pressure loss e.g. due to turbulence Effective area is NOT a width x height) Jones and Cook: A review of ventilation opening area terminology, Energy and Buildings, March 2016 ‘An effective area, defined as the product of its discharge coefficient and its free area, is proposed as a standard description because it is unambiguous and its measurement is governed by recognised standards.’ [Also ‘new’ CIBSE AM10] Flow rate = Factor x Pressure difference
  10. 10. Case study 2: Single-sided ventilation The Future Envelope 12 final event 20-21 May 2019, Bolzano Inside Outside Horizontal section through vent unit Vent unit zone Outside Occupied zone Perimeter zone Office space (adjacent spaces not shown)
  11. 11. Case study 2: Single-sided ventilation The Future Envelope 12 final event 20-21 May 2019, Bolzano Flow in Flow out Air velocity Flow out Flow in
  12. 12. Case study 2: Single-sided ventilation The Future Envelope 12 final event 20-21 May 2019, Bolzano For same geometry, pressure loss or effective area inwards ≠ pressure loss or effective area outwards. Effective area inwards (also input to dynamic thermal model) calculated to be six times less than original design target. Design impact of study: Attenuators removed. Energy dissipation rate Flow in Flow out
  13. 13. Heat flow through glazing and comfort conditions The Future Envelope 12 final event 20-21 May 2019, Bolzano g-value Shortwave radiation Surface convection Longwave radiation Sun patch spread over dynamic thermal model surface (changes location over time) Inside surface temperature of glass uniform over all surface (unless areas are split) Local shading Key glass properties
  14. 14. Case study 3: Heat flow through complex glazing system The Future Envelope 12 final event 20-21 May 2019, Bolzano Closed cavity façade (CCF) system Automatic interstitial blind operation in dynamic thermal model (reduced solar gain & glare control).
  15. 15. Case study 3: Heat flow through complex glazing system The Future Envelope 12 final event 20-21 May 2019, Bolzano • R&D with vendors to capture heat transfer and gains with required controls. • Challenge to vary blind operation with incident solar gains and resulting daylighting levels. • Challenge to vary internal artificial lighting and associated heat gains with blind operation. • Similar performance to brise soleil system which allowed floor to ceiling glazing. Model 1 Single external surface with four layers including blind Model 2 Single external zone with controls for blind
  16. 16. Case study 4: Impact of glass temperature on room air flow Winter Glass inside surface temperature 9.3°C Summer Glass inside surface temperature 31.2°C All surface temperatures fixed values in CFD taken from dynamic thermal model The Future Envelope 12 final event 20-21 May 2019, Bolzano
  17. 17. The Future Envelope 12 final event 20-21 May 2019, Bolzano Summer Case study 4: Impact of glass temperature on room air flow Glass temperature 31.2°C fixed and uniformCool jet does not reach occupied zone Supply air 0.7m3/s @14.0°C
  18. 18. The Future Envelope 12 final event 20-21 May 2019, Bolzano Winter Case study 4: Impact of glass temperature on room air flow Glass temperature 9.3°C fixed and uniformWarm jet does reach occupied zone Supply air 0.7m3/s @23.0°C
  19. 19. The Future Envelope 12 final event 20-21 May 2019, Bolzano Case study 4: Impact of glass temperature on room air flow Winter Fixed glass inside surface temperature Air Surface Variable glass inside surface temperature
  20. 20. Case study 5: Condensation risk and multi-phased flow The Future Envelope 12 final event 20-21 May 2019, Bolzano Supply Extract Pool Spa Heated floor Basement pool / spa room with light well to garden area above Light well ~28°C air temperature, ~60% RH
  21. 21. Case study 5: Condensation risk and multi-phased flow The Future Envelope 12 final event 20-21 May 2019, Bolzano Solid Pond water (assumed 0°C at top surface) Air with moisture Light well materials and conjugate heat transfer results (CFD) Does condensation drip off underside of acrylic?
  22. 22. T.water(in) = f [T.water(out), heat gain in pipe and through plant room, flow rate] Case study 5: Condensation risk and multi-phased flow The Future Envelope 12 final event 20-21 May 2019, Bolzano water(out) water(in) water(out) water(in) Pond water model
  23. 23. Case study 5: Condensation risk and multi-phased flow The Future Envelope 12 final event 20-21 May 2019, Bolzano Light well condensation risk • Moisture dynamics – slight fogging or large droplets forming and falling? • Strategy was to increase thickness of acrylic and gauge complaints!
  24. 24. Summary and conclusions • Dynamic thermal and CFD modelling are powerful approaches used to drive building design. • Understanding limitations of the adopted approaches supports good interpretation and, therefore, development of better designs. The approach could impact pass-fail judgements for the design. • Current approach to wind pressures and resulting ventilating flows is quite simplistic. Often complex, particularly when using non- standard openings. • Heat flow through glazing can also be complex. The way that the inside surface temperature is calculated may impact the room air flow characteristics. • Heat, air and moisture transport can be combined into one detailed assessment providing added insights. The Future Envelope 12 final event 20-21 May 2019, Bolzano
  25. 25. Thank you for your attention! www.interreg.net Prof Darren Woolf Hoare Lea / Loughborough University FACEcamp is funded by European Regional Development Fund and Interreg V-A Italy-Austria 2014-2020.

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