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SUMMARY:Unbalanced exchange flow and the natural ventilation of buildings 
 - Nick Wise\, CUED
DTSTART:20211119T123000Z
DTEND:20211119T133000Z
UID:TALK166357@talks.cam.ac.uk
CONTACT:99736
DESCRIPTION:The natural ventilation of buildings at night is an essential 
 part of a low-energy ventilation and cooling strategy\, allowing excess he
 at to be purged and replaced with cooler night air. Instrumental to the su
 ccess of such ventilation schemes is the ability to predict flow patterns 
 and flow rates\, based on the size and location of ventilation openings. A
  common choice is to position openings at high and low level in the buildi
 ng fabric with the intention of setting up a buoyancy-driven displacement 
 flow\, where warm air exhausts through the high-level opening and cool air
  enters through the low-level opening. However\, we show that displacement
  flow cannot be maintained throughout a purge. Instead\, the flow pattern 
 must transition to ‘unbalanced exchange flow’\, whereby the inflow of 
 cool air at low level is maintained but there is now simultaneous inflow a
 nd outflow of warm and cool air at the high-level opening. This change in 
 flow pattern alters the internal distribution of heat and the resulting fl
 ow rates and purging times. We develop a theoretical model that captures a
 nd predicts this behaviour\, successfully predicting the transition and su
 bsequent flow rates\, then consider the implications for the design of nat
 ural ventilation systems.
LOCATION:CUED\, LR3A
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