Tutorial 4
Solving the Flow Equations
[See
Disclaimer and Important Notes]
Assuming a total of
‘j’ openings, the flow rate through each opening is solved by
determining the internal pressure of the space or (in the case of a
multi-zone building) each internal zone. This is determined by applying
the Law of Conservation of Mass (i.e. the mass of flow into the building
equals the mass of flow out or the sum of the flow equals zero). Thus the
mass balance equation (and volume flow approximation) for j flow paths is
given by:
These generally have to be
solved by ‘iteration’ using a model such as PHPAIDA.
The user must supply the pressure (due to stack and wind) for each flow
path and the flow coefficient and flow exponent for each path. This leaves
the internal pressure as the only unknown.
Direct solution is possible for very simple networks. Examples are given
in Tutorial 5.
This completes Tutorial 4
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