[esp-r] Re: Bi-directional Airflow Component for Vertical Air Exchange

[Jeremy Cockroft]

The bi-directional flow component only works for openings in vertical surfaces between internal spaces.  It takes into account the combined effect of zone pressure differences and bouyancy caused by temperature differences.  It should not be applied to represent, e.g. an open window, because the external wind turbulence effects, which are likely to predominate, are not represented.  It is unlikely to give correct results for flow between arbitrarily defined nodes in a space (like an atrium) because the flow is not constrained to pass through a physical opening.  It certainly should not be used to represent a horizontal opening.

Jeremy
ESRU
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Jon Hand [jon at esru.strath.ac.uk]
Sent: 08 February 2010 07:49
To: Mostapha Sadeghipour; esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: Bi-directional Airflow Component for Vertical Air Exchange

The bi-directional component is based on experiments with doors and the equations
are specific to an opening in a vertical surface.  The quote about bi-directional
components in atria is in the context of side-to-side flow within the atria.

Vertical flow is usually represented by one of the single direction flow components.  Thus
to get two way flow we have to define two separate paths.  One approach is to create
a small vertical by-pass zone at one corner of an atria and connect be top and base so
that (cold down-drafts can be accommodated for example).  Perhaps it is time to
include an exemplar model which demonstrates sub-division of large spaces.

The ESP-r community would love to have a component that represented bi-directional flow
in horizontal openings.  Anyone know of one or has an interest in creating such a component?

-Jon Hand
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of Mostapha Sadeghipour [sadeghipour at gmail.com]
Sent: 07 February 2010 12:37
To: esp-r at lists.strath.ac.uk
Subject: [esp-r] Bi-directional Airflow Component for Vertical Air Exchange

Thank you Jon for your answer to my previous question. Here is the next question(s). :^)

I read several emails in esp-r 2006 emails archive related to using the bi-directional door component in horizontal surfaces for vertical air exchange (here<http://lists.strath.ac.uk/archives/esp-r/2006/subject.html>). Many posters stated that door component is defined for vertical surfaces and using this component in horizontal positions is out of theoretical scope of the model, and thus the result would be meaningless.

In contrary, the same idea is mentioned in Esp-r FAQs, under the fictious surfaces and zone subdivision<http://www.esru.strath.ac.uk/Programs/ESP-r_FAQ.htm#fictitious> as a suggestion:
"Occasionally it is necessary to divide a large space into several thermal zones. A typical example of this is an atrium or other high space with an air temperature gradient such that the perfectly mixed zone approach is not applicable...The flow across the opening as represented by this fictitious construction can be described by either scheduled air flows or by setting up a network flow (often a door component is a good choice to allow bi-directional flow)."

Then, which one is true? Use the bi-directional door component for vertical air exchange or not?

If the answer to the question 1 is "NO", then how to define a bi-directional component for vertical air exchange? Is there a bi-directional horizontal airflow component available now?

Thanks in advance,

Mostapha Sadeghipour

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