Re: [EnergyPlus_Support] UCSD DISPLACEMENT VENTILATION MODEL

[Philip Haves <phaves@xxxxxxx>]

The warning message indicates that the difference in height between the highest and lowest vertices of the surfaces
surrounding the zone differs from the Ceiling Height specified in the Zone object by more than 0.1m.  Possible explanations
are:

1. The coordinates of one or more surfaces have been entered incorrectly (check the Z values).
2. The Ceiling Height has not been set or has been set incorrectly
3. The space has a floor or ceiling that isn't level, so the maximum value of the floor-to-ceiling height differs from the
value that was entered as the zone Ceiling Height.

Note that the UCSD displacement ventilation model is only intended to treat spaces with level floors and ceilings.  The
effect of sloping floors or ceilings on the accuracy of the model hasn't been quantified but can reasonably be expected to
depend on the variation in floor-to-ceiling height.  My judgement is that a 10% variation in height is unlikely to affect the
accuracy of the model significantly but a 50% variation may well produce significant errors.  The model uses the maximum
height difference between floor and ceiling to calculate the behavoir of the plumes, so that plumes in parts of the space
where the floor-to-ceiling height is lower will be modeled incorrectly.  Since greater floor-to-ceiling height generally
produces better displacement ventilation performance, the modeling errors from sloping ceilings or floors will tend to
overestimate performance.

I'd like to hear from people who find this limitation a problem, so that we can assess the demand for a possible fix.

Philip Haves

daiounomiso wrote:

> I want to use UCSD DISPLACEMENT VENTILATION MODEL.
> The following message is given.
>
> ** Warning ** Inconsistent ceiling heights in Zone
>
> What does this message mean?
> What input should I modify?
>
> Thanks.
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
>
> Yahoo! Groups Links
>
>
>
>

--
Philip Haves
Leader, Commercial Building Systems Group
Lawrence Berkeley National Laboratory, MS 90-3111
Berkeley, CA 94720
Tel: (510) 486 6512
Fax: (510) 486 4089




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