[Bldg-sim] wetbulb formula

[Dr. Nader Chalfoun]

Alec:

In the past, I wrote two programs in Turbo Pascal that calculates
thermal properties of moist air based on ASHRAE equations.  They are
called PSY and PSY2.  PSY2 takes values of Dry-bulb and Relative
Humidity under a particular pressure condition (in.Hg) and returns all
properties of that air including Relative Humidity.

I will attempt to send this PSY2.exe file but our university email
system blocks any .exe files from being sent over their system.  So I
will remove the .exe from the file and you can re-name it later.  You
can also try to unzip the attached PSY2.exe file.

If it doesn't work, let me know, and I will send it through other email
accounts to you directly.  You may also try to download it from my
website: http://houseenergydoctor.arizona.edu


Nader

Check my new online energy courses
http://www.hed-online.com

--------------------------------------------
Nader V. Chalfoun, Ph.D., LEED AP, CEA
Professor of Architecture and Environmental Sciences
Director: The House Energy Doctor Program
http://houseenergydoctor.arizona.edu
Chair: Graduate Masters Program on "Design and Energy Conservation"
Coordinator: Environmental Education Ph.D. Minor
Faculty on Global Change Ph.D. Minor

Address:
University of Arizona
College of Architecture and Landscape Architecture
1040 N. Olive St., Tucson, AZ 85721, U.S.A.
Phone: (520)621-6751    Fax: (520)621-8700


Quoting R B <slv3sat at gmail.com>:

> You should be able to find these routines in the HVAC Toolkit book - sold by
> ashrae. I don't have it handy so not sure if you can use the routine
> directly in excel - you might need visual basic. I have done this previously
> in matlab, C++
> -Rohini
>
> On Thu, Dec 9, 2010 at 4:43 PM, Alec Stevens <astevens at dmiinc.com> wrote:
>
>> Hi,
>>
>> Does anyone have an Excel-friendly equation they would be willing to share
>> that can convert Tdb and RH into Twb?  We have metered data giving us Tdb,
>> RH, and Tdp, but we need to know wetbulb.  We usually solve this problem
>> with an Excel psychrometric add-in, but we need to distribute this
>> spreadsheet to a client and cannot distribute the add-in at the same time.
>>
>>
>>
>> We've tried a couple of multivariable regressions on the data, but because
>> it is nonlinear, it is not proving to be that straightforward.  Next stop
>> might be a two-way lookup table, but that is kind of cumbersome and was
>> hoping to avoid it.
>>
>>
>>
>> Any help much appreciated.
>>
>>
>>
>> Sincerely,
>> Alec Stevens
>>
>>
>>
>> DMI
>> 35 Walnut Street, Wellesley, MA 02481
>> p: 781 431 1100 x11   f:781 431 1109
>> e: astevens at dmiinc.com
>>
>>
>>
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>
>
> --
> --------------------------------------------------------------------------------
> Rohini Brahme, Ph.D. LEED AP
> Building energy analysis, tool development, and training
> Dallas/Fort Worth, TX


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