RE: RE: [EnergyPlus_Support] EnergyPlus Validation

["Michelle Smith" <MLSmith@xxxxxxxxxxxxxxxxxxxx>]

No, I haven't done any validation in the sense of specific conditions. I
typically will run similar models on different software tools to see how
they vary. The work I do doesn't require my answers to be so precise.

I guess I don't understand why you would see a change in room temperature
with the radiant body. How can the temperature change if nothing in the room
can absorb the energy and convect it back to the space? Mike Witte pointed
out the air is considered transparent in energyplus. The only heat transfer
by E+ should be the conduction across the walls.

I know this is all an academic exercise, but I'm just curious.

Michelle Smith
Belle Engineering, LLC
Ph: 314.631.8447
Fx: 314.631.9102
www.belleengineering.com

-----Original Message-----
From: alexander.beisteiner@xxxxxxxxxxxxxxxxxx
[mailto:alexander.beisteiner@xxxxxxxxxxxxxxxxxx]
Sent: Friday, October 25, 2002 10:48 AM
To: MLSmith@xxxxxxxxxxxxxxxxxxxx
Subject: Re: RE: [EnergyPlus_Support] EnergyPlus Validation


Dear Mr. Smith
Thank you for your answer. The reason I am simulating non-real conditions is
because I want to validate the software according the German VDI 6020
directive. I am aware of the basics of heat transfer, but the question is
why the same load (either convective or radiant) in that specific example
produces different equilibrium conditions. The only difference might be in
the temperature trend in the room: while the convecitve load heats up the
air quicker, the radiant causes a slower increase, but equilibrium
conditions must be the same.
By the way, have you ever validated E  with reference examples? I am looking
for people who have done to discuss results.

Regards.

----------------------------------------------
Alexander Beisteiner
Forschungs- und Technologietransfer
Pinkafeld GmbH
Steinamangerstrasse 21
7423 Pinkafeld

Tel.: 0043/3357/45370-1324
alexander.beisteiner@xxxxxxxxxxxxxxxxxx
http://www.fh-pinkafeld.ac.at

I would just like to point out, while the test is very interesting on a
theoretical level, the conditions you are simulating do not exist in the
real world.

Since your walls have an absorption of zero (I am assuming a radiant
absorption), they must have a reflectance of one. Or 100f the radiant
energy is reflected back into the space, or more precisely, reflected back
to the air in the space which will be able to absorb it. The radiant source
heats the air, THEN the air will lose some heat to conduction to the walls.

With the convective source,  while it is convectively heating up the air,
the air is also transferring heat to the outside by conduction. Thus, the
air is constantly having both the convection from the source added, while
losing heat through conduction to the walls.

A basic text book on heat transfer will give you all the relevant equations
for each type of source.

Michelle Smith
Belle Engineering, LLC
Ph

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