Re: [EnergyPlus_Support] Fractions to surfaces for ZoneHVAC:HighTemperatureRadiant

["Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

That makes it a bit harder. The conservative approach would be to start at zero % People 100% Floor. Over time radiation exchange to other surfaces will give a MRT and the operative temp will be the ave. of MRT and air temp.

The other route envolves knowing exactly where the human(s) will stand (sit), simplification of their surface geometry to some combination of horizontal and vertical plates and doing some basic view factor calcs regarding the radiation exchange with respect to your radiant device.

I always imagine the polititions like this as having rectangular plates for heads. It makes what they say seem more fitting.

And a happy 2018 for you too!

PS I think the DB CFD tool is quite nice for these kind of comfort analysis investigations.

Am 02.01.2018 5:43 nachm. schrieb "Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>:

 

Thanks, Ned.

You are exactly right that comfort is the driver of this particular model. My goal is to get that reasonably right and see what energy is consumed.

On Mon, Jan 1, 2018 at 8:54 AM, 'Edward G. Lyon' eglyon@xxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@yahoogroups.com> wrote:

 

I have had similar concerns with the radiant fraction of radiators, especially modeling older steam systems.  The last radiant panels I modeled (predate this radiant heater object) were actual surfaces in the model and the radiant distribution was calculated automatically.  The object you are modeling is a heater, often found in big box stores over cashiers near the outside doors.  The devices produce a focused radiant heat, so you have to decide how to split the output.  All the output is somehow integrated into the room.  The only reason to attribute any to people is if you were performing a human comfort calculation.  Anything radiated to people eventually goes to the room, but it affects the comfort perception of the occupant.  To calculate the occupant fraction, you need to calculate how much of the total radiant area is occupied by a body, so you need to know something about the focus of the device and the occupancy.  Similarly, if the radiant is focused onto an exterior wall, you would get more heat loss from your building because the surface conduction would have a radiant increase.

 

Staying warm by the fire?lotss of radiant heat in a cold house?

 

Ned Lyon, P.E. (MA, WV)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
617.285.2162 mobile 
781.907.9009 fax
www.sgh.com

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From: EnergyPlus_Support@yahoogroups.com [mailto:EnergyPlus_Support@yahoogroups.com]
Sent: Friday, December 29, 2017 4:17 PM
To: EnergyPlus_Support@yahoogroups.com
Subject: [EnergyPlus_Support] Fractions to surfaces for ZoneHVAC:HighTemperatureRadiant

 

 

Dear Forum,

 

I am using the ZoneHVAC:HighTemperatureRadiant object in a model and am trying to double check the fraction of radiant energy that I'm assigning to:

• People
• Walls
• Floor

At the moment (and largely using values from an example file), I'm assigning 5% to people, and the remainder to the floor.

 

Do any of you who are familiar with this object have recommendations regarding how to assign those radiant fractions?

 

Thanks in advance. Happy New Year, too!

 

--

James V Dirkes II, CEO / President
The Building Performance Team Inc..
1631 Acacia Dr, Grand Rapids, MI 49504

 

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450...8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxm

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Coffee conversation:

My opinion and experience:

The gospel of Jesus is without doubt the most beautiful world view on our planet.

--

James V Dirkes II, CEO / President
The Building Performance Team Inc.
1631 Acacia Dr, Grand Rapids, MI 49504

(alphabet soup of efforts for greater understanding: PE, BEMP, BCxP, LEED AP)

Direct / Mobile: 616.450.8653
jim@buildingperformanceteam.com

Website l  LinkedIn

Coffee conversation:
My opinion and experience: 
The gospel of Jesus is without doubt the most beautiful world view on our planet. 

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---

Posted by: Jean Marais <jeannieboef@xxxxxxxxx>

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