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RE: [EnergyPlus_Support] Comparable Comfort
Andy and Rory,
While the low temperature radiant system model in EnergyPlus is a valid
means of conditioning the space, the main disadvantage to using it for this
study is that it will affect the temperature of at least one surface in the
zone directly and other surfaces indirectly. As a result, I think using
the low temperature radiant system would not be of much help in what is
essentially a thermal physics study. This is not to say that it wouldn't
be appropriate in other cases.
However, it *may* be possible to trick the high temperature radiant heater
into serving the zone as a heating only system (no cooling would be
available--a potential drawback?). You can get the high temperature
radiant system to be 100% convective by assigning zero values to the fields
for fraction radiant, fraction latent, and fraction lost. Since one minus
the sum of these fractions is the fraction convective, this would serve to
make the high temperature radiant heater 100% convective. Not exactly the
point of that model (and the performance of the model has not been tested
at that limit yet), but it would allow you to heat the space based on
either MAT, MRT, or Operative Temperature (average of MRT and MAT). And it
would do it without affecting the surface temperatures within the
space. If this works, the main drawback is that it would not allow you to
cool the space.
I hope this helps and that you are able to model your situation with this
approach.
Rick Strand
EnergyPlus Development Team
At 08:58 AM 12/15/2005, you wrote:
>Is it possible to create a special surface located within each zone to house
>the low temperature radiators? This will avoid changing the heat transfer
>properties of existing surfaces but I don't have any experience using these
>low temperature radiant Systems and am hoping that someone who does could
>confirm that this is a viable approach. I am interested because I am
>considering implementing these systems in DesignBuilder.
>
>Andy
>DesignBuilder
>
>-----Original Message-----
>From: EnergyPlus_Support@xxxxxxxxxxxxxxx
>[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]On Behalf Of rorywalsh06
>Sent: 15 December 2005 14:40
>To: EnergyPlus_Support@xxxxxxxxxxxxxxx
>Subject: [EnergyPlus_Support] Comparable Comfort
>
>Rick and Andy
>
>Thanks for setting me on the right path.
>
>Originally I thought I would be able to investigate the effects of
>thermal mass without having to specify a heating/cooling system.
>However if specifying a system allows me to ensure similar comfort
>conditions are provided when different construction are used then I
>think this might be worth trying.
>
>The office buidlings I am looking at are heated using hot water
>which is supplied to large radiators from a gas boiler. I would like
>to specify a comparable system in energyplus.
>
>Base-board units would be a close match but "operative Temperature
>Control" is not available with this system.
>
>If I were to specify a low temperature hydronic system. I would have
>to associate it with a surface in the zone.I am worried that this
>might be too invasive.
>I really want to see how the internal surface temperatures of
>different constructions react, as a function of heating schedules,
>occupancy periods, internal gains, ventilation rates etc... Would
>embedding a heat generating system not result in a situation where
>my internal surface was driving internal air temperatures instead of
>reacting to them?
>Is there anyway I could implement this option without using any of
>the six surfaces which typically define a rectangular zone.
>
>Would a high temperature radiant system be more suitable as it does
>not need to be associated with a surface within the zone? Is there
>any way to include a convective contribution from this type of
>equipment?
>
>Look forward to your suggestions
>
>Thanks
>
>Rory
>
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>The primary EnergyPlus web site is found at:
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>Attachments are not allowed -- please post any files to the appropriate
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