[Bldg-sim] Radiant slab Heating Cooling

[varun kulkarni]

Thanks Peter,

I am using Carrier HAP and when I model a fan coil unit, I am asked to
input the design supply temperatures for heating and cooling (which is
usually 95F and 55F). Now, i think these are going to drive my energy
consumed at the boiler and chiller. The whole point (not the only point but
a major though) of using radiant slab heating and cooling is lower temps
for heating, higher temps for cooling and also the fact that water has
higher energy carrying capacity then air. So if you are not able to take
credit for that in modeling then obviously, the energy consumption number
is not right. Thats my reason to segregate the different temperatures.

On Thu, Feb 23, 2012 at 11:38 AM, Peter Simmonds
<peter.simmonds at ibece.net>wrote:

>  Varun, your perception is nearly true, but it depends on what you are
> modeling? If you are modeling the energy performance of a building a four
> pipe fan coil works just fine as it maintains the required energy balance.
> It is true that the actual performance of a radiant floor is different than
> a fan coil, but you are looking at energy and not optimal modeling.****
>
> Your thoughts on stratification are somewhat correct. I would tend to
> think that stratification is caused by space heat load and air movement,
> especially displacement. Yes, there is a convective flow from the floor but
> this is quite small as the temperature difference between the floor surface
> temperature and the space operating temperature.****
>
> Regarding temperature; this depends on what program you are using and why
> you want to segregate the different temperatures?****
>
> ** **
>
> *Peter Simmonds, Ph.D. *
> *Senior Associate
> Head of the Advanced Technology Group
> **IBE Consulting Engineers*
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> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *varun kulkarni
> *Sent:* Thursday, February 23, 2012 5:34 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Radiant slab Heating Cooling****
>
> ** **
>
> Good Morning everyone,****
>
>  ****
>
> I have been reading through the archives for modeling radiant slab heating
> and cooling.****
>
> Most popular and the closest to real world approach I found was using a 4
> pipe fan coil unit and making the fan energy zero.****
>
> I still have following questions:****
>
> ·         Did anyone think of using a factor, which when multiplied to
> the energy usage by fan coil system, give us the actual energy usage by
> radiant system. (I would guess it would be <1)****
>
> ·         As radiant heating and cooling forms a stratification layer in
> the space. And  we care about first 6-8 feet to be within desired
> temperature range. So to take that into account while modeling “it”  as fan
> coil unit, can we lower the ceiling height. Does that mean the conduction
> load from ceiling/roof or the wall above 6-8 feet doesn’t count ?****
>
> ·         The temperature range for heating water (95F-105F) and cooling
> water (55F-65F) pumped in the radiant system is different from the typical
> chilled water (44F-45F) and heating water (170F-180F). How do we make sure
> our model reflects this while using fan coil unit.****
>
>  ****
>
> I am sure there are more questions you would have come across but these
> were some of my major concerns and I would appreciate any inputs/
> suggestions.****
>
> PS: This is a aspiring LEED platinum building.****
>
>
>
> -- ****
>
> Thanks and Best Regards,****
>
>  ****
>
>  ****
>
>  ****
>
> Sincerely,****
>
>  ****
>
> Varun Kulkarni ****
>
>  ****
>
> Note: Please do not print, unless required.****
>
>  ****
>
>  ****
>
> ** **
>



-- 
Thanks and Best Regards,



Sincerely,

Varun Kulkarni

Note: Please do not print, unless required.
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