[EnergyPlus_Support] Re: Ground temperature of Singapore

["academicryan" <azianzheep@xxxxxxxxx>]

Thanks Joe and Linda for your help so far.

Joe - yes I noticed there is a time lag and it increases with depth. 

Joe and Linda - OK great, both of you have given me the same solution: use the Slab program and use an appropriate indoor temperature. I can imagine this working as intended if there was a constant HVAC thus I would know the indoor temperature to put in. 

The problem is I'm simulating a building with no HVAC and a concrete ground floor. This means the ground temperature has a huge effect on the indoor temperature. In this scenario, how would you decide what indoor temperature to put into the Slab? 

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie  wrote:
>
> If you don't enter the indoor temperature, you will likely have 
> unrealistic results.
> 
> You have not given your problem to the helpdesk == this is a user=user 
> forum.
> 
> Rule of thumb - make your ground temperature -2C from your indoor 
> temperature.  I believe this is stated in the aux programs document if 
> you choose not to believe the calculations from the slab program.
> 
> 
> On 2013-01-18 19:32, academicryan wrote:
> > Hi Linda I have read that section at least 4 time trying to
> > understand it. I still don't really understand it very well but I'm
> > pretty sure its simply telling me to use the Slab program in the
> > EnergyPlus Utilities.
> >
> > I've mentioned that the Slab program gives unrealistic results. What
> > I particularly don't understand about the Slab is why there is an
> > input for monthly averaged indoor temperature. This means I need the
> > indoor temperature to calculate the ground temperature. But to
> > simulate the indoor temperature, I need the ground temperature. This
> > seems like an impossible chicken/egg scenario of which one comes
> > first. I've even read somewhere I'm supposed to start with an
> > arbitrary indoor temperature and keep doing this chicken/egg cycle
> > until both ground and indoor temperatures converge and stabilise. 
> > This
> > seems really silly and tedious but maybe that really is what I'm
> > supposed to do?
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Linda Lawrie  wrote:
> >>
> >> Read the auxiliary programs document on Ground heat transfer with
> >> EnergyPlus.  Look at the EPW file ground temperatures as well (which 
> >> are
> >> not suggested for the Site:groundTemperatures values)
> >>
> >> On 2013-01-18 18:49, academicryan wrote:
> >> > Update: *EnergyPlus developer please respond*
> >> >
> >> > OK I now know how to calculate soil temperature as a function of
> >> > depth from Hillel, 1982.
> >> >
> >> > Essentially his equation says that at 0 m depth, monthly average 
> >> soil
> >> > temperature is the monthly average air temperature plus 1�°C. This 
> >> is
> >> > basically a sine wave. With increasing depth, the soil temperature
> >> > gets closer to the annual mean air temperature plus 1�°C.
> >> >
> >> > NEW QUESTION: Is this what 
> >> 'Site:GroundTemperature:BuildingSurface'
> >> > wants? i.e. 0 m depth soil temperature. Or some other depth? Or 
> >> some
> >> > other 'ground temperature' altogether?
> >> >
> >> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "academicryan"  wrote:
> >> >>
> >> >> Can somebody please help me do a very simple task.
> >> >>
> >> >> Calculate/find the monthly ground temperature for Singapore. To
> >> >> clarify, this is the input for the
> >> >> 'Site:GroundTemperature:BuildingSurface'.
> >> >>
> >> >> ------
> >> >>
> >> >> Extra info - I've already tried the Slab utility, it comes up 
> >> with
> >> >> very unbelievable results. Calculating some months below 17�°C 
> >> when
> >> >> Singapore air temperatures never drops below 21�°C.
> >> >>
> >> >
> >> >
> >> >
> >> > ------------------------------------
> >> >
> >> > Primary EnergyPlus support is found at:
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> >> >
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> >> under
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> >> >
> >> >
> >>
> >
> >
> >
> >
> > ------------------------------------
> >
> > Primary EnergyPlus support is found at:
> > http://energyplus.helpserve.com or send a message to 
> > energyplus-support@...
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
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> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are currently allowed but be mindful that not everyone
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> >
> > EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under
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> > Yahoo! Groups Links
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> >
> >
>



------------------------------------

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