Joe
On 1/20/2013 11:08 AM, Joe Huang wrote:
Ryan has said that those previous runs with Slab were done with the default indoor temperatures which were very low (13C for winter, 18.3 for summer) and appropriate only for buildings in northern climates. Since the building is naturally ventilated, a more appropriate indoor temperature would be simply the outdoor air temperature, in which case you would probably see the same ground temperatures as on the weather file. Further iterations between E+ and Slab can be done, but that would definitely a 2nd or 3rd order effect.
Joe
On 1/19/2013 11:45 PM, jeannieboef wrote:
Your itteration approach is correct. I don't believe high accuracy is needed for the deltaT over the slab, as the small error is only impacting on a small chunk of energy transfer over the entire envelope. if the space above is conditioned this makes things easier.
Post an example of your unbelievable results. Corrispond them also with Dr. Li as he has practiced energy modelling in Singapore. You'll have to check some older posts for the contact details.
Sent from my iPhoneIf 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:
>> > http://energyplus.helpserve.com or send a message to
>> > energyplus-support@...
>> >
>> > The primary EnergyPlus web site is found at:
>> > http://www.energyplus.gov
>> >
>> > The group web site is:
>> > http://groups.yahoo.com/group/EnergyPlus_Support/
>> >
>> > Attachments are currently allowed but be mindful that not everyone
>> > has a high speed connection. Limit attachments to small files.
>> >
>> > EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf
>> under
>> > the Documentation link and press the "search" button.
>> > Yahoo! Groups Links
>> >
>> >
>> >
>>
>
>
>
>
> ------------------------------------
>
> Primary EnergyPlus support is found at:
> http://energyplus.helpserve.com or send a message to
> energyplus-support@xxxxxxxx
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are currently allowed but be mindful that not everyone
> has a high speed connection. Limit attachments to small files.
>
> EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under
> the Documentation link and press the "search" button.
> Yahoo! Groups Links
>
>
>
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