Re: [EnergyPlus_Support] Re: Indoor air temperature LOWER than ambient temperature

Jason

On Fri, Aug 17, 2012 at 8:39 AM, academicryan <azianzheep@xxxxxxxxx> wrote:

Hi Dr. Li,

Thank you for taking the time to reply me.

The ground temperature argument is a good one, however in my case the night time ambient is around 11-16C (and ground temp is constant at 18). Thus it cannot be due to this effect.

To clarify, you are right, ambient does mean outdoor dry bulb temperature.

please have a look at the file "glass_house.xlsx" in the Files section of this Yahoo Group. You will see what I mean. The inside temperature goes below the lowest night time temperature, which to me seems impossible in real life.

The simulation is of a glass house rather than a regular house, nevertheless this phenomenon is still against common logic and has occurred for me when I model regular houses as well.

Many thanks

Ryan

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> When you say ambient temperature, I assume that you are referring to the outdoor dry bulb temperature. The dew point has a lower temperature. The building surface ground may have a lower temerature, and assumed to be 18°C, if you did not not enter a set for the bulding. The radiation component always acts faster than the covection component. The exterior surfaces are facing the sky temperature, which is also lower than the ODT..
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> The ODT is usually the lowest at around 5 am. The building will follow this with a delay. Therefore, there are many possiblilities. After sun rise, the indoor temerature can still be lower, because of ground cooling through the floor. So list the variable for floor temperature ro confirm. If it is due to the low building surface ground temperature (18°C), increasing the temperature will raise the indoor temperature by a similar amount.. Dr. Li
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: azianzheep@...
> Date: Fri, 17 Aug 2012 07:47:37 +0000
> Subject: [EnergyPlus_Support] Indoor air temperature LOWER than ambient temperature

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> Hi
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> I've been doing E+ simulation for over half a year now and feel like I have a good grasp of it. But one thing I can't figure out is why I sometimes get results of indoor temperature being lower than ambient temperature. This often occurs during the early morning, 3am-9am. In reality this is impossible so I'm very confused by this result.
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> Can someone please explain to me why E+ produces this result?
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> If requested, I can attach additional information such as .idf or excel graph.
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> Many thanks,
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> Ryan
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--
Jason Quinn
Lead Engineer
Sustainable Engineering Ltd.
82 Liverpool Street
Wanganui 4500
New Zealand

+64 21 1846 911