This is a very frequent question on Zone mean temperature.
The anual simulation starts from 23°C, i brief, as any digital calculation requires some initial values. Therefore the first three days are the same, if they are all from Jan 1.
If the three days are from the middle of an anual simulation, the short three day one would not be the same. I usually run six or more days and compare the last three days.
The DesignDay simulation repeats a few times (second groups of warm up times) until the begining midnight and ending midnight value are the same. This implies that the previouday condition is the same as the current one. Therefore, if the building does not cool down at night, the temperature of the building would be higher in the morning.
A weather file simulation would look quite different, when the day is preceded by a cloudy raining day.
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When using operative temperature, the additional check on "shadowCalculation" would be required.
In the WinterDesignDay object, the skyclearance is normally set to zero.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: linda@xxxxxxxxxxxxxx
Date: Mon, 6 Feb 2012 08:09:12 -0700
Subject: Re: [EnergyPlus_Support] different results with different run periods?
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The anual simulation starts from 23°C, i brief, as any digital calculation requires some initial values. Therefore the first three days are the same, if they are all from Jan 1.
If the three days are from the middle of an anual simulation, the short three day one would not be the same. I usually run six or more days and compare the last three days.
The DesignDay simulation repeats a few times (second groups of warm up times) until the begining midnight and ending midnight value are the same. This implies that the previouday condition is the same as the current one. Therefore, if the building does not cool down at night, the temperature of the building would be higher in the morning.
A weather file simulation would look quite different, when the day is preceded by a cloudy raining day.
=====================
When using operative temperature, the additional check on "shadowCalculation" would be required.
In the WinterDesignDay object, the skyclearance is normally set to zero.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: linda@xxxxxxxxxxxxxx
Date: Mon, 6 Feb 2012 08:09:12 -0700
Subject: Re: [EnergyPlus_Support] different results with different run periods?
Make sure that you have the "ShadowCalculation" in
both runs set to 1.
How far off are they? Are your zones being controlled? There is some influence of warmup days -- are they the same for both and passing convergence?
At 08:03 AM 2/6/2012, amyquartette wrote:
How far off are they? Are your zones being controlled? There is some influence of warmup days -- are they the same for both and passing convergence?
At 08:03 AM 2/6/2012, amyquartette wrote:
dear all,
I have run an annual simulation of my e+ file for the operative temperatur of a zone. Then I ran with the same file with a run period which has only 3 days. The results of the operative temperaturs for the 3 days of the 2 simulations are not the same.
Could someone explain the reason and tell what I should be aware of?
Thank you very much!
Regard,
Amy
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