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Re: [EnergyPlus_Support] weird zone air temperature curve





Thank you Richard!

I have set the ZoneCapacitanceMultiplier to 10 and the graph is much more realistic now. However, I still do not fully understand what this multiplier does. Have I just hacked my model to force it to work as I would expect or was something wrong with the capacitance of the air in the volume of my zone?

Thanks again


From: Richard Raustad <RRaustad@xxxxxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Wed, 17 November, 2010 13:20:40
Subject: Re: [EnergyPlus_Support] weird zone air temperature curve

 

You might try changing the air capacitance. See this object (I believe new to V6):

ZoneCapacitanceMultiplier:ResearchSpecial,
10, !- Temperature Capacity Multiplier
10, !- Humidity Capacity Multiplier
1;   !- Carbon Dioxide Capacity Multiplier

Or, if using a previous version, a different air heat balance solution method (see documentation):

The default if this object is not present in the input file is ThirdOrderBackwardDifference which may be susceptible to very small simulation time steps (due to rapidly changing zone temp). You could try a method which is less susceptible to variations in simulation time step.
 
ZoneAirHeatBalanceAlgorithm, AnalyticalSolution;

or

ZoneAirHeatBalanceAlgorithm,EulerMethod;


On 11/17/2010 8:08 AM, cleef_lee wrote:

 

Hi,

I am using E+ with BCVTB to test heating control in domestic houses.
In order to validate the heating behaviour of a simple house with regular materials, I have built a simple 5m x 3m x 3m box house with an electric radiator (700W capacity) and no windows or doors or any kind of internal loads. The construction materials have values based on a BRE measured u-values report and more or less are average materials used in UK domestic houses.

I run the simulation in E+ for 5 days with outdoor temperature between
-4 and 9 degrees Celsius and the temperature graph was somehow weird. When the heating goes to ON the temperature initially increases rapidly (more than 1 degree per 3 minutes) and then increases with a slightly more expected way (1 degree per 20min). In a similar way when the heating gets to OFF the temperature initially decreases too quickly (1 degree in 3 minutes) and then the decrease rate gets a little bit smoother.

Do you have any idea why the temperature curve follows this positive or negative "logarithmic" form ?

Thank you very much!


-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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Fax:     (321) 638-1439 or 1010
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