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RE: [EnergyPlus_Support] Direct Air Heating help





I have looked your draft document.  You have chosen to create an IDF using IDFeditor from scratch.
 
What you should do is to look at the example and decide on what you wanted to do.
 
If you simply remove one TSC from the ZN11 to ZN15 group, you have have one zone with TSC and one zone without.  Simply ignore the result for the SUmmer, the job is done.
 
You can then change another zone for a window and another with window with blind.  One simulation will give you four different options.


There is no harm leaving the DX cooling coil in the system.  As there are five of them in the example, you can simply remove one by delete them in the IDFeditor or using a text editor.  Because yu are simulating all the options at one time, they are very easy to compare.
 
You can move the columns on the spreadsheet, or use the .rvi post processor to re-format the csv file, using the .eso file already exist after a simulation, provided that all the required variables are in the IDF.


The variables you are monitoring are not so useful, as they are all energy values which changes with simulation timestep period.  Use the rate in watts.
 
You can compare the exterior wall temperature with and without the TSC.  This is the main factor determining the change in zone energy demand. 
 
Air loop total includes all the equipment losses.  In your case, there is ony one zone per loop.  The value would be close to the zone demand.  Because you do not have two zones simulated at the same time, you need to combine results from two runs to compare.
 
Zone sensible heating energy does not include the component due to humidity change.
 
Most of these values for a larger time period are averaged values.  You do not really get the feel of the changes as they are occurring.  List in timestep intervals, not in hourly averaged values.


If you are using the OA mixer, the fan rate is the air loop circulation rate.  If you made the OA inlet rate the same as fan  rate, no return air is mixed with the inlet and relieved.  3 m/s is the air velocity limit  for noise consideration.  3m3/s would need an opening larger than 1m2.  As you have a large wall, this may not be a problem, until you reach the by-pass duct end.  3m3/s does not fully descibe the capacity. Temperature, convection coefficient, etc must also be considered.
 
Direct air was used for a damper unit, (now ATU uncontrolled.)  A zone is connected to the air duct via a direct air unit.  It may have other meaning.
 
When you use these three component to control one zone, it may be called a zone unit.
 
When they are used to feed more then one zone, then it is called  AHU system.  The operation is the same.
 
During Summer time  the natural zone temperature may be lower than the ODT at some time in a day.    If the setpoint is still active and heating is available, it will be used to compensate.  If heating is not available, the demand may still reported.
 
Don't forget that the TSC will heat, when the sun is there.  It will not heat at night.  Therefore, a storage system is more efficient.
 
 Dr. Li  

 
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: mumcuece@xxxxxxxxx
> Date: Thu, 16 Aug 2012 21:44:02 +0000
> Subject: [EnergyPlus_Support] Direct Air Heating help
>
>
> Dear people,
>
> I formed an airloop which has just one branch containing 3 component objects.
> 1.AirloopHvac:Outdoor Air system (outdoor air mixer)
> 2. Coil: Heating: Gas
> 3. Fan: Constantvolume
>
> and for the air terminal unit I used singleduct:uncontrolled. So It is a direct air heating system.
>
> For the min and max outdoor airflow rate I assigned 3 m3/sn to bypass recirculation in the mixing box. I want to supply 3 m3/sn outdoor fresh air ( in the ambient temperature) to the zone during the occupied hours and keep the zone temperature 18 C occupied hours. By having 3 for min and max outdoor air flow rate 3m3/sn and design supply air flow rate 3 m3/sn , I assume I exhaust the recirculation air do I ???
>
> On the other hand, is this system ok in terms of HVAC system??
>
> The outputs which I observe are direct air sensible heating energy
> Air loop total heating energy
> Zone sensible heating energy
> Air loop total coil heating energy
> Air loop fan heating energy
>
> From the I / O REFERENCE, Dï?¥RECT air sensible heating energy is " the heating energy provided to the zone by the uncontrolled gterminal unit
> But the zone/system sensible heating energy description is quite similar. However, I noticed one thing although my heating system
> does not work during july and august , there are small loads for these two months in direct air heating energy and zone system sensible energy outputs. How could it be ? and if I wanted to put a TSC ( which I want )and compare the both case which output is important for cooling reason .. or comparing the two situation is logical to find out how TSC affects the heating energy ?
>
>
> The aim is to provide this 3 m3/sn during the occupied hours ,heat it to maintain the zone described conditions except july and August.
>
>
> I hope I will have great help
> Thanks !!
>
>
>
>
>
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