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[EnergyPlus_Support] Re: Small School - Modelling Simple Heating and Ventilation Equipment

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Small School - Modelling Simple Heating and Ventilation Equipment
From: "yangchen19851226" <yangchen19851226@xxxxxxxxxxxx>
Date: Thu, 10 Sep 2009 16:06:31 -0000
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Dear Richard,
     I understand your explanation about 100% fresh air.I have read both document you mentioned.I plan to combine unit ventilator and fan coil system to serve the zone.Here I have two questions.
     1)I have set up unit ventilator and fan coil system seperately,how can i combine them?Is it feasible to use controlled zone configuration to combine two supply air node into the same zone?
     2)You said if the supply air flow rate of unit ventilator equals to the OA flow rate, the unit ventilator will use 100% fresh air, but it still puzzles me that i can't find "supply air flow rate"
object in idf file?

Regards










--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> The unit ventilator has it's own mixing box (unlike the air loop systems 
> which have an OA Mixer and OA controller). If you specify that the 
> outdoor air is the same as the supply air flow rate, then you will bring 
> in 100% outdoor air. The exhaust air is always the same amount as the 
> outdoor air. 100% fresh air simply means there will be no recirculation 
> (return) air from the zone. All the air will come from outdoors and this 
> same amount will be exhausted through the unit ventilators mixing box 
> relief node. See the documentation for Unit Ventilator in both the Input 
> Output Reference and the Engineering Reference.
> 
> yangchen19851226 wrote:
> >  
> >
> > Thanks for reply.But I don't know what's the meaning of the system use 
> > 100% fresh air.Does it mean there is no exhaust air,if so, how to do?
> > Looking for your reply.
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Richard Raustad 
> > <RRaustad@> wrote:
> > >
> > > Look at the UnitVentilator object. Changing the max OA input should
> > > change the amount of OA compared to the supply air flow rate. You can
> > > also use schedules to vary the min/max OA during the simulation.
> > >
> > > ZoneHVAC:UnitVentilator,
> > > Zone1UnitVent, !- Name
> > > UnitVentAvailability, !- Availability Schedule Name
> > > 1.3, !- Maximum Supply Air Flow Rate {m3/s}
> > > FixedAmount, !- Outdoor Air Control Type
> > > 0.4, !- Minimum Outdoor Air Flow Rate {m3/s}
> > > UnitVentMinOA, !- Minimum Outdoor Air Schedule Name
> > > 0.4, !- Maximum Outdoor Air Flow Rate {m3/s}
> > > UnitVentMaxOA, !- Maximum Outdoor Air Fraction or Temp
> > >
> > > yangchen19851226 wrote:
> > > >
> > > >
> > > > I am puzzled about that the unit ventilator's outside air flow rate
> > > > equals the zone supply air flow rate (sum both zones).How to set in
> > > > idf file?
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "Richard Raustad"
> > > > <RRaustad@> wrote:
> > > > >
> > > > > The system you describe will not control to a 20C supply air
> > > > > temperature. You should be using an air primary loop with a HW
> > > > > heating coil controlled to 20C (Set Point Manager:Scheduled and
> > > > > Controller:Simple). See example file 5ZoneWarmest. The zone 
> > radiators
> > > > > will trim the zone temperatures. The unit ventilator is zone
> > > > > equipment, it is not used in an air primary loop. The unit 
> > ventilator
> > > > > is controlled by a thermostat and connects at the zone level (zone
> > > > > exhaust and zone inlet nodes). I would be surprised if were able to
> > > > > connect this to more than 1 zone without seeing node connection
> > > > > errors.
> > > > >
> > > > > Even though I recommend you change system type, I will try to answer
> > > > > your questions.
> > > > >
> > > > > 1) The preheat temperature defines the temperature of air leaving a
> > > > > preheat coil in the outside air system. This is the air temperature
> > > > > that will be sent to the heating coil for sizing. If return air is
> > > > > mixed, it will be mixed with this preheated air to calculate the air
> > > > > temperature entering the heating coil. If there is no preheat 
> > coil in
> > > > > the outside air system, this field will not be used. You will still
> > > > > have to define a hot water coil for the unit ventilator. You 
> > will not
> > > > > use this field for your input file.
> > > > >
> > > > > 2) The unit ventilator does not use a Controller:Outside Air object.
> > > > > But you will need one if you switch to using an Air Primary Loop
> > > > > object. You would then need Outside Air System and Outside Air Mixer
> > > > > objects also.
> > > > >
> > > > > 3) Report the air node flow rates in each zone, Return, Supply and
> > > > > Exhaust. Also report the outside air and relief node flow rates for
> > > > > each unit ventilator. Make sure the unit ventilator's relief air 
> > flow
> > > > > rate equals the total zone exhaust air flow rate (sum both zones).
> > > > > Also make sure the unit ventilator's outside air flow rate 
> > equals the
> > > > > zone supply air flow rate (sum both zones).
> > > > >
> > > > > 4) You do not have to actually simulate the exhaust fans. You 
> > can use
> > > > > electric equipment and gas equipment objects to simulate the energy
> > > > > use. I think you would set the Fraction Lost to 1 for these objects
> > > > > to only simulate energy use.
> > > > >
> > > > > 5/6) You do not need a set point manager for the outside air system.
> > > > > You would use a Set Point Manager:Scheduled (85C) for the hot water
> > > > > loop temperature.
> > > > >
> > > > > 7) The unit ventilators and OA systems do not require controllers.
> > > > > See the UnitVent5Zone exmample file for additional help.
> > > > >
> > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>
> > > > <mailto:EnergyPlus_Support%40yahoogroups.com>, "brandao_nuno"
> > > > > <ncostab@> wrote:
> > > > > >
> > > > > > I´m reposting my two previous posts hoping to get any help I can
> > > > > get.
> > > > > > I'm really desperate for some help here!
> > > > > >
> > > > > > Thanks in advance
> > > > > > Nuno Brandão
> > > > > >
> > > > > > -------------------------------------------------------
> > > > > > > Dear Group Supporters,
> > > > > > >
> > > > > > > I´m simulating a small school, with 4 controlled zones. All the
> > > > > zones
> > > > > > > are equipped with radiators. Two unit ventilators equiped with
> > > > > heating
> > > > > > > coils, supply air, each one supplying air to a group of two
> > > > > zones. The
> > > > > > > system is suppose to maintain the 4 controlled zones to a
> > > > > setpoint of
> > > > > > > 20ºC, so outside air is preheated to 20ºC by the ventilator's
> > > > > heating
> > > > > > > coil, and injected at that temperature into the zones. The
> > > > > radiators
> > > > > > > are responsible for the final heating requirement adjustments,
> > > > > > > although they have priority. The building has no cooling
> > > > > requirements.
> > > > > > >
> > > > > > > The system is only functioning during occupancy hours with a 
> > 20ºC
> > > > > > > setpoint. It turns on when the temperature is below 20ºC and
> > > > > turns off
> > > > > > > if the temperature is above that value. Uses 100% outside 
> > air and
> > > > > it
> > > > > > > is not recirculated.
> > > > > > >
> > > > > > > I've introduced the system in order to get the autosizing
> > > > > results, but
> > > > > > > I´m having hard time to figure out the excessive boiler 
> > autosized
> > > > > > > capacity obtained from the "Report:Table".
> > > > > > >
> > > > > > > I´m expecting for an anual simulation:
> > > > > > >
> > > > > > > - Boiler capacity - 30 KW
> > > > > > > - HVAC EnergyConsumption - 23626 KWh
> > > > > > > - Miscellaneous Equipment Energy Consumption(including lights,
> > > > > > > gas and electric equipment) - 51027 kWh
> > > > > > >
> > > > > > > However, I´m obtaining exaggerated high values. I suspect the
> > > > > problem
> > > > > > > is related to "System Control" and "Zone Sizing" issues, which I
> > > > > still
> > > > > > > don´t quite understand. My questions are as follow:
> > > > > > >
> > > > > > > 1. In the system sizing objects, what does the field "preheat
> > > > > design
> > > > > > > temperature" stands for? The I/O reference definition says that
> > > > > it is
> > > > > > > "The design air temperature exiting the preheat coil(if any)".
> > > > > > > In my specific case, to obtain the heating coil capacity is it
> > > > > enough
> > > > > > > to specify an exit temperature in this field, or do I still have
> > > > > to
> > > > > > > define a COIl:WATER:SIMPLEHEATING object? If it refers to 
> > another
> > > > > > > preheat coil, do I still have to specify a temperature even 
> > if the
> > > > > > > coil does not exist?
> > > > > > >
> > > > > > > 2. As described above, the system uses 100% outside air with no
> > > > > > > recirculation. Do I still have to specify a "CONTROLLER:OUTSIDE
> > > > > AIR"?
> > > > > > >
> > > > > > > 3. How do I guarantee, that the system uses only 100% outside
> > > > > air?
> > > > > > >
> > > > > > > 4. Air is exhausted from the building by exhaust fans 
> > located in 3
> > > > > > > zones. I need to account for the fan´s and kitchen gas equipment
> > > > > > > energy consumption, in the total building energy consumption
> > > > > internal
> > > > > > > gains from both equipments are ignored since I do not need to
> > > > > estimate
> > > > > > > zone loads or equipment size). Do I have to define a FAN object
> > > > > for
> > > > > > > each ventilator, or is it enough to use the "ELECTRIC EQUIPMENT"
> > > > > and
> > > > > > > "GAS EQUIPMENT" objects with an "ALWAYS OFF" schedule in 
> > order to
> > > > > > > ignore heat gains?
> > > > > > >
> > > > > > > 5.If the inlet/outlet boiler temperatures are 85/70, and the
> > > > > sizing is
> > > > > > > done by using the design day "Maximum Dry-Bulb Temperature" 
> > which
> > > > > > > temperatures do I need to specify at the "Set point at outside
> > > > > > > low/high" and "Outside low/high" fields from the "SET POINT
> > > > > > > MANGER:OUTSIDE AIR"? In I/O reference, the supply air set point
> > > > > > > temperature at outside high(SATOH) for example, is described 
> > as an
> > > > > > > outside air temperature, can it be a water supply loop
> > > > > temperature?
> > > > > > >
> > > > > > > 6. If the inlet air at the "MIXED AIR BOX" is only outside air
> > > > > with no
> > > > > > > zone recirculated air, do I need a "SET POINT MANAGER:OUTSIDE
> > > > > AIR"? I
> > > > > > > use a "SET POINT MAANGER:OUTSIDE AIR" to control the hot water
> > > > > loop
> > > > > > > flow and a "SET POINT MANAGER:SCHEDULED" to control the both air
> > > > > loops
> > > > > > > air outlet temperatures, is this procedure correct? If not, how
> > > > > do I
> > > > > > > control the heating coil flow in order to meet the heat demand?
> > > > > > >
> > > > > > > 7. I´m using one controller for each AIR LOOP, and one for each
> > > > > > > HEATING COIL, this assures the air control and the water 
> > control,
> > > > > is
> > > > > > > this right?
> > > > > > >
> > > > > > > I´m having hard time to understand how and what do I need to
> > > > > specify,
> > > > > > > to model system control procedures in EnergyPlus.
> > > > > > > I would appreciate any help I can get. I´m uploading my idf file
> > > > > so
> > > > > > > that you can have a look at it if necessary.
> > > > > > >
> > > > > > > Thank you for your patience.
> > > > > > > Nuno Brandão
> > > > > > >
> > > > > >
> > > > >
> > > >
> > > >
> > >
> > > --
> > > Richard A. Raustad
> > > Senior Research Engineer
> > > Florida Solar Energy Center
> > > University of Central Florida
> > > 1679 Clearlake Road
> > > Cocoa, FL 32922-5703
> > > Phone: (321) 638-1454
> > > Fax: (321) 638-1439 or 1010
> > > Visit our web site at: http://www.fsec.ucf.edu <http://www.fsec.ucf.edu>
> > >
> > > UCF - From Promise to Prominence: Celebrating 40 Years
> > >
> >
> > 
> 
> -- 
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL  32922-5703
> Phone:   (321) 638-1454
> Fax:     (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
> 
> UCF - From Promise to Prominence: Celebrating 40 Years
>




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- Re: [EnergyPlus_Support] Re: Small School - Modelling Simple Heating and Ventilation Equipment
  - From: Richard Raustad

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