[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

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



The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/