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

[EnergyPlus_Support] Design coil load is zero



Hi all,

 

I?m trying to simulate a Constant Volume Air Handling Unit to control
temperature in a single zone. The AHU has a constant volume fan and a
cooling coil. Heating is provided by a terminal reheat coil.

To control the exit cooling coil air temperature I?ve defined a
controller:simple and a Set - point manager: Warmest to reset the cooling
coil air temperature.

To control zone temperature, I?ve defined a dual set-point with deadband
thermostat (heating set-point temperature 20ªC, cooling set-point
temperature 24ºC). 

 

The total air system and  outside air volumetric  flow rates are known. For
this reason, in the zone sizing object I?ve defined the cooling  and heating
design air flow method to ?flow/zone? and input the desired flow rates. I?ve
defined also the outside air flow rate.

 

ZONE SIZING,

    P1 - Sala_Cirurgia,      !- Name of a zone

    16,                      !- Zone cooling design supply air temperature
{C}

    25,                      !- Zone heating design supply air temperature
{C}

    0.008,                   !- Zone cooling design supply air humidity
ratio {kg-H2O/kg-air}

    0.008,                   !- Zone heating design supply air humidity
ratio {kg-H2O/kg-air}

    flow/zone,               !- outside air method

    0,                       !- outside air flow per person {m3/s}

    1.167,                   !- outside air flow per zone {m3/s}

    1,                       !- zone sizing factor

    flow/zone,               !- cooling design air flow method

    5.139,                   !- cooling design air flow rate {m3/s}

    flow/zone,               !- heating design air flow method

    5.139;                   !- heating design air flow rate {m3/s}

 

As I?ve read in the mailing list and in the EnergyPlus documentation, the
flow rates are sized on the sum of zone air flow rates. If I define
flow/zone method, design calculated flow rates are override. For this
reason,  I didn?t change the flow rate fields in the System Sizing to let
the program compute the flows I?ve entered in the zone sizing object.

 

SYSTEM SIZING,

    UTA_BO 2,                !- name of an AIR PRIMARY LOOP object

    sensible,                !- type of load to size on

    autosize,                !- Design (minimum) outside air volumetric flow
rate {m3/s}

    1,                       !- minimum system air flow ratio

    7,                       !- Preheat design set temperature {C}

    16,                      !- Central cooling design supply air
temperature {C}

    25,                      !- Central heating design supply air
temperature {C}

    noncoincident,           !- Sizing Option

    no,                      !- Cooling 100% Outside Air

    no,                      !- Heating 100% Outside Air

    0.008,                   !- Central cooling design supply air humidity
ratio {kg-H2O/kg-air}

    0.008,                   !- Central heating design supply air humidity
ratio {kg-H2O/kg-air}

    design day,              !- cooling design air flow method

    ,                        !- cooling design air flow rate {m3/s}

    design day,              !- heating design air flow method

    ;                        !- heating design air flow rate {m3/s}

 

In the components (coils, fan?) I left the fields with the autosize option.

 

To simulate a worst case scenario, I defined the day type as WinterDesignDay
and defined the internal gains schedule to off for this day. 

 

I ran the sizing objects and the design day simulation and I? get the
following warning:

 

 

** Warning ** The design coil load is zero for COIL:Water:SimpleHeating P1 -
SALA_CIRURGIA REHEAT COIL

   **   ~~~   ** The autosize value for max water flow rate is zero

   **   ~~~   ** To change this, input a value for UA, change the heating
design day, or lower

   **   ~~~   **   the system heating design supply air temperature

 

To debug the problem I? ve asked the following report variables:

                Zone/Sys Sensible Load Predicted

            Zone/Sys Thermostat Heating Setpoint

                

I don?t understand why I get this warning because zone temperature is lower
than the set-point, a heating load is predicted and the thermostat heating
set point is 20ºC. I also checked the component connections,  flow rates and
availability schedules and everything seems to be alright. 

 

I?m missing something? Could anyone help me?

 

Thanks in advance for your help

 

Best regards

 

 

Filipe Madureira

Tel: +351 919 293 876 | E-mail: filipe.madureira@xxxxxxxxxxxxx

__________________________________________________________________

FluidInova, Engenharia de Fluidos, SA

TECMAIA - Parque de Ciência e Tecnologia da Maia

Rua Engº Frederico Ulrich, nº 2650  |  4470-605 Moreira da Maia | Portugal


Tel: (351) 229 408 265  |  Fax: (351) 229 408 266

E-mail:  <mailto:geral@xxxxxxxxxxxxx> geral@xxxxxxxxxxxxx  | Web:
<http://www.fluidinova.pt/> http://www.fluidinova.pt/

 



[Non-text portions of this message have been removed]



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/