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

Re: [EnergyPlus_Support] Re: "strange" autosize of Coil:Cooling:DX:SingleSpeed



Thanks for the update.

2014-12-12 14:46 GMT+01:00 fpasserini.tn@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx>:
 

With the consent of Michael J. Witte I'm reporting here his answer from the helpdesk:


So you want the cooling to be sized assuming no ventilation air and the heating to be sized with ventilation air? That will be difficult. EnergyPlus sizing expects the same outdoor air requirement for both heating and cooling. You could try to make an adjustment to the Sizing:System Central Cooling Design Supply Air Temperature (raise it by some amount to produce and equivalent delta-T across the coil ad design conditions). Or it may be easiest in this case to do a simulation with zero outdoor air in the desired zones and use the cooling coil sizing results to set hard capacity values for the coils.

Mike


---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <fpasserini.tn@...> wrote :


During summer season in some systems there is no outdoor air (those spaces are unoccupied since June until September and the SummerDesignDay is 7/21). Nevertheless, as â??User Design Air Flow [m3/s]â?? the value that is imposed in DesignSpecification:OutdoorAir is considered also in â??zone coolingâ??, although I imposed a schedule that is zero during the summer season. I asked to the helpdesk and it seems that the calculations for minimum outdoor air do not look at the schedules in the DesignSpecification:OutdoorAir object.

Here an example:

 

DesignSpecification:OutdoorAir,

    0serviziopalestra:Spogliatoio1 Design Specification Outdoor Air Object,  !- Name

    Flow/Zone,               !- Outdoor Air Method

    0.009440,                !- Outdoor Air Flow per Person {m3/s-person}

    0.000000,                !- Outdoor Air Flow per Zone Floor Area {m3/s-m2}

    0.110000,                !- Outdoor Air Flow per Zone {m3/s}

    0.000000,                !- Outdoor Air Flow Air Changes per Hour {1/hr}

    occupazione aule;        !- Outdoor Air Flow Rate Fraction Schedule Name

 

The schedule is the following one:

 

Schedule:Compact,

    occupazione aule,        !- Name

    Fraction,                !- Schedule Type Limits Name

    Through: 1/15,           !- Field 1

    For: AllDays,            !- Field 2

    Until: 24:00,            !- Field 3

    0,                       !- Field 4

    Through: 6/10,           !- Field 5

    For: Weekdays SummerDesignDay WinterDesignDay,  !- Field 6

    Until: 07:50,            !- Field 7

    0,                       !- Field 8

    Until: 16:10,            !- Field 9

    1,                       !- Field 10

    Until: 24:00,            !- Field 11

    0,                       !- Field 12

    For: Saturday,           !- Field 13

    Until: 07:50,            !- Field 14

    0,                       !- Field 15

    Until: 12:20,            !- Field 16

    1,                       !- Field 17

    Until: 24:00,            !- Field 18

    0,                       !- Field 19

    For: AllOtherDays,       !- Field 20

    Until: 24:00,            !- Field 21

    0,                       !- Field 22

    Through: 9/10,           !- Field 23

    For: AllDays,            !- Field 24

    Until: 24:00,            !- Field 25

    0,                       !- Field 26

    Through: 12/20,          !- Field 27

    For: Weekdays SummerDesignDay WinterDesignDay,  !- Field 28

    Until: 07:50,            !- Field 29

    0,                       !- Field 30

    Until: 16:10,            !- Field 31

    1,                       !- Field 32

    Until: 24:00,            !- Field 33

    0,                       !- Field 34

    For: Saturday,           !- Field 35

    Until: 07:50,            !- Field 36

    0,                       !- Field 37

    Until: 12:20,            !- Field 38

    1,                       !- Field 39

    Until: 24:00,            !- Field 40

    0,                       !- Field 41

    For: AllOtherDays,       !- Field 42

    Until: 24:00,            !- Field 43

    0,                       !- Field 44

    Through: 12/31,          !- Field 45

    For: AllDays,            !- Field 46

    Until: 24:00,            !- Field 47

    0;                       !- Field 48

 

The cooling design day (SummerDesignDay) is 7/21. As you can see, on 7/21 the value of the schedule is 0.

Nevertheless, the â??User Design Air Flow [m3/s] â?? in â??Zone coolingâ?? for that zone is calculated equal to 0.110 m3/s (=Outdoor Air Flow per Zone in DesignSpecification:OutdoorAir, without considering the schedule).

 

Here an image from the html report: http://oi58.tinypic.com/rtg85f.jpg


Iâ??ll let you know if Iâ??ll find a solution with the help of the helpdesk.

Best Regards



---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <jeannieboef@...> wrote :

That is strange. If the sizing objects have correctly deturmined that the design flowrate for cooling is zero, then why would the coil capacity be non-zero.

And to achieve your off coil outlet air setpoint with the minimum outdoor air?Does it need non-zero capacity to achieve that? You probably have that at Setpoint-11C.

Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)

i. A.
Jean Marais
b.i.g. bechtold

On 07.12.2014, at 16:33, "fpasserini.tn@... [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

In Sizing:System the field "Type of Load to Size On" is "Sensible".

Regards

 

 



__._,_.___
Posted by: Jean Marais <jeannieboef@xxxxxxxxx>


Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

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 currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

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



Visit Your Group
Yahoo! Groups
• Privacy • Unsubscribe • Terms of Use

__,_._,___