[Bldg-sim] eQuest evaporative pre-cooling

[Nidhi Vyas]

Dear Jim,

Thank you for your input.

In eQuest there is an option to use the return air as secondary air so that
is helpful.

I tried to control the evaporative pre-cooling entering air temperature
through economizer controls and schedules too but unfortunately nothing is
working out. If I look over the hourly reports i still see that evaporative
pre-cooling is treating the OA below 70F.

Again thank you for your help.

Nidhi


On Sun, Jul 15, 2012 at 6:00 PM, Jim Dirkes <jim at buildingperformanceteam.com
> wrote:

> Dear Nidhi,****
>
> I am not familiar with eQuest, so I cannot help much with the specifics of
> that program.****
>
> About one year ago I modeled an indirect evaporative system (Maisotsenko
> cycle specifically) in EnergyPlus and had some difficulties which I have
> noted below.  They may help focus your efforts!****
>
> ** **
>
> 1.            Energy Plus version 6 cannot place the condenser coil in the
> exhaust of an indirect evaporative cooler.  It can be defined with an
> evaporatively cooled condenser.  We assume that good results can be
> obtained by choosing the same evap effectiveness as for the M-cycle and
> making them both available for the same months.****
>
> 2.            Energy Plus cannot currently model a VSD secondary / exhaust
> fan for an indirect evap cooler.  Energy reduction for both a cycling and
> VSD-equipped secondary / exhaust fan was assumed similar to that
> experienced by the supply fan.  This is modeled by reducing the secondary
> fan delta P  to xx%  (varies by climate) of actual.****
>
> 3.            Secondary / exhaust air  can come only from the outdoors in
> EnergyPlus.  Thus no mixed air can be used.****
>
> 4.            Economizer controls in EnergyPlus always look at the outdoor
> air temperature. We’d rather control based on the temp leaving the M cycle
> heat exchangers.  This requires a special, climate-specific schedule in
> EnergyPlus.  Not difficult, but takes more time.****
>
> ** **
>
> ** **
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Nidhi Vyas
> *Sent:* Friday, July 13, 2012 10:26 PM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] eQuest evaporative pre-cooling****
>
> ** **
>
> Hi everyone,****
>
>  ****
>
> I am working on a California project pursuing Title-24 2008 and using
> eQuest for the analysis. The project includes VAV with chilled water
> cooling and hot water reheat system . Additionally the system is 100% OA
> system and also includes indirect evaporative pre-cooling in the design. My
> model indicates that the evaporative pre-cooling is helping on the cooling
> energy savings ( as expected) but I am getting heating penalty because of
> it. ****
>
>  ****
>
> After digging into the simulation output reports it seems that the reheat
> energy has increased significantly and the space temperature for the zones
> have more hours in the cooling temperature band. I believe that the
> evaporative pre-cooling is overcooling the spaces. Further, I think that
> the evaporative pre-cooling is treating OA with dry bulb as low as 55F.  *
> ***
>
>  ****
>
> Can somebody please suggest how to control the evaporative pre-cooling so
> that it comes on for OA above 70F temperature only. eQuest has a high limit
> set point for evaporative pre coolers but no low limit one.  Also, any
> thoughts on how to control the increase in reheat energy. ****
>
>  ****
>
> Thank you****
>
>  ****
>
> Nidhi****
>
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