[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[EnergyPlus_Support] Re: Water-to-Air Heatpump Issues
Mike,
Thanks a lot for your clarification on de-humidification options for
the water-to-air heatpump. I placed the desiccant de-humidifier
upstream of the heatpump and it worked like a charm!
Two other issues have surfaced with the water-to-air heatpump, though:
(1) If I run the HeatPumpWaterToAirEquationFit.idf example as-is the
supplementary heating coil kicks in during the winter design-day and
stays off during the summer design-day as I would expect it to. You
can see this on the "Heating Coil Rate" column "AY" on output
HeatPumpWaterToAirEquationFit.csv.
If I now reduce the "Rated Air Volumetric Flow Rate" parm on the
objects COIL:WATERTOAIRHP:EquationFit:COOLING and
COIL:WATERTOAIRHP:EquationFit:HEATING to 1.2 (from 2.0), I start to
see significant supplementary heating during the summer design-day!
I would have expected an increase in the supplementary during the
winter but not during the summer. For the summer, I would expect
zone temperatures to rise as the cooling coil is less able to meet
the load.
In my own heatpump run (not HeatPumpWaterToAirEquationFit.idf) I get
a similar pattern. Namely, if I set the Flowrate parm to the
heatpump design airflow calculated through an autoresize run or the
published airflow rate from the manufacturer, the supplementary
heater is completely off during the winter design-day and always on
during the summer design-day! This leaves me not sure what value to
use for this parameter. Any ideas? My goal is to get an accurate
estimate of the supplementary heating demand I will need for the
heatpump and building design I have tentatively chosen.
(2) In all runs involving the above-mentioned objects, I can't seem
to get electric power-related report variables to indicate anything
other than zeros on the .csv outputs (eg "Power [W]", column "AK" in
the above example csv). Is this a bug or am I doing something wrong?
Your input on these two items would be greatly appreciated!
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@...> wrote:
>
> The documentation for ZONE CONTROL:HUMIDISTAT does not tell the
whole story.
> For unitary systems which have a humidity control option, the
humidity control
> option must be activated and a ZONE CONTROL:HUMIDISTAT object added.
>
> But not all unitary systems have a humidity control option. Only
> FURNACE:HEATCOOL, UNITARYSYSTEM:HEATCOOL, and
> UNITARYSYSTEM:VAV:CHANGEOVERBYPASS support humidity control through
the
> "Dehumidification control type" field.
UNITARYSYSTEM:HEATPUMP:WATERTOAIR does
> not support humidity control
>
> In your model, the desiccant dehumidifier has been placed after the
heat pump.
> When the desiccant dehumidifier turns on to control humidity, it
also warms the
> air, so this is why the zone temperature control is no longer
working. If you
> choose to use a dessicant dehumidifier, it should be placed
upstream of the
> heat pump, either in the outside air system or in the main branch.
A sensible
> heat exchanger is usually place immediately after the dehumidifier
to reject
> some of the sensible heat gain from the desiccant wheel prior to
applying
> mechanical cooling. See examplefiles DesiccantCVRh.idf and
> DesiccantCVRhZoneRHCtrl.idf.
>
> Mike
>
>
> On 24 Apr 2007 at 1:41, energyplus99 wrote:
>
> > Is it true that a UNITARYSYSTEM:HEATPUMP:WATERTOAIR, being
a "unitary
> > system", only needs a ZONE CONTROL:HUMIDISTAT object added to
provide
> > humidity control? This is what the e+2.0 InputOutput Guide seems
to
> > suggest (page 872, second paragraph).
> >
> > Yet when I do this I get the following warnings along with
greatly
> > dimished control of cooling and humidity after simply adding the
> > humidistat:
> >
> > Calculated Humidity Ratio invalid (ie -0.5387) and
> > Temperature out of range [-100. to 200.] (ie 406353.15)
> >
> > (Just in case a UNITARYSYSTEM:HEATPUMP:WATERTOAIR system has no
means
> > for dehumidifying (such as controlling the airspeed over the
cooling
> > coil via the fan) I added a DESICCANT DEHUMIDIFIER:SOLID object
to
> > boot).
> >
> > Without the humidistat the system controls nicely for
temperature,
> > albeit humidity is high for the summer design day.
> >
> > The enclosure I am using is a simple 3-meter-cubed
stucco/insulated
> > cube with a single window. So I know that the heatpump/GSHE
system
> > is large enough to handle any HVAC needs of this small space.
> >
> > I've uploaded the IDF for this run (CubeSimpleWindow.idf). Would
> > anyone have any ideas as to why I'm getting these warnings and
the
> > consequent poor performance? Am I making the wrong assumptions
as to
> > what it takes to dehumidify a water-to-air-heatpump/GSHE system?
> >
> > Any thoughts would be greatly appreciated.
> >
> >
> >
> >
> >
> > 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
> >
> >
> >
> >
> >
>
>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@...
>
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/