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Re: [EnergyPlus_Support] DX:CoolingBypassFactorEmpirical object
The supply air condition in the zone sizing object is too low for the
coil's process line to cross the saturation curve. You are using a rated
inlet air dry-bulb temperature of 26.7 C and rated inlet air wet-bulb
temperature of 19.4C (rated inlet air humidity ratio = 0.01125 kg/kg)
with a zone sizing object supply air temperature of 16C and zone sizing
supply air humidity ratio of 0.008. If you draw a line from the rated
inlet air condition to the zone sizing supply air condition, you will
see that this line does not cross the saturation curve on the
psychrometric chart.
Try increasing the supply air humidity ratio to 0.009. This should allow
the bypass factor calculation to converge.
Brian Aldred wrote:
>
> We have an input file which uses the
> COIL:DX:CoolingBypassFactorEmpirical object and is causing some problems.
>
> I have uploaded the example file HevacompDXCoolingProblem.zip.
>
> When run through v1.4 an error is reported as follows:
>
> ** Severe ** COIL:DX:COOLINGBYPASSFACTOREMPIRICAL "WC:C2 FF OPEN" --
> coil bypass factor calculation did not converge after max iterations.
> ** ~~~ ** The RatedSHR of 0.571, entered by the user or autosized (see
> *.eio file),
> ** ~~~ ** may be causing this. The line defined by the coil rated
> inlet air conditions
> ** ~~~ ** (26.7C drybulb and 19.4C wetbulb) and the RatedSHR (i.e.,
> slope of the line) must intersect
> ** ~~~ ** the saturation curve of the psychrometric chart. If the
> RatedSHR is too low, then this
> ** ~~~ ** intersection may not occur and the coil bypass factor
> calculation will not converge.
> ** ~~~ ** If autosizing the SHR, recheck the design supply air
> humidity ratio and design supply air
> ** ~~~ ** temperature values in the System Sizing and Zone Sizing
> objects. In general, the temperatures
> ** ~~~ ** and humidity ratios specified in these two objects should be
> the same for each system
> ** ~~~ ** and the zones that it serves.
>
> Given the absense of a system sizing object, I am unsure how else to
> address this problem. Any help would be appreciated.
> Brian Aldred
> Software Development
> Tel: 0114 255 6680
> Fax: 0114 255 6638
>
> Hevacomp Ltd is a company registered in England and Wales with company
> number 1523216
> Registered office: Smithywood House, Smithywood Crescent, Sheffield,
> S8 0NU
>
> P Help save paper - do you need to print this email?
>
> [Non-text portions of this message have been removed]
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
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