[TRNSYS-users] Type511 fluid cooler Design ambient air temperature > 20 °C

Jeff Thornton thornton at tess-inc.com
Tue May 15 09:49:34 PDT 2018


The fluid cooler model can certainly handle high ambient temperature conditions.  The only reason we have users change that parameter from 28 to 20 is that the default parameters (airflow, inlet and outlet water temperatures etc) supplied with the model (with 28 C and not 20),that are used to solve for the design heat transfer, create an impossible condition and the model reports the error.  For example you can’t make 25 C water with 30 C air and the model would report the same error if you supplied those conditions as the design parameters.

All you have to do is supply a set of consistent parameters and the model will behave beautifully.


Sent from my iPhone

> On May 15, 2018, at 11:23 AM, Eric Peterson via TRNSYS-users <trnsys-users at lists.onebuilding.org> wrote:
> Regarding the Type 511 Dry Fluid Cooler by Jeff W. Thornton last modified September 2014
> “Type511 models a dry fluid cooler; a device used to cool a liquid stream by blowing air across coils containing the liquid.
> This model assumes that the device can be modeled as a single-pass, cross-flow heat exchanger;
> which is typically how these devices are constructed.”
> I read in blog somewhere that you must change the seventh parameter from 28 °C default to 20 °C.
> “The dry-bulb temperature of the air entering the device at design conditions”
> Why shouldn’t users be able to specify higher ambient conditions without the TRNSYS ERROR
> “The dry cooler model was unable to correctly calculate the number of transfer units (NTU) for the design condition.
> Please check the design conditions carefully.”
> In practice ambient may reach 45°C in summer heat wave conditions.
> Eric Peterson, PhD, PE, RPEQ, M-ASHRAE TC4.2 Climatic Data
> Research Fellow in Geothermal Systems Modelling
> http://www.geotech-project.eu/?portfolio=university-of-leeds
> School of Civil Engineering, University of Leeds
> Leeds, West Yorkshire LS2 9JT United Kingdom
> Telephone +44 (-0) 11334 31957
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