Fluid Cooler

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I am having issues with the heat exchanger for a fluid cooler (closed
circuit cooling tower) in eQuest 3.64. I can run the simulation without the
heat exchanger, but get a series of the following message:
CURINV: No real root for CURVE:
1 0.449745 0.027043 -0.000444 -0.028325 0.000285 0.001570
which appears to be from the FluidCooler-FluidCap-fApp&WB performance
curve. This is likely due in part to operating the system at freezing
temperatures with the spray pump on.

If I add the heat exchanger so that I have a dry cooler for the winter
months (set the Wet Schedule to 60F), I get the following error:
***ERROR***********************************************************************
Heat-Exchanger: FluidCooler-DryHX has
inconsistent
input parameters for flow calculations
Mode SupTi DemTi DemTo
3 39.00 82.00 82.00
I allow everything for the heat exchanger to default as well as the
performance curves for the fluid cooler. The values for SupTi, DemTi and
DemTo will vary somewhat, but DemTi always equals DemTo, which I think may
be a problem.

The fluid cooler serves a heat pump loop that also serves as the condenser
water loop for a chiller. I'm trying to maintain the HP loop temperature
between 75 and 85F with additional heat provided by a boiler. I have
attached the .inp and .pd2 files if they may be of help.

Any help would be appreciated.

--
Ron Pecarina, PE, CEM, LEED-AP

Ron Pecarina's picture
Offline
Joined: 2011-09-30
Reputation: 0

I am having a problem with a fluid cooler on a project. The fluid cooler is
a closed circuit cooler that provides heat rejection for a heat pump loop.
I can get the model to run if I omit the heat exchanger which is integral to
the fluid cooler or if I provide a Wet Schedule, but delete the heat
exchanger. I realize that neither one of these options will give me the
results that I truly need, but it sort of works for some comparative
purposes. I have also tried this on 3.63 with the same results.

When I run either of the options identified above, I get the following
messages:

**CAUTION**********************************************************************
In curve: FluidCooler-FluidCap-fRng&WB the dependent value
is exceeding the limits.
Value/Min/Max/First time: 4.981
0.000 3.000 1/27/16
CURINV: No real root for CURVE:
1 0.449745 0.027043 -0.000444 -0.028325 0.000285 0.001570

The CAUTION I can get around. But the CURINV, which relates to the
FluidCooler-FluidCap-fAPP&WB performance curve, typically ends up as
thousands of lines in the output file. I have yet been able to identify the
cause.

When I add the heat exchanger, the model crashes and I get the following
error:
***ERROR*********************
**************************************************
Heat-Exchanger: FluidCooler-DryHX has
inconsistent
input parameters for flow calculations
Mode SupTi DemTi DemTo
3 39.00 82.00 82.00

The values for SupTi, DemTi and DemTo will vary depending on other
parameters that I may change, but DemTi always equals DemTo.

I have attached the input and pd2 files for the case without the heat
exchanger. Adding the heat exchanger is simply inserting the Wet Schedule
(Cooler Sch) and using the first Heat Exchanger from the Library. I
apologize for the size and complexity of the building model, but it's what I
have to deal with.

I also note that the pan losses/pan heater are not accounted for in the
model.

--
Ron Pecarina, PE, CEM, LEED-AP

Ron Pecarina's picture
Offline
Joined: 2011-09-30
Reputation: 0

I am having a problem with a fluid cooler on a project. The fluid cooler is
a closed circuit cooler that provides heat rejection for a heat pump loop.
I can get the model to run if I omit the heat exchanger which is integral to
the fluid cooler or if I provide a Wet Schedule, but delete the heat
exchanger. I realize that neither one of these options will give me the
results that I truly need, but it sort of works for some comparative
purposes. I have also tried this on 3.63 with the same results.

When I run either of the options identified above, I get the following
messages:

**CAUTION********************
**************************************************
In curve: FluidCooler-FluidCap-fRng&WB the dependent value
is exceeding the limits.
Value/Min/Max/First time: 4.981
0.000 3.000 1/27/16
CURINV: No real root for CURVE:
1 0.449745 0.027043 -0.000444 -0.028325 0.000285 0.001570

The CAUTION I can get around. But the CURINV, which relates to the
FluidCooler-FluidCap-fAPP&WB performance curve, typically ends up as
thousands of lines in the output file. I have yet been able to identify the
cause.

When I add the heat exchanger, the model crashes and I get the following
error:
***ERROR*********************
**************************************************
Heat-Exchanger: FluidCooler-DryHX has
inconsistent
input parameters for flow calculations
Mode SupTi DemTi DemTo
3 39.00 82.00 82.00

The values for SupTi, DemTi and DemTo will vary depending on other
parameters that I may change, but DemTi always equals DemTo.

I can provide the input and pd2 files if necessary, but hesitate due to size
and complexity of the building model, but it's what I have to deal with.

I also note that the pan losses/pan heater are not accounted for in the
model. I am not sure if this feature is supported at this time or not. The
unit has an electric pan heater, which I input. I have tried both
defaulting the values and inputting the pan loss, but neither results in any
energy use for the heater.

--
Ron Pecarina, PE, CEM, LEED-AP

Ron Pecarina's picture
Offline
Joined: 2011-09-30
Reputation: 0