Re: 回复： [EnergyPlus_Support] PsyPsat FnTemp+PsyTsatFnHPb

Hi, Richard

Loong used water to connect the twoer to the condenser coil. The temperature were the water temperature. Two nodes on the condenser side, and two on the tower side. The other variables in the tower object were autosized. I have noted your guide on flowrate/ton and delta T.

I think, those nominal capacity values were limiting the autosizing values. Most of the fields in the tower object were left blank.
================
The humidity related temperature rise has not been identified yet.

I think that if the OA is fed directly into a cooled zone, condensation will occur and produce those warnings.
=====================
Because building designer specified so much fresh air per person as a requirement, most of the students are feeding OA directly into each zone to meet the design requirement, and caused those warnings.

One student found a solution by pre-cool the OA to 7°C and then feed it to the zones as fresh air intake.

They wanted a 100% OA system, therefore the zone return air should not be mixed with the intake using the OA mixer box. They want to use the return air in a heat recovery system for the OA intake.

==========================
I shall spend a little time on loong's IDF to identify the problems.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: RRaustad@xxxxxxxxxxxx
Date: Thu, 7 Jul 2011 08:19:00 -0400
Subject: Re: 回复： [EnergyPlus_Support] PsyPsatFnTemp+PsyTsatFnHPb

If that's what it takes to bring the temperatures down, then yes, that's the correct approach. You could also set up the file to autosize those values and see what the program thinks those values should be.

The tower does calculate outlet air wet-bulb temperature but there is no outlet air node so I am surprised this node could be viewed in the output. As long as the node data with high temperatures is related to tower capacity, then adjusting the tower capacity is the correct fix. Water flow rate also provides a means for adjustment. And keep the capacity and flow rate in a range of about 2-"3" gpm/ton with 10F detla T.

On 7/6/2011 7:07 PM, YuanLu Li wrote:

Thanks, Richard.

The system node temperature values were displayed in Loong's csv. I did not know the significance of those high temperature values, as the chiller temperature values were normal.

I increased the tower capacity by 100 times, (the values highlighted below) and the temperature values are now reduced from 1548°C to around 45°C. This may not be the correct way.

There are still (18) warnings on his IDF error file.

Dr. Li

P.S. The change is highlighted below:

CoolingTower:TwoSpeed,

tower1, !- Name

tower1 CndW Inlet, !- Water Inlet Node Name

tower1 CndW Outlet, !- Water Outlet Node Name

, !- Design Water Flow Rate {m3/s}

autosize, !- Air Flow Rate at High Fan Speed {m3/s}

autosize, !- Fan Power at High Fan Speed {W}

, !- U-Factor Times Area Value at High Fan Speed {W/K}

autosize, !- Air Flow Rate at Low Fan Speed {m3/s}

autosize, !- Fan Power at Low Fan Speed {W}

, !- U-Factor Times Area Value at Low Fan Speed {W/K}

autosize, !- Air Flow Rate in Free Convection Regime {m3/s}

, !- U-Factor Times Area Value at Free Convection Air Flow Rate {W/K}

NominalCapacity, !- Performance Input Method
2000000, !- High Speed Nominal Capacity {W}

1000000, !- Low Speed Nominal Capacity {W}

200000, !- Free Convection Capacity {W}

, !- Basin Heater Capacity {W/K}

, !- Basin Heater Setpoint Temperature {C}

, !- Basin Heater Operating Schedule Name

, !- Evaporation Loss Mode

0.2, !- Evaporation Loss Factor {percent/K}

0.008, !- Drift Loss Percent {percent}

, !- Blowdown Calculation Mode

3, !- Blowdown Concentration Ratio

, !- Blowdown Makeup Water Usage Schedule Name

, !- Supply Water Storage Tank Name

tower1 Cooling Tower Outdoor Air Inlet Node, !- Outdoor Air Inlet Node Name

, !- Number of Cells

, !- Cell Control

, !- Cell Minimum Water Flow Rate Fraction

, !- Cell Maximum Water Flow Rate Fraction
1; !- Sizing Factor
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: RRaustad@xxxxxxxxxxxx
Date: Wed, 6 Jul 2011 13:32:44 -0400
Subject: Re: 回复： [EnergyPlus_Support] PsyPsatFnTemp+PsyTsatFnHPb
The psyc routines do have limits on inputs. The PsyPsatFnTemp routine returns saturation pressure (Psat) as a function of temperature (Temp). This routine is usually used to calculate RH or wet-bulb temperature. But this is really beside the point. The air temperature input to this routine is 1898.61 C. This is way out of bounds. I would report the air node temperatures in your simulation and see if you can find a node with this high of a temperature which may then help you determine what is happening in your simulation.

Output:Variable,*,System Node Temp,Hourly;

On 7/6/2011 1:13 PM, YuanLu Li wrote:

想不到你正的是龍王。黃森的理解是对的》

He mentioned the EPlus developer's guide. I wonder he has the Eplus source code to compare.

The names mentioned in the error message are the module internal variable name. I do not know the detail of the calculation.

I know that when the RH value is larger than 100%, the calculated temperature can go out of range.

Therefore, you can try increasing the cooling coil temperature, or reducing the wet-bulb temperature of OA to see whether the warning would disappear. These warnings did not stop the simmulation, and the results are still good.

You have 5 or 6 AHU's, timestep = 20, many zones. That is why you get more than 279556 warnings of the same type.

You have other problems in your IDF which prevent the temperature in the zones to be proerly controlled. Because I have not figured out how you named the zones, it will take some time to get an over all view of your design.

You seems to have two buildings (CD and OFF), one three storeys and one five stories. You have cooling chiller, but no heating plant equipment.   AHU provideds the cooling to a low temperature and then heated b the reheat heater in the zone. The reheat heater is also used for Winter heating.

The reheat coil can be used for humidity control with cooling in Summer and heating in Winter. I have not checked your schedules, etc.

The VAV damper setting, if reversed, would also caused the zone temperature control to fail.

You should look at the other warning vessages to fix the problems.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: aloongge@xxxxxxxx
Date: Wed, 6 Jul 2011 13:00:16 +0800
Subject: Re: 回复： [EnergyPlus_Support] PsyPsatFnTemp+PsyTsatFnHPb

恩谢谢

--- On Wed, 7/6/11, 森黄 <jawhasway@xxxxxxxxxxxx> wrote:

From: 森黄 <jawhasway@xxxxxxxxxxxx>
Subject: 回复： [EnergyPlus_Support] PsyPsatFnTemp+PsyTsatFnHPb
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Date: Wednesday, July 6, 2011, 12:14 PM

王龙

    我查看了e+的EnergyPlus Module Developer's Guide，我理解这几个错误的原因是根据模型计算得的回风温度过高，导致湿空气计算出现问题，因此问题的根源还在于房间的热平衡计算有问题。

   我再看看，有结果会和你联系

                                                                                                                黄森

--- 11年7月2 日，周六, 传说阿龙哥 <aloongge@xxxxxxxx> 写道：

发件人: 传说阿龙哥 <aloongge@xxxxxxxx>
主题: [EnergyPlus_Support] PsyPsatFnTemp+PsyTsatFnHPb
收件人: energyplus_support@xxxxxxxxxxxxxxx
日期: 2011年7月2日,周六,下午4:42

Hello, I have some questions to ask for your help. I model a VAV with PFP Boxes system with a screw chiller provides chilled water. There are some warnings after I run the model, which are list below:

1) ** Warning ** Temperature out of range [-100. to 200.] (PsyPsatFnTemp)
   **   ~~~   ** Routine=PsyWFnTdbRhPb, Environment=SUMMER DESIGN DAY, at Simulation time=07/15 00:00 - 00:03
   **   ~~~   ** Input Temperature=1898.61

2) ** Warning ** Enthalpy out of range (PsyTsatFnHPb)
   **   ~~~   ** Routine=Unknown, Environment=WINTER DESIGN DAY, at Simulation time=01/21 00:00 - 00:03
   **   ~~~   ** Enthalpy=327804470.59739 Pressure= 101241.00
   **   ~~~   ** Initial Resultant Temperature= 99.01

Can you tell me why these warnings occured, or how can I modify my model to avoid these warnings? Thank you!

Best wishes!

                                                              loong
-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL  32922-5703
Phone:   (321) 638-1454
Fax:     (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu

UCF - From Promise to Prominence: Celebrating 40 Years

-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL  32922-5703
Phone:   (321) 638-1454
Fax:     (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu

UCF - From Promise to Prominence: Celebrating 40 Years