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Unexpected results when adding water-side economizer to Data Center

asked 2015-07-06 22:03:01 -0600

I am trying to model a data center using the new ITE load added to v8.3 and wanted to be able to take credit for water-side economizer. I attempted to add water-side economizer based on the example file WaterSideEconomizer_Integrated.idf, but I get an increase in energy use. Click the following links to download the IDF file without water-side economizer and the IDF file with water-side economizer.

Should I use the NonIntegrated example file as the basis instead?

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answered 2015-07-14 05:27:13 -0600

Chandan Sharma's avatar

Though the simulation is running to completion, error file is showing that condenser loop is reaching very high temperatures.

   *************  ** Warning ** Plant loop exceeding upper temperature limit, PlantLoop="CONDENSER WATER LOOP"
   *************  **   ~~~   **   This error occurred 1618 total times;
   *************  **   ~~~   **   during Warmup 1593 times;
   *************  **   ~~~   **   during Sizing 0 times.
   *************  **   ~~~   **   Max=208.222976
   *************
   *************  ** Warning ** GetSpecificHeatGlycol: Temperature out of range (too high) for fluid [WATER] specific heat **
   *************  **   ~~~   **   This error occurred 20044 total times;
   *************  **   ~~~   **   during Warmup 0 times;
   *************  **   ~~~   **   during Sizing 0 times.
   *************  **   ~~~   **   Max=207.045248 {C}  Min=125.038743 {C}
   *************
   *************  ** Warning ** GetDensityGlycol: Temperature out of range (too high) for fluid [WATER] density **
   *************  **   ~~~   **   This error occurred 4436 total times;
   *************  **   ~~~   **   during Warmup 0 times;
   *************  **   ~~~   **   during Sizing 0 times.
   *************  **   ~~~   **   Max=207.045248 {C}  Min=100.100167 {C}
   *************

Looking at condenser loop outputs revealed that tower with hard sized UA value of 1241 W/K does not have enough capacity to meet the cooling demand. Increasing the UA to 12410.12 W/K brought the loop temperatures down to within maximum limit and economizer started working.

image description

After the modification above SimHVAC warning appeared in the error file with message that the solution for one or more plant systems did not appear to converge.

   ** Warning ** SimHVAC: Maximum iterations (20) exceeded for all HVAC loops, at ANNUAL1, 03/18 11:36 - 11:42
   **   ~~~   ** The solution for one or more plant systems did not appear to converge
   ** 
   ** 
   **   ~~~   ** Plant System Named = CHW LOOP CHILLED WATER LOOP did not converge for temperature

Chiller object has reference leaving chilled water temperature set to 43.4804 and entering condenser fluid temperature set to 28.33 C.

Chiller:Electric:EIR,
    Chiller 1,               !- Name
    418505.530799999,        !- Reference Capacity {W}
    4.2,                     !- Reference COP {W/W}
    43.4804,              !- Reference Leaving Chilled Water Temperature {C}
    28.3333333333333,        !- Reference Entering Condenser Fluid Temperature {C}

The chilled water loop is only having heating demand and no cooling demand. Lowering down 43.4804 C to 20 C got rid of the SimHVAC warnings. There are both cooling and heating demands in chilled water loop now which gets better if reference leaving chilled water temperature is further reduced to 10 C or 6.67 C. This may need more investigation.

Error file is mostly clean now with some geometry issues still remaining to be fixed. Weather file used in the annual simulation is USAPAPittsburgh.725200_TMY2.epw.

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Asked: 2015-07-06 22:03:01 -0600

Seen: 258 times

Last updated: Jul 14 '15