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[EnergyPlus_Support] Discrepancy in PCM Results





Dear all,

I have defined a PCM (26 degree melt, 230 KJ/Kg enthalpy) using the Enthalpy-Temp curve two different ways using the object Materialproperty:phase change and applied it to the interior face of the east wall.

a) Gypsum Board PCM:                                   

   Temp - 0
   Enthalpy - 0
  Temp-26
  Enthalpy-230000
  Temp-100
  Enthalpy-230000

b) Gypsum Board PCM1

Temp-0
Enthalpy-0
Temp-20
Enthalpy-0
Temp-24
Enthalpy-0
Temp-26
Enthalpy-230000
Temp-28
Enthalpy-230000
Temp-30
Enthalpy-230000
Temp-40
Enthalpy-23000
Temp-100
Enthalpy-23000

As you can see both "hypothetical PCMs" melt at 26 degrees and have the same energy storage capability.But when I use PCM -a versus PCM-b for the same IDF file. I get two different results in heating and cooling energy loads? A long time ago I was told that the enthalpy stays the same until you define a different temp/enthalpy pair.

For instance, if you define:
Temp-0
enthalpy-0 
it stays enthalpy-0 even at temp 25. until you add another temp enthalpy pair such as 
Temp-26
Enthalpy-230000.

So my question is why am I getting two different results?

I would appreciate any insight regarding this issue. 

Sincerely yours'
Niraj


--
Niraj Poudel, Architectural Engineer.
PhD student, PDBE Program.
Clemson University, Clemson, SC.




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Attachment not found:
d:\eudora\attach\East.idf