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How to define PCM enthalpy curves for EnergyPlus

asked 2017-06-28 04:18:09 -0500

Tim gravatar image

updated 2017-06-29 10:47:41 -0500

Hi all, PCM manufacturers often provide the following technical data on their products:

  • 'Switching' temperature 23°C
  • Latent heat capacity ∆H 330 kJ/m2 at 'switching temperature'
  • Specific heat capacity approx. 1.20 kJ/kgK
  • Thermal conductivity λ approx. 0.18 W/(mk)

How can one define the enthalpy curve of the material for the use in EnergyPlus based on this? The IDF file takes inputs as shown below. With the ∆H provided for the switching temperature I can describe the jump at 23C but how is the base enthalpy of the material inferred so that data-points for -20C, 20C and 100C can be provided to EnergyPlus.

0.0, !- Temperature coefficient ,thermal conductivity(W/m K2)
-20., !- Temperature 1, C
0.01, !- Enthalpy 1 at –20C, (J/kg)
20., !- Temperature 2, C 33400, !- Enthalpy 2, (J/kg)
20.5, !- temperature 3, C 70000, !- Enthalpy 3, (J/kg)
100., !- Temperature 4, C 137000; !- Enthalpy 4, (J/kg)

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answered 2017-11-18 04:42:30 -0500

Nima8927 gravatar image

Hi Tim. It is not possible to form the enthalpy-temperature curve through the thermophysical data. These curves are usually drawn using the data from experiments. Most manufacturers do not provide all details of their products. However, they provide an email address which you can contact them for more detailed enthalpy-temperature curves. Here are the links of some suppliers that can help you through.

Rubitherm GmbH

CRISTOPIA Energy Systems


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Asked: 2017-06-28 04:08:26 -0500

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Last updated: Nov 18 '17