Hey
I am also currently pursuing research on PCM in the building envelope. You need to know the variation of heat capacity (Cp) of the PCM with temperature. Or at least Cp at solid phase, solid-liquid transition phase and liquid phase. You can try asking the manufacturer for these details, else if you have PCM sample, you can do a DSC (Differential Scanning Calorimetry) analysis to get Cp values.
To your questions:
1. The PCM thermal conductivity (k) may vary with temperature. That field defines how k varies with temperature. This can also be found using DSC. If not you can take that value as 0. From my research simulation, increasing k value of PCM has insignificant effect on
buildings.
2. Specific Enthalpy = [Heat Capacity * Temperature]/mass
Unit Check: J/kg = [( J/°C)*(°C)]/(kg)
The units can vary depending upon the DSC instrument. Basically, you will need a enthalpy curve as seen in 1st attachment. You can also read this interesting journal article: "Advanced Zone Simulation in Energyplus: Incorporation of Variable Properties and Phase Change Material (PCM) Capability" by C.O.Pedersen, Proceedings: Building Simulation 2007.
Please let me know if you have further
questions.
Thanks
Karthik M, LEED GA, EIT
Masters Student
Mechanical Engineering, SEMTE
Vice-President, ASHRAE @ ASU
Arizona State University
kmurugan@xxxxxxx
Tempe, AZ, US
From: alterea_nrjplus <akerneur@xxxxxxxxxx>
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Sent: Wed, 13 October, 2010 7:28:28 AM
Subject: [EnergyPlus_Support] PCM in energyplus
Hi All,
I'd like to use in my project a PCM : ENERGAIN of Dupont
The material property is :
0.18, !- Conductivity {W/m-K}
855, !- Density {kg/m3}
4 140, !- Specific Heat {J/kg-K}
Latent heat storage capacity : 71 kJ/kg
Melt point : 21.7°C
I don't know how definate (with my material property above)the :
Field: Temperature Coefficient for Thermal Conductivity
Field Set: Temperature-Enthalpy
I try to understand with Input-Output Reference but i can't.
Can you help me
Thanks a lot