slPCMlib

User-defined PCM properties

If you have not found your PCM in the database you could use the following template to define a custom PCM and generate source code for it.

Set material parameters:

Phase transition behavior (heating)
Phase transition range	°C → °C
Peak shape	peak shift: %
Phase transition enthalpy (ℹ) This value depends on temperature. Here the upper limit of the transition range T_max is used as reference. See the enthalpy plot for an illustration!	J/g at °C

Single phase properties
Specific heat capacity (solid)	J/(g·K)
Specific heat capacity (liquid)	J/(g·K)
Thermal conductivity (solid)	W/(m·K)
Thermal conductivity (liquid)	W/(m·K)
Density (solid)	g/dm³
Density (liquid)	g/dm³
Dynamic viscosity (liquid)	mPa·s
Thermal expansion (liquid)	1/K

Switch between content to show:

xi peak app-cp h rho cond

Generate your material:

Name your PCM: and

Source code:

Select language: and or

Usage notes

Phase transitions and temperature range

Non-isothermal phase transition behavior is described by the lower and upper bound of the phase transition range, and by the peak shape. Different Ansatz functions are available to model the peak:

Smooth Step function (symmetric peak)
Sigmoid function (symmetric peak)
Gumbel Minimum Distribution function (asymmetric peak, left-skewed)
Log-Normal Distribution function (symmetric or asymmetric peak, left or right-skewed),
with user-defined 'peak shift parameter', a value of zero corresponds to the Normal Distribution function with a symmetric peak

All peak functions (except the smooth step function) show an asymptotic behavior, which means that the peak curves are never exactly zero, instead they approach zero when the temperature tends to infinity and minus infinity. The integral of the peak function is the liquid mass phase fraction ξ(T) which indicates the phase change progress. Because of the asymptotic behavior of the peak function, the phase fraction function never gives exactly ξ=0 g/g (material is completely solid) or ξ=1 g/g (material is completely liquid).
As a solution, we define the start and end of the phase transition temperature range by: T_min where ξ = 0.001 g/g, and T_max where ξ = 0.999 g/g.

Symmetric vs. asymmetric peaks

Measured peaks are often asymmetric. Asymmetric peaks can be modelled either by the Gumbel Minimum Distribution function, or by the Log-Normal Distribution function. The (user-defined) peak shift parameter (peak shift: -80 % ... 80 %) works only for the Log-Normal Distribution!
Try it out here:

Note: Some of the above user-defined models are also included in the Modelica/Dymola library GitHub-slPCMlib, see the Package slPCMlib.Media_generic.