Today the Thermo Special Interest Group (Thermo SIG) of CO-LaN has issued a request for input to the CO-LaN membership. Several organizations within CO-LaN have already contributed their experience. Through this Post the Thermo SIG hopes to reach out to more individuals and organizations capable to provide input. This request is about two properties.

Within the CAPE-OPEN Thermodynamic and Physical Properties interface specification, many properties are defined as belonging to the CAPE-OPEN standard. CAPE-OPEN based PMEs and PMCs have the same understanding of each of these defined properties. Through CAPE-OPEN interfaces, it is however possible to make use of properties that are not defined by the CAPE-OPEN standard. Then it is dubious that all PMEs and PMCs will give the same meaning to these non-defined properties which are just then known by their identifiers, i.e. their name. Consequently it is important for the CAPE-OPEN standard to cover all the properties which are of use in process engineering.

The Thermo SIG is evaluating the need to change the specification for two properties.

The first property is relative permittivity, also known as dielectric constant. This property is in principle a single-phase property which is nowadays defined in the CAPE-OPEN standard solely as a temperature-dependent property for pure compounds. However, relative permittivity for a pure compound depends also on frequency of an electro-magnetic field. The current design of the CAPE-OPEN Thermodynamic and Physical Properties interface specification does not allow for a frequency dependence for a property. Relative permittivity may also be considered as a mixture property that depends on temperature, pressure, and composition as well as on frequency. If that has to be taken into consideration, it is simpler: it means adding relative permittivity to the list of mixture properties. As an alternative to considering it as a frequency-dependent property, relative permittivity could also be reported at 0 Hz frequency, i.e. in a static electro-magnetic field. This would mean that the definition of relative permittivity would have to be modified, stating that it is reported at 0 Hz frequency. A minor modification to the interface specification would suffice for that.

The second property is refractive index which currently has no definition in the CAPE-OPEN standard. This property is in principle a single-phase pure compound as well as mixture property that in addition to temperature, pressure, and composition, depends on light wavelength.

The Thermo SIG is trying to establish whether there is a business case to (re)define these properties within the CAPE-OPEN standard, and if so, whether such properties should be obtained at frequencies or wave lengths requested by the Property Package client, or alternatively delivered at frequencies or wave lengths that the Property Package is capable of calculating the property at.

If you have a Property Package that is capable of calculating these properties, or if you have a PME or Unit Operation that is able to consume these properties, we would like you to inform the Thermo SIG how these properties are calculated and what are their application range, so that the Thermo SIG may come up with a design that allows exchange of these properties. Please send your input to technologyofficer at