Why only energy equations are solved when HTC is defined via UDF in Eulerian Multiphase model?
my goal is to model interphase heat transfer inside "Two-Resistance" model using user-defined volumetric heat transfer coefficient (HTC) at "To-Phase" in Eulerian Multiphase solver implemented in academic version of ANSYS Fluent 2019 R3.
Incorporation of user-defined volumetric HTC results in solution of only the energy equations, as shown in the attached figure. Here, the code for "Ranz-Marshall" model available in [1, p. 172] is used.
However, if "Ranz-Marshall" model already available in the software is used, all the conservation equations are being solved, as denoted in the figure.
The question is: "What is missing and causing solution of only energy equations?"
Many thanks in advance!
 ANSYS, Inc., ANSYS Fluent Customization Manual, Release 2019 R2, 2019.