Improve SimpleConsumer

Created by: alexanderAKU

What is the problem?

• The model SimpleConsumer contains a volume with convection to a fixed temperature. It would be benificial to have more options, e.g. predescribed heatflow or varianle temperature, thus, this model could be used for several applications

How do we want to solve it? Describe the solution you'd like

• Add options to select between internal fixed temperature, external temperature, internal fixed heatflow, external fixed heatflow.