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From: Jorian on 7 Mar 2010 05:45
"Arnaud Miege" <arnaud.miege(a)nospam.mathworks.co.uk> wrote in message <h0np5n$b24$1(a)fred.mathworks.com>...
>
> "Robert " <rjseme(a)rit.edu> wrote in message
> news:h0n62q$dme$1(a)fred.mathworks.com...
> > "Arnaud Miege" <arnaud.miege(a)nospam.mathworks.co.uk> wrote in message
> > <h0meqe$m2b$1(a)fred.mathworks.com>...
> >> "John Kreuder" <gedoboarder(a)hotmail.com> wrote in message
> >> <h0mbdm$5sv$1(a)fred.mathworks.com>...
> >> > I am using Simscape to create a thermal system models. For proof of
> >> > concept, I am trying to model a Brayton Cycle (compressor, combustor
> >> > and turbine in series, where the compressor is driven by the work
> >> > output of the turbine). Since both pressure and temperature of the air
> >> > entering the turbine are needed to predict the work output, I am using
> >> > my own domain adapted from the Simscape hydraulic foundation library
> >> > that includes both pressure and temperature as across variables, while
> >> > the only through variable is mass flow rate. All of the Demos and
> >> > examples from Mathworks consist of domains that contain only one
> >> > through and one across variable. How, if at all, does my domain differ
> >> > and what sort of workarounds do you recommend?
> >>
> >> Hi,
> >>
> >> I would suggest adding heat flow as a through variable. The tricky part
> >> is defining temperature-dependent domain-wide parameters, such as fluid
> >> properties. If you manage to get it working, I would encourage you to
> >> post it to the FEX for sharing with the rest of the community. Good luck!
> >>
> >> Arnaud
> >
> > Arnaud,
> > But can one still have two across variables with one variable? What
> > problems might arise if such a domain definition is used?
> >
> > Won't adding heat flow as a through variable actually cause problems since
> > the heat flow of a component such as a heat exchanger, combustor, turbine,
> > etc. will actually change "across" the component?
> > Rob
>
> Hi Rob,
>
> You can have two across variable and one through variable, there are no
> rules as to the number of across and through variables in a domain, but it's
> generally good practice to have a pair of across and through variables, in
> your case pressure/mass flow rate and temperature/heat flow. The effect of
> heat flow (in J/s) on temperature is similar to that of mass flow rate on
> pressure. The through variable is what flows through a port (and therefore
> you measure it in series) whereas the across variable is something that you
> measure relative to a reference, i.e. in parallel. Think of voltage and
> current in the electrical domain. Additionally if you are using the latest
> versuion (R2009a), the source code for most of the blocks in the Simscape
> foundation library is provided.
>
> HTH,
>
> Arnaud
>
Thanks!

Best regards, Jorian Seokaner!

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