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I want to analyze and make model of the water mixing process as shown in file in attacment. Basically, there are two input variables: input hot water flow and cold water flow. There is constant flow FL3. I need to write equation that describe how level and tank's temperature is changing. Equation for the level is:

dh/dt=(FL1(t)+FL2(t)-FL3(t))/Area;

And I need to figure out what equation to use to describe temperature.

At first I thought that this is correct equation:

V*dT/dt = Fl1*T1+Fl2*T2-(FL1+FL2)*T

But I have saw different equation:

V*dT/dt = Fl1*T1+Fl2*T2-FL3*T

Which of these is correct?

I know that these equations should be derived from heat equations m*C*(Ta-Tb), but not sure how to do this.

Can you help?

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# Writing correct physical equation for mixing process

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