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Create a model to solve an energy balance

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kasim
kasim on 30 Mar 2020
Commented: kasim on 1 Apr 2020
Hi, I am trying to use MATLAB to create a model that can solve a set of equations. I have attached an image of the equations I am trying to solve. Essentially, there are 3 unknowns, Tout, Tp & Tg.
I wanted to ask which would be the best way to solve this on MATLAB, i have tried to use matrices but the temperatures I am getting are very high. Is there any other method that could be used to solve these equations?
Kind regards

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kasim
kasim on 30 Mar 2020
Again, thank you!
with regards to this line: [Tg Tout Tp Tm hrpg hrgs] = deal(x(1),x(2),x(3),x(4),x(5),x(6));
is this the order in which the answers are outputted? i.e. Tg = Value 1, Tout = Value 2
darova
darova on 30 Mar 2020
Yes
Experiment with x0 (initial guess) for different outputs

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Answers (1)

Alex Sha
Alex Sha on 31 Mar 2020
Hi, I get two solutions:
No. 1 2
tg -328.861557610457 -549.471818197512
tm 1.72830356360143 -541.712011528394
hrpg -0.00727597589137702 -11.1180945451184
tp 326.846969797053 -548.48073838475
hrgs 0.0134500837438822 -4.90776624779464
tout -326.543392872797 -1413.42402305679

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kasim
kasim on 31 Mar 2020
Hi, I have found a mistake in my model, which is perhaps why you're getting different results.
eq1 should read as ag*I + hg*(Tg-Tm) + hrpg*(Tp-Tg) + (hw+hrgs)*(Tg-Ta)
Perhaps this may provide some accurate values?
Alex Sha
Alex Sha on 1 Apr 2020
then the result will be:
tm: 330.112356511329
tg: 329.614806294714
hrpg: 2.41746002404232
tp: 330.611779336469
hrgs: 7.81080204482525
tout: 330.224713022658
Feval:
9.35251875944232E-12
-6.95421498164706E-12
-1.83834281131112E-10
-5.6843418860808E-14
-3.1827873669954E-12
-3.30402372128447E-13
kasim
kasim on 1 Apr 2020
Hi, Could you show me how you coded this?

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