Question to: Infinite or Not-a-Number value encountered

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Karsten Gros 2017-1-8

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评论： Karsten Gros 2017-1-10

enright.m

Hi, I have a question regarding my matlab-code. Basically, the code should calculate the heat-transfer for drop-wise condensation. At first, the program worked just fine, but I received a unexpected solution, so I searched for mistakes. At line 64, I noticed that I wrote a / instead of * (kJ to J is obviously *1000 not /1000 ;) ) So after I corrected that mistake, the Warning: "Infinite or Not-a-Number value encountered" occurred (at the matlab-function integral, line 106 to 108). I attached the file, so if anyone is willing to help me, you would make me very happy :) I guess the problem is, that at line 64, h_fg gets too big (from /1000 to *1000, so factor 10^6), any ideas how I could get the program fixed? Thanks in advance and best regards, Karsten

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Answer 1

Jordan Ross 2017-1-10

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Hello,

This is a result of your function have a discontinuity and trying to integrate between points where the discontinuity exists. If you plot the function "start" you will see that the function is undefined around R = 0 and R = -2.

>> figure; fplot(start);

Furthermore, if you try and evaluate the function "start" at R=R_stern you will get that the value is "NaN" leading to the integral giving you this error.

>> start(R_stern)
ans =
     NaN

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Karsten Gros 2017-1-10

Thanks, I guess the problem is on the function n (R) I guess... But how can the function work with h_fg=h_fg/M_w/1000, but not with h_fg=h_fg/M_w*1000? (line 65) Any idea?

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