I want to calculate each v value from each diameter value, then the value of Re one by one, and for all the calculations in the for loop,but this code give me single value for v, Re, f . Where am I doing wrong? Sorry I'm beginner in mtlab.

Question

hüsna özlem mermer 2021-5-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/832213-i-want-to-calculate-each-v-value-from-each-diameter-value-then-the-value-of-re-one-by-one-and-for

回答： David Hill 2021-5-17

clc;
close all;
clear;
L=(2000+(5*50))
T=5+5*0.25
It=0.0075*L
ht=0.15*T
bt=0.50*It
e=0.0003*(5+50)
t=15000/sqrt(9.81/ht)
V=It*ht*bt
flwrt=V/t
iteration=1;
for D=0.1:0.01:0.5
    v=4*flwrt/pi*D;
    Re=(v*D)/0.00000131;
    f=1.325/(log10(e/D*3.7+5.74/Re^0.9));
    hp=5+5*0.25+(v^2)/2*9.81*[f*(2000+5*50)/D+8.1];
    totalhead(iteration)=(v^2)/2*9.81*[f*(2000+5*50)/D+8.1];
    Ppower(iteration)=((9.81*1000*flwrt*hp)/1000);
    valvecost=320+(D/25)*200;
    elbowcost=60+((D/25)*50);
    pipecost=(2000+5*50)/25*1,5;
    pumpandmotorcost=3700+100*ht;
    electricitycost=(0.15*(t/3600)*Ppower);
    yearelectric=electricitycost*730;
    totalcost(iteration)=(elbowcost+valvecost)*5
    ttcst=(pipecost+pumpandmotorcost+electricitycost)*5
    a=totalcost+ttcst
    htVals(iteration)=ht;
    iteration=iteration+1;
    
end
plot(0.1:0.01:0.5,totalhead)
hold on
plot(0.1:0.01:0.5,Ppower)
hold on
plot(0.1:0.01:0.5,a)
hold on

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Rik 2021-5-17

在 MATLAB Online 中打开

This time I edited your question for you. Next time, please use the tools explained on this page to make your question more readable. You should also use the default indentation.

If you had used the debugging tools to step through your code line by line, you would have noticed that Re will be overwritten every iteration. If you want a vector, you will have to index it:

D_list=0.1:0.01:0.5;
Re=zeros(size(D_list));
for n=1:numel(D_list)
    D=D_list(n);
    v=4*flwrt/pi*D;
    Re(n)=(v*D)/0.00000131;
    
    ...
    
end

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Answer 1

David Hill 2021-5-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/832213-i-want-to-calculate-each-v-value-from-each-diameter-value-then-the-value-of-re-one-by-one-and-for#answer_701673

在 MATLAB Online 中打开

No loop needed.

L=(2000+(5*50));
T=5+5*0.25;
It=0.0075*L;
ht=0.15*T;
bt=0.50*It;
e=0.0003*(5+50);
t=15000/sqrt(9.81/ht);
V=It*ht*bt;
flwrt=V/t;
D=0.1:0.01:0.5;
v=4*flwrt/pi*D;
Re=(v.*D)/0.00000131;
f=1.325./(log10(e./D*3.7+5.74./Re.^0.9));
hp=5+5*0.25+(v.^2)/2*9.81.*(f*(2000+5*50)./D+8.1);
totalhead=(v.^2)/2*9.81.*(f*(2000+5*50)./D+8.1);
Ppower=((9.81*1000*flwrt*hp)/1000);
valvecost=320+(D/25)*200;
elbowcost=60+((D/25)*50);
pipecost=(2000+5*50)/25*1.5;
pumpandmotorcost=3700+100*ht;
electricitycost=(0.15*(t/3600)*Ppower);
yearelectric=electricitycost*730;
totalcost=(elbowcost+valvecost)*5;
ttcst=(pipecost+pumpandmotorcost+electricitycost)*5;
a=totalcost+ttcst;
htVals=ht;
plot(D,totalhead);
figure;
plot(D,Ppower);
figure;
plot(D,a);