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.

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

[Rik]

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

Answer 1

[David Hill]

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);