how to plot graph for U wrt L_lime from 0.001 to 0.003 with differance 0.001? getting error using / matrix dimension must agree. the value of L_lime changes U value

di=0.01;
do=0.025;
hi=5000;
m_dot = 0.3;

k= 0.598;
rho=998;
knew=1.004*10^-6;
pr=7.01;

dh=do-di

dh = 0.0150

Ac = pi*((do^2)-(di^2))/4

Ac = 4.1233e-04

vel=m_dot/(rho*Ac)

vel = 0.7290

Re=(vel*dh)/knew

Re = 1.0892e+04

if Re>4000
    Nu=0.023*(Re^0.8)*(pr^0.4)
end

Nu = 85.0539

ho= (k*Nu)/dh

ho = 3.3908e+03

k_lime=1.3;
L_lime = [0.001:0.003:0.0001];
U=(1/((1/hi)+(L_lime/k_lime)+(1/ho)))

Error using /
Matrix dimensions must agree.

Answer 1

[Diwakar Diwakar]

To perform the division between L_lime and k_lime, you need to ensure that their dimensions match. If you want to divide each element of L_lime by k_lime, you can use element-wise division by adding a dot before the slash operator.

Try this code:

di = 0.01;
do = 0.025;
hi = 5000;
m_dot = 0.3;
k = 0.598;
rho = 998;
knew = 1.004 * 10^-6;
pr = 7.01;
dh = do - di;
Ac = pi * ((do^2) - (di^2)) / 4;
vel = m_dot / (rho * Ac);
Re = (vel * dh) / knew;

if Re > 4000
    Nu = 0.023 * (Re^0.8) * (pr^0.4);
else
    Nu = 0;  % Set Nu to zero if Re is not greater than 4000
end

ho = (k * Nu) / dh;

k_lime = 1.3;
L_lime = 0.001:0.003:0.0001;
U = (1 ./ ((1 ./ hi) + (L_lime ./ k_lime) + (1 ./ ho)));

[SHARVARI]

Thank you. it works now