Indexing into a matrix to create a plot

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Justin Hayes
Justin Hayes el 29 de Mzo. de 2020
Comentada: Justin Hayes el 30 de Mzo. de 2020
I would like to store Tskin for all t values and then use indexing to create a plot. How do I accomplish this?
Tambient = 20; % C
Tfilm = (T + Tambient)/2;
T = 29;
for t = 1:1:10
k_air_2 = 0 * (2.4131 + 0.0078 * T) * 10^-2; % W/m*C = 0
k_cotton = 0; % because long sleeve
rho_air = 1.2893 - 0.004 * Tfilm; % kg/m^3
mu_air = (0.0047 * Tfilm + 1.7164) * 10^-5; % kg/m*s
k_air_ambient= (2.4131 + 0.0078 * Tfilm) * 10^-2; % W/m*C
Re = Diameter_forearm * V * rho_air / mu_air;
h_air = (k_air_ambient/Diameter_forearm) * (0.3 + ((0.62 * Re.^.5 * Pr.^.333)/((1 + (0.4 * Pr)^.667).^.25))*(1 + ((Re/282000).^(5/8))).^.8) % J/s*K*m^2
Uskin = (k_air_2/thickness_air) + (k_cotton/thickness_shirt) + (h_air) % J/s*K*m^2
Uambient = (k_air_ambient/thickness_air) + (k_cotton/thickness_shirt) + (h_air)
old_Tskin = T
Tskin = [(T * Area * Cp_air * rho_air)/(t-(t-1)) + Qgen + (Uambient * Area * Tambient)]/((Area * Cp_air * rho_air / ((t-(t-1)))) + Uskin * Area);
T = Tskin
Tfilm = (T + Tambient)/2;
fprintf('Your frontal forearm temperature is %.2f C after %d seconds ' ,Tskin,t)
dT = old_Tskin - Tskin
if dT > 0.007
display('Your forearm probably feels cold')
elseif dT < -0.005
display('Your forearm probably is probably feeling hot')
else
display ('Your forearm feels comfortable')
end
end
  2 comentarios
Ameer Hamza
Ameer Hamza el 29 de Mzo. de 2020
Several variables in your code are not defined. Please specify the values of all variables.
Justin Hayes
Justin Hayes el 30 de Mzo. de 2020
T = 29; % %C
% Constants
Area = .1/2; % m^2 divide by 2 for the "frontal area", I assume this is 50% of the SA of arm
Qgen = 4.5/2; %J/s divide by 2 for the "frontal area"
thickness_shirt = 0.002286; % m
thickness_air = 0.01 % m thickness of air layer in shirt
k_cotton = 0.04; % W/m*C
Diameter_forearm = 0.07; % m
Tambient = 20; % C
% Properties of ambient air
Pr = 0.71;
V = 5; %m/s
Cp_air = 1006; %J/kg*K
Tfilm = (T + Tambient)/2;
p = input('long-sleeve, short-sleeve, tank, or none: ','s')
for t = 1:1:100
k_air_2 = 0 * (2.4131 + 0.0078 * T) * 10^-2; % W/m*C = 0
k_cotton = 0;
rho_air = 1.2893 - 0.004 * Tfilm; % kg/m^3
mu_air = (0.0047 * Tfilm + 1.7164) * 10^-5; % kg/m*s
k_air_ambient= (2.4131 + 0.0078 * Tfilm) * 10^-2; % W/m*C
Re = Diameter_forearm * V * rho_air / mu_air;
h_air = (k_air_ambient/Diameter_forearm) .* (0.3 + ((0.62 * Re.^.5 * Pr.^.333)/((1 + (0.4 * Pr).^.667).^.25)).*(1 + ((Re/282000).^(5/8))).^.8) % J/s*K*m^2
Uskin = (k_air_2/thickness_air) + (k_cotton/thickness_shirt) + (h_air) % J/s*K*m^2
Uambient = (k_air_ambient/thickness_air) + (k_cotton/thickness_shirt) + (h_air)
Tskin = [(T * Area * Cp_air * rho_air)/(t-(t-1)) + Qgen + (Uambient * Area * Tambient)]/((Area * Cp_air * rho_air / ((t-(t-1)))) + Uskin * Area);
T = Tskin
Tfilm = (T + Tambient)/2
end

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Respuestas (1)

MaryD
MaryD el 29 de Mzo. de 2020
you can just try
T_skin(t)= [(T * Area * Cp_air * rho_air)/(t-(t-1)) + Qgen + (Uambient * Area * Tambient)]/((Area * Cp_air * rho_air / ((t-(t-1)))) + Uskin * Area);
inside the loop.
then outside the loop
t=1:1:10
plot(t,T_skin)
  1 comentario
Justin Hayes
Justin Hayes el 30 de Mzo. de 2020
When I use this method to plot it produces an empty plot

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