Value in Array does not Change

I'm simulating a Heat Exchanger Model with the HED Matrix in the program as discretized Heat Exchanger. The 1st row is the hot fluid matrix and 2nd row is the cold fluid matrix. The calculation is in a loop of timesteps. The temperature of the fluid changes as per the loss in enthalpy. But the temperature of the cold fluid does not change at all, it decreases at some timesteps when it should strictly increase. You can view the results at different time steps by tweaking the for loop with 't/j'. I have commented on the program, I'm stuck only on this, since the other part of program seems fine.

t = 25;   % L/((m/rho)/CSArea); %Time for the fluid to cross Heat Exchanger
%Heat Transfer Coefficients
Hhot = 0.340;
Hcold = 0.400;
A = 1;
Cpcold = 4.179;
Cphot = 4.208;
%Initial Temperatures
Th = 363;
Tc = 303;
%number of fluids i
i = 1;
%discretization level; number of blocks fluid to be divided into j;
j = 100;
HED = zeros(i,j);
n=5; %timesteps
for j= 1:1:j
        HED(i,j) = Th;
        HED(i+1,j) = Tc;
end
    Qrate = zeros(i,j);

for m = t/j:t/j:j*t/j

      j=100;
      for j =1:1:j
          Qrate(i,j) = Hhot * A * (HED(i,j)-HED(i+1,j));   %Heat transfer Rate
      end

          Q1 = times(Qrate,t/j);    %Heat transferred in timestep

      for j = 0:1:j-1

          %New Temperature of Cold Water after Heat Transfer
          HED(i+1,j+1) = HED(i+1,j+1) + (Q1(i,j+1)/Cpcold); 
          %New Temperature of Hot Water after Heat Tranfer
          HED(i,j+1) = HED(i,j+1) - (Q1(i,j+1)/Cphot); 
      end
      for j=0:1:j-1
              HED(i,j+1)=HED(i,j+2);   %shifting row of hot fluid Row 1
              HED(i+1,j+2)=HED(i+1,j+1);    %shifting row of cold fluid Row 3
      end
      j=100;
      HED(i,j) = Th;
      HED(i+1,1) = Tc;
end

[the cyclist]

The way that you use j as a constant and as a looping variable (and as the endpoint of that looping variable) is pretty confusing, and possibly the source of your bug. (MATLAB may interpret that correctly, but I'm not sure.)

Answer 1

[the cyclist]

This is a guess, because I have not run your code, but is the very last line right?

HED(i+1,1) = Tc;

Is that "1" right, or should it be j?

[Vishakh Ranade]

Thanks for your review, actually I figured the problem out soon. The problem was in the 'shifting row of cold" part. the problem was: 1st iteration : HED(2,2)=HED(2,1) 2nd iteration : HED(2,3)=HED(2,2) So the same value would be copied through the entire matrix.