Brayton Cycle T-S and P-V diagram

[Rohit Suresh]

Hello,

I need to plot TS and PV diagram for Brayton Cycle.


The following is my code that I used but I'm not sure if I am storing it correctly or not also I'm somehow not able to plot.

The s1 value when computed by using a calculator does not give a negative value but MATLAB does, don't know why?

%T-S and P-V diagrams
close all; clear all; clc;
format long;
cp=1.0045;
r=0.287; %Specific Gas Constant for Dry Air
k=1.4; %Specific Heat Capacity
ta=288.15;% Inlet Temperature (K)
tc=2000:500:4000; %Combustion Temperature (K)
pa=101325 ; %Inlet Pressure ()
s0=0;

for j=1:5; %tc

%Compressor Temperature
tb=(ta*tc(1,j))^0.5;

%Exit Temperature
td=ta*(tc(1,j)/tb);

%Pressure

pb=pa*((tb/ta)^(k/(k-1)));

pc=pb;

pd=(pa/pb)*pc;

% a=tb/ta(1,i);
% b=pb/pa(1,i);

% Entropy calculation
s1=s0+(cp*(log(tb/ta)))-(r*(log(pb/pa)));

s2=s1+(cp*(log(tc(1,j)/tb)))-(r*(log(pc/pb)));

s3=s2+(cp*(log(td/tc(1,j))))-(r*(log(pd/pc)));


store1(1,j)=tb;
store2(1,j)=td;
store3(1,j)=pb;
store4(1,j)=pc;
store5(1,j)=pd;
store6(1,j)=s1;
store7(1,j)=s2;
store8(1,j)=s3;
end