Project 1 - Parsing NASA thermodynamic data

AIM

To write a program in MATLAB to calculate specific heat,enthalpy and entropy for all the species in the given data file. And also to calculate the molecular weight of those species.

GOVERNING EQUATIONS

Equations for specific heat, enthalpy and entropy are as follows,

`C_p/R = a1+a2*T+a3*T^2+a4*T^3+a5*T^4`

`H/(RT) = a1+a2*T/2+a3*T^2/3+a4*T^3/4+a5*T^4/5+(a6)/T`

`S/R = a1*lnT+a2*T+a3*T^2/2+a4*T^3/3+a5*T^4/4+a7`

Where, ‘C_p’ is the specific heat

‘H’ is the enthalpy

‘S’ is the entropy

‘R’ is the universal gas constant

‘T’ is the temperature range

‘a1 - a7’ are the polynomial coefficients

THEORY

In this program we are basically parsing a given set of data. Parsing a file means reading the data inside it and storing the required meaningful data from it.

MATLAB functions used in this program with syntax is given below,

1)For opening a file we use ‘fopen’ function ,which has a syntax as follows,

fileID = fopen(filename,permission)

Where, ‘fileID’ is the name given to that file inside the program

‘filename’ is the original name of the file which has to be opened

‘permission’ specifies the type of access , it is ‘w’ for writing and ‘r’ for reading.

2)Now to read line from a file we use ‘fgetl’ function ,whose syntax is as follows,

fgetl(fileID)

3)To find a string inside a line we use ‘strfind’, whose syntax is as follows,

k=strfind(str,pat)

Where , ‘str’ is the line in which ‘pat’ has to be searched and this returns an output ‘k’ which indicates the starting index of each occurrence of ‘pat’ in ‘str’.

4)To find a numerical value inside a line we use ‘str2double’,whose syntax is as follows,

X=str2double(str) ,which will convert ‘str’ to double precision values and output it as ‘X’.

5)To create an array of temperature range we use ‘linspace’ command,whose syntax is as follows,

y=linspace(x1,x2,n) , which will create an array ‘y’ with ‘n’ evenly spaced value from ‘x1’ to ‘x2’.

6)To save the figure as images we usse ‘saveas’ function ,whose syntax is as follows,

Saveas(fig,filename,formattype) , which will save the figure ‘fig’ with the ‘filename’ and with format specified by ‘formattype’.

7)To read data into a column vector we use ‘fscanf’ function,whose syntax is as follows,

A=fscanf(fileID,formastspec,sizeA) , which will read the data of type specified by ‘formatspec’ from the file ‘fileID’ into a column vector of size mentioned by ‘sizeA’.

8)To perform case insensitive comparison of strings we use ‘strcmpi’,whose syntax is as follows,

tf=strcmpi(s1,s2) , which will compare strings ‘s1’ and ‘s2’ and outputs either 1 if true or 0 if false.

PROGRAM

The first and foremost thing done here is to open the data file stored in the system.

To do that we use the ‘fopen’ function and give that data file a name , which will be used throughout the program here after.

Now to read the first line we have used ‘fgetl’. Each time we use this function it moves to the next line in the data file.

After that we put this line into a row vector using ‘fscanf’ function.

Then we assign the three elements inside this array to corresponding global temperatures.

Next 3 lines in the data file are just comments which we don’t need. So to skip those three lines we type ‘fgetl’ function 3 times and move onto the line after these three.

Now for the input command , which will be asked once the program is run we use ‘prompt’ and ‘input’ function. In this program it asks us to enter the species name once the program is run.

In the data file we have 53 different species present. So we need to run the program 53 times to get all those species. For that we open a for-loop with 53 iterations.

To move to the next line which contains species name and local temperature data we have used ‘fgetl’ .

Now to get the species name the logic used here is , we have used the ‘strfind’ function to search for space in the line. Species name ends before the first space starts so we can equate species name as first character till the character just before the space. This will give us the species name.

We are storing this species name inside an array and then this array is converted to string type in order to facilitate string comparison operation.

Using ‘strcmpi’ function we compare this string with that species name which we will input once the program runs. The output of comparison is stored in an array which contains either ‘1’ if true or ‘0’ if false.

Now in this same line we have local temperature values. To get those we used another logic that is to find any ‘.’ in that line , because the temperature is given with decimals. So the first ‘.’ lies in the first temperature value and so on.

Also we have converted these values to double precision using ‘str2double’ function.

Moving onto the next line using ‘fgetl’, this line is the first of three lines which contains coefficient values.

For getting each coefficient value in this line we have use a logic which will search for ‘E’s’ in the line. Since all coefficient have ‘E’ in it we can use it as a reference and then find the coefficients accordingly.

After getting all the coefficients in that line we move onto the next two lines and repeat the same procedure.

Defining universal gas constant and temperature values(with 100 values using linspace).

After we open another for-loop which runs for the length of temperature array ,which here is 100.

Inside the for loop we open an ‘if conditional statement’ , which checks whether the temperatures are greater than or less than than the local medium temperature and provides two sets of equations for finding specific heat,enthalpy and entropy accordingly.

After that we close this ‘if-else’ statement and also the for loop.

Now we call the molecular function program.

We open another ‘if statement’ which will molecular weight value only if the condition is true.

Inside this we also plot the graph for specific heat,enthalpy and entropy of that species which has been inputted by user after running the program. These figures are stored inside the folder mentioned insid the ‘directory’ function.

These are saved as ‘.png’ file format.

Also the figures are stored in different names to that of other species figures.

Then we closes the ‘if statement’.

Now we have to plot and store the figures of all other 52 remaining species inside the data file.

For that we use different figure names and save these in the same directory used before.

To save these figures with their corresponding species name we have used ‘spritnf’ function inside ‘saveas’ function.

After all these things we close the for loop. This for loop will run for 53 times till all four lines containing data’s regarding the 53 species are read.

To display error message if in case the entered species name is wrong , for that we have created an array with 53 zeroes and compared it to the logical array created earlier inside the for loop.

After finishing all reading process inside the data file we close the file using ‘fclose’ function , which closes an open file.

clear all 
close all
clc

%opening the file and reading the data
f2 = fopen('THERMO.dat','r');

%reading the first line
fgetl(f2);

%converting the first line into a column vector
Line_1 = fscanf(f2,'%f',[1 Inf]);

%reading the global temperature data from the first line
global_low_temp = Line_1(1);
global_med_temp = Line_1(2);
global_high_temp = Line_1(3);

%skipping next 3 lines
fgetl(f2);
fgetl(f2);
fgetl(f2);

%input action specified
 prompt='enter species name : ';
x=input(prompt,'s');

%for loop with 53 iterations
for i =1:53

%reading the line with species name
L1 = fgetl(f2);
%finding species name
A4 = strfind(L1,' ');
species_name= L1(1:A4(1)-1);

%creating an array containing species name
array_name(i) ={species_name};
%converting that char type array into str type array
y = string(array_name);

%logical comparison of strings
tf= strcmpi(y,x);

%finding local temperature values
A1 = strfind(L1,'.');
%assigning local temperature values
t_min = str2double(L1(A1(1)-3:A1(1)+3));
t_high = str2double(L1(A1(2)-4:A1(2)+3));
t_med = str2double(L1(A1(3)-4:A1(3)+3));

%moving to the first line which contains coefficient values
L2 = fgetl(f2);
%finding coefficient and assigning those values 
A2 = strfind(L2,'E');
c1 = str2double(L2(1:A2(1)+3));
c2 = str2double(L2(A2(1)+4:A2(2)+3));
c3 = str2double(L2(A2(2)+4:A2(3)+3));
c4 = str2double(L2(A2(3)+4:A2(4)+3));
c5 = str2double(L2(A2(4)+4:A2(5)+3));

%moving to the second line which contains coefficient values
L3 = fgetl(f2);
%finding coefficient and assigning those values 
A3 = strfind(L3,'E');
c6 = str2double(L3(1:A3(1)+3));
c7 = str2double(L3(A3(1)+4:A3(2)+3));
c8 = str2double(L3(A3(2)+4:A3(3)+3));
c9 = str2double(L3(A3(3)+4:A3(4)+3));
c10 = str2double(L3(A3(4)+4:A3(5)+3));

%moving to the third line which contains coefficient values
L4 = fgetl(f2);
%finding coefficient and assigning those values 
A4 = strfind(L3,'E');
c11 = str2double(L4(1:A4(1)+3));
c12 = str2double(L4(A4(1)+4:A4(2)+3));
c13 = str2double(L4(A4(2)+4:A4(3)+3));
c14 = str2double(L4(A4(3)+4:A4(4)+3));

%specifying R value and temperature range
R = 8.314;
T = linspace(t_min,t_high,100);

%for loop to get the temperature values in the array
for j=1:length(T)
%giving conditions and specifying the formulas accordingly    
if T(j)>t_med
specific_heat = (c1+c2*T+c3*T.^2+c4*T.^3+c5*T.^4)*R;
enthalpy = (c1+c2*(T./2)+c3*((T.^2)./3)+c4*((T.^3)./4)+c5*((T.^4)./5)+c6./T)*R.*T;
entropy = (c1.*log(T)+c2.*T+c3*((T.^2)./2)+c4*((T.^3)./3)+c5*((T.^4)./4)+c7)*R;
else
    specific_heat = (c8+c9*T+c10*T.^2+c11*T.^3+c12*T.^4)*R;
enthalpy = (c8+c9*(T./2)+c10*((T.^2)./3)+c11*((T.^3)./4)+c12*((T.^4)./5)+c13./T)*R.*T;
entropy = (c8.*log(T)+c9.*T+c10*((T.^2)./2)+c11*((T.^3)./3)+c12*((T.^4)./4)+c14)*R;
end 
end

%calling the molecular weight function
molecular_w = molecular_weight(species_name);

% specifying the condition to display molecular weight and plot figures
if tf(i)==1
    fprintf('molecular weight of %s is %d.\n',species_name,molecular_w)
  figure(1)
plot(T,specific_heat,'linewidth',3,'color','r')
title('specific heat of',species_name)
%saving those figures to the specified directories
directory=('C:\Users\user\Documents\MATLAB\specific_heat');
cd(directory)
saveas(figure(1),sprintf('%s.png',species_name));
    
    figure(2)
plot(T,enthalpy,'linewidth',3,'color','g')
title('enthalpy of',species_name)
directory=('C:\Users\user\Documents\MATLAB\enthalpy');
cd(directory)
saveas(figure(2),sprintf('%s.png',species_name));

figure(3)
plot(T,entropy,'linewidth',3,'color','b')
title('entropy of',species_name)
directory=('C:\Users\user\Documents\MATLAB\entropy');
cd(directory)
saveas(figure(3),sprintf('%s.png',species_name));
end

%plotting all other graphs 
figure(4)
plot(T,specific_heat,'linewidth',3,'color','r')
title('specific heat of',species_name)
directory=('C:\Users\user\Documents\MATLAB\specific_heat');
cd(directory)
saveas(figure(4),sprintf('%s.png',species_name));

figure(5)
plot(T,enthalpy,'linewidth',3,'color','g')
title('enthalpy of',species_name)
directory=('C:\Users\user\Documents\MATLAB\enthalpy');
cd(directory)
saveas(figure(5),sprintf('%s.png',species_name));

figure(6)
plot(T,entropy,'linewidth',3,'color','b')
title('entropy of',species_name)
directory=('C:\Users\user\Documents\MATLAB\entropy');
cd(directory)
saveas(figure(6),sprintf('%s.png',species_name));

end

%creating an row vector with 53 zeroes
w=zeros(1,53);
%specifying the condition wrong input species name
if tf==w
    disp('species name entered is wrong')
end

%closing the file
fclose(f2);

MOLECULAR WEIGHT FUNCTION PROGRAM

To calculate the molecular weight of the species we have made a function named ‘molecular_weight’.

We have defined two arrays namely ‘elements’ and ‘atomic_weight’ which contains element names and their corresponding weights.

Next we have initialized molecular weight as zero.

Then we have opened two for loop inside which the ‘species_name’ and ‘elements’ are compared and then then their atomic weight added in the next step.

Also we need to add those numbers in the species name , for that we have converted string to numbers and compared.

After that the values are added to the molecular weight already calculated.

%writing a function to calculate molecular weight
function M = molecular_weight(species_name)
 species = (species_name);
 
 %array with element names
 elements = ['O','H','C','N','A'];
 
 %array with molecular weight of thos elements in the same order
 atomic_weight = [16,1,12,14,40];
 
 %initializing molecular weight value
 M=0;
 
 %for loop to compare species name and elements to find molecular weight
 for i =1:length(species)
     for j =1:length(elements)
     if strcmp(species(i),elements(j))
         M=M+atomic_weight(j)  ;
       y =j;
     end
     end
     %to calculate those elements which occur more than once
     n=str2double(species(i));
     if n>1
         M=M+(atomic_weight(y)*(n-1));
     end
 end
 end
 
    

CONCLUSION

Program in MATLAB to read the data from the given data file and then to plot the specific heat,enthalpy and entropy has been done successfully. Also a function program has been created to find out the molecular weight.