FILE PARSING WITH MATLAB

AIM:

To develop a code to parse the NASA thermodynamic data file to calculate thermodynamic properties of various gas species and obtain thermodynamic property plots along with molecular mass of the desired species. 

INTRODUCTION:

• Parsing: Parsing a file means reading in a data stream and building a memory model of the content of that data. This aims at facilitating perfoming some kind of transformation on the data. Parsing splits a file or other input into pieces of data that can be easily stored or manipulated.

DATA SOURCE:

NASA Thermodynamic data file 

https://drive.google.com/file/d/1AikCHDlz9s_fu8whE81qee_GD4AyYpCP/view

The file contains co-efficients required to evaluate polynomials that can be used to evaluate thermodynamic properties such as  Specific Heat(Cp), Enthalpy (h) and Entropy (S).

FORMULA USED:

Formula used to calculate the thermodynamic properties are as follows:

CODE:

1)Main Part

clear all
close all
clc


%reading data from the file
thermo = fopen('THERMO.dat','r')
fgetl(thermo);
tempdat = fgetl(thermo);
A = strsplit(tempdat,' ');
%Extracting the global temperature range
LowGt = str2num(A{2});
MidGt = str2num(A{3});
HighGt = str2num(A{4});

%Defining variable to store the input from end-user
get = input(' Enter Species Name','s');

while ~feof(thermo)
    data = fgetl(thermo);
    a = strsplit(data,' ');
    b = a(1);
     
    %Comparing input and data of molecule
     match = strcmpi(b , get)
     if match == 1
         disp('Species Data Available')
         %Extracting coefficients of desired moecule
         Line1 = fgetl(thermo);
         SL1 = findstr(Line1,'E');
             Coef1 = Line1(1:SL1(1)+3);
             Coef2 = Line1(SL1(1)+4:SL1(2)+3);
             Coef3 = Line1(SL1(2)+4:SL1(3)+3);
             Coef4 = Line1(SL1(3)+4:SL1(4)+3);
             Coef5 = Line1(SL1(4)+4:SL1(5)+3);
             a1 = str2num(Coef1);
             a2 = str2num(Coef2);
             a3 = str2num(Coef3);
             a4 = str2num(Coef4);
             a5 = str2num(Coef5);

         Line2 = fgetl(thermo);
         SL2 = findstr(Line2,'E');
             Coef6 = Line2(1:SL2(1)+3);
             Coef7 = Line2(SL2(1)+4:SL2(2)+3);
             Coef8 = Line2(SL2(2)+4:SL2(3)+3);
             Coef9 = Line2(SL2(3)+4:SL2(4)+3);
             Coef10 = Line2(SL2(4)+4:SL2(5)+3);
             a6 = str2num(Coef6);
             a7 = str2num(Coef7);
             a8 = str2num(Coef8);
             a9 = str2num(Coef9);
             a10 = str2num(Coef10);
         Line3 =fgetl(thermo);
         SL3 = findstr(Line3,'E');
             Coef11 = Line3(1:SL3(1)+3);
             Coef12= Line3(SL3(1)+4:SL3(2)+3);
             Coef13 = Line3(SL3(2)+4:SL3(3)+3);
             Coef14 = Line3(SL3(3)+4:SL3(4)+3);
             a11 = str2num(Coef11);
             a12 = str2num(Coef12);
             a13 = str2num(Coef13);
             a14 = str2num(Coef14);
             %Extracting the local temperature range of the input molecule
             mlt = a(end-1);
             midlt = str2double(mlt);
             hlt = a(end-2);
             highlt = str2double(hlt);
             llt = a(end-3);
             lowlt = str2double(llt);
            
             break
     elseif match == 0
         disp('Species Data Not Available')
     else
         continue
     end
end

f = upper(get);

%Displaying Molecular Weight of the input molecule.
moleWeight = MW(get);
disp('Molecule Entered')
disp(f)
disp('Molecular Weight')
disp(moleWeight)
TRange = linspace(100,10000,9000);
R = 8.314;
%Obtaining value of SPECIFIC HEAT
cp = specific_heat(a1,a2,a3,a4,a5,a8,a9,a10,a11,a12,midlt,TRange,R);
%Obtaining value of ENTROPY
s = entropy(a1,a2,a3,a4,a5,a7,a8,a9,a10,a11,a12,a14,midlt,TRange,R);
%Obtaining value of ENTHALPY
h = enthalpy(a1,a2,a3,a4,a5,a6,a8,a9,a10,a11,a12,a13,midlt,TRange,R);

%creating directory to store the plots
mkdir(f)
%Plotting Cp v T
figure(1)
plot(TRange,cp,'linewidth',3,'color','r')
grid on
xlabel('Temperature')
ylabel('Specific Heat (J/K)')
title(f)

%Plotting S v T
figure(2)
plot(TRange,s,'linewidth',3,'color','b')
grid on
xlabel('Temperature')
ylabel('Entropy  (J/K)')
title(f)

%Plotting h v T
figure(3)
plot(TRange,h,'linewidth',3,'color','g')
grid on
xlabel('Temperature')
ylabel('Enthalpy (J/kg)')
title(f)

%Defining current folder
cd(f)

%Saving the images to current folder in specified formats
saveas(figure(1),'Cp vs T.jpg')
saveas(figure(2),'S vs T.jpg')
saveas(figure(3),'h vs T.jpg')

%Defining current folder back as parent folder
cd('E:\')
%Closing the open files
fclose('all');

2)Function for Molecular Weight 

%Creating funcion for MOlecular weight
function Mol_Weight = MW(get)
 Weight = 0;
 % input as molecule name 
 % atoms dealt with H C N O Ar
 % atomic mass   1 12 14 16 40 respectively
 %to find molecular weight, we have to compare the atomsbfrom input
 
  atoms = ['H','C','N','O','A'];
  %Only A taken for Ar since A&R will be contained two positions in get
  mass = [1,12,14,16,40];
  %Since we have to compare each characters for mass, using 2 for loop
  for i = 1:length(get)
      for j = 1:length(atoms)
          if strcmpi(get(i),atoms(j))
          Weight = Weight + mass(j);
          y = j;
          end
      end
          %for more number of same atoms in the molecule
          number =  str2num(get(i));
          if (number>1)
          % for c2 we have to add mass of c 2 times
          %initially since for C, mass is added to mol_weight
          % for extra molecule we use (number -1) so adding one more weight
          Weight = Weight + (mass(y)*(number - 1));
          end
  end
  Mol_Weight = Weight;
end

3) Function for enthalpy

function h_val = enthalpy(a1,a2,a3,a4,a5,a6,a8,a9,a10,a11,a12,a13,midlt,TRange,R)
if (TRange>midlt)
   h_val = ( a1+ ((a2 .* TRange)./2) + ((a3.*(TRange.^2))./3) +((a4 .*(TRange.^3))./4) + ((a5 .* (TRange.^4))./5) + (a6./TRange)).* (R.*TRange);
else
    h_val = ( a8+ ((a9 .* TRange)./2) + ((a10.*(TRange.^2))./3) +((a11 .*(TRange.^3))./4) + ((a12 .* (TRange.^4))./5) + (a13./TRange)).* (R.*TRange);
end
end

4)Function for entropy

function s_val = entropy(a1,a2,a3,a4,a5,a7,a8,a9,a10,a11,a12,a14,midlt,TRange,R)

if (TRange>midlt)
    s_val= ((a1*log(TRange)) + (a2 *TRange)  + ((a3*(TRange.^2))/2) + ((a4*(TRange.^3)) /3) + ((a5*(TRange.^4))/4) + (a7))*R;
else
    s_val= ((a8*log(TRange)) + (a9 *TRange)  + ((a10*(TRange.^2))/2) + ((a11*(TRange.^3)) /3) + ((a12*(TRange.^4))/4) + (a14))*R;
end
end

5)Function for specific heat

function cp_val = specific_heat(a1,a2,a3,a4,a5,a8,a9,a10,a11,a12,midlt,TRange,R)

if (TRange>midlt)
cp_val = ( a1+ (a2*TRange) + (a3 *(TRange.^2)) + (a4*(TRange.^3)) + (a5 * (TRange.^4)))*R;
else
    cp_val = ( a8+ (a9*TRange) + (a10 *(TRange.^2)) + (a11*(TRange.^3)) + (a12 * (TRange.^4)))*R;
end
end

Understanding the CODE:

• Initially the given data file is read with help of fopen command with reading function. Then successive lines in the data file is extracted for global temperature range using fgetl command.
• The desired input from the user is stored as a string.
• The input string is then compared with the molecule available in data file using strcmp. If a match is obtained, respective coefficients are extracted from the data file usinf fgetl command. Different co-efficients in a particular line is sorted out by specifyinng the place in that line. Similarly the local temperature range for the input molecule is also extracted from the data file.
• inorder to get the molecular weight, the function for calculating the molecular weight is called and stored to a variable and is displayed.
• Now, for the thermodynamic propety values ( Cp, S, h) , the associated functions are called.
• mkdir command is then used inorder to create a directory to store the ouput figures.
• Now from the different thermodynamic property values, associated Cp v T, S v T and h v T plots are created.
•  Current folder is defined where the figure should be stored and saveas command is used to store the figure to that particular folder created.
• current folder is again defined to make the directory back to parent folder and all the open files are closed with fclose command.

Understanding the Functions

1) Molecular Weight

• A character array is defined for the atoms and array of atomic weights respective to character array is defined.
• The input string is compared with character array, when a match occurs, associated atomic weight is taken.
• For molecules having numbers defining the number of atoms, that number is first extracted, and calculation is made to account for multiple atomic weights.
•  a variable is assigned to store the output value of the function.

2)Enthalpy, Entropy and Specific Heat

• Since the coefficients available in data file is having a temperature constraint, an if condition is used
• First 7 coefficients are high temperature coefficients and last 7 are low temperature coefficients, to calculate the thermodynamic property values, coefficents are selected with reference to temperature range.

OUTPUT:

Some random ouput plots and molecular weight calculation:

PLOT - O2

                                       Cp v T - Plot O2

                                        h v T - Plot O2

                                        S v T - Plot O2

                          Molecular Weight of O2 - Output

PLOT - N2

                                     Cp v T - Plot N2

                                      h v T - Plot N2

                                      S v T - Plot N2

                          Molecular Weight of N2 - Output

PLOT - CO2

                                      Cp v T - Plot CO2

                                      h v T - Plot CO2

                                      S v T - Plot CO2

                          Molecular Weight of CO2 - Output

CONCLUSION:

On successful parsing of data from NASA's Thermodynamic Data file, variation of thermodynamic properties with temperature of certain species of molecules are observed with the help of plots obtained.

REFERENCES:

• https://www.thermal-engineering.org
• https://in.mathworks.com
• https://in.mathworks.com/matlabcentral/answers
• https://www.quora.com
• https://www.cmu.edu
• https://www.thoughtco.com