Project 1 - Parsing NASA thermodynamic data

Parsing NASA thermodynamic data using MATLAB/OCTAVE

Objective: The objective of the project is to write a program which can extract required coefficients from a file containing NASA thermodynamic data, and to calculate parameters such as enthalpy, entropy, molar weight and specific heat, as well as plotting the graphs of the parameters obtained.

Report:

The entire project consists of the main program, which calls multiple functions to extract the coefficients, names, temperatures and plotting the graphs. The project also mostly deals with extracting strings from the data file. A string is an array of characters, just like a matrix is an array of numbers. The difference between a string and a matrix is that a string is stored and assigned a character class (char) within the program, whereas it is (double) fo a matrix. A step wise summary is given below regarding the logic used throughout the project, with each program for the function is explained in every step.

1) Main Program:

%program for parsing NASA thermodynamic data

clear all
close all
clc

R = 8.314;                             %gas constant
f = fopen('THERMO.dat','r');           %opening the file THERMO.dat, and specifying the function to only read the file

for i=1:5;                             %skipping unwanted lines
    skip=fgetl(f);
end

line=0;                                %specifying a counter to count the lines in the file
for i=1:400
    L1 = fgetl(f);                     %keyword to get a line
    
    if strcmp(L1,"END") == 1           %searching for "END" string
        break                          %terminating the loop when the read function reaches the last line
    else
    line = line+1;                     %increment for the counter
    end
end

specie =(line)/4                       %No. of species in the file
frewind(f)                             %rewinds the read function back to the beginning of the file 

folder = 'elements';                   %creating the folder where the plots for the elements are stored
mkdir(folder);                         %specifying the directory for storing the folders

for i=1:5;                             %skipping unwanted lines again
    skip=fgetl(f);
end

for j=1:specie                                       %for loop runs for the no. of species calculated
  [sp_line,species_name] = sp_name(f);               %function for extracting the name of the specie
  [TLOW,THIGH,TMEDIUM] = local_temp(sp_line);        %function for extracting the local temperatures of the specie
  T = linspace(TLOW,THIGH,100);                      %specifying the temperature range for the plots by using the extracted local temps.
  E = coeff(f);                                      %function for extracting the coefficients of the specie in the data file
  CP = spec_heat(TMEDIUM,T,E,R);                     %function for calulating specific heat
  H = enthalpy(TMEDIUM,T,E,R);                       %function for calulating enthalpy
  S = entropy(TMEDIUM,T,E,R);                        %function for calulating entropy
  M = molarw(species_name);                          %function for calulating molar weight
  plots_nasa(T,H,S,CP,species_name,folder);          %function for plotting graphs for the specie using extracted data
end
fclose(f);                                           %closing the file

The main program begins with the standard clear all, close all and clc to clear the workspace, close open windows and clear the command window every time the program is run. The gas constant is specified. The NASA data file is opened in MATLAB using the 'fopen' command. The command asks for the name of the file, which is THERMO.dat, and also asks for the action to be performed on the file, which is read(r). Next, the 'fgetl' command is used to read a line from the file. Every time this command is used, it reads the line below the current one. In the NASA file, the first five lines are extra information to be skipped. So a for loop with fgetl is used to skip the first 5 lines. A counter is assigned as 0. This counter will count the total number of lines in the file. The file has "END" at the bottom of the file. So the for loop is executed in such a way that it terminates when the "END" word is reached. This is detected by using the 'strcmp' command, which compares two strings. When the strcmp gives an output 1 (true condition), the loop terminates using the 'break' keyword. Otherwise the line variable is incremented by 1 till the loop ends. Next, the line output is divided by 4, since each specie has 4 lines, and saved as no. of species. Then the 'frewind' command is used to rewind the read function back to the top of the file. The folder called elements is created to store the specie plots. The unwanted lines are skipped again. Now, using the no.of species, the for loop is executed for calling the required functions such as name extraction, plotting and calculating various parameters, into the main program. Every iteration works for one specie at a time. After the loops are completed, the 'fclose' command is used to close the file.

2) Function for extracting the specie name:

%function for extracting the specie name

function[sp_line,species_name] = sp_name(f)       
sp_line = fgetl(f);                                %specifying the line as a string
species_name = sp_line(1:6);                       %extracting the first 6 elements of the string
end

This function extracts the name of the specie. First, the line is stored as a string. Then the first 6 characters of the string are selected and stored. The longest species name is 6 characters long, and hence the number 6 is considered. For shorter names, the extra blank characters after the name are considered.

3) Function for extracting the local temperatures:

%function for extracting the local temperatures of the specie

function[TLOW,THIGH,TMEDIUM] = local_temp(sp_line)
Y = strsplit(sp_line,'  ');                             %splitting the string at '  ' (double space)
Z = numel(Y);                                           %calculating the number of elements created in stringsplit

if Z == 8                                               
TLOW = str2num(Y{5});                                   %converting the string to numeric value
THIGH = str2num(Y{6});
TMEDIUM = str2num(Y{7});

elseif Z == 9
TLOW = str2num(Y{6});
THIGH = str2num(Y{7});
TMEDIUM = str2num(Y{8});

elseif Z == 10
TLOW = str2num(Y{7});
THIGH = str2num(Y{8});
TMEDIUM = str2num(Y{9});
endif
end

This function extracts the local temperatures (i.e. low, medium and high temperatures) for the specie. First, the 'strsplit' command is used. The command splits the string at specified delimiters. In this case, the delimiter is a double space(' '). So the strsplit command splits the string using the delimiter. Now the string is split into multiple smaller strings and stored in variable 'Y'. Now, the no. of strings of the variable is counted using the 'numel' command. The strings are counted because the no. of strings after splitting the string are not the same for every specie. It varies from 8 to 10. So the if condition is used for all 3 outputs for numel. On finding the correct output of numel, the low, high and medium temperatures are extracted in that order. The 'str2num' command then converts the specific strings that represent the temperature to numeric values(i.e from char to double).

%function for extracting the coefficients from the data file

function[E] = coeff(f)

f1 = fgetl(f);                     %selecting the first line with coefficients
Q = strfind(f1,'E');               %finding 'E' within the string 

%line 1 of coefficients
a1 = f1(1:Q(1)+3);                 %selecting the part of the string representing the first coefficient, using the position of 'E'
A1 = str2num(a1);                  %converting the coefficient from string to numeric value
a2 = f1(Q(1)+4:Q(2)+3);            %second coefficient
A2 = str2num(a2);
a3 = f1(Q(2)+4:Q(3)+3);            %third coefficient
A3 = str2num(a3);
a4 = f1(Q(3)+4:Q(4)+3);            %fourth coefficient
A4 = str2num(a4);
a5 = f1(Q(4)+4:Q(5)+3);            %fifth coefficient
A5 = str2num(a5);

f2 = fgetl(f);                     %selecting the second line with coefficients
R = strfind(f2,'E');               %finding 'E' within the string

%line 2 of coefficients
b1 = f2(1:R(1)+3);                 
B1 = str2num(b1);
b2 = f2(R(1)+4:R(2)+3);
B2 = str2num(b2);
b3 = f2(R(2)+4:R(3)+3);
B3 = str2num(b3);
b4 = f2(R(3)+4:R(4)+3);
B4 = str2num(b4);
b5 = f2(R(4)+4:R(5)+3);
B5 = str2num(b5);

f3 = fgetl(f);                     %selecting the third line with coefficients
S = strfind(f3,'E');               %finding 'E' within the string

%line 3 of coefficients
c1 = f2(1:S(1)+3);
C1 = str2num(c1);
c2 = f2(S(1)+4:S(2)+3);
C2 = str2num(c2);
c3 = f2(S(2)+4:S(3)+3);
C3 = str2num(c3);
c4 = f2(S(3)+4:S(4)+3);
C4 = str2num(c4);

E = [ A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 C1 C2 C3 C4 ];           %storing the values in a matrix

 end

%function for calulating specific heat

function[CP] = spec_heat(TMEDIUM,T,E,R)

%Cp = R(A1 +A2.T + A3.T^2 + A4.T^3 + A5.T^4)

for i = 1:length(T)
  if T(i) <= TMEDIUM
    CP = (E(8) + E(9).*T + E(10).*T.^2 +E(11).*T.^3 + E(12).*T.^4).*R;       %lower temperature range
  else
    CP = (E(1) + E(2).*T + E(3).*T.^2 +E(4).*T.^3 + E(5).*T.^4).*R;          %upper temperature range
  endif
endfor
end

%function for calulating enthalpy

function[H] = enthalpy(TMEDIUM,T,E,R)

%H = RT(A1 +A2.T/2 + A3.T^2/3 + A4.T^3/4 + A5.T^4/5 + A6/T)

for i = 1:length(T)
  if T(i) <= TMEDIUM
    H = (E(8) + E(9).*T./2 + E(10).*(T.^2)./3 +E(11).*(T.^3)./4 + E(12).*(T.^4)./5 + E(13)./T).*R.*T;     %lower temperature range
  else
    H = (E(1) + E(2).*T./2 + E(3).*(T.^2)./3 +E(4).*(T.^3)./4 + E(5).*(T.^4)./5 + E(6)./T).*R.*T;         %upper temperature range
  endif
endfor
end

%function for calulating entropy

function[S] = entropy(TMEDIUM,T,E,R)

%S = R(A1.ln(T) +A2.T + A3.T^2/2 + A4.T^3/3 + A5.T^4/4 + A7)

for i = 1:length(T)
  if T(i) <= TMEDIUM
    S = (E(8).*log(T) + E(9).*T + E(10).*(T.^2)./2 +E(11).*(T.^3)./3 + E(12).*(T.^4)./4 + E(14)).*R;           %lower temperature temperature
  else
    S = (E(1).*log(T) + E(2).*T + E(3).*(T.^2)./2 +E(4).*(T.^3)./3 + E(5).*(T.^4)./4 + E(7)).*R;               %upper temperature range
  endif
endfor
end

%function for calulating molar weight

function[M] = molarw(species_name)

Elements = {'H','C','N','O','AR'};           %elements present in the data file
Atomic_wt = [1 12 14 16 40];                 %atomic weight of the corresponding elements

M = 0;                                       %setting the molar weight as zero
for i = 1:length(species_name)               %for loop to check the characters in the specie name string
  for j = 1:length(Elements)                 %for loop which considers the elements by sequence
    if strcmp(species_name(i),Elements(j))   %comparing element matrix with the name
      M = M + Atomic_wt(j);                  %adding the atomic weight of the element when previous stmt is true
      q = j;
    endif
    endfor
 k = str2num(species_name(i));               %converting the name(string) to number
 if k>1
   M = M + Atomic_wt(q)*(k-1);               %adding atomic weight of elements which are more than one
endif
endfor

disp(species_name)                           %display species name in command window
disp(M)                                      %display molar weight in command window

end

%function for plotting the graphs for the specie

function[P] = plots_nasa(T,H,S,CP,species_name,folder)

d = pwd;                                %specifying the drive for storing the folders
cd(folder);                             %changing directory to folder
Tdata = sprintf('%s',species_name);     %specifying the folder name for the plots
mkdir(Tdata);

%plotting Temperature vs Enthalpy
figure(1)                               
plot(T,H,'linewidth',3,'color','g')
title(species_name)
xlabel('Temperature')
ylabel('Enthalpy')

%plotting Temperature vs Entropy
figure(2)
plot(T,S,'linewidth',3,'color','b')
title(species_name)
xlabel('Temperature')
ylabel('Entropy')

%plotting Temperature vs Specific Heat
figure(3)
plot(T,CP,'linewidth',3,'color','r')
title(species_name)
xlabel('Temperature')
ylabel('Specific Heat')

%saving the plots as png files
cd(Tdata)
saveas(1,'Enthalpy.png')
saveas(2,'Entropy.png')
saveas(3,'Specific_heat.png')
cd(d)
end