Project 1 - Parsing NASA thermodynamic data

Objective:To obtain thermodynamic data for various species, and the coefficients of temperature in the characteristic equations for entropy, enthalpy and specific heat using a matlab code.

The equations are as follows:

Specific heat equation:

Cp = R*(a1 + (a2*T) + (a3*(T.^2)) + (a4*(T.^3)) + (a5*(T.^4)))

Enthaply equation

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

Entropy equation

S = R*((a1*log(T)) + (a2*T) + (a3*(T.^2)/2) + (a4*(T.^3)/3) + (a5*(T.^4)/4) + a7)

14 coefficients are obtained from the thermodynamic data file of which the firrst 7 are used in low temperature conditions and the latter 7 are used for high temperature conditions. The temperature for each species is mentioned in the data file with a maximum and minimum limit as well as a median limit. For temperatures above the median limit, the high temperature coecients are used and for temperatures below the median limit, the low temperature coefficients
are used.

MATLAB CODE:

clear all
close all
clc
f1 = fopen('THERMO.dat', 'r');
tline = fgetl(f1);
%Universal gas constant(J/K mol)
R = 8.314;
%Loop to run the first 4 lines of the data file
for i = 1:4

 fgetl(f1);

end
%Loop to obtain data and get the plots for each species
for i = 1:53

 %Obtaining the name of the species and converting to a string value
 %for convenience
 tline1 = fgetl(f1);
 a = strsplit(tline1, ' ');
 species_cell = a(1);
 species = char(species_cell);

 %Finding the local values of temperature for each species
 str1 = strfind(tline1, '.');
 low_temp_range = str2num(tline1(str1(1)-4:str1(1)+3));
 high_temp_range = str2num(tline1(str1(2)-4:str1(2)+3));
 med_temp_range = str2num(tline1(str1(3)-4:str1(3)+3));

 %Obtaining the coefficients from the subsequent three lines
 tline2 = fgetl(f1);
 str = strfind(tline2, 'E');
 a1 = str2num(tline2(1:str(1)+3));
 a2 = str2num(tline2(str(1)+4:str(2)+3));
 a3 = str2num(tline2(str(2)+4:str(3)+3));
 a4 = str2num(tline2(str(3)+4:str(4)+3));
 a5 = str2num(tline2(str(4)+4:str(5)+3));

 tline3 = fgetl(f1);
 a6 = str2num(tline3(1:str(1)+3));
 a7 = str2num(tline3(str(1)+4:str(2)+3));
 a8 = str2num(tline2(str(2)+4:str(3)+3));
 a9 = str2num(tline3(str(3)+4:str(4)+3));
 a10 = str2num(tline3(str(4)+4:str(5)+3));

 tline4 = fgetl(f1);
 a11 = str2num(tline4(1:str(1)+3));
 a12 = str2num(tline4(str(1)+4:str(2)+3));
 a13 = str2num(tline4(str(2)+4:str(3)+3));
 a14 = str2num(tline4(str(3)+4:str(4)+3));

 %a1-a7 are low temperature coefficients, a8-a14 are high temperature
 %coefficients

 %Calculating molecular weight of each species
 Molecular_weight = m_wt(species);
 sprintf('Molecular weight of %s = %d',species, Molecular_weight)

 %Defining T
 T = low_temp_range:high_temp_range;

 %Obtaining the values for Cp, enthalpy and entropy using the coefficients
 if (T>med_temp_range)
 %specific heat
 Cp = R*(a1 + (a2*T) + (a3*(T.^2)) + (a4*(T.^3)) + (a5*(T.^4)));
 %Enthaply
 H = R*(a1 + (a2*T/2) + (a3*(T.^2)/3) + (a4*(T.^3)/4) + (a5*(T.^4)/5) + (a6*(T)));
 %Entropy
 S = R*((a1*log(T)) + (a2*T) + (a3*(T.^2)/2) + (a4*(T.^3)/3) + (a5*(T.^4)/4) + a7);

 else

 %specific heat
 Cp = R*(a8 + (a9*T) + (a10*(T.^2)) + (a11*(T.^3)) + (a12*(T.^4)));
 %Enthaply
 H = R*(a8 + (a9*T/2) + (a10*(T.^2)/3) + (a11*(T.^3)/4) + (a12*(T.^4)/5) + (a13*(T)));
 %Entropy
 S = R*((a8*log(T)) + (a9*T) + (a10*(T.^2)/2) + (a11*(T.^3)/3) + (a12*(T.^4)/4) + a14);


 end
 %Creating the folder for the species
 t = sprintf('%s', species);
 mkdir(t);

 %Going in to the folder of the species to save the plots
 cd(t)


 %Plotting the curves
 %Cp v temperature plot
 figure(1)
 plot(Cp,T, 'b','linewidth',3);
 xlabel('specific heat')
 ylabel('Temperature')
 Cp_text = sprintf('Specific heat v temperature for %s', species);
 title(Cp_text);
 saveas(gcf, 'Cp.jpg');

 %Enthalpy v temperature plot
 figure(2)
 plot(H, T, 'r','linewidth',3);
 xlabel('Enthalpy')
 ylabel('Temperature')
 H_text = sprintf('Enthalpy v temperature for %s', species);
 title(H_text);
 saveas(gcf, 'H.jpg');

 %Entropy v temperature plot
 figure(3)
 plot(S, T, 'g','linewidth',3);
 xlabel('Entropy')
 ylabel('Temperature')
 S_text = sprintf('Entropy v temperature for %s', species);
 title(S_text);
 saveas(gcf, 'S.png');

 %Going back to the previous directory
 cd ..;

end

A separate function is used to determine the molecular weights of each species:

function [out] = m_wt(spec)
%Defining the elements
elements=['H','C','N','O','R'];

%Atomic weights of each element
Atomic_Weight = [1 12 14 16 40];
out=0;
%Looping for each element inside each species and finding the atomic weight
for i=1:length(spec)
 for j=1:length(elements)
 if strcmp(spec(i),elements(j))
 out= out + Atomic_Weight(j);
 p=j;
 end
 end

 %loop to multiply the coefficients of the elements if greater than 1.
 n=str2double(spec(i));
 if n>1
 out = out + (Atomic_Weight(p))*(n-1);
 end
end
end

EXPLANATION-
1. The program uses the following commands 'fopen' command opens the thermodynamic data file [therm.dat]and stores it to a file Id called 'f1'. 'fgetl' of f1
command takes the value of the first line of the therm.dat file.

2. The 2nd line in the file represents global temperatures, thus the values are stored for temperature calculations.

3. Since the temperatures are inside the string we use 'strsplit' command that splits the string in the specied delimiter, here ' ' (space) is the delimiter, after
splitting the values are assigned to variables ( global low, mid and high temperatures), using 'str2double' command string value is converted to the
numeric value.

4. A temperature range with 500 values between global high and low temperature is made by using 'linspace' command, the number of values is specified
by 'linspace' command.

5. Preallocations are made to store the properties or data of all the elements present in the file.

6. Then skipping the 3 comment lines present in the therm.dat le, which has command 'fgetl of f1'.

7. Command 'cd(pwd)' opens a present working directory. 'mkdir' command makes a new folder with the name specified inside brackets.

8. A folder named 'Elements' is created in the working directory which is used to store all the related output les of the program.

9. Command 'cd()' makes the new folder as the directory. At last, a 'for' loop must run 'j' times, where j is a number of elements.

10. After the loop gets executed, cd .. is used to get back to the original directory.

MOLECULAR WEIGHT OF SPECIES.

Screenshot of the directory where different Species are saved:

FINAL RESULTS-

Plots for O2

Plots for N2

Plots for CO2

Conclusion:

• The characteristic curves for all the species are obtained.
• N2 and O2 follow the same general pattern with the only difference being that O2 gives out energy (positive enthalpy) and N2 takes in energy (negative
  enthalpy). Their relation to Temperature is as expected as they follow a parabolic path for Cp and S and a linear plot for H since Cp and S are inversely
  proportional to temperature and H is directly proportional to it.