Challenge

Parsing NASA Thermodynamic Data

BBalayogi Ip11 May 2021

AIM

To write a function that extracts the 14 co-efficients and calculates the enthalpy, entropy and specific heats for all the species in the given data file

OBJECTIVE

Code a function to get 14 co-efficients of given species from the given data
Code a function to calculates the thermodynamic properties of Specific heat, enthalpy, entropy for each given species
Code a function to plots for each given species by the values has got from the calculation of thermodynamic properties
Code a function to make a folder to save the plots of each species
Code a function to calculates the molecular weight of each species

FILE PARSING

Parsing a file means nothing but a syntax analyzer which can reading and converting it into a form which can be used for computations. This aims at facilitating perfoming some kind of transformation on the data
From the input file, we can see the data in the form of text

It will be able to,

Split a string using a delimeter
Remove the whitespace around the string
Convert the datatypes of variables from one type to other

THERMODYNAMIC PROPERTIES

In order to carry through a program of finding the changes in the various thermodynamic functions that accompany reactions, such as specific heats, enthalpy and entropy

Specific Heat [Cp]

Specific heat refers to the ratio of the quantity of heat that we require to raise the temperature of a body by one degree that we need to increase the temperature of an equivalent mass of liquid (water) by one degree
Also, we use the term in a narrower sense to mean the amount of heat, in calories that we require to raise the temperature of one gram of a substance by one Celsius degree
In simple words, it is the ratio of the amount of heat required to increase the temperature of an object by one degree to the amount of heat required to increase the temperature of the same amount of water by one degree
Specific heat is also known as specific heat capacity or mass specific heat

`c_p=(DeltaQ)/(m*DeltaT)`

where,

`c_p`= Specific heat

`DeltaQ`= Heat energy

`m`= Mass of the object or substance

`DeltaT`= Change in temperature

Enthalpy [H]

Enthalpy is representing the heat content of a system. It is a common fact that the heat can go in or out of the system. Enthalpy is the measurement of the energy of some chemical reactions in a thermodynamic system, the change of heat is defined as enthalpy change
This knowledge about the increase or decrease of the enthalpy of the system during a chemical reaction is a very crucial factor for understanding the reaction. Also, the change in the enthalpy of the system during a chemical reaction is termed as the sum total value of change in its internal energy and the change in the product of the pressure and volume of the system
It is also equivalent to the sum total of the system’s internal energy product of volume and pressure. Enthalpy describes the internal energy needed to generate a system

`H=U+pV`

where,

`U`= Internal energy

`p`= Pressure

`V`= Volume

When a process begins at some constant pressure, then heat will be evolved, either absorbed or released and it equals the change in enthalpy. Therefore Enthalpy change is the sum of internal energy denoted by E and product of volume and Pressure, denoted by P × V

Entropy [S]

Entropy is a scientific concept, as well as a measurable physical property that is most commonly associated with a state of disorder. Any type of medium either solid or fluid always consists of molecules. The measurement of the randomness of molecules in the system is called entropy
Therefore, if the randomness of molecules is more, then there will be more increase in entropy of the process. And as a result, the percentage of heat which may be converted into work will be less. Thus, we may say that entropy is a function of the quantity of heat
It's simple, it is just a measurement of how much randomly the molecules are moving in a system. In solids, the molecules are properly arranged, which means it has less randomness, so the entropy of solids is least. In gases, the molecules move very fast throughout the container. It has more randomness which means it has entropy. The entropy of liquids lies in between the solids and liquids

`DeltaS=(DeltaQ)/T`

where,

`DeltaS`= Change in entropy

`DeltaQ`= Heat energy

`T`= Temperature

FORMUALE USED

`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.ln.T+a2.T+a3.T^2/2+a4.T^3/3+a5.T^4/4+a7`

where,

`C_p`= Specific heat (J/Kg.K)

H = Enthalpy (J)

S = Entropy (J/K)

`a1-a7`= Low temperature co-efficient

`a8-a14`= High temperature co-efficient

T = Temperature (T)

R = Universal gas constant (J/mol.K)

PROGRAM

clear all
close all
clc

%Getting the Data File
f1 = fopen('THERMO.dat','r');

%To find the total no.of species
string = fgetl(f1);
i = 1;
while strcmp(string,'END') ==  0
    string = fgetl(f1);
i = i+1;
end

total_lines = i;
total_species = (total_lines-6)/4;
% On above commands are used only to find out the total no.of species in the given data file

%So we  have to reopen the Data File for further steps
f1 = fopen('THERMO.dat','r');
fgetl(f1);

%Reading the header information to get the global temperatures
A = fgetl(f1);
B= strsplit(A,' ');

global_low_temp = str2double(B{2});
global_mid_temp = str2double(B{3});
global_high_temp = str2double(B{4});

%Skipping next 3 Lines
for j = 1:3
    fgetl(f1);
end

%Reading the Species Data
for i = 1:total_species
    line_1 = fgetl(f1);
    x = strsplit(line_1,' ');
    species_name = x{1};
    z = length(x);
    
    %Subtract from right side to left side in z
    local_low_temp = str2double(x(z-3));
    local_high_temp = str2double(x(z-2));
    local_mid_temp = str2double(x(z-1));
    
    t1 = local_low_temp;
    t2 = local_mid_temp;
    t3 = local_high_temp;
   
%2nd Line Co-efficients of a1-a5
    line_2 = fgetl(f1);
    a = strfind(line_2,'E');
    a1 = str2double(line_2(1:a(1)+3));
    a2 = str2double(line_2(a(1)+4:a(2)+3));
    a3 = str2double(line_2(a(2)+4:a(3)+3));
    a4 = str2double(line_2(a(3)+4:a(4)+3));
    a5 = str2double(line_2(a(4)+4:a(5)+3));
    
%3rd Line Co-efficients of a6-a10
    line_3 = fgetl(f1);
    a = strfind(line_3,'E');
    a6 = str2double(line_3(1:a(1)+3));
    a7 = str2double(line_3(a(1)+4:a(2)+3));
    a8 = str2double(line_3(a(2)+4:a(3)+3));
    a9 = str2double(line_3(a(3)+4:a(4)+3));
    a10 = str2double(line_3(a(4)+4:a(5)+3));
    
%4th Line Co-efficients of a11-a14
    line_4 = fgetl(f1);
    a = strfind(line_4,'E');
    a11 = str2double(line_4(1:a(1)+3));
    a12 = str2double(line_4(a(1)+4:a(2)+3));
    a13 = str2double(line_4(a(2)+4:a(3)+3));
    a14 = str2double(line_4(a(3)+4:a(4)+3));
    
%Calculate Specific Heat, Enthalpy, Entropy w.r.t Temperature
        T = linspace(t1,t3,50);     %Temperature(K)
        R = 8.314;                  %Universal gas constant(J/mol.K)
    for j = 1:length(T)
        if T(j)>t2
            C_p(j) = (a1+(a2.*T(j))+(a3.*T(j).^2)+(a4.*T(j).^3)+(a5.*T(j).^4))*R;
            H(j)= (a1+(a2.*T(j)/2)+(a3.*(T(j).^2)/3)+(a4.*(T(j).^3)/4)+(a5.*(T(j).^4)/5)+(a6./T(j)))*R.*T(j);
            S(j) = ((a1.*log(T(j)))+(a2.*T(j))+(a3.*(T(j).^2)/2)+(a4.*(T(j).^3)/3)+(a5.*(T(j).^4)/4)+a7)*R;
        
        else
            C_p(j) = (a8+(a9.*T(j))+(a10.*T(j).^2)+(a11.*T(j).^3)+(a12.*T(j).^4))*R;
            H(j)= (a8+(a9.*T(j)/2)+(a10.*(T(j).^2)/3)+(a11.*(T(j).^3)/4)+(a12.*(T(j).^4)/5)+(a13./T(j)))*R.*T(j);
            S(j) = ((a8.*log(T(j)))+(a9.*T(j))+(a10.*(T(j).^2)/2)+(a11.*(T(j).^3)/3)+(a12.*(T(j).^4)/4)+a14)*R;
        end
    end
    
%Plotting Specific Heat, Enthalpy, Entropy w.r.t Temperature
    figure(1)
    plot(T,C_p,'linewidth',3,'color','r')
    title('Species Name:',species_name)
    xlabel('Temperature(K)')
    ylabel('Specifc Heat(J/Kg.K)')
    grid on
    figure(2)
    plot(T,H,'linewidth',3,'color','g')
    title('Species Name:',species_name)
    xlabel('Temperature(K)')
    ylabel('Enthalpy(J)')
    grid on
    figure(3)
    plot(T,S,'linewidth',3,'color','b')
    title('Species Name:',species_name)
    xlabel('Temperature(K)')
    ylabel('Entropy(J/K)')
    grid on

%Creating folder for each species  
    mkdir(['D:Skill LyncTemp Program 1File Parsing',species_name]);
    cd(['D:Skill LyncTemp Program 1File Parsing',species_name]);
    saveas(1,'Specific Heat.png')
    saveas(2,'Enthalpy.png')
    saveas(3,'Entropy.png') 

%Calculate molecular weight for each species
elements=['H','C','O','N','A'];
atomic_weight=[1.0079 12.0107 15.999 14.0067 39.948];
mol_mass=0;
for l=1:length(species_name)
    for m=1:length(atomic_weight)
        if strcmp(species_name(l),elements(m))
            mol_mass=mol_mass+atomic_weight(m);
            position=m;
        end
    end
    
 %Multiply the molecular weight into no.of atoms for each species
n=str2double(species_name(l));
if n>1
    mol_mass=mol_mass+atomic_weight(position)*(n-1);
    
end
end

%Display the molecular weight for each species in command window
fprintf('Molecular Weight of %s: %f amun',species_name,mol_mass)

end

fclose(f1);

CODE PROCEDURE

First of all, we need to download the "THERMO.dat" file of NASA thermodynamic data from the given link
Use the 'fopen' command to open the 'THERMO.dat' file to read the given data
To find the total number of species, code a 'while-loop' function with 'strcmp' command has used to compare the string 'END' word where mentioned in the given data file
Based on the above code to find the total lines in the data file, then calculate the total species as subtracting total lines by eliminating the unwanted 6 lines(1st five lines and the last line) and divided by 4(which means each species had 4 lines)

Above these all coded only for the calculations of total lines and total species of the given data file, now we going to code for main part of this file parsing program
Let use the 'fopen' command again to open the 'THERMO.dat' file to read the given data and use the 'fgetl' command to read the first line of the file
After that use same 'fgetl' command to read the header information(global temperatures)
Use 'strsplit' command to split the string by the specified delimeters(' ')
Assign the splitted line in 'y', then get the global temperatures(low, mid, high) by subtracts the cell position from right to left side for each
After that skip the 3 unwanted lines by using 'for-loop' function

From the above picture, Read the species data as line wise from 'line_1' by use 'fgetl' command, then use 'strsplit' command to split the string by the specified delimeters(' ')
Then call the 'line_1' as 'x' and call the 'species_name' from the 1st cell of x. Assign the splitted line in 'z', then get the local temperatures(low, mid, high) by subtracts the cell position from right to left side for each
Assign the 3 local temperatures in t1, t2, t3 and after that read all the 14 co-efficients as given in that specified species by 'fgetl' command as line-wise(line_2 to line_4)
Use 'strfind' command to find strings within other strings by the specified delimeters('E')
Use 'str2double' command to convert the strings into values to get the each co-efficients and assign in a1 - a14
Now we have to calculate the specific heat, enthalpy, entropy with respect to Temperature(`T`)
Use the'linspace' command to generate 50 evenly spaced points between two values(t1 and t3) in 'T' and assign 'R' an universal gas constant
Then use the 'Nested for-loop' and 'if-else' function to calculate the specific heat, enthalpy, entropy by the given formula
Here we have to plot the each figures, before that we have to use the 'figure' command to create figure window for each thermodynamic properties
Now use 'plot' command to plots the 3 required thermodynamic properties(`c_p,H, S`) with temperature(`T`) and with color, linewidth, labels, title commands for each
Use 'mkdir' command to create the folder for each species and use 'cd' command to change the current folder to the new created folder. In this both command we have to provides the same path as where we going to save these files
Here use 'saveas' command to save the figures of each properties on each species folders under the specific file format
Then calculate molecular weight for each species by 'nested loop' and 'if' function here analyse the given data file and find out the type of moleculars in it, after that mention those and assign that in elements

Then provide the values of moleculars what you got and assign it in atomic weight

In this 'if' function, 'strcmp' command has used to compare the strings of species name with elements, if it results TRUE then molecular mass will calculated as per the appropriate species
And the result of molecular mass has been multiplied with the number of atoms for each species by the 'if' function
Finally, 'fprintf' command has used to display the molecular weight for each species in command window

PLOT DIAGRAM

1. For O2