Challenge

Parsing NASA thermodynamic data

SSingareddy Sreekesh Reddy19 Aug 2021

Aim: To write a program that extracts 14 coefficients and calculate the specific heat, enthalpy, and entropy of all the given species.

Objectives:

To extract 14 coefficients from the given data file and find specific heat, enthalpy, and entropy for every species
Calculate the molecular weight of each species and display it in the command window
Plot specific heat, enthalpy, and entropy for local temperature range
Save all the plots as images with appropriate names

Inputs:

Global_low_temperature = 300

Global_mid_temperature = 1000

Global_high_temperature = 5000

Formulae:

From data, the first 7 are high-temperature coefficients and the other 7 are low-temperature coefficients

Function program for specific heat:

function [Cp]=specific_heat(T,R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14);

if T

Function program for enthalpy:

function [H]=enthalpy(T,R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14);

if T

Function program for entropy:

function [S]=entropy(T,R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14);

if T

Explanation:

As given, the first 7 coefficients are high-temperature coefficients and the next 7 are low-temperature coefficients, we need to write 2 equations with different coefficients
By using 'if-else' condition, condition the 2 equations for different temperature ranges
Conditioning is done with respect to local_mid_temperature
Similarly, functions for specific heat, enthalpy, and entropy are written

Function program for molecular mass:

function [Mol_wt] = molecule(species)
elements = ['C','H','O','N','S','A'];
At_wt = [12,1,16,14,32,40];
Mol_wt = 0;
for i=1:length(species)
    for j=1:length(elements)
        if strcmp(species(i),elements(j))
            Mol_wt=Mol_wt+At_wt(j);
            n=j;
        end
    end
    m=str2num(species(i));
    if m>1
        Mol_wt=Mol_wt+At_wt(n)*(m-1);
    end
end
end

Explanation:

The function is created by giving the species name as an input
Declare the elements and assign the atomic weights to each element
Use 'for' loop to execute the program throughout the length of species
'strcmp' is used to compare species and elements. If they are characters, we can execute directly, but if they are numbers, we have to cinvert them from string to number
'str2double' is used to convert string to a number

Main program:

clear all
close all
clc

%Reading global temperature values
f1=fopen('THERMO.dat','r');
header=fgetl(f1);

%Global temperatures
global_temperature=fgetl(f1);
T=strsplit(global_temperature,' ');
global_low_temperature=str2num(T{2});
global_mid_temperature=str2num(T{3});
global_high_temperature=str2num(T{4});

%Comments
comment_1=fgetl(f1);
comment_2=fgetl(f1);
comment_3=fgetl(f1);

%Constants
R=8.314;

%Calculating Cp,H,and S
for i=1:inf
    line1=fgetl(f1);
    L1 = strsplit(line1,' ');
    if strcmp(L1(1),'END');
        disp('File is ended');
        break;
    end
    species=L1{1};
    local_low_temperature=str2num(L1{end-3});
    local_mid_temperature=str2num(L1{end-1});
    local_high_temperature=str2num(L1{end-2});
    
    line2=fgetl(f1);
    %extracting the coefficients of line2
    L2=findstr(line2,'E');
    
    c1=str2num(line2(1:L2(1)+3));
    c2=str2num(line2(L2(1)+4:L2(2)+3));
    c3=str2num(line2(L2(2)+4:L2(3)+3));
    c4=str2num(line2(L2(3)+4:L2(4)+3));
    c5=str2num(line2(L2(4)+4:L2(5)+3));
   
    line3=fgetl(f1);
    %extracting the coefficients of line3
    L3=findstr(line3,'E');
    
    c6=str2num(line3(1:L3(1)+3));
    c7=str2num(line3(L3(1)+4:L3(2)+3));
    c8=str2num(line3(L3(2)+4:L3(3)+3));
    c9=str2num(line3(L3(3)+4:L3(4)+3));
    c10=str2num(line3(L3(4)+4:L3(5)+3));
    
    line4=fgetl(f1);
    %extracting the coefficients of line4
    L4=findstr(line4,'E');
    
    c11=str2num(line4(1:L4(1)+3));
    c12=str2num(line4(L4(1)+4:L4(2)+3));
    c13=str2num(line4(L4(2)+4:L4(3)+3));
    c14=str2num(line4(L4(3)+4:L4(4)+3));
   
    %Calculating molecular weight
   [Mol_wt] = molecule(species);
   sprintf('Mol_wt of %s=%d',species,Mol_wt)
    
    T=linspace(local_low_temperature,local_high_temperature,1000);
   for j=1:length(T)
       Cp(j)=specific_heat(T(j),R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14)
       
       H(j)=enthalpy(T(j),R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14)
       
       S(j)=entropy(T(j),R,local_mid_temperature,c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12,c13,c14)
    end
    
  %Plotting Cp vs Temperature
   cp=figure(1);
   plot(T,Cp,'linewidth',3,'color','r');
   xlabel('Temperature')
   ylabel('Specific_heat') 
   
   %Plotting Enthalpy vs Temperature
   h=figure(2);
   plot(T,H,'linewidth',3,'color','b');
   xlabel('Temperature')
   ylabel('Enthalpy')
   
   %Plotting Cp vs Temperature
   s=figure(3);
   plot(T,S,'linewidth',3,'color','r');
   xlabel('Temperature')
   ylabel('Entropy')
   
   %Making folder
   mkdir('Project');
   cd('project');
   mkdir(species);
   cd(species);
   
   %Saving the plots
   saveas(cp,'specific_heat.jpg')
   saveas(h,'enthalpy.jpg')
   saveas(s,'entropy.jpg')
   
   cd ..
   cd ..
   close all
   
end

Explanation:

'THERMO.dat' file is opened using 'fopen' command and it is read using 'r' command
Each line is read separately using 'fgetl' command
The first line is a header line
The second line is the global temperatures line. At first, read the line, then use 'strsplit' command to split the string. Now use 'str2num' command to convert a string to a number. Assign 3 global temperature values i.e. low, mid, and high
Neglect the next 3 lines
Declare the constants
Use 'for' loop such that the program stops executing till the 'END' is reached.
Every species contains 4 lines. From the first line we can extract the local temperatures of each species.
Read the species and extract local temperatures using 'str2num' command
The next three lines consist of coefficients. Extract each line and coefficient separately
After extracting all the 14 coefficients, give the temperature range and no. of values using 'linspace' command
Use 'for' loop to execute the function programs of specific heat, enthalpy, and entropy
Plot the graph for T vs Cp, T vs H, T vs S separately using 'plot' command
Use'mkdir' to make a new directory and use 'cd' to create a directory and it saves all the files in that directory
Also, save the images using 'saveas' command

Screenshot of window where all folders are saved:

Results:

14 coefficients are extracted and are used in program to calculate the values of specific heat, enthalpy, and entropy for different temperature ranges
The graphs for Cp, H, and S are plotted with local temperatures and observed the trend for different ranges
Molecular mass has been calculated and displayed them in a command window

Plots for O2:

Specific Heat