Project 1 - Parsing NASA thermodynamic data

Parsing NASA Thermodynamic Data

Aim:

To write a code in Matlab/Octave to parse the NASA thermodynamic data file and then calculate thermodynamic properties of various gas species.

Objectives:

To write a function that extracts the 14 co-efficients for a given species from the given file.

To write functions that calculate the enthalpy, entropy and specific heats using the NASA polynomials.

To write a function that calculates the molecular weight of each species.

To write a function that plots the Cp, Enthalpy and Entropy of an input species.

Introduction: Parsing is the process of breaking a data block into smaller chunks by following a set of rules, so that it can be more easily interpreted, managed, or transmitted by a computer. NASA came up with polynomials that can be used to evaluate thermodynamic properties such as Cp, H and S using polynomials. They have also documented the co-efficients that are required to evaluate these polynomials for 1000+ species.

Procedure:

The value of the universal gas constant R is given as 8.31 as an input.Then the given THERMO.dat file has to be accessed to obtain the necessary data 'fopen' command is used to open the desired file and the keyword 'r' is used to read the file.This THERMO.dat file is assigned to a variable 'f1'The file is read line by line by using the 'fgetl' command. The first line represents the title of the file so it is ignored.The second line has the global maximum, global mid and global minimum values which is split into the three values by using the strsplit command and converted into numbersAn array of temperature is generated using linspace commandThe next 3 lines are ignored as they contain only commands. A for loop is employed.Again a for loop is created to read the data of all the species. fgetl command inside the for loop makes our task easier Then the next 3 lines of the file is read which contains the high and low temperature data of the particular species.The read lines are in the form of a string so they are converted into numbers using the str2num command and stored in specific variables so they can be used for further calculations.The low temperatures values are stored in variables lc1,lc2,lc3,lc4,lc5,lc6 and lc7 and the high temperature values are stored invariables hc1,hc2,hc3,hc4,hc5,hc6 and hc7.The next part of the program contains a for loop with formulas to calculate Specific Heat, Enthalpy and Entropy for lower temperatures given T<=t.An else command is used to calculate the thermodynamic properties at higher temperature if the temperature fails to satisfy the criteria given abovePlot of Specific Heat vs Temperature is plotted Plot of Enthalpy vs Temperature is plottedPlot of Entropy vs Temperature is plottedUsing the saveas command the three figures are saved in the new folder which is created by the element name.Using the "cd" command the folder is back to the original folder.The function runs for 52 times through the for loop and it creates seperate folders for each species and saves all the plots in the folders.Molecular Weights of different species is calculated.

NASA polynomial:

Specific heat(Cp)=The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius .

Entropy(H)=The entropy of an object is a measure of the amount of energy which is unavailable to do work.

Enthapy(S)=a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.

Writing the main program:

clear all 
close all
clc

%universal gas constant
R=8.31;

f1=fopen('THERMO.dat','r')
line1=fgetl(f1)

%initial lines
for i=1:4
    fgetl(f1)
end
T=linspace(300,5000,500);
for i=1:52
line=fgetl(f1)


A=strsplit(line,' ')
species=A(1)


line2=fgetl(f1)
sf=strfind(line2,'E')
cf1=line2(1:sf(1)+3)
cf2=line2(sf(1)+4:sf(2)+3)
cf3=line2(sf(2)+4:sf(3)+3)
cf4=line2(sf(3)+4:sf(4)+3)
cf5=line2(sf(4)+4:sf(5)+3)

line3=fgetl(f1)
cf6=line3(1:sf(1)+3)
cf7=line3(sf(1)+4:sf(2)+3)
cfe1=line3(sf(2)+4:sf(3)+3)
cfe2=line3(sf(3)+4:sf(4)+3)
cfe3=line3(sf(4)+4:sf(5)+3)

line4=fgetl(f1)
cfe4=line4(1:sf(1)+3)
cfe5=line4(sf(1)+4:sf(2)+3)
cfe6=line4(sf(2)+4:sf(3)+3)
cfe7=line4(sf(3)+4:sf(4)+3)
 
%high temperature coefficients
hc1=str2num(cf1);
hc2=str2num(cf2);
hc3=str2num(cf3);
hc4=str2num(cf4);
hc5=str2num(cf5);
hc6=str2num(cf6);
hc7=str2num(cf7);
lc1=str2num(cfe1);
lc2=str2num(cfe2);
lc3=str2num(cfe3);
lc4=str2num(cfe4);
lc5=str2num(cfe5);
lc6=str2num(cfe6);
lc7=str2num(cfe7);

%low temperature coefficiemts
lc=[lc1 lc2 lc3 lc4 lc5 lc6 lc7];
hc=[hc1 hc2 hc3 hc4 hc5 hc6 hc7];
 for j=1:length(T)
    t=1000;
    if T(j)<=t
        
        Cp(j) = R*(lc(1)+lc(2)*T(j)+lc(3)*(T(j))^2 +lc(4)*(T(j))^3 +lc(5)*(T(j))^4);
         H(j) = R*T(j)*(lc(1)+lc(2)*T(j)/2 +lc(3)*((T(j))^2)/3 +lc(4)*((T(j))^3)/4 + lc(5)*((T(5))^4)/5 + lc(6)/T(j));
         S(j) = R*(lc(1)*log(T(j))+lc(2)*T(j)+lc(3)*((T(j))^2)/2 +lc(4)*((T(j))^3)/3 + lc(5)*((T(j))^4)/4 + lc(7));
         
    else
        Cp(j) = R*(hc(1)+hc(2)*T(j)+hc(3)*(T(j))^2 +hc(4)*(T(j))^3 +hc(5)*(T(j))^4);
         H(j) = R*T(j)*(hc(1)+hc(2)*T(j)/2 +hc(3)*((T(j))^2)/3 +hc(4)*((T(j))^3)/4 + hc(5)*((T(5))^4)/5 + hc(6)/T(j));
         S(j) = R*(hc(1)*log(T(j))+hc(2)*T(j)+hc(3)*((T(j))^2)/2 +hc(4)*((T(j))^3)/3 + hc(5)*((T(j))^4)/4 + hc(7));
        
    end
  
end
 spec=char(species)
 
 fd = sprintf('%s',spec);
 cur_dir=pwd
mkdir(spec);
    cd(spec);
    
%Plot 1, Specific heat (Cp) vs Temperature (T)
figure(1);
plot(T,Cp);
xlabel('Temperature in K');
ylabel('Specific heat in kJ');
title('Specific heat vs Temperature');
      
%Plot 2, Enthalpy (H) vs Temperature (T)  
figure(2);
plot(T,H);
xlabel('Temperature in K');
ylabel('Enthalpy in kJ/(mol)');
title('Enthalpy vs Temperature');
      
%Plot 3, Entropy (S) vs Temperature (T)
figure(3);
plot(T,S);
xlabel('Temperature in K');
ylabel('Entropy in kJ/(mol K)');
title('Entropy vs Temperature');


% saving the plots that got generated

saveas(figure(1), 'cp.png');
saveas(figure(2), 'h.png');
saveas(figure(3), 's.png');
cd(cur_dir);
 
end

Function for molecular weight:

%Function_for_Molecular_Weight%

function M=Molecular_Weight(species_element)
        atoms={'H','C','N','O','AR'};
        AtomicWeight=[1 12 14 16 40];
        M=0;
        for i=1:length(species_element)
            for j=1:length(atoms)
                if strcmp(species_element(i),atoms(j))
                    M=M+AtomicWeight(j);
                    p=j;
                end
                n=str2num(species_element(i));
                if n>1
                    M=M+(AtomicWeight(p)*(n-1));
           end
      end
end

Explanation of programme:

• We start the program with close all,clear all and clc.
• fopen is an inbuilt command use for open 'THERMO.dat' file and stored in varible called f1.
• fgetl is used for read command. first line is documend heading stored in the varible l1.
• Similarlly second line stored in l2.
• Next three lines are comments which are irrelevent to the program .That why we use for loop .
• strsplit used for split data and ' ' is delimeter according to it splits automattically .
• Global low , mid and high temp are converted from string to number using inbuilt command str2num.
• input command use for entering the species name. dispaly in command window.
• For loop is used for extract the 14 coefficient of all the 53 species.
• Mm function used for calculate the molecular weight of all the species.fprintf used for display all the molercular weight in command window.
• L1 is used to store the pattern into of line1 with 'E' as a marker.
• Values of the coefficient stored in the varibles c1,c2,c3,c4,c5........etc.
• Operation is performed for remain 2 lines also line2 and line3.
• mkdir command is used for creating new new diectory where individual folder for all species.
• R is inputs
• for loop is used to run the set of commands for all the values of temperature.
• if and else is used for different temperature range .if the temperature is below 3000 use different sets of commands otherwise the commands under else statement is used.
• plot command is used for plotting the graph b/w temp and entropy,specific heat , enthalpy.
• saveas used for save the plot of each species.
• fclose is used to close the file (f1)

Plots for O2:

1.specific heat plot 2.enthalpy plot 3.entroy plot

Plots for N2:

1.specific heat plot 2.enthalpy plot 3.entroy plot

Plots for CO2:

1.specific heat plot 2.enthalpy plot 3.entroy plot

window where all the folders are saved:

Conclusion:

Thus the function that extracts the coefficients ans calculate the enthalpy,entropy and specific heat for all the species in the data file and as well as the molercular weight of each species are calculated and plottd done by the Cp,H,S and local temperature for each species.