Challenge

Project 2 - Rankine cycle Simulator

SSudarshan Gauda9 Jan 2022

MATLAB

Aim:- Create a Rankine Cycle Simulator using MATLAB.

Objective:-

Calculate the state points of the Rankine Cycle based on user inputs.
plot the corresponding T-s and h-s plots for the given set of inputs.

Outputs:-

Net work output
Back work ratio

Given Inputs Value:-

Turbine Inlet temperature = 400° C
Turbine Inlet Pressure = 30 bars
Turbine Outlet Pressure = 0.05 bars = Condenser Inlet Pressure

Steam Table Data:- Standard XSteam library

Rankine Cycle:- The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat source and heat sink.

Heat energy is supplied to the system via a boiler where the working fluid (typically water) is converted to a high pressure gaseous state (steam) in order to turn a turbine. After passing over the turbine the fluid is allowed to condense back into a liquid state as waste heat energy is rejected before being returned to boiler, completing the cycle. Friction losses throughout the system are often neglected for the purpose of simplifying calculations as such losses are usually much less significant than thermodynamic losses, especially in larger systems.

Four Processes in the Rankine Cycle:-

Process 1–2: The working fluid is pumped from low to high pressure. As the fluid is a liquid at this stage, the pump requires little input energy. Process 1-2 is isentropic compression.

Process 2–3: The high-pressure liquid enters a boiler, where it is heated at constant pressure by an external heat source to become a dry saturated vapour. The input energy required can be easily calculated graphically, using an enthalpy–entropy chart (h–s chart, or Mollier diagram), or numerically, using steam tables or software. Process 2-3 is constant pressure heat addition in boiler.

Process 3–4: The dry saturated vapour expands through a turbine, generating power. This decreases the temperature and pressure of the vapour, and some condensation may occur. The output in this process can be easily calculated using the chart or tables noted above. Process 3-4 is isentropic expansion.

Process 4–1: The wet vapour then enters a condenser, where it is condensed at a constant pressure to become a saturated liquid. Process 4-1 is constant pressure heat rejection in condenser.

Formulae:-

Workdone & Efficiency

Specific Stem Consuption

Back Work Ratio

Matlab Code:-

clear all
close all
clc

%Process Information
fprintf('Rankine Cycle Simulator \n')
fprintf('process 1-2 : Isentropic Expansion \n')
fprintf('process 2-3 : Isobaric Heat Rejection \n')
fprintf('process 3-4 : Isentropic compression \n')
fprintf('process 4-1 : Isobaric heat addition process \n')

%Initial Inputs
P1 = input('Enter the inlet pressure of Turbine: ')
P2 = input('Enter the outlet pressure from Turbine: ')
T1 = input('Enter the steam inlet Temperature: ')

%State point 1
H1 = XSteam('h_pt',P1,T1); %Enthalpy
S1 = XSteam('s_pt',P1,T1); %Entropy
Hf1 = XSteam('hL_p',P1); %Enthalpy of saturated liquid
Hg1 = XSteam('hV_p',P1); %Enthalpy of saturated vapour
Ts1 = XSteam('Tsat_P',P1); %Saturation Temp
Sf1 = XSteam('sL_p',P1); %Entropy of saturated liquid
Sg1 = XSteam('sV_p',P1); %Entropy of saturated vapour

%State point 2
S2 = S1;
Sf2 = XSteam('sL_p',P2);
Sg2 = XSteam('sV_p',P2);
Hf2 = XSteam('hL_p',P2);
Hg2 = XSteam('hV_p',P2);
x = (S2-Sf2)/(Sg2-Sf2); %Dryness Fraction
H2 =Hf2+x*(Hg2-Hf2);
T2 = XSteam('T_ph',P2,H2);
Ts2= XSteam('Tsat_p',P2);

%State Point 3
H3 = Hf2;
S3 = Sf2;
T3 = T2;
P3 = P2;

%State point 4
P4 = P1;
S4 = S3;
H4 = XSteam('h_ps',P4,S4);
T4 = XSteam('T_Ps',P4,S4);

t = linspace(0,374,500);

%Plot T-S Diagram
figure(1)
hold on

for i = 1:length(t)
plot(XSteam('sL_T',t(i)),t(i),'.','color','b')
plot(XSteam('sV_T',t(i)),t(i),'.','color','b')
end

%Plot Cycle,
plot([S1,S2],[T1 T2],'linewidth',2,'color','r')
if x>1
T3 =Ts2;
plot([S2 Sg2 S3 S4],[T2,Ts2 T3 T4],'linewidth',2,'color','r')
T2 = Ts2;
else
plot([S2 S3 S4],[T2 T3 T4],'linewidth',2,'color','r');
end

l = linspace(T1,T2,1000)

for i=1:length(l)
plot(XSteam('s_pT',P1,l(i)),l(i),'.','color','r')
end
plot([Sf1 Sg1],[Ts1 Ts1],'linewidth',2,'color','r')
xlabel('Entropy[KJ/Kg-K]')
ylabel('Temprature[K]')
title('T-S Diagram')

%Plot H-S Diagram
figure(2)
hold on

%Plot Saturation Curve
for i=1:length(t)
plot(XSteam('sL_T',t(i)),XSteam('hL_T',t(i)),'.','color','b')
plot(XSteam('sV_T',t(i)),XSteam('hV_T',t(i)),'.','color','b')
end

%Plot Cycle
plot([S1 S2 S3 S4 S1],[H1 H2 H3 H4 H1],'linewidth',2,'color','r')
xlabel('Entropy[KJ/Kg-K]')
ylabel('Enthalpy[KJ/Kg]')
title('H-S Diagram')

%calcualtion

%Turbine Work
wt = H1-H2

%Pump Work
wp = H4-H3;

%Heat Addistion
Qin = H1-H4;

%Heat Rejection
Qout = H2-H3;

%Net Work
Wnet=wt-wp;

%Efficiency
Ntherm = (Wnet/Qin)*100

%Specific stem consumption
SSC = 3600/Wnet;

%Back power Ratio
BWR= wp/wt;

%Print Result
fprintf('\n\nResults\n')
fprintf('At State Point 1:\n')
fprintf('P1 is : %.2f bar\n',P1)
fprintf('T1 is : %.2f Deg Celcius\n',T1)
fprintf('H1 is : %.2f KJ/Kg\n',H1)
fprintf('S1 is : %.2f KJ/Kg-K\n',S1)

fprintf('\nAt State Point 2:\n')
fprintf('P2 is : %.2f bar\n',P2)
fprintf('T2 is : %.2f Deg Celcius\n',T2)
fprintf('H2 is : %.2f KJ/Kg\n',H2)
fprintf('S2 is : %.2f KJ/Kg-K\n',S2)

fprintf('\nAt State Point 3:\n')
fprintf('P3 is : %.2f bar\n',P3)
fprintf('T3 is : %.2f Deg Celcius\n',T3)
fprintf('H3 is : %.2f KJ/Kg\n',H3)
fprintf('S3 is : %.2f KJ/Kg-K\n',S3)

fprintf('\nAt State Point 4:\n')
fprintf('P4 is : %.2f bar\n',P4)
fprintf('T4 is : %.2f Deg Celcius\n',T4)
fprintf('H4 is : %.2f KJ/Kg\n',H4)
fprintf('S4 is : %.2f KJ/Kg-K\n',S4)

fprintf('\nWt is : %.2f KJ/Kg\n',wt)
fprintf('Wp is : %.2f KJ/Kg\n',wp)
fprintf('Wnet is : %.2f KJ/Kg\n', Wnet)
fprintf('Thermal Efficiency is : %.2f percent\n',Ntherm)
fprintf('S.S.C. is : %.2f Kg/KWh\n',SSC)
fprintf('Back Work Ratio is : %.3f \n',BWR)

Steps:-

1. clear all, close all, clc, use to clear any previosly defined values.

2. FIrst step is bring the given inputs to the program, for that the 'input()' command use. The user inputs includes tempareture and pressure entry to the turbine and pressue after existing to the turbine.

3. Using the given inputs all four stages points are calculated.

(H-Enthalpy, S-Entropy, T-Temperature, P-Pressure, x-Dryness factor, )

4. After calculating all parameters, now calculate the Pumpwork, Turbine Work, Net work output, Back Ratio, Thermal Efficiency.

5. Now to display all inputs 'fprintf()' command use.

6. Next is to plot the grapt, H-S & T-S, First step to calculate the saturation curve for loop use.

Results:-