I have a question regarding MATLAB. I have class file where I can solve my problem with by simply defining the problem parameters in my script and call on a class in MATLAB to solve the problem with parameters that I provide. Now, the resulting variables that are computed by the class, how can I import them into the worskspace or display them within my MATLAB script without altering the class?
Class code
classdef rankine
% Rankine cycle class
properties
% Inlet properties
mass_flow; % Mass flow of system (kg/s)
Pboiler; % Boiler pressure (bar)
superheat; % Boiler degrees superheat (C)
isen_eff_turbine; % Turbine isentropic efficiency
Pcond; % Condenser pressure (bar)
subcooling; % Condenser subcooling
% Calclated properties
h_out_boiler; % Boiler outlet enthalpy (kJ/kg)
s_out_boiler; % Boiler outlet entropy (kJ/kg-K)
h_out_turbine; % Turbine outlet enthalpy (kJ/kg)
s_out_turbine; % Turbine outlet entropy (kJ/kg-K)
h_out_condenser; % Condenser outlet enthalpy (kJ/kg)
s_out_condenser; % Condenser outlet entropy (kJ/kg-K)
h_out_pump; % Pump outlet enthalpy (kJ/kg)
s_out_pump; % Pump outlet entropy (kJ/kg-K)
turbine_exh_quality; % Turbine exhaust quality
T_boiler_out; % Boiler outlet temperature (C)
T_turbine_out; % Turbine outlet temperature (C)
T_condenser_out; % Condenser outlet temperature (C)
T_pump_out; % Pump outlet temperature (C)
Q_boiler; % Boiler Heat Rate (kW)
W_turbine; % Turbine Work Rate (kW)
Q_condenser; % Condenser Heat Rate (kW)
W_pump; % Pump Work Rate (kW)
Q_net; % Plant Net Heat Rate (kW)
W_net; % Plant Net Work Rate (kW)
plant_efficiency; % Plant Thermal Efficiency
end
methods % Methods for rankine class
% Make constructor for the class
function obj=rankine(mass_flow,Pboiler,superheat,isen_eff_turbine,Pcond,subcooling)
% Enter system parameters
obj.mass_flow=mass_flow;
obj.Pboiler=Pboiler;
obj.superheat=superheat;
obj.isen_eff_turbine=isen_eff_turbine;
obj.Pcond=Pcond;
obj.subcooling=subcooling;
% Calculate boiler outlet specific enthalpy and entropy
if ~superheat % saturated vapor
obj.T_boiler_out=XSteam('Tsat_p',Pboiler);
obj.h_out_boiler=XSteam('hV_p',Pboiler);
obj.s_out_boiler=XSteam('sV_p',Pboiler);
else % Superheat
obj.T_boiler_out=XSteam('Tsat_p',Pboiler)+superheat;
obj.h_out_boiler=XSteam('h_pT',Pboiler,obj.T_boiler_out);
obj.s_out_boiler=XSteam('s_pT',Pboiler,obj.T_boiler_out);
end
% Calculate turbine parameters
h_out_s_turbine=XSteam('h_ps',Pcond,obj.s_out_boiler);
obj.h_out_turbine=obj.h_out_boiler-isen_eff_turbine*(obj.h_out_boiler-h_out_s_turbine);
obj.s_out_turbine=XSteam('s_ph',Pcond,obj.h_out_turbine);
obj.turbine_exh_quality=XSteam('x_ph',Pcond,obj.h_out_turbine);
obj.T_turbine_out=XSteam('Tsat_p',Pcond);
obj.W_turbine=mass_flow*(obj.h_out_boiler-obj.h_out_turbine);
% Calculate condenser parameters
if ~subcooling % saturated liquid
obj.h_out_condenser=XSteam('hL_p',Pcond);
obj.s_out_condenser=XSteam('sL_p',Pcond);
obj.T_condenser_out=obj.T_turbine_out;
v=XSteam('vL_p',Pcond);
else
obj.T_condenser_out=obj.T_turbine_out-subcooling;
obj.h_out_condenser=XSteam('h_pT',Pcond,obj.T_condenser_out);
obj.s_out_condenser=XSteam('s_pT',Pcond,obj.T_condenser_out);
v=XSteam('v_ph',Pcond,obj.h_out_condenser);
end
obj.Q_condenser=mass_flow*(obj.h_out_turbine-obj.h_out_condenser);
% Calculate pump parameters
obj.W_pump=(Pboiler-Pcond)*100*v*mass_flow;
obj.h_out_pump=obj.h_out_condenser+(Pboiler-Pcond)*100*v;
obj.s_out_pump=obj.s_out_condenser; % Isentropic case for now
%obj.s_out_pump=XSteam('s_ph',Pboiler,obj.h_out_pump);
obj.T_pump_out=XSteam('T_ph',Pboiler,obj.h_out_pump);
% Calculate boiler heat rate
obj.Q_boiler=(obj.h_out_boiler-obj.h_out_pump)*mass_flow;
% Calcualte net work and heat rates
obj.W_net=obj.W_turbine-obj.W_pump;
obj.Q_net=obj.Q_boiler-obj.Q_condenser;
obj.plant_efficiency=obj.W_net/obj.Q_boiler;
end % End constructor
function obj=update(obj,parameter_name,parameter_value)
switch lower(parameter_name)
case 'mass_flow'
obj.mass_flow=parameter_value;
case 'pboiler'
obj.Pboiler=parameter_value;
case 'superheat'
obj.superheat=parameter_value;
case 'isen_eff_turbine'
obj.isen_eff_turbine=parameter_value;
case 'pcond'
obj.Pcond=parameter_value;
case 'subcooling'
obj.subcooling=parameter_value;
otherwise
error('Parameter not modifiable. Parameters to modify are mass_flow, Pboiler, superheat, isen_eff_turbine, Pcond, subcooling')
end
% Calculate boiler outlet specific enthalpy and entropy
if ~obj.superheat % saturated vapor
obj.T_boiler_out=XSteam('Tsat_p',obj.Pboiler);
obj.h_out_boiler=XSteam('hV_p',obj.Pboiler);
obj.s_out_boiler=XSteam('sV_p',obj.Pboiler);
else % Superheat
obj.T_boiler_out=XSteam('Tsat_p',obj.Pboiler)+obj.superheat;
obj.h_out_boiler=XSteam('h_pT',obj.Pboiler,obj.T_boiler_out);
obj.s_out_boiler=XSteam('s_pT',obj.Pboiler,obj.T_boiler_out);
end
% Calculate turbine parameters
h_out_s_turbine=XSteam('h_ps',obj.Pcond,obj.s_out_boiler);
obj.h_out_turbine=obj.h_out_boiler-obj.isen_eff_turbine*(obj.h_out_boiler-h_out_s_turbine);
obj.s_out_turbine=XSteam('s_ph',obj.Pcond,obj.h_out_turbine);
obj.turbine_exh_quality=XSteam('x_ph',obj.Pcond,obj.h_out_turbine);
obj.T_turbine_out=XSteam('Tsat_p',obj.Pcond);
obj.W_turbine=obj.mass_flow*(obj.h_out_boiler-obj.h_out_turbine);
% Calculate condenser parameters
if ~obj.subcooling % saturated liquid
obj.h_out_condenser=XSteam('hL_p',obj.Pcond);
obj.s_out_condenser=XSteam('sL_p',obj.Pcond);
obj.T_condenser_out=obj.T_turbine_out;
v=XSteam('vL_p',obj.Pcond);
else
obj.T_condenser_out=obj.T_turbine_out-obj.subcooling;
obj.h_out_condenser=XSteam('h_pT',obj.Pcond,obj.T_condenser_out);
obj.s_out_condenser=XSteam('s_pT',obj.Pcond,obj.T_condenser_out);
v=XSteam('v_ph',obj.Pcond,obj.h_out_condenser);
end
obj.Q_condenser=obj.mass_flow*(obj.h_out_turbine-obj.h_out_condenser);
% Calculate pump parameters
obj.W_pump=(obj.Pboiler-obj.Pcond)*100*v*obj.mass_flow;
obj.h_out_pump=obj.h_out_condenser+(obj.Pboiler-obj.Pcond)*100*v;
obj.s_out_pump=XSteam('s_ph',obj.Pboiler,obj.h_out_pump);
obj.T_pump_out=XSteam('T_ph',obj.Pboiler,obj.h_out_pump);
% Calculate boiler heat rate
obj.Q_boiler=(obj.h_out_boiler-obj.h_out_pump)*obj.mass_flow;
% Calcualte net work and heat rates
obj.W_net=obj.W_turbine-obj.W_pump;
obj.Q_net=obj.Q_boiler-obj.Q_condenser;
obj.plant_efficiency=obj.W_net/obj.Q_boiler;
end % End update
function plot_ts(obj) % Plots the t-s diagram of the process
% Get the minimum and maximum pressures and temperatures
Tmax=obj.T_boiler_out;
Pmax=obj.Pboiler;
Pmin=obj.Pcond;
ts_diagram([Pmin Pmax],Tmax*1.5);
title('T-s Diagram For Process')
axesHandles=get(gcf,'Children');
classHandles=handle(axesHandles);
axes(classHandles(1))
hold on
% First draw the turbine process
plot([obj.s_out_boiler obj.s_out_turbine],[obj.T_boiler_out obj.T_turbine_out],...
'Linewidth',3,'Color','k')
% Draw the condenser process
sL=XSteam('sL_p',obj.Pcond); % Saturated liquid entropy
s_line=[obj.s_out_turbine sL];
T_line=[obj.T_turbine_out obj.T_turbine_out];
if (obj.subcooling~=0) % Subcooled
s_line=[s_line obj.s_out_condenser];
T_line=[T_line obj.T_condenser_out];
end
plot(s_line,T_line,'Linewidth',3)
% Draw the pump process
s_line=[obj.s_out_condenser obj.s_out_pump];
T_line=[obj.T_condenser_out obj.T_pump_out];
plot(s_line,T_line,'Linewidth',3,'Color',[0.5 0 0.5])
% Draw the boiler process
sL=XSteam('sL_p',obj.Pboiler);
s_subcooled=linspace(obj.s_out_pump,sL,101);
T_subcooled=arrayfun(@(s) XSteam('T_ps',obj.Pboiler,s), s_subcooled);
sV=XSteam('sV_p',obj.Pboiler);
TV=XSteam('Tsat_p',obj.Pboiler);
s_line=[s_subcooled sV];
T_line=[T_subcooled TV];
if (obj.superheat>0)
s_super=linspace(sV,obj.s_out_boiler,101);
T_super=arrayfun(@(s) XSteam('T_ps',obj.Pboiler,s), s_super);
s_line=[s_line s_super(2:end)];
T_line=[T_line T_super(2:end)];
end
plot(s_line,T_line,'Linewidth',3,'Color','r')
LH=legend('Turbine','Condenser','Pump','Boiler','Location','northwest');
set(LH,'Color','w')
end % End plot_ts
function plot_mollier(obj)
% Get extremities of operating points
Phigh=obj.Pboiler;
Plow=obj.Pcond;
slow=obj.s_out_condenser;
shigh=obj.s_out_boiler;
hlow=obj.h_out_condenser;
hhigh=obj.h_out_boiler;
x_exhaust=obj.turbine_exh_quality;
Thigh=obj.T_boiler_out;
T_low=XSteam('T_ps',Phigh,shigh);
pressures=[Plow/2 Plow Plow/4+Phigh/8 Plow/2+Phigh/4 Phigh/2 Phigh Phigh*1.5];
temperatures=[Thigh-rem(Thigh,10)+10];
entropies=[slow*0.8 shigh*1.2];
qualities=min([0.7 x_exhaust-rem(x_exhaust,0.05)-0.05]):0.01:1;
hrange=[hlow*0.8 hhigh*1.2];
mollier(entropies,hrange,pressures,temperatures,qualities);
title('Mollier diagram for process')
axesHandles=get(gcf,'Children');
classHandles=handle(axesHandles);
axes(classHandles(1))
hold on
% Plot turbine line
plot([obj.s_out_boiler obj.s_out_turbine],...
[obj.h_out_boiler obj.h_out_turbine],...
'Linewidth',3,'Color','k')
% Plot condenser line
scond=linspace(obj.s_out_turbine,obj.s_out_condenser,101);
hcond=arrayfun(@(s) XSteam('h_ps',obj.Pcond,s),scond);
plot(scond,hcond,'Linewidth',3,'Color','b')
% Plot pump line
spump=[obj.s_out_condenser obj.s_out_pump];
hpump=[obj.h_out_condenser obj.h_out_pump];
plot(spump,hpump,'Linewidth',3,'Color',[0.5 0 0.5])
% Plot boiler line
sboiler=linspace(obj.s_out_pump,obj.s_out_boiler,101);
hboiler=arrayfun(@(s) XSteam('h_ps',obj.Pboiler,s),sboiler);
plot(sboiler,hboiler,'Linewidth',3,'Color','r')
LH=legend('Turbine','Condenser','Pump','Boiler','Location','northwest');
set(LH,'Color','w')
end % end plot_mollier
end % End Methods
end % End rankine classMy script calling onto it.
clc;
clear all;
close all;
import rankine
%Problem 1
mass_flow = 200;
Pboiler = 50;
superheat = 0;
isen_eff_turbine = 0.85;
Pcond = 1;
subcooling = 5;
problem1 = rankine(mass_flow, Pboiler, superheat, isen_eff_turbine, Pcond, subcooling)The rankine class outputs solutions for each step such as
h_out_boiler
s_out_boiler
h_out_turbine
s_out_turbineBasically, I would like to take the variables the rankine class outputs and put them into the MATLAB workspace without modifying the rankine class. Thanks.
Add the following to your script:
rankineOutput = struct(problem1) ; %// convert the object into a structure
fldNames = fieldnames(rankineOutput) ; %// get the field names of the structure
for iField = 1:numel(fldNames)
varName = fldNames{iField} ; %// extract specific field name (just for the sake of clarity)
assignin('base', varName , rankineOutput.(varName) ) ; %// assign the value in the field to a variable with the same name in the base workspace
end
You might get a warning about the conversion of the object into structure but you can ignore it (it will not change the implementation of the class).
This will extract all the fields into variables in the base workspace. If you only want a subset you can use the same method but be more selective in which field you extract.
depending on your version of Matlab, you can even avoid the conversion to structure by calling the same directly on the object:
fldNames = fieldnames(problem1) ; %// get the field names of the object
for iField = 1:numel(fldNames)
varName = fldNames{iField} ; %// extract specific field name (just for the sake of clarity)
assignin('base', varName , problem1.(varName) ) ; %// assign the value in the field to a variable with the same name in the base workspace
end