What is wrong with my code?

Code needs to display:

Code is displaying a blank graph.

clear,clc
R=8.314; T1=60+273.15; PvapH=.7583;PvapT=.3843;HvapH=29000;HvapT=31000;P=.7;
fPvapH1=@(T2) PvapH*exp(-1*HvapH/R*((1./T2)-(1/T1)));
fPvapT1=@(T2) PvapT*exp(-1*HvapT/R*((1./T2)-(1/T1)));
fxH=@(x) (x*PvapH/P)+((1-x)*PvapT/P)-1;
xH=fzero(fxH,.7);
xT=1-xH;
fBPH=@(T2) (((xH*fPvapH1(T2))/P)+((xT*fPvapT1(T2))/P))-1;
BPH=fzero(fBPH,340);
yH=xH*fPvapH1(BPH)/P;
yT=xT*fPvapT1(BPH)/P;
T=linspace(55,80,100);
figure(1)
plot(xH,fBPH(T))
hold on
plot(yH,fBPH(T))
hold off
axis([0 1 55 80])

[AndresVar]

• xH and yH are not vectors
• this T should be in celcius or kelvin? it returns -1 -1 -1 -1...

R=8.314; T1=60+273.15; PvapH=.7583;PvapT=.3843;HvapH=29000;HvapT=31000;P=.7;
fPvapH1=@(T2) PvapH*exp(-1*HvapH/R*((1./T2)-(1/T1)));
fPvapT1=@(T2) PvapT*exp(-1*HvapT/R*((1./T2)-(1/T1)));
fxH=@(x) (x*PvapH/P)+((1-x)*PvapT/P)-1;
xH=fzero(fxH,.7)

xH = 0.8441

xT=1-xH;
fBPH=@(T2) (((xH*fPvapH1(T2))/P)+((xT*fPvapT1(T2))/P))-1;
BPH=fzero(fBPH,340);
yH=xH*fPvapH1(BPH)/P

yH = 0.9144

yT=xT*fPvapT1(BPH)/P;
T=linspace(55,80,100);

fBPH(T)

ans = 1×100

-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1

[Angelina Encinias]

I attached the graphs that the code should display. I am unsure if I need for loops.

[Angelina Encinias]

T should be Celsius

[Torsten]

In the equation

fxH=@(x) (x*PvapH/P)+((1-x)*PvapT/P)-1;

all parameters are given constants except x.

But PvapH and PvapT should depend on T, I guess.

[Angelina Encinias]

This is the question. I am pretty sure I need a for loop to display the graphs.

Answer 1

[Torsten]

  R = 8.314;
  T1 = 60 + 273.15;
  PvapH = .7583;
  PvapT = .3843;
  HvapH = 29000;
  HvapT = 31000;
  P = .7;
  fPvapH = @(T) PvapH*exp(-HvapH/R*(1./T - 1/T1));
  fPvapT = @(T) PvapT*exp(-HvapT/R*(1./T - 1/T1));
  
  XH = 0:0.01:1;
  Tstart = 340;
  for i=1:numel(XH)
    xH = XH(i);
    fun = @(T) xH*fPvapH(T)/P + (1-xH)*fPvapT(T)/P - 1;
    T(i) = fzero(fun,Tstart);
    Tstart = T(i)
  end
  YH = XH.*fPvapH(T)/P;
  XT = 1-XH;
  YT = XT.*fPvapT(T)/P;
  
  T = T - 273.15;  
  figure(1)
  plot(XH,T)
  hold on
  plot(YH,T)
  hold off
  axis([0 1 55 80])
  figure(2)
  plot(XT,T)
  hold on
  plot(YT,T)
  hold off
  axis([0 1 55 80])

Answer 2

[Benjamin Thompson]

xH, yH, and BPH are all scalar values. They must be the same length as fBPH(T). In this line to you mean to pass a vector argument to the fxH function handle?

xH=fzero(fxH,.7);

[Angelina Encinias]

Yes I did. The graph is supposed to look like the graph on the left (image I attached). To make the image on the right I need to do yH(xH).

[Angelina Encinias]

Image of graphs needed to display is attached.