Thursday, February 21, 2019

Water from pipe from sea to land

Sometimes, in dry areas, the sea nearby is warmer than the land at night. If one has a pipe with inlet over the sea and outlet over the land it is possible the warmer less dense sea air will rise in the pipe and water will condense out on the land side. At the same temperature moist air has a lower density than dry air. Here is computer code that will help one determine whether water will condense out (RH becomes greater than 100% - if that were possible).
T is in deg C, P is in kPa, RH is a percentage.
The inputs are initial temperature Ti above sea surface, initial relative humidity (RH) above sea surface, initial atmospheric pressure just above the sea surface (P1) and final temperature Tf (above land of desert), and P2 (at altitude of land of desert). Delphi computer code below:

label 1;
var
Tdewi,Tdewf,Pvf,LCL1,LCL2,Pvi,Psatwi,Psatwf,RHf,HR,RH,p1,p2,Ti,Tf,Hinc,q,lnx,x,
Psat,h,p:extended;
errors1:boolean;
calcstr6,calcstr5,calcstr4,calcstr2,calcstr1,calcstr3:string[30];
begin
errors1:=false;
form47.hide;
form47.show;
try
Ti:=strtofloat(form47.edit1.Text);
RH:=strtofloat(form47.edit2.Text);
P1:=strtofloat(form47.edit3.Text);
Tf:=strtofloat(form47.edit4.Text);
P2:=strtofloat(form47.edit5.Text);
except
errors1:=true;
end;
if (errors1=true) or (Ti<0) or (Ti>100) or (RH>100) or (RH<0) or (P1<2) or (P1>500) or (Tf<0)
or (Tf>100) or (P2<2) or (P2>500)
then begin
form47.canvas.textout(0,100,'CHECK ENTRIES.');
goto 1
end;
Psatwi:=0.61121*exp((18.678-Ti/234.5)*Ti/(257.14+Ti));
Pvi:=Psatwi*(RH/100);
HR:=0.622*Pvi/(P1-Pvi);
Psatwf:=0.61121*exp((18.678-Tf/234.5)*Tf/(257.14+Tf));
RHf:=(HR*P2)/((0.622+HR)*Psatwf);
Pvf:=RHf*Psatwf;

Tdewi:=Ti;
repeat
Tdewi:=Tdewi-0.001;
Psat:=0.61121*exp((18.678-Tdewi/234.5)*Tdewi/(257.14+Tdewi));
until (Psat<=Pvi);
str(Tdewi:12:2,calcstr3);

Tdewf:=Tf;
repeat
Tdewf:=Tdewf-0.001;
Psat:=0.61121*exp((18.678-Tdewf/234.5)*Tdewf/(257.14+Tdewf));
until (Psat<=Pvf);
str(Tdewf:12:2,calcstr4);

LCL1:=125*(Ti-Tdewi);
LCL2:=125*(Tf-Tdewf);
str(LCL1:15:2,calcstr5);
str(LCL2:15:2,calcstr6);

str((100*RHf):15:2,calcstr1);
str(HR:15:5,calcstr2);
If(RHf<1) then form47.canvas.textout(0,120,'Relative humidity (RH) AFTER PARCEL HAS MOVED is: '+calcstr1+'%.');
If (RHf<1) then form47.canvas.textout(0,150,'Humidity ratio (HR) remains the same as the air parcel moves: '+calcstr2+' kg/kg.');
If(RHf>1) then form47.canvas.textout(0,120,'Air has become SATURATED and FICTITIOUS relative humidity (RH) AFTER PARCEL HAS MOVED is: '+calcstr1+'%.');
form47.canvas.textout(0,190,'Dew point for initial Ti and P1 situation is: '+calcstr3+' deg C.');
if (RHf<1) then form47.canvas.textout(0,220,'Dew point for final Tf and P2 situation is '+calcstr4+' deg C.');
form47.canvas.textout(0,260,'LCL1 for initial Ti and P1 situation is: '+calcstr5+' m.');
if (RHf<1) then form47.canvas.textout(0,290,'LCL2 for final Tf and P2 situation is '+calcstr6+' m.');

1: end;

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