Evaporative cooling of air

procedure EvapCool;
var
iocode:integer;
ch:char;
Tap1,Tap2,HR1,HR2,T1,T2,RHwb,Twb,Pwb,effc,Pv1,Pv2,Psat1,Psat2,
RH1,RH2,Pa1,Pa2,Tk1,Tk2,P,V,Tw,A1,B1,C1,A2,B2,C2,RHwb1,mwe,mwen,
mwed,ma1,mv1,ma2,mv2,Ad1,Bd1,Cd1,Ad2,Bd2,Cd2,Psatd1,Psatd2,LCL1,
LCL2,eff,D1,d2,mv11,ma11,mv21,ma21,VPD1,VPD2,
Td1,Td2,VPDr,ew,fw,gw,hw,iw,Enth1,Enth2:extended;

begin
repeat
clrscr;
repeat
write('Enter initial T1 in deg C    ');
{$I-}
readln(T1);
{$I+}
iocode:=ioresult;
until (iocode=0) and (T1>0) and (T1<100);
repeat
write('Enter relative humidity RH1%    ');
{$I-}
readln(RH1);
{$I+}
iocode:=ioresult;
until (iocode=0) and (RH1>0) and (RH1<=100);
repeat
write('Enter atmospheric pressure P in kPa    ');
{$I-}
readln(P);
{$I+}
iocode:=ioresult;
until (iocode=0) and (P>50) and (P<=130);
repeat
write('Enter volume of air V in cubic m   ');
{$I-}
readln(V);
{$I+}
iocode:=ioresult;
until (iocode=0) and (V>0);
repeat
write('Enter efficiency of evaporative cooling   ');
{$I-}
readln(eff);
{$I+}
iocode:=ioresult;
until (iocode=0) and (eff>0) and (eff<100);

Pwb:=P/101.325;
RHwb1:=RH1;
RH1:=RH1/100;
Tk1:=T1+273.15;
Psat1:=0.61121*exp((18.678-T1/234.5)*(T1/(257.14+T1)));
Pv1:=Psat1*RH1;
Pa1:=P-Pv1;
ma1:=Pa1*V/(0.287*Tk1);
mv1:=Pv1*V/(0.4615*Tk1);
D1:=(ma1+mv1)/V;
HR1:=mv1/ma1;
Twb:=T1;
repeat
Twb:=Twb-0.001;
ew:=17.502*Twb;
fw:=240.97+Twb;
gw:=ew/fw;
hw:=66.8745*(1+0.00115*Twb);
iw:=6.112*exp(17.502*T1/(240.97+T1));
RHwb:=(611.2*exp(gw)-hw*Pwb*(T1-Twb))/iw;
until (RHwb<=RHwb1);
T2:=T1-(eff/100)*(T1-Twb);
mwen:=ma1*1.006*(T1-T2)+1.88*mv1*(T1-T2);
mwed:=2501.3+1.88*T2;
mwe:=mwen/mwed;
HR2:=(mwe+mv1)/ma1;
Psat2:=0.61121*exp((18.678-T2/234.5)*(T2/(257.14+T2)));
RH2:=HR2*P/((0.62185+HR2)*Psat2);
Pv2:=RH2*Psat2;
Tk2:=T2+273.15;
Pv2:=Psat2*RH2;
Pa2:=P-Pv2;
ma2:=Pa2*V/(0.287*Tk2);
mv2:=Pv2*V/(0.4615*Tk2);
D2:=(mv2+ma2)/V;
ad2:=9.81*(1-D1/D2);
Enth1:=ma1*1.006*T1+mv1*(2501.3+1.88*T1);
Enth2:=ma1*1.006*T2+(mv1+mwe)*(2501.3+1.88*T2);


writeln;
writeln('RESULTS:');
writeln('HR1 = ',HR1:13:5,' kg vapour/kg dry air');
writeln('HR2 = ',HR2:13:5,' kg vapour/kg dry air');
writeln('ma1 = ',ma1:15:5,' kg');
writeln('mv1 = ',mv1:15:5,' kg');
writeln('Initial wet bulb Twb = ',Twb:15:3,' deg C');
writeln('Mass of water evaporated mwe = ',mwe:15:4,' kg');
writeln('Mass of water evaporated = ',mwe/1000:15:6,' tonnes');
writeln('Air cooled to ',T2:15:4,' deg C');
writeln('Final RH = ',RH2*100:15:2,'%');
writeln('Initial density D1 = ',D1:15:4,' kg per cubic m');
writeln('Final density D2 = ',D2:15:4,' kg per cubic m');
writeln('Enth1 = ',enth1:15:3,' kJ, Enth2 = ',enth2:15:3,' kJ');


write('Another Y/N?');
repeat
ch:=readkey
until (ch in ['Y','N','y','n']);
until (ch in ['N','n']);
end;