Quiet@Remove["Global`*"];
$HistoryLength=2;
SetDirectory[NotebookDirectory[]];Off[Solve::"ifun",General::"spell1"]

p1[t_]:=Exp[((1500.3+23.5*t)/(234+t))];
t=100;
{p1[t],p2[t]}

Plot[p1[T],{T,20,100},AxesLabel->{"T[°C]","p[Pa]"},GridLines->Full]

(*heating the air*)
Quiet@Remove["Global`*"];
TA=0;
fiA=0.8;
xA=3.0592;(*grams H2O per 1 kg of dry air*)
hA=7.6508;(* enhtalpy, kJ/kg*)
xB=xA;
fiB=0.174;
hB=31.01;
TB=23.;
neededHeat=hB-hA;
Print["needed heat fo heating= ",neededHeat," kJ/kgda"];
V=6*3*11;
density=(349./(TB+273));
Print["Volume= ",V," (m^3),  density= ",density," kg/(m^3)"]
mass=V*density;
Print["there is ",mass," kg of dry air in the room"]
timeOfAirExchange=3*3600.;
energy=mass*neededHeat;
Print["needed energy for one air exchange= ",(energy/1000)," MJ"]

power=(energy/timeOfAirExchange);
Print["power for heating= ",power," kW"]

Quiet@Remove["Global`*"];
(*drying the air*)
fiA=0.8;
TA=25;
xA=16.1866;
hA=66.4757;
fiC=0.5;
TC=25;
xC=10.0189;
hC=50.7671;
xB=xC;
fiB=1;
TB=13.865;
hB=39.3155;
heatFromAir=hA-hB;
Print["energy of cooling= ",heatFromAir," kJ/kgda"];
energyIntoAir=hC-hB;
Print["energy of heating= ",energyIntoAir," kJ/kgda"];

Quiet@Remove["Global`*"];
(*increasing relative moisture*)
TA=15;
fiA=0.4;
xA=4.2737;
hA=25.9561;
TB=23;
fiB=0.7;
xB=12.4871;
hB=54.9874;
hC=hB;
xC=xA;
TC=43.5218;
energy=hC-hA;
Print["energy of heating= ",energy," kJ/kgda"];
water=xB-xA;
Print["we need ",water," g of H2O for each kg of dry air"]

Quiet@Remove["Global`*"];
(*mixing and heating*)
TA=25;
fiA=0.8;
xA=16.1866;
hA=66.4757;
TB=10;
fiB=0.7;
xB=5.3946;
hB=23.6906;
TC=20;
fiC=0.6;
xC=8.8559;
hC=42.6736;
xD=xC;
solmA=Solve[xA*mA+xB*(1-mA)==xD][[1]]
hD=mA*hA+(1-mA)*hB/.solmA;
Print["enthalpy after mixing= hD= ",hD," kJ/kgda"];
neededHeat=hC-hD;
Print["energy of heating= ",neededHeat," kJ/kgda"];