Get temperature given pressure and enthalpy

Question

ThermodynamicData["Ammonia", "Enthalpy", {"Temperature" -> t,"Pressure" -> p}]

works fine, but how can I get temperature when pressure and enthalpy are given?

Answer 1

i suppose you can use standard numerical methods..

 h[t_?NumericQ, p_?NumericQ] := 
 QuantityMagnitude[
   ThermodynamicData["Ammonia", 
    "Enthalpy", {"Temperature" -> Quantity[t, "Kelvins"], 
     "Pressure" -> Quantity[p, "MegaPascals"]}]]

FindRoot[h[t,.4] == 19300, {t, 200}]

{t -> 199.982}