Gases are cooled in Joule-Thomson expansion, when it is __________ inversion temperature.

Answer: Option A

Above the inversion temperature joule-thomson coefficient $${\left(\frac{\partial T}{\partial P}\right)}_H=-ve$$
So, by throttling (decreasing the pressure) the temperature increases and hence heating.
Below the inversion temperature houle-thomson coefficient $${\left(\frac{\partial T}{\partial P}\right)}_H=+ve$$
So,by throttling the temperature decreases hence cooling.