Throttling refrigeration and expander refrigeration

When the same pressure is reduced, the temperature drop of throttling is far greater than that of expansion. This is because the gas does not work externally during throttling, but when the molecular spacing increases, the potential energy of molecules increases, and the kinetic energy decreases correspondingly, reflecting the decrease of temperature. The expansion refrigeration not only increases the potential energy between molecules, but also makes external work to push the impeller to rotate or push the piston to move. All these energies need to reduce the kinetic energy of molecules, so the molecular kinetic energy decreases more and the temperature drop is larger.