The differential throttling effect of liquid ammonia

μH=(T/p)H＞0，for the isoenthalpy throttling process of liquid ammonia from high pressure to low and moderate pressure

means a refrigerating effect.The magnitude of the integral throttling effect ΔTH depends on the states (T

p) before and after throttling.Given the post-throttling pressure p2

the refrigerating extent ΔTH is larger when the initial temperature is lower and the pressure is higher before throttling.The relationship of enthalpy with pressure and the computing method of ΔTH for the liquid ammonia were derived.The deviation was small for the calculated refrigerating extent ΔTH in comparison with the experimental value

which met the requirements for practical use.It was found that a refrigerating extent from 7.5℃ to 15℃ could be obtained in the ammonia-synthesis system with a moderate operating pressure.To benefit from lower energy consumption and production cost

the refrigeration working procedure in the present ammonia-synthesis system could be replaced by exploiting the self-generating refrigerating effect from the throttling effect of liquid ammonia

as well as some techniques of cold quantity reclaiming and energy saving.