Nowadays CFC and HCFC refrigerants are restricted because they causes to depletion of ozone layer. Accordingly, an experiment is apply to the $NH_3$ gas for refrigerant to study the performance characteristic and to improve the energy efficiency. An experiment are carried out for the condensed pressure in a range from 14.5bar to 16bar and for degree of superheat in a range from 0 to $10^{circ}C$ at each condensed pressure. As the result of experiment, when degree of superheat is $1^{circ}C$ and condensed pressure is 14.5bar, the refrigeration system showed the high performance.