Based on the reliability theory and material mechanics theories

Indicated the reliability factor in CO 2 transcritical refrigeration and heat pump systems that were influenced by the high operate pressure of the system. The vary law of the reliability degree

when the inside pressure changing

was attained. In terms of the various factors and change laws

the ways that can be improve the reliability of CO 2 transcritical systems were: enhancing the thickness of the pipes properly

enlarging the allowable pressure or both of the them. All of this could provide essential theory basis for further studing and exploiting the CO 2 transcritical refrigeration and heat pump systems.