In view of the applicability of calculation method of safety valve exhaust flow rate in the field of supercritical carbon dioxide(S-CO_2)

the thermodynamic model of safety valve exhaust flow rate calculation is given. On the premise of considering the influence of actual gas

the derivation process and premise assumptions of two calculation methods in DL/T 5054 and ASME B 31.1 are analyzed

and the characteristics of the two methods in the calculation of flow rate of superheated steam safety valve exhaust are compared. The influence of some important factors on the calculation results is semi quantitatively analyzed

and the parameter value of the second calculation method is modified. The calculation results show that

when the first method and the second method(after modification) are applied to the calculation of the exhaust pipe of S-CO_2 safety valve

the former has a large deviation and the latter is more accurate. The modified second method is recommended for S-CO_2 with the new parameters: k=1.2

a=115 kJ/kg

b=6.