安全阀定压P s 为1.52MPa,天然气泄放量1.5×10 4 m 3 /h,温度18℃,选用弹簧全启式安全阀,安全阀所需最小喉径为 ____ 。(天然气摩尔成分:CH 4 96%,C 2 H 6 0.8%,C 3 H 8 0.2%,CO 2 2.8%,N 2 0.2%,K取0.7,Z取0.97)
天然气定压比热容:
C p =∑y i Cp i =(1.55×0.96+2.24×0.008+2.96×0.002
+1.62×0.026+1.3×0.002)kJ/(m 3 ·K)=1.56kJ/(m 3 ·K)
定容比热容:C V =(1.56-0.371)kJ/(m 3 ·K)=1.19kJ/(m 3 ·K)
则比热容比为:
安全阀出口侧压力:P 0 =0.1MPa(绝压)
泄放压力:P d =1.52×1.1+0.1=1.772MPa(绝压)
属临界条件,采用
天然气分子量为:
M=∑y i M i =16.04×0.96+30.07×0.008+44.01×0.002+44.01×0.028
特性系数分别为:
K=0.7,Z=0.97。
天然气密度为:
ρ=∑y i ρ i =0.7174×0.96+1.3553×0.008+2.01×0.002+1.9768×0.028+1.2507×0.002=0.7614kg/m 3
W s =1.5×10 4 ×0.7614=11420kg/h
因此,