In {HEAD ~ operation}, the gas flows through the body 6 from {TAIL ~ the inlet end} 7 in an axisymmetric profile 
In { HEAD ~ operation } , the gas flows through the body 6 from { TAIL ~ the inlet end } 7 in an axisymmetric profile
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH