The invention 11 wherein {HEAD ~ said wall member} has {TAIL ~ an elongated opening}, and wherein said gas flow inlet extends through said elongated opening 
The invention 11 wherein { HEAD ~ said wall member } has { TAIL ~ an elongated opening } , and wherein said gas flow inlet extends through said elongated opening
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH