The middle nozzle provides {HEAD ~ water}, air or {TAIL ~ other chemicals} as coolant to insulate the inner nozzle 
The middle nozzle provides { HEAD ~ water } , air or { TAIL ~ other chemicals } as coolant to insulate the inner nozzle
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH