The tubes form passages for flow of the hot gaseous mixture in heat exchange contact with the gaseous fluid through the heat exchanging chamber, thereby preheating the gaseous fluid prior to {HEAD ~ reaction} with {TAIL ~ the fuel} 
with
The tubes form passages for flow of the hot gaseous mixture in heat exchange contact with the gaseous fluid through the heat exchanging chamber , thereby preheating the gaseous fluid prior to { HEAD ~ reaction } with { TAIL ~ the fuel }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL