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