{HEAD ~ Air} is forced through the tube bundle by either a draft induction blower located at the outlet end of the tube bundle or a forced draft blower located at {TAIL ~ the inlet} 
{ HEAD ~ Air } is forced through the tube bundle by either a draft induction blower located at the outlet end of the tube bundle or a forced draft blower located at { TAIL ~ the inlet }
HEAD HEAD HEAD HEAD HEAD 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 TAIL TAIL TAIL TAIL TAIL TAIL