sensing {HEAD ~ the temperature} of {TAIL ~ reaction products} at said outlet side of said tube bundle; and 
sensing { HEAD ~ the temperature } of { TAIL ~ reaction products } at said outlet side of said tube bundle ; and
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH