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