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