{HEAD ~ A multitubular catalytic reactor} for exothermal catalytic reactions comprises {TAIL ~ a bundle} of parallel tubes all of the same length and a catalyst within the tubes 
comprises
{ HEAD ~ A multitubular catalytic reactor } for exothermal catalytic reactions comprises { TAIL ~ a bundle } of parallel tubes all of the same length and a catalyst within the tubes
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH