The selection of {HEAD ~ heat source vapors} and heat sink liquid is such that at least one is withdrawn from {TAIL ~ the phase contracting region} of the distillation system 
The selection of { HEAD ~ heat source vapors } and heat sink liquid is such that at least one is withdrawn from { TAIL ~ the phase contracting region } of the distillation system
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH