The variable cross sectional vapor passage first increases and then decreases the rate of vapor flow, and {HEAD ~ a further heat transfer zone} with either heat supply or removal is located in {TAIL ~ the area} of increased vapor velocity 
is located in
The variable cross sectional vapor passage first increases and then decreases the rate of vapor flow , and { HEAD ~ a further heat transfer zone } with either heat supply or removal is located in { TAIL ~ the area } of increased vapor velocity
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH