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