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 {TAIL ~ removal} is located in the area of increased vapor velocity 
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 { TAIL ~ removal } is located in 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 REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH