1.we are choosing 2 pass he over 1pass heat exchanger because in
2 pass he we are paaing same quantity of fluid through more surface
areae(ie 2 passes)
2.1st benefit of using many tubess is heat transfer Q =hA(T2-T1)
proportional to A ,therefore heat transfer
increases.Another benefit is that ,since we are using many tubes
for a certain quantity .flow area is decreased,means velocity
increased,(Q=AV is const).the heat transfer coefficient varies with
respect to velocity(approximately h proportional to 0.8 th power of
v.so if velocity doubles,h will become 1.74 times initial value,so
Q=hA(t2-t1) increases
3,materials used commonly are carbonsteel,stainless
steel,brass.bronze,titanium alloys
