which fluid is pass on shell side and which pass in tube side in shell and tube type heat exchenger./?
It depends..... 1] If you have one fluid which is very corrosive, generally you would put it in the tubes, since that way only the tubes [and tube end header] need be made of the expensive corrosion resistant alloy; the shell can be carbon steel. 2] Fouling can influence the choice. If you expect bad fouling problems, using straight through tubes with the fouling to happen inside the tubes will allow much easier cleaning. I was working in a paint plant when a batch of resin set up in the reactor. Said reactor contents were heated with an external heat exchanger instead of the more usual jacket. So they had to drill out every tube in the heat exchanger to remove the gelled polymer, but even though that was a royal pain, it was far far easier than chipping it off the outside of the tubes would have been [especially since they would not have been able to get at the outside of the tubes in the center of the bundle]. 3] I note you say fluid, not liquid. If you are using condensing steam [or other vapor, eg, Dowtherm], better it go on the shell side. Or if you are boiling one liquid.
Hot fluid in the shell and cold fluid in tube
