You have designed two heat exchangers to do the same thermal job [i.e., they have the same
Question:
You have designed two heat exchangers to do the same thermal ‘‘job’’ [i.e., they have the same q and total tube-side mass flow rate m1 t (kg/s)]. A comparison of these heat exchangers shows the following:
Assume constant and identical fluid properties for both heat exchangers.
(a) Calculate P/Ps, where the subscript s is for the smooth tube.
(b) Calculate p/ps.
(c) Suppose that P/Ps is 0.8; how would you alter the rough tube exchanger geometry to make P/Ps = 1, keeping the same rough tube length? Give quantitative estimates considering no change in the friction factor.
(d) How would you expect UA to change for part (c)? Give explicit reasons whether it will increase, decrease, or will have no change.
Fundamentals of Heat and Mass Transfer
ISBN: 978-0471457282
6th Edition
Authors: Incropera, Dewitt, Bergman, Lavine