when analyzing heat transferfrom a tube bank in cross flow,we must consider all the tubes inthe bundle at once. The tubes ina tube bank are usually arrangedeither in-line or staggered in thedirection of flow

•Pipes with a circular cross section can withstand large pressure differences

•Noncircular pipes are usually used where the pressure difference is relatively small and the manufacturing and installation costs are lower

•For a fixed surface area, the circular tube gives the most heat transfer for the least pressure drop,

laminar flow can be maintained at much higherReynolds numbers in very smooth pipes by avoidingflow disturbances and tube vibrations. In such arefully controlled experiments, laminar flow has beenmaintained at Reynolds numbers of up to 100,000.