Heat exchanger having improved tube layout

In a heat exchanger for exchanging heat between fluids and having a plurality of parallel tubes of circular cross-section, said tubes all having the same outer diameter, the improvement wherein said tubes are laid out according to the following relationship:

• (1) said tubes are arranged with their centres located on a set of concentric circular arcs, said set comprising at least first, second and third such arcs, a plurality of tubes on each arc,
• (2) the number of tubes in each arc differs from the number of tubes in each other arc by not more than one,
• (3) the tubes in each arc are spaced uniformly apart along such arc,
• (4) each tube in each arc, other than such end tubes as may be present in some of said arcs, is located circumferentially midway between the two adjacent tubes of each neighboring arc so that the centres of each such three tubes form an isosceles triangle, each tube in each arc being separated from each of said adjacent tubes in each adjacent arc by a diagonal ligament distance h, said distance h being constant for all said tubes, and
• (5) the distance between each two adjacent tubes in any said arc is at least as great as twice said diagonal ligament distance h, so that the minimum cross-sectional area for radial fluid flow between adjacent arcs of said set is defined as to its circumferential dimension by the sum of said diagonal ligament distances h between the tubes of said adjacent arcs and is substantially constant independent of the radial position of said arcs.