GB796004A - Improvements relating to tubulous heat exchangers and heat exchanger tubes - Google Patents

Abstract

796,004. Tubular heat exchange elements; feedwater heating systems. BABCOCK & WILCOX, Ltd. Aug. 2, 1956 [Aug. 5, 1955], No. 23842/56. Classes 64(1) and 64(3) In a tubular heat exchanger such as an economiser or steam generator in which heating gases flow longitudinally over the tubes, each tube 26 is formed with four, plain, longitudinal fins 27 such that with respect to each of two transverse axes drawn through the tube section, the fins are disposed in symmetrical, opposed pairs (Figs. 4 and 5 showing alternative forms), the tubes being arranged in rows (Fig. 5), with each tube positioned in two mutually transverse rows, the tubes being spaced apart at their closest points by a distance less than the height of the fins and the arrangement being such that in the zones 31, 32 outside the tubes, the opposed heat exchange surfaces each comprise approximately a quarter of the. circumference of a tube between lateral faces of adjacent fins 27, and each has a development at least three times greater than the width of the passage space between opposed heat exchange surfaces. Preferably, the space within each tube is divided into four outer fluid conducting zones 30 (Fig. 4), and a central zone 29 of square cross-section communicating with a zone 30 but itself closed with respect to fluid flow, each fin 27 having its root located adjacent that part of an outer zone 30 of greatest radial depth. Figs. 1 and 2 show an economiser located at the inlet of a first of a series of steam generating units (not shown) arranged for example as described in French Specification 1,128,733. The economiser comprises a vertical cylindrical casing 1 the central zone of which is partitioned into a plurality of gas ducts, comprising four ducts 13 of segmental cross-section interconnecting in series four ducts 10 of square crosssection each containing a bank of heat exchange tubes. The arrangement is such that the heating gases flow downwardly in the ducts 10 in sequence A, B, C, D and ultimately to a gas outlet 8. The tube banks are also series-connected, the water to be heated flowing from an inlet 24 upwardly through the tubes of each bank and thence to an outlet 25.