VDI-Buch 2010, pp 701-708

G2 Heat Transfer in Concentric Annular and Parallel Plate Ducts

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1 Introduction

The simplest form of a two-fluid heat exchanger is a double pipe made up of two concentric circular tubes. One fluid flows through the inside tube and the other in co-current- or countercurrent flow through the annular passage. Heat exchangers of this type are common practice if liquids at high and very high pressures have to be either heated or cooled.

Beside separate double-pipe heat exchangers, heating or cooling jackets for tubes are of this type. But annular passages may also occur as heat exchangers in other types, for example, to heat a fluid by electricity, either a heating-rod is put into the middle of a circular tube, or the fluid in the annulus is heated or cooled from the outer tube, and an inert rod is placed in the middle of the tube to increase the velocity of the fluid in the gap. Finally, the fluid flowing in the annulus is either heated or cooled from both sides, from the inner tube and from the outside of the outer tube.

2 Flow in the Annulus;