Coiled smooth-tubular heat exchanger with improved heat properties

Abstract

Coiled tubular heat exchangers are widely used in power generation, cryogenics, and in the gas, petroleum, and chemical industries and other areas of industry. Among the large number of designs for equipment of this type, a coiled smooth-tubular heat exchanger [1][2][3], which consists of a bundle of smooth tubes wound as coaxial layers onto a cylindrical core, is the most commonly used. Spacers are arranged as straight strips between the layers of tubes to form circular channels for passage of gas in the intertubular space. The tubes are in an unstaggered arrangement.The heat exchanger has high reliability and adaptability and is fairly compact. However, it has a number of design shortcomings.With layer winding of the tubes it is virtually impossible to achieve a fixed width for the circular channels in all the tubular layers. It only occurs discretely in different positions of the spacers. The varying width of the circular channels results in a nonuniform flow of gas in the intermbular space and consequently to a deviation of the aqueous equivalents of the heatexchanging flows from the calculated ratios. As a result of this, it is not possible to achieve high efficiency values in the traditional designs of coiled smooth-tubular heat exchangers [4, 5]. Moreover, heat transfer is insufficient in the unstaggered bundle because of the incomplete flow around the whole perimeter of the tubes.These shortcomings can be eliminated if the umtaggered arrangement of the tubes is changed to a staggered one (Fig. 1). A staggered arrangement of the tubes produced with specially profiled spacers achieves a more complete and uniform flowround, so that quite high heat efficiency values can be obtained and the degree of heat exchange increased.The profiled spacers can generally be made with any ratio of longitudin~i (t2) to transverse (q) pitch, but the optimum ratios [6, 7] are: \

Review of the micro-tubular solid oxide fuel cell

“…This is just a design and there is no performance data available on how well the heat exchanger works but it seems that it could work quite well. Indications of the advantages of similar coiled heat exchangers have been shown elsewhere by [16][17][18][19].…”