TUBES DESIGNING OF COIL-WOUND HEAT EXCHANGER

Abstract

Coil-wound heat exchangers are widely used in the production of liquefied natural gas. The heat exchange surface of it is composed of concentrically wound tubes around the central core tube. The purpose of this work is to develop a method for designing the heat surface in coil-wound heat exchangers. Designing of the tube, the geometry of which is a spiral, is a laborious task. There are different types of winding depending on the size of the distance between the tubes, both in the longitudinal and radial directions. In addition, the designing should take into account the dependence between the diameter of spiral, the pitch of the spiral and the average length of the tubes in the apparatus. The developed designing algorithm, based on the iterative method of selecting the optimal option, allows getting the number of tubes in each row of winding with an equal length of tubes in all rows. The lengths of all pipes in the heat exchange zone must be equal so that the flow residence time in the tubes should be the same. Therefore, the spiral pitch on the peripheral rows should be greater than on the central ones. And the number of tubes in the peripheral rows will be greater than in the central ones too. It is proven that the angle of spiral inclination in different rows of winding should be the same. The tubes become straighter if an increase in the angle of spiral inclination and the total number of tubes is growing, but the length of each tube reduces.