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Conference Article: Analysis of heat exchanger bundles operated at elevated temperatures

Abstract

Heat exchanger equipment operating at elevated temperatures has to be designed with careful consideration of the effects of creep and other time-dependent phenomena. In this regime the crucial material properties become very sensitive to the most important parameter, temperature. Therefore it is essential to avoid as much as possible all effects that increase the material temperatures above that which is needed for the process. Since the absence of significant hot gas streaks in the primary gas cannot be guaranteed, the design of the bundle should minimize their effect on the temperatures in the secondary gas and in the metal of the heating surface and the header. The bundle with helically coiled tubes, as it is used, e.g. in the steam generators of the Thorium High Temperature Reactor (THTR), has this distinctive feature: The individual tubes see hot streaks as well as cold ones and therefore average out the fluid temperatures. In addition, gas velocities at the entrance of the bundle can be kept fairly uniform and gas mixing in cross flow is relatively efficient. Gas bypass at the boundaries of the bundle, which might also cause excessive temperatures, can be kept under control. A bundle with helically coiled tubes is still subject to a number of loadings that have to be considered in design. Comments on the analysis of such a bundle are given.

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Reference:

Specialists' meeting on process heat applications technology. Juelich, Germany, F.R. 27 - 29 Nov 1979

International Atomic Energy Agency, Vienna (Austria). International Working Group on High-Temperature Reactors.

IWGHTR--6, pp:87-94