Designing Shell & Tube Heat Exchangers: Avoid Vibration From The Start

Mechanical integrity is an essential consideration in heat exchanger design. The most common threat to this integrity is tube bundle vibration. So, the computer programs used for heat exchanger design incorporate procedures that assess this threat. However, such analysis is generally undertaken after exchanger geometry has been identified. The result can be that geometry that is optimal in terms of thermal performance is rejected for a more expensive alternative. This added expense is often unnecessary. This article shows that identification of geometry that avoids dangerous vibration can be undertaken as an integral part of the design process and provides insight on doing so. (Part 2 of this report, pp. 35–38 addresses the challenges of two-phase flow) Modern computer programs allow the engineer to explore a very wide range of bundle geometry. Baffle cut can be set anywhere within the range 15 to 45% and baffle spacing up to a maximum allowable span set by manufacturer’s standards. Beware, however, that the fact that a computer program provides a prediction of performance (sometimes of questionable validity) for a poor geometry does not justify the engineer in accepting the result. The best heat transfer is obtained for…