Interpretation of fouling data in industrial shell and tube heat exchangers

An improved method of analysis is presented for the interpretation of fouli ng in shell and tube heat exchangers. The method reveals weaknesses that ar e inherent in commonly used but simpler approaches to the interpretation of plant data. It is shown, for example, that by neglecting the effect of by- passing and the effect of heat transfer coefficient variation through an ex changer, it is possible to become misled into believing that a heat exchang er may be fouled when actually it is clean. The improved method of analysis shows that the corresponding 'apparent fouling resistance' of a clean heat exchanger is higher the lower its temperature effectiveness. The improved method is applied firstly to a hypothetical heat exchanger located in a tra in of clean exchangers and secondly to the shell and tube exchangers in an oil refinery crude preheat train.