Abstract: From the viewpoint of rational utilization of energy, the available energy of con-vective heat transfer enhancement in a tube was studied by energy analysis. The enhancement usually not only increases heat transfer, but also raises flow resistance. Since the heat transferred and the work done in flow , both are different forms of energy, Energy was used to combine heat transfer with flow resistance. Several dimensionless factors and a dimension-less equation about the available energy lost (or exergy lost )were presented to analyse and appraise the enhancement. The Kenics static mixer was taken as a example for study . The theoretical analysis and the example studied showed that this equation can be used as an analysis criterion for enhancement investigation and engineering application.