A revised performance evaluation method for energy saving effectiveness of heat transfer enhancement techniques

In this paper, a revised performance evaluation method was proposed to estimate the thermal hydraulic performance of various heat transfer enhancement techniques. The energy saving effectiveness for the enhanced structures can be identified via a plot. In the plot, Reynolds number and the efficiency index ln(Nu(e)/Nu(r))/ln(f(e)/f(r)) are taken as the X and Y coordinates, respectively. The efficiency can be ranked into four different levels. For experimental data or simulation results in Level 1, enhanced heat transfer is accompanied with more power consumption. The data in Level 2 is that the heat transfer can be intensified at the same pumping power. In Level 3, it is characterized by the augmented heat transfer at the same pressure drop. The efficiency in Level 4 is the highest. The ratio of heat transfer augmentation is higher than the increment ratio of friction factor at the same Reynolds number. Four levels correspond to four horizontal regions with Level 1 at the bottom and Level 4 at the top. The data at higher levels in the ordinate will be more competitive for energy saving. The examples on how to use the method for evaluating the performance of enhanced surfaces and typical heat exchangers were also presented. (C) 2019 Elsevier Ltd. All rights reserved.