Comments on “Experimental study on thermal–hydraulic performance of a wavy fin-and-flat tube aluminum heat exchanger”

•These comments are increasing the awareness among the journal readers.•Comments are presented in particular on the paper by Dong et al. [1].•Thermal-hydraulic models of Awad and Muzychka [2] have only 1 unknown.•Thermal-hydraulic correlations of Dong et al. [1] have 6 unknowns. These comments are presented to increase the awareness among the readers of Applied Thermal Engineering. Comments are presented in particular on the paper by Dong et al. (2013) where the authors investigated experimentally the air side thermal-hydraulic performance of a wavy fin-and-flat tube aluminum heat exchanger. Dong et al. (2013) did not mention some available thermal-hydraulic correlations in the literature like thermal-hydraulic correlations of Awad and Muzychka (2011). In addition, Dong et al. (2013) developed air-side friction and heat transfer correlations for wavy-fin compact heat exchangers. Their Fanning friction factor (f) and Nusselt number (Nu) correlations have six unknowns (one constant and five exponents). On the other hand, thermal-hydraulic correlations of Awad and Muzychka (2011) have only one unknown (the fitting parameter in the asymptotic model). For the aim of calculation and design of air cooled compact wavy fin wavy-fin heat exchangers, having only one unknown in thermal-hydraulic correlations of Awad and Muzychka (2011) is better than having six unknowns in thermal-hydraulic correlations of Dong et al. (2013).