Closure to “Discussion of ‘An Experimental Study on Heat Transfer Surface Area of Wavy-Fin Heat Exchangers’ ” (2014, ASME J. Therm. Sci. Eng. Appl., 6(3), p. 015501)

Abstract

Plate-fin heat exchangers and tube-fin heat exchangers with wavy surfaces are characterized by high compactness and excellent heat transfer performance [1]. Early data on geometries of wavy surfaces were presented by Kays and London [2]. Three sets of geometries were studied by using the air as working fluid. This paper presents a discussion on two recent pressure drop and heat transfer models introduced by Awad and Muzychka [3] and Asadi and Xie [4].Awad and Muzychka [3] studied on thermal-hydraulic performance of an air-cooled compact heat exchanger with wavy surfaces. They developed a new model by combining the asymptotic behavior for the low Reynolds numbers and laminar boundary layer regions. They used this model for predicting friction factor (f) and Colburn factor (j) in a wide range of Reynolds numbers. They found that their results were in good agreement with the previous experimental investigations and then concluded that their present model was quite accurate given the uncertainties in heat exchanger core manufacture, even if the RMS errors are high.Then, Asadi and Xie [4] presented a new model to evaluate the thermal-hydraulic performance of wavy surfaces. They proposed a direct method to calculate the heat transfer area of compact heat exchangers, which plays a key role in reducing pressure drop and improving the heat transfer characteristics. In Awad and Muzychka's model [3], the geometrical parameters such as fin height, fin spacing, wave amplitude, fin wavelength, Reynolds number, and Prandtl number were accounted. Such proposed model is generally applicable. The results of Asadi and Xie [4] showed that their model might be a strong tool in optimization of wavy surfaces under different objective functions. Recently, these authors used this model with the help of Constructal Theory [5] to improve the thermal performance of a corrugated-wall channel. More information can be found in the Refs [6] and [7].