Experimental study of heat transfer and hydraulic resistance at cross flow of tube bundle with indentations

Abstract

The results are given on experimental study of heat transfer and hydraulic losses at the cross flow of a five-row tube bundle arranged in the staggered mode, the external surface of which is covered with conic-shaped dimples. The tube’s spatially averaged heat transfer was measured by means of the melting ice technique. As a result, the heat transfer coefficients were determined both for separate tube rows and the whole bundle. The hydraulic losses of the tube bundle were also found for the same conditions in the form of the Euler number. The Reynolds number was defined on the external tube diameter and flow velocity in the minimal cross section of the bundle and was in the range of 3000…25000. In the heat transfer determination, the surface of a smooth cylinder was used without the surface of the dimple area. The heat transfer augmentation rate of 34…40 % at the pressure losses growth by 10…15 % was obtained. The Reynolds analogy factor (thermal performance) value is 1.17…1.27. The similarity relations for the Nusselt number and Euler number as a function of the Reynolds number were obtained. These relationships allow determining the coefficients of heat transfer and hydraulic resistance in the development of tube-type heat exchange equipment. The results of this study can be used for the development of compact tube-type heat exchangers with a high thermo-hydraulic performance parameter.