R. Wejkowski

Heat Transfer and Pressure Loss In Combined Tube Banks With Triple-Finned Tubes

This paper presents experimental and analytical results of an investigation of heat transfer and pressure loss in a new type of convection heat exchanger tube bank with triple-finned tubes (TFTs). An initial evaluation of the optimal geometry of TFT banks using the Lusas code is presented. The heat transfer between the external environment and the medium inside the TFTs was modeled. Fins were arranged on a tube in the following three configurations: three fins with the same geometry with 45° between two symmetric fins and a vertical line of symmetry, denoted by T90, three fins with the same geometry with 30° between two symmetric fins and a vertical line of symmetry, denoted by T60, and one fin and angle steel plate placed parallel to the line of symmetry of the triple-finned tube, denoted by TAS90. The naphthalene sublimation technique is used as a heat/mass transfer analogy to evaluate the Sherwood (Nusselt) number ratios in the tube banks. The heat transfer performance of staggered S1T90 tube banks and the basic plain tube bank SP was compared. The second possibility for using TFTs is in a tube bank with all tubes finned was studied using the naphthalene analogy technique. The results are then compared with those computed using the computational fluid dynamics code. A comparison of the numerical and experimental heat transfer results shows that the trends in the heat transfer increase are very similar. The results show that triple-finned tubes can be used to increase the performance of cross-flow tube banks.

Heat Transfer and Pressure Loss in Combined Plain and Diagonally Finned Heating Surfaces

This paper presents the results of model investigation of the heat transfer in plain and combined plain and diagonally finned convective tube banks. A heat and mass transfer analogy, by means of a naphthalene sublimation technique, is used. The effect of tube bank arrangement on heat transfer coefficients and flow resistance is discussed. The results show an increase of Nusselt numbers in comparison to those obtained for plain tube arrangements; however, a significantly higher flow resistance accompanies this increase.