Research On Natural Convection Heat Transfer Characteristic Of The Vertical Finned Tube

As a kind of strengthened heat transfer element, the finned tube is widely applied to the heat exchanger equipments. Because of its various structures and changeable applied range, the deeper research on the finned tube has important theoretic sense and usage value. The natural convection heat transfer and the flow characteristic of the vertical finned tube is researched through numerical simulation and experiments in this thesis.The natural convection heat transfer model of the vertical finned tube has been established, and then the specific computation methods are determined. In order to reduce the computation quantity, the orthogonal experimental method is leaded in. The influence of the tube height H, the fin height l, the included angle 6 and the fin spacing S₁ are discussed. According to the numerical simulation results of the single finned tube, with the increase of the tube height, the heat dissipating capacity will be increased, but the unit quality heat dissipating capacity will be decreased. When the included angle is fixed and the fin height is 30 mm, 40 mm, 50 mm, 60 mm or 70 mm, the finned tube with the fin height of 70 mm has the largest unit quality heat dissipating capacity. When the fin height is fixed, whether the included angle is oversized or excessively small, the heat dissipating capacities are both low. The included angle is changed from 30° , 60° , 90° and 120° . The best included angle is 30° when the fin height is 70 mm, the best included angle is 60° when the fin height is 30 mm, 40 mm, 50 mm or 60 mm.In order to discuss the influence of the fin spacing on the heat transfer, the numerical simulation of the vertical finned tube rows has been carried, where tube height is varied from 400mm, 500mm, 600mm, 700mm and 800mm, the variation scope of fin spacing is 0mm, 10mm, 20mm, 30mm and 40mm. With the increase of the fin spacing, the total heat dissipating capacity will be increased, but the unit volume heat dissipating capacity will be decreased. The best fin spacing of the 400 mm height tube row is 0 mm, the best fin spacing of the 500 mm height and 600 mm height tube row is 10 mm, the best fin spacing of the 700 mm height tube row is 20 mm, and the best spacing of the 800 mm height tube row is 30 mm. According to the synthetical analysis of the tube number and the tube height, the principle of choosing tube row is that the tube number should be more and the tube height should be lower. The radiating heat has been analyzed too. The proportion of radiation heat transfer of the single finned tube is 36.5%⁴9.2%, and the proportion of radiation heat transfer of the finned tube row is 29%～39%. The suitable choice of the fin height, the tube height and the fin spacing is contribute to the radiation heat dissipating capacity. After analyzing mass data and synthesizing various factors, the criterion equations of the single tube and the tube row of natural convection heat transfer are fitted. It provides the basis for designing the finned tubes.The heat transfer laboratory bench is established. The experiments to the single tube and the tube row are carried separately. Comparing the data of experiments and numerical simulation, the conclusion is identical. Although the value had certain deviation, the data agree with relatively.The above research has provided the beneficial theory basis for whole optimization and calculation of the finned tube, and the important guiding significance for production and practical application as well.