Numerical Study Of Heat Transfer Performance Of Rectangular Finned Elliptical Tube Heat Exchanger

As a process equipment of heat transfer, the heat exchanger is widely used in the industry. With the situation of shortage of all the energy, the reasonable design, operation and improvement of heat exchanger is very important for saving money, materials, energy and space. As a kind of compact heat exchanger, the finned tube heat exchanger is widely used in the industry, such as power, chemical industry, and refrigeration industry, and it has a high efficiency of heat exchange. Usually, the base pipe is circle pipe, research shows that the elliptic tubes have smaller resistance losses, so it will have better guidance significance for the study of rectangular finned elliptical tube heat exchanger for its Practical effect in the project.In this paper, we had done a numerical simulation and structure optimization on the fin structure of the rectangular elliptical tube, by the combination data of the orthogonal experiment; we concluded that the best combination of the fin structure is fin length for 55mm, fin width for 32mm, and fin thickness for 0.3mm.By using the method of numerical analysis, we have done the structure optimization and analysis on a four rows of elliptical tubes with rectangular fin in staggered row arrangement from the tubes horizontal spacing, longitudinal spacing, fins spacing, air velocity, air temperature, and the material aspects. The results show that with the increase of the tubes horizontal spacing and longitudinal spacing, the comprehensive evaluation factors get improved and the extent of improvement has a great relationship with the entry air velocity; as the fin spacing increases, the comprehensive evaluation factors get improved, however, while the fin spacing reaches to a certain value, the increase rate becomes small.By using the method of numerical analysis, we have done the structure optimization and analysis on a four rows of elliptical tubes with rectangular fin in staggered column arrangement from the tubes horizontal spacing, longitudinal spacing, fins spacing, air velocity, air temperature, and the material aspects. The results show that while the tubes longitudinal spacing is less than 16mm, the growth rate of Nu/Eu is small, and when air velocity reaches 7.57 m/s, the performance shows descending tendency; when the tubes longitudinal spacing is greater than 16mm, the Nu/Eu is increasing. With the increase of the tubes horizontal spacing, the Nu/Eu shows increscent tendency, but while the tubes horizontal spacing reaches 78mm, it tends towards stability that shows keeping on increasing the tubes horizontal spacing has basically no influence on the heat exchange; when the tubes horizontal spacing is between 66mm and 78mm, Eu is stable, the Nu/Eu is increasing, so the optimization structure size should be 78mm. Along with the increase of the fin spacing, the performance of heat exchange wears off, and while the fin spacing reaches a certain value, the influence of the fin spacing for heat exchange becomes small.Although the increase of air velocity of the entrance can enhance the heat transfer, the increase amplitude of resistance is relatively greater. The increase of air temperature of the entrance makes the heat transfer effect poor, and the resistance also increases. The bigger of the thermal conductivity of the materials, the better of the heat exchange effect. While the air velocity is fixed, with the increase of the tube rows, the heat transfer coefficient is decreasing gradually, and as the air velocity increases, the distribution of the temperature of the entire flow field is even, the heat transfer effect of the whole flow field is enhanced.By using the method of numerical analysis, this paper made comparisons between the two different structural models in the aspect of thermal performance. The results show that the Eo of staggered column arrangement of the elliptical tubes with rectangular fin is higher relatively, and the maximum is about 38% higher than that of staggered row arrangement of the elliptical tubes with rectangular fin, in addition, the former can get a better heat transfer effect with less metal materials.