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Basic introduction to heat transfer design

The heat transfer design involves the distribution of fluid flow and the temperature field. On the one hand, the internal characteristics of the heat exchanger cannot be obtained by solving the differential equations of fluid flow and heat transfer control, which is due to the current basic mathematical knowledge and the development level of theoretical fluid mechanics. In engineering practice, it is usually based on a simplified heat exchanger model, using similar principles to measure fluid flow and heat transfer data, and then obtaining characteristic parameters close to the actual situation through amplification and other data processing methods. Essien. However, due to the increasing application of heat exchangers and the complexity of their own structures, traditional experimental methods and theoretical methods have been difficult to meet the needs of research and development in this field. On the other hand, with the development of modern computer technology and the development of advanced numerical algorithms, computational fluid dynamics (CFD) and computational heat transfer (NHT) technologies have developed rapidly worldwide since the 1960s. The use of CFDHT technology to study the heat exchanger has the advantages of low cost, high speed, complex simulation and ideal process. At the same time, you can observe the impact of different operating parameters on solving the problem, get detailed information of all relevant variables and potential physical processes. Therefore, the use of simulation data to evaluate, select and optimize the actual design, and through limited experimental inspection results, can greatly reduce the amount of work and funding required for research. However, the accuracy of numerical simulation is related to mathematical models and numerical methods, and is limited by the capacity of the computer.

There are many types of finned tubes. The finned tube has two kinds of inner finned tubes and outer finned tubes according to different mounting positions of the fins, and the outer finned tubes are more commonly used. Depending on the arrangement of the fins, there are two types of finned tubes: longitudinal finned tubes and horizontal finned tubes. According to the shape of the fin tube, the fin tube has a round fin tube, an elliptical fin tube, and a flat tube fin tube. At present, the circular finned tube heat exchanger dominates the market, but a large number of experiments have shown that the reflow area and the windward area of ​​the elliptical tube are much smaller than the round finned tube, effectively reducing the flow resistance of the air side A. Reduced energy consumption. When the number of tube bundles is present at the same time, the elliptical tube and the flat tube are tighter than the round tube structure. The heat exchanger is small in size and reduces the cost. Therefore, the research and development of elliptical tube-fin heat exchangers has attracted more and more scholars' attention.