Research On Flow Field And Heat Exchange Characteristics Of Heat Exchanger Tube With Sectional Spring Inserts

Coil spring inserted tube as enhancing heat transfer technology was widely used in engineering production. Although this technology can improve the heat transfer coefficient, but it also can increase the pressure drop and the resistance coefficient. In this paper, using sectional spring inserted tube to analyze the flow and heat transfer process through the combination method of theoretical analysis, numerical simulation and experimental study. The main contents and conclusions are as follows:(1) Combined with some scholars’ study, making an exploratory research on the mechanism of heat transfer enhancement of the sectional spring inserted tube. Spring dynamics theory was used to analyze the relationship between the axial velocity and the spring parameters. The results showed spring with larger pitch, smaller circle diameter and larger wire diameter had a great effect on the axial velocity and the vibration. Then when the Reynolds number was different, the field synergy angle’ relationship between a smooth tube and sectional spring inserted tube was obtained by the field synergy principle, which was helpful to design a good disturbed flow components. The results showed the way to insert sectional spring in tube can not only improve the heat transfer coefficient, but also can reduce the resistance coefficient. It has a great significance to improve the efficiency of heat transfer enhancement.(2) The effects of different length, pitch, wire diameter and circle diameter spring on the flow field, heat transfer and pressure drop was simulated by the FLUENT software. The results showed that: Nusselt number of sectional spring inserted tube was increased 2~4 times than Nusselt number of smooth tube, and compared with the nonsectional spring inserted tube, the resistance coefficient was decreased about 3 times.By simulating different parameters sectional spring’ pressure fields and temperature fields, it was found that sectional spring with larger pitch, larger wire diameter and smaller circle diameter can bring better effects. The conclusion was consistent with the theoretical analysis in the previous chapter, the method of sectional spring inserted tube is helpful to achieve the purpose of heat transfer enhancement.(3) The PIV experimental platform of inserted sectional spring tube was established. The particle imaging velocimetry technology was used to measure and research the changes of flow field in the sectional spring inserted tube. And the effects of different parameters(pitch, wire diameter and circle diameter) of sectional spring on flow field was PIV experimental studied. The results showed that the distribution of the vorticity field and velocity field in sectional spring inserted tube is better than smooth tube. It was found that the axial velocity was increased by about 1.2~1.6 times and the radial velocity was presented M type fluctuation. The average velocity was a linear relation with Reynolds number. And the effects of sectional spring with larger pitch, larger wire diameter and smaller circle diameter inserted tube was best. The conclusion was consistent with the conclusions of theoretical analysis and numerical simulation, which can verify the accuracy of theoretical analysis and numerical simulation.