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keywords] Summary of comparison of heat transfer and flow resistance performance of different baffle heat exchangers] Thermal equipment plays a vital role in the chemical process, and its investment costs generally account for about 40% of the total investment costs. The traditional shell-and-tube heat exchanger has a low heat transfer area per unit volume and a low heat transfer coefficient, making it difficult to meet production requirements. Therefore, the research on high-efficiency heat exchangers has received more and more attention. The spiral baffle heat exchanger is a heat exchanger that has recently appeared with high efficiency. 1 Introduction Heat exchange equipment plays a vital role in the chemical process, and its investment cost generally accounts for about 40% of the total investment cost. The traditional shell-and-tube heat exchanger has a low heat transfer area per unit volume and a low heat transfer coefficient, making it difficult to meet production requirements. Therefore, the research on high-efficiency heat exchangers has received more and more attention. The spiral baffle heat exchanger is a type of heat exchanger that has recently appeared with high efficiency. Spiral baffle The heat exchanger breaks through the traditional concept that the shell-side medium flow is transversely vertical and the tubes are tangential. The fluid flows in a continuous plunger-shaped spiral on the shell side (i.e., plug flow). There will be no flow "dead zone" in the traditional baffled heat exchanger. Moreover, due to the interaction between the vortex generated by the swirling flow and the boundary layer of the tube bundle heat transfer interface, the degree of turbulence is greatly enhanced, which is conducive to improving the shell-side heat transfer film coefficient [1].PStehlik [2] studied the spiral baffle heat exchanger and found that compared with the traditional arcuate baffle heat exchanger under the same conditions, the heat transfer coefficient of the heat exchanger was increased by 1.8 times, and the flow resistance was reduced by 25%. Chen Shixing et al. [3] found that for low-viscosity fluids such as water, the shell side convective heat transfer coefficient of the same flow unit pressure drop, the spiral baffle heat exchanger is about 2.4 times that of the ordinary arcuate baffle heat exchanger; For high-viscosity oils, the shell-side convective heat transfer coefficient per unit pressure drop at the same flow rate is about 1.5 times that of ordinary arcuate baffle heat exchangers. Research shows that spiral baffle heat exchangers are not only suitable for low-viscosity fluids, but also for high-viscosity fluids. In short, spiral baffle heat exchangers have the advantages of good heat transfer effect, small flow pressure drop, not easy to fouling, and small flow-induced vibration [4]. The spiral baffle heat exchanger used in this experiment is composed of several fan-shaped baffles with a quarter shell cross section that are propelled in a spiral shape from the inlet to the outlet. In this way, the medium flows continuously, steadily, and rotates in the entire shell, avoiding serious pressure losses caused by large-angle reentry and reducing energy consumption. At the same time, due to the spiral distribution of the baffles, the shell medium generates a vortex, from the center of the circle to the half There is a large velocity gradient in the radial direction. This gradient field effectively generates turbulence on the surface of the tube, thins the boundary layer, and improves the film heat transfer coefficient. This article uses a helix angle of 12° as an example to study the heat transfer and flow resistance performance of spiral baffle heat exchangers and arcuate baffle heat exchangers, providing reference for the industrial application of spiral baffle heat exchangers and their use in combination with other new enhanced heat transfer tubes. 2 Experimental device and process In order to study the heat transfer and flow resistance performance of the spiral baffle heat exchanger, the overall experimental device and process used in this article are shown in Figure 1. The experimental system consists of two parts. The first part is the hot diesel (hot water) circuit. The hot diesel (hot water) passes through the oil storage (water) tank (2, 3) centrifugal pump (8) rotor flow meter (6) and then enters the heat exchanger (1). After cooling, it returns to the oil storage (water) tank; the second part is the cold The cooling water supply system consists of a water storage tank (4) and a water pump, which regulates the flow of cooling water through a valve (5). Temperature measurement points are set at the inlet and outlet of the diesel and cooling water, copper-constantan thermocouples are installed, and the inlet and outlet temperatures are measured with microvolt-level electronic millivolt meters; the flow rates of diesel and cooling water are measured using rotameters respectively; according to the readings of the pressure gauge (7), the total pressure drop of the working fluid flowing in the shell side of the heat exchanger can be obtained. The heat exchanger is a single-shell side, double-tube side, and the spiral baffle is a single-head spiral. Its structural diagram is shown in Figure 2. 3 Data processing method Change the flow rate of diesel (hot water) working fluid, record the inlet and outlet temperatures and flow rates of diesel (hot water) and cooling water under different flow rates, and the readings of the inlet and outlet pressure gauges on the shell side of the heat exchanger. 3.1 The modified Wilson method for calculating the shell-side heat transfer film coefficient requires few known conditions or limiting conditions, and is more suitable for heat transfer test data processing of shell-and-tube heat exchangers [5]. In this paper, after obtaining the total heat transfer coefficient of the heat exchanger, the modified Wilson separation method is used to calculate the heat transfer film coefficient inside and outside the heat exchanger. If the difference between the heat absorption and heat release at thermal equilibrium is within ±10%, the experimental data is considered reliable and used. 3.2 Calculate the resistance of the fluid flow on the shell side and analyze the flow path of the fluid on the shell side of the spiral baffle heat exchanger. It can be obtained that eta = 1 is taken as the initial value and the flow rate is the full flow. From formula (1). Formula (2) has Δp0 = (L/B) Dρu2m/2 (6) According to the D value at full flow rate, substitute the D value into equation (5) to get a new η′ value, compare η′ with η, if the relative error is less than the given accuracy, then the η value is considered to be the desired one, otherwise in the formula A --- the total flow area of the tube, m2; the upper subscript - the new value after iteration, the lower subscript - outside the pipe. Substitute u′m and the corresponding Δp0 value into equation (6) again, and iterate repeatedly until an eta value that meets the accuracy requirements is obtained. The final resistance coefficient can be calculated from equation (3). 4 Experimental results and analysis. Under the test conditions of 4m3/h≤W0≤19m3/h, the change curves of the shell-side heat transfer film coefficient with the flow rate (W0) of the two heat exchangers and the change curves of the resistance coefficient of the shell-side fluid flow with the flow rate (W0) are shown in Figure 3, Figure 4, Figure 5, and Figure 6 respectively. It can be seen from Figures 4 and 5 that as the flow rate increases, due to the increased turbulence, the shell-side heat transfer film coefficient of the heat exchanger increases; under the same flow rate, the shell-side heat transfer film coefficient of the spiral baffle is 33%-136% higher than that of the arcuate baffle, and as W0 increases, the heat transfer film coefficient increases to a greater extent than the heat exchanger. This is due to the spiral baffle shell Due to the special structure of the process, when diesel (water) flows in the spiral channel on the shell side, the shearing motion of the diesel (water) and the tube wall can cause the boundary layer to continuously separate and thin the boundary layer, thereby reducing the thermal resistance of heat transfer and achieving the effect of enhanced heat transfer; the larger the flow rate, the better the enhanced heat transfer effect, so the spiral baffle heat exchanger can better exert its advantages of enhanced heat transfer under larger flow rates. It can be seen from Figures 3 and 6 that as the flow rate increases, the resistance coefficient of diesel (water) in the spiral baffle heat exchanger and the arcuate baffle heat exchanger decreases. At the same flow rate, because the fluid forms a jet (ie Plug flow) in the spiral channel of the spiral baffle heat exchanger, the resistance coefficient of diesel (water) in the spiral baffle heat exchanger is 15%-35% lower than that in the arcuate baffle heat exchanger.5 Conclusion Using diesel (water) as the working fluid and the flow rate in the range of 4m3/h≤W0≤19m3/h, the shell-side heat transfer film coefficient of the spiral baffle heat exchanger is 33%-136% higher than that of the arcuate baffle heat exchanger. As the flow rate increases, the improvement is greater, and it has It has a better enhanced heat transfer effect; the resistance coefficient of the shell side fluid flow is 15%-35% lower than that of the bow-shaped baffle heat exchanger within the range of test conditions. The spiral baffle heat exchanger has excellent heat transfer and flow resistance performance, and has broad prospects for application in petroleum, chemical and other fields. References [1] Zhao Xiaoxi, Deng Xianhe, Lu Enxi. Heat transfer and flow resistance performance of spiral baffled rhombus fin tube heat exchanger [J]. Acta Chemical Engineering, 2003, 54(3): 388-391 [2] StehlikP, NemcanskyJ, KralD, SwansonL.W. Com paresionofCorrectionFactorsofShell -and-TubeHeatExchangeswithSegmentalorH elicalBaffles〔J〕.HeatTransferEngineeri ng,1994,15(1):55-65 [3] Chen Shixing, Zhang Kezheng, Zhang Qiang. Experimental research on spiral baffle heat exchanger (Ⅰ, Ⅱ) [J]. Journal of Fushun Petroleum Institute, 1998, 18(3): 31-38 [4] Wang Suhua, Wang Shuli, Zhao Zhiyong. Research on flow characteristics of spiral baffles [J]. Journal of Petroleum and Chemical Engineering Colleges, 2001, 14(1): 64-67 [5] Ouyang Xinping, Huang Haiying, Tao Leren. Application of Wilson method in shell and tube heat exchanger testing [J]. Industrial Boiler, 1999, 1:24-26