| With the development of society,the energy problem is becoming more and more serious.The traditional fossil energy is drying up.Energy conservation and emission reduction and new energy development are always hot topics in the energy field.As an important equipment for waste heat recovery and heat transfer in energy field,the efficiency of heat exchanger will directly affect the utilization of energy,and the high efficiency heat exchanger will save more energy.The reliability of heat exchanger affects the whole production process.Fluid induced vibration is one of the main reasons leading to failure of shell and tube heat exchangers.A variety of anti vibration measures have been put forward by the researchers for a long time.On the basis of previous studies,a new style heat exchanger called the blade baffle heat exchanger is proposed to prevent fluid induced vibration in this paper.The performance of the blade baffle heat exchanger and the spiral baffle heat exchanger was compared by numerical simulation,and the influence of different structural parameters on the performance of this type of heat exchanger was also studied.Based on the research results,the shell side tube layout was optimized.Finally,the dynamic characteristic of heat exchange tubes in the blade baffle heat exchangers was analyzed by seam-connection method.The conclusions are summarized as follows.(1)In order to suppress the flow induced vibration,a new type shell-and-tube heat exchanger with balde baffle was proposed in this paper,and its performance was compared with the helical baffle heat exchanger.When the Reynolds number is at2500~7500,the heat transfer coefficient of the blade baffle heat exchanger is increased by 3.19%~48.48% than that of the helical baffle plate heat exchanger.The pressure drop of the shell side of the helical baffle heat exchanger is reduced by45.19%~47.06% compared with the blade baffle heat exchanger.When the Reynolds number is greater than 6500,the comprehensive performance of the fan blade baffle heat exchanger is higher than that of the helical baffle heat exchanger.The flow state of the two heat exchangers is similar.The flow velocity in the central area is lower than area near the shell wall,and the velocity difference in the blade baffle heatexchanger is larger.The shell-side fluid in the blade baffle heat exchanger enters the fully developed state earlier than the fluid in the helical baffle heat exchanger,resulting in high heat exchange performance of the blade baffle heat exchanger.The synergy angle of the blade baffle heat exchanger is smaller than that of the helical baffle heat exchanger,so the former has better convective heat transfer characteristics.(2)The influence of baffle installation angle,tube arrangement,baffle arrangement and baffle pitch on the performance of the blade baffle heat exchanger was studied.The results are as follows: when the installation angle is 60°,the pressure drop of the shell side is the lowest,which is reduced by 89.3%~91.7%,68.3%~78.1%compared with the installation angle of 30° and 45°;the heat transfer coefficient of the shell side of the heat exchanger with a installion angle of 30° is higher than that of the other two,which is increased by 9.4%~19.3%,26.6%~31.7% compared with the installation angle of 45° and 60° respectively;when the installation angle is 60°,the comprehensive performance of the blade baffle heat exchanger is higher than that of the other two;the arrangement of heat exchanger tubes can obviously affect the performance of the blade baffle heat exchangers,and the reasonable arrangement of tube bundles can effectively improve the performance of the heat exchangers;when the outer tube arranged densely,the heat transfer performance of the blade baffle heat exchanger is improved than that normal layout,but it also increases the pressure drop of shell side and reduces the comprehensive performance;the parallel-arranged balde baffle heat exchanger has the highest comprehensive performance;the axial rotating angle of the baffle could reduce the pressure drop and the heat transfer coefficient slightly;the staggered arranged baffles could aggravate the shell side flow disturbance and enhances the heat transfer coefficient;with the increase of baffle pitch,the heat transfer performance of the blade baffle heat exchanger decreases,pressure drop decreases,and comprehensive performance decreases;when the baffle pitch is 200 mm and 250 mm,the low velocity region appears in the central region,the low velocity region expands with the increase of the Reynolds number and the baffle pitch.(3)The tube layout of the blade baffle heat exchanger was optimized,and theperformance changes of the heat exchanger before and after optimization were compared.The results are as follows:(4)The dynamic characteristics of the heat exchanger tubes in the balde baffle heat exchanger were analyzed by means of the seam-connection method.The results are as follows: the fundamental frequency of the tube in the shutter baffle heat exchanger is very close to that in the segmental baffle heat exchanger,and the difference between them decreases with the decrease of Link 10 pitch;when the Link10 pitch is less than 0.1m,the two frequencies are almost equal,at this condition,the constraints of shutter baffles on tubes can be simplified as simply supported constraints;when the The tube span is 1.0 m and the Link 10 pitch is 0.2 m,the fundamental frequency of the tube in the shutter baffle heat exchanger is infinitely close to that in the segmental baffle heat exchanger.And when the tube length is larger than 7.0 m,the two frequencies are almost equal,at this condition,the constraints of shutter baffles on tubes can be simplified as simply supported constraints.The fluid induced vibration should be judged on the basis of the fundamental frequencies of the outer tubes. |
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