A case study: Monitoring heat exchanger based on vibration sensors and nondestructive testing technique
Flow-induced tube vibration could cause serious damage on large-scale circulating-water heat exchanger in factories, e.g., atomic reactors, nuclear power plants, petroleum and chemical industry. Therefore, efficient inspection technology is very important for heat exchanger's blockage and leakage. The existing detection technologies, like temperature test and pressure test, are very easily affected by extraneous factors, e.g., temperature and pressure, while the nondestructive testing technology based on vibration sensors is free from above limits. In this paper, we use vibration sensors to detect blockage and leakage of the circulating-water heat exchanger. According to the experimental results, it is found that when detecting heat exchanger's blockage and leakage with vibration sensors, environmental vibration from the working machines has influence upon the result, while pump vibration and vibration produced by liquid flowing through regulating-valve make little difference. Nevertheless, fault diagnosis of large-scale circulating-water heat exchanger, which uses nondestructive testing technology based on vibration sensors, needs to be further improved.
Research and Industry Application of Helical Baffled Heat Exchangers
The helical baffled heat exchanger mainly includes two kinds of different geometry designs.The first is that helical baffles are not integrally continuous and a central tube is not placed in the exchanger.The second is that helical baffles are integrally continuous and a central tube is placed in the exchanger.The research works concerning hydrodynamic studies,and heat transfer and pressure drop testes and numerical simulations in the shell side of helical baffled heat exchangers are reviewed.The application of the helical baffled heat exchangers combined with different enhanced tubes are presented.Eventually,the expected aspects of further investigations on helical baffled heat exchangers are put forward.
Buffeting Excitation of Boiler Tube Vibration
The origin of the vibration generated within an extensive bank of tubes that run transverse to the direction of gas flow through a boiler shell and whose movement is small enough in amplitude to have no perceptible effect on the motion of the gas, is examined on the supposition that, sufficiently deep inside the bank, the flow is essentially turbulent and, except for a general drift through the bank, exhibits no regular feature. Conditions of this kind are thought to be appropriate to certain types of heat exchanger used in nuclear power stations and operating at large Reynolds numbers.The source of vibration, either structural or gaseous, is associated with the randomly fluctuating forces imposed on the tubes by the turbulent eddies, and a simple argument is put forward to account approximately for the length scale of the most energetic of these eddies and consequently the frequency with which they encounter the tubes. It is further argued that the tubes are aerodynamically discriminating in their force ...