System for measuring wave frequency and wave speed of fluctuating liquid membrane in pipe

Abstract

A measuring system provided by the invention transforms the light intensity into a current signal by using a photoelectric sensor, thereby realizing measurement of a wave frequency and a wave speed of a fluctuating liquid membrane. According to the principle of the system, when light emitted by an infrared light-emitting diode passes through a fluctuating liquid membrane interface, color dispersion is carried out and only the part of light is absorbed by an infrared photodiode. One pair of infrared light-emitting diode and infrared photodiode installed on the outer wall of a tested segment pipe form an upper stream sensor and a lower stream sensor; the sensors transform light intensity signals into current signals; after amplification by an amplifier, an A/D converter converts the amplified signals into discrete digital signals; and on the basis of FFT and a cross-correlation analysis principle, the digital signals are processed by using an MATLAB software programming program to obtain a wave frequency and a wave seed of a fluctuating liquid membrane. The system has the following beneficial effects: the wave frequency and the wave seed of the fluctuating liquid membrane are measured simultaneously; and the statistic uncertainty of measurement data is not lower than 5%.

Description

technical field [0001] The invention belongs to the technical field of measuring fluctuation characteristic parameters of a fluctuating liquid film in a falling film evaporator, and in particular relates to a method of obtaining a fluctuating liquid film in a tube through fast Fourier transform (FFT) and cross-correlation analysis of a current signal received by a photoelectric sensor A system of wave frequency and wave velocity. Background technique [0002] As an efficient heat transfer technology, steam condensation is widely used in petroleum, chemical industry, refrigeration, energy, aerospace and seawater desalination and other fields. The fluctuating characteristics of the condensate film in the actual application process strengthen the heat and mass transfer process. Condensate film fluctuations contain complex dynamic characteristics in time and space. Due to the limitation of testing technology and test methods, it is impossible to accurately measure the wave freq...

AI Technical Summary

Problems solved by technology

This measurement technique has the following main problems: identifying the same wave depends on the subjective judgment of the measurer; adding a fluorescent factor to the liquid can easily change the physical properties of the liquid film; only the wave velocity of the liquid film can be measured but the wave frequency cannot be measured

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