Film Thickness Measurements Of The R1233zd Film Evaporation And Flow Processes

The evaporation and flow of refrigerant films widely exists in aviation and aerospace,refrigeration and air conditioning,consumer electronics,and other fields.Film thickness is closely related to heat transfer in the film evaporation and flow processes.Quantitative analysis of film thickness is helpful to understand relevant heat transfer mechanisms and provide scientific guidance for optimizing relevant industrial devices and processes.Researchers at home and abroad had done a lot of research on refrigerant films based on numerical simulation.However,in order to verify and optimize the simulation model,high accuracy measurement technology was needed to provide experimental data.Although many scholars had carried out a lot of experimental research on conventional liquid film thickness measurement based on electrical method,acoustic method and optical method,compared with liquid media such as water,oil and solution,the boiling point of refrigerant is low,and the experimental environment and working conditions of liquid film evaporation and flow process are difficult to control.Therefore,the research on the measurement methods of refrigerant liquid film was relatively scarce,and there were some limitations.R1233zd is a new nonflammable refrigerant with zero Ozone Depletion Potential,low Global Warming Potential and good environmental protection performance.In this work,R1233zd is taken as the research object,and a novel method of refrigerant film thickness measurement by absorption spectroscopy is proposed.The main research contents are as follows:1.A high accuracy（±0.1°C）refrigerant temperature control device was designed and developed to realize the temperature control of R1233zd in the cuvette.The absorption spectra of R1233zd were measured by Fourier transform infrared spectrometer at different temperatures（11.8/12.6/13.5/14.3/15.2/16.0/16.5/17.1/17.7/18.0°C）,and the absorption spectral characteristics of R1233zd in near-infrared region were deeply analyzed.On this basis,the wavelength optimization criterion for refrigerant film thickness inversion was proposed,and the two wave number positions were preliminarily determined as 6080.5 cm^-1 and 6280.5 cm^-1,respectively.2.A refrigerant film thickness measurement system on the transparent quartz plate surface based on absorption spectroscopy was developed.Due to the limitation of the resolution(5.2 cm^-1)of the near-infrared spectrometer in the system,the two wave number positions were finally determined as 6082.9 cm^-1 and 6278.1 cm^-1.Combined with the self-made data acquisition and processing program,the measurement accuracy of the liquid film thickness of the system was verified by using the calibration tool with adjustable film thickness（100/200/300/400/500μm）at a certain temperature（13.5°C）and the cuvette with a certain thickness（1000μm）at different temperatures（13.5/14.5/15.5/16.5/17.5°C）.It revealed that the average relative deviations between the measured and the known values were 0.3%and 0.4%,respectively3.Combined with an imaging method,the evaporation processes of three groups of R1233zd films with different initial thicknesses on horizontal quartz plate were investigated.It revealed that the initial film thicknesses of the three groups measured by absorption spectroscopy and imaging method were 399.6/410.7/423.6μm and401.0/409.7/422.6μm,respectively.The relative deviations of film thicknesses were0.35%/0.24%/0.24%,respectively.And the changes of film thicknesses measured by the two methods matched quite well during the whole evaporation processes,and the average relative deviations were 1.0%/1.4%/1.6%,respectively.4.The system was used to investigate the flow processes of R1233zd films on an inclined quartz plate surface at different flow rates（65.0/79.0/97.0 m L/min）.It revealed that 4-22 s after the start of data acquisition,the average film thicknesses at the three flow rates were 207.8/212.3/223.2μm,respectively.And the corresponding standard deviations were 14.5/12.9/11.5μm,respectively.5.The flow processes of R1233zd films at different flow rates（65.0/79.0/91.0/97.0m L/min）in an inclined quartz circular tube were further studied.It revealed that the average film thicknesses at the four flow rates were244.4/248.4/259.5/263.6μm,respectively.The corresponding standard deviations were12.3/9.8/8.2/7.7μm,respectively.