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Infrared blanching is a new pretreatment method for fruits and vegetables apple slices drying. However, the influence of the air medium properties on the infrared blanching is not clear, which is not conducive to developing the infrared blanching technology. In order to reveal the mechanism of the heat and mass transfer of infrared blanching pretreatment of apple slices and that effects on the drying process, the air medium humidity control technology was used in infrared blanching of apple slices in this paper. Numerical simulation was used to analyze the law of heat and mass transfer during infrared blanching of apple slices under different air relative humidity. The convection heat and mass transfer between air and material was obtained by Newton’s law of cooling, and the radiation heat transfer between infrared radiation source and material was solved by Stefan-Boltzmann’s law. According to Fick’s diffusion law and Fourier’s heat conduction law, the moisture diffusion and heat transfer in apple slice were calculated. The effect of infrared blanching under medium humidity control on drying efficiency and the color of products were studied by combining blanching and drying experiments. The results showed that the heat and mass transfer of infrared blanching for apple slices could be described by the mathematical model, which based on the heat transfer of infrared radiation and air convection, and considering moisture evaporation and vapor condensation. The model fitted well with the apple slice moisture and temperature data with average relative errors of 0.54% and 0.39%, respectively. The heat and mass transfer during infrared blanching involved the interaction of infrared radiation source, air medium and apple slice. At constant 120℃ of infrared heating temperature, the relative humidity of medium had effect on the heat and mass transfer during infrared blanching, drying rate after blanching, and product quality. Under the condition of low humidity (1% relative humidity), the water vapor partial pressure of the air medium was lower than that of the material surface. The moisture in material was transferred from the surface of the material to the air medium via diffusion, and the heat consumption of water evaporation accounted for 40% of the total absorbed heat of material, resulted in slow heating rate of material. At the constant temperature, the higher relative humidity, the more water vapor content in the equal amount of dry air. Increasing the relative humidity of the medium to 50% could effectively restrain the water evaporation of the apple slice that could greatly improve the heating rate of material at the initial stage of blanching. In 50% relative humidity, The center temperature of the material increased to 86.8℃ after blanching for 120 s. The drying rate and color quality of the apple chips could be improved by infrared blanching under high air relative humidity. Compared with 1% relative humidity, the pre-drying time of the apple slice was shortened by 8.3% under 50%IRB, and color difference and browning index of apple slice were reduced by 55.6% and 37.4%, respectively. The results provided a new idea for the development of infrared blanching pretreatment technology of fruits and vegetables to achieve high quality and efficient drying. [ABSTRACT FROM AUTHOR]

Based on the principle of one dimensional flow and heat transfer, the law of temperature attenuation along the path was acquired by solving the one-dimensional coupled heat conduction and convection equation with harmonic method. Then the law of rheological resistance increasing along the path was obtained. Meanwhile, the law of pressure attenuation along the path was solved. Finally, the prediction model of rheological filling ability for aluminum alloy in molten metal die forging was established by combining the stopping rheological mechanism and conditions of alloy melt. Furthermore, the model covered t he process parameters of molten metal die forging, material property parameters and mold structure structure parameters, and it was suitable for generalized semi-solid ally melt below liquidus temperature. The validity of theoretical model was verified by the length of Archimedes spiral sample of 6066 aluminium alloy by molten metal die forging. The resutls showed that the maximun relative deviation between the calculated results and the experimental results was only 8.2%. Compared with the exisying fillinf ability model, the rheological filling distance model in this paper has some progress in the prediciton accuracy and application scope. [ABSTRACT FROM AUTHOR]

In order to study the effect of the nozzle structure of the spray box on the convective heat transfer between the hot air and the veneer in the air-jet veneer dryer, the impact heat transfer characteristics of the air flow from the circular spray hole and round flanging spray hole on the veneer surface were studied by Fluent software. The effects of jet spray distance H, nozzle outlet diameter d, jet velocity v, jet temperature T on the convective heat transfer of the round flanging spray hole were systematically analyzed. The results showed that the round flanging spray hole can improve the convective heat transfer uniformity between the jet and the plate and improve the heat transfer efficiency. The heat transfer capacity between hot air flow and veneer had a positive correlation with jet velocity and jet temperature respectively. There was no single linear relationship between the jet spray distance, the nozzle outlet diameter and the convective heat transfer coefficient, and there was a spray distance range, so that the convective heat transfer intensity and convective heat transfer uniformity between the jet and the single plate were optimized. This paper provided a theoretical basis for the design of veneer dryer spray box. [ABSTRACT FROM AUTHOR]