Research On Grain Drying Characteristics Based On Test Rig With Controllable Temperature And Humidity

The factor relative humidity of drying medium is often ignored in traditional hot air drying research.However,the relative humidity of drying medium play an important role in grain drying process.According to the hot air drying technology which is available,simulated the environment of hot air drying process in real producing,design one new experiment scheme with adding drying medium relative humidity,and do research about the results of hot air drying process how influenced by drying medium relative humidity.This paper aims to that study the drying experiment of cross flow hot air thin layer under constant temperature and humidity conditions,design a new type of cross flow hot air thin-layer drying test rig,and study on the factors five that hot air temperature,hot air drying relative humidity,hot air drying velocity,initial moisture content of wheat and the radio of tempering which affect the drying rate and the drying time of thin-layer drying experiment process.By five quadratic regression orthogonal rotation combination experiment,the cross-flow thin layer drying characteristics of wheat under constant temperature and humidity conditions were studied,and a relatively accurate drying model was required which was fitted to describe the drying process of wheat under constant temperature and humidity conditions and drying laws.This paper mainly study about:1)Design a new type of cross-flow hot air thin layer drying test rig,mainly by: axial fans,heating resistance wire,humidification devices,sensors,control devices and other components.The test rig is powered by an axial flow fan to circulate air inside the test rig to ensure that the humidity and temperature inside the test rig are generally consistent in all parts.The control device ensures that the resistance wire can maintain during heating Hot air temperature within a small range of 1℃ floating,humidity within 1% per minute floating within the scope of change.In the drying process,the hot air flow to the axial fan as the driving force,starting from the location of the heating resistor wire,flow in the inner drying oven,through the drying zone,after the axial fan,into the outer box humidification,back To the heating resistance wire position,the formation of air circulation.2)Secondly,this article do an experiment about cross-flow hot-air drying of wheat.Designing the five-element quadratic regression orthogonal rotation combination experiment,study that the effects of hot air temperature,hot air humidity,initial wheat moisture content,with the total drying time and drying rate to be the experimental indicators for regression analysis.The results showed that hot air temperature,as the most significant factor affecting the drying characteristics,had a positive correlation with the drying rate and had no significant difference with the total drying time The relative humidity of the hot air has an important influence on the drying experiment of the thin layer.The higher the hot air humidity,the lower the drying rate and the longer the drying time.The higher the hot air velocity,the faster the drying rate and the longer the drying time.The higher moisture content,in most cases,is positively correlated with the drying rate and negatively with the drying time.Among them,since the free water is more in the initial stage of wheat,the drying rate is higher at this stage,affecting the overall drying rate;the ratio of the tempering is not significantly affected by the drying rate.Under the condition of the initial moisture content of wheat is 21% and the drying rate is less than 0.8% per hour,the optimal solution is hot air temperature 43.2,hot air humidity 50%,hot air speed 0.63 m / s,The shortest total time is 6.935 h.3)Finally,the drying mathematical model of drying thin-layer wheat by cross-flow hot air was studied in this paper.The experimental data were analyzed by Desgin-Expert.The results showed that the Page equation MR = exp(-ktN)The drying experiment results in a dry model in which the coefficients k and N are affected by the combined effect of the hot air temperature,the hot air humidity,the hot air velocity,the initial moisture content of the wheat,and the ratio of tempering.R2 values were 0.9548 and 0.9618,respectively,and the model was significantly affected.