| In order to reduce the energy consumption of tunnel dryer, and make it more widely used in drying industry and farming, the energy consumption related drying factors were deeply studied by using the tunnel dryer for Chinese medicine material, which was self-designed, and also by using the tunnel length as drying factor for the first time.Lack of homogeneity of the air velocity in the tunnel dryer often seems to be the main factor that leads to high energy consumption, poor drying efficiency and non-homogeneity of the products. So the air velocity distribution was studied firstly, and the air velocity distribution in the tunnel was clear: the central air velocity was small, the air velocity at tunnel border was a bit stronger; the hot air velocity was decreased when entered into the material plate; the air velocity inside the tunnel was disordered partially, but stable in general. At the same time, the relationship between tunnel length and air velocity was also studied, the regression equation of air velocity at the air outlet and the effect of tunnel length to air velocity were gained. The results show that the longer the tunnel, the greater the resistance to the air. Under the same air inlet condition, the longer the tunnel is, the smaller the air velocity at the center of the outlet is.Secondly, based on the phenomenon that the air temperature was obviously affected by air velocity which causes the set temperature is not equal to the real air temperature in the tunnel, the relationships among the set temperature of the temperature control panel, the real air temperature in the tunnel and air velocity were studied. The results showed that the stronger the air velocity, the stronger effect of air velocity to air temperature; the higher the setting temperature, the stronger effect of air velocity to air temperature. At the same time, the temperature control system was proofread. The regression equation of set temperature to real air temperature and air velocity was gained; the proof-curve of temperature was drawn. Using this equation or proof-curve, the air temperature can be adjusted accurately and conveniently, the precision of the machine was improved.At last, in order to reduce the energy consumption of tunnel dryer, get a effective studying method for energy saving of tunnel dryer, based on the single factor experiment, the quadratic general rotary unitized experiment with three factors was operated, using the green radish pieces as drying material, the air temperature, air velocity and tunnel length as drying factors, unit energy consumption and production efficiency as indexes. The theoretical models of unit energy consumption and production efficiency were gained. And through the method of weighted optimization, the best combination of drying factors using the tunnel dryer to dry green radish pieces was gained. The combination is: air temperature is 52.8℃, air velocity is 1.50 m/s, tunnel length is 4.93 m. The best unit energy consumption is 2.08 kWh/kg, production efficiency is 2.26kg/h. These values were verified through the verifier tests. The verified results showed that the average error of unit energy consumption was 0.32% while the average error of production efficiency is 0.17%; the verified values conformed to the optimizing value very well. Then through data reduction analysis, the affections of air temperature, air velocity and tunnel length to unit energy consumption and production efficiency were analyzed; the results showed that the higher the air temperature, the higher the production efficiency, also the higher the unit energy consumption; along with the increase of the air velocity, the unit energy consumption first increased and then decreased a little, but the production efficiency increased obviously; along with the increase of the tunnel length, the unit energy consumption first decreased sharply and then increased a little, the production efficiency increased.
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