The Influencing Factors Of Cowpea Quality Dried In Tunnel Kiln And Relative Analysis

Cowpea is one of the green vegetables, rich in protein, carbohydrates, vitamins and mineral elements. It has been planted all over our country. With high nutritional value, cowpea is beneficial to digestion and gastric absorption. In addition, it also can be effective in preventing cardiovascular diseases. Cause of high moisture content, fresh cowpea is not conducive to preservation after harvest. For long term storage, it’s usually recommended to reduce the moisture content to the safe level by drying. In this way, it helps to regulate the supply of vegetables during the off-season, bringing economic and social benefits.Tunnel drier which is widely used in the field of fruit and vegetable drying has many advantages such as simple structure and low investment. In the processing of cowpea using this kind of equipment, it not only improves the handing capacity per unit time but also obtains good quality products.According to actual production, there’s a big difference among the dried cowpea products processed in the tunnel kiln. Vc content and rehydration rate of the products are low, otherwise the moisture distribution among the products is inconsistent either. Based on this case, we explored the drying characteristics of cowpea and the flow distribution inner the tunnel kiln, to improve the quality of the dried products. The results provide a theoretical basis for the optimization of cowpea processing and structure of tunnel kiln.It’s proved that the constant drying period and the falling rate drying stage accounted for the most time of cowpea dewatering process according to the hot air drying experiments. The thickness of material layer gives most negative impact on the drying rate, followed by hot air temperature. The primary influencing factor to product quality is temperature, and the secondary is thickness of the material layer.Conclusions of numerical simulation show that the wind flow mainly distributed in the central and lower part of tunnel kiln in the height direction. The flow distribution inner the tunnel kiln has a great impact on the quality of dried products. Numerical simulation results show that it is not conducive to dry cowpea because of low wind speed in the upper part of tunnel drying kiln. The layout of partition board and angle iron located at the entrance of tunnel kiln play a large role in regulating the distribution of air flow.