Research On Characteristics Of Round Bamboo Microwave-Vacuum Drying

As a new type of drying technology.Microwave-vacuum drying has been widely used in other fields,such as food stuffs.The cylindrical structure of round bamboo has both excellent mechanical properties and aesthetic characteristics.Its application in various fields such as furniture and architecture has important practical significance.In this paper,round bamboo was taken as the research and the microwave-vacuum drying characteristics of round bamboo were preliminary studied.The general rules of drying were summarized in the studying.The color,shrinkage and cracking were expounded.The mathematical model of moisture content was established.The research will provide a theory basis for the further application of microwave-vacuum drying technology of round bamboo.The main conclusions of this study are as follows:(1)Developed a round bamboo microwave-vacuum drier and which could weigh the samples online.The device achieve monitoring of moisture content of the samples requirement.(2)The discipline of microwave-vacuum drying of round bamboo was systematically studied.The results showed that: With the increase of microwave power?drying temperature and vacuum levels.The drying rate of round bamboo increased.The drying rate was higher when the initial moisture content was higher;The movement rates of water were obvious under different texture directions.The relationship is: unsealed samples>longitudinal>bamboo yellow>bamboo green>diaphragm;Analysis of variance showed that microwave power,drying temperature and vacuum levels and initial moisture content have significant effect on the drying rate;Microwave-vacuum drying of round bamboo has higher drying efficiency and better drying effect than traditional drying method.(3)The influence of drying conditions on the change of bamboo color was systematically studied.The results showed that: After drying,the color changed from green to yellow and distribution was more uniform.With the microwave power increasing,the value of L*a*b* increased;The higher drying temperature increased,the more obvious change of color was.The range of lightness L* was from 46.35 to 56.02.And the index a* was from-2.45 to 4.57 from green to red.The index b* was from 25.83 to 29.28.which was from blue zone to yellow zone;The higher the degree of vacuum,the more change of color was.The range of lightness L* was from 46.35 to 54.34.The index a* was from-2.45 to 5.73 and moved from green to red.The index b* was from 25.83 to 27.84.It was from blue zone to yellow zone.The overall color ?E* gradually increased with the drying conditions enhanced.It indicated that the color difference increased.(4)The effects of drying conditions on the shrinkage were studied systematically.The results showed that the shrinkage was increased with the microwave power,drying temperature and vacuum levels improved.The shrinkage rate of the upper part was higher than that of the bottom part.Analysis of variance showed that power,temperature and vacuum levels had a significant effect on the shrinkage.(5)Microwave-vacuum drying could avoid the cracking in a large extent.It could reach a lower moisture content in a short time.In this studying,the type of cracking was mainly end cracking,mid-cracking and penetration cracking.It mainly occurred in the severe drying condition.(6)Taking Hong bamboo as the object,the method of physical and X-ray tomography was used to establish the fitting model of moisture content-CT value: CTM+×=96.832148.0 ?.The reliability and accuracy of the model were verified by experiments.It was used to measure the distribution and migration of radial and axial moisture content of bamboo in different drying stages.(7)Through comparative study with common drying methods,the advantages of microwave-vacuum drying are illustrated.Which was an effective ways for industrial drying of round bamboo.