Temperature And Flow Fields Simulation And Experimental Research On Multi-Temperature Zone Mesh Belt Dryers

In view of the problems of uneven drying and unsatisfactory drying effect in the drying process of Camellia oleifera seeds drying equipment in China at this stage.A belt dryer of multi-temperature zone is designed to meet the requirements of continuous drying and temperature zoning.In this paper,the flow field and temperature field of Camellia oleifera seeds dryer was numerically simulated by computational fluid dynamics(CFD)method.The main contents and conclusions of this article are as follows:(1)Four kinds of multi-temperature belt dryers with different structures were designed.The layer of Camellia oleifera seeds was simplified as a porous medium model,and the energy source term was used to represent the heat that camellia seed would absorb in the air during the drying process.The numerical value of the energy source term corresponded to the internal heat source in the energy equation,and the parameters of the energy source term were calculated.The energy source terms of each layer from top to bottom are-62936.7966W · m-3,-30899.9447W·m-3,-15871.4280W·m-3 and-5342.4484W·m-3 under the condition of layer by layer decreasing.The energy source terms of each layer from top to bottom are-46096.0338W·m-3,-30191.7296W.m-3,-20769.6181W·m-3 and-11861.5568W·m-3 under the condition of layer by layer increasing.The boundary conditions of numerical simulation were determined,which laid the foundation for the numerical simulation,design and selection of working parameters of multi-temperature zone mesh belt dryer.(2)The velocity field and temperature field of four different structures of multi-temperature zone belt dryer were simulated by computational fluid dynamics method.The results showed that when the flow equalizing room was set up,the flow of each layer plays a guiding role,the hot air can directly reach the Camellia oleifera seeds layer,and the interference effect on other layers is small,and the temperature stratification effect can be realized.At the same time,the temperature stratification effect and temperature uniformity are the best under the straight air supply structure.The average temperatures of each layer from top to bottom layers are 61.24℃,57.71℃,53.67℃ and 49.53℃ under the decreasing profiles,and the temperature nonuniformity coefficients of each layer from top to bottom layers are 2.91%,2.25%,1.24%and 0.63%.The average temperatures of each layer from top to bottom layers are 48.88℃,53.65℃,58.20℃ and 62.74℃ under the decreasing profiles,and the temperature nonuniformity coefficients of each layer from top to bottom layers are 3.22%,2.42%,2.08%and 1.74%.Therefore,the multi-temperature zone mesh belt dryer with the flow equalizing room and straight face air supply structure is beneficial to the drying of Camellia oleifera seeds.(3)The multi-temperature zone mesh belt dryer with the flow equalizing room and straight face air supply structure was tested and verified.The single layer temperature uniformity and the overall stratification effect were analyzed to verify the accuracy of the numerical simulation results,and the drying performance of the multi-temperature zone mesh belt dryer was evaluated.The results showed that the multi-layer mesh belt dryer could achieve accurate and independent control of each layer temperature according to the drying process requirements,which could meet the requirements of continuous drying of Camellia oleifera seeds and adapt to the variable temperature drying process of Camellia oleifera seeds.The variation trend of test results is consistent with that of numerical simulation results,which verifies the accuracy of numerical simulation results.In the experiment,the first,second and third layers of the dryer in the multi-temperature zone can reach the predetermined temperature.As the outlet is in the fourth layer,the air leakage phenomenon is serious,which makes it difficult to increase the air supply temperature and the temperature of the fourth layer.When the Camellia oleifera seeds are dried continuously according to the temperature change curve,the precipitation amplitude was 44.83%.The drying rate was 4.08%/h.In summary,the multi-temperature zone mesh belt dryer developed in this paper can meet the requirements of continuous drying of Camellia oleifera seeds,adapt to the variable temperature drying process of Camellia oleifera seeds,and the temperature uniformity and temperature stratification effect are the best under the condition of setting the flow equalizing room and straight face air supply structure.The research results can provide a reference for the partition controllable variable temperature drying of the mesh belt dryer.