| The tobacco industry has an important contribution to China's economy,but drying tobacco leaves not only consumes a lot of energy,but also causes environmental pollution.Studying the hot and humid environment in the flue-curing room can improve the quality of flue-cured tobacco leaves,and provide a reference for the optimization of flue-cured tobacco technology,heat source matching in the flue-curing room,and energy saving,so as to achieve the purpose of improving quality and efficiency.In this paper,K326 tobacco leaves are selected,and the dense curing room is taken as the research object.According to the"three-stage"dense drying room drying process,combined with the heat and mass transfer theory of porous media,the CFD numerical calculation method and the test method,the yellowing period of the tobacco drying cycle,The parameters such as hot and humid environment,wind speed and moisture content of tobacco dry basis in the curing period and dry gluten period were analyzed.At the same time,the heat loss of the maintenance structure of the grill and the internal dehumidification and external heating double circulation heat pump system performance coefficients are analyzed,and the simulation results are compared with the test results to verify.The main conclusions are as follows:The conditions of variable porosity and water migration equation were used to compare and analyze the consistency of the simulated value and the experimental value.The simulation results showed that the average pressure in the baking room during the yellowing period was about 46Pa,and the average wind speed in the upper part of the baking room was about 3m/s.The average wind speed in the lower part is about 1m/s,the average wind speed in the smoking area is about 0.2m/s,the average air moisture content is about 0.05kg/kg,the relative humidity is relatively saturated,and the maximum heat flux density of the envelope is 97 w/m2;The average pressure in the grill during the color period is about 98Pa,the average wind speed in the upper part of the grill is about 4.5m/s,the average wind speed in the lower part is about 2.5m/s,the average wind speed in the smoking area is about 0.4m/s,and the air moisture content is about 0.035 kg/kg,the average relative humidity is about 50%,the maximum heat flux of the envelope is 320 w/m2;the average pressure in the baking room during the dry gluten period is about 46Pa,the average wind speed in the upper part of the baking room is about 3m/s,and the average wind speed in the lower part is about 1m/s,the average wind speed in the smoking area is about 0.2m/s,the air moisture content is about 0.025 kg/kg,the average relative humidity is about17%,and the maximum heat flux density of the envelope is 510w/m2.The average heat dissipation through the door,roof and wall of the baking room is 220w,2630w,8910w during the drying cycle.The total heat dissipation is about 1835kw,which is equivalent to the heat of 227.8kg bituminous coal.The dry base moisture content shows a trend of slow,fast,and slow.The model fitting function results are:W=5.14-0.029t+2.91t~2.and the regression determination coefficient is 0.99.The test and calculation shows that the average dew point temperature is 33.6?,the average moisture content is 0.0332kg/kg,the quality of tobacco leaves is reduced from 44g to 9g,the water quality of tobacco leaves is reduced from 36g to 2g,and the moisture content of dry basis is from 5kg/kg dropped to 0.2kg/kg.The average quality of the absolutely dry tobacco leaf is 9.37g,the maximum water loss of the tobacco leaf is about 8g during the color fixing period,and the maximum drying rate is about 0.00002kg/(kg·s)during the yellowing period.The average heating capacity of the internal dehumidification and external heating systems are 15.49kw and 15.72kw,respectively,and the average compression work of the compressor is 3.49kw and 3.72kw,respectively.The average COP of the internal dehumidification system is 3.23,and the average COP of the external heating system is 3.35.Through economic analysis,it can be seen that the recovery cost takes about 5 years,and at the same time,it can save about 14025.6 yuan in the life of the equipment.The use of heat pumps for drying tobacco leaves has both economic and environmental benefits. |
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