| Tobacco leaf curing needs a large amount of heat.Coal,which is used as a way of heating with high coal consumption and low heat utilization,is widely used to cure tobacco for a long time in China,one of the biggest tobacco producing countries.With the development of new energy and technology in heating and drying industry,tobacco curing process and equipment also get continuously improved and innovated.Heat pump technology has gradually be applied to tobacco curing because of the characteristics of energy saving,environmental protection and high thermal efficiency.In this paper,a kind of heat pump tobacco leaf bulk curing system with heat recovery unit was proposed and designed.Based on theoretical analysis,simulation and experiment,the paper lays emphasis on the study of the energy saving of the heat pump tobacco leaf bulk curing system with heat recovery unit.This paper firstly determined the system mode of the heat pump tobacco leaf bulk curing system with heat recovery unit,analyzed not only the composition of heat load but also heat and mass transfer process of the tobacco curing barn based on the principle of thermodynamics,and established a simplified energy model of the whole tobacco curing barn.Taken the curing of Yunyan 97 as an example,the heat load distribution of the tobacco bulk curing barn was studied with DeST software played as an assisting role in the paper.According to the results,the heat load distribution of the tobacco bulk curing barn is mainly affects by dehydration rate of tobacco leaf,which is similar to the humidity load distribution.The maximum heat load appears in the later stage of the color fixing period;the envelope load increased as temperature inside the barn increases,and the load accounts for 15% of the total heat load of the tobacco bulk curing barn during the curing process;nearly 90% of the curing time is under the load rate of 20%~60%.On the basis of the heat load calculation,TRNSYS software was used to establish the system model of the heat pump tobacco leaf curing system with heat recovery unit,and the system simulation was carried out.The simulation results show that COP of the system is 4.11,and the average specific moisture extraction rate(SMER)is 3.48 kg /(kW · h),while COP of conventional heat pump system tobacco bulk curing barn is between 1.92~3.25.Obviously,the drying efficiency of the heat pump tobacco leaf curing system with heat recovery unit is higher.The experimental equipment was set up in the tobacco curing base in a tobacco Agricultural Park in southern Anhui.An experimental tobacco bulk curing barn was transformed into the heat pump tobacco leaf curing system with heat recovery unit to carry out the test.The results show that average COP of the system is 3.85,the average specific moisture extraction rate(SMER)reaches 3.22 kg /(kW · h),and the drying efficiency is far superior to the traditional coal-fired bulk curing tobacco barn.The measured results and the simulation results are consistent,which indicates reliability of simulation results and verifies energy saving effect of the heat pump tobacco leaf curing system with heat recovery unit.In the end,this paper compared the experimental barn with manual coal feeding barn and automatic coal feeding barn,the two traditional bulk curing barn,from following three aspects: operation cost,quality evaluation of tobacco leaf and environmental benefit.Results show that the use of the heat pump tobacco leaf curing system with heat recovery unit owns the ability of cutting down operating cost of the system,improving quality of tobacco leaves,reducing labor intensity,building up production efficiency and decreasing output of various pollutants emission,which demonstrates remarkable application benefit. |
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