Study On Performance Of Regenerative Heat Pump Drying System In Closed Hot Air Circulation Bulk Curing Barn

At present,China’s tobacco planting area and output rank first in the world.The curing effect of tobacco leaves is the key factor to determine the quality and economy of tobacco leaves.In today’s energy shortage and strict environmental protection requirements,heat pumps,as a kind of efficient and pollution-free clean energy,are widely used in various drying.The current heat pump baking intensive grill The dehumidification method is open dehumidification.After the dehumidification air passes through the evaporator,it is directly discharged to the outside.The waste heat loss is serious and the baking energy consumption is high.Closed heat pump baking effect is better,but because the temperature of circulating air into the heat pump condenser is too high,the refrigerant in the condenser can not be completely cooled as liquid,so that the thermal performance of air source heat pump is poor.In this context,in order to improve the high temperature performance of the air source heat pump drying system,increase the recovery capacity of waste heat and reduce the loss of beneficial substances in the baking process,this paper proposed to add a gravity heat pipe regenerator between the curing room and the heat pump system to assist the heat pump curing.Through theoretical analysis,numerical simulation and experimental research,the gravity heat pipe regenerator and flue-cured tobacco system are studied.The main research contents and results are as follows:(1)Based on the operating conditions and dehumidification load of three-stage flue-cured tobacco,a regenerative heat pump flue-cured tobacco system was proposed.The regenerator of the system is composed of high efficiency gravity heat pipe,and the regenerator is added between the baking room and the heat pump.(2)Solid Works software was used to build a three-dimensional model of the regenerator,which was imported into the simulation software Fluent.The flow flow of the regenerator and the heat transfer performance of the regenerator were explored with the simulation software Fluent.The influence of pipe spacing on heat transfer performance is optimized through simulation.The heat transfer effect is the best when the distance between the heat pipes on the windward side is 30mm.(3)According to the numerical simulation results,a regenerator was made,and a regenerative heat pump flue-cured tobacco experimental platform was built.The dehumidification performance and heat transfer performance of the regenerator were tested and analyzed by using three-stage intensive tobacco leaf baking process.The energy consumption and economy of the regenerative heat pump baking system were analyzed.(4)The regenerator can reduce the circulating air temperature from the baking room,which drops from 66℃to about 43℃in the late stage of the dry bar.The average sensible heat efficiency,latent heat efficiency and total heat efficiency of the regenerator in the baking process are 57.63%,14.13%and 28.37%respectively,and the dehumidification capacity of the system reaches the maximum of 22.28kg/h in the fixed color period.Through the study of the fixed color period,it is concluded that with the increase of relative humidity,the maximum dehumidification amount corresponds to the greater the wind speed.(5)The experimental study of the regenerative system shows that the average dehumidification energy consumption ratio SMER of the system is 3.27 kg?(k W·h),the average heating coefficient Co P_s of the system is 3.48,the average regenerative temperature of the condensate section of the regenerator is 8.69℃,and the cost of 1kg dried tobacco leaves is 1.68 yuan,1.89 yuan,and 2.45 yuan respectively.