Study On The Performance Of An Air-cooled Gravity Heat Pipe Dehumidification System In The Fully Closed Hot Air Circulating Bulk Curing Barn

The open-type dehumidification in the process of tobacco baking in dense barns used in the production of flue-cured tobacco has many shortcomings such as energy waste and poor quality of tobacco leaves.This study proposed and constructed a novel fully-closed hot air circulation bulk curing barn air-cooled gravity heat pipe dehumidification system which couples the social demand of energy saving and improving efficiency of bulk curing barn.Firstly,the main structural parameters for the fully-closed hot air circulation dense air-cooled gravity heat pipe heat exchanger of the barn dehumidification system are determined based on the operating conditions of intensive barn.The steady convection and heat transfer model for the gravity heat pipe exchanger is developed based on the commercial CFD software FLUENT to investigate the effects of different air velocity,the distance between pipe on the performance of heat transfer.Finally,the experimental validation of on-site tobacco dense baking is conducted to get that the applicability of closed hot air circulation dense barn air-cooled gravity heat pipe dehumidification system is determined.The main results are following:(1)The fundamental principles of air-cooled gravity heat pipe dehumidification system for fully-closed hot air circulation bulk curing barn.(2)The main structural parameters,structural model of the air-cooled gravity heat pipe heat exchanger and the geometric model of the fully-closed hot air circulation bulk curing barn air-cooled gravity heat pipe dehumidification system are optimized and obtained.(3)The effects of different inlet wind speeds and pipe spacing on the heat transfer performance are investigated.It is found that the heat transfer efficiency of the gravity heat pipe was a concave function of the wind speed.So do not blindly increase the import wind speed but select the optimum wind speed through optimization.when the inlet wind speed is fixed,the total heat exchange capacity of the air at the evaporator side increases with the decrease of the pipe spacing,but the operability and economy must be considered when choosing the actual pipe spacing.(4)According to experimental data of flue-cured tobacco and the collection and measurement of the drainage during the baking process,the distribution of temperature and humidity during the baking process of tobacco leaves in a fully closed hot air circulation bulk curing barn with an air-cooled gravity heat pipe dehumidification system was obtained.(5)Through on-site closed hot air circulation intensive experiments,the large row of wet fixing period of tobacco leaves was selected as the main influencing factor research stage,and the change law including the heat transfer efficiency of air-cooled gravity heat exchanger with change of inlet dry bulb temperature,the dehumidification efficiency of air-cooled gravity heat pipe dehumidifiers varies with the inlet dry bulb temperature,inlet relative humidity,inlet wind speed,and inlet air flow are all obtained.