Research On Curing Temperature And Humidity Responsiveness And Effect In Heat Pump Bulk Curing Barn

In this study,“CF965” is used as the material to systematically study the temperature and humidity changes and the responsiveness of the heat pump and coal-fired bulk curing barn during the tobacco leaf baking process.The temperature and humidity are reflected by the dry bulb temperature and the wet bulb temperature.The chemical composition,sensory evaluation,economic benefits,and energy consumption and employment of the baked tobacco leaves in two types of curing barn are compared and analyzed.In addition,the numerical simulation study is carried out on the speed field and temperature field of the heat pump bulk curing barn.The purpose of this paper is to provide theoretical basis for the optimization and promotion of heat pump bulk curing barn.The main results are as follows:(1)The coal-fired bulk curing barn uniformity of the dry bulb temperature in the horizontal direction is slightly greater than that in the heat pump bulk curing barn,and the dry bulb temperature distribution in the two types of bulk curing barn is high in the middle and rear part and low in the front part.The heat pump bulk curing barn uniformity of the dry bulb temperature in the vertical direction is slightly greater than that in the coal-fired bulk curing barn,and the dry bulb temperature distribution in the two types of bulk curing barn is highest in the bottom,second in the middle part,and lowest in the top part.The uniformity of the wet bulb temperature in the heat pump bulk curing barn during the curing process is greater than that in the coal-fired bulk curing barn.In the horizontal direction,during the curing process of the heat pump bulk curing barn and the coal-fired bulk curing barn,the wet bulb temperature is highest in the rear part,second in the front part,and lowest in the middle part.In the vertical direction,the wet bulb temperature distribution of heat pump bulk curing barn is high in the top and bottom,and the middle part is low.The temperature of the bottom wet bulb is highest in the early yellowing stage of the coal-fired bulk curing barn,and the middle part is the second,and the top part is lowest.From the late yellowing stage to the stem-drying stage,the wet bulb temperature was the highest in the top part,followed by the middle part,and the lowest in the bottom part.The distribution of dry bulb temperature is more uniform than wet bulb temperature in heat pump bulk curing barn and coal-fired bulk curing barn.And the temperature distribution of wet and dry bulb in the horizontal direction is more uniform than that in the vertical direction.The uniformity of the dry and wet bulb temperature in the yellowing stage in heat pump bulk curing barn and coal-fired bulk curing barn is higher than that of fixed color stage and stem-drying stage.(2)The dry bulb temperature responsiveness of the heat pump bulk curing barn during curing process is slightly lower than that of the coal-fired bulk curing barn,and the wet bulb temperature responsiveness is greater than that of the coal-fired bulk curing barn during the curing process.The responsiveness of dry bulb temperature is higher than that of wet bulb temperature during the curing process of heat pump bulk curing barn and coal-fired bulk curing barn.The responsiveness of dry and wet bulb temperature in horizontal direction is higher than that in vertical direction.The dry and wet bulb temperature responsiveness of yellowing stage in heat pump bulk curing barn and coal-fired bulk curing barn is higher than that of fixed color stage and stem-drying stag.The responsiveness of heat pump bulk curing barn and coal-fired bulk curing barn is the highest in the middle,while the responsiveness of the top part and the bottom part is lower.Moreover,the difference of dry and wet bulb temperature in the heat pump bulk curing barn is mainly negative,while that in the coal-fired bulk curing barn is mainly positive.(3)The heat pump bulk curing barn is more conducive to the transformation and accumulation of aroma causing substances of tobacco leaves.The chemical indexes and the chemical quality of the flue-cured tobacco leaves in the heat pump curing barn is greater.The heat pump bulk curing barn can improve the sensory quality of flue-cured tobacco,increase the aroma,reduce the irritation and make the taste more comfortable and mellow.Heat pump bulk curing barn can increase the proportion of orange and yellow tobacco.It can reduce the proportion of micro strip green and variegated tobacco.It can increase the availability,improve the economic characteristics of flue-cured tobacco.It can increase the average price of tobacco,and promote farmers to obtain more economic benefits.In the whole curing process,the automation degree of heat pump bulk curing barn is higher,and the baking cost is greatly reduced.(4)The simulation results of heat pump bulk curing barn show that: the hot air first enters the curing barn from the air inlet,passes through the fluid area at the bottom of the curing barn,reaches the front of the curing barn,and then moves through the tobacco leaf accumulation area to the upper part.After reaching the top of the curing barn,the hot air returns back and goes down through the tobacco leaf accumulation area and moves to the rear of the curing barn.At the same time,the hot air entering the tobacco leaf accumulation area will move to both sides of the curing barn until it fills the whole barn.The wind velocity in the tobacco leaf accumulation area is consistent.The rear temperature of the curing barn is higher than the front temperature,the top temperature is higher than the bottom temperature,and the middle temperature is higher than the temperature on both sides.Although there are some differences in the wind field and temperature field of the tobacco leaf accumulation area,the overall curing barn is relatively uniform,which can ensure that the whole curing barn is dried at the same temperature,creating a good curing environment for the curing of tobacco leaves.