Design Of An Intelligent Storage System For Sweet Potatoes And Optimization Of Gas Component Concentration Distribution

Sweet potato is one of the most important crops and plays a crucial role in ensuring food and nutritional security amidst dynamic global climate changes.However,sweet potatoes are generally characterized by thin and delicate skin,making them susceptible to cuts,abrasions,cold damage,pathogen infestation,and oxygen deficiency,leading to multiple damages.Post-harvest storage of sweet potatoes remains a major bottleneck in the sweet potato industry.To minimize losses,this paper proposes an intelligent storage system design concept for sweet potato storage processes.Additionally,improvements are made to the arrangement of shelves within the storage facility,and a folding turnover box assembly is designed to reduce losses during transportation and storage.According to the"Size Series and Technical Requirements for Plastic Collapsible Transit Boxes for Fruits and Vegetables"（GB/T 39907-2021）document,the recommended size for foldable,preassembled turnover boxes is 600 mm×400 mm×340 mm.To simulate the actual storage conditions,medium-sized sweet potatoes were modeled as long rotating ellipsoids and stored in standardized turnover boxes.The species transport model,porous medium model,local non-thermal equilibrium model,and pre-test were used to determine the air supply parameters for the curing warming phase,curing internal circulation phase,post-curing cooling phase,and storage internal circulation phase.The temperature,humidity,velocity,O₂ concentration,and CO₂ concentration distribution in the cargo area during the curing ramp-up,curing,post-curing cooling,and storage phases were also studied.The results of the study show that（1）increasing the air supply temperature and speed is conducive to shortening the time to reach the target curing and storage temperatures,respectively,and that the temperature inhomogeneity coefficient of the whole process is larger.When warming up,curing,and cooling down the storage,the air supply fluid mixed with the air in the storage warehouse causes large temperature fluctuations in the early stage,and when the two are mixed for a short time,the physical properties of the sweet potatoes stored in the cargo area and the storage volume determine the subsequent warming and cooling processes.40℃ is the optimal curing air supply temperature,and the time required for the cargo area to reach the target curing temperature is 5.85 h.10.00 m/s is the optimal post-healing cooling air supply speed,and the time required for the cargo area to reach the target storage temperature is 8.47 h.In addition,due to the generation of sweet potato respiratory heat,the internal temperature of the cargo area took less time to reach the target curing temperature and more time to reach the target storage temperature.（2）At different air supply speeds,O₂ and CO₂ concentrations were evenly distributed and met storage standards due to forced air flow in the storage.An air supply speed of 6.00 m/s is better for the curing internal circulation phase,while 4.50-5.00 m/s is better for the storage internal circulation phase.These speeds ensure that the temperature and humidity of the cargo area are maintained,the flow rate is within the optimal range,and the uniformity is good.（3）During the whole storage process,the temperature,velocity,relative humidity,O₂concentration,and CO₂ concentration distribution on the surface of the cargo area under different design air supply speeds are similar;the temperature and relative humidity on the upper surface of the first two layers of the cargo area and the closer to the air supply outlet are easily affected;the velocity on the bottom part of the cargo area is easily affected;and changing the air supply speed will not affect the main distribution characteristics.The velocity field on the surface of the cargo area is less correlated with the humidity field distribution,and the temperature field is negatively correlated with the relative humidity field,and the distribution state is similar.（4）Due to the physical parameters of the sweet potato itself and the forced flow of fluid in the storage,convective heat exchange occupies a dominant role compared to conduction heat,causing a lag in temperature changes inside and outside the cargo area during storage.The respiratory heat of the sweet potato affects the unbalanced potential difference in fluid temperature,which to some extent affects the heat convection in the cargo area and then affects the temperature uniformity.In the whole storage,the difference of temperature distribution in the internal section of each box in the cargo area is related to the internal fluid flow;for the internal temperature field,the low temperature of the box in the part where the fluid flows in is due to the resistance generated by the presence of sweet potatoes inside the box,which leads to a smaller velocity in the outflow process,thus causing the difference of temperature distribution in the same box;in addition,there are vortices inside the two columns of boxes near the right wall,and the flow direction and the size of the two columns of the right wall box and the left two columns of the box’s internal temperature are different.The fluid flow direction inside the cargo area can be changed by the air supply speed,and the size of the air supply speed and the fluid flow direction inside the box have a great influence on the temperature distribution inside the cargo area.