Optimization Design Of Indoor Cooling System For Edible Mushroom Based On CFD

Industrialized production of edible fungi is a new way of agricultural cultivation.At present,global agricultural production is shifting from industrialization and largescale production to intelligent and refined control.The edible fungus industry in China has basically completed the transformation from decentralized,workshop-style production to factory-scale,large-scale production,and there are still great promises for intelligent and fine control.The edible fungus factory production generally adopts the method of concentrated heat exchange in a large-density accumulation culture bottles,and the heat generated by the growth of edible fungi in the bottle body is discharged.If the arrangement of the bottles and the layout of the fans are unreasonable,the problems such as uneven distribution of ambient temperature in the cultivating room and excessive design power of the cooling system are easily caused,which seriously affects the output of the edible fungus.Therefore,the study of reasonable bottles and layout of fans are an important guarantee for improving and ensuring the yield of edible fungi.In view of the problems of uneven distribution of ambient temperature and unsynchronized mushrooming in the current culture room of edible fungi,a Flammulina velutipes greenhouse in Shanghai was used as the research object,and the calorific value of different growth stages of Flammulina velutipes was measured for the first time.Computational Fluid Dynamics(CFD)Fluent software is used to get the simulation of temperature and velocity field in the mushroom.The simulation results are in good agreement with the field measurements.Based on the analysis of the internal temperature field and flow field characteristics of the original factory building,four optimization schemes were proposed and CFD simulation was conducted.The optimal scheme was selected to provide a reference for the control of the fine HVAC(Heating,Ventilating and Air Conditioning)in the edible fungus factory.The main research contents are as follows:1.The relationship between calorific value of Flammulina velutipes and its growth cycle and ambient temperature was studied.For the two main factors affecting the calorific value of Flammulina velutipes,according to the principle of equivalent substitution,the self-made experimental equipment was used to simulate the heating effect of Flammulina velutipes in the thermal insulation box on the internal air,and the calorific value of each bottle of Flammulina velutipes was calculated.The results show that the calorific value of Flammulina velutipes is mainly affected by different growth stages,and the calorific value of Flammulina velutipes show an upward trend in the 0-12 days of mycelial stage,peaked in 12-20 days,and the maximum value is about 0.15 W per bottle.After 20 to 24 days,it slowly decreases and the calorific value is about 0.1W per bottle.Different growth environment temperature has no significant effect on the calorific value of Flammulina velutipes.2.Two three-dimensional models of bottle flasks and Flammulina velutipes culture rooms were established.The model of bottles was used to simulate the pressure drop produced by the air through the gap between the bottles,thus determining the pressure drop in the unit length and the correlation of the air flow resistance system with the air flow rate.On the basis,the area of the bottles in the mushroom was defined as the porous medium area,and the correlated expression was used to simulate the air flow and temperature fields of the whole mushroom,the simulation results were compared with the field measurement results.The results show that the difference between the average temperature difference and the numerical simulation results in the three regions of 0.1 m,1.8 m,and 3.5 m from the surface of the mushroom is about 0.3°C,which is basically consistent.3.Four kinds of HVAC optimization schemes were proposed.Based on the simulation results of the prototype plant,the problems of large resistance in the box area,insufficient cold air power,and overheating under the fan were analyzed.On the basis of the original model,four optimization schemes were proposed,such as adding nozzles and changing the outlet of fan.The results show that the flow and heat transfer of air in the growth area of Flammulina velutipes can be significantly improved by adding the lateral gap of the plan 4,and the temperature in the growth area of the Flammulina velutipes bottle is concentrated at 13°C,and the temperature difference is the smallest.