| The drying of food to remove water needs to overcome the binding energy and free energy of the food itself,so in addition to using its own chemical energy and other energy,food also needs the help of external energy to complete this process,so food drying needs a large amount of external energy supply.Food production needs a large amount of biomass energy to be used as a heating source to provide a certain amount of heat for the food drying system to supply the demand of food drying production.Biomass energy is high in energy,suitable as a heat source to provide the required energy for the drying system,but high energy consumption rate and environmental pollution problems will also follow.If certain experimental research can be carried out in the heat transfer of grain drying,the heat transfer performance of the heat exchanger is analyzed,so as to provide some theoretical guidance for the optimization design of heat exchanger.As a major consumer of grain production,it is imperative for China to make full use of biomass resources,and it is also a necessary action to respond to the call of environmental protection and green development.The heat exchanger is an important equipment for heat transfer of 5HP-50 double-tower circulating dryer.The high-temperature flue gas passes through the flue gas pipe through the pressure difference and conducts heat transfer with the natural air crossing the outer pipe.5HP-50 towers circulating dryer heat exchanger is fork row tube drainage mode,this kind of arrangement can strengthen the horizontal sweep fluid strenuous exercise,fluid of vigorous exercise will improve the fluid turbulence intensity,and turbulence intensity related to the intensity of heat transfer,so the increase in turbulence intensity increases the overall heat transfer intensity,increase thermal efficiency.In order to achieve the goal of high quality,environmental protection,energy saving and high efficiency,it is of great significance to study the energy efficiency of heat exchanger of grain dryer in drying application field.The flow and heat transfer characteristics of5HP-50 double-tower circulating dryer heat exchanger are studied by numerical simulation and experimental analysis.Finally,the BP neural network prediction model was established by MATLAB to predict and analyze the energy efficiency of the dryer heat exchanger under different working conditions.The main work and innovation points of this paper are as follows:1.Using three-dimensional modeling software to Computer Aided Design(CAD)of the grain drier heat exchanger for 3 D modeling and 2 D modeling,according to the theory of fluid mechanics and heat transfer theory of heat transfer and fluid flow heat exchanger pipe were analyzed and summarized in this paper,exergy analysis and theoretical model of economy,the heat exchanger numerical simulation research on flow and heat transfer characteristics of Fluent19.0 using computational fluid dynamics software ANSYS,the numerical simulation calculation model of selecting select kappa epsilon model predominate.The numerical simulation results show that the flow resistance and pressure drop of the fluid flow are highly correlated with the different inlet fluid velocities.The numerical simulation study was carried out on the cold air transversal heat transfer pipeline with different relative humidity,and the research on the flow and heat transfer performance of the heat exchanger with different relative humidity was analyzed,and the heat transfer efficiency of the heat exchanger with different relative humidity was analyzed.2.Based on the field production and drying operation of grain,the field heat transfer and resistance of grain heat exchanger were studied.The experiments of grain drying under different conditions such as air inlet velocity and flue gas temperature were carried out,and the changes of heat transfer coefficient,pressure drop and Reynolds number of grain drying heat exchanger under different conditions were analyzed.The experimental study on the heat exchanger of 5HP-50 dual-tower grain dryer was carried out and the experimental data were analyzed.3.Combined with the method of experimental research,the heat exchanger was modeled based on BP neural network by combining theory and experiment.Thermal fluid were used respectively to the flue gas temperature,environment humidity,environment temperature,three parameters as input factors,to exergy during corn drying production efficiency,sustainability,and can improve the potential change law of three target parameters as the target function,using the Matlab software neural network model is established and some experimental data is used to model to train and validate the feasibility of the model,and finally with stay with the experimental data for the model fitting.The results showed that the exergic efficiency of the dryer heat exchanger varied from 8.32% to 13.96%,and the SI value varied from 1.08 to 1.16 during the experimental study on maize drying.The improvement potential increased with the increase of exergic loss,and the variation ranges were 643.35-1114.24 kw and 17.59-29.04 kw,respectively. |
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