Study On Heat Transfer Characteristics Of Industrial Building Inner Surface Under The Coupling Effect Of Purified Circulating Air And High Temperature Heat Source

Industrial buildings produce pollutants such as particulate matter,CO and NO during the production process,which seriously affects the health and work efficiency of workers.To solve the problem of indoor air pollution,mechanical ventilation is needed,but traditional mechanical ventilation systems have high energy consumption and low efficiency.Therefore,in order to save energy in buildings and improve indoor air quality,this article takes the Inner Mongolia casting cleaning workshop as the research object and proposes a controllable circulating air purification technology.After the high-temperature particles and harmful gases associated with the thermal process are purified and dust removed,their emission concentration reaches below 30%of the occupational exposure limit and enters the workshop for recycling.According to the Unified Standard for Energy Efficiency Design of Industrial Buildings（GB 51245-2017）,the energy consumption of the casting workshop depends on the heat transfer process between the ventilation airflow and the interior surface of the building.Therefore,this article studies the heat transfer characteristics of the interior surface of the building under the coupling effect of purified circulating air and high-temperature heat sources,providing a theoretical basis for further improving the technology of purified circulating air in industrial buildings.Firstly,to remove a large amount of high-temperature particulate matter,CO,NO and other pollutants generated by the hot process in the casting workshop,static filtration experiments were conducted to analyze the filtration characteristics of high silica membrane filter materials,alkali free glass fiber expanded membrane filter materials,and polyester filter materials,and the steady-state kinetics experiment was conducted to study the CO-SCR performance of Cu-Mn-Ce-O_xloaded high silica filter media（HSF）.The results show that the high oxygen silicon membrane coated filter material has excellent temperature resistance and mechanical properties.When the air flow temperature reaches 200℃,the mechanical strength can also reach 99%.Moreover,the filtration efficiency of high oxygen silicon membrane coated filter media for particulate matter can basically be maintained at over 90%.And for particle sizes greater than 5μm particulate matter,maintain filtration efficiency above 99%,can effectively remove particulate matter from high-temperature flue gas.And when the temperature of the gas stream was 260℃,the conversion rates of NO and CO could reach 69%and 71%for Cu-Mn-Ce-O_x/KH550/HCl@HSF.The activation energy of CO reduction reaction is 19.7 k J/mol,which is only 50%of the current commercial vanadium titanium based catalysts.Therefore,prepared catalytic filter material Cu-Mn-Ce-O_x/KH550/HCl@HSF has good high-temperature particle filtration and NO and CO removal effects.Secondly,in order to reveal the transport characteristics of particulate matter under the coupling of circulating air and high-temperature heat source,a numerical calculation method coupled with CFD continuous phase model and discrete phase model（DPM）was used to analyze the variation law of particulate matter concentration and ventilation energy consumption in the workshop under different air velocities of inlet air and circulating air.The results show that inlet air and circulating air velocity can affect the airflow distribution.The length of the horizontal jet increases as the inlet velocity increases.The higher the circulating air velocity,the greater the inhibition effect on the rising thermal plume,and the more advantageous the removal of particulate matter.For the circulating air system,the particle concentration in the workshop decreases with the increase of inlet air and circulating air velocity.On the one hand,when the inlet air velocity is low,the fresh air jet cannot reach the side exhaust outlet from the inlet,forming eddies between the workbenches.On the other hand,increasing the air velocity will dilute the particle concentration in the workshop.When comparing the particle concentration in the workshop with and without circulating air,it was found that the particle concentration in the workshop with circulating air was almost half of that without circulating air.The ventilation efficiency when the recirculated air velocity is 0.42 m/s is similar to that when the exhausted air velocity is 1.05 m/s,and the energy consumption of the exhaust system is approximately eight times that of the circulating air system.This indicates that circulating air technology can effectively improve the air quality inside industrial buildings while also reducing ventilation energy consumption.Then,the characteristics of mixed convection flow field in a foundry workshop under the mixed action of clean circulating air and high temperature heat source were studied.The effects of heat source temperature,fresh air velocity,circulating air velocity,supply air temperature,and tuyere size on air distribution were analyzed.The flow characteristics and mechanisms of airflow have been discovered:（1）Mixed convection is forced convection dominated by the inertial forces of horizontal jets and top air supply,as well as natural convection driven by the buoyancy of heat source plume and buoyancy caused by the temperature difference between indoor air and air supply airflow.（2）When the inertial force of the horizontal jet is strong,it will inhibit the rise of the thermal plume and push the thermal plume towards the outlet.When the buoyancy generated by the thermal plume of the heat source is strong,it will cause the horizontal jet to deflect upward,unable to suppress the rise of the thermal plume,and generate vortices throughout the room.（3）To ensure the comfort of the personnel area,it is necessary to determine the effectiveness of air supply.When Ri₀is greater than 900 and Ri_reis greater than 1,the air supply fails.Finally,the heat transfer characteristics of the interior surface of a building using medium and high temperature heat sources for clean circulating air were studied.It is obtained that an increase in the difference between the heat source temperature and the wall temperature will increase the average heat transfer coefficient of each internal surface,and the total heat transfer coefficient of the room will also increase.At the same time,with the increase of fresh air velocity and circulating air velocity,the average heat transfer coefficient of each surface will decrease,and the room heat transfer coefficient will also decrease.When there is a significant difference between the heat source temperature and the wall temperature,the heat transfer on the inner surface is determined by the heat source temperature.The energy efficiency first increases and then decreases with the increase of temperature difference,and increases with the increase of fresh air speed and circulating wind speed.Compare the total heat transfer coefficient of the ventilation control room with the heat source wall temperature differenceΔT,fresh air velocity V₀and fresh air ratioγ_f,the fitting correlation between the average total heat transfer coefficient of the total wall surface of the building and the temperature of the heat source is h_total=14.55*e^{（ΔT）/（234.96）}+17.2*e^-V₀/0.098+14.84*γ_f-24.82,obtained important indicators for calculating energy consumption in industrial buildings,providing a basis for further promotion and optimization of circulating air technology for energy conservation in industrial buildings.