CFD Numerical Simulation And Application Status Analysis Of Forced Ventilation And Waste Heat Recovery System In Wood Drying Kiln

With the traditional approach of ventilation,there has plenty of thermal losses carried by waste wet air in wood conventional drying kiln.To cope with this problem,a brand-new energy consumption saving technology,"Forced Ventilation and Waste Heat Recovery System",has been developed,which can improve the indoor and outdoor wet air exchange significantly in the process of kiln drying.For the purpose of putting forward to the theoretical basis and technological requirements on optimization design and application status of the system,methods of the Computational Fluid Dynamic(CFD)numerical simulation and application status analysis were used to study the characteristics of different segments in this system,such as the fluid flow and heat transfer property of thermal exchange system,the velocity and pressure regularity of forced ventilation system and the property of technology and economy about the whole system.The results indicated that:(1)Compared with old methods,which discards the wet air out of the kiln in direct way,thermal exchange system can efficiently recycle the waste heat throughout the whole drying stage.The recovery waste heat is used to warm fresh air,which can increase the temperature of fresh air ranging from 9.5 to 25.5? and reduce energy consumption.(2)As for the same drying progress,the small fan frequency is,the better heat recovery effect will be.But,considering the lower fan frequency which can diminish the pressure in this system so that wet air would not be eliminated out of the kiln,it is necessary to choose the moderate fan frequency,which can help the system to give play to the most effects.(3)The use of elbow can increase the local pressure loss.To reduce the loss of pressure,when to design the system,the number of elbows should be taken priority to configure the ducts within the limited space in rational ways.(4)With the help of methods of CFD numerical simulation and Orthogonal Experiment Design,the optimal combination is obtained,which includes that orifice diameter is 40mm and location is 2/5 and the inlet total pressure and dynamic pressure of the fan is 690Pa and 90Pa respectively.(5)The value of evaluation index for technological and economic analysis varies with the seasons change.Generally speaking,the waste heat utilization rate ranges from 24.8%to 30.0%,the waste heat recovery efficiency ranges from 21.54%to 24.13%,the energy-saving rate ranges from 12.23%to 22.74%.