Performance Analysis And Optimization Design Of Waste-heat Utilization Heat Collector

Rotary kiln,which internal temperature keeps at about 1300?,and out surface temperature is about 100? to 450?,mostly distributes in 280? to 350?,is the key equipment in the new dry cement production.To protect rotary kiln out surface,cooling fans were usually set up on the kiln.There is a great heat recovery potential in this kiln part,for its high out surface temperature.Focusing on the rotary kiln waste heat collectors,this paper studied the operation parameters influence and put forward the design method of the collector.The main research is as follows:Firstly,the theoretical calculation method is used to calculate the entropy production,entransy dissipation number and effectiveness of collector.Heat transfer and flow process in the collector are analyzed.After this,a several mathematical equations are set up and programed to calculate it in the Matlab software.Four different working conditions are selected to calculate in the program.Compared with the experimental results,the accuracy of theoretical calculation is verified.This paper selected various collector kiln surface temperature,inlet air temperature and inlet air velocity under the same working medium flow rate,the same inlet water temperature,the same emissivity.That simulates the different operation condition of collector in different seasons.This paper analyzes the entropy production number,entransy dissipation number and effectiveness to provide data reference to collector operation and design.Secondly,the effect of different running parameters of heat collectors are analyzed by numerical simulation.Pro/E software is used to establish the physical models of collector,which is simplified based on the collector' structure characteristics.The control equation,heat transfer model and turbulent model,as well as the basic hypothesis and boundary condition in the numerical simulation are introduced in this paper.Then the experimental values are compared with the simulation values.The error is acceptable,so the simulation method is accuracy.In order to analyze the collector performance under different working conditions,this paper selected the multiple variables to simulate.Focused on the heat transfer and flow characteristics,the surface emissivity,air flow velocity,mass flow rate of water and the kiln temperature were chosen as the variables,as they all have great influence on collector working performance.Thirdly,based on the above conclusions,this paper proposed single objective optimization method and multi-objective optimization method of heat collector design.The minimum area method,the minimum entropy method and the entransy dissipation extreme value theorem were used to heat collector single objective optimization design.When the minimum area method was optimized,the heat transfer area decreased by 33.82%.When the minimum entropy method was used,the entropy number decreased by 3.6%.After the entransy dissipation extreme value theorem optimization,the pressure loss decreased by 16.36%.In multi-objective optimization design,the heat transfer area and entransy number were chosen as the target function.Using the genetic algorithm,the Pareto front was obtained.And the minimum pressure loss design was analyzed.The results showed that the multi-objective optimization design method could improve the economical and heat transfer performance at the same time.