Research On Heat Transfer Performance Of Precooled Type Evaporative Air Cooler

Environmental problems have become increasingly prominent,and the energy crisis has further deepened.To actively respond to the national call for energy-saving and emission reduction policies,petrochemicals,power plants,and oil refining and other fields are constantly exploring efficient,energy-saving,and environmentally friendly heat exchange equipment.Evaporative air coolers that use latent heat of vaporization to take away a large amount of heat have been widely used in recent years due to its high efficiency.However,it still has some drawbacks,such as the formation of scale on the wall of the tube and the narrow cooling range.For this reason,the precooled type evaporative air cooler came into being.However,the theoretical guidance for the design of this new type of heat exchange equipment is not yet mature,and its practical application experience is still insufficient.This article relies on independently designed and established precooled type evaporative air cooler for pilot plant to examine the effects of process media flow,process medium inlet temperature,air volume,and spray water volume on the heat transfer performance of the precooled type evaporative air cooler.The results show that when the frequency of the hot water pump is controlled at 36 Hz,and the frequency of the fan and circulating water pump are 45 Hz and 40 Hz,the heat transfer effect is the best.At this time,the total heat flux density can reach 11 k W/m2,and the tube-outside heat transfer coefficient of the wet part can reach 2000 W/(m2·K).Appropriately increase the inlet temperature of the process medium,the heat exchange capacity can be further enhanced.The enhancement of the heat transfer effect of the wet part increases the temperature of the secondary air,thereby affecting the heat transfer capability of the dry part.In addition,the heat exchange effect of the dry part is not optimal when the wet part achieves the best heat exchange effect.From the viewpoint of the conservation of heat and mass,the thesis analyzes the heat and mass transfer process theoretically,and derives four ordinary differential equations to describe the entire heat transfer process,and gives the boundary conditions.The theoretical difficulty of the complex tube-outside heat transfer coefficient was studied in depth.The experimental data of the heat transfer of the precooled type evaporative air cooler was imported into the SPSS software for multiple linear regression analysis.The best mathematical model for the fin tube-outside heat transfer coefficient of dry part was obtained and the goodness of fit was 0.891,and the model was evaluated comprehensively and statistically;The heat transfer performance of the experimental system during dry and wet operation was further compared.When only examining the influence of wind speed on the tube-outside heat transfer coefficient of the fin tube bundle,the goodness of fit of the corresponding model decreased from 0.782 at dry running of the system to 0.642 at wet running of the system.The results show that the dry part of the precooled type evaporative air cooler is greatly influenced by the wet part;the wind speed is always the most significant factor affecting the tube-outside heat transfer coefficient of the fin tube bundle;The mathematical model of heat transfer established by regression can well represent the experimental results and provides the empirical guidance and theoretical basis for the practical application and optimization design of the precooled type evaporative air cooler.