Particle Deposition Characteristics During Gas-solid Flow On Heat Exchange Surfaces

Heat exchangers are widely used in daily life and industrial production.Therefore,to improve production efficiency,experimental and theoretical studies related to the enhancement of heat transfer have been highly valued by the academic community.However,limited by the working environment of heat exchangers and the purity of the working medium,most heat exchangers suffer from the degradation of their heat transfer efficiency due to the generation of fouling during the working cycle.So,by establishing the mathematical model of micron-size particle deposition in a two-dimensional rectangular channel,with numerical calculation by the Euler-Lagrange method,this paper analyzes the effects of different factors on the particle deposition characteristics,and the heat exchange process by the field synergy principle,to explore the effects of particle deposition on the average synergy angle and vector size.Firstly,the critical velocity model of micron particles in the air in a two-dimensional rectangular channel is established,then the model is converted into a programming language and loaded into FLUENT for calculation by UDF(user-defined function),and the reliability of the data is ensured by being compared with related literature for verification.To reflect the effect of particle deposition on the continuous phase,this paper reveals the effect of particle deposition on the whole fluid domain by establishing a dynamic grid model.To explore the effect of different conditions of the continuous phase on the particle deposition characteristics,the inlet velocity,inlet temperature,wall temperature,and particle size are adjusted.Secondly,the above mathematical model is still used to study the effect of particle deposition on the average synergy angle and vector size.The results show that the wall roughness caused by particle deposition has a positive effect on the deposition of small particle size and a negative effect on larger particle size;the four single-factor conditions have different degrees of influence on the deposition characteristics of particles: Other factors being constant,the effect on the particle deposition characteristics intensifies under each condition in the following—a smaller inlet flow velocity,a higher inlet temperature,a lower wall temperature,or a larger particle size.the deposition of particles reduces the average synergy angle,indicating that the wall roughness developed by particle deposition will improve the inter-field synergy;but the deposition brings additional heat transfer and flow resistance,reducing the vector size,so the overall heat transfer intensity of the heat transfer process exhibits a gradual decrease with increasing particle deposition.In addition,the qualitative analysis shows that the effect of particle deposition on the heat transfer process is multifaceted,besides bringing additional heat transfer thermal resistance,it also weakens the velocity vector through additional flow resistance.Although the deposition of particles forms rough elements to enhance the inter-field synergy,the overall heat transfer process is still weakened due to the significant weakening of the vector magnitude by the resistance to heat transfer and flow.