Research On Dirty Blockage Diagnosis And Wear Of Outdoor Heat Exchanger Based On Image Processing Technology

As one of the renewable energy utilization technologies,air-source heat pumps are widely used in the context of clean heating.Tube-fin heat exchangers are commonly used outdoor heat exchangers for air source heat pumps.When the heat exchanger is exposed to the outdoors,dust accumulation,clogging,abrasion,etc.will occur,especially in the northwestern region where there are many particles such as wind and sand all year round.The above phenomenon is more obvious.The deposition and erosion of particulate matter on the surface of the heat exchanger for a long time will form dirt and wear,which will affect the heat exchange efficiency and operational safety of the unit.It is also contrary to the original intention of the efficient application of air source heat pump technology to contribute to carbon emission reduction.Therefore,the study of the clogging and wear of finned tube heat exchangers for air source heat pumps has important theoretical significance and practical application value.This paper takes the finned tube heat exchanger for air source heat pump as the research object,uses the theory of gas-solid two-phase flow,and uses the method of numerical simulation to calculate the movement law of the gas phase and the discrete phase in the heat exchanger channel,and analyze the airflow The relationship between speed,particle size,concentration and deposition,and erosion,as well as the formation of clogging and wear;At the same time,based on image processing technology and numerical simulation,based on the image information of the actual outdoor heat exchanger as a blueprint,A method for identifying the degree of clogging of outdoor heat exchangers in ASHP is proposed and verified by experiments.The main research conclusions are as follows:(1)The trajectory of particulate matter is affected by drag force and inertia force.Small size particles are easily affected by the airflow drag force,and a little number of small size particles are deposited in the low-pressure area on the windward side and the eddy current area on the leeward side of the heat exchange pipe.Large size particles are easily affected by the inertial force and deposited in the bottom area of the heat exchanger.With the increase of airflow velocity,the area of turbulent region increases,the number of small particle size in turbulent region increases,and the probability of collision between particles and the surface of heat exchanger increases.(2)With the increase of gas flow rate,the deposition rate of particulate matter on the surface of the heat exchange tube and fin increases first and then decreases.The particle deposition rate on the fin surface is less than that on the heat exchange tube surface.With the increase of particle size,the surface deposition rate of fin and heat exchange tube increases first,then decreases,and finally tends to be flat.The average deposition rate on the surface of the tube and the fin increases with the increase of particle concentration.(3)The average erosion rate of the heat exchange tube and the fin surface increases with the increase of the gas flow rate;With the increase of particle size,the average erosion rate of heat exchanger surface increases first,then decreases,and finally becomes flat.When the particle size is 25μm,the erosion rate of the heat exchanger tube appears at the peak.With the increase of particle concentration,the average surface erosion rate of the heat exchanger increases linearly.Among the above three influencing factors,the impact of airflow velocity on the erosion of large particle size is greater than that of particle size,and the impact of concentration is the least.In the erosion caused by particles smaller than the peak particle size,the influence of particle size on erosion is greater than that of airflow velocity.(4)By processing the fouling image information of the actual outdoor heat exchanger,the changing relationship of the fouling coefficient on the surface of the heat exchanger with the running time was obtained,and the identification method of the fouling degree of the ASHP outdoor heat exchanger was proposed.According to the fact that the particulate matter is dispersed in the early stage of ash accumulation and the deposition rate increment is the maximum,the optimal time point for scaling is determined when the fouling degree reaches 4%,and the corresponding actual operation days are 84 days at this time.