Long-term Test And Simulation Study On The Characteristics Of Fouling On The Surface Of Enhanced Tubes

The enhanced tube is being used more often in water-chiller condensers because of their superior performance in heat transfer.The use of enhanced tubes in cooling tower systems is a very common application in HVAC industry.The heat transfer performance of enhanced tubes is affected by the fouling build-up on the heat transfer surfaces.The fouling resistance is one of the most important parameters for designing the enhanced tubes.The data of fouling resitance for smooth tube could not apply to enhaned tubes.Therefore,it is necessary to carry out an actual test about the fouling resistance of the enhanced surface,which provide a data basis for establishing the correlation between the fouling resistance of heat transfer tubes and operation conditions.The study takes the development of fouling as the research object,and do experiments of decoupling analysis and an actual(non-accelerated)fouling test with combined fouling(precipitation and particulate fouling),and analyze the influence of geometric parameters of enhanced tubes on fouling resistance.In the same time,the the study develops a initial model of particle fouling and proposes a new concept of effective thickness based on the Monte Carlo method.Firstly,the paper provides the description about priciple of the newly developed fouling test system.The formula of decoupling correction for gouling resistance was propsed to accurately quanty the value of fouling resi stance,based on the correlations developed by decoupling anlysis between overall heat transfer coefficient and heat flux or water velocity.Then,when the water velocity was controlled at ~1.6 m/s,an actual(non-accelerated)fouling test with medium-fouling potential water is carried out to determine the fouling resistance of nine tested tubes(8 enhanced tubes and 1 smooth tube),and the effect of the geometrical parameters of each surface on the combined fouling was analyzed,and the optimal surface geometric parameters under the experimental conditions were determined.Through continuous monitoring and control for heat transfer characteristics and water quality of the enhanced tubes,the project analyze the change laws of water quality,heat transfer coefficient,fouling resistance,and pressure drop variation of the cooling water side during the experiment.In addition,based on the Monte Carlo method,the initial physical model of particle fouling deposition process on the enhanced surface have been established with reasonable simplifications and assumptions.The particulate fouling deposition process has been simulated using MATLAB programming software.The initial model provide a reference for the simulation of combined fouling.Finally,in order to solve the problems,such as a long calculation time of simulation,large memory capacity ect,a new concept of effective thickness is proposed,which has been vertrified by sundden drop of particle deposition.And the effective thickness provides new solutions for large-scale simulations.Through the analysis of the simulation result,the relation between the effective thickness(or particulate fouling deposition process)and water velocity or diameter of tube is generalized.