Study On The Law Of Particulate Deposition On The Surface Of Fin-and-tube Heat Exchanger

The particulate deposition on the surface of heat exchanger not only caused the problem of indoor air quality but also increased the energy consumption, and furthermore influenced the precision of temperature control of air conditioning system. The research on the law of particulate deposition and analysis about the particulate properties depositing on the surface of the heat exchanger had important meaning to strengthen the heat exchange, optimize the structure design of the heat exchanger and clean the heat exchanger regularly. The particulate deposition on the surface of the heat exchanger can be divided into three parts, such as the particulate deposition on the front-end edge of the fin, on the coil surface, and on the finned surface of the heat exchanger.The feature of the particulate depositing on the surface of the outdor heat exchanger was studied, and the results showed that the average diameter of the depostiton was between 8~17μm, and the curve of particle size distribution showed two or three peaks. The particulate mainly deposited on the front-end of the fin, and the crosslink phenomenon was serious on the top of the surface of the heat exchanger .In this disseration, numerical simulation was used to research the velocity field of dusty airflow flowing through the fin-and-tube exchanger, and the different velocity field distribution on the influence of particulate deposition was analysed. The results showed that the large diameter particulate deposited easyly on the front-end parts of the fin under the action of interception and collision. The influence of the coil was greater than the surface of the fins on the velocity field of the heat exchanger, and the amount of the deposition on the windward surface of the front coil was larger than the rear coil. Moreover, the small size particulate deposited on the leeward area of the coil more easily .The isolated single fiber capture theory was used to analyse the particulate deposition on the coil of the heat exchanger, and the relationship between intercept deposition efficiency and the particle size, head-on wind velocity, and other parameters was analyzed. With the increase of the particle size, intercept deposition efficiency of the coil increased firstly, and than decreased. The small diameter of the coil and head-on wind velocity made the particulate deposite on the coil more easyly.The heat transfer coefficient, heat exchange area, the pressure drop and the paticulate deposition should be comprehensive considered when determining the structure size of the heat exchanger.