Numerical Simulation On Heat And Mass Transfer Of Frost Formation On Finned Tube Heat Exchanger

Finned tube heat exchangers are extensively employed in various industrial applications. They are quite compact, lightly weight, and characterized by a relatively low cost fabrication. A comprehensive understanding on the performance of heat and mass transfer of finned tube heat exchangers is of prime importance to optimize the design of heat exchangers for refrigeration and air conditioning applications. Frost formation on finned tube heat exchanger occurs widely.When moist air comes in contact with cold heat exchanger surface whose temperature is below freezing point, frosting occurs. The vapor of the air becomes frost and the frost sticks to the surface of the heat exchanger. The frost acts not only as a thermal insulator between the surface and the humid ambient air, but also significantly reduces the performance of the heat exchanger, since the air passages become narrower and pressure drop generated becomes higher. With time goes by, the thickness of the frost layer grows. In addition, in order to ensure the defrosting period of finned tube heat exchanger, it is necessary to understand the characteristics of frost formation deeply.A small unit of finned tube heat exchanger is studied. From the simulation results of the model of small unit, the simulation performance of whole finned tube heat exchanger can be known. The continuous, momentum, energy and grid updating equations of frost formation on finned tube heat exchanger were described.。Using numerical method, the frost accumulation quantity and heat transfer capacity of evaporators are predicted, which is simplified to a quasi-stable problem for convenience. In every time step the process is considered to be stable and the obtained data, the frost thickness and the temperature of the frost surface are used as the boundary conditions in the next time step. According to the...