Numerical Study On Heat Transfer And Flow Drag Characteristics Of Offset-Strip-Fin Compact Heat Exchanger

Offset-Strip-Fin compact heat exchanger is widely used in industrial application, such as aviation and air separation, because it has high heat transfer coefficient and compact structure. With the rapid development of refrigeration and air conditioning, compactness is getting more and more important, so Offset-Strip-Fin heat exchanger has good prospects in Air-condition application. However, its internal mechanism of operation is very complex, and little work was done to study its operation in unsteady laminar flow conditions.On the basis of previous experimental and theoretical studies, two-dimensional numerical model is developed to describe heat transfer and flow drag of Offset-Strip-Fin heat exchanger. In steady and unsteady laminar flow conditions, the SIMPLE algorithm is carried out to simulate the heat transfer and flow drag of fins that have different arrangement. The predictions from the model agree well with the experimental data, image of visualization and empirical correlation. It is manifested that the model and algorithm are both feasible. According to the results of computation, it indicates that in the steady laminar flow condition, heat transfer is mainly affected by the thickness of boundary layer. At the former surface of fin, heat transfer is enhanced because of thin boundary layer. For the thickness of fin, passage between two fins becomes narrow and flow is accelerated, which make heat transfer enhanced at the cost of large loss of pressure. When the laminar flow becomes unsteady, vortex will emerge regularly in the field behind last fins, which is similar to famous Karman Vortex Street. In this condition, flow and heat transfer become very complex.The data of computation is dealt with and the fields of velocity, temperature and pressure are depicted. Furthermore, the effect of number and arrangement of fins is analyzed. Such analysis is helpful to understand the internal mechanism of the operation of Offset-Strip-Fin heat exchanger. This work can be used for optimization studies and design of this compact heat exchanger.