Numerical Simulation On Plate Heat Transfer And Resistance Characteristics Of Plate Heat Exchangers

Plate heat exchangers are efficient and compact heat exchanging elements, and widely used in engineering fields such as petroleum, chemical, heating and ventilation, power, and so on. Compared to removable plate heat exchangers, all-welded plate heat exchangers elevate service temperature and pressure, having more extensive application range. The plate shape design and optimization has great theory significance and application value.In this paper, by adopting numerical simulation method, the heat transfer and flow resistance characteristics of triangle-boss plate heat exchangers are studied. Based on Fluent, the numerical analysis model of heat transfer and flow resistance in triangle-boss plate heat exchangers are established, and the influence of plate-shape geometric parameters on the flow state of heat transfer medium, heat transfer and flow resistance characteristics are analyzed in detail. The flow state of heat transfer medium, heat transfer and flow resistance characteristics of triangle-boss plate and concave-convex plate are compared and analyzed. Besides, a model establishment method for the simplified simulation of large-size plate is proposed, which could be used to analyze the medium flow, heat transfer and flow resistance characteristics of large-size plate.Multiple flow pass models of triangle-boss plate with different boss inclination, boss spacing and interior angle in boss section are established. On the basis of setting reasonable boundary conditions, the numerical simulations of heat transfer are conducted, the Nusselt numbers, heat transfer factors, friction factors in all flow passes under different Reynolds number are obtained, and hence the influence of plate-shape geometric parameters on the heat transfer and flow resistance characteristics of triangle-boss plate is summarized. Via fitting of plate-shape geometric parameters and Nusselt number, the heat transfer principles of triangle-boss plate heat exchangers (9000<Re<60000) are obtained, which contain the parameters of boss inclination, boss spacing and interior angle.According to the research of corrugated plates, two improvements of the plate boss distribution are proposed, with two kinds of concave-convex plates a total of four plate heat exchangers, and numerical simulations of the heat transfer and fluid flow of the seven flow passes in these plate heat exchangers are performed. The flow patterns, heat transfer factors and fiction factors of all these flow passes are compared, and the influence of concave-convex plate and triangle-boss plate on fluid disturbances, heat transfer and flow resistance characteristics is analyzed deeply and summarized. Plate with best heat transfer characteristic is selected, its forming performance is simulated numerically, and then plate with better forming performance is obtained by adjusting the face angle between short bosses and blank holding force.For the excessive number of elements and massive calculation data in the simulation model of heat transfer and fluid flow in large-size plate, according to flow patterns in the passes and the principles of numerical simulation, the grid model of flow pass during large-size concave-convex plates is established by reducing the plate size appropriately, which could meet the requirements of hardware computing power and simulation precision. The influence of concave and convex on the medium flow between the plates is analyzed, and velocity field, temperature field and pressure field of the cold and hot flow passes in the heat exchangers are obtained.