颗粒外掠含不同掺混单元平板的流动换热特性

The shell-and-plate heat exchanger plays a significant role in the concentrating solar power systems. For improving the heat transfer performance of the shell-and-plate heat exchanger, the effects of plane, trapezoidal mixing element, elliptical mixing element, trapezoidal-elliptical mixing element and trigonal mixing element on particle flow and heat transfer were studied by discrete element method. The research shows that the blending rate of the plane is almost zero, and the blending rate of the trapezoidal blending unit is the highest. When particles flow around the trapezoidal mixing element, elliptical mixing element, trapezoidal-elliptical mixing element and trigonal mixing element, the temperature boundary layer is destroyed and redeveloped in the downstream region of the mixing elements. In the upstream region of the mixing elements, the mixing elements have an impediment to particle movement. The elliptical mixing element is the most impeded to its upstream particles. The feature velocity of particles is maximum in the downstream of the trapezoidal mixing element. When the particles move along the plane, there is no mixing phenomenon and the mixing efficiency of the plane is approximately zero. The average mixing efficiency of trapezoidal, elliptical, trapezoidal-elliptical and trigonal mixing elements are 3.8, 2.6, 3.2 and 2.5, respectively. The mixing efficiency of trapezoidal mixing element is the highest. In the downstream region of mixing elements, the heat transfer coefficients of trapezoidal, elliptical, trapezoidal-elliptical and trigonal mixing elements are significantly larger than that of the plane (average increased by 41.5%, 31.5%, 28.9% and 25.3%). Compared with other mixing elements, the flow and heat transfer characteristics of trapezoidal mixing element is the best.