Illustration of Numerical Approaches

Abstract

In this chapter, a 240-tube bundle heat exchangers immersed in a titled thin enclosure is simulated to show a practical application of the models and numerical methods discussed in Chaps. 1–3. The governing parameters in the macroscopic, microscopic, and mesoscopic length scales corresponding to the enclosure width, tube diameter, and mesh size are obtained. Porous medium model simulations by projection method and nondimensional lattice Boltzmann method (NDLBM), and direct simulations by NDLBM are compared for the transient energy discharged, the Nusselt numbers, the distributions of isotherms and streamlines, and the CPU times. Given the same grid number and simulation time, the CPU time of the porous medium model simulations by using NDLBM is about 1/60 of that of porous medium simulations by using finite difference based on the projection method, and 1/20 of that of the direct simulations with the uniform code based on NDLBM. The porous medium simulations can only obtain Darcy velocity and volume averaged temperature, while the direct simulations can obtain both macroscopic and microscopic velocity and temperature.