CFD Simulation for Sustainable Building Design

Abstract

In this chapter, the computational fluid dynamics (CFD) technique is described for accurate simulation of fluid and heat flow in sustainable technologies and buildings. The technique is demonstrated using three examples; one for each of three different types of flow: (1) steady state in wind- and buoyancy-driven natural ventilation; (2) compressible flow in a solar-powered ejector for cooling; and (3) transient state flow in a horizontal-coupled ground source heat pump for heating/cooling of buildings. When naturally ventilating a building, a double skin facade can enhance the buoyancy effect, but the impact of wind is less certain compared to buoyancy; not only in terms of its unpredictable nature, but also its interactions with buoyancy. The performance of a solar-powered ejector is influenced by the nozzle position, and the ideal position for the nozzle outlet is near the diffuser entrance. The heat extraction/injection capacity of a ground-coupled (horizontal) heat exchanger for long-term operation is lower than that used in current design guidance for ground source heat pumps. The technique can also be used for optimization and performance assessment of other technologies and solutions for sustainable building design. Learning Outcomes: on successful completion of this chapter, readers will be able to: (1) grasp the underlying principles of CFD and its governing mathematical models and equations, (2) understand the type of applications of CFD and how findings can influence sustainable building design and technology, (3) appreciate the types of conditional requirements that are necessary in order to conduct a simulation, and (4) have a limited knowledge about natural ventilation in offices, ejector refrigeration, and ground source heat pumps (GSHP). This chapter explains the basics of CFD and illustrates its potentials for sustainable building design. The partial differential equations for fluid and heat flow and the solution method are introduced, followed by three examples for simulations of natural ventilation, solar cooling, and ground source heating of buildings. Emphasis is placed on the accuracy of simulation from model setup to solution convergence.