Advanced Building Thermal Simulation Coupling of Finite Volume Method and Nodal System

Energy modeling approaches have continued to advance to cater for emerging new design concepts towards "greener" solutions. Notwithstanding the advances in system modeling, there are still limitations in the capability of representing the "real"' environmental behavior with different building spatial configurations. For example, most current energy models adopt a "nodal" approach to simulate the heat transfer process in the building, with simplified heat resistors and capacitors network. Finite Volume Method (FVM) such as Computational Fluid Dynamics (CFD) on the contrary will perform detailed computation on the temperature profiles and air flow fields, which could supplement the nodal model for the building energy simulation with heat transfer coefficients airflow rates and etc. With the rapid development of computation power, the computation time of CFD is decreasing, it is highly necessary to develop an integrated thermal simulation model that combines the advantages of both the nodal and the FVM model, which will improve simulation accuracy with acceptable computation time.;Mesh generation is a critical and probably the most manually intensive step in CFD simulations in the architectural domain. Mesh generation for CFD simulation in buildings poses special challenges. Firstly, the span of the dimensional scales encountered in design is large. Secondly, the geometry model of a building usually involves non-manifold surfaces. Thirdly, the lack of data interoperability between CFD simulation tools and major architectural Computer Aided Design tools makes the application of CFD in architectural design an expensive practice.;Research by NIST (National Institute of Standards and Technology) estimates the cost of inadequate interoperability in the U.S. capital facilities industry to be ;In addressing the challenges, this dissertation work implemented a coupled simulation platform between a nodal model and a CFD tool with advanced mesh generation. Eight days of natural ventilation simulation for the live retrofit project of building 661 at the Philadelphia Navy Yard was conducted. Significant differences have been identified in heat transfer coefficients and airflow rates between the coupled simulation and the nodal model. The differences of heat transfer coefficients between the nodal model and the coupled model range from 7% to 188% for exterior surfaces and range from 10% to 80% for interior surfaces. The differences of airflow rates between the two models are from 100% to 770%. An interpolation model was developed based on the simulation period of June 1st to June 8th. The weather analysis shows that there are 854 hours annually, which are suitable for natural ventilation in Philadelphia. It is found that with the 8 days' simulation results, the interpolation model is able to predict 266 (35% of 854) hours of airflow rates annually, with excepted error of 24%.;The mesh generation algorithm development has two stages. First, a prototype automatic two dimensional mesh generation tool is implemented to generate adaptive quadrilateral meshes from architecture drawings for CFD simulations. Starting from two dimensional image data, adaptive quadrilateral meshes are constructed automatically. The nearly orthogonal boundary layer is generated and the thickness is controlled to facilitate various simulation scenarios. Second, a three dimensional automatic mesh generation tool was developed to generate the adaptive hexahedral-dominant mesh and the uniform all-hexahdral mesh from architecture conceptual design tools for CFD simulation in the architectural domain. Simulation experiments show that the adaptive 3D mesh reduces the number of elements significantly (> 90%) while maintaining the accuracy compared with uniform mesh. The three dimensional meshing tool will take as input the VRML model generated by Google SketchUp. The mesh generated shows good quality in terms of shape parameters, the scaled Jacobian, and the condition number of the Jacobian matrix.;A prototype BIM platform that supports interoperability between the energy simulation tool and the CFD tool was developed. The manual time required to create the EnergyPlus model and the Fluent Model on the prototype BIM platform is reduced by 87 ∼ 90% compared to that required on the non-BIM supported approach for similar models. Based on the developed prototype platform, key information requirement for the coupled simulation was identified. Dynamic information, which are the properties of an object that are dependent on changing geometry configurations, system operations, or boundary conditions, was proposed as Domain Object Model. The proposed dynamic information objects are heat transfer coefficients for building envelop components and airflow rates for openings.