IBPSA1991

The simulation complexity of the thermal behaviour of buildings can be reduced by splitting it up as a hierarchical system of linked components. The behaviour of each component and its relations to the other components are modelled by an object oriented approach. We describe an Ada implementation of these concepts and a simple example of a multilayer wall at the end of this article.

From the observation that existing simulation programs exploit neither the subjacent parallelism in building energy management problems nor parallel computer possibilities, we develop certain principles and apply them to a well-known program, TRNSYS.

The current generation of building simulation software is based upon separate building, mechanical system, and equipment simulations. This scheme evolved primarily because of memory limitations of the computers which were used to develop the programs. Hardware advancements have eliminated some of these limitations so the separate building and system scheme needs to be reevaluated.

Increasing design standards within the building industry mean that some form of pre-construction testing of the building envelope is required. Expensive and time consuming field tests are becoming more impractical whereas the cost-effectiveness and greater flexibility of computer simulations will allow them to play an increasing role in building design. An expanding database of actual construction properties is needed to assist the use and advancement of existing models.

The air flow pattern and temperature distribution in a naturally ventilated classroom were simulated using CFD techniques. The simulation model consists of equations for the conservation of mass, momentum and thermal energy, taking account of the effects of buoyancy and obstacles in the room. The well known k-e turbulence model was used to simulate the effect of air turbulence. Close to the inside surface of the room and the obstacle boundary, the wall-function equations were used for momentum and heat flux. Heat sources existing in the classroom were included in the simulation.

Mathematical models are presented that account for the mass transport processes associated with isothermal reversible sorption in building materials. These models account for a) the equilibrium limits of reversible sorption processes, b) boundary layer diffusion transport at the adsorbent surface, and/or c) diffusion transport within the adsorbent proper. Three distinct families of models are formulated with individual members of each family distinguished by the sorption equilibrium relation used in their formulation.

The developments in the computer-aided building design will enable designers to improve the energy performance in buildings, through a more appropriate design which will be better structured, will learn from previously accumulated knowledge (e.g., heuristics, databases), and will use new methods for the generation and evaluation of the design alternatives.

Well insulated walls of residences experience temperature depression in their outer layers during cold weather, causing moisture to condense on the surfaces. A predictive model capable of identifying the conditions that potentially lead to condensation or high moisture levels has been developed. The model utilized includes both moisture storage and distribution effects by utilizing the general form of the thermal energy and moisture conservation equations for each layer of a wall of typical residential construction, utilizing materials such as wood siding, insulation, and gypsum board.

SIMULAR AIR is a computer code for calculating the three dimensional transient indoor air flow using a k,e-turbulence model. It solves the nonlinear partial differential equations for momentum, energy, continuity, turbulence and air purity by an implicit time marching technique. The equations are modeled by a finite volume procedure. The model handles a variety of flow, temperature and heat flux boundary conditions including prescribed inflows and outflows. All boundary conditions can be defined time dependent.

The rapid development in the thermal energy modelling requirements for buildings, marked by the need to integrate many phenomena, has led the Applications de l'Electricit department at Electricit de France to develop a general energy simulation tool called CLIM 2000. Beyond the production of the software, our approach is to provide the specialists in the 7arious fields involved in the creation of the model library, with common formalisation rules ensuring clear and unambiguous expression of their work.To do this, we have drawn up a method based on a thermodynamic approach to the phenomena.