IBPSA1991

This paper describes the techniques used within the ESP environment# to simulate coupled heat and mass flows in integrated building and plant systems. In particular, it describes the equation-sets used to represent inter-zonal (building) and inter-component (plant) fluid flow, the method used for the simultaneous solution of these non-linear equations, and the solution coupling of the heat and mass conservation equation-sets. By means of a brief description of a case study, the application in a real building performance evaluation context is demonstrated.

Analytical solutions for coupled diffusion of heat and moisture through a material are used to develop a generalisation of the wellknown 2 x 2 matrix method for describing heat flow only. A new 4 x 4 matrix is derived which relates temperatures, humidities, heat flows and moisture flows at one surface of a slab with those at the other. Multilayer slabs and surface boundary conditions, including moisture-impermeable surfaces, are easily handled by multiplication of matrices.

A first order correction to uni-directional heat transfer is proposed, so that multi-dimensional heat transfer effects can be accounted for with only a moderate increase in storage and CPU timerequirements. The model has been implemented into the ESP building energy simulation program and is shown to be able to predict the order of magnitude of changes due to corner effects and therml bridges.These effects are shown to be non-negligible even in full scale buildings, especially if one isinterested in an accurate prediction of internal surface temperatures.

While advanced models for combined heat and moisture transfer have been available in the community of building scientists within the last two decades, such models have not yet become an item in the toolbox of consultants, building designers or manufacturers of building components. Moisture dimensioning among the practitioners still takes place by rules of thumb or at best by use of the steady state Glaser method or modifications thereof.

A numerical study of turbulent air flow in ventilated multi-room configurations, where both of buoyancy- and radiation-effects are of importance, is described in this paper. Our computer code solves, in finite difference form, the transient-state conservation equations for mass, momentum and thermal energy. The two equation k-e model with buoyancy terms (Boussinesq approximation) is employed for modelling of turbulence. In addition, a two-band model based on Gebhart's method has been implemented enabling the study of the effects of long wave radiation and solar radiation through windows.

This paper presents a new, improved method for designing radiant panel heating systems using accepted thermal comfort criteria, mean radiant temperature, and radiant asymmetry as bases for decision making. Peak design loads are calculated for radiant panel heating systems and convection heating systems in rooms with cold radiative interior spaces. An evaluative comparison of traditional methods and the new design method is also presented here.

This paper describes the objectives of International Energy Agency (IEA) Annex 21 and the ongoing work of Subtask B which deals with how programs should be used for particular applications. Well documented procedures for using programs need to be developed to fulfill a real need by increasing consistency of performance assessment, aiding in training, allowing improvement of procedures and promoting quality assurance. The emphasis in this work is on how programs are applied, so that the programs are taken as 'given'.

The simulation of the transient behaviour of buildings is becoming more important as faster and cheaper computers reach the market. Many simulation programs and specialized tools have been developed to simulate complex situations. With growing problem complexity the simulation programs have to provide more user support and more advanced models. Ibis is usually solved by writing tailored application programs using specialized solution methods and menus or window interfaces. The results are efficient tools for the end user.

Fast accurate micro-computer simulations of the thermal, lighting, and energy performance of buildings offers the promise of informing architects' design decision-making. Yet this promise has only been partially realized, probably because of the mismatch between the way humans and computers communicate information. The full potential of microcomputer design tools depends on finding more effective ways for architects and computers to exchange information in a graphic or visual mode.

This paper discusses recent efforts to develop an intelligent front end (IFE) for a building energy simulation model using a readily available expert system shell. Currently a number of dependable energy simulation models exist for the energy assessment of buildings. However, use of these simulation models involves one problem with respect to the data input process. Usually, detailed building energy simulation models require somewhat rigorous input information from users regardless of the design stage or application domain.