modelling

Looked at seven residential buildings in northern England to analyse the causes of short-term variations in particle number concentrations. High short-term peak concentrations arose from cooking, smoking and physical activity. The loss rate of particles after emissions stopped depended on the particle size range. The relative importance of deposition and air exchange in particle loss rates were quantified by simultaneous measurement of particle number concentration and air exchange rate.

Describes a simple design tool called the 'office building module' (OPTI), which is intended to help building professionals to incorporate the impact of design choices on energy consumption when designing a project. Emphasises the importance of the program's user-friendliness, minimisation of data and speed. Dynamic thermal programs are needed to compute energy needs and estimate overheating. Current programs suffer from slowness and the need for large amounts of data.

Evaluates by measurement and computational fluid dynamic (CFD) modelling, the thermal performance of an atrium integrated with photovoltaic (PV) modules, situated at the Jubilee Campus of the UK University of Nottingham. The project monitored the internal and external environments of the atrium, and applied CFD to the prediction of its thermal performance. Investigated the effect of ventilation strategies on the performance of PV arrays. Found that CFD modelling showed that for effective cooling of roof mounted PV arrays, the air inlet should be situated close to the roof.

Describes a research and development project that has been started in order to generate design guidelines for PER walls. The three tasks covered are computer modelling, experimental evaluation and development of design guidelines. Describes the results of the experimental evaluation of an exterior insulation finish system. The systems were evaluated for air leakage characteristics, pressure equalization response and water penetration. Concludes that a wall designed to PER principles is more able to resist rain penetration.

Presents a simplified CFD interface (SCI) intended to allow architects and building engineers to use CFD with little training. It can be easily integrated into new CFD programs.

European project pr EN13465 from CEN TC 156/WG2/AH4 gives a monozone model for airflow calculations in dwellings. In order to apply it to natural ventilation systems with adjacent ducts used in dwellings in France, we need to address several issues. First, in adjacent ducts, airflows at each level depend on pressions in the different dwellings. We have to solve by iteration the balanced equation proposed in AH4. Then, cowls and roof outlet performances as well as the wind-pressure coefficient on the roof must be known.

Earth-air heat exchangers can be used to reduce energy consumption in building ventilation systems. The idea is to pre-heat air in winter and pre-cool air in summer using the thermal capacity of the soil. To do this concrete and plastic tubes are put underground, through which the ventilation air is drawn. In this paper a 3D unstructured finite volume model is derived, which allows evaluating the earth-air heat exchanger. The model solves conduction through the soil and the convection from air to the tube wall.

One exposure pathway which has a significant influence on the outcome of a site specific risk assessment when volatile contaminants compounds are involved, is the leakage of contaminated subsurface gases into the indoor air environment. Evaluation of this pathway largely is completed with the use of mathematical models. The current level of understanding is that both convective and diffusive contaminant transport processes in the soil and across the subsurface building envelope will contribute to degraded indoor air quality.

Describes how a nodal model was developed intended to represent room heat transfer in displacement ventilation and chilled ceiling systems. Precalculated air flow rates were used to predict the air temperature distribution and the division of the cooling load between the ventilation air and the chilled ceiling. A network of ten air nodes is used to separately represent the air movements in the plumes and the rest of the room. Calculation of the capacity rate parameters is done by solving the heat and mass balance equations for each node using measured temperatures.

Describes the use of a two-layer model to predict mixed convection. It uses a one-equation model for near-wall region and the standard k-e model for the outer-wall region. In six cases its validation shows good agreement between computed and measured data. The model also reduces computing costs.