AIVC - Air Infiltration and Ventilation Centre

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numerical modelling

Experimental and theoretical analysis of natural ventilation by means of windows opening.

The purpose of this paper is to improve our understanding of the transient behaviour of airing by window opening. While a few simple models exist to analyse the results of window opening, its transient behaviour is not yet well understood, in its effects on air change rates, air temperature and ventilation efficiency. The paper achieves its purpose in the first place by using a synthesis of numerical modelling activity. Then a critical analysis of the methods of calculation is undertaken, comparing both detailed (CFD) analysis results and simplified or zonal models predictions.

Evaluating the thermal performance of active envelopes.

In situ measurements were compared with a numerical model to assess the effectiveness of the model for active envelopes as energy efficient building envelope solutions. There was good agreement for the mechanical flow active envelope, but not for the natural flow variant. States that taking into account the enthalpy change of the cavity air is essential for a correct evaluation of the energy efficiency of active envelopes.

A numerical study of a solar chimney with uniform wall heat flux.

A numerical study was carried out to gain an understanding of the ventilation performance of solar chimneys with uniform heat flux from both walls. Results showed that a currently available predication method, which has been validated with narrow chimneys, may not be suitable for wide chimneys. It was also shown that for geometrically similar chimneys, the ventilation flow rate, Q, increases with the solar radiation intensity, q, and the chimney height, H, and can be well correlated by Q q1/3H4/3 regardless of height/gap ratio and the occurrence of reverse flows.

Air quality appraisal in air conditioned spaces: numerical analysis.

The conditioned air is an important element in healthcare applications. One of the main objectives of supplying conditioned air to healthcare facilities is to create proper comfortable combination of temperature, humidity, and air motion as well as to remove airborne bacterial, microorganisms, and air contaminants. So the air distribution must meet specified conditions of air change rates, velocity, pressure, cleanliness, temperature, humidity, and noise level.

Low energy cooling. Technical synthesis report IEA ECBCS Annex 28.

Covers low energy cooling technologies, the numerical design tools, and case study buildings.

Heat transmission through walls with slotted steel studs.

An insulated wall can be supported internally by thin steel studs. There will be extra heat loss caused by the metal U-studs, but slitting the web of the U-studs perpendicular to the heat flow direction reduces this heat loss. Calculation of the heat transmittance is a difficult numerical problem due to the high ratio of thermal conductivity between the insulation and the steel. This study presents result of calculations in three dimensions. The proper choice of the numerical mesh is discussed. Simplified equations for the U-factor are derived and implemented ill a computer program.

Angle factors between human body and rectangular planes calculated by a numerical model.

Angle factors between a human body and rectangular planes are calculated by a numerical model. The method presented in this paper which predicts the thermal radiation field in a space, is based on a numerical integration method proposed in a previous paper. To confirm the validity of the calculated results, predicted angle factors for both standing and seated persons are compared with those from experiments. It was found that the predicted figures matched well with those from experiments except those between the human body and the front floor.

Characterisation of natural convection in a room communicating with the outside environment through a door.

The present paper describes a numerical method for analysing threedimensional natural convection in rooms connected to the outside through large openings. The calculations made use of a Computational Fluid Dynamics (GDF) procedure which solves the three-dimensional equations for the conservation of mass, momentum and thermal energy taking into account the effects of buoyancy, heat sources, thermal radiation heat transfer and air flow turbulence.