model

In the Mediterranean countries, where the active solutions of air-conditioning must be avoided, natural ventilation allows improvement of indoor comfort which is generally critical in hot season, and reduction of building cooling loads.A three-dimensional zonal model for calculating temperature fields and airflow distributions insideunconditioned buildings was developed.

In the present communication, a psychometric model has been presented to evaluate the performance of rotary desiccant wheels based on different kind of desiccants e.g. silica gel and LiCl. The developed psychometric model is based on simple correlations between the relative humidity and enthalpy of supply and regeneration air streams. The model is used to predict the performance of three type of desiccant rotors (Type-I, II and III). The model is tested corresponding to a wide range of measurement data.

This paper considers an ideal naturally ventilated building model that allows a theoretical study of the effect of thermal mass associating with the non-linear coupling between the airflow rate and the indoor air temperature.The thermal mass number and the convective heat transfer air change parameter are suggested to account for the effect of thermal mass heat storage and convective heat transfer at the thermal mass surfaces. The new thermal mass number measures the capacity of heat storage, rather than the amount of thermal mass.

A new model has been proposed for evaluating the discharge coefficient and flow angle at an inflow opening for cross-ventilation. This model is based on the fact that the cross-ventilation flow structure in the vicinity of an inflow opening creates dynamic similarity under the condition that the ratio of the cross-ventilation driving pressure to the dynamic pressure of cross flow at the opening is consistent. It was confirmed, from a wind tunnel experiment, that the proposed model can be applied regardless of wind direction and opening position.

Environmental and economic concerns linked to conventional heating, ventilation and air-conditioning systems (HY AC) have sparked a renewed interest in natural ventilation, passive cooling and other low energy microclimate control strategies for buildings. In Canada, the combination of extreme weather conditions, wind variability, transient occupancy patterns and high internal heat gains may hinder the feasibility of implementing natural ventilation as an exclusive means of ventilating non-domestic buildings.

In many buildings, for instance tunnels, underground, parking areas and industrial halls, the L/H is so large that the flow pattern induced by a two dimensional supply air jet along the ceiling can be completely different from that in rooms of normal sizes. Earlier model experiments indicate that, in this case, the supply jet will have a limited penetration length (Ire) because the entrainment generates a backward flow in the lower part of the ventilated space which at a given distance will disperse or deflect the jet.

The aim was to develop a simple dynamic model for predicting air exchange caused by short time single-sided ventilation and necessary window opening time in classrooms. Tracer gas measurements have been made in a full-scale room. The comparison indicates that the model can be used when rough estimates of air exchange are of interest.

The methodology of risk analysis and assessment is reviewed and applied to study the reliability of condensation control measures in lightweight building envelopes. It is generally recognized that airtight construction is an essential part of condensation control. Nowadays, different air barrier systems are developed and documented to prevent air leakage and moisture accumulation in the envelope. But does this mean that the condensation risk is sufficiently minimized and that the protective system is reliable?

The proposed local dynamic similarity model of cross-ventilation predicted ventilation flow rates more accurately than the conventional orifice flow model assuming constant discharge coefficients when discharge coefficients actually decreased with change of wind direction. This model was used to develop a new method for evaluating the ventilation performance of window openings. The obstructive effect of model size on flow fields in a wind tunnel was avoided by installing the opening parallel to the wind tunnel floor.

An overview is given of the current position regarding the use of wind tunnel modelling and envelope flow theory for determining natural ventilation through large openings. The overview is, to a large extent, a personal one and is illustrated primarily by recent research carried out in Nottingham, some of which has yet to be published in full.