English

Natural ventilation based on Passive-stacks are currently designed without incorporating heat recovery leading to wasteful heat loss. Heat recovery is not used because the pressure loss caused by conventional heat exchangers is large and could cause the ventilation system to fail. This paper presents laboratory investigation and computer simulation of a low pressure-loss heat recovery device for passive stack systems. It was found that the heat recovery effectiveness decreases with increasing stack velocity and heat recovery effectiveness of over 50% has been obtained in the experiments.

A thermal simulation model and suitable weather data were used to generate design curves for the application of night ventilation cooling to office buildings. The work was carried out under the programme of the International Energy Agency (IEA) Annex 28 on 'Low Energy Cooling'. The generated curves show the potential reduction in internal peak day temperatures throughout the cooling season, the free cooling provided by night ventilation and the number of hours that a fan would run during the night for mechanical systems to achieve this free cooling.

This paper describes an innovative experimental technique that accurately reproduces natural ventilation flows, driven by the combined effects of stack and wind, at small scale in laboratory models of rooms or buildings. This technique provides a powerful tool for examining the performance of naturally ventilated buildings at the design stage as it may be used to predict quantitatively ventilation flow rates and temperature stratification under a wide range of climatic conditions.

During the past three years, BRE has conducted winter and summer occupant surveys on satisfaction with environmental conditions in 23 buildings. These were a mixture of naturally ventilated and air conditioned buildings. The results presented in this paper are based on a secondary analysis of 5136 completed questionnaires. The aim of the analysis was to determine the effect of ventilation type and season on occupant satisfaction with key environmental parameters: thermal sensation, thermal comfort, humidity, air movement, stuffiness, air quality, lighting and noise.

For exhaust systems that handle dusts, a minimum transport velocity is required to prevent settling and plugging of ductwork. The minimum transport velocity required was studied experimentally for different kinds of dusts. In the case of horizontal ducts, three different velocities related with the minimum transport velocity were measured: saltation velocity, settling velocity and pick up velocity. The experimental results obtained are shown in different graphs, plotting minimum transport velocities vs. particle size and density.

This paper critically reviews current and previous research into the use of displacement ventilation in commercial offices with and without supplementary static cooling devices. It also reports the findings of a preliminary study of a displacement ventilation technique that may increase the scope of application for displacemelllt ventilation systems without the need for supplementary static cooling.

A method was developed to estimate dust production and deposition rates for a ventilated airspace without a recirculation system under steady-state conditions. The method was derived from a dust mass balance equation and parameter estimation method. The measured variables required for using the method were the dust concentrations and ventilation rates of the ventilated space. The outputs of the method were dust production and deposition rates.