English

This paper presents the results of tests on the two-zone airflow pattern that forms in a room with displacement ventilation under conditions of various heat sources and airflow rates. The position of the interface layer between the zones was determined experimentally by tracer gas concentration measurement and by applying a plume model for a point heat source. The following heat sources were used: a plume simulator, a desk lamp, a computer, a round plate and a human body. Quasi-laminar diffusers supplied the air.

Several building simulation programs have been developed for design, analysis and prediction of thedistribution of temperature, airflow and heat transfer between the inside and outside of a building, and/or between different zones of the building. These programs are categorized as mono-zone models (e.g. AIDA and Type 19 of TRNSYS), multi-room models (e.g. HOT2000, DOE, Type 56 of TRNSYS, EnergyPlus, COMIS and CONTAMW), zonal models (e.g. POMA and CWSZ), Computational Fluid Dynamics (CFD) models (e.g. EXACT3, FLUENT, FLOVENT, PHOENICS, and STAR-CD), and multi-zone models (e.g. ESP-r).

Wind-induced cross ventilation is one of the key technologies for saving energy while controlling the indoor environment, and seems to be a crucial element of any sustainable building policy. However, it is sometimes difficult to arrange openings on two sides for cross ventilation of a room. In buildings in built-up areas, many rooms only have openings on a single side.

Chenvidyakarn et al (2004a) investigated the natural ventilation of an occupied open-plan space, which was connected to an exterior through two stacks and a low-level vent. Occupants located at an intermediate level between the stacks and the low-level vent acted as a uniform source of heat, providing buoyancy to drive the ventilation. Their work showed that these conditions could produce up to three steady state ventilation regimes. In the first regime, the bottom opening and the shorter stack acted as inflow vents, while the taller stack acted as an outflow vent.

In this study, the function of carbon dioxide as an index of indoor air quality and as a tracer gas to estimate the air exchange rate in naturally ventilated single family houses was investigated. Carbon dioxide concentrations were measured continuously in the occupied room of six selected Irish houses for periods of 2 to 7 days. The air change rates were then calculated according to the mass balance equation and the time variation of carbon dioxide levels.

A method for estimating the time-varying intensity of emitting sources of a gaseous contaminant inventilated enclosures is proposed in this numerical study. A reduced model linking up a set of control points inside the domain to the contaminant sources is identified using the Modal Identification Method, from simulations carried out using CFD software. This reduced model is then used to solve the inverse forced convection problem consisting of the estimation of sources emission rates as a function of time from simulated contaminant concentration measurements.

The present work contains the details of an investigation of air diffusion and comfort issues of an isolation room of a hospital. Two types of cases have been chosen for a unidirectional ventilation system of the isolation room i.e. for immuno-suppressed patients and infectious patients. The patients body is simulated as a cylinder with approximate values for the physical and thermal properties of a human body and is treated as a constant heat source. The height of the inlet vent was varied and mean residence time and draught rating (DR) were studied.

When the airflow pressure losses at the junctions of ducts in ventilation systems are taken into account, the analysis becomes more complicated since no unique value for the static pressure is associated with a junction. Additional system equations expressing the pressure jumps over the junctions must be written down. A method to replace the junction losses approximately as equivalent channel section losses is presented. The method is based on dissipation considerations. Simpler system equations with fewer unknowns are obtained.

Case studies provide essential evidence about the performance of buildings. They also illustrate the methods by which a technology can be implemented as well as highlighting problems. Various case study buildings (both new and retrofit) that incorporate mixed mode, natural ventilation and low energy cooling are reviewed in this paper. An outline of the tasks that ventilation is required to perform is also presented. The results show that many buildings perform well and can provide good thermal comfort and air quality for much of the occupied period.

The purpose of this research was to assess the performance of air infiltration or naturally driven ventilation, the corresponding energy consumption and indoor contaminant level for residential buildings in Harbin, a typical city in the severe cold region of China. Based on questionnaire surveys and field measurements, a prototypical apartment building was determined. Then, unsteady-state numerical simulations were carried out by the use of COMIS. A parametric study on ventilation performance was undertaken based on applying various air-tightness levels.