IJV6

The buildings sector is a major energy consumer as it accounts for almost 40% of the EU’s energy requirements and for about 1/3 of the total energy related CO2 emissions. In 2003, the building sector accounted for almost 60% of the total net electricity consumption in the OECD countries. A large share of the electricity consumption accounts for space cooling which has shown an increasing trend in recent years. It is expected that, in future years, the economic growth of many countries and the increased living standards will boost electricity consumption for space cooling.

Recent work has begun to consider the potential for using freeze flow techniques in Computational Fluid Dynamics programs for carrying out long term simulations of time dependent flows. This paper describes and tests a new, adaptive control method which automatically adjusts the lengths of the frozen and unfrozen flow periods in the solution procedure, based on current and imminent conditions. The adaptive control method demonstrates improved performance compared with an invariable control method.

Established methods of computational fluid dynamics (CFD) have been applied to predict the details of airflow, contaminant dispersal and thermal transport within isolated zones, yet zone transport processes do not occur in isolation. They result from and interact with the bulk airflows from the larger whole-building systems in which they are embedded.

This paper presents steady-state energy and exergy analyses for dwelling ventilation with and without air-to-air heat recovery, and discusses the relative influence of heat and electricity on the exergy demand by ventilation airflows. Energy and exergy analysis results for De Bilt, NL, are presented in terms of heat and electricity use, on an instantaneous and a daily basis. The amount of electricity input to fans and the heat recovery unit (HRU) is much more significant in terms of exergy than of energy, due to the higher exergy value of electricity.

In recent years, the quest has been focused on energy efficient building design. To achieve this in terms of high efficiency air conditioning schemes for hot climate cooling, the combination of variable refrigerant volume (VRV) with variable air volume (VAV) systems have become popular. In this paper, attention is focused on achieving good thermal comfort and indoor air quality (IAQ) combined with energy savings by using multi-zone VAV air conditioning (A/C) that incorporates a genetic based fuzzy logic controller (FLC).

Passive cooling techniques such as night time cross ventilation can potentially provide substantial cooling energy savings in warm climates. The efficiency of night cooling ventilation is determined by three main factors: the external airflow rate in the room, the flow pattern and the thermal mass distribution. The aim of this paper is to analyse the effect of the enclosure shape and the situation of inlet/outlet openings on the total cooling energy stored in the structure.

Localized ventilation systems typically create highly asymmetric or non-isothermal environments around occupants with significant vertical temperature gradient and highly non-uniform airflow regimes that could be directed toward a segment of the body. These effects may have pronounced impact on occupants thermal comfort. The airflow field and temperature distribution near the occupant can be determined either by performing full-scale measurements or by simulation methods. Usually, human subjects or manikins are used in field studies involving measurement techniques.

Knowledge of ventilation rates in dairy buildings is essential for determining indoor air quality and for estimating green house gases and particle emissions. Two new methods for estimating ventilation rates are introduced for situations where air velocities at ventilation inlets and outlets are tedious or impossible to measure. The first method is applicable to buildings whose ventilation can be stopped or closed totally.

Ventilation, cooling and air-conditioning contribute significantly to the energy consumption of many existing office buildings, particularly when primary energy factors are taken into account. Lean building concepts however can diminish this energy consumption by natural ventilation and passive cooling strategies. Compared to fully air-conditioned buildings the resulting indoor temperatures float in a broader band during summer and might exceed the boundaries for thermal comfort for short periods.

In order to provide comfort in a low energy consumption building, it is preferable to use natural ventilation rather than HVAC systems. To achieve this, engineers need tools that predict the heat and mass transfer between the building's interior and exterior. This paper presents a method implemented in some building software, and the results are compared to CFD. The results show that the knowledge model is not sufficiently well described to identify all the physical phenomena and the relationships between them.