Explicit algebraic equations for calculation of wind and stack driven ventilation were developed by parametrically matching exact solutions to the flow equations for building envelopes. These separate wind and stack effect flow calculation procedures were incorporated in a simple natural ventilation model, AIM-2, with empirical functions for superposition of wind and stack effect and for estimating wind shelter.
States that zero and low wind speed occurrences are often overestimated in standard meteorological data for use by HVAC engineers because of the use of the robust, rotating cup anemometers. Therefore the data would be expected to underestimate wind-driven natural ventilation as well as pollution dispersal. A comparison of rotating cup and ultrasonic anemometers carried out for this study indicated that the former can indicate zero wind speed over many hours in the day when speeds up to 1.5 m/s can be present.
This paper analyses buoyancy-driven natural ventilation assisted or opposed by winds in a building with thermal stratification. Theoretical analysis shows that the ventilation flow is mainly characterised by two air change parameters, namely a buoyancy air change parameter and a wind change parameter, as well as the ventilation openings. It also shows how the clean zone height is affected by ventilation openings. Our new analysis also reveals that the hysteresis behaviour found when uniform temperature distribution is assumed also exists in buildings with thermal stratification.
States that one of the most important parameters for multizone airflow simulation is the wind pressure distribution around a building. Pressure coefficients usually form the input, and the values derives from wind tunnel studies. Alternatives to wind tunnel tests are suggested, namely the use of statistical regression analysis of data obtained from wind tunnel studies. Describes how pressure coefficient values for a shop building were generated using a new wind pressure distribution model based on the regression analysis as well as on wall averaged values from published data.
Describes a three-year EU funded research project into the application of passive downdraught evaporative cooling (PDEC) to non-domestic buildings. This paper specifically discusses the use of computational fluid dynamics (CFD) to model PDEC. Using a hypothetical office building in Seville, Spain, it describes modelling techniques used and applications in an investigation of the building's performance.
A performance evaluation of two passive cooling strategies is presented: daytime ventilation and night cooling, for a six storey apartment building in Beijing and Shanghai, China. A coupled, transient simulation approach is used in order to model heat transfer and air flow. CFD is used to simulate wind-driven ventilation, and Fanger's comfort model is used for occupant thermal comfort. States that the results indicate the superiority of night cooling over daytime ventilation, although there is a high condensation risk. For Shanghai neither were found to be suitable.
The main problem in natural ventilation is that its efficiency depends very tightly on the meteorological conditions : high wind velocity and outside temperature lower than inside are optimal conditions for efficient ventilation. Consequently, air renewal inside buildings is very fluctuating from one moment to another, and extreme comportments can be reached from one season to another : in winter, ventilation is usually very satisfying, whereas in summer unwanted reverse airflows can hardly be avoided.
Passive cooling techniques driven purely by natural wind forces present a highly attractive environmental solution in the perspective of low energy architecture. The physics governing passive cooling are well understood and have been extensively discussed in the literature. Indeed the necessary design details that must be incorporated to achieve the full potential of the technique, such as exposed thermal massive and good internal and solar gain control, are also well understood.
Wind access/protection in cities can be affected by the morphological characteristics of the built environment. Town-planning legislation, building codes and city plan regulations influence those characteristics. Substantial climate-responsive changes of such laws and by-laws as well as simplified environmental performance evaluation tools can contribute to the reduction of mechanical ventilation and air conditioning energy loads through natural ventilation-proned urban design.
Even when the hills have soaked up the rain and the lush green grass is bent flat in the wind, the Great Glasshouse in Wales can still offer a Mediterranean haven. But how do you create and service such an environment?
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