A computational procedure to predict expected rates of natural ventilation for buildings at the design stage is investigated. This procedure integrates three computational methods, namely one to predict temperature induced pressures, another to compute wind generated pressure distributions around buildings, and the third to analyse the networks of resulting air flows in buildings. Experiments show that these methods are valid. The three methods can be used not only for the prediction of natural ventilation, but also for many other environmental engineering applications, e.g.
The objective of this paper is to highlight the range of air infiltration and ventilation models that are available to the designer and to indicate the appropriate level of associated computer hardware that is necessary to support these modelling methods. The description begins with a discussion on simple empirical methods intended for basic design calculations. The applicability of these methods is discussed and some of their shortcomings are highlighted.
In order to obtain means for determining realistic convective heat transfer coefficients, a hierarchy of interacting and interdependent calculation methods have been developed by the authors. Both higher and lower level models have been used to develop and verify an 'intermediate level' computer code, which formed the basis for generating input convective heat transfer data for dynamic building models. The contribution considers the computation of convective heat exchange within three-dimensional, rectangular enclosures when buoyancy effects are significant.
One of the recent major developments to the ESP (Environmental System Performance) building/plant energy simulation package has been the integration of a technique capable of performing dynamic air flow analysis as part of the building thermal analysis, thereby permitting simultaneous dynamic modelling of energy and air flow within the building envelope. This paper briefly describes the model and its data requirements. It compares and discusses differences in zone energy requirements and temperature levels (obtained from ESP) when 1. applying traditional air changes rates and, 2.
A program is presented which runs on Apricot, Sirius and IBM-PC microcomputers and calculates the heating energy requirements of single zone, intermittently heated buildings with reasonable accuracy. Calculation of preheating energy is based on the average internal temperature concept of CIBS Energy Code 2. Solar gains and long-wave radiation losses are treated crudely on the basis of regression equations for radiation as a function of daily average external temperature for different periods of the day.
In this programme of work, methodologies for determining infiltration rates of large and complex buildings have been established. Theoretical considerations suggested that comprehensive information regarding interzonal air movements might be obtained from experimental techniques using multiple tracer gases. Field measurements to determine interzonal flows were carried out in office buildings using automated measurement systems developed for this purpose. Simpler techniques were found to be needed and were developed.
The introduction describes the principle of SVP (Solar Ventilation Pre-heating) and then reviews a number of current related topics. Heat recovery is considered. Work on other devices which produce solar heated air is reviewed. The main driving forces of natural ventilation are wind pressure and thermal buoyancy. One of the problems is that the magnitude of these forces is very variable. The basis of SVP demands a thorough knowledge of airflow through buildings.
The application of heat pumps to ventilation heat recovery in domestic houses is considered. It is shown that the most effective system is a combination of heat pump and heat recovery unit; a plate heat exchanger is the type commonly used. Such units are now commercially available, and can provide heat at a lower cost per kilowatt hour than the Economy 7 tariff. The performance of several units is presented, and seasonal running costs have been computed for a house equivalent to the Capenhurst low energy house design.
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