Application of the principle of the balance of mechanical energy gives a constraint on the possible values of the junction coefficients at a duct system junction. In some cases the recorded junction coefficients in the literature do not satisfy this constraint. The values given may then be questionable. The terminology in connection with junctions is discussed and the role of the principle of balance of mechanical energy in duct system flow modelling is considered in some detail.

Investigations were carried out into the airflow in a non-unidirectional airflow cleanroom and its affect on the local airborne particle cleanliness. The main influence was the method of air supply. A supply inlet with no diffuser gave a pronounced downward jet flow and low levels of contamination below it, but poorer than average conditions in much of the rest of the room. A 4-way diffuser gave much better air mixing and a more even airborne particle concentration throughout the cleanroom.

This paper describes the transient ventilation of two interconnected rooms. One of them has a negative buoyancy source located at ceiling level, similar to an overhead split type air-conditioning system with ductless distribution, whereas the other has a vent at floor level. The flow evolution from short- and long-term analytical models was determined and confirmed with scale-model salt bath experiments.

It has been found that, among the tools and methods available for the energy calculation of double envelope elements, there are some debatable aspects such as: the selection of correlations for calculating the convective heat transfer coefficient and the procedure for calculating the temperature of the air layer. In addition, the validation of some models only refers to specific cases or no information is available whether or not a validation has been performed.

The governing equations in duct system flow analyses are nonlinear, and iterative solution methods must be used. A suitable initial flow rate guess may be needed to start the calculations so that a converged solution can be finally achieved. A method to obtain a reasonably accurate initial flow rate guess is presented. In it the duct system is analyzed first in a strongly simplified setting assuming a linear (imaginary laminar) duct flow problem. The continuity equations at the junctions are satisfied.

Aerosol detection in HVAC duct components is a critical component of contaminant detection and analysis. Incorrect placement of a sensor inlet within the ductwork can have a significant, deleterious effect on capture efficiency and sample accuracy. Computational fluid dynamics studies were conducted of straight rectangular cross-section ductwork and a 90° bend to determine flow patterns and simulations of particulate injections were made at various locations across the inlet. The resultant particle distributions were analyzed to determine the optimal placement for a sensor inlet.

There is a need to improve the accuracy of infrared thermography for measuring the temperature distribution of building exterior surfaces. Thermography is useful for building ventilation and thermal analysis, as well as understanding city ventilation and the urban heat island phenomenon. The key in correcting infrared images is to quantify accurately the reflected infrared contribution of surrounding surfaces as well as that of the atmosphere. Two new methods are proposed here for correcting measured temperature distribution of building exterior surfaces by infrared thermography.

Windcatchers are roof mounted devices that use the action of the wind to provide top down natural ventilation to a room. Here, fresh air is channelled into a room while, at the same time, stale air is drawn out. This provides a simple but attractive natural ventilation methodology that is increasing in popularity in U.K. schools. However, an analysis of system performance has largely been limited to laboratory based measurements and the use of CFD to generate predictions.

In this paper, a review is made of the adaptive thermal comfort model. This is then applied and compared with the performance of the conventional thermal comfort model for a school located in a Mediterranean weather environment. Measurement data, combined with a building thermal response numerical model, are used to define the comfort performance under ambient natural ventilation and passive conditions for various classrooms. These results can then be used to identify the locations that require further measures to improve comfort, such as extra passive heat load and shading measures.

Hybrid ventilation represents an interesting option both to guarantee good air quality for indoor environments and to reduce the energy consumption related to the mechanical motivation of the air.