air flow

Knowledge of the authority of control dampers in HVAC systems may be used for diagnostic purposes or to enhance control performance. In this paper, a method of estimating damper authority in air distribution systems is described. The method only requires measurements that are normally available in modem HV AC systems with digital controls. The method is based on a technique that allows the static pressure drop across a branch to be regulated even if that pressure is not measured. Experimental results on a Variable Air Volume (VA V) air handling unit demonstrate the efficacy of the method.

At present, numerical simulation of room airflows is mainly conducted by either the Computational-Fluid-Dynamics (CFD) method or various zonal/network models. The CFD approach needs a large capacity of computer and a skillful expert. The results obtained with zonal/network models have great uncertainties. This paper proposes a new simplified method to simulate three-dimensional distributions of air velocity, temperature, and contan-finant concentrations in rooms. The method assumes turbulent viscosity to be a function of length-scale and local mean velocity.

A field study investigated outside air delivery and thermal comfort in a normally operating variable-air-volume (VA V) system. In addition to finding that outside air delivery and thermal comfort are generally acceptable under a variety of operating conditions, a number of practical diagnostic techniques were used to more fully understand VA V system operation and design. It was concluded that unless a VAV system is well understood or continuously monitored, the likelihood of unexpected system behavior that can impact the outside air delivery and thermal comfort is high.

New office buildings in Spain are nearly always designed to be air conditioned. The architect Emilio Miguel Mitre Associates (EMMA) has designed a building which avoids air conditioning, thereby reducing energy demand. The design uses the principles of high thermal mass combined with night ventilation, reduction of solar gain during the summer months, high levels of insulation, evaporative cooling, and buried pipes to provide cooling when the external temperature rises above 30°C.

Increasing demands for energy saving and a higher degree of comfort in rooms compels designers or architects to use more sophisticated analysis methods. The measurement in situ, numerical simulation (CFO), and wind tunnel investigations are three of methods which are always utilised to analyse or to assess air flow in rooms and their environment. However, these methods remain generally very difficult for the majority of the designers or the architects.

The LCA methodology [SETAC] is applied to buildings. The system limits, functional units and allocation principles are explained. Inventories have been established for 150 buildings materials and linked to the ECOINVENT database. Buildings are described on the basis of specifications which are aggregated to (cost planning)-elements. There is a catalogue of several hundred elements. Energy needs, costs and environmental impact are calculated simultaneously. Different views are possible (type of Impact. life time phase, element).

This paper presents an analysis of different possibilities of representing mass transfers in zonal models. In this aim, formulations derived from the Navier-Stokes equations or from Euler's theorem are obtained. The models which result from them and empirical models are compared so that to define the best compromise between simplicity, accuracy and easy convergence.

Air flow through doors, windows and other large openings constitutes a major factor inbuilding ventilation. However, due to the complexity of the physical processes involved,relevant physical phenomena are not yet fully understood.The paper presents data obtained from five consecutive experiments concerning air flowthrough a large opening (door) connecting two rooms (volumes 28.3 m and 38.1 mrespectively) with different air temperatures.

Within the EU project NATVENT, which deals with the application of natural ventilation in office type buildings, one of the items to be studied was controlled air flow inlets. Natural air supply is a key part in the design of natural ventilation in offices. In cases these air supplies are designed in the wrong way one may expect complaints in terms of draft and stuffiness. Size and controls on inlets are vital elements in design. Controlled air inlets may help to overcome the problems of draft and stuffiness, and may contribute to an energy efficient design of the building.