air flow

The paper presents a way of producing an algorithm for the automated construction of mathematical models of air conditioning and ventilating systems with branched air duct networks. The use of mathematical modelling in making aerodynamic calculations of air duct networks allows us to determine the actual value of air flow in network elements. It also permits us to achieve the required air flows effectively in the adjustment of a system.

To simulate non-isothermal indoor airflow more quickly and correctly, a turbulence model is performed in STACH-3, the 3-D CFD code developed by Tsinghua University. Validation reveals that it is satisfied for non-isothermal indoor airflow. The air distribution in an actual conference room with VAV system is numerically solved by CFD method, and the conventional jet theory method is used for a comparison of the results. Subsequently an analysis is done of the cold air draught and hot air climbing problems.

The article presents a zonal model called Sim_Zonal which can be used to predict air movement, temperature distribution and comfort characteristics in a room. The model is based on an approximate partitioning of the room, which is divided into a small number of 'cells', usually in the order of 10 to 100, as compared to 10000 or more for typical CFD calculations. Exchanges are calculated between the cells when mass balance and heat balance equations are applied. Empirical laws describe airflow where plumes or jets occur.

The study forms part of a research project performed by LEPTAB and ATMO Poitou-Charente within PRIMEQUAL program which targets the relation between the indoor and local outdoor pollution. According to many studies, outdoor pollution has a major influence on indoor air quality, airflow being the main factor linking the outdoor environment directly to the climate indoors. A precise regulation of the air flow entering the room is enabled by the mechanical ventilation system and this makes possible the control of the indoor air pollution concentration.

The use of two simplified models was demonstrated in this study, the box and momentum methods, in order to simulate complex diffusers in room airflow modelling by CFD. Additional flow information is needed by the two methods, which is not available from product catalogues of diffuser manufacturers - the information required includes the distribution of discharge air velocity, box size and flow direction. A test method was developed on how to obtain the additional information with minimal effort under ASHRAE standard 70-1991.

Describes a study carried out to validate multizone airflow and contaminant migration simulation programs as they apply to the modelling of tall buildings. Tracer gas experiments were performed in a building on a university campus. A comparison was performed between the measured tracer gas concentrations from these tests and those predicted by a simulation program.

States that inconsistency exists in thermal comfort conditions for local air movement. It is difficult to study, apparently because of the concurrence of the natural convection produced by metabolic heat dissipation of a body and room air movement. Claims that the term local draft sensation can be divided into the physical stimulation of air movement and the physiological perception of a body to analyse such a sensation.

Describes the development of a particle imaging velocimetry (PIV) measurement system for use with full-scale room airflows. Two-dimensional airflows were measured in a full-scale room in order to validate the PIV system, using two typical ventilation schemes: cross-flow ventilation and return flow ventilation. In the former, a slot air inlet and a slot air outlet were positioned on opposite walls so the ventilation air moved across the room air space.

Residential apartments in Hong Kong are usually equipped with up to three window-type air conditioners, placed in living rooms and bedrooms, operated over seven months of hot and humid weather. Analyses the arrangement of room furniture to minimise cold air draughts. The performances were modelled using FLOVENT.

Presents a newly developed supervisory control scheme which adapts to the presence of the faults of outdoor air flow control based on online occupancy detection. It also maintains adequate indoor air quality and minimizes any resulting increase in energy consumption. A strategy, which based on three neural networks of the mixing process of an AHU, is employed to diagnose the measurement faults of outdoor and supply flow sensor, and accomplish the fault tolerant control of outdoor air flow when the fault occurs.