air diffusion

This article deals with summer comfort and room air distribution in low-energy housings. In such buildings, the efficient thermal insulation and air tightness make it crucial to efficiently dispose of the heat released by the internal gains. In this prospect, the comfort in a test room resulting from an integrated cooling and ventilation system is assessed both experimentally and numerically. The air is supplied into the room close to the ceiling through a wall-mounted diffuser of complex geometry composed of 12 lobed nozzles.

The methods for estimating or calculating the noise reduction in ductwork are described. Information is given about noise propagation in straight circular or rectangular ducts and in ducts with diameters changes, bends, elbows or junctions. Noise reduction by air diffusers, filters, coils, is also presented, as well as noise emission by ducts walls.

This paper proposes a new mode of ventilation for indoor airflow. Computational results show that with properly designed supplied air velocity and volume, locations of diffusers and exhausts, the proposed system should be able to maintain better thermal comfort with a smaller temperature difference between the head and foot level, and possibly lower energy consumption, if compared with conventional systems. It looks promising that better indoor air quality (IAQ) in the breathing zone could also be achieved but that further work is needed to determine if IAQ benefits are significant.

In this article, four turbulence models are studied to capture the flow and temperature behavior of the air close to a low-velocity diffuser for displacement ventilation. Turbulence is modeled by means of one zero-equation model and three different two-equation models, i.e. the LVEL, the RNG, the Standard k-e, and the Chen-Kim model. They are evaluated for their performance in predicting the air flow patterns and temperature profiles close to the diffuser.

For a long time PPD index defined in international ISO7730 standard has been a practical tool for evaluation of measured thermal comfort conditions in existing buildings. However, its usage has not yet been realized in design phase. One of the reasons is that there has not been any practical tool available to estimate average velocity conditions within the occupied zone. A kinetic energy model for calculation of the average room velocity has been presented in earlier paper. Current paper reports additional verification results of the kinetic energy model with different types of diffusers.

This paper describes the precautions that have to be taken in design and installation of ventilation systems in order to reduce their noise. They concern fans, ducts and ductwork, air inlet and outlet, air diffusers, air handling unit.

Economic and polyvalent, numerical simulation, or computational fluid dynamics (CFD) lends itself to the topic of air diffusion. An overview of this useful modelling strategy.

Indoor air flow induced by a fan-coil unit in an air-conditioned environmental chamber is studied experimentally. The supply Archimedes number which is a macroscopic number describing indoor air flow is measured and related to the
centreline velocity and temperature decay of the cold air jet issued from the fan-coil unit. The space air diffusion and the thermal comfort using respectively the Air Diffusion Performance Index (ADP]) and the Predicted Percentage of  dissatisfied (PPD) are evaluated. Evolution of these indices with the supply Archimedes number is discussed.