Natural ventilation is a more pleasant and acceptable ventilation mode, which is favorable to human physical and psychological comfort and health. In this research, experiments and analysis on the fluctuant characteristics of natural wind in outdoor environment and in different positions of indoor area are conducted. The authors analyze the physical structure of airflow fluctuations with turbulence statistical theory, chaos and fractal theory. The fluctuant characteristics of the natural wind in different built environment are found and generalized in the paper.
As part of an investigation into single-sided natural ventilation, a computational fluid dynamics study was performed to analyse the impact on the airflow rate of the dimensions and position of a large rectangular opening and of the temperature difference between inside and outside air. An empty room with a rectangu-lar opening in the external wall was assumed and the Bernoulli formula used to calculate discharge coefficients Cd. The vertical position of the opening was found to have the greatest impact on the discharge coefficient.
The fluctuating characteristics of airflow have impacts on the thermal comfort of people. Two kinds of mechanical airflows in indoor environment were tested and analyzed in the paper. Spectrum analysis, chaos analysis were used to study the rule of the fluctuating characteristics shifting of the mechanical airflows. The results show that the fluctuating characteristics of different kinds of mechanical winds are different. It is also found that the characteristic parameters of the mechanical airflow, such as power spectrum etc.
We describe the flow in an underfloor plenum. We show that the geometry of the plenum causes the flow to exhibit two-dimensional dynamics and to develop flow patterns that are determined by the inlets of the underfloor into the plenum void. We describe laboratory experiments that simulate these flows and also show that the location and number of diffusers in the plenum has little effect on the underfloor flow. Depending on the location of the inlets to the plenum, the flow can exhibit complex vortex patterns and may be time dependent.
Floor-supply air-conditioning system with Coanda effect is introduced to a theater hall. This system supplies air from floor diffusers set beneath the seat backrest in front of occupants. Supplied air moves upward along the backrest board inducing the circumambient air resulted in airflow temperature difference reduction. Thermal environment was measured under various heat load conditions in the theater hall. Supply air flow along and radiation effect from the seat backrest in front were confirmed using the floor-supply system.
A comprehensive modelling of a compact double skin facade equipped with a venetian blind is proposed here. The modelling is done using CFD approach to asses the air movement inside the ventilated facade channel and appropriate radiation model for long and short wave exchanges. The impact of solar radiation on temperature and velocity fields as a function of some parameters such as beam radiation incidence angle, blade angle of solar protection, etc. is analysed.
This paper presents an analytical model for predicting the air flow and velocity in an open vertical air channel due to natural convection. It can be used in the study of ventilated windows and double-faade systems, which are arousing interest as an energy-efficient means of providing fresh air, daylight and solar radiation to rooms. Unlike most previous work in this field, it proceeds from known surface temperatures instead of known surface heat flux.
We present in this paper an advanced formulation of zonal models for calculating room airtemperature and airflow distributions. It is based on a new way of sub-dividing the room usings the Octree method. It allows us to obtain a partitioning based on airflow patterns. The behaviour of the room is represented by the connection of SPARK calculation objects according to its partitioning. The SPARKs objects represent sub-zones of the room or interfaces between sub-zones. We developed an automatic generator of zonal models.
This paper presents an exploratory study on flow pattern selection in unmixed flows, resulting in aset of rules that are used to decide between flow regime during and before a simulation. The development of this set of decision rules had several goals: to define simple criteria to distinguish between flows, to assist non-expert users in the selection of the correct flow pattern model and finally to automate the choice of models during numerical simulations in energy simulation software.
The purpose of the present work is to describe the ability of the advanced computer packages(CFD codes) to perform numerical simulations of general refrigeration engineering problems. The case study concerns the modelling of three-dimensional turbulent airflow with thermal buoyant effects and air temperature distribution in the refrigerated compartment of a perishable foodstuff transportation vehicle.The numerical predictions obtained with three commercial codes (PHOENICS, FLUENT and CFX) and an academic one are evaluated and compared with experimental data.
Login