In the indoor air quality (IAQ) assessment of ventilated enclosures it is useful to know therelative influence of key boundary conditions on the personal exposure and ventilationeffectiveness, for instance as a source of information on where to allocate the greatest effortin the design phase. CFD is used to predict ventilation effectiveness and personal exposure tocontaminant sources in a displacement ventilated room subject to variation of several keyboundary conditions.
This paper investigates the pollutant distribution patterns in a ‘negative pressure’ isolation room by means of objective measurement and CFD modelling. The isolation room has two air supply diffusers and two extract grilles mounted in the ceiling. Numero
Cavity wall is often proposed in the building envelope design as a solution for improving the thermal comfort of the inhabitants and reducing the adverse condensation effects on the building fabric. In order to evaluate the thermal effect of ventilated air gaps on building energy demand and comfort, an experimental ventilated cavity wall has been built and tested. The cavity wall separates two ambients at different temperatures that are assumed to be constant over the time required to perform the experimental analysis.
The airtightness of a building envelope impacts upon the magnitude of uncontrolled air leakage and associated ventilation energy losses. A building's airtightness can be assessed using a steady state fan pressurisation technique. This paper describes a study on the largest building in the UK ever to have had its airtightness tested. Power law regression analysis revealed a good correlation between flow rate into the building and observed pressure differentials.
Infiltration has traditionally been assumed to contribute to the energy load of a building by an amount equal to the product of the infiltration flow rate and the enthalpy difference between inside and outside. Some studies have indicated that application of such a simple formula may produce an unreasonably high contribution because of heat recovery within the building envelope. The major objective of this study was to provide an improved prediction of the energy load due to infiltration by introducing a correction factor that multiplies the expression for the conventional load.
The use of natural ventilation systems continues to be a popular feature in low energy, sustainable building design. One feature of natural ventilation is that, depending upon the prevailing climatic or thermal conditions, the airflow through a ventilator can be bi-directional. Aerodynamically, the ventilator, depending upon its construction, may not perform in the same way for the two different flow directions.
Condensation and mold problems have been identified as one of the severest IAQ problems in Japan. Especially in the wintertime, moisture condenses on cold wall surfaces where it can cause deterioration of the building materials and mold growth related to allergic symptoms. This paper discusses the possibility of using the CFD method to solve condensation problems.
Firstly, a CFD model for simulating condensation is developed, and then the validity of this model is examined experimentally.
Air supply diffusers used in air-conditioning systems can be classified as ceiling diffusers, sidewall diffusers, floor diffusers, jet nozzles, and low velocity displacement diffusers. Fixed or adjustable slats are usually used to control airflow directions.
This paper describes a performance-based evolution model using Genetic Algorith as the evolution algorithm and CFD as the evaluation mechanism. The advantages of such an evolutionary performance-based design approach is that diverse instances of the state space can be investigated in relation to specific goal requirements that will enhance the possibility of discovering a variety of potential solutions. The model allows the user to explore and visualize the design evolution and its form generation in an attempt to stimulate the designer creativity that might contribute to their output.
The aim of the study is to validate CFD approaches for the simulation of the dispersion of gases and vapors in an enclosed space at different flow rates, and to show the impact of one important determinant of simulation accuracy.CFD results and measurements were compared, showing a good correspondance for the pollutant concentration when the boundary condition was a profiled velocity inlet and not an uniform velocity inlet.