In order to clarify whether a combination of designs is optimal, design elements are divided intodesign variables and random variables in the inquiry process for the optimal design. Design variablesrelated to the model are selected by a genetic algorithm, and random variables related to outdoor condition are selected by the moment method. The whole process of optimization consisted of a two-step procedure to reduce the calculation loads for finding the optimal solution. This study carried out a simple analysis using a coarse mesh considering the calculation loads in the first step.
Wind-driven cross-ventilation in a single-zone cubic building with two large openings is investigated using a computational fluid dynamics approach. We analyzed the driving force and the ventilation flow rate due to wind as a function of the relative location and geometry of the two ventilation openings. The aim is to understand how well the conventional simple macroscopic method predicts the ventilation flow rate and when the simple method fails. Parametric studies were completed using building envelope porosity as the primary variable of interest.
This paper investigates the single-sided natural ventilation through a VELUX centre pivot roof window under natural weather conditions. The aim of the investigation is to develop an empirical formulation for air flow rate through a roof window based on CFD and tracer gas decay measurement methods. CFD can separate buoyancy and wind effects in the calculation of the air flow rate through a window opening, but it is difficult to isolate wind effect from buoyancy forces during measurements.
The air exchange in a room with different windows and window geometries is investigated. The aim is to get reliable data for the air change rate and the air exchange efficiency for natural ventilation. Before using a CFD program for the calculations experimental studies have been carried out. In order to meet different demands we distinguish between short time and continuous ventilation. The results are availabe as figures, graphs or approximate equations.
The influence of thermal effects on the dispersion of a gas in a naturally-ventilated room is investigated using CFD in conjunction with measurements. The gas dispersion inside the room, with and without thermal effects, is characterised by a statistical analysis of the CFD-predicted gas concentrations at a large number of points across the room with a view to quantifying the thermal effects. It is concluded that even small temperature differences can lead to significantly different cross flow behaviour and rates of gas concentration decay at the relatively low air change rate considered.
Predicting the performance of natural ventilation is difficult, especially for the large scale naturally ventilated buildings, because of the lack of accurate and efficient prediction tools. This paper presents a strategy, integrating a multi-zone model and computational fluid dynamics (CFD), to improve natural ventilation prediction and design. Large openings and atrium are broadly used in naturally ventilated buildings to promote buoyancy force and optimize air movement. How to properly deal with large openings and atrium is discussed and compared in this 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.
This paper reports the results of room model experiments and Computational Fluid Dynamics(CFD) analysis of ozone distribution in indoor air. The analyzed room model had one supply inlet and one exhaust outlet, with a cavity of dimensions 1.5m (x) 0.3m (y) 1.0m (z) in which a two-dimensional flow field was developed. In order to discuss the order of wall surface deposition for ozone, the concentration distributions of ozone in the model room were measured. CFD analysis corresponding to the experimental conditions and with a built-in ozone wall surface deposition model was carried out.
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.
This article describes CFD simulation results and measurements using a swirl diffuser. Thediffuser is able to provide relatively low velocities within the occupied zone while supplying high airflow rates. The flow pattern produced by the air diffuser was validated by measurements with a flow rate of 133 l/s and 4 C lower temperature than ambient air. Turbulence was modelled using the RNG k- e model with additional swirl modification.
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