English

This paper studies in three-dimension the coupled convective and radiative heat transfer rate from awindow surface with adjacent venetian blind using a commercial CFD code. For this study the window surface was modeled as an isothermal vertical flat plate. The flow patterns (temperature and velocity fields) and convective heat transfer coefficient were investigated for different blade angles (00, 450, -450, 800). Comparisons were made with experimental and other theoretical research.

One of the main arguments supporting the application of the natural ventilation is the reduction inenergy consumption and capacity of the HVAC system. Here several tests of the building with different systems are carried to quantify the differences in capacities and energy consumptions of different solutions for the HVAC system. The tests were carried with the simulation program built in Simulink. To validate the model the measurements were done in Test cell at TU Delft as well as in the real office building.

It is difficult to evaluate the effect of cross ventilation quantitatively, because the indoor environment under cross ventilation is uneven and changes with the outside conditions. In this paper, the decay process of tracer gas is measured in uneven space under cross ventilation, and the property of spatial unevenness is examined by the concentration decay and velocity distribution.

This paper discusses the concept and performance of a naturally ventilated building with a double-skin facade in Tokyo. The building incorporates a hybrid ventilation system (natural ventilation integrated with air-conditioning systems) that makes use of buoyancy forces generated in a vertical airshaft in the center of the building. Field measurements were made in order to evaluate the performance of the double-skin facade during the summer and winter and also the performance of the hybrid ventilation system during the spring and autumn.

There has been considerable interest in the interaction between buoyancy and wind pressure gradients on the overall structure of natural ventilation flows. Indeed, it has been shown that when wind and buoyancy forces act in opposition, it is possible that for certain wind speeds, multiple steady states may emerge, with a stable wind dominated and a stable buoyancy dominated regime being possible for identical conditions; while at lower wind speeds, the buoyancy dominated flow develops and higher wind speeds, the wind dominated flow develops.

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.

Experiments were carried out to study transition phenomena in buoyancy-induced natural ventilation in a relatively large-scale enclosure equipped with a localized heat source and two openings (upper and lower) on one of the sidewalls. The process studied is transition from the mixing to the displacement ventilation mode realized by opening the lower vent to different heights while keeping the upper vent fully open. Measurements included inside vertical temperature profiles and air velocity through the upper vent.

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.