This paper presents a set of detailed experimental data of room airflow with displacement ventilation. These data were obtained from a new environmental test facility. The measurements were conducted for three typical room configurations: a small office, a large office with partitions, and a classroom. The distributions of air velocity, air velocity fluctuation, and air temperature were measured by omnidirectional hotsphere anemometers, and contaminant concentrations were measured by tracer gas at 54 points in the rooms. Smoke was used to observe airflow.
This paper describes a methodology for simulating the transport of smoke and hot gases in buildings. The approach is based on the use of efficient CFD techniques and high performance computers to solve a form of the Navier-Stokes equations specialized to the smoke movement problem. The fire is prescribed in a manner consistent with a mixture fraction based approach to combustion, but the combustion phenomena themselves are not simulated. The mixing and transport of smoke and hot gases are calculated directly from an approximate form of the Navier-Stokes equations.
NFPA Standard 92B presents computational methods for determining the position of a smoke layer in a large-volume space. Although NFPA 92B is a guide to smoke management design, the methods have been adopted, with certain modifications, by model building codes and are mandated for use in atriums and large-volume spaces. This paper makes use of a recently developed CFD fire model to assess the NFPA 92B calculation methods. A total of 13 simulated tests were conducted.
This paper presents results of a study where computational fluid dynamics (CFD) was the numerical tool used to analyze the ventilation performance in stations of the Buenos Aires Metro subway system. Both natural and mechanical ventilation options were studied. The study showed that although natural ventilation was sufficient to maintain the temperature criteria, it presented a potential egress problem by letting hot gases leave through the entranceways.
Rapid activation of fire protection systems in response to a growing fire is one of the important factors required to provide for life safety and property protection. Airflow due to the heating, ventilating, and air-conditioning (HVAC) system can significantly modify the flow of smoke along the ceiling and must be taken into consideration when a particular system is designed. At present, the standards used to guide the design of fire protection systems contain very little quantitative information concerning the impact of airflow produced by HVAC systems.
This paper evaluates the performance of traditional displacement ventilation systems for small offices, large offices with partitions, classrooms, and industrial workshops under U.S. thermal and flow boundary conditions, such as a high cooling load. With proper design, displacement ventilation can maintain a thermally comfortable environment that has a low air velocity, a small temperature difference between the head and foot level, and a low percentage of dissatisfied people.
A two dimensional model was developed to predict the infiltration load to a cold room through its doorway. The governing equations were derived and transformed into dimensionless form. The model showed that the infiltration load to a cold room depends on three dimensionless parameters: the Grashof number of the cold room, the aspect ratio of the room (height to width), and the opening ratio (height of doorway to height of the room). 1\ finite difference technique with a control volume approach was used to solve the governing equations.
This paper proposes a new approach to thermostat design. For many years, thermostats have been "dumb" devices, meaning that they react to their environment either by direct user control or by previous user programming. This new approach details an intelligent thermostat that learns about the behavior of the occupants and their environment and controls ambient temperature to maintain comfort according to human specifications. In that way, the thermostat reduces the number of interactions with the user and eliminates the need for them to learn how to program the device.
Video camera calibrations and field tests for air change rates in a test house were performed to develop a new method of measuring air change rates using a video imaging technique. From the camera calibrations, it was found that good correlation was achieved between image signals and luminous reflectance of achromatic color chips by appropriately adjusting the pedestal level of the video camera so that the image signals were made equal to zero for the black level of the picture.