Experiences from cleanroom installations has frequently shown that displacement ventilation has a much higher efficiency than mixing ventilation with respect to particle and CO2 reduction, cooling efficiency etc. Another cleanroom experience is that low particle concentration benefits asthma and allergy sufferer. Low particle concentrations reduces the impact of other pollutants and enhance the quality of life for everybody. In an office, the level of discomfort this means less tiredness, better concentration and lower absenteeism.
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 paper deals with research on capture efficiency of reinforced exhaust system equipped withhorizontal slot exhaust hood, capture efficiency of which is increased by radial flow of supply air through a slot in hood flange. Investigation was carried out with the use of tracer gas method applied in order to measure the capture efficiency of the system, interferometric method in order to visualize tracer gas propagation from different sources, and smoke method in order to make flow patterns at exhaust system visible.
The paper reports on findings from a series of experiments where the supply flow rate wasvaried periodically in time. All experiments were conducted in a small scale model with water as operating fluid. The flow was visualised by adding particles to the water and the streaks were recorded with a digital camera. The main result is that there exist variations that generate a role up of the base flow by generation of vortices that are shed into the stagnant region.
Airflow characteristics in the air-conditioned spaces play an important role to obtain the comfortable and hygienic conditions. This paper utilizes a 3D time dependent Computational Fluid Dynamics (CFD) model to assess the airflow characteristics in four different air-conditioned spaces. It was found that the location of the air extraction port represents a critical design factor and would have a direct effect on the heat removal efficiency and the energy efficiency of the air-conditioning system from the airside wise.
In this paper micro-environment around human body with a personalized ventilation system ina displacement ventilated room was simulated by the standard k-e model. The geometry of thecomputational thermal manikin (CTM) is a real representation of a human body. Detailed analyses of air flow at the facial region and inhaled air quality improvement with personalized ventilation system were carried out with the aid of this complicated CTM.
Task conditioning system is expected to reduce energy consumption in buildings and also toimprove thermal comfort of occupants. In this paper, an isothermal task unit was developed and its impact on subjective feeling was invesigated. Laboratory and field surveys were carried out. The airflow characteristic of the unit and usage of the unit in an actual office are described. Preferred airflow and seating condition of the workers using the unit were observed. Most of the workers preferred the airflow from the unit. Task unit was most effective immediately after a worker took their seat.
A personalized ventilation system combined with a seat is introduced in this paper. This kind ofventilation seat is able to provide occupants with improved air quality, individual control and energysavings. A thermal manikin with an artificial lung was used to investigate several fundamental issues on this novel ventilation system. We tested the performances of the eight different air supply nozzles within the flow rate range from 0.1 l/s to 3.0 l/s. The highest pollutant reduction of inhaled air about 80% is achieved by one nozzle named SCN at the flow rate of 3.0 l/s.
Today, tracer gas is used as a reliable means to examine various queries related to mechanical systems. Prerequisite is the safe and routine handling of the relevant analysis methods. Apart from some basic considerations, the present paper includes results of ventilation efficiency studies and a comparison of different systems on the basis of characteristic parameters.
Methods to measure airflow rates using tracer gas in single air handling units are well known.However, in some buildings, in particular in Singapore, rooms are often ventilated with two ormore units. An adapted methodology that should be used to measure not only the airflow ratesprovided by each unit, but also to determine the inter-units airflow rates and the globalventilation efficiency is presented.
Login