This investigation used a validated CFD program to further study the ventilation performance of the TDV and UFAD systems for an office, a classroom, and a workshop of different sizes. Also, the systems with low-height-throw diffusers (all except the linear diffusers) were better. The two systems had higher ventilation performance than the mixing one under cooling mode as well as under heating mode. This study first compared experimentally the TDV with UFAD systems that use four different diffusers (perforated TDV diffusers, swirl diffusers, linear diffusers, and perforated-floor-panel diffusers) in an environmental chamber that can simulate different indoor spaces of the same size. Many previous studies have compared the TDV or UFAD systems with mixing ventilation systems. Traditional displacement ventilation (TDV) and under-floor air distribution (UFAD) systems have been used widely because they create better indoor air quality. With the model, this study developed an airflow calculation method for UFAD as well as a graphical interface for designers.
Linear regression analysis was conducted to correlate the empirical equations of stratification for swirl, square, and linear diffusers. The model used dimensionless numbers to group design parameters in order to represent the two driving factors of thermal stratification, namely, inertial and buoyance forces. This investigation developed the model based on a database summarizing vertical temperature distributions that correspond to various airflow and thermal conditions. This study introduced an empirical model to predict the vertical temperature difference between the head and ankle of occupants and calculated the supply airflow rate for UFAD design. The design parameters, such as airflow rate, temperature of supply air, and types and number of diffusers need to be properly calculated to ensure an acceptable vertical temperature difference between the head and ankle of occupants. Supply airflow rate of Under-floor Air Distribution (UFAD) needs to be carefully determined to achieve thermally comfortable conditions in an occupied space. This paper reports on the continued study of the thermal environment in indoor spaces with under-floor air distribution systems with a focus on the determination of supply airflow rate.
We are designing three different models of swirl diffuser on pro-E software and then analyses its performance experimentally. It is also assumed that changes in thermal energy are significantly greater than changes in potential energy and therefore the latter can usually be neglected for the purpose of analysis. However, the external work transfer is always assumed to be zero. We are designing three different models of swirl diffuser on pro-E software and then analyse its performance experimentally.įrictional effects may sometimes be important, but usually they are neglected.
This study demonstrates the common approaches, identifies the critical design parameters, analyses and discusses the differing outcomes in terms of flow pattern, air distribution.įrictional effects may sometimes be important, but usually they are neglected. Proper calibration and correct definition of performance related parameters are important to affect the radially diffusing flow pattern. The Air Change Effectiveness calculation depends strongly on the flow characteristics produced by the diffuser outlet that vary considerably between different modelling set ups. Swirling vanes are used in air diffusers to create swirling outflow jet, so that more rapid mixing with ambient air can be achieved. Swirl diffusers can create better air mixing to enhance indoor air quality and help achieve compliance through Air Change Effectiveness measure. Diffusers are used to slow the fluid's velocity and to enhance its mixing into the surrounding fluid. An air diffuser is the mechanical device that is designed to control the characteristics of a fluid at the entrance to a thermodynamic open system.