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Flow in the plenum of a UFAD system

We describe the flow in an underfloor plenum. We show that the geometry of the plenum causes the flow to exhibit two-dimensional dynamics and to develop flow patterns that are determined by the inlets of the underfloor into the plenum void. We describe laboratory experiments that simulate these flows and also show that the location and number of diffusers in the plenum has little effect on the underfloor flow. Depending on the location of the inlets to the plenum, the flow can exhibit complex vortex patterns and may be time dependent.

Application of CFD and Data Based Mechanistic (DBM) modelling techniques for a ventilated air space

This paper outlines the extension of a CFD model using DBM modelling approach. Primarily adynamic CFD model is proposed for adiabatic ventilation system. At the inlet a step rise in temperature of the incoming air with steady flow rate is used for the CFD simulation and temperature responses at 36 monitoring locations were extracted. In the second stage, the inlet and the extracted temperature profiles were used to develop DBM models at individual locations. Finally the developed compact DBM model was used to construct model based predictive control algorithm.

Indoor air quality and thermal comfort studies in the tropics: a comparison between under-floor supply and ceiling-based mixing ventilation systems using female subjects

An experimental study was conducted in a field environmental chamber with the aim of comparingceiling-based mixing ventilation (MV) system and under-floor supply system (UF) from the perspectives of indoor air quality and thermal comfort. Six tropically acclimatized female subjects participated in the experiments and they were required to complete a set of questionnaire pertaining to IAQ and thermal sensation every 20 minutes during each exposure of 2 hours.

CFD analysis of two different supply diffusers in underfloor air distribution systems

For underfloor air distribution (UFAD) systems, more rapid mixing of the supply air with ambient airis desirable for better thermal comfort, and swirling air diffusers are usually used. In order to rigorously simulate the flow characteristics of such diffusers, we used the multi-grid technique and validated it with experimental results. In this paper, the technique is used to compare the square diffuser and the swirling diffuser.

An Extended Model for Underfloor Air Distribution Systems

Previous work on an Underfloor Air Distribution (UFAD) system with a single heat source anda single cooling diffuser at floor level developed by Lin has been extended to study the effects of the vertical location of the heat source and of multiple cooling diffusers. This is an attempt to produce more realistic models of UFAD systems. Both experimental and theoretical modeling is described in this paper. In the experiments, a plume and fountains represent a heat source and cooling diffusers respectively.

The compared cost-to-quality analysis of the mechanical ventilation systems

The research was oriented to analyze better the ventilation systems, in terms of cost-to-quality ratio. The matter of the paper is that a ventilation system is designed to work in certain quality conditions, but every quality has its cost. This cost comprises investment, energy consumption and operation-maintenance expenditures.

Critical analysis of contaminant removal efficiency assessment in a ventilated room

This study presents a critical analysis of assessment of ventilation systems effectiveness in terms of contaminant removal. For this purpose, experimental measurements are carried in a room of an experimental house called MARIA. Various ventilation scenarios are handled. The ventilated room is also equipped with a pine wood floor which emits several Volatile Organic Compounds which are considered as air pollutants here. Thereafter, based on boundary conditions given by measurements, Computational Fluid Dynamics (CFD) simulations are performed.

Distribution of Contaminants in the Occupied Zone of a Room with Personalized and Displacement Ventilation

A distribution of contaminants from floor covering, exhaled air and human bioeffluents was examined in a mock-up of a typical two-person office by means of tracer-gases. The distribution was studied with two types of air terminal device for personalized ventilation combined with displacement ventilation. The results show that the type of personalized ventilation and its use affects the distribution of contaminants to a great extent, as does the type and location of contaminant sources.

Transmission of Exhaled Air between Occupants in Rooms with Personalized and Underfloor Ventilation

Air exhaled by occupants may carry infectious agents and be one way of transmitting respiratory diseases in rooms. The exposure of occupants to exhaled air was examined at two different throw heights of underfloor ventilation combined with two types of personalized ventilation by means of full-scale experiments. The concentration of exhaled air from one occupant was measured in air inhaled by another occupant who used or did not use personalized ventilation.

Experimental study of ventilation performance and contaminant distribution of underfloor ventilation systems vs. traditional ceiling-based ventilation system

This study shows the possiblity of improving indoor air quality thanks to underfloor ventilation systems. The top-return configuration and the floor-return one are tested and compared to a traditional ceililng based mixing system.

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