Full-scale Test Chamber Research Articles

Numerical evaluation of contaminants mixing uniformity in a full-scale test chamber with mixing fan

Most existing models and standards for volatile organic compounds emission assume that contaminants are uniform in the testing devices. In this study, a three-dimensional transient numerical model was proposed to simulate the mass transport process based on a full-scale test chamber with a mixing fan, and the airflow field and contaminants concentration distribution were obtained within the chamber under airtight and ventilated conditions. The model was validated by comparing the numerical results with experimental data. The numerical results show that the contaminant source position and the airflow field characteristics have significant impact on the contaminant mixing, and the fan rotation has an important role in accelerating mixing. In the initial mixing stage, the concentration distribution is obviously uneven; as the mixing progresses, it gradually reaches acceptable uniformity except for some sensitive regions, such as high concentration region at the injection point of the contaminants and low concentration region at the air inlet. To ensure test accuracy, the monitor should avoid above sensitive regions; and some special regions are recommended where contaminant concentration uniformity can be reached sooner. The ventilated chamber results indicate that the mixture of contaminants in the chamber is actually better than the results shown by conventional test method.

Comfort IAQ – a new tool to simulate the indoor particulate matter pollution in relation to the chosen supply air filter quality

Many factors are rather well known for their ability to create a good indoor air climate, but when it comes to airborne particles, there is no great deal of documentation to consult and set requirements. Nor are there much of other specific guidelines. The new, product-neutral and free online calculation tool Comfort IAQ helps to understand the mechanisms behind IAQ and gives a good indication on what would be the impact on indoor air quality (IAQ) due to air exchange, outdoor air environment, air filter selection and building envelope characteristics. Comfort IAQ allows to simulate the concentrations of Particulate Matter (PM1, PM2.5, PM10) in a specific ventilated room, depending on the chosen supply air filter quality. To model the room and the supply air conditions in a realistic way, Comfort IAQ allows to define besides outdoor air conditions (ODA) also the room dimensions, the air changes, the recirculation air rate as well as the supply air filter quality (based on ISO 16890, EN779 or ASHRAE 52.2). Based on these values, the Comfort IAQ tool provides an estimation of the indoor particle concentration and gives engineers and planers a good tool to optimize the Indoor Air Quality, by choosing the best combinations of supply air filter qualities and ventilation rates for a specific application. The algorithms in the online tool Comfort IAQ have been developed by Lars Ekberg, (Docent-installallationsteknik, Chalmers Tekniska Högskola) and the accuracy of the calculations was verified by comparing them with measurements in a full-scale test chamber.

Reducing Losses from Wind-Related Natural Perils: Research at the IBHS Research Center

The capabilities of the IBHS Research Center full-scale test chamber are described in detail. This research facility allows complete full-scale structures to be tested. Testing at full-scale allows vulnerabilities of structures to be evaluated with fewer assumptions than was previously possible. Testing buildings under realistic elevated wind speeds has the potential to isolate important factors that influence the performance of components, potentially allowing for modifications to standard testing procedures that are commonly used to evaluate product performance. IBHS’s wind-related research is discussed, along with research examining natural perils that are highly affected by wind flows around a structure, such as wind-driven rain during high-wind events and firebrand exposures during wildfires. In addition, IBHS’ hail testing capabilities are described in detail.

Combined air heating and ventilation increases risk of personal exposure to airborne pollutants released at the floor level

Combined air heating and ventilation systems are often used in low energy buildings. However, operating these systems in the heating mode increases vertical air temperature gradient in rooms and can have negative effect on indoor air quality. The effectiveness of ventilation and personal exposure of the occupants to airborne pollutants generated at the floor level in rooms with the combined air heating and mixing ventilation was analyzed in this paper. The dispersion of pollutants was evaluated under three air distribution methods (in-ceiling four-way and one-way air supply, and high level wall grille air supply) and under three air change rates (1, 2, and 3ach). Each of these cases were tested at the supply air temperature of +20°C and +25°C by performing CFD simulations and experiments in the full-scale test chamber. The results of the experiments showed higher inhaled concentration of the contaminants under the heating mode. The inhaled-to-ambient pollutant concentration ratio varied in the range of 1.05–1.41 under the ventilation mode and it rose up to 1.14–1.78 under combined air heating and ventilation mode. CFD predictions confirmed that pollutants generated at the floor level are entrained into convective boundary layer of the occupant in cases when vertical air temperature gradient was present. The personal exposure to pollutants released at the floor level can increase significantly when a HVAC system runs in the combined air heating and ventilation mode; this effect will not necessarily dissolve with the increase of the air change rate.

Characterization of indoor aerosol temporal variations for the real-time management of indoor air quality

The study presents the characterization of dynamic patterns of indoor particulate matter (PM) during various pollution episodes for real-time IAQ management. The variation of PM concentrations was assessed for 20 indoor activities, including cooking related sources, other thermal sources, personal care and household products. The pollution episodes were modelled in full-scale test chamber representing a standard usual living room with the forced ventilation of 0.5 h−1. In most of the pollution episodes, the maximum concentration of particles in exhaust air was reached within a few minutes. The most rapid increase in particle concentration was during thermal source episodes such as candle, cigarette, incense stick burning and cooking related sources, while the slowest decay of concentrations was associated with sources, emitting ultrafine particle precursors, such as furniture polisher spraying, floor wet mopping with detergent etc. Placement of the particle sensors in the ventilation exhaust vs. in the centre of the ceiling yielded comparable results for both measured maximum concentrations and temporal variations, indicating that both locations were suitable for the placement of sensors for the management of IAQ. The obtained data provides information that may be utilized considering measurements of aerosol particles as indicators for the real-time management of IAQ.

The impact of the air distribution method in ventilated rooms on the aerosol particle dispersion and removal: The experimental approach

The ventilation strategy, air distribution method and air change rate may affect building energy consumption significantly. However, this strategy is also related to contaminant dispersion, its removal efficiency and the risk of cross-infection in buildings. In this study, the effects of air distribution methods on aerosol particle behaviour in a ventilated room have been experimentally tested. Experiments were conducted in a full-scale test chamber with the source of contaminant (a nebulised solution of sodium chloride) positioned at the air supply and air exhaust sides. Displacement ventilation and mixing ventilation with one-way and four-way air supply through ceiling diffusers were tested at 1, 2, 3 and 4 air changes per hour. The concentration of particles was monitored within 10min after the injection using six optical particle counters located in one plane section of the room. Aerosol particle decay was used for calculating the age of the air and analysing the ventilation efficiency. Computational fluid dynamics (CFD) predictions were performed to determine the spatial particle dispersion in the room and were compared to the results of the experiment.Experimental results showed that at lower air change rates, one-way mixing ventilation directed particles towards air exhaust diffusers more efficiently, while four-way mixing ventilation enabled more particles to remain airborne. At higher air exchange rates (3 and 4ach), mixing ventilation with one-way air supply prevented aerosol particle transport to the opposite side of the room. The displacement air distribution appeared to be rather inefficient in the removal of particles from the chamber, which was reflected by the relatively high age of the air (of average 16.7s at 3–4ach) compared to the mixing ventilation (of average 9.9s at 3–4ach).

Experimental investigation of the velocity distribution of the attached plane jet after impingement with the corner in a high room

Supplying air into rooms properly without causing a sensation of draught is a challenging task. Airflow patterns and the air velocity of attached plane jets should be predicted and designed accurately before the airflow enters an occupied zone in different applications. The objective of this study is to identify the airflow patterns of attached plane jets and set up an efficient model to predict the maximum jet velocity decay of an attached plane jet after its impingement with the corner in a high room. A full-scale test chamber was used to measure the jet velocity with a plane jet supply device. The attached plane jet is bounded initially by the ceiling and the insulated wall after being discharged from the jet slot. Three velocities from the slot, 0.5, 1.0, and 2.0 m/s, are used as the initial jet velocities with three Reynolds numbers, 1000, 2000, and 4000, respectively. The results show that the behaviours of the attached plane jet differ from earlier studies carried out in a relatively low room. The virtual origin model setup in this study can be used to predict the maximum jet velocity decay for jet flow design with impingement in the corners of rooms.

Deposition of Fine and Ultrafine Particles on Indoor Surface Materials

The aim of this study was the experimental determination of particle deposition for both different particle size fractions and different indoor surface materials. The selected surface materials were glass, gypsum board, carpet, and curtain. These materials were tested vertically in a full-scale test chamber. Experiments took place in a 32 m3 chamber with walls and ceiling made of glass. Prior to each experiment the chamber was flushed with outdoor air to reach an initial particle concentration typical of indoor air in buildings with natural ventilation. The decay of particle concentrations was monitored. Seven particle size fractions were studied. These comprised ultrafine and fine particles. Deposition was higher on carpet and curtain than on glass and gypsum board. Particles ranging from 0.3 to 0.5μm had the lowest deposition. This fraction also has the highest penetration into buildings and its indoor concentration is expected to be closest to outdoor concentrations.

Effect of ventilation pattern on room air and contaminant distribution

The ventilation efficiency of different ventilation patterns arranged by two inlet and two outlet diffusers at different locations is investigated. The numerical simulation was first adopted to predict airflow pattern and ventilation performance. Then, a laboratory experiment at room air and contaminant distribution in a full-scale test chamber was conducted to validate the simulation results. Applied the tracer-gas techniques to the experimental program, a concentration decay of CO 2 is used to calculate the ventilation efficiency and air change rate of the test chamber. The distribution of supply/exhaust air in the study characterized by ventilation efficiency, was investigated in isothermal conditions using different supply air velocities. The results indicate that the ventilation efficiency might be dominantly influenced by location of diffuser rather than air change rate.

Comparing Turbulence Models for Buoyant Plume and Displacement Ventilation Simulation

Computational fluid dynamics may be used to predict the details of airflow in rooms served by displacement ventilation systems, provided a suitable turbu lence model can be found. Since buoyant plumes are central to the displace ment ventilation strategy, four turbulence models - three eddy-viscosity mod els (the 'standard' k-ε model, a modified k-ε model, and an RNG k-ε model) and the Reynolds stress model - were applied to simulate airflow in a turbu lent buoyant plume. Corresponding experimental data from the literature were used for validation, although for a plume stronger than expected in rooms as no reliable plume data for room air flow were found. The Reynolds stress model predicted velocity, temperature, and turbulence quantities satis factorily while the eddy-viscosity models performed poorly. The eddy-viscosi ty models were then applied to predict airflow in a furnished room with dis placement ventilation. The computed airflow patterns, mean velocities, tem peratures, and contaminant concentrations agree reasonably well with the experimental data obtained from a full-scale test chamber, but the discrepan cies in some locations were large.

軸流型吹き出し口を用いた床吹き出し空調システムの室内温度分布特性 : 床吹き出し空調システムに関する研究 第1報

Space air temperature profile when cooled air was discharged from floor-mounted outlet was quantified through a number of experiments in a full-scale test chamber. Nozzle-type outlet was discussed as the first trial in the present paper. Space air temperature distribution was measured under steady-state in detail. The vertical temperature gradient of the room could be related to the throw of the cold air jet. Thus, uniform temperature distribution was formed in the region of approximately a half height of the throw. A simplified calculation model of the vertical temperature profile was also developed. It was suggested that, room space was divided into the completely mixing region and the piston flow region. The depth of the former zone was identified based on experimental results.