Full-scale Chamber Research Articles

Novel MOF-based autonomous humidity control materials for energy-efficient indoor moisture regulation

The concept of autonomous humidity control material (AHCM) is inspired by phase change material. AHCM is a new type of functional sorbent material. It can adsorb/release sufficient water vapor at the target relative humidity level and autonomously maintain the indoor relative humidity at a set value/range without external intervention, which cannot be achieved by conventional sorbents (e.g., zeolite, silica gel, etc.). In this study, a novel metal-organic framework (MOF) based AHCM is prepared, and its application for energy-efficient indoor moisture control has been investigated. The new MOF-AHCM has an S-shaped water vapor isotherm, large porosity, and high moisture adsorption capacity. The trigger points for adsorption and desorption occur at 60 % and 40 % RH, respectively. It means MOF-AHCM can autonomously regulate the indoor relative humidity to fall within 40%–60 % RH, which fits the thermal comfort range recommended by ASHRAE well. The physicochemical and hygrothermal characteristics of the synthesized MOF-ACHM have been assessed. Full-scale chamber tests were carried out to verify the humidity control ability of the new material. The experimental results show that MOF-AHCM can significantly mitigate indoor humidity fluctuation and regulate the humidity level within the target range autonomously. Furthermore, numerical simulation has been performed to investigate the impact of MOF-AHCM on building energy consumption in different moisture regions globally, namely, arid, semiarid, dry, moist, and wet areas. The results reveal that MOF-AHCM has an excellent humidity control capacity and can reduce the latent cooling demand of HVAC systems in most climates, especially in arid, semiarid, dry, and moist areas.

Far-UVC disinfection of airborne and surface virus in indoor environments: Laboratory experiments and numerical simulations

Numerical models have been used to predict the efficacy of ultraviolet (UV) lamps in disinfecting indoor bioaerosols. However, detailed experimental data on both air and surface viral inactivation for model validation are lacking. This study aimed to experimentally validate a computational fluid dynamics (CFD)-Lagrangian model for disinfection of airborne and surface viruses with far-UVC light. The susceptibility constants (Z-value) of MS2 virus in the air and on surfaces irradiated by 222 nm far-UVC light were measured. The UVC irradiance distribution, the airborne MS2 concentrations as a function of time, and the surface MS2 count in a full-scale chamber with a 222 nm far-UVC lamp were also measured. The comparison between simulation and experiments showed that the numerical model can predict the inactivation of airborne and surface viruses reasonably well. The validated numerical model was then used to calculate the disinfection of airborne and deposited SARS-CoV-2 in a dental clinic and a shared office. It was found that far-UVC lamps can effectively inactivate airborne and surface SARS-CoV-2 simultaneously in both the clinic and the office. The experimental results can be used as a benchmark for model validation, and the case studies can improve our understanding of far-UVC disinfection in real-life indoor environments.

Experimental study of the disinfection performance of a 222-nm Far-UVC upper-room system on airborne microorganisms in a full-scale chamber

222-nm Far-UVC light is an emerging and promising tool for rapidly inactivating airborne pathogens. In this study, we experimentally evaluated the performance of a 222-nm Far-UVC upper-room disinfection system with a 15 W Far-UVC lamp in a full-scale chamber (11.9 m3). One gram-positive bacteria, namely Staphylococcus epidermidis and two gram-negative bacteria, namely Escherichia coli and Salmonella enterica were selected for the experiments. The aerosolized bacteria were injected into the chamber and exposed to 222-nm Far-UVC light. The first-order decay rates of indoor bioaerosols concentration with and without Far-UVC treatment were estimated. According to the results, the 222-nm Far-UVC induced decay rates of three bacteria were 0.0611 ± 0.003, 0.409 ± 0.048, and 0.474 ± 0.015 min−1, respectively. Besides, the UV susceptibility constants (Z-values) of these three bacteria were estimated as 0.157, 0.974, and 1.18 m2/J, respectively. The gram-positive bacteria, S. epidermidis, showed higher resistance to Far-UVC light as compared to the gram-negative bacteria, E. coli and S. enterica. In addition, a case study on airborne SARS-CoV-2 indoor transmission was simulated, and the infection risk of SARS-CoV-2 was compared using the Far-UVC and enhanced ventilation approaches. The results showed that both UV inactivation and ventilation approaches can significantly reduce the infection risk. More importantly, the Far-UVC may be a feasible and sustainable solution for reducing infection risk and improving indoor air quality.

Experimental study on the control effects of different strategies on particle transportation in a conference room: Mechanical ventilation, baffle, portable air cleaner, and desk air cleaner

To control the spread and transmission of airborne particles (especially SARS-CoV-2 coronavirus, recently) in the indoor environment, many control strategies have been employed. Comparisons of these strategies enable a reasonable choice for indoor environment control and cost-effectiveness. In this study, a series of experiments were conducted in a full-scale chamber to simulate a conference room. The control effects of four different strategies (a ventilation system (320 m3/h) with and without a baffle, a specific type of portable air cleaner (400 m3/h) and a specific type of desk air cleaner (DAC, 160 m3/h)) on the transportation of particles of different sizes were studied. In addition, the effects of coupling the ventilation strategies with five forms of indoor airflow organization (side supply and side or ceiling return, ceiling supply and ceiling or side return, floor supply and ceiling return) were evaluated. The cumulative exposure level (CEL) and infection probability were selected as evaluation indexes. The experimental results showed that among the four strategies, the best particle control effect was achieved by the PAC. The reduction in CEL for particles in the overall size range was 22.1% under the ventilation system without a baffle, 34.3% under the ventilation system with a baffle, 46.4% with the PAC, and 10.1% with the DAC. The average infection probabilities under the four control strategies were 11.3–11.8%, 11.1–11.8%, 9.1–9.5%, and 18.2–19.7%, respectively. Among the five different forms of airflow organization, the floor supply and ceiling return mode exhibited the best potential ability to remove particles.

Full-scale test of Direct-buried Cable in Sand under Repetitive Loading

Direct-buried cable construction can minimize cumbersome processes, thereby decreasing construction time and cost. However, there is no regulation on burial depth that consider the long-term performance of backfilling soil for direct-buried cables. This study examines the mechanical response of direct-buried cables subjected to repetitive loads. This experimental study uses a full-scale chamber to replicate field construction. The stress on the cable, vertical displacement on the surface, and shear wave velocity between loading plate and cable are continuously monitored during 10,000 repetitive loading cycles. A miniature electrical cone is used to indirectly quantify the initial relative compaction. Repetitive loading densifies the soil around the cable, increasing stress on the cable and accumulating vertical strain. The trends are more pronounced with lower initial relative compaction. The shear wave velocity increases during repetitive loading, suggesting a change in the earth pressure coefficient. Applied stress – vertical strain allows the estimation of resilient modulus. These observations will provide a better understanding of the mechanical response of backfilling soil. Additionally, the uniaxial compression test of the underground power cable made for direct burial is conducted to measure the displacement of the cable insulator under the field condition obtained from the full-scale test. Then mechanical stability of the cable is investigated based on the axial displacement of the cable insulator.

Robustness of ventilation systems in the control of walking-induced indoor fluctuations: Method development and case study.

Walking-induced fluctuations have a significant influence on indoor airflow and pollutant dispersion. This study developed a method to quantify the robustness of ventilation systems in the control of walking-induced fluctuation control. Experiments were conducted in a full-scale chamber with four different kinds of ventilation systems: ceiling supply and side return (CS), ceiling supply and ceiling return (CC), side supply and ceiling return (SC), and side supply and side return (SS). The measured temperature, flow and pollutant field data was (1) denoised by FFT filtering or wavelet transform; (2) fitted by a Gaussian function; (3) feature-extracted for the range and time scale disturbance; and then (4) used to calculate the range scale and time scale robustness for different ventilation systems with dimensionless equations developed in this study. The selection processes for FFT filtering and wavelet transform, FFT filter cut-off frequency, wavelet function, and decomposition layers are also discussed, as well as the threshold for wavelet denoising, which can be adjusted accordingly if the walking frequency or sampling frequency differs from that in other studies. The results show that for the flow and pollutant fields, the use of a ventilation system can increase the range scale robustness by 19.7%–39.4% and 10.0%–38.8%, respectively; and the SS system was 7.0%–25.7% more robust than the other three ventilation systems. However, all four kinds of ventilation systems had a very limited effect in controlling the time scale disturbance.

Evaluation of Reducing NO and SO2 Concentration in Nano SiO2-TiO2 Photocatalytic Concrete Blocks.

The use of titanium dioxide in concrete block pavements is a promising approach to reduce air pollution in the roadside. When TiO2 is used as an additive of cement concrete or mortar, it is not dispersed uniformly due to agglomeration between particles causing the degradation of photocatalytic reaction. To improve the photocatalytic performance of TiO2, the Nano SiO2-TiO2 (NST) has been developed by coating TiO2 with SiO2 as a support using the sol-gel method. The environmental performance of concrete blocks incorporating NST as an additive was evaluated using both laboratory and full-scale chamber experiments. It was observed from laboratory environment chamber testing that the NO reduction efficiency of concrete blocks with 4% NST ranged from 16.5 to 59.1%, depending on the UV intensity. Results of the full-scale chamber test on NST concrete blocks indicated that the NO and SO2 reduction efficiencies were 22.3% and 14.4% at a 564 W/m2 of solar radiation, respectively. It was found that the increase in UV intensity and solar radiation had a positive effect on decreasing NO and SO2 concentration. In the future, the NST will be applied at in-service photocatalytic block pavements to validate the environmental performance in field conditions.

Experimental investigation on the ventilation performance of diffuse ceiling ventilation in heating conditions

This paper aims to investigate the performance of diffuse ceiling ventilation (DCV) in heating mode by a full-scale chamber. Eleven cases combined with different exhaust positions, supply air change rates, internal heat source intensities, and the type and location of contaminant sources were tested. The contaminant removal effectiveness (CRE) and temperature effectiveness (TE) were utilized to evaluate the ventilation effectiveness of DCV. It is found that thermal discomfort due to vertical temperature differences or draught is negligible for all tested cases. The results demonstrate that the effect of exhaust positions on CRE depends on the existence of internal heat source. With the presence of heat source, the room air can reach a good mixing, and the effect of exhaust positions is therefore limited. Nevertheless, when there is no internal heat source, the lower position can force the supply air to enter the occupied zone and improve ventilation performance. Increased air change rates can significantly improve indoor air quality, but have a little influence on ventilation effectiveness. CRE is strongly influenced by the internal heat source intensity and the contaminant source type. With the increase of heat source intensity, CRE increases notably from 0.28 to 0.82. As for different contaminant source types, CRE is about 1.3 under the active source (with heat), but only 0.68 and 0.82 under the passive source (without heat). This study is beneficial to the further design and optimization of DCV for its broader heating application.

Indoor air depolluting material: Combining sorption testing and modeling to predict product's service life in real conditions

Indoor air quality is an important performance aspect in assuring a healthy and sustainable habitat. Building materials, occupant and related activity are some of the identified major indoor sources of formaldehyde, a high priority pollutant for indoor environmental health. Sorption materials embedded in gypsum wall and ceiling boards have been developed as an effective solution on the market to reduce the formaldehyde concentration levels indoors. A question often raised is the service life of the solution through time. This paper presents a methodology that combines sorption testing in small and full-scale chambers with mathematical modeling to provide a lifetime estimation on an industrial board in the frame of a collaborative work involving a material supplier (Saint-Gobain), university researchers (Syracuse University) and an independent testing and certification body (UL). This novel methodology is a combination of short- term & long-term performance assessments at chamber and room level using Certification laboratory reports or internal small-scale chamber sorption testing with CLIMPAQ tools to feed an analytical predictive model allowing extrapolation of service life. The predictive model accounted for the sorption characteristics of the Activ’Air® plasterboard with no additional finishing obtained from the small-scale chamber testing, the convective mass transfer resistance over the material surfaces and typical indoor formaldehyde pollution load condition, and was validated with full-scale experiments under ventilation conditions typical of ventilated spaces in residential and commercial buildings. Results show that the plasterboard tested is effective in removing formaldehyde over 50 years under realistic ventilation and standard average pollution load conditions.

Experimental and numerical study on the thermal performance of ventilated roof composed with multiple phase change material (VR-MPCM)

In the hot summer, roof is the prime location absorbed the most solar radiation for both residential and commercial buildings. Hence, enhancing the thermal performance of roofs is essential for reducing the heat gain thus building load. In this study, a novel ventilated roof composed with multiple phase change material (VR-MPCM) was proposed and its thermal performance was investigated experimentally and numerically. A contrast experiment was conducted in two full-scale chambers. The research results indicated that VR-MPCM can reduce the indoor peak temperature by 16.9–18.8%, and push back the peak temperature occurrence time by 30–50 min compared with the conventional ventilated roof (CVR). In addition, the cumulative heat flux during 4320 min demonstrated that the energy conservation rate of VR-MPCM can go up to 97.1% compared with the CVR. A verified three-dimensional transient heat transfer model was introduced for further research. Through the simulation research, intermittent opening of vents was found to be the best operating strategy for reducing heat gain. Regional comparison indicated that VR-MPCM in severe cold and cold climate zones had obvious energy saving potential. In conclusion, VR-MPCM has a potential of energy saving by reducing the diurnal heat gain and utilizing the nightly free cooling.

Limitations and applicability of a new small-scale measuring setup for sound insulation characterization

The development of soundproofing materials with exceptional acoustic properties has been of great interest in recent years. The acoustic characterization of such materials using full-scale reverberation chambers requires the preparation of relatively large-sized specimens, fulfilling the requirements of the ISO 10140 standards; this is a costly and time-demanding process. Recently, various methods based on the utilization of small-sized specimens have been developed by numerous researchers, so that the acoustic performance of a large selection of materials can be more rapidly assessed in the laboratory. However, such attempts to experimentally characterize soundproofing materials have specific limitations with regard to the validity of the measured sound reduction index. The article addresses the use of a small-scale measuring setup which can be used to study the sound insulation characteristics of a variety of materials, taking into account the limitations and applicability of the setup. The experimental analysis was performed on three materials that are widely used in building and civil engineering applications but have completely different internal structures and mechanical properties. It is shown that the use of the proposed small-scale measuring setup is more appropriate for materials with lower structural stiffnesses and with higher critical frequencies, as well as for porous materials with open pores. © 2019 Institute of Noise Control Engineering.

Characteristics of airborne transmission under stratum ventilation

The objective of this study is to investigate the characteristics of airborne spread of exhaled droplet nuclei between two occupants in a space conditioned by a horizontal air distribution method, known as stratum ventilation. Experiments were conducted in a full-scale climate chamber. Two breathing thermal manikins were used to simulate a standing infected person and a standing exposed person, respectively. Tracer gas (N2O) was added into the air exhaled by the infected manikin. The tracer gas concentrations in the air inhaled by the exposed manikin and at the ventilation exhaust were continuously monitored. ACH was kept at 2 h-1. The variables in the experiments include the positioning of the manikins, the distance between manikins, and the room air temperature. The horizontal supply airflow to the breathing zone strongly intensifies the mixing between the flow of exhalation and the room air, which reduces the exposure risk of occupants at close proximity and flattens the risk-distance curves. The homogenization of concentration weakens considerably the importance of the relative positioning and location of the infected and exposed persons. All those characteristics of airborne transmission may not be maintained, however, if the horizontal supply jet does not interact directly with the occupants. The findings from this study are intended to contribute for better understanding of airborne transmission indoors.

Stability Index for Injection-Coupled Instability in Full-Scale Firing Tests

To construct a stability estimation tool for injection-coupled instability in rocket engines, a linear stability analysis was applied. The amplifying factor related to injector-element acoustics and the damping factor related to chamber acoustics were defined. A complex vector, which is a function of these factors, was introduced. The stability for gain and that for phase were defined by the vector, and the bulk stability was defined by these stabilities. Because of time-lag findings obtained from subscale firing tests, the instability index, which was defined as inverse of the bulk stability, was defined only by the stability of gain. To validate the tool, the stability of cryogenic oxygen/hydrogen firing tests with a full-scale chamber was rated. The average acceleration was applied as an instability index for the firing tests. By setting the instability index by the tool at as the threshold that divides “unstable” and “stable,” the stability obtained by the tool and that of the firing test showed a good correlation for three test cases. In the fourth test case, the tool could not re-create the test result. In conclusion, the present tool can detect an instability that is dominated by gains rather than by time lags.

Micro-environmental control for efficient local cooling

Micro-environment is hereby defined as the air space and environment around a person that directly impacts his/her thermal sensation. Most existing HVAC systems condition the air of the entire room including the unoccupied space, which leaves a big potential to save energy. This study aims at evaluating the performance of three existing air terminal devices (ATDs) to locally remove enough heat from the micro-environment to manage the thermal balance so as not to sacrifice thermal comfort when the ambient unoccupied space temperature is increased by 2.2 °C from 23.9 °C to 26.1 °C in the summer to reduce the external cooling load. A computational fluid dynamics (CFD) model was developed, validated by full-scale chamber tests and applied to evaluate different configurations of the ATDs for local cooling. Results show that the predicted performance agreed well with the measurements, and the selected ATD, with only 50 W cooling power, was always able to remove a sufficient amount of heat from the micro-environment in a room of raised temperature, when the manikin was moved inside a semicircle movement range. The cooling performance of the jet was increased more by increasing the supply air flow rate than reducing the supply temperature and was highly dependent on the shooting angle. The heat flux from the manikin surface is very sensitive to the surface temperature and furniture placement, and proper specification of the surface temperature is crucial for the CFD simulation to match the measured results.

Toward effective design and adoption of catalyst-based filter for indoor hazards: Formaldehyde abatement under realistic conditions

Catalytic oxidation at ambient temperature has drawn wide attention as a new promising method of air cleaning, converting hazardous materials into non-hazardous ones. However, limited information is available regarding catalytic filter performance/characteristics under real operating conditions, especially on service efficiency and byproducts. Also, no practical scale-up method/evidence for filter performance evaluation is currently available to scale-up laboratory results to real application conditions. These limitations and knowledge gaps prevent building owners/designers from adopting this new promising technique in their commercial/industrial applications. The present study conducted experiments from small-scale to full-scale chamber tests which challenged a developed catalytic filter under realistic conditions. Formaldehyde was selected for approach demonstration due to its indoor ubiquitousness and criticality for human health even at low-levels. Results showed that the competition level for reaction sites in filter media had a crucial role in the performance for formaldehyde abatement, a high initial (77%; under no competing pollutants) to a typical stable level (23–32%), depending on the coexistence of other pollutants and moisture in the air, that the employment of this type of filter might generate byproducts (opposite to previous literature reports), and that small-scale column tests represented a good indication for large-scale filter performance as a practical screening method.

Volatile organic compound emissions from markers used in preschools, schools, and homes

ABSTRACTThere is little published research examining volatile organic compound (VOC) emissions from art markers. In this study, we characterised VOC emission rates from markers commonly used by children at home and in school, and by teachers in their classrooms. We developed a method to measure standardised emission rates under controlled laboratory conditions, focusing on four major marker types: permanent, dry erase, highlighter, and washable. Emission rates for other less common marker types were also measured. We conducted additional experiments determining changes in emission profiles over short and long time periods (several hours up to daily use over about 2 months), as well as during periods of active drawing. We tested a total of 101 markers and report emission rates for 60 chemicals. Permanent and dry erase markers had average total VOC emissions more than 400 times higher than highlighters and washable markers. Alcohols were the most highly emitted class of VOCs from permanent and dry erase markers. Some chemicals associated with potentially serious health concerns were also identified. Future studies that employ full-scale chamber experiments and personal monitoring in classrooms to measure children’s actual exposures are recommended.

Dispersion of indoor air pollutants emitted at near-floor levels in rooms with floor heating and mixing ventilation

The usage of floor heating is increasing in low-energy buildings as it enables efficient applications of low-exergy level heat sources as well as provides a uniform distribution of air temperature and low air velocities in heated spaces. The aim of this study was to analyse the effects of floor heating on the dispersion of gaseous pollutants emitted at the floor level, considering that carpets and flooring materials can be sources of such pollution. Mixing ventilation with high-level wall grille air supply and in-ceiling four-way air supply was tested numerically and experimentally in the full-scale chamber at the air change rate of 2 h−1. Three positions of a heated dummy in relation to the pollution source, cold surface and air supply diffusers were analysed. Both experiments and CFD predictions revealed the overall positive effect of floor heating on ventilation effectiveness and personal exposure. Floor heating increased pollutant removal effectiveness by 5% and reduced personal exposure by 22% on average.

Transverse Instability Studies in a Subscale Chamber

High-frequency combustion instabilities result from a coupling between modes of heat release and chamber acoustics. Because the geometric dimensions of the chamber define the relevant acoustic modes, it is particularly difficult to study transverse instabilities in anything other than a full-scale chamber. In this paper, results from experimental studies of a two-dimensional subscale chamber that can nearly replicate full-scale acoustic modes are described. The acoustic modes are primarily driven by injector elements at the endwalls of the rectangular chamber. They were designed to be unstable, based on a vortex-shedding mechanism postulated on earlier results from longitudinal studies. The 27-cm-wide by 19-cm-long chamber produced transverse instabilities with a first width-mode frequency of about 2000 Hz, with no longitudinal mode content in the pressure signal. The chamber comprises a linear array of seven gas-centered swirl coaxial liquid injectors, designed to flow either bipropellants, only oxidizer, or nothing. Eight different flow configurations were tested, yielding peak-to-peak pressure oscillation amplitudes ranging from about 5% to nearly 100% of chamber pressure. The strongest instabilities were observed when endwall injectors flowed both fuel and oxidizer, and amplitudes were reduced as the driving injectors were moved inward. An asymmetric setup demonstrated that the unsteady pressures in warm regions and hot regions have differing pressure amplitudes. To demonstrate the potential use of the chamber for measuring the combustion response to velocity and pressure oscillations, the synchronized measurement and analysis of pressure and flame emission are presented.

Efficient Computation of Thermoacoustic Modes in Industrial Annular Combustion Chambers Based on Bloch-Wave Theory

Most annular combustors feature a discrete rotational symmetry so that the full configuration can be obtained by copying one burner-flame segment a certain number of times around the circumference. A thermoacoustic model based on the Helmholtz equation then admits special solutions of the so-called Bloch type that can be obtained by considering one segment only. We show that a significant reduction in computational effort for the determination of thermoacoustic modes can be achieved by exploiting this concept. The framework is applicable even in complex cases including an inhomogeneous temperature field and a frequency-dependent, spatially distributed flame response. A parametric study on a three-dimensional combustion chamber model is conducted using both the full-scale chamber simulation and a one-segment model with the appropriate Bloch-type boundary conditions. The results for both computations are compared in terms of mode frequencies and growth rates as well as the corresponding mode shapes. The same is done for a more complex industrial configuration. These comparisons demonstrate the benefits of the Bloch-wave based analysis.

Design and commissioning of a semi-confined blast chamber

Abstract This paper presents the design, test and analysis of a scaled cylindrical blast chamber. The blast chamber is a one-fifth dimensional size replica of the full-scale blast chamber (Emily). The blast chamber is semi-confined as one end is open. The scaled blast chamber is used to test concepts for closing the open end and allows the gas to vent at the same time. ANSYS AUTODYN calculated the pressure time histories for different closure scenarios. Comparing the results suggested a viable scenario, namely a structure consisting of a circular disc and a frame positioned at the open end of the blast chamber. The structure and cylindrical blast chamber were subjected to scaled blast tests and the pressure results are presented and discussed.