Small Test Chamber Research Articles

Study on adsorption and purification materials for ethylene in cold storage

In view of the lack of systematic quantitative and comparative studies on the purification effect of ethylene adsorbent in cold storage, starting from the selection of purification materials, this paper analyzed the purification effect of different zeolite materials on ethylene through a small test chamber, and screened out the best zeolite adsorbents used in self-made purification device. Combined with characterization analysis, purification efficiency evaluation and adsorption capacity of zeolite material, the removal performance of ethylene was investigated. The results showed that the zeolite samples with rough and porous surface showed better adsorption performance for ethylene. The larger the specific surface area and total pore volume, the stronger the adsorption capacity to ethylene. In addition, the presence of Na elements and mesoporous increased the exchange capacity and pore volume, which also played a certain role in the ethylene adsorption process. Experimental result demonstrates that clean air volume (CADR) of ethylene is 232 m3/h, the ethylene removal rate at 30 min is 98.19%, and the purification energy efficiency is 1.39. At the same time, the adsorption capacity of the selected zeolite sample is 1380.5 μg/g by dynamic adsorption experiment, and the service life of the filter element of the self-made purification device is estimated to be 166 days. This study can provide a theoretical basis for ethylene purification in cold storage.

Facile strategy of preparing excellently thermal-insulating and fire-safe building materials based on an aromatic Schiff base dicarboxylic acid without additional flame retardants

Developing excellently fire-safe and thermal-insulating building materials is a critical subject in the building sector. In this work, a novel aromatic Schiff base dicarboxylic acid (FN) was synthesized through a facile strategy to prepare high-performance rigid polyurethane foam (RPUF) composites with excellent thermal insulation and fire safety performance. The uniform dispersion of FN in polyether polyol improved the cellular structure of RPUF composites, which was conducive to increasing the thermal insulation of RPUF composites. Therefore, incorporating only 10 wt% FN into RPUF composite (RPUF/10FN) possessed the lowest wall temperature (51.9 °C) and room temperature (38.8 °C) with the lowest temperature growth rate under the continuous thermal radiation of the heat source among all samples in the small chamber test. Moreover, FN remarkably reduced the peak heat release rate, peak smoke production rate, and peak CO production rate of RPUF/10FN by 41.9%, 58.0%, and 59.6% without additional flame retardants, respectively, compared with those of pure RPUF. In addition, FN endowed RPUF/FN composites with better fire resistance and structural integrity compared with pure RPUF in the building facade fire test and fire protection test. The increased fire safety of RPUF/FN composites is due to the barrier effect of the formation of a dense and continuous char layer and the dilution effect of nonflammable gas generated by the thermal degradation of FN. Furthermore, FN enhanced the water contact angle of RPUF/FN composites from 112.2° for pure RPUF to 120.8° for RPUF/10FN, indicating that FN also enhanced the hydrophobicity of RPUF/FN composites. Therefore, the as-designed RPUF composites containing FN possessed a broad application prospect in the building field.

Research on Temperature Field of Wheat Grain Piles in Underground Granary

AbstractTo investigate the temperature change in grain piles during underground grain storage, this study considers the wheat as the research object, The method of combining numerical simulation and small chamber test is adopted to study the changes in the temperature field in the experimental warehouse during natural storage conditions. Then, based on the numerical simulation software COMSOL is used to simulate and analyze the influence of different storage time, different covering soil depth, and different porosity on the temperature field of the grain pile in the warehouse. The results show that: during natural storage conditions, the temperature in the test warehouse is obviously stratified; under different initial grain pile temperature conditions, the difference between the initial grain temperature and ground temperature affects the change range of the temperature of the grain pile in the warehouse; when the temperature is 0.5, the change of the grain pile in the warehouse is the largest, which is 0.52 °C. When the porosity is 0.3, the temperature of the grain pile in the warehouse changes the smallest, which is 0.48 °C. The microenvironment changes in the warehouse under complex conditions can be analyzed in the follow‐up, and further formulations for safe grain storage can be made effective.

Internal diffusion and re‐emission of leaked liquid ethyl acetate from mortar materials

AbstractAssuming the leakage of hazardous liquid chemicals in factories and chemical plants caused by natural disasters or human error, it is important to precisely estimate exposure risk and design appropriate evacuation plans and risk‐reduction measures. The exposure risk of indoor residents to leaked chemicals may be estimated using direct measurements or theoretical/numerical estimations of gas‐phase concentrations. Although mathematical models of gas‐phase concentration in the workplace are essential for predicting exposure concentrations at the design stage, practical models have not yet been fully established. We previously proposed practical numerical models to assess indoor gas‐phase concentration distributions after the accidental leakage of liquid chemicals using liquid toluene as a representative hazardous chemical. In this study, the leakage of liquid ethyl acetate, a commonly used organic solvent, into mortar flooring was reproduced in a small test chamber, and numerical analysis was performed. The results showed that the time history of the chamber exhaust concentration had a sharp peak and differed significantly from that of toluene. Three‐dimensional computational fluid dynamics (CFD) analysis incorporating practical ethyl acetate emission models reproduced the external and internal emission characteristics of leaked ethyl acetate on the mortar material. The models showed reasonable agreement with the experimental data.

A simple method for validating a simulation model of a radiant ceiling panel with thermal energy storage

This paper focuses on validating a simulation model of a radiant ceiling panel (RCP) incorporating phase change materials (PCM) for heating and cooling applications in buildings. The development of an RCP with thermal energy storage capacity aims to encourage high thermal mass radiant systems in existing buildings to replace the traditional all-air HVAC system. First, a heat flow meter (HFM) is used to perform enthalpy measurements at a product scale (macro-encapsulated PCM). Then, a small test chamber is constructed to measure the dynamic thermal performance of an RCP with PCM under well-known and realistic boundary conditions. A known thermal resistance is used to establish a realistic heat transfer coefficient between room air (represented by the temperature of a temperature-controlled metal plate) and ceiling. The results show that HFM enthalpy measurements of products incorporating PCM are within ± 2% of manufacturers’ data. Additionally, results indicate that a test chamber can be used for validating a dynamic simulation model of the RCP with PCM installed in a room. The proposed method can be helpful during the system optimization phase, as many conditions and sample configurations can be tested without spending too much time or money on test rooms or real building monitoring.

Design and control of radiant ceiling panels incorporating phase change materials for cooling applications

Experimental and numerical studies have demonstrated that thermally activated building systems (TABS) may lead to significant energy savings. However, TABS are generally incorporated into the building during the construction phase, limiting their adoption to new buildings. To encourage the application of TABS during building refurbishments, the authors have developed a radiant ceiling panel (RCP) with macroencapsulated phase change materials (PCM). This study aims to provide the criteria to design, size, and control the newly proposed RCP-PCM system. A simplified method to size and design the RCP-PCM system for cooling applications is developed from a set of parametric dynamic simulations. At first, the thermal storage properties of the macro-encapsulated PCM were determined using the standard ASTM C1784-20. The obtained properties were then used in a whole-building simulation model validated using measurements in a small test chamber that replicates the conditions of an actual test room. The PCM panel thickness of 0.015 m and a supply water temperature of 15 ℃ showed the best results in terms of thermal comfort and effective thermal energy storage capacity. The implementation of the simplified method in a case study showed that the RCP-PCM system maintained room conditions within the specified thermal comfort range (−0.5 < PMV < 0.5) for more than 90% of the occupied periods in all of the evaluated cooling-dominated climates. Moreover, yearly-round, the PMV values never reached values higher than 0.8 or lower than −0.6, confirming the effectiveness of the proposed method for designing a RCP-PCM system. The results show that energy savings of 22% could be obtained in a very hot and humid climate using an RCP-PCM system instead of a conventional all-air system. In conclusions, this paper offers a new system to promote energy flexibility and Demand-Side Management (DSM) strategies to modulate the energy demands in retrofitted buildings.

Transfer of exposure therapy effects to a threat context not considered during treatment in patients with panic disorder and agoraphobia: Implications for potential mechanisms of change

Further developments of exposure-based therapy (EBT) require more knowledge about transfer of treatment to non-trained everyday contexts. However, little is known about transfer effects of EBT.Using a standardized EBT protocol in 275 patients with panic disorder and agoraphobia we investigated the transfer of EBT to a highly standardized context during a Behavioral Avoidance Test (BAT; being entrapped in a small and dark test chamber) and not part of the exposure sessions. Patients of a treatment group underwent the BATs before treatment (t1), after a preparatory treatment phase (t2), and after an agoraphobic exposure phase (t3) and were compared with wait-list control patients, who repeated BAT assessments across the same time period.We found stronger reductions in avoidance behavior, reported fear, and autonomic arousal during the BAT from t1 to t3 in the treatment group patients who were anxious during t1 relative to the anxious but untreated patients. Fear reduction was related to treatment outcome indicating the contribution of transfer effects to successful EBT. Interestingly, reduction varied for different fear response systems suggesting different processes to may be involved in transfer effects. Importantly, final BAT assessment still evoked residual fear in the treatment group as compared to BAT non-anxious control patients, suggesting limited transfer effects – one possible reason for the return of symptoms in new situations.

Improvement of Bearing Capacity of Shallow Foundation with the Wall Attached to the Base-Slab: Model Test

For the cases where shallow foundation cannot satisfy the requirement of the foundation, engineers choose deep foundations without careful consideration of the cost-effectiveness. However, the bearing capacity of deep foundation is much bigger than shallow foundation. In this study, innovative shallow foundation type is introduced to increase the bearing capacity: The walls are attached to the base-slab of shallow foundation. To validate the performance of suggested shallow foundation, model tests were performed. Three different models (plate-, table-, and box-wall shaped foundations) are constructed in a small and large chamber, respectively. In the small chamber tests, the effect of degree of compaction (40, 60 and 80%) and footing width and wall length ratio (0.2, 0.4, 0.6, 0.8 and 1) on bearing capacity are evaluated. In large chamber test, the performance of wall-shaped foundation with respect to ultimate bearing capacity is evaluated. From the model tests, it is found that box-wall shaped foundation can increase the bearing capacity than table- and plate-wall shaped foundation. Also, the ultimate bearing capacities of box-wall shaped foundation are about 1.8 times than that of shallow foundation without wall.

A novel metal-organic frameworks based humidity pump for indoor moisture control

Latent heat load accounts for a significant proportion of energy consumption by air-conditioning, particularly for buildings in humid climates. Traditional vapor-compression refrigeration dehumidification faces problems like refrigerant leakage, overcooling, and complicated mechanical systems. Here, we report a novel humidity pump that uses metal-organic frameworks (MOFs) as desiccant layers to transport moisture from a low-humidity space to a high-humidity one efficiently. The working principle and operation modes of the humidity pump are introduced herein for which the dehumidification performance is investigated at 22.8 °C with 60% RH. The dehumidification rate and moisture removal efficiency of the MIL-100(Fe) based humidity pump reached 26.24 g h−1 and 0.87 g Wh−1, respectively, and these are 2.15 and 2.12 times higher than that of the humidity pump with silica gel coating. The maximum dehumidification coefficient of performance (DCOP) of the humidity pump could reach up to ~0.46, higher than the conventional desiccant dehumidification systems. In addition, many factors, such as the cycle time, thermoelectric power, air velocity, etc., which may affect the dynamic characteristics and dehumidification performance, were analyzed. Lastly, the localized humidity management ability of the designed humidity pump using MIL-100(Fe) was validated by a small chamber test. The results indicate that the MOF humidity pump could achieve energy-efficient localized moisture control.

Evaluating Volatile Organic Compound Emissions from Cross-Laminated Timber Bonded with a Soy-Based Adhesive

Volatile organic compound (VOC) emissions from indoor sources are large determinants of the indoor air quality (IAQ) and occupant health. Cross-laminated timber (CLT) is a panelized engineered wood product often left exposed as an interior surface finish. As a certified structural building product, CLT is currently exempt from meeting VOC emission limits for composite wood products and confirming emissions through California Department of Public Health (CDPH) Standard Method testing. In this study, small chamber testing was conducted to evaluate VOC emissions from three laboratory-produced CLT samples: One bonded with a new soy-based cold-set adhesive; a second bonded with a commercially available polyurethane (PUR) adhesive; and the third assembled without adhesive using dowels. A fourth commercially-produced eight-month-old sample bonded with melamine formaldehyde (MF) adhesive was also tested. All four samples were produced with Douglas-fir. The test results for the three laboratory-produced samples demonstrated VOC emissions compliance with the reference standard. The commercially-produced and aged CLT sample bonded with MF adhesive did not meet the acceptance criterion for formaldehyde of ≤9.0 µg/m3. The estimated indoor air concentration of formaldehyde in an office with the MF sample was 54.4 µg/m3; the results for the soy, PUR, and dowel samples were all at or below 2.5 µg/m3.

Development of a personal passive air sampler for estimating exposure to effective chlorine while using chlorine-based disinfectants.

With an increasing use of indoor disinfectants such as chlorine (Cl2) and hypochlorous acid, a convenient sampler for estimating exposure to oxidants, such as effective chlorine, is necessary. Here, we developed a personal passive air sampler (PPAS) composed of a redox dye, o‐dianisidine, in a polydimethylsiloxane (PDMS) sheet. o‐Dianisidine readily reacts with gaseous oxidants generated by bleach usage, and its color changes as the reaction progresses; hence, personal exposure to effective chlorine could be easily detected by the naked eye, while cumulative exposure could be determined by measuring concentrations of o‐dianisidine reacting with it. The PPAS was calibrated, and a sampling rate of 0.00253 m3/h was obtained using a small test chamber. The PPAS was tested with the help of ten volunteers whose personal exposure to Cl2‐equivalent gas was estimated after bathrooms were cleaned using spray and liquid‐type household disinfection products, and the accumulated exposure‐gas concentrations ranged from 69 to 408 ppbv and 148 to 435 ppbv, respectively. These PPAS‐derived exposure concentrations were approximately two orders lower than those estimated using ConsExpo, suggesting a significant overestimation by prevailing screening models, possibly due to the ignorance of transformation reactions.

Computational fluid dynamics prediction of formaldehyde emission and sorption processes in a small test chamber with mixing fan and vents

Abstract Characterizing the emission performance of formaldehyde is critical for control strategies. Most previous emission models assume that formaldehyde concentrations are well-mixed. In this study, a computational fluid dynamics-based model is developed for simulating the mass transfer and adsorption/desorption processes of formaldehyde from particleboards in a chamber with a mixing fan. Numerical investigations on the impacts of the mixing fan, adsorption/desorption rate constants, and key transport parameters influencing the emission behaviors are conducted for the first time. The results show that the complete mixing assumption is not appropriate in the early emission period. Incomplete mixing becomes more significant with a decreasing rotation speed, leading to a time-dependent equivalent mass transfer coefficient. The deviation in the maximum concentration between the simulated curves with and without the adsorption/desorption effect is approximately 8.5%. A coefficient of mixing of 0.0283 is suitable for evaluating complete mixing in the chamber. With an increase in the rotation speed, the degree of mixing improves, and the mass transfer coefficient increases sub-linearly. Secondary reemission becomes more significant and begins earlier for materials with lower partition coefficients and higher diffusivity.

The Role of Green Building Materials in Reducing Environmental and Human Health Impacts.

Conventional building materials (CBMs) made from non-renewable resources are the main source of indoor air contaminants, whose impact can extend from indoors to outdoors. Given their sustainable development (SD) prospect, green building materials (GBMs) with non-toxic, natural, and organic compounds have the potential to reduce their overall impacts on environmental and human health. In this regard, biocomposites as GBMs are environmentally friendly, safe, and recyclable materials and their replacement of CBMs reduces environmental impacts and human health concerns. This study aims to develop a model of fully hybrid bio-based biocomposite as non-structural GBMs and compare it with fully petroleum-based composite in terms of volatile organic compound (VOC) emissions and human health impacts. Using a small chamber test (American Society for Testing and Materials (ASTM)-D5116) for VOC investigation and SimaPro software modeling with the ReCiPe method for evaluating human health impacts. Life cycle assessment (LCA) methodology is used, and the results indicate that switching the fully hybrid bio-based biocomposite with the fully petroleum-based composite could reduce more than 50% impacts on human health in terms of indoor and outdoor. Our results indicate that the usage of biocomposite as GBMs can be an environmentally friendly solution for reducing the total indoor and outdoor impacts on human health.

Use of a small‐scale, portable test chamber for determining the bactericidal efficacy of aerosolized glycol formulations

This study aimed to understand the efficacy and mechanisms of action of an aerosolised glycol-ethanol formulations against bacteria. We validated a small scale in-house test chamber to determine the microbicidal efficacy of four aerosolized formulations combining dipropylene glycol and ethanol against Staphylococcus aureus and Escherichia coli embedded in alginate. The aerosolised glycol/ethanol formulation decreased bacterial viability by 3 Log10 and was more efficacious than an ethanol only control formulation. Electron microscopic examination indicated extensive structural damage in both bacteria, and membrane damage was confirmed with potassium release in S. aureus and DNA release in E. coli. The development of a small test chamber facilitated the measurement of the microbicidal efficacy and experiments to understand the mechanism of action of an aerosolised microbicidal formulation.

Development of a procedure for estimating the parameters of mechanistic VOC emission source models from chamber testing data

In order to evaluate the impacts of volatile organic compounds (VOCs) emissions from building materials on the indoor air quality beyond the standard chamber test conditions and test period, mechanistic emission source models have been developed in the past. However, very limited data are available for the required model parameters including the initial concentration (Cm0), in-material diffusion coefficient (Dm), partition coefficient (Kma), and convective mass transfer coefficient (km). In this study, a procedure was developed for estimating the model parameters by using VOC emission data from standard small chamber tests. In the procedure, initial values of the model parameters were refined by multivariate regression analysis of the measured emission data. To verify the procedure and estimate its uncertainty, simulated chamber test data were generated by adding 10% experimental uncertainties on the theoretical curve from the analytical solution to a mechanistic emission model. Then the procedure was applied to the generated data to estimate the model parameters. Results indicated that estimates converged to the original parameter values used for the data generation and the error of estimated parameters Dm, Cm0 and Kma were within ±10%, ±23%, and ±25% of the true values, respectively. The procedure was further demonstrated by applying it to estimate the model parameters from real chamber test data. Wide application of the procedure would result in a database of mechanistic source model parameters for assessing the impact of VOC emissions on indoor pollution load, which are essential input data for evaluating the effectiveness of various indoor air quality (IAQ) design and control strategies as well as the energy required for meeting given IAQ requirements.

Comparing predictions by existing explicit emission models to real world observations of formaldehyde emissions from solid materials

Existing general explicit mass transfer models for volatile organic compound emissions have been validated against experimental results from small test chambers. This study compared emission rates predicted by such models to observations from homes, large test chambers and full scale experiments. The comparison revealed that the examined explicit emission models could not simulate behaviour observed under real world conditions for the cases studied. It is hypothesised that the reasons for the observed discrepancies include that: (1) There is a shortage of detailed information on the actual physical conditions at the emitting surfaces under real world conditions. (2) The mathematics behind the explicit emission models does not allow such models to fully capture the dynamic behaviour of a system with varying temperature and relative humidity. (3) The assumption that change in the concentration in an emitting material is determined by diffusion alone, implicitly implying that generation is negligible, may not be valid outside small test chambers.

1g shaking table tests on residual soils in Malaysia through different model setups

Studies of soil dynamic properties in Malaysia are still very limited. This study aims to investigate the dynamic properties of two selected tropical residual soils (i.e., Sandy Clay and Sandy Silt) and a sand mining trail (Silty Sand) in Peninsular Malaysia using 1g shaking table test. The use of 1g shaking table test for soil dynamic testing is often constrained to large strain level and small confining pressure only. Three new experimental setups, namely large laminar shear box test (LLSBT), small chamber test with positive air pressure (SCT), and small sample test with suction (SSTS) are attempted with the aims of these experimental setups are capable of evaluating the dynamic properties of soils covering a wider range of shear strain and confining pressure. The details of each experimental setup are described explicitly in this paper. Experimental results show that the combined use of the LLSBT and SCT is capable of rendering soil dynamic properties covering a strain range of 0.017%-1.48% under confining pressures of 5-100 kPa. The studied tropical residual soils in Malaysia behaved neither as pure sand nor clay, but show a relatively good agreement with the dynamic properties of residual soils in Singapore. Effects of confining pressure and plasticity index on the studied tropical residual soils are found to be insignificant in this particular study.

光触媒反応による室内汚染物質濃度低減性能の数理モデル化と数値予測 第1報-小形チャンバーを用いた濃度低減性能試験と濃度依存性を考慮した光触媒反応モデルの提案

光触媒反応による室内汚染物質濃度低減性能の数理モデル化と数値予測 第1報-小形チャンバーを用いた濃度低減性能試験と濃度依存性を考慮した光触媒反応モデルの提案

Computational fluid dynamics modeling and parameterization of the visible light photocatalytic oxidation process of toluene for indoor building material

Poor indoor environmental conditions caused by the presence of gas-phase/aerosol-phase contaminants are thought to be potential triggers of illnesses, leading to productivity losses. In recent decades, the photocatalytic oxidation (PCO) process has attracted attention because of its potential to purify indoor air polluted with volatile organic compounds (VOCs), especially at low concentration levels. Titanium-dioxide (TiO2)-bound building materials have been extensively studied for the oxidation of indoor VOCs. In this study, kinetic studies were carried out to evaluate the PCO of toluene in the gas phase, over TiO2-bound building materials, using a 20l small test chamber. A Langmuir–Hinshelwood (L–H)-type model, for reproducing the PCO process over TiO2-bound building materials, was developed as a function of the toluene concentration, illumination intensity, and humidity levels. The parameters of the L–H model were determined using the hybrid identification procedure of computational fluid dynamics (CFD) simulations and a 20l small test chamber experiment. By using this hybrid identification method, PCO kinetic parameters were estimated with reference to the concentration in viscous-sub layer. Finally, CFD simulations were also carried out under the same boundary conditions as those used in the chamber experiments to evaluate the prediction accuracy.

A-24 揮発性有機化合物の放散・吸脱着等のモデリングとその数値予測に関する研究(その14) : 建材表面気流精密制御 Small Test Chamberの開発と物質伝達率の測定

A-24 揮発性有機化合物の放散・吸脱着等のモデリングとその数値予測に関する研究(その14) : 建材表面気流精密制御 Small Test Chamberの開発と物質伝達率の測定