Compartment Walls Research Articles

Acoustic metamaterials of double-layer structure for sound insulation

Insulation against air-borne sound is one of the earliest research fields of acoustic metamaterials. The sound insulation of the conventional sound insulation structure is generally limited by the law of mass. When the density of the structural surface is doubled, the low-frequency sound insulation is only increased by 6dB.In our report, we introduce a double-layer resonator-type acoustic metamaterial, which consists of two honeycomb sandwich panels, two perforated panels, and a thin air layer. Firstly, for two singer -layer resonator-type acoustic metamaterial, different sound absorption frequency points were designed. Secondly, a calculation model of sound insulation metamaterial with double-layer resonator type is established. The results show that the sound insulation performance of the structure greatly breaks through the law of mass in the frequency range of 165Hz-3150Hz. Finally, for the application requirements of the manufacturer, the compartment wall components and composite sound insulation door core components are designed. The reasonable design of Double-layer resonator-based honeycomb metamaterial structural parameters can solve the problem of low-frequency noise of thin-layer lightweight structure.

Experimental and theoretical investigation of an adjacent wall on the occurrence of flashover

In urban or informal settlement fires, the influence of an adjacent inert wall/dwelling on the fire development of the burning dwelling is still unknown. Therefore, 41 compartment fire experiments were conducted with a ¼ scale ISO 9705 room, with a calcium silicate board acting as the inert wall, was placed in front of the burning compartment's opening with distances between 50 and 1250 mm. Parameters such as the mass loss rate of fuel, temperatures of gas and walls, heat flux imposed on the floor, and time to flashover were analyzed. From the experiments, it was found that the flashover occurrence times differed significantly with or without the adjacent dwelling, and the time to flashover increased gradually with increasing distance from 50 to 300 mm between the burning compartment and adjacent wall, but decreased with distance from 300 to 600 mm. The heat flux to the floor was calculated and correlated well with measured values, confirming that the observed experimental phenomenon was primarily caused by the interaction between the combustion efficiency of fuel and the different heat losses from hot gas flowing out from the opening depending on the adjacent wall location. Moreover, a modified MQH method and a theoretical model were proposed to predict the gas temperature and time to flashover, respectively.

Prediction of Limit of Heat Release Rate during Flashover in a Compartment Space

This study derives a predictive equation for calculating the marginal heat release rate of flashover in a compartmentalized space. Moreover, other variables (in addition to the surface area and opening area of the compartment, which are used as variables is existing studies) were derived and modified. By collecting and analyzing the results of existing flashover experiments, the thermal inertia of the compartment wall was judged to be a variable that directly affects the indoor temperature rise. An equation constructed using this variable was found to be up to 6.5% more reliable than the existing predictive equations. However, for use in design prediction, the developed equation had to be adjusted to derive values lower than the experimental results; thus, an equation that corrected the safety rate was derived. From this calculation, a design prediction equation was derived, from which flashover is predicted to occur before the time predicted in existing experiments.

Dependence of Fire Safety on the Spaced Installation of Fire Dampers

According to building regulations, fire dampers should be installed in or close to the part of the duct that penetrates the fire compartment. Accordingly, in construction sites, fire dampers are installed in or adjacent to the fire compartment wall and floor. However, they are often installed too far away from the fire compartment wall and floor because the law does not stipulate a clear standard for “close”. If this occurs, the duct and sleeve in the spaced part may be transformed by the high heat of a fire. Through this, smoke and flames can be directly transmitted to the neighboring compartment space, failing to ensure fire safety. Therefore, this study investigated the dependence of fire safety on the spaced installation of fire dampers by performance verification. From the performance verification results, it was found that the separation distance of the fire damper should be minimized (i.e., attached to the wall) to ensure fire safety.

Potential and pitfalls of XRF-CS analysis of ion-exchange resins in environmental studies

Detecting clandestine, intermittent release of heavy metal pollution into natural and man-made water ways is challenging. Conventional chemical methods are both labor intensive and expensive. A recent approach combining ion-exchange resins with the capabilities of X-ray fluorescence core scanners (XRF-CS) therefore is of great interest. In short, ion-exchange resin is deployed in the water using small sachets, the resin is then collected, dried, filled into sample holders and scanned using XRF-CS. Ion-exchange resins take up heavy metals in proportion to the concentration in the ambient water, with a correlation coefficient (R2) between concentration and XRF-CS counts better than 0.96 for most elements. However, a number of parameters influence the measurements. Different drying methods introduce differences in the XRF counts because of lattice bound water, resin shrinkage, and disaggregation of the resin particles. Furthermore, the newly developed sample carrier, which was constructed using 3D printed polymers, contains trace amounts of elements that may influence the sample measurements through edge effects and secondary fluorescence. In the tested sample carrier materials, substantial levels of Cr, Fe, Co, and Zn were detected, while Ca, Ti, Ni, Cu, Ga showed variable levels. Ba, Tl and Bi show very low levels, and Pb is only of importance in the PLA carrier. It is therefore necessary to streamline the analysis-process to ensure that the variations in sample treatment and drying and filling methods are minimized. It is also recommended that only spectra from the center of the compartments are used for the evaluation to avoid edge effects caused by secondary fluorescence of metals in the compartment walls. Although the technique of using ion-exchange resin sachets and XRF-CS analysis is only semi-quantitative, it is a cost effective and fast way to monitor large areas for environmental pollution, and the new sample carrier greatly contributes to make the process faster and less error prone.

A Novel Pressure-Controlled Revolute Joint with Variable Stiffness.

The compliance and deformability of soft robotics allow human-machine interactions in a safe manner without the need of sophisticated control systems inherent in rigid-body robotic devices. However, these advantages introduce controllability and predictability challenges. In this study, we propose a novel fluidic-driven variable stiffness revolute joint (VSRJ) based on hybrid soft-rigid approach to achieve adjustable compliance while addressing the abovementioned challenges. The VSRJ is composed of a silicone rubber cylinder as a pressure chamber and two identical rigid links. The soft cylinder is positioned in a fully closed compartment created by the assembly of the two rigid links, thus constraining its expansion when pressure is applied. By applying pressure, the stiffness of the joint increases accordingly for the following reasons: (1) increasing the friction force between the cylinder and the compartment walls and (2) creating a locking mechanism through the expansion of the cylinder into space between rigid links in a "bump" formation. Experimental results show that the VSRJ can achieve up to 8-fold rotational stiffness enhancement from 0 to 5 bar input pressure within -30° to +30° rotation angle. The modular design of the rigid link allows the assembly of multiple VSRJs to build a variable stiffness structure in which each VSRJ has an independent stiffness and relative position. The VSRJ was characterized in terms of repeatability, torque, and stiffness. The experimental results were validated by finite element analysis. This approach can provide opportunities for the use of this new variable stiffness concept as an efficient alternative to traditional variable-stiffness linkages.

Potential of activated carbon in lime mortar plastering in term of fire resistance and thermal performance

The use of lime mortar plastering for wall construction in residential and light commercial buildings has increased significantly over the world. The unique characteristic of hydrated lime increases the strength of the tensile bond. The more considerable the amount of cement content in cement lime mortar, the low the air content; thus, the bond strength stronger. The performance of plastering under fire exposure is an item of significant importance in securing construction. Activated carbon is one known adsorbent which has a high capacity to adsorb gases and improved fire resistance ability of concrete. The purpose of conducting this study is to identify the optimum proportion of lime mortar plastering containing activated carbon with different percentages which is 0%, 10%, 30% and 50% as cement replacement. Therefore, a fire resistance test was conducted on cement plaster mixtures with variable ratio content of activated carbon to identify the optimum proportion according to the temperature reading by an infrared thermometer for 30 minutes. Based on the results obtained, the sample with 30% activated carbon as cement substitution was the most effective since it gave a relatively low initial temperature reading which was 28.2°C. The test showed only a slight increase in temperature after the first five minutes, which is 93.1% and reached 108.2°C at maximum even after 30 minutes of testing. There was no hair crack developed, and no visible of smoke observed from the sample compared to existing plaster which formed hair crack and visible of smoke at 280°C after 16 minutes of testing. Therefore, 30% of activated carbon is the optimum proportion in lime mortar plastering due to ability to resist fire and prevention from hair crack and visible smoke formation. This proportion can be applied to the interior and exterior wall of the building, especially at the compartment wall and along the escape route.

Computation of a Compartment Fire with Smagorinsky Sub-Grid Scale Model

A fire tests using plywood crib as fire source was done in a cubical compartment to investigate the fire development and temperature distribution. The dimension of the experimental compartment was 4 m high, 4 m wide and 4 m length with a door opening of 2 m × 1 m wide located at one of the compartment wall. Several parameters were measured which includes fuel mass loss rate, compartment gas temperature, centerline doorway temperature, heat flux and wall surface temperature. Three-dimensional numerical simulations were performed using large eddy simulation with different values of Smagorinsky sub-grid scale constant. In order to accurately investigate the behavior of fire within the compartment by computational fluid dynamics (CFD), it is vital to study these Smagorinsky sub-grid scale constant. Numerically predicted results with various Smagorinsky sub-grid scale constant was compared with the physical results. It was found that the varying the Smagorinsky constant affect the numerical simulation results.

Study on Selection of Optimal Installation Positions of Fire Dampers to Secure Fire Safety Performance

Building regulations in recent times require that fire dampers be automatically closed when detecting smoke or flame in the event of a fire. However, they may be vulnerable to fire themselves because they contain combustibles, such as motors. Therefore, the optimal installation locations of fire dampers for securing fire safety performance were selected through performance verifications in this study. Thus, it was found that fire dampers installed in contact with the fire compartment wall surfaces would be advantageous for securing the required fire safety performance.

Osmosis-Driven Water Transport through a Nanochannel: A Molecular Dynamics Simulation Study

In this work, we study a chemical method to transfer water molecules from a nanoscale compartment to another initially empty compartment through a nanochannel. Without any external force, water molecules do not spontaneously move to the empty compartment because of the energy barrier for breaking water hydrogen bonds in the transport process and the attraction between water molecules and the compartment walls. To overcome the energy barrier, we put osmolytes into the empty compartment, and to remove the attraction, we weaken the compartment-water interaction. This allows water molecules to spontaneously move to the empty compartment. We find that the initiation and time-transient behavior of water transport depend on the properties of the osmolytes specified by their number and the strength of their interaction with water. Interestingly, when osmolytes strongly interact with water molecules, transport immediately starts and continues until all water molecules are transferred to the initially empty compartment. However, when the osmolyte interaction strength is intermediate, transport initiates stochastically, depending on the number of osmolytes. Surprisingly, because of strong water-water interactions, osmosis-driven water transport through a nanochannel is similar to pulling a string at a constant speed. Our study helps us understand what minimal conditions are needed for complete transfer of water molecules to another compartment through a nanochannel, which may be of general concern in many fields involving molecular transfer.

Bearing behavior and earth pressure distribution for modified suction caissons in sand under inclined loading

Model tests accompanying numerical analyses on the modified suction caissons (MSCs) in saturated marine sand subjected to inclined loading were conducted to investigate the bearing behavior and earth pressure distribution along the embedded depth. Influences of external structure sizes, inclined loading angles and loading point position on the inclined bearing behavior were discussed. Results show that the inclined bearing capacity significantly decreases with increasing the loading angle when the loading point locates at the outer wall of the internal compartment. It can be also found that the passive earth pressure can resist a considerable portion of the inclined load when the loading point is located at the internal compartment wall. The maximum inclined bearing capacity of MSC is obtained when the loading position locates at the internal compartment outer wall of 2 L 1/3-3L 1/4 below the caisson lid under relatively small loading angle. An equation was proposed to determine the optimum loading point position under different loading angles to obtain the maximum inclined bearing capacity.

A Study on the Establishment of Sprinkler System in Duct Passing through Fire Compartment Walls

The need for a standard review of fire prevention and related statutes and human safety protection against fire spread has emerged owing to the recent diversification of fire types and the increase in the scale of damage in the K-industrial complex's electronic parts manufacturing plant. The building law mitigates the installation of fire dampers (FDs) by fixing sprinkler heads to the inside of the exhaust duct that penetrates the fire compartment wall in the electronic components manufacturing plant. However, the clause presents only alternative applicability and does not present any installation criteria. This results in conflicting interpretations between the Fire Protection Act and the Building Act, causing major confusion in the work. Therefore, in this study, three problems of building legal fire-fighting facilities in electronic parts manufacturing plants with special process characteristics were reviewed and analyzed. In addition, performance standards and standards for inspection and maintenance of building-legal firefighting facilities suitable for preventing the spread of flames were presented.

Age-related efficiency loss of household refrigeration appliances: Development of an approach to measure the degradation of insulation properties

Despite the omnipresence of household refrigeration appliances, there is still a lack of knowledge about their age-related efficiency loss over time. Past studies provide basic evidence for increasing electricity consumption of cooling appliances with ageing but fail to investigate the associated technical wear. Concentrating on the degradation of the thermal insulation, we first determined the ageing process of sealed samples of polyurethane rigid foam by investigating changes in cell gas composition and thermal conductivity over time. Simultaneously, the main challenge was to develop an approach that investigates the age-related efficiency loss of the insulation without its destruction. This testing procedure is referred to as the Bonn method. The non-destructive Bonn method was applied to varying refrigerator models in a series of successive experiments to evaluate the insulation degradation over time. Subsequently, the physical relationship between the test value of the Bonn method and the heat transfer through the multi-layered compartment walls of domestic refrigeration appliances was established, ultimately characterising the degrading insulation in terms of increasing heat transfer. Our results give substantiated evidence that the efficiency loss of cooling appliances is greatly influenced by insulation degradation over time. The ageing of sealed samples of polyurethane rigid foam indicates a large initial increase of thermal conductivity by 15% within the first year, corresponding to a change in cell gas composition. These results are in line with those of the Bonn method, emphasising an increasing heat flow through the multi-layered compartment walls of domestic refrigerators with ageing. Therewith, the present study is of significance to a wide range of stakeholders and forms the basis for future research.

Impact of Flashover Fire Conditions on Exposed Energized Electrical Cords/Cables

There has been prior research exploring the exposure of common electrical cords and cables to fire, but that has traditionally been at the lab scale and under near steady-state exposures. The goal of these experiments was to expose six types of cords and cables in a room-scale compartment with a fuel load sufficient to drive the compartment through flashover. The basic test design was to expose the cords and cables on the floor of a compartment to a growing fire to determine the conditions under which the cord/cable would trip the circuit protection device. All of the cords were energized and installed on a non-combustible surface. The six cables and cords were protected by three different circuit protection devices which were remote from the thermal exposure. This configuration resulted in 18 exposures per experiment. The room fires experiments consisted of three replicate fires with two sofas as the main fuel source, two replicate fires with one sofa as the main fuel source and one fire with two sofas and vinyl-covered MDF paneling on three walls in the room. Each fuel package was sufficient to support flashover conditions in the room. The average peak heat release rate of the sofa fueled compartment fires with gypsum board ceiling and walls prior to suppression was 6.8 MW. The addition of vinyl covered MDF wall paneling on three of the compartment walls increased the pre-suppression peak heat release rate to 12 MW. In each experiment during post flashover exposure, the insulation on the cords and cables ignited and burned through, exposing bare wire. During this period, the circuits faulted. Assessments of both the thermal exposure and physical damage to the cords did not reveal any correlation between the thermal exposure, cord/cable damage, and trip type.

Compartment temperature estimation of a multiple-layer cable tray fire with different cable arrangements in a closed compartment

Fire hazard analysis of multiple-layer cable tray is an important part of nuclear safety analysis. Large-scale cable fire experiments with a three-layer horizontal cable tray were conducted in a closed compartment. The vertical temperature profile in the middle of the room was acquired. Distinctive stratification phenomena were found in the vertical temperature distribution. The interface between the upper and lower layer was located at approximately the height of the top cable layer. Heat transfer between the smoke and compartment walls occurred mainly above the smoke interface. A modified non-steady energy balance model in a closed compartment which included the effect of smoke interface height was used to estimate the compartment temperatures. Compared with the experimental results, the modified model for the multiple-layer cable tray fire in a closed compartment provides better estimation than the original model.

Performance and calibration of two subgrid extinction models for turbulent diffusion combustion in an under-ventilated enclosure fire

The fast-chemistry eddy dissipation combustion model fails to predict abrupt flame self-extinguishment when the oxygen content falls below the critical threshold. To overcome this limitation without recourse to the highly resolved simulations with the detailed chemical mechanisms, the bespoke subgrid extinction model is required. In this work, two subgrid extinction models are implemented in ANSYS Fluent and applied. The first extinction model utilizes conventional critical flame temperature concept, and the second one is the Damköhler number-based approach. The model formulation is used as derived earlier from the perfectly stirred reactor model, with the finite-rate reaction kinetics and radiative heat losses from the unresolved reaction zone.To evaluate model performance and to select optimum model parameters, the burner fire with the constant fuel supply rate (corresponding to the nominal heat release rate 400 kW in complete combustion) is considered in 4x6x4.5 m compartment with the 0.3 m diameter lower air inlet connected to the ambient atmosphere. Conjugate heat transfer at the compartment walls and transient thermal conductivity in the compartment structures are accounted for.Provided that the model parameters are optimized, both extinction models enable prediction of flame self-extinguishing, and the predicted times for flame to extinguish are similar to those recorded in the experiments. For the CFT model, best agreement with the experimental time to flame extinguishment is obtained if the critical flame temperature is set to 1900 K. For the Damköhler number-based approach, the optimum value of 0.25 is found for the model constant in the proportionality relationship between the resolved strain rate and the residence time in the reaction zone, which is not resolved in the simulations.In spite of the similar performance of the two extinction models in the experimental scenario with weakly strained flame, the Damköhler number-based model is expected to be applicable in a wider range of scenarios including highly strained flames such as those affected by strong jets, sprays, and cross-winds.

Spray fire induced gas temperature characteristics and correlations in a ceiling ventilated compartment

Spray fire, one of the common fires, often occurs in ship cabin and results in serious economic loss and casualties. However, there are few literatures [1–3] in terms of compartment spray fire, especially its gas temperature characteristics. Hence, a series of spray fire experiments were conducted in a 2 m × 2 m × 1.88 m ceiling ventilated compartment. It is found that the injecting pressure and ceiling vent size have significant effect on gas temperature. Gas temperature increases with the increase of injecting pressure and the increase in ceiling vent size results in a higher maximum gas temperature. The gas heat gain dominates the total heat transfer. The percentage of gas heat gain decreases with the ceiling vent size while the heat transfer through ceiling vent and compartment walls increases. For estimating the time-dependent average gas temperature in the combustion process, a simplified model was developed according to the thermal analyses, which shows good agreement with experimental data. Furthermore, based on M-Q-H method, a dimensionless analysis was performed for the total average gas temperature rise during the whole combustion process and the corresponding correlation was established, which can be applicable to estimate the gas temperature in ceiling ventilated compartment spray fire scenario.

Fire Performance of Sandwich Panels in a Modified ISO 13784-1 Small Room Test: The Influence of Increased Fire Load for Different Insulation Materials

Four sandwich panel rooms were constructed as prescribed in the ISO 13784-1 test. However, the construction followed normal industry practice, and the panels were also subjected to the kinds of damage typically found in commercial premises, although such damage may not typically be concentrated in such a small room. The fire load was increased to simulate fires actually occurring in commercial premises by stepping up the propane burner output from the usual maximum of 300–600 kW, and by placing a substantial wooden crib in two of the rooms. The results showed significant differences in fire growth rate and burning behaviour between those panels filled with polyisocyanurate (PIR) and those filled with stone wool in both the experiments without and with the wooden crib. Most significantly, the PIR pyrolysis products caused earlier ignition (by radiation from above) of the wooden crib 11 min into the experiment (1 min after the burner was stepped up to 300 kW), whereas the crib ignited 22 min into the test (2 min after the burner had been stepped up to 600 kW, which is beyond the test standard both in time and heat input) for the stone wool panels. This interaction between building and contents is most often ignored in fire safety assessments. After a few minutes, the PIR pyrolysis products that escaped outside the room, from between the panels, ignited. The extra thermal exposure from the PIR-fuelled flames distorted the panels, which in turn exposed more PIR, resulting in large flames on both the inside and outside of the enclosure. From a fire safety perspective this is most important as it shows that with the large fire loads that are commonly found in commercial premises, steel-faced PIR filled panels are not capable of acting as fire barriers, and may support flame spread through compartment walls and ceilings. In addition, the PIR panelled rooms produced very large quantities of dense smoke and toxic effluents, whereas the stone wool panelled rooms produced small amounts of light smoke of lower toxicity. Furthermore, the experiments showed that modifications to the standard test can lead to extremely different outcomes for some of the products. As the modifications simulated real-life situations, it seems important to discuss whether the standard is robust enough for property safety scenarios encountered in industrial premises.

Ambulance Crash in a Rural Area of Thailand

BackgroundAmbulance crashes delay patient transfer and endanger patients, ambulance crews, and other road users. In low- and middle-income countries, where motor vehicle crash rates are typically high, ambulances have a high risk of being involved in a crash. This case report describes an ambulance crash in Thailand to elucidate modifiable problems in current protocols and practices of emergency medical services. Case ReportIn November 2016, a 28-year-old male driver of an ambulance died in a crash while transferring a female patient with dizziness to a rural hospital. The driver and another ambulance crew member were sitting in the front seats unrestrained. The other occupants were in the patient compartment unrestrained. The driver was driving the ambulance within the speed limit. He made a sharp turn trying to evade a dog, and the ambulance crashed head-on into a roadside tree. The cabin sustained severe damage, and the occupants in the patient compartment were struck against the compartment wall and were struck by unsecured equipment and the stretcher. The driver sustained a severe brain injury. The other occupants, including the female patient, sustained minor injuries. Why Should an Emergency Physician be Aware of This?This case raises safety issues concerning the following aspects of ambulance operations in low- and middle-income countries: speed limit, safety device use, seatbelt use, securing equipment, and vehicle safety standards. Systematic measures to change protocols or even legislation, as well as data collection, are required to address these issues.

Mitigation against crude oil wax solidification using TES fin

Crude oil stored in a cold subsea compartmented metal storage tank is constantly undergoing undesirable phase change. Thus, the prevention of the immobile wax formation for the ease of transportation in liquid phase becomes a daunting challenge. We hypothesize that a significant amount of thermal energy could be stored and discharged immediately after complete wax melting via embedded metallic fin(s) in retarding paraffin solidification process and to facilitate sustainable heating and shipment. This study employs the 2D enthalpy-based lattice Boltzmann method (LBM) that is capable of naturally capturing the innate propagation of mushy solid–liquid interface to explore the possibility of using thermal energy storage (TES) fin(s) in reducing the paraffin solidification process within a storage tank. In particular, the effects of cold wall cooling on compartment walls, selected adiabatic material, as well as TES-fin(s) positions and the corresponding aspect ratios to slow down paraffin solidification are discussed. Results show that the present optimized TES-fin configuration is capable of prolonging paraffin solidification by 94% immediately after complete melting. Interestingly, the mushy interface zone propagation rate during the paraffin wax solidification is reduced to a minimum, once the dimensionless length-to-width aspect ratio of TES-fin approaches 1.15 and most importantly, it is strongly position dependent. Overall, the present findings may serve as guidance for the long-term sustainable development in addressing the existing logistic issues on sustainable crude oil shipment from oil platforms.