Small-scale Test Apparatus Research Articles

Experimental evaluation of inelastic dynamic amplification factors for progressive collapse analysis under sudden support loss

A small-scale test setup is devised to investigate the inelastic dynamic amplification factors (DAFs) for structures subjected to sudden support loss. Based on three different definitions, experimental DAFs are calculated from static and dynamic support-release tests. Comparison results indicate that DAFs obtained from the neutral displacement response cannot account for the inelastic dynamic effect on either the displacement or force response. The displacement-based DAFs are apparently different from the force-based DAFs in the inelastic range. The former is larger than 2.0 and exhibits a concave downward variation with displacement ductility. On the contrary, the latter is less than 2.0 and exhibits a concave upward variation. Both of them may asymptotically return to the elastic DAF under large deformation as the specimen presents significant strain-hardening behavior. Pseudo-static response analysis is carried out for prediction of inelastic DAFs using the load–displacement curve obtained from the nonlinear static test. Also, analytical formulae with consideration of post-yield stiffness ratios are derived from the pseudo-static response analysis. They are proved to be capable of simulating the variation of inelastic DAFs with ductility demand.

Description of loading conditions due to violent wave impacts on a vertical structure with an overhanging horizontal cantilever slab

A vertical structure with an overhanging horizontal cantilevering slab is tested in a small-scale test set-up (with a scale factor of 1:20) under loading conditions of violent wave impacts. Tests are conducted using regular waves for different values of water depth and wave period. All the events are recorded by a high speed camera and pressures are measured with 10 Quartz pressure sensors using a 20kHz sampling frequency. A single approaching wave creates two individual impacts which occur sequentially on the vertical and horizontal parts. Both impact pressures and forces are non-repeatable under nominally identical conditions. Beneath the horizontal part, the shock pressures occur even for non-breaking waves which are the result of accelerated water jets along the vertical part. Waves are classified into four breaker types based on Oumeraci et al. (1993). The largest peak pressures are recorded at the still-water level on the vertical part (109kPa) and at the fixed corner of the cantilever slab (123kPa). In addition to these locations, the local pressures measured at the upper corner of the vertical part are also high. Consequently, the presence of a horizontal structural part increases the vulnerability of the vertical structures against violent wave impacts.

Application of Membrane Dehumidifier for Gaseous Trituim Recovery in the LHD

In order to realize the planned deuterium plasma experiments using the Large Helical Device (LHD), the National Institute for Fusion Science (NIFS) is planning to install a system for tritium recovery from exhaust gas. While adopting typical tritium recovery systems, NIFS has also made plans for the development of a compact reduced-waste recovery system by applying a membrane type dehumidifier. A commercially available membrane dehumidifier was evaluated experimentally for this purpose with the results indicating such a membrane is feasible for practical application.A small scale test apparatus having a capacity 1/10th (30 m3/h) that of the actual tritium recovery system with the same flow control system was constructed and its performance evaluated.

Scale‐Up of flat plate photobioreactors considering diffuse and direct light characteristics

This study investigates the scaling of photobioreactor productivity based on the growth of Nannochloropsis salina incorporating the effects of direct and diffuse light. The scaling and optimization of photobioreactor geometry was analyzed by determining the growth response of a small-scale system designed to represent a core sample of a large-scale photobioreactor. The small-scale test apparatus was operated at a variety of light intensities on a batch time scale to generate a photosynthetic irradiance (PI) growth dataset, ultimately used to inform a PI growth model. The validation of the scalability of the PI growth model to predict productivity in large-scale systems was done by comparison with experimental growth data collected from two geometrically different large-scale photobioreactors operated at a variety of light intensities. For direct comparison, the small-scale and large-scale experimental systems presented were operated similarly and in such a way to incorporate cultivation relevant time scales, light intensities, mixing, and nutrient loads. Validation of the scalability of the PI growth model enables the critical evaluation of different photobioreactor geometries and design optimization incorporating growth effects from diffuse and direct light. Discussion focuses on the application of the PI growth model to assess the effect of diffuse light growth compared to direct light growth for the evaluation of photobioreactors followed by the use of the model for photobioreactor geometry optimization on the metric of areal productivity.

Close-range blast loading on empty recyclable metal beverage cans for use in sacrificial cladding structure

This article deals with the experimental and numerical blast study on a single empty recyclable metal beverage can. The idea is to make a macro-foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Close-range free air blast tests have been conducted to understand the crushing behaviour and the energy absorption of a single empty beverage can in detail. To conduct such an air blast test a special small-scale test set-up was designed and manufactured. The effect of skin plate surface area and its nature on the blast parameters is studied. Furthermore, the effect of inertia of the skin plate on the crushing performance of the beverage can is evaluated. Tests have been conducted with different plates (made of aluminium and sandwich composite materials) with different masses which represent the skin plate of the proposed sacrificial structure. The measured blast parameters from the experimental tests were compared with ConWep predicted data. Furthermore, the influence of the finite surface area of the skin plate on the clearing of the reflected pressure waves was also studied. The deformation behaviour and the corresponding energy absorption of empty beverage cans were captured. During the experimental blast tests it was observed that a part of the total reflected impulse (∼30%) was lost before it transfers to the non-sacrificial structure. Hence, in order to investigate this phenomenon Eulerian–Lagrangian coupled analyses were conducted using Hydrocodes. The results from these analyses showed that the diffraction and ground reflected pressure wave caused the loss in impulse. The results from the numerical studies have been compared and validated with the experimental results.

A temperature and mass dependent thermal model for fire response prediction of marine composites

Abstract An accurate assessment of accumulative damage of a composite ship structure subjected to fire is strongly reliant on the accurate characterization of the time dependent temperature distribution within the composite system. Current state-of-the-art analysis tools assume that thermal–mechanical properties of composite structures are independent of temperature change and mass loss. In this paper, a temperature and mass dependent heat diffusion model is developed to characterize the temperature and mass dependent heat conduction, energy consumption resulting from the decomposition, and the energy transfer associated with vaporous migration. The temperature dependent thermal conductivity and specific heat capacity are determined for the composite at a given resin decomposition stage using a recently developed small-scale test apparatus. Given the temperature dependent thermal properties of the fiber and resin materials, the resulting temperature dependent thermal properties of a woven fabric composite are computed from the newly developed thermal–mechanical analysis tool (TMAT). To assess the effect of using single heating rate based mass loss on the composite fire response prediction, the kinetic parameters are obtained from the post-processing of thermogravimetric analysis (TGA) test data conducted at various heating rates. The effects of temperature dependent thermal conductivity, specific heat capacity, and kinetic parameters determined at different heating rates are explored through the application of the temperature and mass dependent fire model to a composite plate subjected to a hydrocarbon fire. The accuracy of the temperature and mass dependent thermal model is demonstrated by comparing its response prediction with available experimental data.

The use of small-scale test data to characterize some aspects of fire fighting foam for suppression modeling

Concerns have been raised about the environmental impact of fluorocarbon-based fire fighting foams. To aid in developing alternative fire fighting foam formulations, fire suppression models are being constructed to evaluate the performance of new, innovative formulations. Some of the input parameters for the fire suppression models are specific to the foam and need to be measured experimentally. A small-scale test apparatus was developed in this study to measure the foam loss mechanisms (i.e., solution evaporated and drained) as well as the time to fuel ignition. In this test, the mass evaporated and drained is continuously measured for a static layer of foam exposed to a fixed irradiance level. The test apparatus was used to quantify the behavior of a single formulation of MIL-SPEC 6% aqueous film-forming foam (AFFF) for a variety of test conditions. Methods for using the data from the small-scale testing in fire suppression models were developed.

Adsorption and desorption of selected VOCs in dust collected on air filters

Adsorption and desorption properties of the dust accumulated on air filters were examined by using a small-scale test apparatus with model compounds. The dust samples were loaded with the model compounds either by adsorption from a constant concentration in air flow or by direct injection into the dust. Desorption was measured at three different relative humidities of air (4–5%, 40–50%, 70–80%). Results indicated that constant relative humidity (RH) of air did not affect the rate of desorption in the test conditions. However, an increase in humidity substantially increased desorption of the model compounds. Similar results were obtained when experiments were conducted using dirty filters without added model compounds. In addition, emission products from clean and dusty filter materials were analyzed at two temperatures (50°C and 100°C) by using an automatic thermodesorption device. The main compounds released were carboxylic acids, aldehydes and terpenes. The emission profiles were similar for the pre-filters and main filters, but the emissions were higher from pre-filters than from the main filters. This result is consistent with the earlier findings of higher odor emissions from pre-filters.

Increasing phenomena of pressure drop during dust removal using a rigid ceramic filter at high temperatures

To analyze the phenomenon of increasing pressure drop during dust removal using a ceramic filter system under high temperature conditions, the pressure drop in an ash powder layer on a ceramic filter during the gas permeation and dust detachment processes was directly measured with a small-scale testing apparatus. Dust detachment behavior of the ash layer on the ceramic filter was evaluated by using both quasi-static and pulse reverse flow methods. Under conditions of relatively low temperatures (below 1050 K), the pressure drop in the gas permeation test was almost fixed, and the maximum pressure drop (Δpmax) at the first detachment of a dust layer by quasi-static reverse flow increased gradually in proportion to temperature. At temperatures higher than 1123 K, a time-dependent increase of pressure difference during gas permeation occurred before dust detachment and a rapid increase of Δpmax during dust detachment was observed. The time-dependent densification of ash layers and a rapid increase of adhesion between ash particles were observed by thermo-mechanical analysis (TMA) and a diametral compression test of ash powder pellets. In this paper, we suggest that the pressure drop increase is controlled by a decrease of pore volume and an increase of fracture strength within the ash layer.

Small-scale evaluation of dump tank sizing methods

Abstract Methods are given for the design of dump tanks to separate the liquid and vapour/gas phases from a two-phase emergency relief discharge from a runaway chemical reactor. A small-scale test apparatus is described which has been used to evaluate the design methods. Results and analysis are given for reacting and non-reacting systems, which give good agreement with the predictions from the design methods for water depressurization and a ‘vapour-pressure’ system. Results for a hybrid system indicate the problems associated with deciding whether the major component of the relief stream is the gas or the vapour.

Design and characterization of an apparatus for agglomeration testing during flash pyrolysis in entrained flow reactors

A small scale test apparatus is developed to measure the relative tendencies of different coals to agglomerate in dilute phase reactors with entrained flow and under conditions of flash pyrolysis. The important variables influencing agglomeration for a given coal are its feed rate and the temperature of pyrolysis. Changes in the method for collecting and measuring agglomerate were not significant at feed rates of dry coal greater than 2.5 g min −1.

Studies of spontaneous combustion in beds of activated carbon

Activated carbon is employed in a nuclear power plant primarily to adsorb and retain traces of fission-product iodine. Whilst most filter units operate in an atmosphere of carbon dioxide some come into contact with air as a consequence of their normal method of usage. Experiments have been performed to identify the parameters likely to affect the self-heating of carbon beds. A small scale test apparatus has been developed in which ignition is achieved by passing heated air upwards through a 25 mm deep bed of material which is supported on a coarse quartz frit. In addition to studying the effects of both the airflow rate and the heating rate on the spontaneous ignition temperature (s.i.t.), the influence of the chemical composition of the bed has been investigated. Potassium iodide (Kl) and triethylene diamine (TEDA) may be added at the manufacturing stage to enhance the I 131 adsorption characteristics of activated carbon. Contamination of the filters by oil or organic (paint) solvents may also occur in practice and, it was suspected, could influence the s.i.t. characteristics of the bed. The results of these experiments are given and discussed with particular reference to the mechanism of interaction between air, carbon and additive/contaminant materials.