Transparent Wall Research Articles

Convection Heat Transfer from Heated Thin Cylinders Inside a Ventilated Enclosure

Experimental study was conducted to determine the effect of velocity of axial fan, outlet vent height, position, area, and aspect ratio (h/w) of ventilated enclosure on convection heat transfer. Rectangular wooden ventilated enclosure having top and front transparent wall was made up of Perspex for visualization, and internal physical dimensions of box were 200 mm × 200 mm × 400 mm. Inlet vent was at bottom while outlet vents were at the side and top wall. Electrically heated cylindrical heat source having 6.1 slenderness ratio was fabricated and hanged at the centre of the enclosure. To calculate heat transfer rates, thermocouples were attached to the inner surface of heat source with silica gel. Heat source was operated at constant heat flux in order to quantify the effect of velocity of air on heat transfer. It was observed that average Nusselt number was increased from 68 to 216 by changing velocity from 0 to 3.34 m/s at constant modified Grashof number i.e. 5.67E+09. While variation in outlet height at the front wall did not affect heat transfer in forced convection region. However, Nusselt number decreased to 5% by changing the outlet position from top to the front wall or by 50% reduction in outlet area during forced convection. Mean rise in temperature of enclosure increased from 8.19 K to 9.40 K by increasing aspect ratio of enclosure from 1.5 to 2 by operating heat source at constant heat flux i.e. 541.20 w/m2.

A novel approach for volumetric solar receiver performance assessments

A novel design and an efficient operation of solar volumetric receivers remain critical for successfully integrating such receivers into solar energy harvesting devices. The performance of the solar volumetric receiver is highly dependent on the geometric connectivity of the actual pore-sites in the SiC open-cell foams. Although the performance of SiC foam receivers has been investigated previously considering the homogeneous foam structure, further studies are needed to explore the influence of the actual path of the pores and their connectivity on the flow and thermal performance of the receiver. Hence, the present study considers the novel design of a solar volumetric absorber incorporating the actual SiC foam receiver geometric features. Accordingly, the thermal and flow behavior of the working fluid within the receiver is examined considering the 3D connectivity of the pore sites. Moreover, the performance of the solar volumetric receiver is evaluated for different Reynolds numbers, solar concentrations, and foam porosities. A 3D-dimensional numerical investigation is carried out incorporating the interactions between convection, conduction, and radiation heat transfer for which the discrete ordinate radiation model is used. Porous SiC foam is placed in a channel having an optically transparent wall at the top and air is used as the working fluid extracting heat from foam. The overall heat transfer coefficient, normalized Nusselt number, and thermal effectiveness are evaluated for various operating conditions. Findings revealed that the receiver thermal performance improves at high Reynolds numbers. The convection heat transfer is found to be the apparent heat transfer mode within the porous SiC foam. In addition, the pumping power to overcome the flow resistance in the channel is considerably less than that of the rate of heat transfer gain.

Energy-efficient design of building facade, inspired by human skin

A great amount of energy consumed is utilised to provide comfort in buildings. Windows (all transparent walls) are one of the factors for waste of energy. This study uses the characteristics of human skin as a protective layer and an interface between the inside and outside of the body to attempt to improve the performance of windows or transparent walls of a building facade. Simultaneously, the process of design and solving the problem is articulated, and the characteristics of human skin are discovered. Then, the traits of human skin are applied to enhance the diverse functions of building facades. Finally, from among more than 15 preliminary designs based on human skin characteristics, a vertical shading system is presented that can control the incoming radiation. The design is evaluated in two modes: controlled by temperature and by the intensity of sunlight. The results show that more than 10% of energy consumption is reduced with movable shading systems. An independent study of energy consumption for cooling, heating and lighting shows it is more reasonable to use the temperature-controlled shading system, which can save 23–25% of the annual cost of energy.

An Improved Empirical Model for Estimating the Geometry of the Soil Wetting Front with Surface Drip Irrigation

Wetting pattern geometry is useful in determining the spacing between emitters and the irrigation time in drip irrigation systems. This research aimed to generate an empirical model to estimate the width and depth of the wetting front in surface drip irrigation based on experimental tests in a cube-shaped container with transparent walls in soils with a sandy clay loam texture, with hydraulic conductivities from 2.316 to 3.945 cm h−1, and organic matter contents from 1.7 to 2.8%, and different irrigation conditions: discharge rates of 1.44, 2.90, 3.00, 3.75, and 4.00 L h−1, initial moisture levels between permanent wilting point and field capacity, and irrigation times from 0.58 to 9.50 h. The experimental conditions and the strategy for measuring the wetting front and soil moisture are detailed so the experiment is verifiable. The proposed model performed better than five other empirical models, with average values of 3 cm for the root mean square error and 0.88 for the Nash and Sutcliffe efficiency coefficient. The generated model is efficient and simple and can be a very useful tool for the design and operation of surface drip irrigation systems in soils with conditions similar to those of this study.

Effects of separated pair housing of female C57BL/6JRj mice on well-being

In laboratory animal facilities, it is a common code of practice to house female mice in groups. However, some experimental conditions require to house them individually, even though social isolation may impair their well-being. Therefore, we introduced a separated pair housing system and investigated whether it can refine single housing of adult female C57BL/6JRj mice. Individually ventilated cages (IVC) were divided by perforated transparent walls to separate two mice within a cage. The cage divider allowed visual, acoustic, and olfactory contact between the mice but prevented interindividual body-contact or food sharing. Short- and long-term effects of the separated pair housing system on the well-being of the mice were compared with single and group housing using a range of behavioral and physiological parameters: Nest building behavior was assessed based on the complexity of nests, the burrowing performance was measured by the amount of food pellets removed from a bottle, and trait anxiety-related behavior was tested in the free exploratory paradigm. For the evaluation of the ease of handling, interaction with the experimenter's hand was monitored. Social interaction with unknown conspecifics and locomotor activity were investigated in a test arena. Moreover, body weight and stress hormone (metabolites) were measured in feces and hair. After the mice spent a day under the respective housing conditions, concentrations of fecal corticosterone metabolites were higher in separated pair-housed mice, and they built nests of a higher complexity when compared to single-housed mice. The latter effect was still observable eight weeks later. In week 8, separated pair-housed mice showed less locomotor activity in the social interaction arena compared to mice from the other housing systems, i.e., single and group housing. Regardless of the time of testing, pair housing improved the burrowing performance. Separated pair-housed mice were more difficult to catch than group-housed mice. Hair corticosterone, progesterone, and dehydroepiandrosterone concentrations changed with increasing age independently of the housing system. There were no effects of the housing systems on trait anxiety-related behavior in the free exploratory paradigm, voluntary interaction with the experimenter’s hand, and body weight. Overall, the transfer to the separated pair housing system caused short-term stress responses in female C57BL/6JRj mice. Long-term effects of separated pair housing were ambiguous. On one hand, separated pair housing increased nesting and burrowing behavior and may therefore be beneficial compared to single housing. But on the other hand, locomotor activity decreased. The study underlined that the effects of the housing conditions on physiological and behavioral parameters should be considered when analyzing and reporting animal experiments.

Three-Dimensional Physical Similarity Simulation Experiments for a Transparent Shaft Coal Pocket Wall in Coal Mines.

To explore the variations of the loading, deformation, and loss and to determine the mechanical state, loss characteristics, and stability for the shaft coal pocket wall in coal mines under a dynamic-static load, this paper innovatively attempts to conduct a three-dimensional physical similarity test of a transparent material shaft coal pocket, as well as the experiments of loading and unloading coal in the shaft coal pocket using different bulk storage materials 80 times. Then, the deformation, pressure, the surrounding rock, and the flow pattern of the silo wall were discussed considering the existence of the warehouse wall support. The characteristics of shaft wall deformation and surrounding rock stress cracks during the unloading were analyzed with the help from multiple integrated test systems such as strain gauges, pressure sensors, borehole peeps, and other comprehensive test systems. The results indicated that different dispersion particles have a significant impact on the strain of the shaft wall. When using the coal particles as storage materials, the overpressure coefficient of the shaft wall is up to 1.95 times higher than using dry sand particles. The particle size and internal friction angle of the bulk particles impact significantly on the deformation of the wall, where the cohesive force among the dispersed particles produced by the compaction effect has a certain influence on the side pressure of the silo wall. During the unloading process, coal particles were easier to obtain an arching phenomenon than dry sand particles. In addition, the number of bulk arching could be significantly reduced under the conditions of the warehouse wall support. The “weak rock stratum” in the surrounding rock plays a major role in controlling the deformation and failure development of the shaft wall. The three-dimensional physical simulation experiment of the transparent shaft wall truly reproduces the field engineering practice, and the physical simulation results are verified by numerical simulation analysis.

미세 입자 분리를 위한 유체 채널 내 폴리머 벽을 포함한 음파영동 디바이스의 제작

In this paper, we propose acoustophoretic microfluidic devices with an acoustic transparent polymer wall using a simple and low-cost fabrication method followed by MEMS (Micro-Electromechanical Systems) processes. Generally, due to the acoustic standing wave between two opposing walls in microfluidic channel, the particle focusing lines are fixed according to the applied frequency. In the proposed device, however, it is possible to place the particle focusing lines in the arbitrary position within the fluidic domain through the optimized width of polymer wall. The PDMS (Polydimethylsiloxane) mold with thin layer was used as the sealing layer between the Si substrate and cover glass, as well as the decoupling layer between the acoustic boundary and fluidic boundary. The thickness of PDMS mold needed to be minimized to decrease the heating by the acoustic energy absorption of PDMS layer, which was successfully made using the spin-coating of PDMS and the UV tape transfer method. The acoustophoretic device with thin PDMS layer and optimized width of PDMS wall can be applied, for biotechnological applications such as the separation of blood cells and micro-particles.

Investigation of convection and radiation heat transfer of paraffinic materials and storage of thermal energy in melting process of PCMs in the cavity with transparent inner walls

Phase change materials have wide applications as thermal energy storage systems. Due to the low thermal conductivity of these materials, lots of efforts have been made to increase the thermal conductivity and efficiency of thermal energy storage systems. In this numerical study, convective and radiation heat transfer on a cavity with transparent inner walls have been investigated considering the effects of buoyancy force and viscosity of phase change materials. For this purpose, computational fluid dynamics that have high accuracy in calculations have been used. The considered wall is made of brick, in which the cavity containing phase change materials is included and layers of cement and plaster are placed on the wall. The results indicate that increasing the heat flux increases the effects of convective heat transfer. In addition, by applying radiation effects, the melting process of paraffin materials increases by 31%. Due to the transparency of the inner walls of the cavity, the radiation process occurred surface to surface. Therefore, with increasing amount of molten material, the radiation effects increase, the reason for this is that RT24 material is more transparent in liquid form than solid material. Also, increasing the heat flux from 50 to 100 and 300 (w/m2) increases the speed of the melting process by 19.3% and 27.2%, respectively.

A machine learning approach to determine bubble sizes in foam at a transparent wall

This article describes the use of a machine learning based technique to measure the bubble sizes of foam with polyhedral bubble shape in contact with a transparent wall. For two different experimental cases images are obtained of foam in a cylindrical column and labeled with a classical image processing algorithm. An available neural network based model, initially designed for cell image applications, is trained and validated to segment the images. When comparing the bubble size distribution in images found using the trained model with manually segmented images a good agreement over a large range of diameters can be found. The error of the mean diameter in both cases lies below , mostly attributed to the failed recognition of tiny round bubbles in dry foam. The trained model is provided for further usage.

Mixing and segregation of spheres of three different sizes on a batch stoker grate: Experiments and discrete element simulation

Mixing and segregation in a tri-disperse granular assembly of polyoxymethylene (POM) spheres induced by the moveable stoking bars of a generic batch grate system are examined. Each particle size class features a separate colour. Stroke bar velocity and stroke length are varied. Different moving modes of the bars are analysed. Optically transparent walls of the grate allow for the localization of the visible particles. Based on the visible particle positions a segregation index is calculated. The initial arrangement of the particles in the experiments, which exhibits small statistical differences introduced by the grate filling procedure, has an influence on the progression of the segregation index. The experiments are compared with discrete element (DEM) simulations employing an in-house DEM code.Experiments are in good general agreement with the simulations. The particle rearrangement during bar movement is characterized by an initially fast mixing on short time-scales and a slow process to reach a final state of segregation. These two processes are influenced by the penetration depth of the bars into the bed and the specific movement mode.Three modes predominantly showed segregation in the direction of bar movement, whereas two modes showed large-scale spatial particle rearrangement. Two moving modes show bridging at the beginning of the experiments, an effect that could be reproduced by the DEM simulations. The influence of the modes and their specific parameters on segregation indices, a mixing rate and a segregation efficiency are discussed in detail.

Kisspeptin is Testosterone independent regulator of Sexual Motivation in Male Rats

Kisspeptin is the peptide product of the KISS-1 gene and endogenous agonist for the Kiss1 receptor. It is well known that kisspeptin acts centrally, and stimulates the secretion of gonadoliberin (GnRH). Further, Kisspeptin also interacts with other neuropeptides such as neurokinin B and dynorphin to regulate GnRH pulse generation and plays a key role in sexual behavior. This study aimed to evaluate the effect of kisspeptin on male rats' sexual motivation and its dependence on testosterone levels. In this study total of 50 copulation naive male Wistar rats were collected and divided into 5 groups (10 rats in each group), among these first group received only saline (control), the second group has been given 20μg buserelin acetate (GnRH analogue), the third group has been given intranasally kisspeptin-10 (3ng), the fourth has been received intraperitoneally kisspeptin-10 (30ng) and the fifth group has been given Yoquimbine 200 µg. Behavioral effects were registered in the open-field reward-proximity chamber with a female in the estrous phase of the cycle over the transparent perforated wall for 10 minutes in red light. Blood samples were collected from the tail vein after 30 minutes of the substance administration and in the collected blood samples, testosterone concentration was measured by the ELISA method. All animal groups were compared with each other by the ANOVA test and correspondent “post hoc” paired tests of Newman–Kruskall– Wallis test and Dunn’s test. Intranasal administration of buserelin acetate increased the concentration of testosterone but did not affect sexual motivation in rats. Further, intraperitoneal administration of Kisspeptin-10 enhances testosterone concentration and sexual motivation. While intranasal administration of kisspeptin-10 didn’t enhance testosterone level but increased sexual motivation. Results of this study showed some effects of kisspeptin along with the independent regulation of steroids.

Bubble‐scale observations of polyurethane foam expansion

AbstractWe describe experiments designed to inform computational models of the dynamic filling process of chemically blown, polyurethane foams, especially subgrid models to predict bubble size affecting foam properties. Three experimental methods are used to observe the evolution of bubble sizes during blowing. Magnified views of bubbles at a transparent wall of a channel are recorded during the foaming. The bubble sizes in the final frame after the expansion has stopped are compared to scanning electron microscope images of the interior of the cured samples to determine wall effects. In addition, diffusing wave spectroscopy is used to determine the average bubble sizes across the width of a similar channel during foam expansion. We conclude that the bubble size distribution is dependent on the formulation of foam being tested, temperature, the height in the foam bar, the proximity to a wall, and the degree of overpacking.

RideVR: Reducing Sickness for In-Car Virtual Reality by Mixed-in Presentation of Motion Flow Information

Humans spend a significant portion of their daily life in cars. In this study, we investigate a method to reduce motion sickness and allow people to use virtual reality (VR) while riding in cars. As the sickness arises primarily from the sensory conflict between visual and actual (or vestibular) motions, the proposed approach attempts to resolve the mismatch by mixing in and visualizing the estimated information of the actual motion, which is sensed by the on-board diagnostics and inertial measurement unit modules attached to the vehicle. We conduct a pilot experiment to validate our approach by comparing the sickness levels before and after implementing the approach in three in-car VR usage conditions: (1) Default – using the VR content without modification; (2) transparent wall – using the VR content with its background scene changing depending on the car motion; (3) particle flow – mixing in the VR content with the estimated motion flow of the car visualized as moving particles. Our experimental results show that motion sickness is reduced significantly (but not eliminated to a negligible level) using our approach.

Analysis of vertical distribution differences of global stratospheric ozone based on weighted multiplication algebraic algorithm

Global climate change and the formation of the Antarctic ozone hole have prompted people to pay attention to the changes in atmospheric ozone content. The global continuous observation of ozone is achieved by retrieving the global total column concentration from nadir satellite data. In this work, the weighted multiplication algebraic algorithm is combined with the radiative transfer model SCIATRAN, by using the 2011 Chappuis-Wulf band SCIAMACHY limb radiation data to retrieve the stratospheric ozone profile between 15- and 40 km altitude, solving the ozone global stratified observation problems. In the ozone global stratification map, the whole process of the global transmission of ozone formed in low latitude regions to high latitude regions is observed, which is directly related to the Brewer-Dobson circulation. During the most severe period of the Antarctic ozone hole from September to October, the Antarctic polar vortex has an obvious hindering effect on ozone transmission, and the polar vortex has a “transparent wall” effect. On the one hand, it is difficult to transfer ozone from the equatorial region to the Antarctic region for replenishment. On the other hand, the retention of ozone-depleting substances over the Antarctic region leads to the acceleration of ozone depletion, and the combination of low replenishment and high depletion contributes to the Antarctic ozone hole. Compared with the global total column concentration of ozone, the observation of global ozone stratification is very valuable for scientific research and will promote the detailed study of the whole process of ozone formation, transmission, and consumption.

Study on 3D Motion Mixer with Sealed Container

3D motion mixer is designed for mixing by rotating a sealed vessel without inserting any blades or other parts into the stirring tank, so that no foreign objects can be mixed inside the container during stirring. However, as the process and state of stirring of the sample inside the container was unknown, therefore, operating conditions such as rotation speed and filling rate were dependent on experience. In this study, a transparent container was used to reveal the flow state of the powder interface inside the rotating container. Spatial analysis methods were applied to the positional information in the recorded images of fluorescent particles distributed near the transparent vessel wall through visualization experiments using UV fluorescent particles to clear the stirring process and to evaluate the dispersion state.

The effect of the filling degree of the tumbling mill chamber on the bifurcation value of the froude number

The influence of the filling degree of the drum chamber on the bifurcation value of the Froude number in the case of self-excitation of self-oscillations of a two-fraction granular charge with a minimum swing is considered. Such a pulsating mode of the charge movement is used in the self-oscillating grinding process in a tumbling mill. The coarse fraction that simulated the milling bodies consisted of spherical particles of an incoherent granular material with a relative size in the chamber ψb=0.00733. The fine fraction, simulating the material to be ground, was cement with a relative particle size ψm≈0.092∙10-3. The value of the adopted analogue of the kinematic viscosity of the two-fraction granular loading approached the value of 10-3 m2/s. The main variable factor in experimental studies was the filling degree of the drum chamber with loading at rest κb=0.25, 0.35, and 0.45. An additional factor was the degree of filling the gaps between the spherical particles of the coarse fraction with particles of the fine fraction κb=0, 0.25, 0.5, and 1. The method of visual analysis through the transparent end wall of the chamber of transient processes of the loading behavior with a smooth change and fixation of the velocity was applied. The bifurcation minimum value of the rotation speed was recorded, at which the steady-state circulation mode of the load movement turns into a transient pulsation one with a minimum swing. A decrease in the bifurcation values of the Froude number Frb on the cylindrical surface of the chamber with an increase in κb has been established. An increase in the intensity of the decrease in Frb with an increase in κm was revealed. The recorded effect is due to an increase in the connected properties of a two-fraction loading during self-excitation of self-excited oscillations with an increase in κb and κm. The numerical values of the boundaries of the range of bifurcation values of the Froude number for a tumbling mill Frb=0.0484–1.17 have been determined. The obtained Frb range corresponds to the Reynolds value in the range Re=40–197. The maximum Frb value is obtained with coarse grinding. An increase in the likelihood of self-excitation of self-oscillations of the intra-chamber loading with a decrease in the fineness of grinding was revealed

Carbon as a solution for nanocellular foam superinsulation

This work demonstrates the substantially improved thermal radiation blocking capability of polymer foams with the utilization of carbonaceous nanoparticles to overcome the limitation of the nanocellular foam's thermal insulation capability to achieve superinsulation. Without carbon, the radiation heat transfer becomes extremely high through thin and transparent cell walls and struts of the low-density nanocellular foams. However, this high radiative heat transfer can be successfully reduced by incorporating multi-walled carbon nanotubes (MWCNTs). The effect of carbon on heat transfer in foams was mathematically modelled and experimentally verified. The model includes contributions of thermal transport through conduction and radiation, while convection is negligible. The effects of MWCNTs on thermal conductivity, refractive index, absorption index, dielectric permittivity and dielectric loss of the solid were studied using two examples of polystyrene/MWCNT and PMMA/MWCNT nanocomposite foams. It was found that, with carbon, the radiation blocking capability is significantly improved and nanocellular foams could achieve superinsulation level through the Knudsen effect. The optimal cellular structure at which heat transfer is minimized was investigated with the aim of manufacturing superinsulation. The foam's total heat transfer decreased while the optimal expansion ratio increased with the filler content, which is preferable for manufacturing high performance insulation with less polymer.

Effects of hydrogen-addition on the FREI dynamics of methane/oxygen mixture in meso-scale reactor

FREI (Flame with Repetitive Extinction and Ignition) is a unique flame dynamic in the micro or meso combustor due to the scale effect of the combustor. To further understand the flame dynamics of the FREI, the flame propagating process of the methane-oxygen premixed gas with hydrogen addition is visualized and analyzed experimentally in a rectangle combustor with transparent wall. The equivalence ratio regimes of different flame behaviors are obtained by varying the hydrogen addition. The effect of hydrogen addition on the flame propagation speed, the flame amplitude and the frequency of the FREI is discussed in terms of methane and hydrogen properties, as well as combustor wall temperature. The results indicate that increasing the hydrogen addition will enlarge the amplitude and decrease the frequency of the FREI. However, the effects of hydrogen addition on the flame properties in the upstream and downstream parts of the combustor vary. When the hydrogen addition is increased under the FREI condition, the temperature profile becomes more uniform upstream. Meanwhile, the flame propagates faster with higher hydrogen addition. However, due to the combined effect of wall temperature and the hydrogen property, increasing the hydrogen addition will decrease the wall temperature and the flame propagating velocity at the downstream part when the equivalence ratio is less than 1.9.

Application of physical theory of cavity in the construction of double skin facades

Abstract The article deals with the issue of double skin transparent facades as a new technological-operational system of transparent exterior walls. Especially of high-rise buildings, which with its operating modes ingeniously uses a renewable source of solar energy to reduce the energy needs of the building. The basic precondition for the correct function of the double skin facade is its functional aerodynamics in any climatic conditions of the outdoor climate. In the critical state of windlessness, the aerodynamic quantification of a double skin facade is the total aerodynamic resistance of the cavity, which consists of the aerodynamic frictional resistances along the length of the air flow line and local aerodynamic resistances of the cavity. The article analyses the functional aerodynamics on two frequented types of double skin facades with a narrow type and corridor type cavity. At the end it confronts functional aerodynamics with the results of their temperature, aerodynamic and energy regime obtained from in-situ experiments.

Visualization of hydrodynamic and physico-chemical processes in rotating and vibrating containers

Variable inertial fields are an efficient way to control the behaviour of hydrodynamic systems. Forces of inertia can be used, for example, to stabilize or destabilize systems with an interface or density gradient, to mix multiphase or non-isothermal fluids. The implementation of this approach means that liquids fill the periodically moving containers. In this paper, the situations are considered when the containers perform either rotation or translational vibrations. Methods for measuring the density and velocity fields of convective flows in reacting hydrodynamic systems are described. Interferometry is used to visualize the density distribution. Particle image velocimetry (PIV) is used to study the structure and velocity of the flows. Optical instruments are installed stationary in the laboratory system. For video recording, a camera shutter is synchronized with the motion of a container, and thus the images are captured in a fixed phase of oscillations or rotation. Constructions of the containers make it possible to illuminate the working volume through transparent walls at different angles or in different planes. They also provide a compensation for the centrifugal pressure and allow interference cells to be used in overload conditions. The successful application of the methods in experimental studies of chemo-hydrodynamic processes is demonstrated.