Search Results (13)

Aquaporin 1 is a membrane water channel protein, which was studied here in spiny dogfish (Squalus acanthias) osmoregulatory tissues using a variety of techniques. The cloning of aquaporin 1 (AQP1) in the spiny dogfish identified a splice variant version of the mRNA/protein (AQP1SV1/AQP1SV1). Polymerase chain reaction (PCR) in a range of tissues showed AQP1 to be expressed at very high levels in the rectal gland with ubiquitous mRNA expression at lower levels in other tissues. Northern blotting showed that AQP1 had a mRNA size of 5.3 kb in kidney total RNA. The level of AQP1 mRNA was significantly lower in the rectal glands of fish acclimated to 120% seawater (SW; vs. 75% SW (p = 0.0007) and 100% SW (p = 0.0025)) but was significantly higher in those fish in the kidney (vs. 100% SW (p = 0.0178)) and intestine (vs. 75% SW (p= 0.0355) and 100% SW (p = 0.0285)). Quantitative PCR determined that AQP1SV1 mRNA levels were also significantly lower in the rectal glands of both 120% (p = 0.0134) and 100% SW (p = 0.0343) fish in comparison to 75% SW-acclimated dogfish. Functional expression in Xenopus oocytes showed that AQP1 exhibited significant apparent membrane water permeability (p = 0.000008–0.0158) across a range of pH values, whereas AQP1SV1 showed no similar permeability. Polyclonal antibodies produced against AQP1 (AQP1 and AQP1/2 antibodies) and AQP1SV1 had bands at the expected sizes of 28 kDa and 24 kDa, respectively, as well as some other banding. The weak AQP1 antibody and the stronger AQP1/2 antibody exhibited staining in the apical membranes of rectal gland secretory tubules, particularly towards the periphery of the gland. In the gill, the AQP1/2 antibody in particular showed staining in secondary-lamellar pavement-cell basal membranes, and in blood vessels and connective tissue in the gill arch. In the spiral valve intestine side wall and valve flap, the AQP1/2 antibody stained muscle tissue and blood vessel walls and, after tyramide signal amplification, showed some staining in the apical membranes of epithelial cells at the ends of the luminal surface of epithelial folds. In the rectum/colon, there was also some muscle and blood vessel staining, but the AQP1 and AQP1/2 antibodies both stained a layer of cells at the base of the surface epithelium. In the kidney convoluted bundle zone, all three antibodies stained bundle sheath membranes to variable extents, and the AQP1/2 antibody also showed staining in the straight bundle zone bundle sheath. In the kidney sinus zone, the AQP1/2 antibody stained the apical membranes of late distal tubule (LDT) nephron loop cells most strongly, with the strongest staining in the middle of the LDT loop and in patches towards the start of the LDT loop. There was also a somewhat less strong staining of segments of the first sinus zone nephron loop, particularly in the intermediate I (IS-I) tubule segment. Some tubules appeared to show no or only low levels of staining. The results suggest that AQP1 plays a role in rectal gland fluid secretion, kidney fluid reabsorption and gill pavement-cell volume regulation and probably a minor role in intestinal/rectal/colon fluid absorption. Full article

The spiral concentrator is usually the first operation in the combined process of iron ore beneficiation. The industrial separation index decreases as the trough surface undergoes increased wear. A combination of surface roughness measurement and numerical experimental methods is utilized to systematically investigate the effect of wall roughness in the middle zone on the evolution of the flow field of a slurry consisting of hematite, quartz and water in a spiral concentrator. The radial migration and distribution characteristics of hematite and quartz particles are analysed, and the separation indexes are further evaluated. The results show that an increase in wall roughness (K_s value) in the middle zone has been shown to decrease the depth of slurry flow, the velocity and radial flux of secondary flow in the inner and middle zones of the trough, and to narrow the space of inward flow. The variation in hydrodynamic parameters is particularly pronounced as the K_s value increases from 0.1 mm to 0.2 mm, resulting in a significant reduction in the space available to the separation fluid and an observable interruption in the inward flow. The migration tendency of hematite and quartz particles to the inner trough is reduced depending on the flow field parameters, and their enrichment zones are both shifted outward. The migration amount and distance of particles show apparent differences in density and size. The separation indexes decrease slightly as the wall roughness (K_s value) in the middle zone increases in the 0.01 to 0.1 mm range, but the iron grade of concentrate decreases significantly, and the separation effect worsens as the K_s value increases from 0.1 mm to 0.2 mm. The separation effect of hematite and quartz particles in the spiral concentrator is influenced by the comprehensive interaction of feed size and wall roughness in the middle zone. The results of this study provide a theoretical basis for the selection of trough material, surface structure design and the production process control of the spiral concentrator. Full article

To meet the Chinese government’s energy-saving and emission-reduction policies, flexible peak regulation is necessary for traditional coal-fired boilers. Flexible peaking leads to large changes in boiler load, which affects the safety of the boiler water wall. In this paper, a 1000 MW ultra-supercritical unit was tracked for three years, and effective data were selected to study the temperature characteristics of the water wall under flexible peak regulation. The results show that the lower the load, the greater the temperature fluctuation of the water wall. The temperature distribution of the spiral water wall is more uniform. The position of the temperature valley value of the rear spiral water wall was found, and the load of more even temperature distribution was also found. The temperature change of the front vertical water wall was the most complex of all the water walls. The 643.9 MW load case showed different behavior to the temperature distribution of the water wall. The side water walls were heated evenly under the different loads. The characteristics of the temperature distribution of the side vertical water wall were found through statistical analysis. The fitting equation for the change rule of the temperature is presented. The higher the load, the better the equations. Finally, this paper gives some advice on how to avoid temperature deviation in the water wall, and the detailed research highlights the safe running of water walls. Full article

Sediment erosion damage is one of the main causes of structural failure in reaction turbine units. To study the mechanism through which sediment erosion affects the water-guiding mechanism of a reaction turbine unit, this study obtained the average concentration and particle size of sediment during the flood season based on the statistics of the measured sediment data from the power station. Additionally, the characteristics of the solid–liquid two-phase flow of the diversion components of the reaction hydraulic turbine were numerically calculated. Based on the velocity triangle change in the guide apparatus and the flow similarity principle, a flow-around wear test device for the guide apparatus of the reaction turbine was designed. Furthermore, the similarity of the sand–water flow field between the guide apparatus of the prototype unit and the test device was compared and analyzed. The results demonstrated that the sand–water flow field of the diversion components of the prototype unit was axisymmetric and exhibited a potential flow distribution. Additionally, uniform sand–water flow occurred within the guide apparatus, with a small sand–water velocity gradient near the wall of the stay vanes (SV) and the guide vanes (GV). The maximum volume fraction of sediment particles was observed in the tailing area of the spiral casing, indicating an enrichment phenomenon of sediment particles. The velocity of the sediment particles on the surface of the guide vane in the single-channel sediment wear test device and prototype unit ranged from 6.2 to 7.8 m/s, and the velocity of the sediment particles on the surface of the stay vane ranged from 5.1 to 14.6 m/s, and the difference of the sediment particles’ velocity near the wall was 1 to 3 m/s. The trailing vorticity of the guide vane reached a maximum of 120 s⁻¹. Consequently, the single-channel sediment erosion test device can unveil the sediment erosion mechanism of the guide apparatus of a reaction turbine. Full article

Carnivorous plants are mixotrophs that have developed the ability to lure, trap, and digest small organisms and utilize components of the digested bodies. Leaves of Drosophyllum lusitanicum have two kinds of glands (emergences): stalked mucilage glands and sessile digestive glands. The stalked mucilage glands perform the primary role in prey lure and trapping. Apart from their role in carnivory, they absorb water condensed from oceanic fog; thus, plants can survive in arid conditions. To better understand the function of carnivorous plant emergences, the molecular composition of their cell walls was investigated using immunocytochemical methods. In this research, Drosophyllum lusitanicum was used as a study system to determine whether cell wall immunocytochemistry differs between the mucilage and digestive glands of other carnivorous plant species. Light and electron microscopy were used to observe gland structure. Fluorescence microscopy revealed the localization of carbohydrate epitopes associated with the major cell wall polysaccharides and glycoproteins. The mucilage gland (emergence) consists of a glandular head, a connecting neck zone, and stalk. The gland head is formed by an outer and inner layer of glandular (secretory) cells and supported by a layer of endodermoid (barrier) cells. The endodermoid cells have contact with a core of spongy tracheids with spiral-shaped thickenings. Lateral tracheids are surrounded by epidermal and parenchymal neck cells. Different patterns of cell wall components were found in the various cell types of the glands. Cell walls of glandular cells generally are poor in both low and highly esterified homogalacturonans (HGs) but enriched with hemicelluloses. Cell walls of inner glandular cells are especially rich in arabinogalactan proteins (AGPs). The cell wall ingrowths in glandular cells are significantly enriched with hemicelluloses and AGPs. In the case of cell wall components, the glandular cells of Drosophyllum lusitanicum mucilage glands are similar to the glandular cells of the digestive glands of Aldrovanda vesiculosa and Dionaea muscipula. Full article

This article deals with the numerical simulation of an oil–air multiphase flow inside the thrust bearing of a high-performance mixed-flow pump, including both the lubrication effects and the cooling of the oil by the water-cooling system based on spiral piping. The bearing is lubricated by the oil bath method with partially submersed rollers. Very complex full 3D geometry is modelled in all details, but for modelling purposes, the impacts of some model simplifications on the results are tested. The comprehensive CFD analysis is based on fully transient simulations, taking into account the different rotational speeds and different coordinate systems of all rotating components. The oil distribution on the bearing ring and roller walls as well as the oil temperature are discussed in detail. The results demonstrate that the designed cooling system is efficient in keeping the bearing and oil temperatures at safe values to guarantee bearing rating life even at extreme climatic conditions. The simulations present a comprehensive way of solving complex problems of the bearing and its cooling system applicable to engineering practice. The results of the simulations indicate also that the complexity of the computational domain and bearing clearances have a significant impact on the obtained results. Full article

Space cooling energy consumption in residential buildings has tripled globally over the past three decades, leading to a significant increase in greenhouse gas (GHG) emissions and building operating costs. To reduce building cooling energy consumption, cooling energy can be recovered from domestic cold water (DCW) for space cooling by circulating DCW through thermally massive walls (herein “DCW-wall”) before regular household consumption (e.g., showers). This approach is more effective in cold climate regions since the DCW is cooler in these regions, yet its engineering design and effectiveness have not been evaluated previously. This study evaluated the cooling potential of DCW-walls in different operation scenarios (e.g., inlet temperatures, zone temperatures, and piping configurations). A typical DCW usage pattern and a daily amount of 1200 L were selected for evaluation. Three-dimensional transient thermal simulations were used to obtain the water outlet temperatures, average wall surface temperatures, and cooling potentials. The results showed that a DCW wall with a spiral piping configuration and DCW inlet at 12 °C can deliver 21.92 MJ of cooling energy daily to a zone at 25 °C. This amount of free energy can cover up to approximately 11% of the annual cooling energy demand of a four-person dwelling in Toronto, Canada, which has a warm and humid summer. Full article

In recent years, high permeability membranes (HPMs) have attracted wide attention in seawater reverse osmosis (SWRO) desalination. However, the limitation of hydrodynamics and mass transfer characteristics for conventional spiral wound modules defeats the advantage of HPMs. Feed spacer design is one of the effective ways to improve module performance by enhancing permeation flux and mitigating membrane fouling. Herein, we propose a multiscale modeling framework that integrates a three-dimensional multi-physics model with a permeable wall and an impermeable wall, respectively, at a sub-millimeter scale and a system-level model at a meter scale. Using the proposed solution framework, a thorough quantitative analysis at different scales is conducted and it indicates that the average errors of the friction coefficient and the Sherwood number using the impermeable wall model are less than 2% and 9%, respectively, for commercial SWRO membrane (water permeability 1 L m⁻² h⁻¹ bar⁻¹) and HPMs (3 L m⁻² h⁻¹ bar⁻¹, 5 L m⁻² h⁻¹ bar⁻¹ and 10 L m⁻² h⁻¹ bar⁻¹) systems, compared to the predictions using the permeable wall model. Using both the permeable and impermeable wall models, the system-level simulations, e.g., specific energy consumption, average permeation flux, and the maximum concentration polarization factor at the system inlet are basically the same (error < 2%), while the impermeable wall model has a significant advantage in computational efficiency. The multiscale framework coupling the impermeable wall model can be used to guide the efficient and accurate optimal spacer design and system design for HPMs using, e.g., a machine learning approach. Full article

The purpose of the present work was to determine the thermal performance of borehole heat exchangers, considering the influences of their geometric configurations and the thermophysical properties of the soil, grout and pipe wall material. A three-dimensional model was developed for the heat and mass transfer in soil (a porous medium) and grout, together with one-dimensional conductive heat transfer through the pipe walls and one-dimensional convective heat transfer of the heat transfer fluid circulating in the pipes. An algorithm was developed to solve the mathematical equations of the model. The COMSOL Multiphysics software was used to implement the algorithm and perform the numerical simulations. An apparatus was designed, installed and tested to implement the thermal response test (TRT) method. Two wells of depth 50 m were drilled in the Almaty region in Kazakhstan. Gravel and till/loam were mainly found, which are in accordance with the stratigraphic map of the local geological data. In each well, two borehole heat exchangers were installed, which were an integral part of the ground source heat pump. The TRT measurements were conducted using one borehole heat exchanger in one well and the data were obtained. The present TRT data were found to be in good agreement with those available in literature. The numerical results of the model agreed well with the present TRT data, with the root-mean-square-deviation within 0.184 °C. The TRT data, together with the predictions of the line-source analytical model, were utilized to determine the soil thermal conductivity (${\lambda }_g$ = 2.35 W/m K) and the thermal resistance of the borehole heat exchanger from the heat transfer fluid to the soil ($R_b$ = 0.20 m K/W). The model was then used to predict the efficiencies of the borehole heat exchangers with various geometric configurations and dimensions. The simulation results show that the spiral borehole heat exchanger extracts the highest amount of heat, followed by the multi-tube, double U-type parallel, double U-type cross and single U-type. It is also found that the spiral configuration can save 34.6% drilling depth compared with the conventional single U-type one, suggesting that the spiral configuration is the best one in terms of the depth and the maximum heat extracted. The simulation results showed that (i) more heat was extracted with a higher thermal conductivity of grout material, in the range of 0.5–3.3 W/m K; (ii) the extracted heat remained unchanged for a thermal conductivity of pipe material higher than 2.0 W/m K (experiments in the range of 0.24–0.42 W/m K); (iii) the extracted heat remained unchanged for a volumetric flow rate of water higher than 1.0 m³/h (experimental flow rate 0.6 m³/h); and (iv) the heat extracted by the borehole heat exchanger increased with an increase in the thermal conductivity of the soil (experiments in the range of 0.4–6.0 W/m K). The numerical tool developed, the TRT data and simulation results obtained from the present work are of great value for design and optimization of borehole heat exchangers as well as studying other important factors such as the heat transfer performance during charging/discharging, freezing factor and thermal interference. Full article

In this paper, we study numerically the effect of rotation within a sample of water in a cylindrical container subject to rotation which is heated with a constant temperature at the bottom and lateral wall. We analyze the temporal behavior of temperature and flow velocity of the solvent. The thermal plumes developed at lower levels, already observed in the case without rotation, begin to spiral spreading outwards by the effect of rotation, increasing the azimuthal velocity of the fluid. No significant increases in the radial and vertical velocity components are observed which do not favor the mixture of hotter and colder flows in the sample and a faster heating of the solvent. In the rotation range studied, the state loses the axisymmetry and becomes fully 3D earlier in time as the rotation rate increases. To perform simulations, we use a 3D temporal model that couples momentum and heat equations and is based on spectral element methods. Full article

This article presents a novel method for the detection of biofilms based on a heatable, capacitive sensor structure (CSS). Biofilms are capable of strongly binding large amounts of water to their extracellular biopolymer matrix, which is detectable via its dielectric properties. A main challenge is to determine the difference between the inherent occurring presence of moisture in the ecosystem, which is necessary to form a biofilm and an actual formed biofilm. Therefore, the CSS is carefully heated to evaporate unbound surface moisture and determine whether there is a remaining residual alternation of the capacitance in comparison to the dry state. As a reproduceable substitute for complex, real biofilms, a hygroscopic, medical hydrogel-based on polysaccharides was used and applied by spray coating. Printed circuit boards (PCB) in different geometries and materials were used as CSS and compared in terms of their performance. A layer-thickness of 20 µm for the hydrogel coating to be sufficiently detected was defined as a realistic condition based on known values for real biofilms cited in literature. For this thickness a double-meander structure proves to be preferable over interdigitating and spiral geometries. It does offer a 30% lower, yet sufficient sensitivity, but shows advantages in manufacturing (one layer instead of two) and conductive heating capability. In the experiments, free water showed virtually no residual change, while the hydrogel-coated CSS still shows an approx. 300% higher value compared to a dry capacity. Yet, the overall small capacities of about 6–30 pF in dry state are difficult to measure and therefore sensitive to interferences and noise, which results in a high deviation. The principle of measurement can be evaluated as proofed by the carried out experiments, though offering room for improvement in the design of the study. The new method might be especially useful for pipes (e.g., hydrodynamically ineffective sensors installed in a pipe wall) if they at least are not permanently flooded with an aqueous medium, but can occasionally dry. If the internal surface is still only moist, it can be dried by initial heating. Full article

Three products hyrdrocyclone screen (TPHS) has been proposed for particle separation based on size. In TPHS, a cylindrical screen was embedded in a conventional hydrocyclone (CH) to combine the centrifugal classification and screening to particle separation based on size. The industrial application of TPHS indicates its better device performance than CH. Although, the earlier studies reveal some common understanding for TPHS, the information of the absent air column remains unknown. Hence, the combination of physical experiment and numerical simulation was considered involving a 75 mm TPHS for this knowledge gap. First, both the computational fluid dynamics (CFD) simulation with Reynolds stress mode and the physical experiment with a high-definition camera illustrate the development process details of a flow field in TPHS. That is, the water was imported along the tangential inlet into TPHS; then under the effects of the feed chamber wall and gravity, the liquid phase spiraled downward until the cylindrical screen passed through the sieve; as the liquid moved to the spigot, it could be discharged in time due to the small underflow port, thus the volume fraction of air rapidly reduced from 1 to 0; subsequently the water filled the TPHS and the absent air column could be observed. Furthermore, the distribution comparisons of air volume fraction and static pressure show that TPHS displayed the absent air core with the negative static pressure in the center region along the z-axis, while CH displayed the opposite features. In addition, despite the different inlet velocity, TPHS consistently presented the vanished air column which could be ascribed to the fact that the present cylindrical screen resulted in positive static pressure distribution inside TPHS. Full article

The improvement of water management in agriculture by exactly detecting moisture parameters of soil is crucial. To investigate this problem, a mini inside-out nuclear magnetic resonance sensor (NMR) was proposed to measure moisture parameters of model soils. This sensor combines three cylindrical magnets that are magnetized in the axial direction and three arc spiral coils of the same size in series. We calculated and optimized the magnet structure by equivalent magnetization to current density. By adjusting the radius and height between the cylinders, a circumferential symmetric constant gradient field (2.28 T/m) was obtained. The NMR sensor was set at 2.424 MHz to measure the water content of sandy soil with small particle diameter and silica sand with large particle diameter. The complete decaying, an NMR signal was analyzed through inverse Laplace transformation and averaged on a T₂ space. According to the results, moisture content of the sample is positively correlated with the integral area of T₂ spectrum peak (A_peak); T₂ of the water in small pores is shorter than that in large pores, because the movement of water molecules are limited by the inner wall of the pores. In the same volume, water in large pore sample is more than that in small pore sample, so A_peak of silica sand is larger than A_peak of sandy soil. Therefore, the sensor is capable of detecting moisture both content and pore size of the sample. This mini sensor (4.0 cm in diameter and 10 cm in length) is portable, and the lowest measurable humidity is 0.38%. Thus, this sensor will allow easy soil moisture measurements on-field in the future. Full article