Vertical Plain Research Articles

Heat and mass transfer characteristics of vertical falling film cylindrical plastic surfaces under partial wetting conditions for liquid desiccant regeneration

The regenerator plays a dominant role in the overall energy-economic performance of liquid desiccant systems. Nevertheless, very few studies have been reported on falling film liquid desiccant regenerators. Most of the previous studies targeted experimental/numerical modelling needs of regeneration process under design conditions. In the current research workexperimental investigation of regeneration process is carried out to study the coupled heat and mass transfer process for adiabatic regeneration of LiCl liquid desiccant over outer surface of vertical Plain and Modified polypropylene cylindrical surfaces under design (complete wetting) and part load (partial wetting) operating conditions. Modified cylindrical surfaces are developed to compensate the poor wetting of the plastic surfaces. New generalised one-dimensional numerical philosophy is proposed to accommodate the need of part load operating conditions by inclusion of actual wetting of the working surface as well as convective heat transfer happening from dry patches of solid surface to the flowing air. The heat and mass transfer coefficients are determined by solving the governing coupled heat and mass balance non-linear differential equation using the numerical finite difference method. It is found that the Modified surface offered an average improvement of 35.8% in the mass transfer coefficient under partial wetting conditions. New Sh and Nu number correlations are proposed by incorporating heat and mass transfer driving potentials and new parameter wetting factor. The developed correlations predicted the change in humidity and temperature across the regenerator with an average error of 6.2% and 7.5%, whereas from the existing two correlations found in the literature, the first one predicted the same experimental observations with an average error of 54.6% and 36.2%, while second one predicted with an average error of 77.3% and 22.0%, respectively. The results highlighted that the assumption of complete wetting of working surface under part load operating conditions leads to significant error in prediction of air outlet conditions. The proposed correlations will be helpful for numerical modelling and simulation of falling film regenerators under wide range of liquid loading conditions.

Mathematical Analysis of Dynamic Models of Suspension Bridges with Delayed Damping

Suspension bridges are a type of construction in which the deck is suspended under a series of suspension cables that are on vertical hangers. The first modern example of this project began to appear in the early 1800s. Modern suspension bridges are lightweight, aesthetically pleasing and can span longer distances than any other bridge form. Many papers have been devoted to the modelling of suspension bridges, for instance, Lazer and McKenna studied the problem of nonlinear oscillation in a suspension bridge. They introduced a (one-dimensional) mathematical model for the bridge that takes into account of the fact that the coupling provided by the stays connecting the main cable to the deck of the road bed is fundamentally nonlinear, that is, they gave rise to the system of semi linear hyperbolic equation, where the first equation describes the vibration of the road bed in the vertical plain and the second equation describes that of the main cable from which the road bed is suspended by the tie cables. Recently, interest in this field has been increasing at a high rate. In this paper, we investigate some mathematical models of suspension bridges with a strong delay in linear aerodynamic resistance force. We establish the exponential decay of the solution for the corresponding homogeneous system and prove the existence of an absorbing set as well as a bounded attractor.

Sensitivity of the Non-Equilibrium Approach for Mixture Condensation to Heat and Mass Transfer Correlations and Thermophysical Properties

Abstract The prediction of mixture condensation is still complex due to the coupled heat and mass transfer and insufficient data of thermophysical mixture properties. This article analyzes the impact of various heat and mass transfer correlations on the non-equilibrium approach for mixture condensation in a vertical plain tube. Furthermore, the influence of thermophysical properties from different databases is investigated. The results are shown for ethanol-water, but allow conclusions to other fluid mixtures. They indicate that the liquid heat transfer coefficient in the non-equilibrium approach dominates the qualitative behavior of the condensation process, but the vapor mass transfer coefficient can only decrease or increase the quantitative level of the effective heat transfer with minor impact. More importantly, the logarithm in the vapor mass transfer term is central for the prediction of the condensation heat transfer. As this logarithm contains vapor-liquid equilibrium (VLE) data, it proves that there is a strong connection between VLE and overall prediction of mixture condensation. A demonstration of available data for thermophysical mixture properties of ethanol-water shows significant deviations, which affect the calculations as well. Besides, data from our own experiments are presented for mixture viscosity of ethanol-water. It is recommended to focus not only on improved heat and mass transfer correlations but also on thermophysical properties and VLE data for a precise prediction of mixture condensation.

Wettability-defined frosting dynamics between plane fins in quiescent air

Finned heat exchangers used in energy applications regularly undergo condensation frosting. Understanding the effects of fin spacing on frost growth with surfaces having differing wettability is important for the design of next-generation heat exchangers. This study presents an experimental investigation using high-resolution optical imaging of frost growth between two parallel vertical plain aluminum fins as a function of surface wettability (hydrophilic, superhydrophilic, superhydrophobic), fin surface temperature (-5 to -15 °C), fin spacing (2 to 8 mm), and relative humidity (≈ 50 and 70%). We observe two distinct regimes of frost growth for all test conditions. The effect of surface wettability on frost growth rate becomes significant for fin spacing ≤ 6 mm at fin surface temperatures below -10 °C. The fin surface temperature plays a significant role for fin spacing > 4 mm. Furthermore, for hydrophilic surfaces, the effect of relative humidity was found to be significant for fin spacing > 4 mm. To explain the frosting physics and mass transfer effects, we developed a three-dimensional finite volume method simulation to characterize the moist air flow field between fins at varying fin spacings. For similar humidity, fin surface temperature, and wettability, larger fin spacing resulted in higher frost growth rate due to higher access to moist air. We use the experimental data to develop an empirical correlation for predicting frost thickness. Furthermore, we develop an artificial neural network independent of predetermined functional form that can be trained with the experimental data to predict frost thickness with high accuracy.

Quasi-stationary modelling of solidification in a latent heat storage comprising a plain tube heat exchanger

In this paper, a two-dimensional model of a latent heat storage is presented. The model describes the time-dependent solidification of a phase-change material (PCM) around a plain tube heat exchanger. Heat transfer and energy balance equations are combined to predict the heat flow rate from the solidifying PCM to the heat transfer fluid. The model utilizes the temperature-based approach combined with a quasi-stationary approximation. In contrast to most solidification modelling approaches, the model is characterized by low computational complexity which enables the simulation of the entire storage volume instead of only a small section. The model is compared with experimental data obtained from a latent heat storage test-rig with a vertical plain tube heat exchanger. The predicted power output matched the experimental results very well, demonstrating the high accuracy of the simulations. This is the first report of a quasi-stationary model of a latent heat storage being validated with a PCM other than water and thus demonstrates the applicability of this approach in a wider range of PCM. The presented model can be used as a fast and accurate tool to design latent heat storage units as well as to analyse the performance of existing storage tanks.

Dynamic simulation and experimental validation of a two-phase closed thermosyphon for geothermal application

The heat transfer performance of a vertical two-phase closed thermosyphon (TPCT) used in a geothermal heat pump was experimentally investigated. The TPCT is a vertical plain steel pipe with inner diameter of 114 mm and bored 368m deep underground. Carbon dioxide (CO2) is used as working fluid. In the TPCT there is no condensation section. CO2 is condensed by the evaporator of the heat pump, flows into the head of the TPCT and runs down as a falling film along the inner wall of the pipe. For the heat transfer simulation in the TPCT, a quasi-dynamic model in which the mass transfer between the liquid and vapor phases as well as the conduction heat transfer from the surrounding soil towards the pipe is treated dynamically. However the film flow modeling is based on the Nusselt theory of film condensation. The comparison of the experimental data with the numerical simulation is presented and discussed.

Finite Element Method Study on Stress State in Soil Induced by Agricultural Traffic

In general, when a tyre is running on a deformable soil, the soil compaction will occur not only on surface layers, but also on soil profile, in deeper layers. This leads to a series of negative effects not only on physical and mechanical properties of soil, but also influences the crops growth and the crop yield. For these reasons, currently are needed solutions to reduce soil compaction, caused mainly by agricultural implements passing on the soil surface in order to aply the specific crop production technologies. From our simulation we can draw the following conclusions: the soil stresses decreased with depth; the soil displacements magnitude increased with soil water content due to lower friction forces between soil particles (water acts like a lubricant between soil particles); decreasing rate for soil displacement is influenced by load magnitude and tyre inflation pressure; the soil particles moved in vertical plain from the top to the bottom, but also in horizontal direction, from the center to the edge in cross section and in longitudinal direction; the dimensions of the geometric shape of the mentioned soil volume is influenced by load and tyre inflation pressure. In this paper the agricultural traffic and its influence on stress state in soil, it was used a software application based on Finite Element Method, that has been proved to be a useful tool for soil compaction assessment in order to find the right decisions for a proper field traffic management.

Scour Formation Due to Laterally Inclined Circular Pier

The purpose of this paper was to study the local scour formation due to an inclined circular bridge pier. The experiments for two cases of inclined and vertical piers under clear-water condition with four different flow conditions have been performed. The experiments were conducted in the hydraulic laboratory of Tarbiat Modares University in a rectangular channel. Also, for better interpretation of the observed changes, the longitudinal component values of the velocity in a vertical plain with definite distance located downstream of the vertical and inclined piers were recorded using a velocimeter. The results show that although the scour hole shape and its ridge is changed with the inclination angle of pier, the maximum scour depth in a laterally inclined pier is almost equal to that of a vertical pier and the location of the maximum scour depth in vertical pier has transferred from the 0° area to the approximately 30° area in inclined pier state.

Preoperative cephalometric analysis to predict transoral robotic surgery exposure.

Transoral robotic surgery (TORS) is being increasingly used in the treatment of head and neck cancer and we wanted to determine the feasibility of predicting TORS access using cephalometric measurements obtained from preoperative imaging. 20 cephalometric measurements were obtained from imaging on 31 TORS base of tongue (BOT) resections and compared to adequacy of exposure. Three measurements were found to be significantly different between the restricted and adequate exposure groups. Distances from posterior pharyngeal wall (PPW) to hyoid, PPW to soft palate and epiglottis to vertical laryngeal angle were all statistically different between the two groups. Receiver operating characteristic (ROC) analysis revealed strong correlation to exposure for all three measurements with cut offs ≤30 mm between the PPW and the hyoid, ≤8.1 mm PPW and soft palate and ≥130° between the epiglottis and vertical plain of the larynx all representing restricted exposure. Duration of surgery for the restricted group, 85 min, was significantly longer than the adequate exposure group, 51 min (p = 0.026). Preoperative measurements of radiographic images of the oropharyngeal working space can predict restricted exposure for TORS resection of the BOT. These measures may be used in conjunction with other subjective assessment parameters to predict which patients could benefit from a staging endoscopy to determine adequate TORS exposure.

Lazika Pier Sculpture

AbstractLazika is a new city in Georgia located on the Black Sea coast. The one‐hundred meter long Lazika Pier with its 31 m high landmark sculpture is one of the first structures to mark the beginning of the development of this new metropolis.The sculpture designed by German architect Jürgen Mayer H. consists of stacked oval elements – so called blobs – organized in seven levels. The blobs are subdivided into vertical plain levels running in an orthogonal direction with a distance of 90 cm. Due to the exposed position, tough requirements concerning corrosion resistance and a pretty tight timetable for design, fabrication and erection, structural steel has been chosen as the building material. The sculpture consists of steel plates with varying thicknesses of 5 to 10 mm. Elements composed of plasma‐cut plates were pre‐fabricated within a site workshop and installed using mobile cranes. Exterior and interior lighting features provide a dynamic and pulsating look to the sculpture.

Inspection and calibration of theodolites by Metrological laboratory of the Military Geographical Institute of the Serbian Armed Forces

This paper describes procedures for inspection and calibration of theodolites, the surveying instruments designed for angle measurements in horizontal as well as in vertical plains, which is in use by the Military Geographical Institute (as a matter of fact, its Metrological laboratory ML 06). The paper has an example of the records of the measurements. Those procedures are based on the German standard DIN 18723-3 published in 1990, as well as on ISO 17123-3:2001, and elaborated in details by metrological instruction MUP 143500V-01.

Globalizacija i promene društva

The main problem analized in this essay is globalization as the basic way of social change and changing society in the XXI century. Globalization has a huge influence in horizontal and vertical plain, on social, economic, political and cultural level, and in the same time on international, regional, national, and organizational level, level of social gropus and individuals. That is the reason why globalization is one of the main topics of contemporary sociology and sociological research.

Forced convective flow and heat transfer of upward cocurrent air–water slug flow in vertical plain and swirl tubes

This experimental study comparatively examined the two-phase flow structures, pressured drops and heat transfer performances for the cocurrent air–water slug flows in the vertical tubes with and without the spiky twisted tape insert. The two-phase flow structures in the plain and swirl tubes were imaged using the computerized high frame-rate videography with the Taylor bubble velocity measured. Superficial liquid Reynolds number ( Re L) and air-to-water mass flow ratio (AW), which were respectively in the ranges of 4000–10000 and 0.003–0.02 were selected as the controlling parameters to specify the flow condition and derive the heat transfer correlations. Tube-wise averaged void fraction and Taylor bubble velocity were well correlated by the modified drift flux models for both plain and swirl tubes at the slug flow condition. A set of selected data obtained from the plain and swirl tubes was comparatively examined to highlight the impacts of the spiky twisted tape on the air–water interfacial structure and the pressure drop and heat transfer performances. Empirical heat transfer correlations that permitted the evaluation of individual and interdependent Re L and AW impacts on heat transfer in the developed flow regions of the plain and swirl tubes at the slug flow condition were derived.

Three-dimensional mesh resolution control in finite difference groundwater flow models through boxed spatial zooming

Summary The iterative composite mesh simulation (CMS) technique operates a coupled system of point centered finite difference groundwater flow models. It allows for high lateral and vertical mesh resolution at the sites of interest, whereas a coarser mesh may be applied in other parts of the formation. The boxed spatial zooming method utilizes a “box-in-box” architecture to build the coupled 3D system of embedded (nested) parent and child meshes exhibiting different vertical and lateral extensions and resolutions. A mesh interface simulator is used to equate the heads and balance the fluxes along the common vertical plains and shared lateral layers (interfaces) linking the meshes. This multi mesh simulation method is used by software FLOW and has been successfully tested in multi-aquifer systems against selected unsteady and steady state well flow problems with available analytical solutions. The base compatibility with MODFLOW databases supports wider use of the FLOW simulator.

Existence of global attractors for the coupled system of suspension bridge equations

A mathematical model of the suspension bridge describes the vibration of the road bed in the vertical plain and that of the main cable. We show the existence of an absorbing set for the solution of the problem. Furthermore, the global attractors of the coupled system of suspension bridge are studied by a new semigroup approach.

Bending Behavior of Woven Fabrics with Vertical Seams

This paper presents a study of the bending properties of fabric strips with vertical plain seam. The "second moment of area" of a seamed cross section determines the bending behavior of such a strip. Fabric thickness, seam thickness, distance of the neutral axis from the surface of the cross section, and seam allowance width are involved. Various woven fabrics with different seam allowances are investigated. Bending length and bending rigidity obtained from the experimental results are highly related to the second moment of area of the seamed fabric cross section.

R-113 condensation on vertically finned plate

In this study, condensation tests were conducted on a vertically finned plate (fin height 1 mm, fin thickness 1 mm, fin spacing 1 mm) using R-113. Results showed that fins enhanced the condensation on a vertical plain surface as much as four times. Comparison with theoretical models revealed that the effect off surface tension should be included in the model. The effect of interruption plates was also investigated. The plates were not effective in enhancing the finned plate condensation. The reason may be attributed to the already thinned condensate film on the finned surface.

132 自然対流場の3次元画像温度計測

This paper presents a new measurement system for three-dimensional temperature distribution in a rotating Rayleigh-Benard convection based on color image processing. This system is an extension of two-dimensional temperature measurement system in which thermo-sensitive liquid-crystal suspension method is adopted for flow visualization and neural network is used for correlating between color and temperature. Interpolating two-dimensional temperature distributions in vertical plain by B-spline function, three-dimensional temperature distribution in the fluid layer was obtained.

相模平野における冬の海陸風について

The explanation of winter land and sea breezes, which blow sometimes in the Sagami Plain is attempted. In the upper layer, the temperature is not affected by the surface temperature, and the pressure gradient is from the land to the sea. While, at night, the air is in contact with the cooled land surface and becomes denser than the air on the sea. lIn the lower layer, the pressure gradient develops from the sea to the land. This is seemed to be the cause of the winter land and sea breezes.The quantitative explanation of this idea is undertaken based on a two-dimensional numerical model which simulates a circulation in a vertical plain perpendicular to the coast-line. It is shown that the diurnal variation of eddy temperature conductivity and eddy viscosity have a possibility to produce winter land and sea breezes.