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Wyniki wyszukiwania dla: SUPERCRITICAL FLUIDS
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Alternative Approach to Convolution Term of Viscoelasticity in Equations of Unsteady Pipe Flow
PublikacjaIn the paper the selected aspects concerning description of viscoelastic behavior of pipe walls during unsteady flow are analyzed. The alternative convolution expression of the viscoelastic term is presented and compared with the corresponding term referring to unsteady friction. Both approaches indicate similarities in the forms of impulse response functions and the parameter properties. The flow memory was introduced into convolution...
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Alternative convolution approach to friction in unsteady pipe flow
PublikacjaIn the paper some aspects of the unsteady friction in pipe flow expressed by the convolution are analyzed. This additional term introduced into the motion equation involves the accelerations of fluid occurring in the past and a weighting function. The essence of such approach is to assume the appropriate form of weighting function. However, until now no fully reliable formula for this function has been found. To avoid some inconveniences...
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An Experimental and Numerical Analysis of Water Hammer Phenomenon in Slurries
PublikacjaThe analysis of slurry transportation in pressure pipelines is important both from practical and theoretical point of view. Due to the nature of the medium, the number of problems arising in the course of design, operation, measurements and mathematical modeling is much higher compared to the cases where the flowing liquid is homogeneous. The equations describing the flow are more complex, and higher number of the parameters is...
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In Situ Verification of Numerical Model of Water Hammer in Slurries
PublikacjaThis paper presents a numerical model of transient flow in a pressure slurry pipeline network with verification based on in situ measurements. The model, primarily verified in laboratory conditions, has been extended and applied to the case of a large and complex slurry pipeline network in Poland. In the model, the equivalent density concept was applied. In situ experiments were performed for various unsteady flow episodes, caused by...
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Activation Energy and Inclination Magnetic Dipole Influences on Carreau Nanofluid Flowing via Cylindrical Channel with an Infinite Shearing Rate
PublikacjaThe infinite shear viscosity model of Carreau fluid characterizes the attitude of fluid flow at a very high/very low shear rate. This model has the capacity for interpretation of fluid at both extreme levels, and an inclined magnetic dipole in fluid mechanics has its valuable applications such as magnetic drug engineering, cold treatments to destroy tumors, drug targeting, bio preservation, cryosurgery, astrophysics, reaction kinetics,...
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On nonlinear dilatational strain gradient elasticity
PublikacjaWe call nonlinear dilatational strain gradient elasticity the theory in which the specific class of dilatational second gradient continua is considered: those whose deformation energy depends, in an objective way, on the gradient of placement and on the gradient of the determinant of the gradient of placement. It is an interesting particular case of complete Toupin–Mindlin nonlinear strain gradient elasticity: indeed, in it, the...
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Rapid assessment of the authenticity of limequat fruit using the electronic nose and gas chromatography coupled with mass spectrometry
PublikacjaCitrus fruits are very popular food products. There are many species and varieties of them. There are also documented cases of some citrus fruits causing a severe allergic reaction. Some species of the citrus fruits, especially hybrid ones show a reduced allergenic effect due to the lack of seeds. There is a need for rapid methods for evaluation of citrus’ botanical origin. During research, the headspace of three citrus fruits...
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Theoretical Organic Rankine Cycle efficiency depending on different thermodynamic work variables.
PublikacjaOne of promising technologies of utilizing low- temperature waste heat is through ORC (Organic Rankine Cycle) system implementation. A primary objective in designing in-stallations based on such systems is to maximize the installation's work efficiency. On the other hand, ecological factors are commonly considered a natural barrier in introducing new, often very expensive technologies. Ecological effect of a potential modernization...
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WSPÓŁPRACA BLOKU GAZOWO-PAROWEGO Z OBIEGIEM ORC = Combinded power plant in cooperation with ORC
PublikacjaIn the paper presented is the idea of a combined gas and steam power plant cooperation with a low temperature organic Rankine cycle ORC unit. Considerations presented in the paper are accomplished for the Gorzów CHP. The intention of present analysis is heat recovery of low temperature energy and its further use in ORC cycle in order to produce electricity, without increase in fuel consumption. Waste energy is recovered from the...
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Gas boiler as a heat source for the domestic micro-CHP
PublikacjaIn the presented analysis a commercially available domestic gas boiler as a heat source for domestic ORC is considered. The applicability of the gas boiler (De Dietrich with thermal power 25 kW) coupled with the laboratory prototype micro ORC setup has experimentally studied. The main aim of the study is to determine the working fluid temperature, attainable heat rates and efficiencies of the whole system. Preliminary investigations...
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Subcritical bifurcation of free elastic shell of biological cluster
PublikacjaIn this paper we will investigate symmetry-breaking bifurcation of equilibrium forms of biological cluster. A biological cluster is a two-dimensional analogue of a gas balloon. The cluster boundary is connected with its kernel by elastic links. The inside part is filled with compressed gas or fluid. Equilibrium forms of biological cluster can be found as solutions of a certain second order ordinary functional-differential equation...
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Gas boiler as a heat source for the domestic micro-CHP
PublikacjaThis analysis considers a commercially available domestic gas boiler as a heat source for a domestic organic Rankine cycle system. An experimental study was made into the applicability of the gas boiler (De Dietrich with thermal power 25 kW) coupled with the laboratory prototype micro ORC setup. The main aim of the study is to determine the working fluid temperature, attainable heat rates and effciencies of the whole system. Preliminary...
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Influence of local bush wear on water lubricated sliding bearing load carrying capacity
PublikacjaOne of main problems concerning water-lubricated bearings is their durability. There are known cases of bearings with life time measured in decades, and some, whose refurbishment was necessary just days after start-up. Obtaining stable fluid film friction plays key role in the durability of these bearings. Unfortunately, their load-carrying capacity is limited due to water's low-viscosity. The conducted experimental...
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Thermal Biomass Conversion: A Review
PublikacjaIn this paper, the most important methods of thermal conversion of biomass, such as: hydrothermal carbonization (180–250 °C), torrefaction (200–300 °C), slow pyrolysis (carbonization) (300–450 °C), fast pyrolysis (500–800 °C), gasification (800–1000 °C), supercritical steam gasification, high temperature steam gasification (>1000 °C) and combustion, were gathered, compared and ranked according to increasing temperature. A comprehensive...
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On the internal efficiency of a turbine stage: classical and CFD definitions
PublikacjaAlmost entire fleet of steam turbines in Poland was designed between 1950 – 1980 with the use of the so-called zero dimensional (0D) calculation tools. For several years, design and modernization of the turbines occur in assistance with the state of the art methods that describe working fluid flow field based on 3D models and CFD codes. This cooperation between 0D and 3D codes requires exchange of overall, integral information...
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Wind resource assessment and energy yield prediction for the small wind turbine on the Szubieniczne Hill
PublikacjaThe goal of this study is to preliminary assess the wind resources on the Szubieniczne Hill in order to predict the annual energy production for planned small wind turbine. The analyzed site is located close to the Gdańsk University of Technology campus, in complex urban environment additionally surrendered by forested hills. The assessment is based on Computational Fluid Dynamics simulations which allow to evaluate the wind energy potential...
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generation of the vorticity mode by sound in a bingham plastic
PublikacjaThis study investigates interaction between acoustic and non-acoustic modes, such as vorticity mode,in some class of a non-newtonian fluid called Bingham plastic. The instantaneous equations describinginteraction between different modes are derived. The attention is paid to the nonlinear effects in the fieldof intense sound. The resulting equations which describe dynamics of both sound and the vorticity modeapply to both periodic...
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On the material symmetry group for micromorphic media with applications to granular materials
PublikacjaWithin the framework of the theory of nonlinear elastic micromorphic continua we introduce the new definition of the local material symmetry group. The group consists of ordered triples of second- and third-order tensors describing such changes of a reference placement that cannot be recognized with any experiment. Using the definition we characterize the micromorphic isotropic media, micromorphic fluids, solids and special intermediate...
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Residence time distribution in rapid multiphase reactors
PublikacjaResidence time distribution (RTD) provides information about average hydraulic residence time and the distribution of material in the reactor. A method for determining RTD for reactors with very short hydraulic residence times is deconvolution based on extraction of real RTD by the analysis of a non-ideal input signal. The mean residence time and dispersion were determined for the spinning fluids reactor (SFR). For the first time...
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Analysis of the radiation dose in UV-disinfection flow reactors.
PublikacjaTheoretical considerations devoted to the variation of UV radiation doses in flow disinfection reactors are presented. The minimal time required by the fluid to pass the reactor was determined and combined with the radiation intensity. The active zones of the reactor were determined.
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Albumin–Hyaluronan Interactions: Influence of Ionic Composition Probed by Molecular Dynamics
PublikacjaThe lubrication mechanism in synovial fluid and joints is not yet fully understood. Nevertheless, intermolecular interactions between various neutral and ionic species including large macromolecular systems and simple inorganic ions are the key to understanding the excellent lubrication performance. An important tool for characterizing the intermolecular forces and their structural consequences is molecular dynamics. Albumin...
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Management of low-temperature heat source by ORC aided by additional heat source
PublikacjaThe presented work is aimed at utilisation of waste heat in the manner to produce electricity in ORC installation. Therefore the precondition of the study was to use the waste heat available in the form of a stream of hot water at 90°C. Such low enthalpy heat source is rather insufficient to produce a good quality vapour to feed the ORC turbine. That was the incentive to search for the ways of increasing the temperature of the...
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Neural network simulator's application to reference performance determination of turbine blading in the heat-flow diagnostics.
PublikacjaIn the paper, the possibility of application of artificial neural networks to perform the fluid flow calculations through both damaged and undamaged turbine blading was investigated. Preliminary results are presented and show the potentiality of further development of the method for the purpose of heat-flow diagnostics.
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A commercial gas boiler fitted with the ORC module as perspective solution for households
PublikacjaIn this paper the applicability of the commercial gas boiler (De Dietrich DTG X23N) coupled with the laboratory prototype micro ORC setup was experimentally studied. The main objective was to determine the working fluid capability to obtain required temperatures of vapour prior to the turbine, attainable heat rates and efficiencies of the whole system. The boiler thermal power was 25 kW. Tests were carried out with a single stage...
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Flow structure, heat transfer and scaling analysis in the case of thermo-magnetic convection in a differentially heated cylindrical enclosure
PublikacjaThe experimental, numerical and scaling analysis in the case of thermo-magnetic convection in a thermosyphon-like enclosure filled with a paramagnetic fluid is presented. Visualization of temperature field together with the numerical simulation gave an information about the flow structure, which indicated “finger-like” structures of hot and cold streams advecting each other. Their number depended on the Rayleigh number and also...
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Experimental investigation of two-phase thermosyphon heat exchanger charged with acetone
PublikacjaThis paper presents thermal characteristics of prototype of a two-phase thermosyphon heat exchanger (TPTHEx) charged with acetone as a working fluid. The TPTHEx consists of two horizontal cylindrical vessels connected by two risers and a downcomer. Tube bundles placed in the lower and upper cylinders work as an evaporator and a condenser, respectively. The tested TPTHEx operates in a vacuum. Therefore, the working liquid is boiled...
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Assessing and Mitigating Ice-Jam Flood Hazards and Risks: A European Perspective
PublikacjaThe assessment and mapping of riverine flood hazards and risks is recognized by many countries as an important tool for characterizing floods and developing flood management plans. Often, however, these management plans give attention primarily to open-water floods, with ice-jam floods being mostly an afterthought once these plans have been drafted. In some Nordic regions, ice-jam floods can be more severe than open-water floods,...
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Assessment of toxic and endocrine potential of substances migrating from selected toys and baby products
PublikacjaAnalysis of literature data shows that there is limited information about the harmful biological effects of mixture of compounds from the EDC group that are released from the surface of toys and objects intended for children and infants. One of the tools that can be used to obtain such information is appropriate bioanalytical tests. The aim of this research involved determining whether tests that use living organisms as an active...
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The compositional space of exhaled breath condensate and its link to the human breath volatilome
PublikacjaBreath analysis is commonly understood to target gaseous or volatile organic compounds (VOCs) for the characterization of different pathologies. Targeted analysis is most effective if a working hypothesis can be based on a plethora of data. The recently published volatilome builds an optimal basis for organizing powerful target sets. However, the origin and pathways of biosynthesis of many VOCs are not known, which complicates...
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Flow Maps and Flow Patterns of R1233zd(E) in a Circular Minichannel at Low, Medium and High Values of Saturation Pressure
PublikacjaThere is a gap in knowledge regarding the flow pattern of low-boiling working fluids in the range of high saturation temperatures (above 120°C) and medium and high reduced pressures (0.5-0.9). Data are present in the literature for similar values of reduced pressures, but for lower values of saturation temperature. This is due to the existing refrigeration applications of these working fluids. At high values of reduced pressure,...
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Fast GC as a useful tool for authenticity assessment of kiwifruit
PublikacjaKiwifruit is one of the healthiest fruits due to its high content of biologically active substances and nutrients. The most popular species of Actinidia (kiwifruit) are the Actinidia deliciosa fruits called kiwi and Actinidia chinensis commonly called golden kiwi, while the lesser known species is Actinidia arguta known as mini kiwi. Bioactivities and nutrients of Actinidia are influenced by species and cultivars. It is very important...
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Teoretyczno-doświadczalne modelowanie konwekcji wymuszonej nanocieczy
PublikacjaPrzedłożona rozprawa doktorska dotyczy badań eksperymentalnych oraz numerycznych konwekcji wymuszonej nanocieczy. Badane nanociecze wytworzone były z cieczy bazowych takich jak woda demineralizowana i mieszaniny wody z glikolem etylenowym w trzech proporcjach objętościowych 90:10, 80:20 i 60:40. Jako nanocząstki użyto Al2O3, a wytworzone nanociecze miały koncentracje masowe 0,1%, 1% i 5%. Wyznaczono eksperymentalnie dynamiczny...
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Electromagnetic Control and Dynamics of Generalized Burgers’ Nanoliquid Flow Containing Motile Microorganisms with Cattaneo–Christov Relations: Galerkin Finite Element Mechanism
PublikacjaIn our research work, we have developed a model describing the characteristics of the bio-convection and moving microorganisms in the flows of a magnetized generalized Burgers’ nanoliquid with Fourier’s and Fick’s laws in a stretchable sheet. Considerations have been made to Cattaneo–Christov mass and heat diffusion theory. According to the Cattaneo–Christov relation, the Buongiorno phenomenon for the motion of a nanoliquid in...
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Cyanides in the environment—analysis—problems and challenges
PublikacjaCyanide toxicity and their environmental impact are well known. Nevertheless, they are still used in the mining, galvanic and chemical industries. As a result of industrial activities, cyanides are released in various forms to all elements of the environment. In a natural environment, cyanide exists as cyanogenic glycosides in plants seeds. Too much consumption can cause unpleasant side effects. However, environmental tobacco smoke...
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Numerical Simulation of two dimensional flow past a bridge cross section
PublikacjaThis work presents some numerical results concerning application of CFD in civil engineering problems. Selected theoretical aspects of fluid mechanics are elucidated. In the second part of the paper a cross section of upper footbridge of the Bella Sky Hotel in Copenhagen is analysed numerically in the field of wind action.
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Investigation of some magnetospheric phenomena of geomagnetic storm on March 17, 2013 based on observations from GNSS and NOAA-15 satellite
PublikacjaSubstantial variations of magnetospheric electron fluxes of low and intermediate energies at an altitude of ~ 800 km at different phases of the geomagnetic storm were investigated. The ionosphere and plasmasphere response was analyzed using TEC variation maps over the Central Europe. A concept of the connection of TEC variations above the Central Europe and spatially inhomogeneous fluxes of energetic particles is being proposed.
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Acoustic heating produced in the boundary layer
Publikacja: Instantaneous acoustic heating of a viscous fluid flow in a boundary layer is the subject of investigation. The governing equation of acoustic heating is derived by means of a special linear combination of conservation equations in the differential form, which reduces all acoustic terms in the linear part of the final equation but preserves terms belonging to the thermal mode. The procedure of decomposition is valid in a weakly...
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Rotor Blade Geometry Optimisation in Kaplan Turbine
PublikacjaThe paper presents the description of method and results of rotor blade shape optimisation. The rotor blading constitutes a part ofturbine flow path. Optimisation consists in selection of the shape that minimises ratio of polytrophic loss. Shape of the blade isdefined by the mean camber line and thickness of the airfoil. Thickness is distributed around the camber line based on the ratio ofdistribution. Global optimisation was done...
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On the differential effect of temperature on the Nusselt-Rayleigh relationship in free convection
PublikacjaThe aim of and inspiration behind this paper was to explain the reasons, also observed by other researchers, of the discrepancy in the results of experimental free convection, which for small Rayleigh and Nusselt numbers in the initial phase of research can sometimes reach several hundred percent. These discrepancies decrease with increasing heating power and plate surface temperature, in proportion to the increase in Ra and Nu,...
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The calculation long-term physical field created by water flow around the ship
PublikacjaThe paper presents a description of the problems with fluid flow around a ship. Using the described solution of the problem were performed numerical calculations using the boundary element method. Were also presented preliminary results of the calculation of pressure fields at the bottom of the ship, taking into account the impact of the bottom.
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Pomiar wartości opóźnienia hamowania dla sprawnego i niesprawnego układu hamulcowego
PublikacjaW artykule przedstawiono wyniki badań: sprawny układ hamulcowy i niesprawny układ hamulcowy. Pomiary opóźnienia hamowania przeprowadzono na suchej nawierzchni asfaltowej. Wykonano układ, który rozszczelnia przewód hamulcowy przy przednim prawym kole w czasie jazdy. Wykonano symulację wycieku płynu hamulcowego
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Ampacity of power cables exposed to solar radiation – recommendations of standards vs. CFD simulations
PublikacjaThe aim of the paper is to evaluate the ampacity of a low-voltage single power cable according to: 1) recommendations of the standard IEC 60287, 2) a Computational Fluid Dynamics method, implemented in Ansys software; and comparison of the results obtained for these two cases. Moreover, limitations of recommendations of the above mentioned standard are indicated.
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Hysteresis curves and loops for harmonic and impulse perturbations in some non-equilibrium gases
PublikacjaEvolution of sound in a relaxing gas whose properties vary in the course of wave propagation, is studied. A relaxing medium may reveal normal acoustic properties or be acoustically active. In the first case, losses in acoustic energy lead to an increase in internal energy of a gas similarly as it happens in Newtonian fluids. In the second case, acoustic energy increases in the course of sound propagation, and the internal energy...
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Experimental Determination of Limit Adhesive Shear Strtess between Solid Wall and Liquid
PublikacjaTheoretically slip of a fluid with respect to the solid wall should occur even at a very low velocity of motion. However theoretical analysisand some empirical data suggest that there must be a limit value of shear stress, below which the slip does not appear. A simple metyhod of this stress determination was proposed in the paper.
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Acute hypoxia diminishes the relationship between blood pressure and subarachnoid space width oscillations at the human cardiac frequency
PublikacjaAcute hypoxia exerts strong effects on the cardiovascular system. Heart-generated pulsatile cerebrospinal fluid motion is recognised as a key factor ensuring brain homeostasis. We aimed to assess changes in heart-generated coupling between blood pressure and subarachnoid space width oscillations during hypoxic exposure.
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Modeling and simulation of blood flow under the influence of radioactive materials having slip with MHD and nonlinear mixed convection
PublikacjaRadioactive materials are widely in industry, nuclear plants and medical treatments. Scientists and workers in these fields are mostly exposed to such materials, and adverse effects on blood and temperature profiles are observed. In this regard, objective of the current study is to model and simulate blood based nanofluid with three very important radioactive materials, named as Uranium dioxide (UO2), Thorium dioxide (ThO2) and...
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Steady magnetohydrodynamic flow in a diverging channel with suction or blowing
PublikacjaAn analysis is made of steady two-dimensional divergent flow of an electrically conducting incompressible viscous fluid in a channel formed by two non-parallel walls, the flow being caused by a source of fluid volume at the intersection of the walls. The fluid is permeated by a magnetic field produced by an electric current along the line of intersection of the channel walls. The walls are porous and subjected to either suction...
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Circumferential temperature distribution during nucleate pool boiling outside smooth and modified horizontal tubes
PublikacjaPrzedstawiono wyniki badań eksperymentalnych obwodowego rozkłądu temperatury w poziomych rurkach, ogrzewanych elektrycznie na których zachodzi wrzenie pęcherzykowe. Wykazano, że lokalne - w obszarze górnej tworzącej rurki, zastosowanie powłki porowatej prowadzi do wygładzenia rozkładu temperatury oraz obniżenia średniej temperatury ścianki.
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Experimental verification of natural convective heat transfer phenomenon from isothermal cuboids
PublikacjaArtykuł przedstawia wyniki badań eksperymentalnych konwekcyjnej wymiany ciepła od powierzchni izotermicznego prostopadłościanu o stosunkowo dużych rozmiarach (t.j. 1.5 m x1 m x 0.5 m). Celem tych badań było otrzymanie wyników, które można by porównać z otrzymanymi dla obiektu w mniejszej skali i prezentowano we wcześniejszych doniesieniach (Int. J. Heat Mass Transfer 46 (2003) 2169-2178). Rozwiązanie eksperymentalne przeprowadzono...
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Liquid crystal technique application for heat transfer investigation inafin-tube heat exchanger element
PublikacjaPublikacja przedstawia rezultaty prac autorów w zakresie wykorzystania techniki ciekłokrystalicznej w badaniach wymiany ciepła dla elementów wymiennika ciepła. Technika ta z powodzeniem została zastosowana do analizy sposobu zabudowy wymiennika na jego efektywność.