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Search results for: Heat transfer
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Non-isothermal effects in a common method for calculation of heat transfer coefficient in flow boiling and flow condensation in minichannels
PublicationW pracy przestawiono efekty nieizotermiczne w metodzie wyznaczania współczynnika przejmowania ciepła podczas wrzenia w przepływie oraz kondensacji w przepływie w minikanałach. Wyniki obliczeń porównano z badaniami eksperymentalnymi z literatury, uzyskując dobrą zgodność.
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Experimental validation of the theoretical analysis of heat transfer between a liquid layer formed by an impinging jet and a solid surface
PublicationPrzedstawiono wyniki badań eksperymentalnych wymiany ciepła między poziomą powierzchnią a przepływająca po niej warstwa cieczy utworzoną z napływającej strugi gazowo-cieczowej. Wyniki badań eksperymentalnych porównano z modelem teoretycznym zjawiska.
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Evaluating the influence of radiative heat flux on convective heat transfer from a vertical plate in air using an improved heating plate
PublicationThis article examines the influence of radiative heat flux on the accuracy of the results of free convective heat transfer in air. In order to carry out these tests, based on the experience gained during the operation of a plate heated on one side, compensated by a reverse heat loss flux counter-heater, a unique double-sided heating sandwich plate was designed and built, consisting of three thin epoxy resin plates reinforced with...
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An experimental investigation on the effect of new continuous core-baffle geometry on the mixed convection heat transfer in shell and coil heat exchanger
PublicationIn the article, the authors presented the influence of continuous core-baffle geometry at mixed convection heat transfer in shell and coil heat exchanger. Experiments were carried out for a large power range, i.e. from 100W to 1200W and mass flow rates ranging from 0.01 kg/s to 0.025 kg/s. During the experiments, the mass flow rate of cooling water, the temperature of water at the inlet and outlet as well as the wall temperature...
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Heat transfer and pressure drop during flow boiling of pure efrigerants and refrigerant/oil mixtures in tube with porous coating
PublicationW pracy przedstawiono wpływ powłoki porowatej na średni współczynnik przejmowania ciepła oraz opory przepływu podczas wrzenia wybranych czynników chłodniczych wewnątrz poziomych rurek. Badania przeprowadzono dla techniczne czystych czynników chłodniczychR22, R134a i R407C oraz ich mieszanin z olejem poliestrowym 1% i 5% wrzących w rurkach wykonanych ze stali nierdzewnej, o wewnętrznej powierzchni gładkiej oraz z metaliczną powłoką...
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Pool boiling heat transfer of water-Al2O3 and water-Cu nanofluids on horizontal stainless steel smooth and rough tubes
PublicationPrzedstawiono wyniki badań eksperymentalnych przejmowania ciepła przy wrzeniu nanocieczy woda-Al2O3 i woda-Cu na poziomych rurkach ze stali nierdzewnej. Ustalono, że niezależnie od badanej koncentracji nanocząstek (0.01%, 0.1% oraz 1%) współczynnik przejmowania ciepła dla nanocieczy był wyższy niż dla wody i rósł ze wzrostem koncentracji. Ponadto współczynnik przejmowania ciepła dla nanocieczy wzrastał ze wzrostem ciśnienia.
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Natural convective heat-transfers from an isothermal horizontal hemispherical cavity
PublicationPrzedstawiono rozwiązanie analityczne oraz wyniki badań eksperymentalnych i numerycznych konwekcyjnej wymiany ciepła od poziomej izotermicznej kulistej wklęsłej powierzchni.
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Analytical model with non-adiabatic effects for pressure drop and heat transfer during boiling and condensation flows in conventional channels and minichannels
PublicationIn the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for boiling flow and condensation flow with account of non- adiabatic effects for some recent data collected from literature. The first effect, the modification of interface shear stresses in annular flow pattern is considered through incorporation of the so called "blowing parameter". The mechanism of...
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Numerical analysis of the two‐phase steam‐air heat transfer flow induced in smooth and corrugated channel using the VOF model
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THREE-DIMENSIONAL numerical investigation of MHD nanofluid convective heat transfer inside a CUBIC porous container with corrugated bottom wall
PublicationSimultaneous use of porous media and nanofluid as a heat transfer improvement method has recently captivated a great deal of attention. The heat transfer and entropy production of the Cu-water nanofluid inside a cubic container with a heated bottom wavy wall and an elliptic inner cylinder were numerically analyzed in this study. The container is partitioned into two sections: the left side is filled with permeable media and...
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The effect of pressure on heat transfer during pool boiling of water-Al2O3 and water-Cu nanofluids on stainless steel smooth tubes
PublicationPrzedstawiono wyniki badań eksperymentalnych wrzenia nanocieczy woda-Al2O3 i woda-Cu o koncentracjach nanocząstek 0.01%, 0.1% oraz 1% przy ciśnieniu absolutnym 10 kPa, 100 kPa oraz 200k Pa.
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Particle rotation effects in Cosserat-Maxwell boundary layer flow with non-Fourier heat transfer using a new novel approach
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Experimental verification of the theoretical modelof heat transfer between a liquid layer formed by a two-phase impinging jet and a solid surface
PublicationW pracy przedstawiono eksperymentalną weryfikacje modelu teoretycznego wymiany ciepła pomiędzy warstwą wody a stałą powierzchnią. Warstwa cieczy powstała z uderzającej o powierzchnię dwufazowej strugi uderzającej
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The effect of pressure on heat transfer during pool boiling of water-Al2O3 and water-Cu nanofluids on stainless steel smooth tube
PublicationPrzedstawiono wyniki badań eksperymentalnych wrzenia nanocieczy woda-Al2O3 i woda-Cu o koncentracjach nanocząstek 0.01%, 0.1% oraz 1% przy ciśnieniu absolutnym 10 kPa, 100 kPa oraz 200k Pa.
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THREE-DIMENSIONAL NUMERICAL INVESTIGATION OF MHD NANOFLUID CONVECTIVE HEAT TRANSFER INSIDE A CUBIC POROUS CONTAINER WITH CORRUGATED BOTTOM WALL
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Recent advances of selected passive heat transfer intensification methods for phase change material-based latent heat energy storage units: A review
PublicationThe following article overviews recent studies regarding heat transfer enhancement methods, explicitly focusing on fins and coils utilization, in phase change material-based latent heat thermal energy storage systems. It discusses the influence of various geometrical and material parameters on the melting and solidification processes, as well as the orientation of the heat transfer surface within the storage tank. Additionally,...
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Application of Feed Forward Neural Networks for Modeling of Heat Transfer Coefficient During Flow Condensation for Low and High Values of Saturation Temperatur
PublicationMost of the literature models for condensation heat transfer prediction are based on specific experimental parameters and are not general in nature for applications to fluids and non-experimental thermodynamic conditions. Nearly all correlations are created to predict data in normal HVAC conditions below 40°C. High temperature heat pumps operate at much higher parameters. This paper aims to create a general model for the calculation...
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AN OVERVIEW OF HEAT TRANSFER ENHANCEMENT BASED UPON NANOPARTICLES INFLUENCED BY INDUCED MAGNETIC FIELD WITH SLIP CONDITION VIA FINITE ELEMENT STRATEGY
PublicationThe mathematical model of heat generation and dissipation during thermal energy transmission employing nanoparticles in a Newtonian medium is investigated. Dimensionless boundary layer equations with correlations for titanium dioxide, copper oxide, and aluminium oxide are solved by the finite element method. Parameters are varied to analyze their impact on the flow fields. Various numerical experiments are performed consecutively...
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Simulation of hybridized nanofluids flowing and heat transfer enhancement via 3-D vertical heated plate using finite element technique
PublicationThe present study probed the creation of heat energy and concentrating into Newtonian liquids across vertical 3D-heated plates. The role of the Soret and Dufour theories in concentrating and energy formulas is discussed. The role of hybrid nanoparticles is introduced to illustrate particle efciency in terms of solute and thermal energy. It is removed a viscous dissipation process and a changing magnetic feld. The proposed approach...
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Polymerization-Driven Immobilization of dc-APGD Synthesized Gold Nanoparticles into a Quaternary Ammonium-Based Hydrogel Resulting in a Polymeric Nanocomposite with Heat-Transfer Applications
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Wyznaczanie współczynnika przejmowania ciepła podczas wrzenia w przepływie dwutlenku węgla (Prediction of flow boling heat transfer coefficient for carbon dioxide in minichannels)
PublicationW pracy przedstawiono wyniki obliczeń uzyskane za pomocą własnego modelu półemirycznego dla wybranych danych eksperymentalnych dla wrzenia w przepływie dwutlenku węgla. Metoda obliczeniowa została zweryfikowana z danymi eksperymentalnymi Docoulombiera i innych (2011) oraz Mastrullo i innych (2009). Badania eksperymentalne dotyczą pełnego zakresu zmienności stopnia suchości oraz zakresu prędkości masowej G=200-1200 kg/m2s. rozwijany...
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Archives of civil engineering. Intelligent graphic modeler integrating FE analisys of transient heat transfer with early computer-aided design of energy-efficient buildings
PublicationW pracy zaprezentowano nowatorski Modeler Rozmyty, w którym zaimplementowano unikalną koncepcję rozpoznawania. Modeler Rozmyty dokonuje ekstrakcji danych geometrycznych poprzez rozpoznanie i identyfikację niedokładnych i niejednorodnych rysunków, złożonych z prostych obiektów graficznych.
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Analysis of transient heat transfer operation in tube wall.Selected papers from the International Conference on Turbines of Large Output devoted to 100th Anniversary of Prof. Robert Szewalski Birthday.
PublicationW pracy przedstawiono zachowanie się wymiennika ciepła stosowanego w układzie regeneracji turbin parowych w niestacjonarnych warunkach pracy.
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Modelling of heat and mass transfer through wooden buildings
PublicationThe aim of this review paper is to examine the most recent available studies dealing with theoretical, numerical and experimental aspects related to modelling of heat and mass transfer through wooden buildings. The main thermophysical, mechanical and hygrometric properties of wood are firstly discussed. Then, the basic governing equations of heat and mass transfer phenomena are presented. A detailed description of the physical...
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Heat and mass transfer in air-fed pressurised suits
PublicationOpisano konieczność modelowania transportu masy i ciepła w kombinezonach ochronnych. Omówiono różne sposoby modelowania wymiany ciepła, łącznie ze sprzężoną wymianą ciepła. Uwzględniono również ludzki metabolizm i turbulentne mechanizmy wymiany masy i ciepła. Publikacja opisuje również sposób modelowanie turbulentnych przepływów wieloskładnikowych. Pokazano również porównanie obliczeń z eksperymentem.
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Heat and mass transfer in air-fed pressurised suits
PublicationOpisano konieczność modelowania transportu masy i ciepła w kombinezonach ochronnych. Omówiono różne sposoby modelowania wymiany ciepła, łącznie ze sprzężoną wymianą ciepła. Uwzględniono również ludzki metabolizm i turbulentne mechanizmy wymiany masy i ciepła. Publikacja opisuje również sposób modelowanie turbulentnych przepływów wieloskładnikowych. Pokazano również porównanie obliczeń z eksperymentem.
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Theoretical and experimental research of heat and mass transfer in adsorption process in dac systems
PublicationPrzedstawiono badania wymiany ciepła i masy w stałych adsorpcyjnych elementach wykonanych na bazie silikażelu. Zaprezentowano również informacje dotyczące osuszania w systemach klimatyzacyjnych. Na zkończenie pokazano wyniki numerycznej symulacji i skojarzonej wymiany ciepła i masy w chłodzonym osuszaczu.
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Investigation of the flow, heat and mass transfer and emissions in pulverized fuel fired boiler using physical and numerical modeling.
PublicationPraca przedstawia wykorzystanie techniki modelowania fizycznego trójwymiarowego oraz obliczeń numerycznych umożliwiających symulację rzeczywistych procesów spalania paliw stałych i gazowych w urządzeniach energetycznych. Dodatkowo wyniki obliczeń porównano z wynikami modelowania fizycznego oraz pomiarów na obiekcie rzeczywistym.
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Experimental and Computational Fluid Dynamics Studies on Straight and U-Bend Double Tube Heat Exchangers with Active and Passive Enhancement Methods
PublicationIn this work, the authors wanted to demonstrate the possibility to increase the heat transfer efficiency by using simple wire coil inserts to create turbulent flow in the boundary layer as well as air blowing into the annulus of the pipe. Experimental investigations were carried out for four heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend double tube, U-tube with turbulator, plain double...
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Numerical simulation of natural convection of Glycol-Al2O3 nanofluids from a horizontal cylinder
PublicationThis paper deals with natural convection around a circular cylinder with constant heat flux in a cavity using computational fluid dynamics. As fluids ethylene glycol and a mixture of ethylene glycol with Al2O3 nanoparticles (mass concentrations of nanoparticles: 0.1% and 1%) are chosen. Rayleigh number ranges from 3104 to 3105. The nanofluids are modeled with single-phase approach. For the investigated range of nanoparticle concentration, the...
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Pool Boiling of Water–Al2O3 and Water–Cu Nanofluids Outside Porous Coated Tubes
PublicationThis paper deals with pool boiling ofwater–Al2O3 and water–Cu nanofluids on porous coated, horizontal tubes. Commercially available stainless-steel tubes having 10 mm outside diameter and 0.6 mm wall thickness were used to fabricate a test heater. Aluminum porous coatings 0.15 mm thick with porosity of about 40% were produced by plasma spraying. A smooth tube served as a reference tube. The experiments were conducted under different...
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Modeling and experimental investigation of the hydraulic jump in liquid film formed by an impinging two-phase air-water jet
PublicationPrzedstawiono model analityczny układu hydraulicznego powstałego na skutek uderzenia strugi dwufazowej wody i powietrza. Obliczenia porównano z badaniami eksperymentalnymi przeprowadzonymi na własnym stanowisku badawczym. Uzyskano zadowalającą zgodność.
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Modelling of dryout process in an annular flow
PublicationW pracy pokazano teoretyczny model kryzysu wrzenia przy wysokich stopniach suchości, który jest modyfikacją modelu proponowanego wcześniej przez Sedlera i Mikielewicza. Model wysychania filmu cieczowego w przepływie pierścieniowym składa się z różniczkowych równań bilansu masy zapisanych dla filmu na ściance i kropel w rdzeniu przepływu. Rozwiązanie układu równań wymaga znajomości gęstości strumienia masy kropel wytrącających się...
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Impact of Silica Nanofluid Deposition on Thermosyphon Performance
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A Computational Analysis of the Aerodynamic and Aeromechanical Behavior of a Thermo-Well for Steam Temperature Measurement in a Steam Turbine
PublicationThe goal of the paper is twofold: firstly, it presents computational fluid dynamics analysis for finding maximum unsteady flow forces (and their frequencies) acting on a thermo-well for measuring steam temperature in a steam turbine control stage and secondly, it presents computational solid dynamics analysis of possibility of entry into resonance of the thermowell structure. There have been analyzed two cases of flow with changing...
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Effect of Flow Normalization in Micro-Pin-Finned Heat Sink: Numerical Study
PublicationThe micro-pin-fin heat sink (MPFHS) is widely employed for the heat transfer enhancement of microchannel heat sinks. In the current paper, the effect of flow normalization on the thermohydraulic performance of micro-pin-finned heat sinks is studied numerically. Two geometries of MPFHSs, the conventional design micro-pin-fin heat sink (CD-MPFHS) with a uniform-width micro pin fin and the proposed design micro-pin-fin heat sink (PD-MPFHS)...
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Experimental investigations of natural convection from circular plates at variable inclination
PublicationW pracy przedstawiono wyniki badań eksperymentalnych oraz bezwymiarową korelację liczb kryterialnych dla konwekcyjnej wymiany ciepła od izotermicznej płyty kołowej skierowanej ku górze dla różnych kątów pochylenia (od poziomej do pionowej) w szerokim zakresie wartości liczb Rayleigha. Badania przeprowadzono w wodzie dla płyty kołowej o średnicy 0,07 m. Celem pracy było określenie wpływu kąta pochylenia płyty na wartość liczby Nusselta.
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Synergistic effects of a swirl generator and MXene/ water nanofluids used in a heat exchanger pipe of a negative CO2 emission gas power plant
Publicationfocus on optimizing heat exchangers contributes to improved temperature control mechanisms, ensuring the sustainable operation of innovative power plants working towards negative CO2 emissions. In the realm of oxy-combustion within Negative CO2 Emission Power Plants (nCO2PP), the temperature of combustion products surpasses 3000 (K). Addressing this challenge, the imperative arises to reduce these elevated temperatures to a manageable...
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A New Approach for the Mitigating of Flow Maldistribution in Parallel Microchannel Heat Sink
PublicationThe problem of flow maldistribution is very critical in microchannel heat sinks (MCHS). It induces temperature nonuniformity, which may ultimately lead to the breakdown of associated system. In the present communication, a novel approach for the mitigation of flow maldistribution problem in parallel MCHS has been proposed using variable width microchannels. Numerical simulation of copper made parallel MCHS consisting of 25 channels...
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Modeling of heat and fluid flow in granular layers using high-order compact schemes and volume penalization method
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Three-dimensional numerical investigation of hybrid nanofluids in chain microchannel under electrohydrodynamic actuator
PublicationEnergy efficiency enhancement methods have received considerable attentionwithin the industry and scientific community, owing to the rising concern ofglobal energy sustainability. The present article attempts to scrutinize the effectsof electrohydrodynamics and nanofluids on the rate of heat transfer and fluidflow in the 3-D chain microchannels. Improved heat exchangers (e.g., chainmicrochannel) would have a key role in increasing...
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Analytical solution of non-stationary heat conduction problem for two sliding layers with time-dependent friction conditions
PublicationIn this article we conduct an overview of various types of thermal contact conditions at the sliding interface. We formulate a problem of non-stationary heat conduction in two sliding layers with generalized thermal contact conditions allowing for dependence of the heat-generation coefficient and contact heat transfer coefficient on time. We then derive an analytical solution of the problem by constructing a special coordinate...
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Partition of friction heat between sliding semispaces due to adhesion-deformational heat generation
PublicationAnalytical expressions of heat-partition coefficient and contact temperatures for two sliding semispaces with account for adhesion-deformational heat generation and contact heat exchange have been obtained. The rate of deformational heat generation is assumed to decay exponentially with increase of distance from the interface. It has been shown that heat-generation configuration and the intensity of contact heat exchange have impact...
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Jeffreys heat conduction in coupled semispaces subjected to interfacial heating
PublicationA Jeffreys heat conduction problem for coupled semispaces subjected to the action of an interfacial heat source was defined. An analytical solution of the problem was derived for a polynomial specific power of the heat source using the Laplace transform approach. The asymptotic and parametric analysis was performed for different ratios of thermal conductivities , thermal diffusivities , thermal relaxation times and coefficients...
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Verification of the method of reconstructing convective velocity fields on the basis of temperature fields in vertical, differential and equally heated, open and closed channels
PublicationThis paper describes a method of reconstructing velocity fields, i.e. a numerical reconstruction procedure (NRP) that involves the numerical processing of experimentally measured temperature distributions in free convection heat transfer. The NRP consists in solving only the continuity and Navier–Stokes equations with an additional source term. This term is proportional to a known temperature (e.g. from a thermal imaging camera)...
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Perfect thermal contact of hyperbolic conduction semispaces with an interfacial heat source
PublicationThe problem of thermal contact between two bodies with a heat source at their interface presents great scientific and practical interest. On the time scale of a nanosecond or shorter, heat propagation should be considered in the form of thermal waves of finite speeds. This study investigated the thermal behaviour of hyperbolic conduction semispaces in perfect thermal contact subjected to the action of an interfacial heat source....
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Towards enhanced heat and mass exchange in adsorption systems: The role of AutoML and fluidized bed innovations
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Double-diffusive natural convection energy transfer in magnetically influenced Casson fluid flow in trapezoidal enclosure with fillets
PublicationThe prime motive of this disquisition is to deal with mathematical analysis of natural convection energy transport driven by combined buoyancy effects of thermal and solutal diffusion in a trapezoidal enclosure. Casson fluid rheological constitutive model depicting attributes of viscoelastic liquids is envisioned. The influence of the inclined magnetic field governed by Lorentz field law is also considered. To raise the essence...
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A novel concept of enhanced direct-contact condensation of vapour- inert gas mixture in a spray ejector condenser
PublicationAn analytical model of direct steam condensation (DCC) in the novel idea of spray ejector condenser (SEC) in the presence of inert gas has been developed. It is based on continuity, momentum and energy equations for the steam-carbon dioxide mixture and direct contact condensation mechanisms due to heat transfer and concentration. Crucial in the process of DCC is atomisation of the motive fluid in the ejector. The effect of atomised...
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Thermal and solutal performance of Cu/CuO nanoparticles on a non-linear radially stretching surface with heat source/sink and varying chemical reaction effects
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