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Search results for: MINICHANNEL HEAT EXCHANGER
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Numerical analysis of high temperature minichannel heat exchanger for recuperative microturbine system
PublicationConsidering the development of energy sector, distributed small-scale power generation, e.g., gas micro-CHP, is attracting considerable interest. In such installations, the heat exchanger is one of the key components possessing a significant influence on overall performance. Most studies concentrate on units operating below 900C, which do not fulfil the requirements of gas micro-CHP. Therefore, there remains a challenge to design...
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Flow distribution and heat transfer in minigap and minichannel heat exchangers during flow boiling
PublicationThe topic of boiling heat transfer in miniscale geometries has focused the ever increasing interest of researchers in recent years. However, most of the works are related to mini- and microchannels and much less to minigaps. Meanwhile, minigaps allow for more comprehensive experimental studies, i.e. flow visualisations due to the flat, two-dimensional configuration of the flow. The results of the experimental investigations of...
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Selected studies of flow maldistribution in a minichannel plate heat exchanger
PublicationAnalysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The...
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Pressure drop related to flow maldistribution in a model minichannel plate heat exchanger
PublicationThe paper describes the issues related to the pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger's plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 µm, 571 µm, 750 µm and 823 µm. In addition, the more complex geometry has been investigated,...
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Boiling heat transfer performance of the thermosiphon heat exchanger
PublicationPrzedstawiono wyniki badań eksperymentalnych prototypowego, termosyfonowgo wymiennika ciepła. W szczególności określono wpływ geometrii pęku rur, stanu powierzchni rurek oraz poziomu cieczy w parowniku na wydajność cieplną wymiennika.
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Two-phase thermosiphon heat exchanger for heat recovery
PublicationW pracy przedstawiono wyniki badań eksperymentalnych dotyczących wpływu geometrii pęku rur, rodzaju powierzni przejmowania ciepła parownika oraz płynu pośredniego na całkowitą wydajność dwufazowego termosyfonowego wymiennika ciepła (DTWC). Badaniu poddano sześć prototypowych DTWC z dwiema podziałkami rur w parowniku, dla trzech rodzajów powierzchni rur parownika oraz z zastosowaniem trzech rodzajów płynów pośrednich. Lepszą wydajność...
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Numerical determination of heat exchanger response
PublicationPrzedstawiono metodę przybliżonego obliczania temperatury płynu w ustalonym punkcie wymiennika ciepła i w ustalonej chwili. Wykorzystując nieklasyczny rachunek operatorów można wyznaczyć wzór na odpowiedź wymiennika ciepła, w którym występuje m.in. całka funkcji jednej zmiennej. Do obliczenia wartości całki dla ustalonych parametrów zastosowano wzory Newtona - Cotesa. Podano również oszacowanie błędu przybliżonego obliczania wartości...
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HEAT TRANSFER CHARACTERISTICS OF ENHANCED SHELL AND COIL HEAT EXCHANGER
PublicationIn the paper authors presented their own constructions of shell and tube heat exchangers with intensified heat transfer. The shell and coils heat exchangers are in common use in heat ventilations and air conditioning systems. Those types of recuperators are quite simple constructions, the low value of pressure drops and good conditions of heat transfer. The present study shows an experimental investigation of the heat transfer...
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Heat transfer characteristics of a two-phase thermosyphon heat exchanger
PublicationPrzedstawiono wyniki badań wpływu geometrii parownika, rodzaju rur użytych do budowy parownika, rodzaju cieczy pośredniej oraz poziomu cieczy nad najwyższym rzędem rur na działanie dwufazowego, termosyfonowego wymiennika ciepła. Zaprezentowano algorytm obliczeń przedstawionego wymiennika.
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High Performance Tubular Heat Exchanger with Minijet Heat Transfer Enhancement
PublicationIn the paper, the original cylindrical heat exchanger with minijets (MJHE) was introduced. The systematic experimental analysis of the prototype heat exchanger was described with special attention paid to such parameters as the heat transfer effectiveness, heat transfer rates, overall heat transfer coefficients, and pressure drop. The heat transfer coefficients were determined based on Wilson plot method, the most suitable approach...
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Heat transfer intensification by enlarged surface roughness in the plate heat exchanger
PublicationIn the paper an experimental analysis of passive heat transfer intensification technique employed in the case of the plate heat exchanger is presented. The passive intensification was obtained by a modification of the heat transfer surface. The roughness of surface was increased by a use of glass micro-beads. Single-phase convective heat transfer in the water-water system was studied. The experiment was accomplished in two stages....
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Transient operation analysis of a regenerative heat exchanger.
PublicationReferat dotyczy problemu niestacjonarnej pracy wymiennika regenearcyjnego.Przedstawiono w nim uproszczony model matematyczny pozwalający oszacować w sposób ilościowy wielkość stałych czasowych wymiennika.
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Heat transfer and pressure drop characteristics of the silicone-based plate heat exchanger
PublicationThe paper presents an experimental investigation of a silicone based heat exchanger, with passive heat transfer intensification by means of surface enhancement. The main objective of this paper was to experimentally investigate the performance of a heat exchanger module with the enhanced surface. Heat transfer in the test section has been examined and described with precise measurements of thermal and flow conditions. Reported...
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The influence of microjet array area ratio on heat transfer in the compact heat exchanger
PublicationThe paper describes the comprehensive study on the effect of microjet array geometrical parameters on the heat transfer enhancement in the modular heat exchanger. The conducted experimental study provides an experimental database on single phase submerged microjet heat transfer. The Wilson plot method was applied to determine the heat transfer coefficients in the laminar and transition flow regimes of a liquid-to-liquid heat exchanger....
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Mitigation of the Flow Maldistribution in Minichannel and Minigap Heat Exchangers by Introducing Threshold in the Manifolds
PublicationIn the present paper, a detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel rectangular cross-section (1 mm depth and 1 mm width) minichannels and minigap section (1 mm depth and 99 mm width) with rectangular/trapezoidal manifolds in Z-type flow configuration. The author carried out numerical investigation with various mass flowrates, namely 0.05 kg/s, 0.1 kg/s and 0.2 kg/s which...
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Thermal Analysis Of Hybrid Microchannel-Microjet Heat Exchanger
PublicationThe paper presents the numerical investigation of a microjet- microchannel cooling module. In which microjets of water are impinging into the microchannels and forming a liquid film on the impingement surface. Applied technology takes benefits from two very attractive heat removal techniques. When laminar jets are impinging on the surface have a very high kinetic energy at the stagnation point, also in microchannels boundary layer...
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The effect of heat exchanger geometry on adsorption chiller performance
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Design and experimental investigations of a cylindrical microjet heat exchanger for waste heat recovery systems
PublicationCompact heat exchangers have more and more applications in many areas, including the HVAC, food and petrochemical industry. This paper describes the development of heat exchanger technology for waste heat recovery (WHR) from a range of processes. Case-study testing shows that the proposed heat exchanger can successfully enhance heat transfer and recover waste heat in a range of applications making them economically, environmentally and...
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Heat transfer in plate heat exchanger channels: experimental validation of selected correlation equations
PublicationThis study is focused on experimental investigation of selected type of brazed plate heat exchanger. The Wilson approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The...
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Heat transfer in plate heat exchanger channels: experimental validation of selected correlation equations
PublicationThis study is focused on experimental investigation of selected type of brazed plate heat exchanger. The Wilson approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The...
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Thermal-Hydraulic Studies on the Shell-and-Tube Heat Exchanger with Minijets
PublicationIn this paper a patented design of a heat exchanger with minijets, with a cylindrical construction is presented. It is followed by the results of its systematic experimental investigations in the single-phase convection heat transfer mode. Based on these results, validation of selected correlations (coming from the literature) describing the Nusselt number was carried out. An assessment of the heat exchange intensification level...
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Numerical analysis of high temperature minichannels heat exchanger performance
PublicationNowadays, the most difficult technological challenge in energy sector is connected with the gas micro-CHP units, dedicated to the distributed power generation. They are expected to be of high efficiency and at the same time of compact in size. Regarding the first reason, significant increase in microturbine efficiency can only be achieved by increase in the engine operating temperature. Therefore, one of the critical elements in...
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Performance of a plate heat exchanger operated with water-Al2O3 nanofluid
PublicationThis study is focused on experimental investigation of a selected type of brazed plate heat exchanger (PHEx). The main aim of the paper was to experimentally check the ability of nanofluids to enhance the performance of PHEx. A typical water-Al2O3 nanofluid was tested and compared to that of the base fluid, i.e. water. Nanoparticles were tested at the concentration of 0.1% and 1% by weight. Impact of the 1 day and 3 days break...
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Performance of a plate heat exchanger operated with water-Al2O3 nanofluid
PublicationThis study is focused on experimental investigation of a selected type of brazed plate heat exchanger (PHEx). The main aim of the paper was to experimentally check the ability of nanofluids to enhance the performance of PHEx. A typical water-Al2O3 nanofluid was tested and compared to that of the base fluid, i.e. water. Nanoparticles were tested at the concentration of 0.1% and 1% by weight. Impact of the 1 day and 3 days break...
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Performance of a plate heat exchanger operated with water-Al2O3 nanofluid
PublicationThis study is focused on experimental investigation of a selected type of brazed plate heat exchanger (PHEx). The main aim of the paper was to experimentally check the ability of nanofluids to enhance the performance of PHEx. A typical water-Al2O3 nanofluid was tested and compared to that of the base fluid, i.e. water. Nanoparticles were tested at the concentration of 0.1% and 1% by weight. Impact of the 1 day and 3 days break...
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Zniszczenie korozyjne wymiennika ciepła = Corrosion failure of a heat exchanger
PublicationPłytowy wymiennik ciepła ze stali 316L uległ zniszczeniu po trzech latach eksploatacji, wskutek perforacji po czyszczeniu nieodpowiednim środkiem czyszczącym.
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Experimental investigations on heat transfer enhancement in shell coil heat exchanger with VARIABLE Baffles GEOMETRY
PublicationThe paper presents the possibility of using passive intensification of heat transfer in the form of baffles to increase the energy efficiency of the shell and coil heat exchanger. The experiment was carried out by using a modular coil heat exchanger in the form of an electric heater. Water was used as a working fluid with constant thermal-flow parameters at the inlet of the module. It should be noted that experiments were made...
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Liquid crystal technique application for heat transfer investigation in afin-tube heat exchanger element
PublicationPublikacja przedstawia rezultaty prac autorów w zakresie wykorzystania termografii ciekłokrystalicznej w badaniach wymiany ciepła dla różnych elementów wymienników ciepła. Technika ta z powodzeniem została zastosowana do analizy zabudowy wymiennika na jego efektywność.
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Liquid crystal technique application for heat transfer investigation inafin-tube heat exchanger element
PublicationPublikacja 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.
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Influence of metallic porous microlayer on pressure drop and heat transfer of stainless steel plate heat exchanger
PublicationThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. On the heat transfer surface of heat exchanger the metallic porous layer was created. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified...
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Influence of metallic porous microlayer on pressure drop and heat transfer of stainless steel plate heat exchanger
PublicationThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. The metallic porous layer was created on the heat transfer surface of analyzed unit. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified...
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Experimental study on single phase operation of microjet augmented heat exchanger with enhanced heat transfer surface
PublicationThe article presents experimental investigations on a prototype heat exchanger. Presented research is focused on combined active and passive enhancement techniques of surface modification and microjet impingement. The results were compared to reference plate heat exchanger without microjet impingement. The Wilson plot method was applied to determine the heat transfer coefficients in the single phase operation. The heat exchanger...
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Thermodynamic and geometrical characteristics of mixed convection heat transfer in the shell and coil tube heat exchanger with baffles
PublicationThe article presents passive heat transfer enhancement method in the form of baffles to increase the energy efficiency of the shell coil heat exchanger. Conducted literature review shows that, despite numer- ous studies, there is little work on the intensification of heat transfer at the shell side. Most of the work focuses on the impact of geometrical parameters of the coil itself. This article successfully proves that it is possible...
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Effect of surface roughness on thermal-hydraulic characteristics of plate heat exchanger
PublicationIn the paper the experimental analysis of passive heat transfer intensification in the case of modeled plate heat exchanger is conducted. The plate heat exchanger is chosen for the analysis because this kind of heat exchangers could be prospectively applied in the ORC systems, however other areas or application are equally possible. The experimental setup was assembled at the Department of Energy and Industrial Apparatus of Gdansk...
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Plate heat exchanger with porous structure for potential use in ORC system
PublicationThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. The passive intensification was obtained by a modification of the heat transfer surface, which was covered by a metallic porous microlayer. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one...
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Plate heat exchanger with porous structure for potential use in ORC system
PublicationThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. The passive intensification was obtained by a modification of the heat transfer surface, which was covered by a metallic porous microlayer. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one...
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Experimental and numerical simulations of flow and heat transfer in heat exchanger elements using liquid crystal thermography.
PublicationW artykule przedstawiono założenia oraz sposób prowadzenia eksperymentu i obliczeń numerycznych wymiany ciepła w modelu wymiennika ciepła przy użyciu termografii ciekłokrystalicznej.
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EFFECT OF NANOFLUID CONCENTRATION ON TWO-PHASE THERMOSYPHON HEAT EXCHANGER PERFORMANCE
PublicationAn approach – relaying on application of nanofluid as a working fluid, to improve performance of the two-phase thermosyphon heat exchanger (TPTHEx) has been proposed. The prototype heat exchanger 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. Distilled water and nanofluid water-Al2O3...
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Optimization of the distance between the vertical plates in the convective air heat exchanger
PublicationThis paper examines the influence of the distance between vertical plates on the intensity of free convective heat transfer along with the optimization of this distance. Experimental tests were carried out for one model channel of such an heat exchanger with widths , 0.085 and 0.18 m. This channel, open at the top and sides, was formed by two isothermal symmetrically heated parallel vertical plates of dimensions m and m. The influence...
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Experimental investigation of two-phase thermosyphon heat exchanger charged with acetone
PublicationThis 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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Experimental investigation of heat transfer enhancement in straight and U-bend double-pipe heat exchanger with wire insert
PublicationIn this paper, the possibility of heat transfer enhancement in the U-bend exchanger was presented. Experimental research has been carried out for four individual heat exchanger constructions i.e. plain tube in tube, turbulized tube in tube, plain U-bend and U-bend with turbulator. Also, heat transfer experiments for various boundary conditions were performed to obtain reference values. In case of U-bend exchanger with and without...
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Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness
PublicationThe shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil,centrifugal force is acting on the moving fluid due to the curvature of thetube results in the development. It has been long recognized that the...
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The low temperature waste heat recovery in drying process of pine wood using micro-jet heat exchanger
PublicationThe article presents the influence of the drying medium temperature changes for the relative and absolute moisture content values during pine wood drying. The drying process was conducted at constant atmospheric pressure and with different drying medium (air) temperature levels, respectively: 40oC, 60oC, 80oC, 100oC, and 120oC. In order to develop a method that would enable low temperature drying of solid materials the experiments...
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Thermal performance of a prototype plate heat exchanger with minichannels under boiling conditions
PublicationTo solve the problem and to meet the requirements of customers in the field of high heat fluxes transfer in compact units, a new design of plate heat exchanger with minichannels (minichannels PHE) was proposed. The aim was to construct a compact heat exchanger of high effectiveness for the purpose of household cogeneration ORC system. In this paper the experimental analysis of an assembled prototype of such compact heat exchanger...
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A simple approach to heat exchanger sizing optimisation by means of entrophy generation minimisation
PublicationIn the paper an attempt is presented to find the method of optimization of microtube diameter with respect to optimal thermal-hydraulic conditions in the single-phase shell-and-tube heat exchangers. The approach is based on consideration of pumping power at the condition of maximum heat transfer by the heat exchanger tube system. In the optimization method the tube diameter is first specified and then appropriate calculations are...
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Selection Of Optimal Working Fluid For Use With Hybrid Microchannel-Microjet Heat Exchanger
PublicationThe paper presents the investigation to find best suited working fluid for a microjet- microchannel cooling module. In which microjets are impinging into the microchannels and forming a liquid film on the impingement surface. This technology takes benefits from two very attractive heat removal techniques. When laminar jets are impinging on the surface have a very high kinetic energy at the stagnation point, also in microchannels...
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EFFECT OF WORKING FLUID SELECTION ON THERMAL PERFORMANCE OF HEAT EXCHANGER FILLED BY THE POROUS MATERIAL
PublicationThermal management of electronics semiconductor technologies that are located i.e. in a novel marine power plants or computer server rooms become very important issue for designers of such systems. Motivation and need for research in development of novel cooling strategies for modern electronics is of paramount importance. Heat exchangers filled by the porous material are a novel research topic in current heat pipe science. The...
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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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A new construction of shell-and-tube heat exchanger with impinging jets and minichannels technologies for heat recovery from gases – experimental analysis
PublicationA dynamic development of technologies allowing waste heat utilization is observed in a correspondence with a pro-ecological approach of the zero waste idea. Such approach becomes the most demanding in the area of low-temperature was heat sources, especially gaseous media. Till now, they were usually not utilized due to unfavorable thermal conditions and high costs. Therefore, the zero waste approach directs research on techniques...
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Numerical modeling of cross-flow heat exchanger for air-conditioning purposes in preliminary study.
PublicationPraca przedstawia wyniki obliczeń numerycznych krzyżowego płytowo-rurowego wymiennika ciepła przeznaczonego do celów klimatyzacyjnych w początkowym etapie jego projektowania.
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Channel Blockage and Flow Maldistribution during Unsteady Flow in a Model Microchannel Plate heat Exchanger
PublicationThis paper describes the problem of channel blockage as a result of flow maldistribution between the channels of a model mini channel plate heat exchanger consisting of one pass on each leg. Each leg of the heat exchanger contains 51 parallel and rectangular minichannels of four hydraulic diameters namely 461 μm, 571 μm, 750 μm and 823 μm. In addition, a more complex geometry has been investigated where for the sake of breaking...
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Monitoring Regenerative Heat Exchanger in Steam Power Plant by Making Use of the Recurrent Neural Network
PublicationArtificial Intelligence algorithms are being increasingly used in industrial applications. Their important function is to support operation of diagnostic systems. This paper pesents a new approach to the monitoring of a regenerative heat exchanger in a steam power plant, which is based on a specific use of the Recurrent Neural Network (RNN). The proposed approach was tested using real data. This approach can be easily adapted to...
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Corrosion-erosion damage of heat exchanger tubes by desalted crude oil flowing at shell side.
PublicationRurki wymiennika zostały uszkodzone lokalnie przez odsoloną ropę naftową przepływającą pod ciśnieniem 2,6 MPa i w temperaturze 385-395K. Większość powierzchni rurek nie była uszkodzona i była pokryta osadem związków organicznych i nieorganicznych, zabezpieczającym przed uszkodzeniami. Badania wykluczyły możliwość występowania intensywnej korozji elektrochemicznej na powierzchniach rurek pozbawionych osadu. Przyczyną perforacji...
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Corrosion-erosion damage of heat exchanger tubes by desalted crude oil flowing at shell side
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Thermal and economic investigation of straight and U-bend double tube heat exchanger with coiled wire turbulator
PublicationExperimental research has been carried out for four individual heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend and U-bend with turbulator. Tests were made for the water-water system. The study covered a wide measuring range, i.e., Re = 800–9000 – on the shell side, for a constant cold water temperature of 9 ◦C and hot water of 50 ◦C. The heat exchangers were made from copper tubes with...
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Experimental investigation on straight and u-bend double tube heat exchanger with active and passive enhancement methods
PublicationAuthors in this work want 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. In the study, Wilson plot approach was applied in order to estimate heat transfer coefficients for all heat exchanger (HX) configurations. The study focuses on experimental values of heat transfer coefficient...
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Selected aspects of two-phase flow studies using different visualization techniques in minichannels
PublicationThe subject of the study is to present the possibility of the use of visualization techniques in the researches on two-phase flows, carried out by the authors for many years. These works included as follows: heat transfer during the flow boiling, boiling crises and condensation in flow. The issue of the heat transfer intensification during the flow boiling through the channels of small diameters was analyzed. All this work focused...
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CHARAKTERYSTYKA WYMIANY CIEPŁA I OPORÓW PRZEPŁYWU OMYWANIA MIKROSTRUGAMI ROZWINIĘTEJ POWIERZCHNI
PublicationW artykule przedstawiono eksperymentalne badania kompaktowego wymiennika ciepła z intensyfikacją przejmowania ciepła przy użyciu mikrostrug. Niniejszy artykuł przedstawia projekt i testy prototypu, wymiennika ciepła typu mikrostrugowego. Modułowa konstrukcja wymiennika umożliwia zmianę wymiarów geometrycznych, a także zmianę materiału przegrody wymiennika ciepła. Metoda graficzna Wilsona została z zastosowana w celu określenia...
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Analytical and reliability data from the real-time simulator biogas plant
Open Research DataThe dataset represents the results of biogas plant simulation. The described plant is an agricultural biogas system, which can produce electrical energy with power estimated up to 1070 kW and heat energy that can reach 1200 kW simultaneously.
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Testing an evaporator operation with a concave manifold, condenser temperature 30, evaporator temperature 70 and preheater temperature 60
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a bifurcation manifold, condenser temperature 20 and evaporator temperature 85
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a concave manifold, condenser temperature 30, evaporator temperature 70 and preheater temperature 40
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a trapezoidal manifold, condenser temperature 90 and evaporator temperature 90
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a bifurcation manifold, condenser temperature 20 and evaporator temperature 70
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a rectangular manifold, condenser temperature 30 and evaporator temperature 90
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a trapezoidal manifold, condenser temperature 70 and evaporator temperature 60
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a bifurcation manifold, condenser temperature 20 and evaporator temperature 95
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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Testing an evaporator operation with a bifurcation manifold, condenser temperature 20 and evaporator temperature 90
Open Research DataThe experiment was conducted to test the evaporator operation. The heat exchanger was equipped with minigeometry (set of 50 parallel minichannels or single minigap). The studies were conducted for various mass flow rate of the working fluid and for various temperatures at the inlet of the evaporator. Accurate information about the test rig, the parameters...
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INTENSYFIKACJA WYMIANY CIEPŁA W WYMIENNIKU WĘŻOWNICOWYM Z WYKORZYSTANIEM PRZEGRÓD O RÓŻNEJ GEOMETRII
PublicationW pracy zaprezentowano możliwości wykorzystania pasywnej intensyfikacji wymiany ciepła w postaci przegród dla podniesienia efektywności energetycznej wymiennika wężownicowego. Badania zostały przeprowadzone z wykorzystaniem modułowego wymiennika z wężownicą w postaci grzałki elektrycznej. Medium odbierającym ciepło była woda o stałych parametrach cieplnoprzepływowych na wlocie do modułu. Pomiary przeprowadzono dla szerokiego zakresu...
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Jan Wajs dr hab. inż.
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Charakterystyka eksploatacyjna pomp ciepła zainstalowanych w oczyszczalni ścieków
PublicationW artykule przedstawiono charakterystykę eksploatacyjną sprężarkowych pomp ciepła zainstalowanych w oczyszczalni komunalnej i wykorzystujących ścieki oczyszczone jako dolne źródło ciepła. Zastosowanie ścieków oczyszczonych jest uzasadnione ich dostępnością oraz stosunkowo wysoką temperaturą (10-25°C). Prawidłowa eksploatacja układu wymaga zastosowania pośredniego obiegu parowacza oraz regularnych zabiegów czyszczenia wymiennika...
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Wykorzystanie ciepła niskotemperaturowego do procesu suszenia peletu ze słomy z wykorzystaniem mikrostrugowego wymiennika ciepła
PublicationW artykule przedstawiono wpływ temperatury medium suszącego na zmiany względnej oraz bezwzględnej zawartości wilgoci podczas suszenia peletu ze słomy. Proces suszenia przeprowadzono przy stałym ciśnieniu atmosferycznym i różnych wartościach temperatury powietrza, jako czynnika suszącego, wynoszących odpowiednio: 40℃, 60℃, 80℃, 100℃ oraz 120℃. Badania eksperymentalne wykonywano na innowacyjnym stanowisku wyposażonym w mikrostrugowy...
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Applicability of arrays of microjets heat transfer correlations to design compact heat exchangers
PublicationThe article presents experimental studies on a compact heat exchanger with heat transfer intensification by means of impinging microjets. The pursuit to provide high performance of heat exchangers is a response to the demand both in economics and in the universal tendency to miniaturization of industrial equipment. This paper presents the design and tests of a prototype, microjet heat exchanger. The modular design of the heat exchanger...
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Thermal-FSI modeling of flow and heat transfer in a heat exchangerbased on minichanels
PublicationIn this paper selected numerical modelling problems for an advanced thermal-FSI ("Fluid Solid Interaction") mini-channel heat exchanger model are presented. Special attention is given to the heat transfer between the separated mediums for different mass flows. Similar modelling problems have also been discussed in the literature dedicated to numerical and theoretical modelling problems for typical heat exchangers [1, 2, 3]. Basic...
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Flow maldistribution and its mitigation in mini heat exchangers
PublicationIn the present paper, a detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel 1 mm x 1 mm rectangular minichannels and 1 mm depth minigap section with rectangular, trapezoidal, triangular or concave mani-folds in Z-type flow configuration (16 different cases). The working medium was ethanol and the mass flow rate was 5×10-4 kg/s. Both sections was heated from the bottom side. Heat...
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Thermohydraulic maldistribution reduction in mini heat exchangers
PublicationA detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel 1 mm × 1 mm rectangular minichannels and 1 mm depth minigap section with rectangular, trapezoidal, triangular or concave manifolds in Z-type flow configuration. The working medium was ethanol and the mass flow rate was 5 × 10−4 kg/s. Both sections were heated from the bottom side. Heat flux of 10 000 W/m2 and 5000 W/m2 was...
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HEAT TRANSFER ENGINEERING
Journals -
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
Journals -
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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Recuperator with microjet technology as a proposal for heat recovery from low-temperature sources
PublicationA tendency to increase the importance of so called dispersed generation, based on the local energy sources and the working systems uti- lizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for...
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Recuperator with microjet technology as a proposal for heat recovery from low-temperature sources
PublicationA tendency to increase the importance of so called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative...
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Minichannel and minigap classification criteria based on the aspect ratio of the minigeometry: A numerical study
PublicationA detailed numerical investigation has been carried out to analyze the diabatic flow distribution and velocity profile in 18 minigeometries with various aspect ratios for V-type and I-type flow configurations (for 36 cases) assuming ethanol as a working fluid. The aim of the study is to distinguish the value of the aspect ratio for which the flow in minigeometry starts to be two-dimensional (minigap). Cases with a constant Reynolds...
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Experimental study of flow boiling pressure drop and heat transfer of R1233zd(E) at moderate and high saturation temperatures
PublicationThe paper presents the results of experimental study of flow boiling of R1233zd(E) in minichannel at moderate and high saturation temperatures. The heat transfer coefficient and pressure drop were measured for flow boiling in a stainless steel tube with 2 mm inside diameter and a length of 300 mm. Experiment has been conducted for saturation temperatures ranging from 83 to 145 °C which corresponds to values of reduced pressures...
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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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An advanced thermal-FSI approach of an evaporation of air heat pump
PublicationThe paper presents selected problems of numerical modeling of an advanced thermal-FSI approach of evaporator of air heat pomp. The example of a fin-tube evaporator has been studied, focusing on obtaining of heat exchanger characteristics applying two-phase flow model for the in-tube refrigerant flow. Special attention is given to heat transfer between separated medium for different air velocity and changed refrigerant mass flow...
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Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
PublicationTwo-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evap- orator. The transferred heat and the pressure drop predicted by simulation have been compared with the corresponding experimental data taken from the literature. Two dimensional analyses of the louvered fins with varying...
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Microjet technology as a perspective intensification method for high performance heat exchangers
PublicationIn the paper two oryginal designs of compact heat exchangers with intensification effect produced by microjets are presented. The technology of microjets manufacturing is an "inhouse" patented design. The idea of such heat exchanger is shown together with the flow and thermal characteristics of the prototypes. The results of performer measurements are satisfactory and encourage for further research of the original designs.
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High-efficiency mini and micro heat exchangers for dispersed power generation
PublicationTaking into account the dispersed systems technologies and their development, the ORC systems seem to be promising technology amongst various micro-CHP domestic units (electrical power production below 10 kWe), however practical realization of the ORC cycle in a micro-scale is technically challenging. The system consists in devices such as the vapour generation unit (boiler), expansion device and heat exchangers. Each of them should...
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High-temperature heat pumps – potential technology for heat recovery and production of process heat
PublicationIn the paper, the high temperature vapour compressor based heat pump with a selection of working fluids, both perspective and ecological ones, is considered. Such system is not yet commercially available on the market and in author’s opinion it has significant potential for various applications. In the presented analysis it was assumed that the heat source has a temperature of 50oC and the temperature lift is 60, 80 and 100K respectively....
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Comparison of various flow maldistribution quantification methods in mini heat exchangers
PublicationThe aim of study is to compare various flow maldistribution quantification methods, using velocity, mass flow rate, pressure, and temperature. An experimentally validated numerical study has been prepared and a heat exchanger with 34 semi-circular channels with a diameter of 3.1 mm has been tested. The minichannels were heated from the bottom with a heat flux of 50, 60, 70, and 80 kW/m2. The cases for various inlet velocities of...
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Heat transfer and heat exchangers
e-Learning CoursesOmówienie głównych mechanizmów i praw przenoszenia ciepła. Przykłady rozwiązywania zagadnień z przewodzenia ciepła, konwekcji i radiacji. Podstawy teorii rekuperatorów. Przykłady obliczania pół powierzchni rekuperatorów.
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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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Natural convective heat transfer from isothermalconic
PublicationTheoretical considerations on convective heat transfer from isothermal upward conicalsurfaces have been presented. The physical model of this phenomenon consists of an isothermalcone of inclination angle (φ) between the cone generating line (X) and the radius (R) of the cone base. The angle is a parameter of conical surface which varied from (φ = 0−circular horizontal plate) to (φ = π/2—vertical cylinder) . Onthe basis of Navier–Stokes...
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Modelling of heat transfer in supercritical pressure recuperators
PublicationIn the paper presented is analysis of convective flow heat transfer at supercritical pressure in channels of heat exchanger working in the thermodynamic cycle. The modelling is based on the division of the flow into three regions, namely the heavy fluid, a two phase flow consisting of the heavy and light fluids and finally the light fluid flow. Modelling is concentrated on the region of simultaneous flow of two fluids divided into...
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Selected prtoblems of heat ans mass transfer
e-Learning CoursesThew lecture presentes advanced topics in heat ans mass transfer
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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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A closed loop thermosyphon with conventional or minichannel based condenser and evaporator
PublicationPrzedstawiono uogólniony model termosyfonu, który może być rozpatrywany dla szeregu wariantów.Model opiera się na jednowymiarowych równanich masy, pędu i energii. Rozpatrzono dwa przypadki termosyfonu, tj. grzanie strony pionowej i chłodzenie strony pionowej oraz drugi, gdzie termosyfon jest ogrzewany na stronie pionowej a chłodzony na poziomej.
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Possibilities of heat transfer augmentation in heat exchangers with minichannels for marine applications
PublicationIn the paper, new trends in development of microchannel heat exchangers are presented. The exchangers developed in this way can be applied in marine applications. Main attention was focused on heat exchangers design with reduced size of passages namely based on microchannels. In our opinion future development of high power heat exchangers will be based on networks micro heat exchangers.
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Numerical Study of Turbulent Flow and Heat Transfer of Nanofluids in Pipes
PublicationIn this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (Reynolds number between 6000 and 12000) with constant heat flux boundary condition using nanofluids. The nanofluid is modelled with the single-phase approach and the simulation results are compared with experimental data. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid...
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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....