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1
Coulson, J. M., J. F. Richardson, J. R. Backhurst i J. H. Harker. "Fluid flow, heat transfer and mass transfer". Filtration & Separation 33, nr 2 (luty 1996): 102. http://dx.doi.org/10.1016/s0015-1882(96)90353-5.
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Makinde, O. D., R. J. Moitsheki, R. N. Jana, B. H. Bradshaw-Hajek i W. A. Khan. "Nonlinear Fluid Flow and Heat Transfer". Advances in Mathematical Physics 2014 (2014): 1–2. http://dx.doi.org/10.1155/2014/719102.
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Muthusamy, P., i Palanisamy Senthil Kumar. "Waste Heat Recovery Using Matrix Heat Exchanger from the Exhaust of an Automobile Engine for Heating Car’s Passenger Cabin". Advanced Materials Research 984-985 (lipiec 2014): 1132–37. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.1132.
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The main objective of our work is to analysis the heat transfer rate for various fluids with different matrix heat exchanger (MHE) models and flow characteristic in matrix heat exchanger by using computational fluid dynamics (CFD) package with small car. The amount of heat carried by the cold fluid from hot fluid is mainly depends upon the mass flow rate of the working fluid. The heat transfer area per unit volume of tube is more. So, it increases the temperature of the cold fluid. Here, the hot and cold fluids are moving in the alternate tubes of heat exchanger in the counter flow direction. The small amounts of pressure drop are occurred but which is less compared to existing model. Flow disturbances are rectified in the MHE through the modifications made. Since, silicon carbide material is used as a polishing material to avoid the deposit of carbon at the inner side of the flow passage and this waste heat energy is used for heating passenger cabin during winter season. The wood is used as an insulating material to avoid the heat flow from fluid to atmosphere. Keywords-Heat transfer rate, Matrix heat exchanger, Working fluid, Polishing material.
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Nallusamy, S. "Characterization of Al2O3/Water Nanofluid through Shell and Tube Heat Exchangers over Parallel and Counter Flow". Journal of Nano Research 45 (styczeń 2017): 155–63. http://dx.doi.org/10.4028/www.scientific.net/jnanor.45.155.
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Nanotechnology has become one of the fastest growing scientific and engineering disciplines. Nano fluids have been established to possess enhanced thermal and physical properties such as thermal conductivity, thermal diffusivity, viscosity and convective heat transfer coefficients. The aim of this research article is to analyze the overall heat transfer coefficient by doing an experimental investigation on the convective heat transfer and flow characteristics of a nano fluid. In this research, an attempt was made for the nano fluid consisting of water and 1% volume concentration of Al2O3/water Nano fluid flowing in a parallel flow, counter flow in shell and tube heat exchanger under laminar flow condition. The 50nm diameter Al2O3nanoparticles are used in this investigation and was found that the overall heat transfer coefficient and convective heat transfer coefficient of nano fluid to be slightly higher than that of the base liquid at same mass flow rate and inlet temperature. Three samples of dissimilar mass flow rates have been identified for conducting the experiments and their results are continuously monitored and reported. The experimental analysis results were concluded that the heat transfer and overall heat transfer coefficient enhancement is possible with increase in the mass flow rate of fluid and Al2O3/water nano fluid on a comparative basis.
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Rao, H. V. "Isentropic recuperative heat exchanger with regenerative work transfer". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, nr 4 (1.04.2000): 609–18. http://dx.doi.org/10.1243/0954406001523948.
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A counter-flow heat exchanger is considered to be the ideal method for recuperative heat transfer between hot and cold fluid streams. In this paper the concept of an isentropic heat exchanger with regenerative work transfer is developed. The overall effect is a mutual heat transfer between the two fluid streams without any net external heat or work transfers. The effectiveness for an isentropic heat exchanger with regenerative work transfer is derived for the case of fluid streams with constant specific heats and it is shown that it is greater than unity. The ‘isentropic effectiveness’ of a heat exchanger is defined. The relationship between the entropy generation and effectiveness for the traditional heat exchanger is also examined and compared with that of the isentropic heat exchanger. The practical realization of isentropic operation of a heat exchanger and its possible application are briefly considered.
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Rajavel, Rangasamy, i Kaliannagounder Saravanan. "Heat transfer studies on spiral plate heat exchanger". Thermal Science 12, nr 3 (2008): 85–90. http://dx.doi.org/10.2298/tsci0803085r.
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In this paper, the heat transfer coefficients in a spiral plate heat exchanger are investigated. The test section consists of a plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot water (hot fluid) is varying from 0.5 to 0.8 kg/s and the mass flow rate of cold water (cold fluid) varies from 0.4 to 0.7 kg/s. Experiments have been conducted by varying the mass flow rate, temperature, and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the Nusselt number which can be used for practical applications is proposed.
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KIMURA, Fumiyoshi, i Kenzo KITAMURA. "A304 FLUID FLOW AND HEAT TRANSFER OF NATURAL CONVECTION ADJACENT TO UPWARD-FACING, INCLINED, HEATED PLATE : AIR CASE(Heat Transfer-1)". Proceedings of the International Conference on Power Engineering (ICOPE) 2009.3 (2009): _3–19_—_3–24_. http://dx.doi.org/10.1299/jsmeicope.2009.3._3-19_.
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Zhou, Guo Fa, i Ting Peng. "Heat Transfer Enhancement of Viscoelastic Fluid in the Rectangle Microchannel with Constant Heat Fluxes". Applied Mechanics and Materials 117-119 (październik 2011): 574–81. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.574.
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It has been found that viscoelastic fluid has evident heat transfer enhancement function in macro scale. But in micro scale, viscoelastic fluid’s flow and heat transfer characteristics are still unknown. In this paper, the heat transfer process of viscoelastic fluid in the microchannel is studied by numerical simulation method. The simulation results show that the maximum heat transfer enhancement of viscoelastic fluid is up to 800%, compared with pure viscous fluid. The viscoelastic fluid has such obvious heat transfer enhancement function because of its strong secondary flow. Laminar sub-layer can be damaged by the strong secondary flow, and thus radial flow generates in laminar sub-layer. The radial flow can increase the interference and mixing effect, and enhances fluid’s turbulence and convection which can enhance heat transfer as a result. So the heat transfer enhancement depends on the intensity of secondary flow which is caused by the second normal stress difference, and it will increase with the raise of the flow rate.
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Yue, Qingwen, Xide Lai, Xiaoming Chen i Ping Hu. "Study on heat transfer characteristics of flow heat coupling of horizontal spiral tube heat exchanger". Thermal Science and Engineering 4, nr 2 (10.09.2021): 23. http://dx.doi.org/10.24294/tse.v4i2.1516.
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In view of the complex structural characteristics and special operating environment of the horizontal spiral tube heat exchanger of the shaft sealed nuclear main pump, the numerical simulation method of flow heat coupling is used to analyze the influence of the flow and temperature changes of the fluid on the shell side on the flow field and temperature field of the heat exchanger, explore the influence rules of the inlet parameters on the flow and heat transfer characteristics of the fluid in the heat exchanger, and analyze the enhanced heat transfer performance of the heat exchanger by using the relevant heat transfer criteria. The results show that the horizontal spiral tube fluid generates centrifugal force under the influence of curvature, forming a secondary flow which is different from the straight tube flow heat transfer, and the velocity distribution is concave arc, which will enhance the heat transfer efficiency of the heat exchanger; with the increase of shell side velocity, the degree of fluid disturbance and turbulence increases, while the pressure loss does not change significantly, and the heat transfer performance of the heat exchanger increases; under the given structure and size, the heat transfer performance curve of the heat exchanger shows that the increase of shell side flow and Reynolds number has a significant impact on the enhanced heat transfer of the spiral tube. In practical engineering applications, the heat transfer can be strengthened by appropriately increasing the shell side flow of the heat exchanger.
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Corzo, Santiago Francisco, Damian Enrique Ramajo i Norberto Marcelo Nigro. "High-Rayleigh heat transfer flow". International Journal of Numerical Methods for Heat & Fluid Flow 27, nr 9 (4.09.2017): 1928–54. http://dx.doi.org/10.1108/hff-05-2016-0176.
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Purpose The purpose of this paper is to assess the Boussinesq approach for a wide range of Ra (10 × 6 to 10 × 11) in two-dimensional (square cavity) and three-dimensional (cubic cavity) problems for air- and liquid-filled domains. Design/methodology/approach The thermal behavior in “differentially heated cavities” filled with air (low and medium Rayleigh) and water (high Rayleigh) is solved using computational fluid dynamics (CFDs) (OpenFOAM) with a non-compressible (Boussinesq) and compressible approach (real water properties from the IAPWS database). Findings The results from the wide range of Rayleigh numbers allowed for the establishment of the limitation of the Boussinesq approach in problems where the fluid has significant density changes within the operation temperature range and especially when the dependence of density with temperature is not linear. For these cases, the symmetry behavior predicted by Boussinesq is far from the compressible results, thus inducing a transient heat imbalance and leading to a higher mean temperature. Research limitations/implications The main limitation of the present research can be found in the shortage of experimental data for very high Rayleigh problems. Practical implications Practical implications of the current research could be use of the Boussinesq approach by carefully observing its limitations, especially for sensible problems such as the study of pressure vessels, nuclear reactors, etc. Originality/value The originality of this paper lies in addressing the limitations of the Boussinesq approach for high Rayleigh water systems. This fluid is commonly used in numerous industrial equipment. This work presents valuable conclusions about the limitations of the currently used models to carry out industrial simulations.
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Ajeeb, Wagd, Monica S. A. Oliveira, Nelson Martins i S. M. Sohel Murshed. "Numerical approach for fluids flow and thermal convection in microchannels". Journal of Physics: Conference Series 2116, nr 1 (1.11.2021): 012049. http://dx.doi.org/10.1088/1742-6596/2116/1/012049.
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Abstract The heat transfer performance of conventional thermal fluids in microchannels is an attractive method for cooling devices such as microelectronic applications. Computational fluid dynamics (CFD) is a very significant research technique in heat transfer studies and validated numerical models of microscale thermal management systems are of utmost importance. In this paper, some literature studies on available numerical and experimental models for single-phase and Newtonian fluids are reviewed and methods to tackle laminar fluid flow through a microchannel are sought. A few case studies are selected, and a numerical simulation is performed to obtain fluid flow behaviour within a microchannel, to test the level of accuracy and understanding of the problem. The numerical results are compared with relevant experimental results from the literature and a proper methodology for numerical investigation of single-phase and Newtonian fluid in laminar flow convection heat transfer in microscale heat exchangers is defined.
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Zhang, Junqiang, Zhengping Zou i Chao Fu. "A Review of the Complex Flow and Heat Transfer Characteristics in Microchannels". Micromachines 14, nr 7 (19.07.2023): 1451. http://dx.doi.org/10.3390/mi14071451.
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Continuously improving heat transfer efficiency is one of the important goals in the field of energy. Compact heat exchangers characterized by microscale flow and heat transfer have successfully provided solutions for this purpose. However, as the characteristic scale of the channels decreases, the flow and heat transfer characteristics may differ from those at the conventional scale. When considering the influence of scale effects and changes in special fluid properties, the flow and heat transfer process becomes more complex. The conclusions of the relevant studies have not been unified, and there are even disagreements on some aspects. Therefore, further research is needed to obtain a sufficient understanding of flow structure and heat transfer mechanisms in microchannels. This article systematically reviews the research about microscale flow and heat transfer, focusing on the flow and heat transfer mechanisms in microchannels, which is elaborated in the following two perspectives: one is the microscale single-phase flow and heat transfer that only considers the influence of scale effects, the other is the special heat transfer phenomena brought about by the coupling of microscale flow with special fluids (fluid with phase change (pseudophase change)). The microscale flow and heat transfer mechanisms under the influence of multiple factors, including scale effects (such as rarefaction, surface roughness, axial heat conduction, and compressibility) and special fluids, are investigated, which can meet the specific needs for the design of various microscale heat exchangers.
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Garai, Anirban, Jan Kleissl i Sutanu Sarkar. "Flow and heat transfer in convectively unstable turbulent channel flow with solid-wall heat conduction". Journal of Fluid Mechanics 757 (19.09.2014): 57–81. http://dx.doi.org/10.1017/jfm.2014.479.
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AbstractMost turbulent coherent structures in a convectively unstable atmospheric boundary layer are caused by or manifested in ascending warm fluid and descending cold fluids. These structures not only cause ramps in the air temperature timeseries, but also imprint on the underlying solid surface as surface temperature fluctuations. The coupled flow and heat transport mechanism was examined through direct numerical simulation (DNS) of a channel flow allowing for realistic solid–fluid thermal coupling. The thermal activity ratio (TAR; the ratio of thermal inertias of fluid and solid), and the thickness of the solid domain were found to affect the solid–fluid interfacial temperature variations. The solid–fluid interface with large (small) thermal activity ration behaves as an isoflux (isothermal) boundary. For the range of parameters considered here (Grashof number, $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Gr} = 3\times 10^5\text {--} 325\times 10^5$; $\textit {TAR} = 0.01\text {--}1$; solid thickness normalized by heat penetration $\text {depth} = 0.1\text {--}10$), the solid thermal properties and thickness influence the fluid temperature only in the viscous or conduction region while the convective forcing influences the turbulent flow. Flow structures influence the interfacial temperature more effectively with increasing TAR and solid thickness compared with a constant temperature boundary condition. The change of channel flow structures with increasing convective instability is examined and the concomitant change of thermal patterns is quantified. Despite large differences in friction Reynolds and Richardson number between the DNS and atmospheric observations, similarities in the flow features were observed.
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Jaworski, Artur J. "Special Issue “Fluid Flow and Heat Transfer”". Energies 12, nr 16 (7.08.2019): 3044. http://dx.doi.org/10.3390/en12163044.
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Mohiuddin Mala, G., Dongqing Li i J. D. Dale. "Heat transfer and fluid flow in microchannels". International Journal of Heat and Mass Transfer 40, nr 13 (wrzesień 1997): 3079–88. http://dx.doi.org/10.1016/s0017-9310(96)00356-0.
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Kryuchkov, I. I., i R. R. Ionaitis. "Heat transfer accompanying a falling fluid flow". Soviet Atomic Energy 66, nr 1 (styczeń 1989): 20–26. http://dx.doi.org/10.1007/bf01121067.
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Shang, Fu Min, Jian Hong Liu i Deng Ying Liu. "Experimental Investigation on the Heat Transfer Characteristics of Nanofluids in Self-Exciting Mode Oscillating-Flow Heat Pipe". Advanced Materials Research 396-398 (listopad 2011): 250–54. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.250.
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The objective of this article is to provide the heat transfer characteristics of Cu-H2O nanofluids in self-exciting mode oscillating-flow heat pipe under different laser heating input, and to compare with the heat transfer characteristics of the same heat pipe with distilled water as working fluids. In this paper, the peculiarity of heat transfer rate of the SEMOS heat pipe with Cu-H2O fluid has been experimentally confirmed by changing the proportion of working fluid and Cu nanoscale particles in the heat pipe. As the results, it has been confirmed that the parameter of filling rate of working fluid determine the heat transfer rate of SEMOS heat pipe, although under certain condition heat transfer performance could be improved because of the addition of nanofluids.
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Gunale, Rahul B., Ashish S. Gajare, Omkar D. Khollam, Aakash G. Gawade i Sanchit S. Salvi. "Experimental Evaluation of Nanofluid for Improved Cooling Efficiency in an AL Mini Channel Heat Sink". International Journal for Research in Applied Science and Engineering Technology 10, nr 5 (31.05.2022): 3400–3406. http://dx.doi.org/10.22214/ijraset.2022.43146.
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Abstract: Efficient heat transfer has become major need these days. In this thesis, both experimental and CFD investigations have to be carried out to evaluate the cooling performance of a mini-channel consisting of fins on upper surface of flat plate. Nano fluids contain a small fraction of solid nano particles in base fluids flowing through groves in bottom plate attached with heater at base. Nano fluids cools small channel heat sinks, have been anticipated to be an excellent heat dissipation method for the next generation electronic devices. Computational Fluid Dynamics (CFD) simulations is to be carried out to study the heat sinks heat transfer mechanism. The sectional geometry of channels affects the flow and heat transfer characteristics of mini channel heat sinks. The heat transfer principle states that maximum heat transfer is achieved in mini channels with minimum pressure drop across it. In this research work the experimental and numerical investigation for the improved heat transfer characteristics of mini channel heat sink using Al2O3/water nano with (1 and 2 % volume fraction) fluid is to be done. The fluid flow characteristics are also analysed for the serpentine shaped mini channel. Heating element of 130 W capacities is to be used to heat up the heating element of base plate. Keywords: Heat, Fluids, Heating, Nano, Fraction, Flow, Sink, Channel, Plate, Aluminum.
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Wen, Xiangyue, Xiting Long i Zhaoying Yang. "Numerical and Analytical Study of Fluid Flow and Thermal Transfer in a Rough Fracture". Geofluids 2022 (31.05.2022): 1–12. http://dx.doi.org/10.1155/2022/2683980.
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The surface morphology of rough fractures significantly affects the fluid flow and heat transfer characteristics in the fractures. A thermal-flow coupling model with specific geometric fractures was established to investigate the influence of surface morphology on the heat transfer characteristics of a single fracture. The effect of temperature on the physical properties of rocks and fluids was included in the study to reflect the actual situation more realistically. The research results show that the temperature of the fluid in the rough fracture is nonlinearly distributed along the flow direction and the higher the flow velocity, the higher the heat transfer efficiency. The fracture surface morphology has a significant impact on the heat transfer characteristics, and the surface fluctuation will greatly affect the flow velocity, causing the fluid temperature to change abruptly at the fracture surface. Under the same flow rate, with the increase of the fluctuation degree of the fracture surface and the fluctuation frequency, the larger the heat exchange area of the fracture surface, the stronger the heat exchange performance. The heat transfer efficiency of the fracture is directly related to the heat transfer area of the fracture, so even with the same permeability, the heat transfer performance of fractures with different surface topography is different.
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Sheremet, Mikhail A., i Ioan Pop. "Natural convection combined with thermal radiation in a square cavity filled with a viscoelastic fluid". International Journal of Numerical Methods for Heat & Fluid Flow 28, nr 3 (5.03.2018): 624–40. http://dx.doi.org/10.1108/hff-02-2017-0059.
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Purpose The purpose of this paper is to study natural convective heat transfer and viscoelastic fluid flow in a differentially heated square cavity under the effect of thermal radiation. Design/methodology/approach The cavity filled with a viscoelastic fluid is heated uniformly from the left wall and cooled from the right side while insulated from horizontal walls. Governing partial differential equations formulated in non-dimensional stream function, vorticity and temperature with corresponding boundary conditions have been solved by finite difference method of second order accuracy. The effects of Rayleigh number (Ra = 1e+3−1e+5), radiation parameter (Rd = 0 − 10), Prandtl number (Pr = 1 − 30) and elastic number (E = 0.0001 − 0.001) on flow patterns, temperature fields, average Nusselt number at hot vertical wall and rate of fluid flow have been studied. Findings It has been found that a growth of elastic number leads to the heat transfer reduction and convective flow attenuation. The heat conduction is a dominating heat transfer mechanism for high values of radiation parameter. Originality/value The originality of this work is to analyze heat transfer and fluid flow of a viscoelastic fluid inside a differentially heated cavity. The results would benefit scientists and engineers to become familiar with the flow and heat behavior of non-Newtonian fluids, and the way to predict the properties of this flow for possibility of using viscoelastic fluids in compact heat exchangers, electronic cooling systems, polymer engineering, etc.
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Gopal, Arumugam, Prabhakaran Duraisamy i Thirumarimurugan Marimuthu. "Experimental Investigation on Heat Transfer and Pressure Drop Characteristics of Food Additive in Dimple Plate Heat Exchanger". Revista de Chimie 73, nr 3 (29.07.2022): 97–109. http://dx.doi.org/10.37358/rc.22.3.8539.
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The present study attempts to examine the heat transfer and pressure drop aspects of a 11-channel dimple plate heat exchanger with hot water as the hot fluid and sodium benzoate (food preservative) as the cold fluid. The outcome of the mass flow rate of hot and cold fluids on the convective heat transfer coefficient and overall heat transfer coefficient were investigated. Furthermore, the effect of Reynolds number on the pressure drop and the Nusselt number were observed. The experimental results demonstrated that when the mass flow rate of the cold fluid increases, so does the overall heat transfer coefficient and the convective heat transfer coefficient. Convective heat transfer coefficient, overall heat transfer coefficient, pressure drop and Nusselt number were increased when sodium benzoate concentration is varied (0.2, 0.4, 0.6% w/w). A correlation is obtained on the basis of experimental results to estimate the Nusselt number as a function of Reynolds and Prandtl number.
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Kumar Gaur, Rohit, Dr Shashi Kumar Jain i Dr Sukul Lomash. "Experimental Investigation on Triple Concentric Tube Heat Exchanger with Helical Baffles". SMART MOVES JOURNAL IJOSCIENCE 6, nr 11 (25.11.2020): 14–20. http://dx.doi.org/10.24113/ijoscience.v6i11.324.
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A heat exchanger is a device used to transfer thermal energy between two or more liquids, between a solid surface and a liquid, or between solid particles and a liquid at different temperatures and in thermal contact where shell and tube heat exchangers contain a large number of tubes packed in a jacket whose axes are parallel to those of the shell. Heat transfer occurs when one fluid flows into the pipes while the other flows out of the pipes through the jacket. In industry, three-tube heat exchanger tubes are used as condensers, evaporators, sub cooler, heat recovery heat exchangers, etc. The three concentric tube heat exchanger is a constructively modified version of the double concentric tube heat exchanger as an intermediate tube adds some advantages over the double tube heat exchangers in that it is larger tube surface area heat transfer per unit of length. In the present study, the triple tube heat exchanger is further modified by inserting helical baffle over the surface of one of the tubes and observed turbulence flow which may lead to high heat transfer rates between the fluids of heat exchanger. Further, the Reynolds number, Nusselt number, friction factor of the flow at different mass flow rates of the hot fluid while keeping a constant mass flow rate of cold and normal temperature fluids were calculated. It was found that as the mass flow rate of the fluid increases the Reynolds number increases, the turbulence in the flow will increase which will cause the intermixing of the fluid, higher the rate of intermixing, more will be the heat transfer of the system.
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Pasupuleti, Ravindra Kumar, Manindra Bedhapudi, Subba Reddy Jonnala i Appa Rao Kandimalla. "Computational Analysis of Conventional and Helical Finned Shell and Tube Heat Exchanger Using ANSYS-CFD". International Journal of Heat and Technology 39, nr 6 (31.12.2021): 1755–62. http://dx.doi.org/10.18280/ijht.390608.
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The summary of the proposed work is to compare the rate of heat transfer, logarithmic mean temperature difference (LMTD) and effectiveness (ε) for a conventional shell and tube heat exchanger with and without helical finned surfaces on tube side of heat exchanger. It is shown that the inlet velocity of cold fluid at the tube side varies, while the inlet velocity of hot fluid at the shell side remains constant. The percentage variations of heat transfer rates with theoretical and simulation methods are compared. The geometry is modelled in ANSYS design modeler and analysis have been carried out in ANSYS-CFD. The inlet velocity of shell side hot fluid is varied in both types of heat exchangers. The proposed work is tested for two configurations of counter flow heat exchanger (conventional and helical finned surfaces) under different shell side inlet velocities of fluids. Helical finned tube heat exchanger with counter flow has a higher LMTD than a conventional counter flow heat exchanger. Variation in heat transfer rates and heat transfer coefficients were observed in heat exchanger influenced by shell side hot fluid velocity. The study shows that helical finned tube surfaces have improved heat transfer rates, LMTD, effectiveness (ε) and overall heat transfer coefficients compared to the conventional heat exchangers.
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Kumar, Shailesh Ranjan, i Satyendra Singh. "Experimental Study on Microchannel with Addition of Microinserts Aiming Heat Transfer Performance Improvement". Water 14, nr 20 (18.10.2022): 3291. http://dx.doi.org/10.3390/w14203291.
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Microchannel technology rapidly established itself as a practicable solution to the problem of the removal of extremely concentrated heat generation in present-day cooling fields. By implementing a better design structure, altering the working fluids and flow conditions, using various materials for fabrication, etc., it is possible to increase the heat transfer performance of microchannels. Two parameters that affect how well a microchannel transfers heat were only recently coupled, and the complicated coupling of the parameter that affects how well a microchannel sink transfers heat is still not well understood. The newest industrial developments, such as micro-electro-mechanical systems, high performance computing systems, high heat density generating future devices, such as 5G/6G devices, fuel cell power plants, etc., all present thermal challenges that require the use of microchannel technology. In this paper, single-phase flow in microchannels of various sizes, with or without microinserts, is described in terms of its thermal-fluid flow properties, including fluid flow characteristics and heat transfer characteristics considering the compound effects of variations of channel size and addition of microinserts. The trials were carried out using distilled water that had thermo-physical characteristics that varied with temperature. A microchannel with microinserts was developed for managing the high heat generation density equipment. The fluid flow and heat transfer characteristics are explored and analyzed for Reynolds numbers ranges from 125 to 4992, for 1 mm channel size, and from 250 to 9985, for 2 mm channel size. The cooling performance criteria are pressure drop characteristics, heat transfer characteristics, and overall performance, whereas the testing parameters were chosen for the variations in channel size and the addition of microinserts. The influence of inserting microinserts on microchannels is discussed. Results suggest that by inserting microinserts, the performance of the heat transfer of microchannels is significantly improved and, also, fluid flow resistance is increased. The criteria of the thermal performance factor are employed to assess the overall performance of the microchannel. Significant intensification of heat transfer is observed with indication that the addition of microinserts to microchannels and reduction in channel sizes exhibited improved overall performance.
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Serizawa, Akimi, i Ziping Feng. "2.13.5 HEAT TRANSFER & FLUID FLOW IN MICROCHANNELS: Two-phase fluid flow". Heat Exchanger Design Updates 9, nr 1-2 (2002): 20. http://dx.doi.org/10.1615/heatexchdesignupd.v9.i1-2.50.
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Zummo, Giuseppe, Zhi-Xin Li, Gian Piero Celata i Zeng-Yuan Guo. "2.13.2 HEAT TRANSFER & FLUID FLOW IN MICROCHANNELS: Single-phase fluid flow". Heat Exchanger Design Updates 9, nr 1-2 (2002): 20. http://dx.doi.org/10.1615/heatexchdesignupd.v9.i1-2.20.
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Kumar, Shailesh Ranjan, i Satyendra Singh. "Numerical Analysis for Augmentation of Thermal Performance of Single-Phase Flow in Microchannel Heat Sink of Different Sizes with or without Micro-Inserts". Fluids 7, nr 5 (24.04.2022): 149. http://dx.doi.org/10.3390/fluids7050149.
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With the development of miniaturized and enormous heat density generating novel technologies, the microchannel heat sink is rapidly establishing itself in modern cooling fields. Enhancement of heat transfer performance of microchannels is done by incorporating improved design structure, changing working fluids and flow conditions, using different materials for fabrication, etc. Coupling of two parameters influencing heat transfer performance of microchannels is in a nascent age, and complex coupling of heat transfer influencing parameters of microchannel sinks has not been clearly understood yet. This study provides the thermal-fluid flow features–fluid flow characteristics and heat transfer characteristics- of single-phase flow in microchannel of different sizes with or without microinserts by the use of computational fluid dynamics. The numerical simulation is performed by employing distilled water with thermophysical properties that depends on temperature for the Reynolds number range of 56–2242. The effect of microinserts on characteristics of fluid flow and heat transfer is analyzed. The results of numerical analysis show that heat transfer performance in microchannel with microinserts is enhanced effectively, however resistance in fluid flow is increased simultaneously. The 0.5 mm microchannel with microinserts shows the best performance of heat transfer characteristics with enhancement of 1–9% in the Reynolds number range of 56–2242 with simultaneous maximum increase in pressure drop by 14.5%. It’s overall performance, evaluated by thermal performance factor, is found to be best among all cases of three different channel sizes with and without microinserts. The maximum enhancement of heat transfer is found to be in case of 0.5 mm channel size with microinserts by a factor of 1.09. The maximum pressure drop is increased is found to be by factor of 2.28 in case of 2 mm channel size with microinserts.
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Rajeh, Taha, Ping Tu, Hua Lin i Houlei Zhang. "Thermo-Fluid Characteristics of High Temperature Molten Salt Flowing in Single-Leaf Type Hollow Paddles". Entropy 20, nr 8 (7.08.2018): 581. http://dx.doi.org/10.3390/e20080581.
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A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten salt flowing in single-leaf type hollow paddles in the view of both the first law and the second law of thermodynamics. The results show that the heat transfer rate of the hollow paddles is significantly greater than that of solid paddles. The penalty of the heat transfer enhancement is additional pressure drop and larger total irreversibility (i.e., total entropy generation rate). Increasing the volume of the fluid space helps to enhance the heat transfer, but there exists an upper limit. Hollow paddles are more favorable in heat transfer enhancement for designs with a larger height of the paddles, flow rate of molten salt and material-side heat transfer coefficient. The diameter of the flow holes influences the pressure drop strongly, but their position is not important for heat transfer in the studied range. Other measures of modifying the fluid flow and heat transfer like internal baffles, more flow holes or multiple channels for small fluid volume are further discussed. For few baffles, their effects are limited. More flow holes reduce the pressure drop obviously. For the hollow paddles with small fluid volume, it is possible to increase the heat transfer rate with more fluid channels. The trade-off among fluid flow, heat transfer and mechanical strength is necessary. The thermo-fluid characteristics revealed in this paper will provide guidance for practical designs.
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Stamenkovic, Zivojin, Milos Kocic, Jasmina Bogdanovic-Jovanovic i Jelena Petrovic. "Nano and micropolar MHD fluid flow and heat transfer in inclined channel". Thermal Science, nr 00 (2023): 170. http://dx.doi.org/10.2298/tsci230515170k.
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Magnetohydrodynamic (MHD) fluid flows attract a lot of attention in the extrusion of polymers, in the theory of nanofluids, as well as in the consideration of biological fluids. The considered problem in the paper is the flow and heat transfer of nano and micropolar fluid in inclined channel. Fluid flow is steady, while nano and micropolar fluids are incompressible, immiscible, and electrically conductive. The upper and lower channel plates are electrically insulated and maintained at constant and different temperatures. External applied magnetic field is perpendicular to the fluid flow and considered problem is in induction-less approximation. The equations of the considered problem are reduced to ordinary differential equations, which are analytically solved in closed form. The influence of characteristics parameters of nano and micropolar fluids on velocity, micro-rotation and temperature fields are graphically shown and discussed. The general conclusions given through the analysis of graphs can be used for better understanding of the flow and heat transfer of nano and micropolar fluid, which have a great practical application. Fluids with nanoparticles innovated the modern era, due to their comprehensive applications in nanotechnology and manufacturing processes, while the theory of micropolar fluids explains the flow of biological fluids and various types of liquid metals and crystals.
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Naghavi, M. R., M. A. Akhavan-Behabadi i M. Fakoor Pakdaman. "Experimental Investigation on Heat Transfer and Pressure Drop of CNT-Base Oil Nano-Fluid Flow in Rectangular Channels under Constant Wall Temperature". Advanced Materials Research 622-623 (grudzień 2012): 806–10. http://dx.doi.org/10.4028/www.scientific.net/amr.622-623.806.
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An experimental investigation has been carried out to study the heat transfer and pressure drop characteristics of MWCNT-Base oil nano-fluid flow inside horizontal rectangular channels under constant wall temperature. The temperature of the tube wall was kept constant at around 95 °C to have isothermal boundary condition. The required data were acquired for laminar fully developed flow inside round and rectangular channels. The effect of different parameters such as mass velocity, aspect ratio of rectangular channels and nano-particles concentration on heat transfer coefficient and pressure drop of the flow is studied. Observations show that the heat transfer performance is improved as the aspect ratio is increased. Also, increasing the aspect ratio will result in the pressure drop increasing. In addition, the heat transfer coefficient as well as pressure drop is increased by using nano-fluid instead of base fluid. Furthermore, the performance evaluation of the two enhanced heat transfer techniques studied in this investigation showed that applying rectangular channels instead of the round tube is a more effective way to enhance the convective heat transfer compared to the second method which is using nano-fluids instead of the base fluid.
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Dawood Jumaah, Itimad, Senaa Kh. Ali i Anees A. Khadom. "Evaluation Analysis of Double Coil Heat Exchanger for Heat Transfer Enhancement". Diyala Journal of Engineering Sciences 14, nr 1 (15.03.2021): 96–107. http://dx.doi.org/10.24237/djes.2021.14109.
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In order to maximize the thermal efficiency of shell and coil heat exchangers, substantial research has been done and geometrical modification is one way to improve the exchange of thermal energy between two or more fluids. One of the peculiar features of coiled geometry is that the temperature distribution is highly variable along the circumferential section due to the centrifugal force induced in the fluid. Moreover, most researchers are concentrated on using a shell and single helical coil heat exchanger to enhance the heat transfer rate and thermal efficiency at different operating parameters. Therefore, the aim of this study is to investigate temperature variation ((T-1, T-2, T-3 and T-4) across a shell and single/double coil heat exchanger at different coil pitches, hot water flow rate, and cold-water flow rate along the outer surface of the coil using experimental and numerical analysis. For single and double coil heat exchangers, Computational Fluid Dynamics (CFD) is carried out using pure water with a hot water flow rate ranging between 1-2 l/min for the coil side heat exchanger. For single coil heat exchangers, the numerical analysis findings showed a good agreement with experimental four-temperature measurement results (T-1, T-2, T-3 and T-4) with an error rate of 1.80%, 3.05%, 5.34% and 2.17% respectively. Moreover, in the current double coil analysis, the hot outlet temperature decreased by 3.07% compared to a single coil (baseline case) at a 2.5L/min hot water flow rate. In addition, increasing the coil pitch will increase the contact between the hot fluid and the coil at a constant hot water flow rate and thereby decrease the hot fluid outlet temperature. Finally, a computational analysis was carried out to examine the flow structure inside single and double coil heat exchangers, and the findings indicated that the effect of centrifugal forces in double coil heat exchangers at various coil pitches caused the secondary flow to be substantially reduced.
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Gorman, John, i Eph Sparrow. "Fluid flow and heat transfer for a particle-laden gas modeled as a two-phase turbulent flow". International Journal of Numerical Methods for Heat & Fluid Flow 28, nr 8 (6.08.2018): 1866–91. http://dx.doi.org/10.1108/hff-04-2018-0144.
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Purpose The purpose of this study is to examine the physical processes experienced by a particle-laden gas due to various types of collisions, different heat transfer modalities and jet axis switching. Here, attention is focused on a particle-laden gas subjected to jet axis switching while experiencing fluid flow and heat transfer. Design/methodology/approach The methodology used to model and solve these complex problems is numerical simulation treated here as a two-phase turbulent flow in which the gas and the particles keep their separate identities. For the turbulent flow model, validation was achieved by comparisons with appropriate experimental data. The considered interactions between the fluid and the particles include one-way fluid–particle interactions, two-way fluid–particle interactions and particle–particle interactions. Findings For the fluid flow portion of the work, emphasis was placed on the particle collection efficiency and on independent variables that affect this quantity and the trajectories of the fluid and of the particles as they traverse the space between the jet orifice and the impingement plate. The extent of the effect depended on four factors: particle size, particle density, number of particles and the velocity of the fluid flow. The major effect on the heat transferred to the impingement plate occurred when direct heat transfer between the impinging particles and the plate was taken into account. Originality/value This paper deals with issues never before dealt with in the published literature: the effect of jet axis switching on the fluid mechanics of gas-particle flows without heat transfer and the effect of jet axis switching and the presence of particles on jet impingement heat transfer. The overall focus of the work is on the impact of jet axis switching on particle-laden fluid flow and heat transfer.
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Saboya, F. E. M., i C. E. S. M. da Costa. "Minimum Irreversibility Criteria for Heat Exchanger Configurations". Journal of Energy Resources Technology 121, nr 4 (1.12.1999): 241–46. http://dx.doi.org/10.1115/1.2795989.
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From the second law of thermodynamics, the concepts of irreversibility, entropy generation, and availability are applied to counterflow, parallel-flow, and cross-flow heat exchangers. In the case of the Cross-flow configuration, there are four types of heat exchangers: I) both fluids unmixed, 2) both fluids mixed, 3) fluid of maximum heat capacity rate mixed and the other unmixed, 4) fluid of minimum heat capacity rate mixed and the other unmixed. In the analysis, the heat exchangers are assumed to have a negligible pressure drop irreversibility. The Counterflow heat exchanger is compared with the other five heat exchanger types and the comparison will indicate which one has the minimum irreversibility rate. In this comparison, only the exit temperatures and the heat transfer rates of the heat exchangers are different. The other conditions (inlet temperatures, mass flow rates, number of transfer units) and the working fluids are the same in the heat exchangers.
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Sathish, T. "Performance Improvement of Base Fluid Heat Transfer Medium Using Nano Fluid Particles". Journal of New Materials for Electrochemical Systems 23, nr 4 (31.12.2020): 235–43. http://dx.doi.org/10.14447/jnmes.v23i4.a03.
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Base fluids like water, ethylene glycolandengineoilare conventionally used as a heat transfer medium. The performance of heat transferred is improved in the conventional fluids with the addition of Nano particles. Hence, this paper considers the forced conventional flow problem over the base fluid within a uniform heated tube placed on a wall. The analysis of heattransferco-efficientis done through a constant Reynoldsnumberfor both Nano and base fluid with a simulation tool. Further, a comparative analysis is carried out with heat transfer coefficient over the base and various Nano fluids. It is seen that the Nano fluids has a better performance due to its better thermal characteristics under standard conditions.
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Asianuaba, Ifeoma B. "Heat Transfer Augmentation". European Journal of Engineering Research and Science 5, nr 4 (25.04.2020): 475–78. http://dx.doi.org/10.24018/ejers.2020.5.4.1869.
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This article presents a brief review of various methodologies applied for heat transfer enhancement in laminar flow convection regime. Experimental setup for laminar flow convection heat transfer enhancement using insertions has been explained along with the associated results. Nusselt’s number is found to be a key parameter for investigatigation in order to perceive the enhancement in heat transfer. Similarly, the magnetohydrodynamic mixed convection heat transfer enhancement technique has also been explored. The results of isotherms and fluid flow parameters are discussed which directly affect the heat transfer coefficient. This review article complements the literature in related field and thus will be helpful in order to carry out further experiments in heat transfer enhancement in future.
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Asianuaba, Ifeoma B. "Heat Transfer Augmentation". European Journal of Engineering and Technology Research 5, nr 4 (25.04.2020): 475–78. http://dx.doi.org/10.24018/ejeng.2020.5.4.1869.
Pełny tekst źródłaStreszczenie:
This article presents a brief review of various methodologies applied for heat transfer enhancement in laminar flow convection regime. Experimental setup for laminar flow convection heat transfer enhancement using insertions has been explained along with the associated results. Nusselt’s number is found to be a key parameter for investigatigation in order to perceive the enhancement in heat transfer. Similarly, the magnetohydrodynamic mixed convection heat transfer enhancement technique has also been explored. The results of isotherms and fluid flow parameters are discussed which directly affect the heat transfer coefficient. This review article complements the literature in related field and thus will be helpful in order to carry out further experiments in heat transfer enhancement in future.
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Naidu P., Sudha Brahma, i P. S. Kishore. "HEAT TRANSFER ENHANCEMENT USING CIRCUMFERENTIAL FINNED TWISTED TAPE HEAT EXCHANGER". International Journal of Research -GRANTHAALAYAH 5, nr 9 (30.09.2017): 152–63. http://dx.doi.org/10.29121/granthaalayah.v5.i9.2017.2225.
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The most desirable feature in any thermal equipment is the enhancement of heat transfer. Heat transfer is basically a slow process and is enhanced by adopting passive or active methods of enhancement. In passive enhancement methods, heat transfer is increased without demanding any external power source; while in active method, enhancement in heat transfer demand external power. In this work, a passive enhancement method is proposed and tested to check the extent of heat transfer enhancement noticed. A tube in shell heat exchanger is designed with circumferential fins attached along the length of tube and a spiral insert running inside the tube. One fluid is made to flow inside the tube under the influence of twisted tape and the shell side fluid is running around the tube continuously provoked by fins. Therefore, the hot and cold fluids were estimated to exchange more heat because of thorough mixing initiated in their flow paths. In this work, analysis was made in CFD package by creating a model that simulates experimentations observed in the literature. The results of experiments and results of CFD analysis were compared. Noticing the agreement between the results, the CFD model is given enhancements like circumferential fins and twisted tape to check the enhancement in heat transfer. The velocity and temperature contours were observed at various flow conditions (Reynolds numbers). Based on results of analysis, thermal performance factor is also estimated to check the increment in heat transfer with reference to hydraulic (or flow) parameters.
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Gupta, Ritu, Parminder Singh i R. K. Wanchoo. "Heat Transfer Characteristics of Nano-Fluids". Materials Science Forum 757 (maj 2013): 175–95. http://dx.doi.org/10.4028/www.scientific.net/msf.757.175.
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Nanofluids are engineered colloids made of a base fluid and nanoparticles, which become potential candidate for next generation heat transfer medium. Nanofluids have higher thermal conductivity and single-phase heat transfer coefficients than their base fluids. The use of additives is a technique applied to enhance the heat transfer performance of base fluids. Recent articles address the unique features of nanofluids, such as enhancement of heat transfer, improvement in thermal conductivity, increase in surface volume ratio, Brownian motion, thermophoresis, etc. A complete understanding about the heat transfer enhancement in forced convection in laminar and turbulent flow with nanofluids is necessary for the practical applications. There are many controversies and inconsistencies in reported arguments and experimental results on various thermal characteristics such as effective thermal conductivity, convective heat transfer coefficient and boiling heat transfer rate of nanofluids. As of today, researchers have mostly focused on anomalous thermal conductivity of nanofluids. Although investigations on boiling, droplet spreading, and convective heat transfer are very important in order to exploit nanofluids as the next generation coolants, considerably less efforts have been made on these major features of nanofluids. This review summarizes recent research on fluid flow and heat transfer characteristics of nanofluids in forced and free convection flows and identifies opportunities for future research.
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Kareemullah, Mohammed, K. M. Chethan, Mohammed K. Fouzan, B. V. Darshan, Abdul Razak Kaladgi, Maruthi B. H. Prashanth, Rayid Muneer i K. M. Yashawantha. "Heat Transfer Analysis of Shell and Tube Heat Exchanger Cooled Using Nanofluids". Recent Patents on Mechanical Engineering 12, nr 4 (26.12.2019): 350–56. http://dx.doi.org/10.2174/2212797612666190924183251.
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Background:: In Shell and Tube Heat Exchanger (STHX), heat is exchanged between hot water (coming from industrial outlet by forced convection) to the cold water. Instead of water, if Nano fluids are used into these tubes, then there is a possibility of improved heat transfer because of high thermal conductivity of the nanofluids. Objective:: From many literature and patents, it was clear that the study of STHX using metal oxide nanoparticles is very scarce. Therefore, the objective of the present investigation is to check the thermal performance of STHX operated with zinc oxide nanofluid and compare with water as the base fluid. Methods:: Heat transfer analysis of a shell and tube heat exchanger was carried out experimentally using Zinc oxide as a nanofluid. Mass flow rate on tube side was varied while on the shell side it was kept constant. Various heat transfer parameters like heat transfer coefficient, heat transfer rate effectiveness and LMTD (Log Mean Temperature Difference) were studied. The experimental readings were recorded after the steady-state is reached under forced flow conditions. Results:: It was found that the effectiveness improves with increase in mass flow rate of nanofluids as compared to base fluid. Conclusion:: From the obtained results, it was concluded that heat transfer enhancement and effectiveness improvement does occur with nano fluids but at the cost of pumping power.
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Lu, Qun Hui, Yang Yan Zheng i Biao Yuan. "A Simulative Study on the Impact of Physical Property Parametersupon Flow and Heat Transfer in Annular Space". Advanced Materials Research 516-517 (maj 2012): 858–65. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.858.
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Through finite volume method, this study establishes a steady state flow and heat transfer model of a single phase flow flowing vertically upward in annular space. The model sets the inner cylinder of the annular space as a heating body with fixed heat generation rate. Flow and heat transfer boundary layers are set between the flow and the inner cylinder wall, in order to give more accurate description of momentum and heat coupling and transfer processes between the fluid and the solid near the wall. Compared with the constant physical property model, the variable physical property model, in which the fluid density, heat transfer coefficient, and viscosity change along with the temperature, has relatively lower heat transfer capacity and a little bit lower interface shear stress between the fluid and the solid heat transfer surfaces. Through the comparison between Re and Ri of the constant physical property model and the variable physical properties model, it can be concluded that the physical property changes of the fluid have gradually lower impact on flow and heat transfer processes along with the acceleration of the forced circulation of the fluid.
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M, Vijayakumar, i Mahendra G. "Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using Tio2 Nanofluid Coolant". International Journal for Research in Applied Science and Engineering Technology 10, nr 4 (30.04.2022): 209–14. http://dx.doi.org/10.22214/ijraset.2022.41171.
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Abstract: The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nano fluids were prepared by adding 0.1 vol. %, 0.2 vol. %, 0.3 vol. % and 0.4 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (60:40). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit./min. for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the Nano fluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with Nano fluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids. Keywords: Heat transfer enhancement, Propylene Glycol, Radiator, TiO2Nanofluid coolant
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Wang, Zhenyu, Jie Wang, Ma Yunhai i Lining Wang. "Structural optimization design and heat transfer characteristics of multi-degree-of-freedom spiral plate type agricultural machinery equipment heat exchanger". Thermal Science 23, nr 5 Part A (2019): 2525–33. http://dx.doi.org/10.2298/tsci181115140w.
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In agricultural equipment, heat exchangers are mainly used for heat exchange and full utilization. Based on the theory of enhanced heat transfer, we establish a reasonable mathematical model and physical model for the multi-degree-of-freedom spiral plate type agricultural machinery heat exchanger, and use the FLUENT numerical simulation software to add the spiral disturbing fluid to the spiral plate heat exchanger flow channel. Numerical simulation and further optimization simulation of the fluid-conducting conditions with poor heat transfer effect were carried out, and an optimal arrangement of two kinds of spiral-shaped turbulent fluids with constant curvature and variable curvature was determined. The heat transfer effect of the fixed-curvature spiral-shaped disturbing fluid is superior. Further optimize the structure of the disturbing fluid. When the diameter of the disturbing fluid increases, the heat transfer can be enhanced; thus, the diameter of the disturbing fluid plays an important role in enhancing the heat transfer effect.
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Hartnett, J. P. "1990 Max Jakob Memorial Award Lecture: Viscoelastic Fluids: A New Challenge in Heat Transfer". Journal of Heat Transfer 114, nr 2 (1.05.1992): 296–303. http://dx.doi.org/10.1115/1.2911275.
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A review of the current knowledge on the fluid mechanics and heat transfer behavior of viscoelastic aqueous polymer solutions in channel flow is presented. Both turbulent and laminar flow conditions are considered. Although the major emphasis is on fully established circular pipe flow, some results are also reported for flow in a 2:1 rectangular channel. For fully established turbulent channel flow, it was found that the friction factor, f, and the dimensionless heat transfer factor, jH, were functions of the Reynolds number and a dimensionless elasticity value, the Weissenberg number. For Weissenberg values greater than approximately 10 (the critical value) the friction factor was found to be a function only of the Reynolds number; for values less than 10 the friction factor was a function of both Re and Ws. For the dimensionless heat transfer coefficient jH the corresponding critical Weissenberg value was found to be about 100. The heat transfer reduction is always greater than the friction factor reduction; consequently, the heat transfer per unit pumping power decreases with increasing elasticity. For fully established laminar pipe flow of aqueous polymer solutions, the measured values of the friction factor and dimensionless heat transfer coefficient were in excellent agreement with the values predicted for a power law fluid. For laminar flow in a 2:1 rectangular channel the fully developed friction factor measurements were also in agreement with the power law prediction. In contrast, the measured local heat transfer coefficients for aqueous polymer solutions in laminar flow through the 2:1 rectangular duct were two to three times the values predicted for a purely viscous power law fluid. It is hypothesized that these high heat transfer coefficients are due to secondary motions, which come about as a result of the unequal normal stresses occurring in viscoelastic fluids. The anomalous behavior of one particular aqueous polymer solution—namely, polyacrylic acid (Carbopol)—is described in some detail, raising some interesting questions as to how viscoelastic fluids should be classified. In closing, a number of challenging research opportunities in the study of viscoelastic fluids are presented.
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Majeed, Amer Hameed, i Yasmin Hamed Abd. "Performance of Heat Exchanger with Nanofluids". Materials Science Forum 1021 (luty 2021): 160–70. http://dx.doi.org/10.4028/www.scientific.net/msf.1021.160.
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The effect of adding nanomaterial of aluminum oxide (Al2O3), titanium oxide (TiO2) and zirconium oxide (ZrO2) in different concentrations of 0.25, 0.5, 0.75, 1.0, and 1.25 g/L to the cold fluid (water) turbulently flowing with different flow rates of 75, 100, 125, 150, and 175 L/min in tube side countercurrently to hot water flowing with a constant flow rate of 60 L/min in the shell side of shell and tube heat exchanger on the heat transfer rates and overall heat transfer coefficients are experimentally studied. It is found that the addition of nanomaterials gives rise to outlet cold (nano) fluids temperatures causing to enhancement averagely 7.74, 11.25, and 17.38 percent for ZrO2, TiO2, and Al2O3 respectively in heat transfer rate and averagely 12.72, 19.47, and 28.71 percent for ZrO2, TiO2, and Al2O3 respectively in overall heat transfer coefficients. The maximum enhancement values in heat transfer rates and in overall heat transfer coefficients are attained at a flow rate of 150 L/min of cold fluid.
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Siddiqui, Abdul, Muhammad Zeb, Tahira Haroon i Qurat-ul-Ain Azim. "Exact Solution for the Heat Transfer of Two Immiscible PTT Fluids Flowing in Concentric Layers through a Pipe". Mathematics 7, nr 1 (14.01.2019): 81. http://dx.doi.org/10.3390/math7010081.
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This article investigates the heat transfer flow of two layers of Phan-Thien-Tanner (PTT) fluids though a cylindrical pipe. The flow is assumed to be steady, incompressible, and stable and the fluid layers do not mix with each other. The fluid flow and heat transfer equations are modeled using the linear PTT fluid model. Exact solutions for the velocity, flow rates, temperature profiles, and stress distributions are obtained. It has also been shown that one can recover the Newtonian fluid results from the obtained results by putting the non-Newtonian parameters to zero. These results match with the corresponding results for Newtonian fluids already present in the literature. Graphical analysis of the behavior of the fluid velocities, temperatures, and stresses is also presented at the end. It is also shown that maximum velocity occurs in the inner fluid layer.
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Chen, Hung Chien, Tzu Chen Hung i Yi Feng Chen. "Numerical Analysis of Heat Transfer in the Concentric Heat Exchanger". Applied Mechanics and Materials 275-277 (styczeń 2013): 572–75. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.572.
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The computational fluid dynamics (CFD) software is used to compute three-dimensional concentric heat exchanger in this research. In order to reduce the burden of the computational time, the concentric heat exchanger is simplified sector of 5° for the regular arrangement of internal shape. The working fluids for hot flow and cold flow are helium and molten salt individually. The arrangements for hot and cold flow paths within a heat exchanger is opposite. This study is mainly focused on the distribution of field for the two layers of concentric heat exchanger. The width of the flow channel as well as the length, pitch, thickness and angle of fin have been changing to analyze the effectiveness-NTU method. The results showed that the best heat transfer of fin thickness, angle, space, length, and flow channel are under 5mm, 5°, 8mm, 44mm, and 12mm, respectively.
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Wardhani, Adinda Shalsa Bellabunda, Alifta Titania Labumay i Erlinda Ningsih. "Influence of Fluid Inflow Rate on Performance Effectiveness of Shell and Tube Type Heat Exchanger". Journal of Mechanical Engineering, Science, and Innovation 2, nr 1 (29.05.2022): 9–15. http://dx.doi.org/10.31284/j.jmesi.2022.v2i1.2993.
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In industrial processes, heat exchangers are needed to transfer a certain amount of heat energy from the system to the environment. The research object observed using a heat exchanger type 1- 2 shell and a tube was water in hot and cold fluids. It aimed to determine the relationship between hot and cold fluids and the heat transfer coefficient, fouling factor, and tool efficiency. The research method varied the hot water by 50, 70, 90, 100 mL/s and the cold water by 20, 40, 60, 80 mL/s. After getting the data for each fluid's inlet and outlet temperatures, the effectiveness analysis was calculated. The research results on the hot fluid variable demonstrated that the more the fluid was flowing into the shell, the higher the heat transfer coefficient, heat transfer velocity, and average effectiveness. Meanwhile, the fouling factor tended to decrease along with the increasing hot fluid. The cold fluid variable, the higher the cold fluid flows into the tube, the higher the heat transfer coefficient and the average heat transfer velocity. Furthermore, the fouling factor and effectiveness tended to decrease along with the increasing cold fluid flow.
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Ningsih, Erlinda, Isa Albanna, Aita Pudji Witari i Gistanya Lindar Anggraini. "PERFORMANCE SIMULATION ON THE SHELL AND TUBE OF HEAT EXCHANGER BY ASPEN HYSYS V.10". Jurnal Rekayasa Mesin 13, nr 3 (31.12.2022): 701–6. http://dx.doi.org/10.21776/jrm.v13i3.1078.
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Heat exchanger type shell and tube, which is the most commonly used heat exchanger in various industries. The efficiency of heat exchangers can be seen from their performance to affect its economy from a process. The purpose is to determine the influence of the hot fluid flow rate and the cold fluid on the overall heat transfer coefficient (U) and log mean temperature difference (ΔTLMTD) values. This simulation is done using Aspen HYSYS V.10 applications and obtained data of the total heat transfer coefficient (U) and ΔTLMTD values. The heat exchanger shell and tube used type 1-2 with single segment type 4 baffle, triangular tube layout, and shell length 1000mm. This simulation results in a hot fluid flow rate compared to reverse with the overall heat transfer coefficient and a cold fluid relative to the overall heat transfer coefficient, with the two best fluid flow rates at 2100 kg/h hot fluid and 1800 kg/h cold fluid at 10400 Kj/oC.h. The influence of the hot fluid flow rate on ΔTLMTD is relative to the straight, while the cold fluid flow rate is relative to the reverse, with the value of the second-best fluid flow rate at the 2100 kg/h hot fluid and the 1800 kg/h cold fluid at 26.25oC
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Shendre, Manoj, i Sandeep Biradar. "Experimental Study on Heat Transfer and Fluid Flow Characteristcs of Shell and Tube Heat Exchanger using hiTRAN Wire Inserts". International Journal of Trend in Scientific Research and Development Volume-2, Issue-2 (28.02.2018): 572–79. http://dx.doi.org/10.31142/ijtsrd9451.
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Yang, Wen-Jei, Shin Fann i John H. Kim. "Heat and Fluid Flow Inside Rotating Channels". Applied Mechanics Reviews 47, nr 8 (1.08.1994): 367–96. http://dx.doi.org/10.1115/1.3111084.
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Power generation and refrigeration accomplished by means of rotating or reciprocating machinery. One of the basic elements of rotating machinery is the rotating channel system. With the desire for ever increasing efficiency in power generation and refrigeration, higher or lower operating temperatures are achieved. It has provided motivation for the pursuit of knowledge on heat transfer and fluid flow characteristics. This paper reviews the literature pertinent to studies of fluid flow and/or heat transfer in channel flows subjected to radial rotation, parallel rotation, and coaxial revolution. Special problems unique to rotating systems are discussed and future study areas are suggested.