scholarly journals Numerical Study of Fluid Dynamic and Heat Transfer in a Compact Heat Exchanger Using Nanofluids

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
P. Gunnasegaran ◽  
N. H. Shuaib ◽  
M. F. Abdul Jalal ◽  
E. Sandhita
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
High Surface ◽  
Convective Heat Transfer Coefficient ◽  
Fluid Systems ◽  
Effective Manner

Compact heat exchangers (CHEs) are characterized by a high surface area per unit volume, which can result in a higher efficiency than conventional heat exchangers. They are widely used in various applications in thermal fluid systems including automotive thermal fluid systems such as radiators for engine cooling systems. Recent development of nanotechnology brings out a new heat transfer coolant called “nanofluids,” which exhibit larger thermal properties than conventional coolants due to the presence of suspended nanosized composite particles in a base fluid. In this study, a numerical investigation using different types of nanoparticles in ethylene glycol-base fluid namely copper (Cu), diamond (DM), and silicon dioxide (SiO2) on automobile flat tube plate-fin cross-flow CHE is explored. The nanoparticles volume fraction of 2% is considered for all types of nanofluids examined in this study. The three-dimensional (3D) governing equations for both liquid flow and heat transfer are solved using a standard finite volume method (FVM) for the range of Reynolds number between 4000 and 7000. The standard κ-ε turbulence model with wall function is employed. The computational model is used to study the variations of shear stress, skin friction, and convective heat transfer coefficient. All parameters are found to yield higher magnitudes in the developing and developed regions along the flat tubes with the nanofluid flow than base fluid. The pressure drop is slightly larger for nanofluids but insignificant at outlet region of the tube. Hence, the usage of nanofluids in CHEs transfers more energy in a cost-effective manner than using conventional coolants.

scholarly journals CONVECTIVE HEAT TRANSFER AND POWER SAVING APPLICATION OF SI BASED NANOPARTICLES IN A CIRCULAR PIPE

2020 ◽  
Vol 50 (4) ◽  
pp. 321-327
Author(s):  
Md Insiat Islam Rabby ◽  
Farzad Hossain ◽  
S.A.M. Shafwat Amin ◽  
Tazeen Afrin Mumu ◽  
MD Ashraf Hossain Bhuiyan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Circular Pipe ◽  
Working Fluid ◽  
Pumping Power

A numerical study of laminar forced convection heat transfer for the fully developed region inside a circular pipe filled with Si based nanoparticle is presented for investigating the parameters of heat transfer. Four Si based nanoparticles Si, SiC, SiO2, Si3N4 with 1-5% volume fraction have been mixed with water to prepare nanofluids which is used for working fluid to flow over a circular pipe with 5mm diameter and 700mm length. Heat transfer characteristics and pumping power have been calculated at fully developed region with constant heat flux condition on pipe wall to identify the heat transfer enhancement ratio and pumping power reduction ratio among base fluid water and each nanofluids. It is worth mentioning that utilizing SiC nanoparticle shows not only the highest increment of Nusselt number and convective heat transfer coefficient but also the highest decrement of pumping power requirement and FOM in comparison to the base fluid.

Numerical Simulation of Heat Transfer in Laminar Natural Convection of Mixed Newtonian-Non-Newtonian and Pure Non-Newtonian Nanofluids in a Square Enclosure

2021 ◽  
pp. 1-44
Author(s):  
Ajay Vallabh ◽  
P.S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Base Fluid ◽  
Volume Fraction ◽  
Numerical Study ◽  
Transfer Model ◽  
Nanoparticle Concentration ◽  
Left Wall ◽  
Square Enclosure ◽  
First Case

Abstract This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-Water) and pure Non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/Water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case the nanofluid changes its Newtonian character to Non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case the base fluid itself is Non-Newtonian and the nanofluid behaves as a pure Non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modelling the nanofluids. The present results have been extensively validated with earlier works. In Case I the results indicate that Alumina-Water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II Alumina-CMC/Water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.

scholarly journals Numerical Study of Laminar Forced Convection of Water/Al2o3 Nanofluid in an Annulus with Constant Wall Temperature

2013 ◽  
Vol 14 (1) ◽  
Author(s):  
Amin Kashani ◽  
Davood Jalali-vahid ◽  
Siamak Hossainpour
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Numerical Study ◽  
Flow Behavior ◽  
Convective Heat Transfer Coefficient ◽  
Two Phase ◽  
Constant Wall Temperature ◽  
Laminar Forced Convection

Laminar forced convection of a nanofluid consisting of water and Al2O3 in a horizontal annulus has been studied numerically. Two-phase mixture model has been used to investigate thermal behaviors of the nanofluid over constant temperature thermal boundary condition and with different volume concentration of nanoparticles. Comparisons with previously published experimental and analytical works on flow behavior in horizontal annulus show good agreements between the results as volume fraction is zero. In general convective heat transfer coefficient increases with nanoparticle concentration. ABSTRAK: Kertaskerja ini mengkaji secara numerik olakan paksa bendalir lamina yang menganduangi air dan Al2O3 didalam anulus mendatar. Model campuran dua fasa digunakan bagi mengkaji tingkah laku haba bendalir nano pada keadaan suhu malar dengan kepekatan nanopartikel berbeza. Perbandingan dengan karya eksperimen dan analitikal yang telah diterbitkan menunjukkan bahawa kelakuan aliran didalm anulus mendatar adalah baik apabila pecahan isipadu adalah sifar. Pada amnya, pekali pemindahan haba olakan meningkat dengan kepekatan nanopartikel. KEYWORDS: nanofluid; volume concentration; heat transfer enhancement; laminar flow convection; annulus

Effect of Volume Fraction of Nanoparticles to the Convective Heat Transfer of Nanofluids

2011 ◽  
Vol 464 ◽  
pp. 528-531 ◽  
Author(s):  
Zhi Yong Ling ◽  
Tao Zou ◽  
Jian Ning Ding ◽  
Guang Gui Cheng ◽  
Peng Fei Fu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Fraction ◽  
Small Difference ◽  
Numerical Study ◽  
Convective Heat Transfer Coefficient ◽  
Full Development ◽  
Significant Difference

A numerical study on the convective heat transfer characteristics of Cu-water nanofluid under the laminar flow condition was performed. The results show that the convective heat transfer coefficient increases with the increase of the volume fraction of the nanoparticles and the Reynolds number. There is a significant difference between the numerical simulation result and the result calculated from the Shah equation in the entrance region, but a small difference in full development areas. The numerical results agree well with that obtained from the Xuan equation when the Reynolds number and the volume fraction of the nanoparticles are small, but the errors between them increase as the increase of the Reynolds number and the volume fraction of nanoparticles.

scholarly journals ENHANCEMENT OF EFFICACY AND HEAT TRANSFER CHARACTERISTICS OF TIO2 NANO FLUIDS UNDER TURBULENT FLOW CONDITIONS IN PARABOLIC TROUGH SOLAR COLLECTOR

2020 ◽  
Author(s):  
K.Dilip Kumar ◽  
T.Srinivasa Rao ◽  
M.Srinivas ◽  
K.Ashok Reddy
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Solar Collector ◽  
Base Fluid ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Energy Parameter ◽  
Maximum Efficiency ◽  
Parabolic Trough ◽  
Parabolic Trough Solar Collector

The efficacy of a parabolic trough solar collector (PTSC) was improved by using TiO2/DI-H2O (De-Ionized water) nanofluid. Working samples consisting of nanofluids with concentrations of 0.05%, 0.1%, 0.2%, 0.3% and 0.5% were compared with deionized water (the base fluid) at different flow rates under turbulent flow regimes (2850 ˂Re ˂ 7440). The experiments were designed as per ASHRAE 93 (2010) standards. Heat transfer and the flow characteristics of nanofluids through the collector were studied, and empirical correlations were developed in terms of the Nusselt number, friction factor, and performance index. The convective heat transfer coefficient was improved up to 23.84% by using TiO2 nanofluids instead of the base fluid. It was found that TiO2 nanofluid with a volume fraction of 0.3% (at a mass flow rate of 0.0689 kg/s) will provide the maximum efficiency enhancement in the PTSC (9.66% higher than the water-based collector). Consequently, the absorbed energy parameter was found to be 10.3% greater than that of the base fluid.

scholarly journals Thermal and Fluid Dynamic Performance Comparison of Three Nanofluids in Microchannels Using Analytical and Computational Models

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 754
Author(s):  
Dustin R. Ray ◽  
Roy Strandberg ◽  
Debendra K. Das
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aluminum Oxide ◽  
Copper Oxide ◽  
Wall Temperature ◽  
Base Fluid ◽  
Fluid Dynamic ◽  
Convective Heat Transfer Coefficient ◽  
Pumping Power ◽  
Flux Boundary Condition

The fluid dynamic and thermal performance of three nanofluids containing aluminum oxide, copper oxide, and silicon dioxide nanoparticles dispersed in 60:40 ethylene glycol and water base fluid as a coolant in a microchannel heatsink are compared here by two methods. The first is a simple analytical analysis, which is acceptable for very low nanoparticle volumetric concentration (1–2%). The second method is a rigorous three-dimensional finite volume conjugate heat transfer and fluid dynamic model based upon a constant heat flux boundary condition, which is applicable for cooling electronic chips. The fluids’ thermophysical properties employed in the modeling are based on empirically derived, temperature dependent correlations from the literature. The analytical and computational results for pressure drop and Nusselt number were in good agreement with the nanofluids showing a maximum difference of 4.1% and 2.9%, respectively. Computations cover the practical range of Reynolds number from 20 to 200 in the laminar regime. Based on equal Reynolds number, all of the nanofluids examined generate a higher convective heat transfer coefficient in the microchannel than the base fluid, while copper oxide provided the most significant increase by 21%. Based on the analyses performed for this study, nanofluids can enhance the cooling performance of the heatsink by requiring a lower pumping power to maintain the same maximum wall temperature. Aluminum oxide and copper oxide nanofluids of 2% concentration reduce the pumping power by 23% and 22%, respectively, while maintaining the same maximum wall temperature as the base fluid.

scholarly journals Natural Convection Heat Transfer in Nanofluids: A Numerical Study

2008 ◽  
Author(s):  
W. Rashmi ◽  
A. F. Ismail ◽  
W. Asrar ◽  
M. Khalid ◽  
Y. Faridah
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Base Fluid ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

Natural convection heat transfer in nanofluids has been investigated numerically using computational fluid dynamics (CFD) approach. Analytical models that describe molecular viscosity, density, specific heat, thermal conductivity and coefficient of thermal expansion have been considered in terms of volume fraction and size of nanoparticles, size of base fluid molecule and temperature. The uniform suspensions of different concentrations of Al2O3 in base fluid (water) are considered as nanofluids. Thermal conductivity of the nanofluids has been obtained by solving the governing equations in conjunction with Kinetic model and interfacial layer model using FLUNET 6.3. Numerical simulations have been carried out in a closed pipe for L/D = 1.0. The numerical values of k have also been compared with the experimental values available in the literature. Both the models gave similar predictions with experimentally compared values of k.

Global Effects of MWCNT-W Nanofluid in a Shell & Tube Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 154-159 ◽  
Author(s):  
Islam Md. Shahrul ◽  
I.M. Mahbubul ◽  
Rahman Saidur ◽  
Mohd Faizul Mohd Sabri ◽  
Muhammad Afifi Amalina ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Heat Exchangers ◽  
Base Fluid ◽  
Convective Heat Transfer Coefficient ◽  
Flow Rates ◽  
Tube Heat Exchanger ◽  
Energy Effectiveness ◽  
Mass Flow Rates

Global warming and other problems can be reduced by effectively using the available materials and facilities. Heat exchangers play an important part of the field of energy conservation, conversion and recovery. Shell & tube heat exchangers are widely using in industrial processes and power plants. Suspension of small amounts of nanoparticles into the base fluid called nanofluid can reduce the global energy losses. Thermal conductivity of Multi Walled Carbon Nanotube (MWCNT) is highest among the different nano materials [1]. Therefore, in this paper, the overall performance of a shell & tube heat exchanger has been analytically investigated by using MWCNT-W nanofluid with 0.02-0.1 vol. fractions of MWCNT and compared with water. Mathematical formula, specifications of heat exchanger and nanofluid properties were taken from the literatures to analyze the energy performance and other effects within the system. It is found that for certain mass flow rates of nanofluid and base fluid, the convective heat transfer coefficient increased around 4% to 17% compared to pure water, respectively for 0.02-0.1 vol. fractions of MWCNT in water. However, for constant vol. fractions of MWCNT, convective heat transfer coefficient of the above nanofluid negligibly changed for different mass flow rates. Furthermore, energy effectiveness of the heat exchanger also improved approximately by 3% to 14%, respectively. This energy effectiveness again improved with the decrease of the mass flow rates of nanofluids (tube side) and increase of the mass flow rates of base fluid (shell side). As energy effectiveness is increased by using MWCNT-W nanofluid, therefore, a significant amount of heat losses will be reduced. As a result, with the reduced heat emissions, global warming and greenhouse effects can be reduced by using MWCNT-W nanofluid as working fluid in shell & tube heat exchanger system.

scholarly journals Convective Heat Transfer and Pumping Power Analysis of MWCNT + Fe3O4/Water Hybrid Nanofluid in a Helical Coiled Heat Exchanger with Orthogonal Rib Turbulators

2021 ◽  
Vol 9 ◽  
Author(s):  
Misagh Irandoost Shahrestani ◽  
Ehsan Houshfar ◽  
Mehdi Ashjaee ◽  
Payam Allahvirdizadeh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Exchangers ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Hybrid Nanofluid ◽  
Pumping Power ◽  
Rib Turbulators

Utilizing nanofluids in heat exchangers can lead to improved thermal performance. Nanofluids with suspended carbon nanotubes are specifically desirable in thermal systems because of their unique capabilities. In this study, convective heat transfer and required pumping power are studied simultaneously for a helical coiled heat exchanger with laminar water flow while incorporating 0.1 and 0.3 percent volume fraction of the hybrid nanofluid MWCNT + Fe3O4/water. Two different geometries of bare and ribbed tubes are used for the heat exchanger part. The ribs are chosen to be orthogonal, i.e., 90° with respect to the inclined ones. Three different Reynolds numbers are selected for investigation, all in laminar flow regime based on the non-dimensional M number defined in coiled tubes. Computational fluid dynamics is used to study thermal and fluid behavior of the problem. The convective heat transfer coefficient can serve as a criterion to measure the effectiveness of utilizing nanofluids in heat exchangers by taking the pressure drop and pumping power of the system into consideration. Finally, the artificial neural network curve fitting tool of MATLAB is used to make a good fit in the data range of the problem. It is shown that for most cases of the study, the pumping power ratio is less than 1 that can be considered appropriate from energy consumption viewpoint.

Study of the boundary layer heat transfer of nanofluids over a stretching sheet: Passive control of nanoparticles at the surface

2015 ◽  
Vol 93 (7) ◽  
pp. 725-733 ◽  
Author(s):  
M. Ghalambaz ◽  
E. Izadpanahi ◽  
A. Noghrehabadi ◽  
A. Chamkha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Heat Transfer Enhancement ◽  
Base Fluid ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Enhancement Ratio ◽  
Transfer Enhancement

The boundary layer heat and mass transfer of nanofluids over an isothermal stretching sheet is analyzed using a drift-flux model. The relative slip velocity between the nanoparticles and the base fluid is taken into account. The nanoparticles’ volume fractions at the surface of the sheet are considered to be adjusted passively. The thermal conductivity and the dynamic viscosity of the nanofluid are considered as functions of the local volume fraction of the nanoparticles. A non-dimensional parameter, heat transfer enhancement ratio, is introduced, which shows the alteration of the thermal convective coefficient of the nanofluid compared to the base fluid. The governing partial differential equations are reduced into a set of nonlinear ordinary differential equations using appropriate similarity transformations and then solved numerically using the fourth-order Runge–Kutta and Newton–Raphson methods along with the shooting technique. The effects of six non-dimensional parameters, namely, the Prandtl number of the base fluid Prbf, Lewis number Le, Brownian motion parameter Nb, thermophoresis parameter Nt, variable thermal conductivity parameter Nc and the variable viscosity parameter Nv, on the velocity, temperature, and concentration profiles as well as the reduced Nusselt number and the enhancement ratio are investigated. Finally, case studies for Al2O3 and Cu nanoparticles dispersed in water are performed. It is found that increases in the ambient values of the nanoparticles volume fraction cause decreases in both the dimensionless shear stress f″(0) and the reduced Nusselt number Nur. Furthermore, an augmentation of the ambient value of the volume fraction of nanoparticles results in an increase the heat transfer enhancement ratio hnf/hbf. Therefore, using nanoparticles produces heat transfer enhancement from the sheet.

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