Simultaneous effect of staggered baffles and dispersed nanoparticles on thermal performance of a cooling channel (original) (raw)
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CFD Letters, 2021
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Applied Thermal Engineering, 2016
h i g h l i g h t s The forced convection of Al 2 O 3-water nanofluid in a baffled channel is investigated. A layer of agglomerated nanoparticles is formed exactly over the baffle. The presence of nanoparticles has a positive effect on recirculation region. More uniformity of wall temperature is obtained using nanoparticles. The best thermal-hydrothermal performance is found at middle Reynolds number.
Heat and nanofluid transfer in baffled channels of different outlet models
The paper is concerned with the effects of baffled obstacles on steady turbulent Al2O3-H2O nanofluid flow and heat transfer characteristics through channels in different outlet models. The first channel has an outlet as its entrance (case A). The second (case B), third (case C), and fourth (case D) channels have narrow, upper, lower, and central exits, with 45 per cent of their entrance, respectively. These effects are investigated with the help of CFD in a 2D model. The numerical data show improvements in the heat transfer rate of about 45.071, 58.404, 82.413, and 92.433 per cent for cases A, B, C, and D compared to the smooth channel using the same solid volume fraction of Al2O3 nanoparticle, respectively. Among the most effective channels on heat transfer is case D, about 37.658, 21.356, and 9.348 per cent compared to cases A, B, and C, respectively for the maximum value of Reynolds number.
Journal of Thermal Engineering, 2022
Numerical simulations have been carried out to investigate the thermal-hydraulic characteristics using water-based CuO nanofluid with volume fraction (ϕ) = 0 - 5% and fixed nanoparticle size (dp) = 20 nm at Reynolds numbers (Re) = 100 - 389 in a micro-scale backward facing step channel with and without a baffle using finite volume method. The flow is steady, laminar, and incompressible. The channel has an expansion ratio (ER) = 1.9423with a fixed step height (S) of 490 μm. To study the effect of the baffle, different geometrical configurations have been developed by varying its height and location. The height of the baffle is varied as Hb = 160 - 640 μm. The baffle is stationed on the upper wall of the channel at a dimensionless distance (D)= 1, 2, 3 and 4. The upstream, step and upper walls are thermally insulated while the lower wall downstream of the step is under a constant heat flux (qs") = 20000 W/m2. The parameters of interest for analysis are Nusselt number, skin friction coefficient and velocity distribution under different flow conditions. Results indicate that the rise in volume fraction and Reynolds number enhances the Nusselt number, indicating improved heat transfer. However, the skin friction coefficient decreases with the increment in Reynolds number. The increase in baffle height causes the Nusselt number and skin friction coefficient to rise. As the baffle is moved away from the step, the Nusselt number tends to decrease. In comparison to water, the heat transfer improved by about 164% using CuO nanofluid at Re = 389 with ϕ = 5% in the presence of the baffle with Hb = 640 μm and D = 1. However, the heat transfer enhancement has been achieved at the cost of higher pumping power requirements.
Characterization the effects of nanofluids and heating on flow in a baffled vertical channel
International Journal of Mechanical and Materials Engineering, 2019
The laminar 2-D blended convection of the nanofluids at different volume fractions has gained interest in the last decade due to an enormous application in technology. The laminar-flow stream system can be further modified by changing the geometry of the channel, adding an external heating source, and changing the initial conditions at which the stream is being influenced. The investigation of this system includes the variation of the geometrical parameters of the channel, Reynolds number, Nusselt number, and type of the nanoparticles used in preparing the nanofluid with water as the base fluid. These parameters constitute a very successful leading to utilize the numerical solutions by using a finite volume method. Regarding heat flow, one side of the channel was supplied by the heat while the temperature of the other side was kept steadily. The upstream walls of the regressive confronting step were considered as adiabatic surfaces. The nanofluids were made by adding aluminum oxide ...
Scientific Reports, 2022
This study is devoted to the numerical assessment of the influence of helical baffle on the hydrothermal aspects and irreversibility behavior of the turbulent forced convection flow of water-CuO nanofluid (NF) inside a hairpin heat exchanger with 100 mm length, 10 mm inner tube internal diameter, and 15 mm outer diameter internal diameter. The variations of the first-law and secondlaw performance metrics are investigated in terms of Reynolds number (Re = 5000-10,000), volume concentration of NF (ϕ = 0 − 4%) and baffle pitch (B = 25-100 mm). The results show that the NF Nusselt number grows with the rise of both the Re and ϕ whereas it declines with the rise of B. In addition, the outcomes depicted that the rise of both Re and ϕ results in the rise of pressure drop, while it declines with the increase of B. Moreover, it was found that the best thermal performance of NF is equal to 1.067, which belongs to the case B = 33.3 mm, ϕ=2%, and Re = 10,000. Furthermore, it was shown that irreversibilities due to fluid friction and heat transfer augment with the rise of Re while the rise of B results in the decrease of frictional irreversibilities. Finally, the outcomes revealed that with the rise of B, the heat transfer irreversibilities first intensify and then diminish. Abbreviations B Baffle pitch (mm) Be Bejan number C p Specific heat capacity (J/kg.K) D h Hydraulic diameter (m) f Friction factor h Convection coefficient (W/m 2 .K) k Turbulent kinetic energy (m 2 /s 2) k f Thermal conductivity of base fluid (W/m.K) k nf Thermal conductivity of nanofluid (W/m.K) k p Thermal conductivity of nanoparticles (W/m.K) L Length (m) m c Mass flow rate of cold fluid (kg/s) m h Mass flow rate of hot fluid (kg/s)
International Journal of Heat and Mass Transfer, 2014
Nanofluid is a new engineering fluid which could improve the performance of heat exchanger. The aim of this paper is to study the effect of different particle shapes (cylindrical, bricks, blades, and platelets) on the overall heat transfer coefficient, heat transfer rate and entropy generation of shell and tube heat exchanger with different baffle angles and segmental baffle. Established correlations were used to determine the abovementioned parameters of the heat exchanger by using nanofluids. Cylindrical shape nanoparticles showed best performance in respect to overall heat transfer coefficient and heat transfer rate among the other shapes for different baffle angles along with segmental baffle. An enhancement of overall heat transfer coefficient for cylindrical shape particles with 20°baffle angle is found 12%, 19.9%, 28.23% and 17.85% higher than 30°, 40°, 50°baffle angles and segmental baffle, respectively in corresponding to 1 vol.% concentration of Boehmite alumina (c-AlOOH). Heat transfer rate is also found higher for cylindrical shape at 20°baffle angle than other baffle angles as well as segmental baffle. However, entropy generation decreases with the increase of volume concentration for all baffle angles and segmental baffle.
Heat transfer augmentation in the straight channel by using nanofluids
Heat transfer enhancement of nanofluids under turbulent flow through a straight square channel under constant heat flux conditions at the upper and lower walls is studied numerically. The nanofluids are prepared as solid nanoparticles of CuO, TiO 2 and Al 2 O 3 suspended in water. CFD analysis by FLUENT software using the finite volume method is conducted. The boundary conditions are applied under a heat flux of 5000 W/m 2 , Reynolds numbers of 10 4 -10 6 and a constant volume concentration of 1-4%. The results show that the heat transfer rates and wall shear stress increase with an increase of the nanofluids' volume concentration. It seems that the CuO nanofluid significantly enhances heat transfer. The results show good agreement with results of other researchers by a 10% deviation.
Enhance heat transfer in the channel with V-shaped wavy lower plate using liquid nanofluids
Case Studies in Thermal Engineering, 2015
The heat transfer and flow characteristics in corrugated with V-shape lower plate using nanofluids are numerically studied. The computations are performed on uniform heat flux over a range of Reynolds number (Re) 8000-20,000. The governing equations are numerically solved in the domain by a finite volume method (FVM) using the k-ε standard turbulent model. Studies are carried out for different types of nanoparticles Al 2 O 3 ,CuO, SiO 2 and ZnO with different volume fractions in the range of 0-4%. Three different types of base fluid (water, glycerin, ethylene glycol) are also examined. Results indicated that the average Nusselt number for nanofluids is greater than that of the base liquid. The SiO 2 nanofluid yields the best heat transfer enhancement among all other type of nanofluids. Heat transfer enhancement increase with increases the volumetric concentration, but it is accompanied by increasing pressure drop values. Moreover, the average Nusselt number increases with an increase in Reynolds number and volume concentration. The SiO 2 -glycerin nanofluid has the highest Nusselt number compared with other base fluids. The present study shows that these V-shaped wavy channels have advantages by using nanofluids and thus serve as promising candidates for incorporation into efficient heat transfer devices.
Turbulent flow and heat transfer of Water/Al 2 O 3 nanofluid inside a rectangular ribbed channel
ScienceDirect, 2018
In present study, the turbulent flow and heat transfer of Water/Al 2 O 3 nanofluid inside a rectangular channel have been numerically simulated. The main purpose of present study is investigating the effect of attack angle of inclined rectangular rib, Reynolds number and volume fraction of nanoparticles on heat transfer enhancement. For this reason, the turbulent flow of nanofluid has been simulated at Reynolds numbers ranging from 15000 to 30000 and volume fractions of nanoparticles from 0 to 4%. The changes attack angle of ribs have been investigated ranging from 0 to 180. The results show that, the changes of attack angle of ribs, due to the changes of flow pattern and created vortexes inside the channel, have significant effect on fluid mixing. Also, the maximum rate of heat transfer enhancement accomplishes in attack angle of 60. In Reynolds numbers of 15000, 20000 and 30000 and attack angle of 60 , comparing to the attack angle of 0 , the amount of Nusselt number enhances to 2.37, 1.96 and 2 times, respectively. Also, it can be concluded that, in high Reynolds numbers, by using ribs and nanofluid, the performance evaluation criterion improves.