Numerical study of fins arrangement and nanofluids effects on three-dimensional natural convection in the cubical enclosure (original) (raw)
Related papers
ScienceDirect, 2020
In this numerical study, natural flow and heat transfer of nanofluids with Al 2 O 3 , TiO 2 , Cu and CNT nanoparticles in a vertical channel with dimpled fins at Rayleigh number (Ra) of Ra = 3.25 × 10 7 to Ra = 1 × 10 8 are investigated by using the finite volume method. The obtained results revealed that, using CNT in volume fractions of 2% and 4% leads to significant heat transfer and at φ = 6%, using TiO 2 nanoparticles has a great effect on Nu number enhancement. Also, using solid nanoparticles in base fluid causes more uniform heat transfer distribution, especially in areas close to heated surface and by adding more volume fraction in base fluid, temperature level reduces. In general, according to temperature contours, reduction of wall temperature depends on the increase of Ra and volume fraction and the type of solid nanoparticles.
International Journal of Heat and Fluid Flow, 2008
Heat transfer and fluid flow due to buoyancy forces in a partially heated enclosure using nanofluids is carried out using different types of nanoparticles. The flush mounted heater is located to the left vertical wall with a finite length. The temperature of the right vertical wall is lower than that of heater while other walls are insulated. The finite volume technique is used to solve the governing equations. Calculations were performed for Rayleigh number (10 3 6 Ra 6 5 Â 10 5 ), height of heater (0.1 6 h 6 0.75), location of heater (0.25 6 y p 6 0.75), aspect ratio (0.5 6 A 6 2) and volume fraction of nanoparticles (0 6 u 6 0.2). Different types of nanoparticles were tested. An increase in mean Nusselt number was found with the volume fraction of nanoparticles for the whole range of Rayleigh number. Heat transfer also increases with increasing of height of heater. It was found that the heater location affects the flow and temperature fields when using nanofluids. It was found that the heat transfer enhancement, using nanofluids, is more pronounced at low aspect ratio than at high aspect ratio.
International Communications in Heat and Mass Transfer, 2011
A numerical study was performed for the laminar forced convection of water over a bank of staggered micro fins with cross section of the elongated hexagon. A 3-dimensional mathematical model, for conjugate heat transfer in both solid and liquid is developed. For this aim the Navier-Stokes and energy equations for the liquid region and the energy equation for the solid region are solved simultaneously and the pressure drop as well as the heat transfer characteristics was investigated. The length and width of the studied heat sinks are one centimeter and different heights in the range of 200-500 micrometer were examined for the fluid media. The heat removal of the finned heat sink is compared with an optimum simple mirochannel heat sink. The comparison which is presented at equal pumping powers depicts the enhancement of the heat removal for some specific sizes of the finned heat sink.
Numerical study on buoyancy driven heat transfer utilizing nanofluids in a rectangular enclosure
A numerical study on heat transfer enhancement utilizing nanofluids in a two-dimensional enclosure was investigated for various pertinent parameters using commercial CFD code FLUENT 6.3. Numerical simulations were carried out assuming nanofluid as single phase. Effect of Rayleigh number ranging from 6 3 10 10 ≤ ≤ Ra and nanoparticle volume fraction (0-20%) was studied on flow pattern and energy transport within the thermal boundary layer for aspect ratio of 1.0. Stream function and isotherm contours were plotted for all the above mentioned parameters. Results show that effect of buoyancy parameter and volume fraction causes increase in average heat transfer enhancement. The results were also compared with the khanafer's model and found to be in good agreement.
Heat transfer enhancement in cubical enclosures with vertical fins
Applied Thermal Engineering, 2007
Natural convection of air in a cubical enclosure with a thick partition fitted vertically on the hot wall is numerically investigated for Rayleigh numbers of 10 3-10 6. A three dimensional convective circulation is generated, in which the cold flow sweeps the fin faces and the hot wall, with low flow blockage. The combined contributions of these faces cause heat transfer enhancements over 40% at high Rayleigh numbers and thermal conductivity ratios (R k). These enhancements significantly exceed the ones obtained with horizontal fins. Even low R k values cause heat transfer enhancements, except at Ra = 10 4 .
Natural Convection and Thermal Radiation Influence on Nanofluids in a Cubical Cavity
International Journal of Heat and Technology
This study investigates the effect of thermal radiation on natural convection of several water-based nanofluids H2O-(Cu, Al2O3, Ag, TiO2) in a partially heated cubical cavity where the left vertical side is heated by three identical and parallel elements. The right vertical side is totally cooled, and the other ones are kept adiabatic. A developed code based on the finite volume method and the Rosseland approximation is used to solve the governing equations. Calculations were performed for three inclination angles of the rectangular heating elements 0°, 45° and 90°. The effect of governing parameters, namely, Rayleigh number, solid volume fraction, radiation parameter, dimensionless spacing of the three heating elements, their aspect ratio and different type of nanoparticles on the velocity contours, isotherms as well as local and average Nusselt number were considered. The results indicate that the inclination angle has a considerable effect on the dynamic and thermal fields, but its effect on the average heat transfer is insignificant. The total Nusselt number increases with the volume fraction of nanoparticles, the radiation parameter and the aspect ratio of the heated elements. The numerical results also revealed that the Cu and Ag-water nanofluid offer a better heat exchange.
International Journal of Simulation Modelling, 2012
Numerical analysis is performed to examine the heat transfer enhancement of Au, Al 2 O 3 , Cu and TiO 2 water-based nanofluids. The analysis uses a two-dimensional enclosure under natural convection heat transfer conditions and has been carried out for the Rayleigh number range 10 3 ≤ Ra ≤ 10 5 , and for the nanoparticles' volume fraction range 0 ≤ φ ≤ 0,10. The governing equations were solved with the standard finite-volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. Highly accurate numerical results are presented in the form of average Nusselt number and heat transfer enhancement. The results indicate clearly that the average Nusselt number is an increasing function of both, Rayleigh number and volume fraction of nanoparticles. The results also indicate that heat transfer enhancement is possible using nanofluids in comparison to conventional fluids, resulting in the compactness of many industrial devices. However, low Rayleigh numbers show more enhancement compared to high Rayleigh numbers.