Numerical study on turbulent natural convection and radiation heat transfer of nanofluids in a differentially heated squ
- PDF / 1,765,398 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 85 Downloads / 213 Views
Numerical study on turbulent natural convection and radiation heat transfer of nanofluids in a differentially heated square enclosure Akash Pravinkumar Patel1 · Divyang Bhatnagar1 · Rajendran Senthil kumar1 · Sethuramalingam Prabhu1 Received: 17 July 2020 / Accepted: 26 October 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Due to the low performance observed during natural convection with fluids such as air and water, nanofluid research was carried out to analyse them for convective heat transfer applications. Heat transfer comparison between water and different water-based nanofluids comprising of MWCNT, alumina and silver has been established for Rayleigh Number 1.5 × 109. Numerical analysis of 2-D differentially heated square cavity has been performed under turbulent natural convection. The top and bottom walls are considered to be at constant temperatures, while the side walls are adiabatic in nature. Based on previous research, nanofluid volume concentration of 0.1 vol% has been considered for this study, and the nature of flow physics and natural convection heat transfer has been explored. It is observed that multiple vortices (almost similar size) exist and evenly speared within the computational domain for air. The viscosity of the fluid was observed to be a deciding factor for the degree of turbulence, thickness and velocity variations within the boundary layer. The average fluid velocity and vortex circulation strength are highest for alumina nanofluid and least for water. The other two nanofluids lie in between with the velocity and vorticity variations of 12.8 and 16.5%, respectively. In terms of heat transfer, alumina nanofluid performs admirably well, followed by MWCNT nanofluid with a variation in radiation heat transfer of 60.8 and 53.19% when compared to air, while for convective heat transfer the variation observed was 98.4 and 97.8%, respectively. Due to the high densities of these nanofluids as compared to air, achieving thermal stratification is difficult. Alumina nanofluid performs admirably well in enhancing convection and radiation heat transfer. Keywords Turbulence · Natural convection · Square enclosure · Nano · CNT · CFD List of symbols Tc Temperature at top (K) TH Temperature at bottom (K) g Gravitational pull (m s−2) Nu Nusselt number Ra Rayleigh number ) ( h Convective heat transfer coefficient mW 2 ⋅K L Length of the square enclosure (m) H Height of the square enclosure ( ) (m) W k Thermal conductivity m⋅K
β Thermal expansion coefficient (K−1) T Surface temperature (K) To, T∞ Bulk mean temperature (K) * Rajendran Senthil kumar [email protected] 1
Department of Mechanical Engineering, SRM Institute of Science and Technology, Kattankulathur, Chennai 603 203, India
α Thermal diffusivity (m2 s−1) v Kinetic viscosity (m2 s−1) Uo Characteristic velocity υT Kinematic eddy viscosity κ Turbulence kinetic energy ω Specific dissipation rate β Coefficient of thermal expansion S Modulus of mean rate of strain tensor t Time Pk Production limiter
Data Loading...
