بررسي بهبود انتقال گرما درون نانو سيال به كمك روش شبكه بولتزمن

چكيده انگليسي :

Heat transfer enhancement with the use of Nanofluids Using Lattice Boltzmann modeling Mohammadreza Nabavitabatabayi Email mr nabavitabatabaei@me iut ac ir April 19 2010 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 8311 Iran Degree M Sc Language Farsi Supervisor Professor Ebrahim Shirani Email eshirani@cc iut ac ir Abstract Nanofluids liquid nanoparticles laden mixture mitigate some problems accompanied with conventional microfluids such as abrasion clogging rapid sedimentation and high pressure drop This work investigates the heat transfer performance in an enclosure including nanofluids with localized heat source The discrepancies found in the literature as to whether the dispersion of nanopaticles in the base liquid improves the heat transfer performance or not intrigued us to become more resolute to attack this problem using a mesoscopic method called multiple relaxation time lattice Boltzmann modeling To the best knowledge of the authors no studies have been done before to investigate the heat transfer in an enclosure which includes nanofluids using mesoscopic methods let alone that the enclosure includes the localized heat source which has a broad application in micro cooling devices The results clearly demonstrate the superior numerical efficiency of the lattice Boltzmann modeling over the classical CFD In this work the velocity field is solved by Multi Relaxation Time lattice Boltzmann MRT scheme however the advection diffusion equation is solved separately by thermal lattice Boltzmann The fields are then coupled together using Boussinesq approximation Consequently the objective of this study is to investigate the influence of several pertinent parameters such as Rayleigh number solid particle volume fraction of nanoparticles and the geometry and location of the localized heat source on the heat transfer performance of nanofluid using LBM in which both Dirichlet and Newmann boundary conditions are implemented The results obtained from lattice Boltzmann clearly indicate that heat transfer augmentation is possible using nanofluids in comparison to conventional fluids resulting in the compactness of many industrial devices Some results obtained through this endeavor are presented below The increase of Rayleigh numbers strengthens the natural convection flows which results in the reduction of heat source temperature The increase of solid volume fraction of nanoparticles causes the heat source maximum temperature to decrease particularly at low Rayleigh numbers where conduction is the main heat transfer mechanism The increase of heat source length increases the heat transfer to the nanofluid and therefore increases the surface temperature of the heat source and the strength of natural convection circulating cells within the enclosure As the heat source moves from the left wall towards the middle of the bottom wall of the enclosure at low Rayleigh numbers the heat source maximum temperature continuously increases Key Words Heat transfer Nanofluids Lattice Boltzmann Modeling

نبوي طباطبائي، محمدرضا

بررسي بهبود انتقال گرما درون نانو سيال به كمك روش شبكه بولتزمن

معادلات بقايي