IMPACT OF RAYLEIGH NUMBER ON A CAVITY CONTAINING A HEATED CIRCULAR CYLINDER FILLED WITH BASE FLUID AND NANOFLUID

Application of nanofluids inside the cavities has been investigated by many researchers, due to importance of using nanofluids to enhance heat transfer and therefore effects of different nanofluids parameters such as type of nanofluid, volume fraction of nanofluid, and its temperature on heat transfer and stream characteristics has been studied. A hot cylinder with radius r and different positions at a high constant temperature (Th) is considered to be located inside the cavity and the side lids are remained at a low constant temperature (Tc). The upper and lower lids are also insulated. Nanofluids used in this problem are considered to be incompressible and Newtonian and the stream is laminar and steady in all areas of the cavity. In a general sense contour and stream pattern, temperature and stream contours in a cavity containing base fluid and a cavity containing nanoparticles are approximately the same for different values of Rayleigh number. In other words, phenomenon such as formation of parallel isotherms at Ra = 104 and formation of Thermal Stratification in higher values of Rayleigh number can be seen in a similar way in all of the contours. Based on present study can be conclude that addition of nanoparticles to the base fluid increases the amount of heat transfer in all points of the lid and amount of this increase is more at upper areas of the lids. Also, increasing Ra number caused a noticeable enhancement in the rate of heat transfer.