Abstract
Mixed convection of carbon-nanotube/water nanofluid in a vented cavity with an inner conductive T-shaped object was examined under pulsating flow conditions under magnetic field effects with finite element method. Effects of different parameters such as Richardson number (between 0.05 and 50), Hartmann number (between 0 and 30), cavity wall inclination (between 0 ∘ and 10 ∘ ), size (between 0.1 H and 0.4 H) and orientation (between −90 ∘ and 90 ∘ ) of the T-shaped object, and amplitude (between 0.5 and 0.9) and frequency (Strouhal number between 0.25 and 5) of pulsating flow on the convective flow features were studied. It was observed that the average Nusselt number enhanced with the rise of strength of magnetic field, solid nanoparticle volume fraction, and amplitude of the pulsation, while the effect was opposite for higher values of Ri number and cavity wall inclination angle. The presence of the T-shaped object and adjusting its size and orientation had significant impact on the main flow stream from inlet to outlet and recirculations around the T-shaped object and in the vicinity of hot wall of the cavity along with the magnetic field strength. Pulsating flow resulted in heat transfer enhancement as compared to steady flow case for all configurations. However, the amount of increment was different depending on the variation of the parameters of interest. Heat transfer enhancements were 41.85% and 20.81% when the size of the T-shaped object was increased from 0.1 H to 0.4 H. The T-shaped object can be utilized in the vented cavity as an excellent tool for convective heat transfer control. As highly conductive CNT particles were used in water, significant enhancements in the average Nusselt number between 97% and 108% were obtained both in steady flow and in pulsating flow cases when magnetic field was absent or present.
Highlights
The convection in vented cavities play a vital role in ventilating systems, food processing applications, electronic cooling, and many others
Nu number reduces with higher values of Ri number and wall inclination angle but the effect becomes reverse for higher values of Ha number and nanoparticle volume fraction
When pulsating flow was promoted, higher heat transfer rates were found as compared to steady flow configuration
Summary
The convection in vented cavities play a vital role in ventilating systems, food processing applications, electronic cooling, and many others. Conducting or adiabatic solid bodies can be inserted into the vented cavity system to control the fluid flow and convective heat transfer features. Magnetic field effects were used with nanofluids [28,29,30,31,32,33,34] This technology of adding nano-sized particles into the heat transfer fluid was successfully used in many applications including solar power, refrigeration, and convective heat transfer [35,36,37,38,39,40,41,42,43,44]. Even though there are some studies with the pulsating flow in vented cavities, the use of magnetic field, which has the potential to redistribute the separated flow regions within the vented cavity, adds novelty and the method has many control parameters and applicability for many thermal engineering systems, as mentioned above. Numerical results from this study can be beneficial when designing and optimizing thermal configurations related to vented cavities, which have many heat transfer engineering applications, as discussed above
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