Periodic Unsteady Natural Convection on CNT Nano-powder Liquid in a Triangular Shaped Mechanical Chamber. (August 2022)

• Record Type: Journal Article
• Authors: Hasan, Md. Jahid; Azad, A.K.; Islam, Zahurul; Hossain, Rumman; Rahman, M.M.
• Is Part Of: International Journal of thermofluids. Volume 15(2022)
• Publication Date: 2022-08
• Subjects: Sinusoidal heat source -- CNT-water nano-powder liquid -- Natural convection -- Rayleigh number -- Periodic behavior; Thermodynamics -- Periodicals; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1016/j.ijft.2022.100181
• Languages: English
• ISSNs: 2666-2027

Abstract

Highlights: Sinusoidal heat source is used on natural convection in a triangular chamber using. Water-based CNT-nano powder liquid. Finite element method based Galerkin weighted residual method is applied. Brownian motion is used to calculate thermal conductivity and diffusivity. Rayleigh number (Ra), solid volume fraction (ϕ) of nano powder, and dimensionless time (τ) are assumed as primary controlling factors for fixed value of oscillation period (τp). The fluctuations that categorize variations in thermophysical properties with dimensionless time are periodic and more complicated than the sinusoidal nature of the excitation. Abstract: Nanoparticle is highly used in enhancing thermal performance, especially in lid-driven cavity flow in powder-related applications. Many researchers considered different conditions, such as MHD, radiation, and mixed convection incorporating nano liquid in such flow. However, no study was carried out with CNT-water nano liquid in a triangular cavity, heated sinusoidally under natural convection to determine the Rayleigh number (Ra) and nano-powder liquid concentration effect on heat transfer. As a result, this study attempts to find the Rayleigh number and particle concentration effects in such transient cavity flow. The governing equations were employed with the Galerkin residual method. While calculating the thermal conductivity and dynamic viscosity of the nano liquid, Brownian motion was taken into consideration. The four solid volume fractions (0.01, 0.05, 0.1, 0.15) and the Ra (10 4 ≤ Ra ≤ 10 6 ) were chosen to evaluate the impact within dimensionless time (0.1 ≤ τ ≤ 1). The findings have been shown by plotting the streamlines, isotherms, heat transfer variation, and pressure gradient. It is found that when the Rayleigh number goes up, the velocity, vorticity, and pressure gradient magnitude become high. But, the fluid flow vortices decrease with dimensionless time. Due to the sinusoidal heat flux conditions, the variation of the result was found to be sinusoidal as well. When the nanoparticle concentration rises, the heat transfer rate and average fluid temperature also increase. Therefore, the highest heat transfer rate is found using the nano liquid with a15% concentration.