Oil-based nanofluids are used to strengthen the stability of nanofluids as well as their thermophysical properties when they are exposed to high temperatures. The time-dependent thermophysical ...characteristics of multiwalet carbon nanotubes for kerosine oil-based nanofluid are numerically explored in this study. Considering a constant magnetic field, the radiative domain is examined in a lid-driven squared shape cavity with a semicircular heater on the middle part of the bottom wall. The Galerkin residual technique based on finite elements is used to obtain nonlinear dimensionless governing equations. Thermal conductivity along with dynamic viscosity models integrate Brownian motion of nanoparticles. The Reynolds number, the Hartmann number, the Radiation Parameter and the Richardson number are assumed to be constant to account for the fluctuation in solid volume fraction (ϕ = 0% to 10%). The results demonstrated that particle concentration improves the nanofluid’s thermophysical properties from 1 to 9 times than the 0% concentration and the heat transfer rate from 1 to 3 times. In addition, dimensionless time enhances all except the heat transfer rate and drag force of the sliding lid. It is worth noting that the considered parameter exhibits consistent behavior after a while.
This work conducts a numerical analysis of thermal radiation with a semicircular heater on the middle part of the bottom wall and a sliding lid on the top in a square enclosure. Magnetohydrodynamic ...(MHD) unsteady mixed convection for kerosene oil-based CNT nanofluid is studied. The finite element-based Galerkin residual technique is used to obtain nonlinear dimensionless governing equations. The thermal conductivity and dynamic viscosity models incorporate nanoparticle Brownian motion. Simulations were conducted for Reynolds number = 100, Hartmann number = 10, Richardson number = 1, and particle concentration = 0.05. The effects of fluid velocity magnitude, pressure gradient, temperature gradient magnitude, average temperature, bulk temperature, drag force of the sliding lid, and Nusselt number of the semicircular heater were investigated for different radiation parameters and dimensionless time. Results showed that increasing radiation intensity and dimensionless time improves fluid velocity, pressure gradient, and temperature gradient but decreases the heat transfer rate of the semicircular heater. Furthermore, the drag force of the moving lid is likewise found to be substantially dependent on the radiation parameter as well as dimensionless time. It is worth noted that after a while, the considered parameter exhibits consistent behavior.
An enclosure with a moving lid is commonly used in heat and mass transmission. Also, many investigations have been done so far on a mixed convective flow in a cavity, but no research has been done to ...observe the low Reynolds number effect in the presence of MHD and radiation in a cavity with a semi-circular heater incorporated kerosine oil-based CNT nanofluid. In addition, oil-based nanofluid makes the working fluid more stable at a higher temperature. This study numerically investigates the time-dependent effect of low Reynolds number on Kerosene oil-based CNT nanofluid with magnetic field and radiation. The governing equations were employed with the finite element method based Galerkin residual technique. Brownian motion of nanoparticles was considered to determine the thermal conductivity and dynamic viscosity. Lower values of Reynolds number are taken, such as 50 to 200 with fixed values of radiation parameter, the particle concentration, the Hartmann number, and the Richardson number. The results were illustrated as heat transfer and fluid flow for three dimensionless time conditions. Results indicate that increasing the fluid velocity improves the Nusselt number and drag force. The vorticity rises to 54% while increasing the fluid velocity, however, the pressure gradient and average temperature become lower. It is also found that the average fluid velocity is 2.2 times higher in the Re = 50 than in the Re = 100. For the time dependency of this study, the thermo-hydrodynamics behavior changes with dimensionless time. Finally, this study would be a guide for designing thermal devices related to heat transfer, especially using the Kerosene oil-based CNT nanofluid under different conditions.
•Kerosene oil-based CNT nanofluid is used as working fluid.•Semi-circular heater is chosen as heat source in the square shaped cavity.•Effect of Re under radiation and mixed convection is evaluated in a cavity.•The magnetic field hinders the fluid flow and heat transfer.•Higher velocity of moving lid ensures better heat transfer rate and drag force.
This research examines the natural convection phenomena in a triangular enclosure, assumed as a mechanical chamber. Water-based CNT-nanofluid was used as the fluid. The nature of the flow is ...unsteady, and a sinusoidal heat source is situated at the bottom of the triangle. The inclined two walls of the triangle are assumed as cold temperature. Based on the finite element method, dimensionless nonlinear governing equations were obtained employing the Galerkin weighted residual method. Brownian motion of nanoparticles was considered to determine the thermal conductivity and dynamic viscosity. Rayleigh number (Ra), oscillation period τp, and dimensionless time τ are assumed as primary controlling factors, and nanofluid concentration is considered as constant φ = 0.04. The result indicates that the heat transfer rate displays varied patterns varying the Rayleigh number, and it rises as the oscillation period increases. The fluid temperature and flow fields exhibit periodic behavior due to the sinusoidal heat source. The findings of this work can be utilized to build an effective cooling or heating system for the mechanical chamber, ensuring that temperature distributions are effective and consistent.
•Sinusoidal heat source is used on natural convection in a triangular chamber using. Water-based CNT-nanofluid.•Finite element method based Galerkin weighted residual method is applied.•Brownian motion is used to calculate thermal conductivity and diffusivity.•Rayleigh number, oscillation period and dimensionless time are assumed as primary controlling factors.•Fluctuations of thermophysical properties with time are periodic and more complex than sinusoidal nature of the excitation.
Double-diffusive mixed convection problem had been a notable topic of research in the last decade. Lack of study is noticed under mixed convection using this double-diffusive in an enclosure ...specifically for roof-based ventilation systems with unsteady, partially heated conditions. This study investigates the Prandtl number effect in a double-diffusive unsteady flow in a square-shaped room where the upper channel was used for ventilation, and inside the enclosure, the walls are partially heated and mass concentrated. Galerkin residual method was implemented to get the governing equations. The Prandtl number 0.071 ≤ Pr ≤ 7.1 was chosen for the study, changing the dimensionless time 0.1 ≤ τ ≤ 1. The results have been shown in the mode of graphical representation and contour plots to observe the Prandtl number effect in such problem. The velocity streamline, isotherm, isoconcentration plots, heat and mass transfer rate, average fluid temperature and average mass concentration, etc., are shown. Results showed that heat and mass transfer rise with the growth of the Prandtl number. This research would be the guide for the design consideration in such double-diffusive systems like roof-based air ventilation systems with partial heat and mass generation.
•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.
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 (104 ≤ Ra ≤ 106) 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.
The goal of the paper is to evaluate the characteristics of the fluid flow, heat, and contaminant transfer in an indoor air environment. A two-dimensional ventilated space having a discrete heat and ...contaminant source at their mutually perpendicular position is constructed to conduct a numerical study. The governing equations with apprupirate boundary conditions of the model are evaluated by Galerkin weighted residual method. The transport characteristics are discussed for varying Richardson number 0.1 ≤ Ri ≤ 10 and dimension less time 0.1 ≤ τ ≤ 1 by the corresponding stream function, heat function, and mass function. Priority is given to analyzing the necessary factors – dependence on average Nusselt number, average Sherwood number, the average fluid temperature and mass concentration in the enclosure, along with the average temperature of the exit port to visualize the ventilation technique. Numerical output illustrates that – the attributes of the transport particles are largely determined by the interaction of the natural convection of heat and contaminant source with the mechanically forced flow of cool air. Results showed that mixed convection method is a better way to showcase efficient ventilation of the transport particles from the enclosure through a practical yet non-complex approach. This study will be a guide for design consideration for roof-based double-diffusive systems with partial heat and mass generation.
The main objective of the study is to investigate the fluid flow pattern and thermal behavior of time-dependent 2-dimensional lid-driven cavity flow in the presence of mixed convection. The ...square-shaped lid-driven chamber was filled with a nanofluid consisting of carbon nanotubes (CNT) dispersed in kerosene oil. A semicircular heater is positioned along the lower wall. The research also incorporates the examination of magnetohydrodynamics and radiation. The use of the Galerkin residual approach inside the finite element method is utilized to derive nonlinear dimensionless governing equations. The phenomenon of Brownian motion in nanoparticles is included into models that describe thermal conductivity and dynamic viscosity. A constant magnetic field with a magnitude of Ha = 10, a constant Reynolds number of Re = 100, and a constant radiation parameter of Rd = 1 were selected for the study. Additionally, a nanofluid concentration of 5 % was chosen. The study aims to investigate the impact of mixed convection by using variable Richardson numbers within the range of 0.1 ≤ Ri ≤ 10. The results are presented in the form of streamlines, isotherms, 2D and 3D charts, illustrating the temporal variations of diverse thermophysical parameters. The investigation reveals that the magnitudes of the drag force and pressure gradient are comparatively greater in the scenario of natural convection. The drag force is 2.8 times greater in the Ri=10 case compared to the Ri=0.1 case. The velocity magnitude is found to be 18 times higher in the Ri= 10 case than in the Ri= 1 case. The Nusselt number has an elevated value as the Richardson number is augmented in conjunction with the dimensionless time (τ).
•Analyzed the effect of the Lewis number in a double-diffusive mixed convective problem.•The square enclosure is considered as room for air ventilation considering an upper channel.•It was observed ...that heat and mass transfer rate increase with the increase of Lewis number.•Average fluid temperature and mass concentration fall with the rise of Lewis number.
Double diffusive flow under mixed convection has become a significant area of research. This study aims to evaluate the Lewis number effect in such a double-diffusive problem in a roof-based air-ventilated system. The Lewis number 0.01 ≤ Le ≤ 5 was chosen for the study, considering other parameters as constant to observe the impact of different heat and mass transfer properties varying the dimensionless time 0.1 ≤ τ ≤ 1. The Galerkin residual technique was chosen to generate the governing equations. The outcomes have been plotted in streamlines, isotherms, isoconcentration, heat and mass transfer, average fluid temperature and mass concentration. The major findings elucidate that heat and mass transfer rate augments when Lewis number goes higher and vice versa. Moreover, when the thermal diffusivity is higher than the mass diffusivity, the average fluid temperature and mass concentration become lower. Overall, this study will be a guide on double-diffusive system design, such as roof-based air ventilation systems.
This numerical study was conducted to investigate the ventilation and airflow in a confined enclosure undergoing rapid inclusion of heat and contaminants representing air quality changes in working ...environments. A flow of air is passing inside a square enclosure with a heat source and a pollutant source on the right and bottom wall, creating double-diffusion, as well as two ventilation ducts on the upper sides asserting mixed convection. The Galerkin weighted residual method is implemented, which is based on the finite element method. For fixed values of Lewis number, Le = 0.5, Richardson number, Ri = 1, Reynolds number, Re = 100, and Prandtl number, Pr = 1.01, simulations were done with Buoyancy Ratio, Br = −10, 1, 10 and 20 over dimensionless time, τ = 0.1, 0.5, and 1.0. The results have been shown with the streamline, isothermal lines, iso-concentration lines, average Nusselt and Sherwood number, average fluid temperature, average mass concentration, and the average temperature at the square cavity's exit port plots. The findings have been discussed to ensure understanding of the changes in parameters, and an enhancement in heat as well as mass transfer was seen with the rapid change in dimensionless time. This specific study could be a guide for designing air conditioning and ventilation systems.
•Analyzed the effect of the Buoyancy Ratio in a double-diffusive mixed convective problem.•The square enclosure is considered as room for air ventilation considering an upper channel.•It was observed that heat and mass transfer rate increase with the increase of Buoyancy Ratio.•Average fluid temperature and mass concentration increase with the rise of Buoyancy Ratio.
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