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Introducing flow pulsation into a water-jet cooling system allows for flow-field control for more efficient heat removal. Here, transient thermal mapping is used to quantify how a pulsed water jet in a falling-film geometry can enhance the overall cooling performance. It is found that the influence of the jet-pulsation frequency on the maximum cooling performance can be predicted by heat flux matching at the solid-liquid interface, while the optimum pulsation frequency is dictated by the thermofluid instabilities that occur in the falling film.

During air or liquid cooling, thermal resistance of the devices is measured precisely from the thermal information at the junction. But existing thermal measurement technologies fall short because of highly transient events such as unstable vortex formation (air cooling) and bubble growth (two-phase liquid cooling). In solving this problem, this paper reports a novel and low-cost thermal mapping technique that can capture highly spatio-temporal temperature evolution at the solid-liquid interface. Essentially, a robust interface is fabricated with CuInS 2 /ZnS Quantum dots (λ peak = 550 nm and 750 nm) trapped inside nanopores (20 nm-30 nm) of a ceramic membrane (50 µm) and/or everyday use paper. It is observed that such nanoconfinement assisted Quantum dots provided sustained thermal photoluminescence coefficient (-0.1 nm/°C) at high number of heating-cooling cycle. This unique yet low cost thermal mapping technique is applied to capture thermal evolution during micro-droplet impingement cooling and hemiwicking flows through anisotropic wicks which showcase commendable spatio-temporal benefits.

Purpose The purpose of this investigation is to determine the nature of the flow field, temperature distribution and heat and mass transfer in a triangular solar collector enclosure with a corrugated bottom wall in the unsteady condition numerically. Design/methodology/approach Non-linear governing partial differential equations (i.e. mass, momentum, energy and concentration equations) are transformed into a system of integral equations by applying the Galerkin weighted residual method. The integration involved in each of these terms is performed using Gauss’ quadrature method. The resulting non-linear algebraic equations are modified by the imposition of boundary conditions. Finally, Newton’s method is used to modify non-linear equations into the linear algebraic equations. Findings Both the buoyancy ratio and thermal Rayleigh number play an important role in controlling the mode of heat transfer and mass transfer. Originality/value Calculations are performed for various thermal Rayleigh numbers, buoyancy ratios and time periods. For each specific condition, streamline contours, isotherm contours and iso-concentration contours are obtained, and the variation in the overall Nusselt and Sherwood numbers is identified for different parameter combinations.

A lid-driven L -shaped cavity filled with a porous medium is analyzed. The Galerkin weighted residual method is applied to obtain numerical solutions. The effect of the Reynolds number ( Re = 1–100), Grashof number ( Gr = 10 3 –10 5 ) and Darcy number ( Da = 10 −5 –10 −3 ) on the velocity and temperature fields is examined. For the vertical wall, a higher heat transfer rate is observed when a low Grashof number, higher Darcy number and higher Reynolds number are applied, but the opposite characteristic is found in the horizontal wall. It is evident that heat transfer decreases up to 63% in the horizontal wall when the flow has a high Reynolds number ( Re = 100).

In this study magneto-hydrodynamic convection in a half-moon shaped cavity filled with ferrofluid has been analyzed numerically. The cavity has two semi-circular bottom heaters and effect of the distance between these two heaters ( λ = 0.1 , 0.4 ) has been thoroughly investigated. Numerical simulation has been carried out for a wide range of Rayleigh number ( Ra = 10 3 ∼ 10 7 ), Hartmann number ( Ha = 0 ∼ 100 ) and inclination angle of magnetic field ( γ = 0 ° ∼ 90 ° ) to understand the flow field, thermal field and entropy generation respectively. Cobalt-kerosene and Fe 3 O 4 -water ferrofluids are used for the present investigation and considered as a single phase fluid. Galerkin weighted residual method of finite element analysis has been used for numerical solution. The code validation and grid independency test have been carried out to justify the numerical accuracy. It has been observed that increment of magnetic field reduces the heat transfer rate, whereas increment of heater distance augments the heat transfer rate significantly. Results are discussed on the basis of Nusselt number ( Nu ), Bejan number ( Be ) and shown by contours and 3D plots. It has also been found that λ = 0.4 always shows better heat transfer rate and entropy optimization.

A numerical analysis has been investigated for unsteady natural convection heat transfer problem in diamond shaped cavity. Carbon nanotube (CNT)-water nanofluid is used to analyze the heat transfer and compared with the pure water as working fluid. The lower right wall is kept at heated surface with constant heat flux and upper left wall is kept cold. Both the bottom left and upper right wall are kept adiabatic. The considered physical problem is characterized mathematically by a set of governing equations along with the corresponding boundary conditions. Galerkin weighted residual method of finite element analysis is used to solve the governing equations. Calculations are done for pertinent parameters such as the solid volume fraction (ϕ = 0.0–0.12) and Rayleigh number (Ra = 104–108) at dimensionless times (τ = 0.01 and 1.0) and fixed Pr = 6.2. Obtained results are presented in terms of average Nusselt number and maximum fluid temperature, streamlines and isotherms in graphs, charts and related contours. It has been observed that increase of Rayleigh number and solid volume fraction enhance the heat transfer rate and reduce the maximum fluid temperature. In this investigation the highest amount of overall heat transfer reaches up to 115%.

Numerical analysis of magneto-hydrodynamic flow has been a matter of concern for research engineers and scientists. In this paper, magneto-hydrodynamic convection in square tank occupied with Cu-H 2 O nanomaterial is investigated for different configurations of heater-sink, in which Artificial Neural Network (ANN) model was used as an advanced predictive tool. The active semi-circular thermal location (heater and sink) at the left- right vertical sides are kept constantly at high and low temperatures respectively, whereas other walls are kept adiabatic. To reach the solution, Galerkin residual finite element analysis has been implemented. The investigation has been done for Hartmann number (Ha = 0 – 100), Rayleigh number (Ra = 103-107) and nanomaterial concentration ( φ = 0 – 0.05) and finally, streamlines, isotherm contours and entropy generation contours are discussed thoroughly. The overall heat transfer and generation entropy are quantitatively investigated by overall Nusselt number (Nu) and Bejan number (Be), respectively. Existence of external Lorentz forces affects on both non-dimensional performance parameters, Nu and Be. Finally, the higher heat transfer is found for middle–middle configuration of heater-sink walls. The impact of Ha and φ on Nu and Be found from the numerical heat transfer analysis has been predicted and compared with ANN prediction model. To be noted, ANN is widely used technique to compare and predict different experimental and numerical data accurately in many engineering applications.

Magneto-hydrodynamic convection has been gaining attention due to its wide range of application. In this paper magneto-hydrodynamic convection in a half-moon (semi-circular) shaped cavity has been analysed. The cavity has two semi-circular bottom heaters and effect of distance between this two heaters has been thoroughly investigated for two different cases ( λ = 0.1, 0.4). Numerical simulation has been carried out for a wide range of Rayleigh number ( Ra = 10 3 ∼ 10 7 ) and for Hartmann number ( Ha = 0 ∼ 100) to understand the flow and thermal field. Galerkin weighted residual method of finite element analysis has been adopted for numerical solution along with code validation and grid independency test to ensure the numerical accuracy. It has been found that strengthening of magnetic field tries to reduce the heat transfer rate, whereas increment of heater distance augments the heat transfer rate. Results analysed on the basis of Nusselt number and average fluid temperatures are shown by related contours, plots and graphical analysis. Therefore, higher heat transfer rate has been achieved for λ = 0.4.

In this study, magneto-hydrodynamic (MHD) mixed convection flow through a channel with a round cavity at bottom wall using non-Newtonian power law fluid is analysed numerically. The cavity is kept at uniformly high temperature whereas rest of the bottom wall is insulated and top wall of the channel is maintained at a temperature lower than cavity temperature. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method is appointed to solve the continuity, momentum and energy equations. The problem is solved for wide range of pertinent parameters like Rayleigh number (Ra= 103 – 105), Hartmann number (Ha= 0 - 60) and power law index (n= 0.5 – 1.5) at constant Richardson number Ri= 1.0. The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study is illustrated by average Nusselt number plots. Result of this investigation indicates that heat transfer is highest for dilatant fluids at this configuration and they perform better (47% more heat transfer) in absence of magnetic field. The retardation of heat transfer is offset by shear thickening nature of non-Newtonian fluid.In this study, magneto-hydrodynamic (MHD) mixed convection flow through a channel with a round cavity at bottom wall using non-Newtonian power law fluid is analysed numerically. The cavity is kept at uniformly high temperature whereas rest of the bottom wall is insulated and top wall of the channel is maintained at a temperature lower than cavity temperature. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method is appointed to solve the continuity, momentum and energy equations. The problem is solved for wide range of pertinent parameters like Rayleigh number (Ra= 103 – 105), Hartmann number (Ha= 0 - 60) and power law index (n= 0.5 – 1.5) at constant Richardson number Ri= 1.0. The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study is illustrated by average Nusselt number plots. Result of thi...

This paper demonstrates magneto-hydrodynamic (MHD) mixed convection flow through a channel with a rectangular obstacle at the entrance region using non-Newtonian power law fluid. The obstacle is kept at uniformly high temperature whereas the inlet and top wall of the channel are maintained at a temperature lower than obstacle temperature. Poiseuille flow is implemented as the inlet velocity boundary condition. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method has been appointed to solve the continuity, momentum and energy equations. The problem has been solved for wide range of pertinent parameters like Richardson number (Ri = 0.1 - 10) at a constant Reynolds number (Re = 100), Hartmann number (Ha = 0 - 100), power index (n = 0.6 - 1.6). The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given st...

Mixed convection in a lid-driven square enclosure with a rotating cylinder inside has been analyzed using non-Newtonian ferrofluid (Fe3O4-water). Left vertical wall is heated while the right vertical wall is kept cold. Bottom wall and cylinder surface are assumed to be adiabatic. Top wall has a moving lid with a constant velocity U0. Galerkin method of finite element analysis has been used to solve the governing equations. Numerical accuracy of solution is ensured by the grid independency test. A variety of Richardson number (Ri = 0.1 - 10) at a governing Reynolds number (Re = 100), power law index (n = 0.5 - 1.5), rotational speed (Ω = 0 - 15) and solid volume fraction of ferrous particles (φ = 0 - 0.05) are employed for this present problem. To illustrate flow and thermal field, streamline and isotherms are included. Average Nusselt number plots are shown to show overall heat transfer rate. It is observed that better heat transfer is achieved at higher rotational speed (Ω), Richardson number (Ri) and po...

Mixed convection in a lid-driven enclosure with a curved bottom wall has been investigated using CNT (Carbon Nanotube)-water nanofluid in this paper. The curvature of the bottom wall follows the sine function. Studies have been made with different amplitudes (λ = 0.05, 0.1, 0.15) of the sine function hence wall curvature. The curved wall at the bottom is heated and the top wall is kept at a relatively low temperature. Left vertical and right vertical surface are assumed to be adiabatic. Top wall has been moving at a constant lid velocity U0 at right direction. Galerkin method of FEA (Finite Element Analysis) has been used to solve the governing equations. Different parameters like Richardson number (Ri = 0.1 ∼ 10) at a fixed Reynolds number (Re = 100), solid volume fraction of CNT particle (φ = 0 ∼ 0.09) are used to observe better heat transfer rate. Streamlines, isothermal lines and average Nusselt number plots are included to discuss the result of the investigation. A 2D plot between average Nusselt num...