Manab Kumar Das

Laminar natural convection in an inclined complicated cavity with spatially variable wall temperature

Abstract Natural convection in two-dimensional enclosure with three flat and one wavy walls is numerically investigated. One wall is having a sinusoidal temperature profile. Other three walls including the wavy wall are maintained at constant cold temperature. This problem is solved by SIMPLE algorithm with deferred QUICK scheme in curvilinear co-ordinates. The tests were carried out for different inclination angles, amplitudes and Rayleigh numbers while the Prandtl number was kept constant. The geometrical configurations considered were namely one, two and three undulations. The results obtained show that the angle of inclination affects the flow and heat transfer rate in the cavity. With increase in amplitude, the average Nusselt number on the wavy wall is appreciably high at low Rayleigh number. Increasing the number of undulations beyond two is not beneficial. The trend of local Nusselt number is wavy.

Laminar Mixed Convection in a Parallel Two-Sided Lid-Driven Differentially Heated Square Cavity Filled with a Fluid-Saturated Porous Medium

Two-dimensional, steady, mixed convection flow in an enclosure filled with a Darcian fluid-saturated uniform porous medium is considered. Both the left wall and the right wall are moving upwards with same velocity. They are maintained at cold and hot constant temperatures respectively. The top and the bottom walls are fixed and are thermally insulated. The governing equations are normalized and solved numerically with boundary conditions by finite volume approach using third order accurate upwinding scheme (deferred QUICK). To validate the code, comparisons are made with previously published work and are found to be in excellent agreement. The study is conducted by varying the key parameters i.e., Richardson number (Ri = Gr/Re 2), Darcy number (Da = κ/H 2) and Grashof number (Gr = g β H 3ΔT/ν 2) and fixing Prandtl number (Pr = 0.71). A parametric study is conducted and a set of streamline and isotherm plots are presented. The average Nusselt number reaches a value of 1 asymptotically when the Ri is gradually increased for Gr up to 103. For Gr = 104, the asymptotic value is 1.5. An empirical heat transfer correlation is also presented.

Natural convection in a cavity with a wavy wall heated from below and uniformly cooled from the top and both sides

In this paper, natural convection inside a two-dimensional cavity with a wavy right vertical wall has been carried out. The bottom wall is heated by a spatially varying temperature and other three walls are kept at constant lower temperature. The integral forms of the governing equations are solved numerically using finite-volume method in the non-orthogonal body-fitted coordinate system. The semi-implicit method for pressure linked equation algorithm with higher-order upwinding scheme are used. The streamlines and isothermal lines are presented for three different undulations (1, 2 and 3) with different Rayleigh number and a fluid having Prandtl number 0.71. Results are presented in the form of local and average Nusselt number distribution for a selected range of Rayleigh number (10 0 -10 6 ).

Natural convection heat transfer augmentation in a partially heated and partially cooled square cavity utilizing nanofluids

Purpose – The purpose of this paper is to investigate the behaviour of nanofluids numerically inside a partially heated and partially cooled square cavity to gain insight into heat transfer and flow processes induced by a nanofluid.Design/methodology/approach – A model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLEC algorithm.Findings – Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. Five different relative positions of the active zones are considered.While circulation depend strongly on the total exit length. Governing parameters were 103 < Gr < 107 but due to space constraints the results for 104 < Gr <107 are presented. It is found that both the Grashof number and solid volume fraction χ affect the fluid flow and heat transfer in the cavity. CopperWater nanofluid is used with Pr = 6.2 ...

Natural Convection in a Rectangular Cavity Heated from Below and Uniformly Cooled from the Top and Both Sides

ABSTRACT In this article, a study of natural convection inside a rectangular cavity is carried out. The bottom wall is heated by a spatially varying temperature and other three walls are kept constant at lower temperature. The integral forms of the governing equations are solved numerically using the finite-volume method in a nonorthogonal body-fitted coordinate system. The SIMPLE algorithm with higher-order upwinding scheme is used. Results are presented in the form of local and average Nusselt number distribution for a range of Rayleigh numbers (100–106) and aspect ratios (0.5, 0.75, 1, 1.25, 1.5, and 2). The streamlines and isothermal lines are presented for various Rayleigh numbers and a fluid having Prandtl number 0.71.

CONJUGATE HEAT TRANSFER STUDY OF TWO-DIMENSIONAL LAMINAR INCOMPRESSIBLE OFFSET JET FLOWS

ABSTRACT Steady-state conjugate heat transfer study of a slab and fluid is carried out for a two-dimensional laminar incompressible offset jet. The unsteady stream function–vorticity formulation is used to solve the governing equations. The energy equation in the fluid and the conduction equation in the solid are solved simultaneously. The conjugate heat transfer characteristics are studied with four parameters, Re, Pr, S/h, and k. The fluid properties affect the heat transfer in the solid slab. The conjugate interface temperature is decreased up to the recirculation region and further increased to a developed condition. As the k is increased, its effect on Nu is reduced. Variation of local Nusselt number and average Nu are reported in detail.

Heat Transfer Study of Two-Dimensional Laminar Incompressible Wall Jet over Backward-Facing Step

A steady-state heat transfer study is carried out for a two-dimensional, laminar, incompressible, plane wall jet over a backward-facing step. An unsteady stream function–vorticity formulation is used to solve the governing equations. The heat transfer characteristics of the jet as functions of Reynolds number (Re), Prandtl number (Pr), and step geometry (step length l and step height s) are reported in detail. Results are presented in the form of isotherm, Nusselt number, and average Nusselt number. In some cases, the computed results are compared with the results when the step length is zero.

Computation of Mean Flow and Thermal Characteristics of Incompressible Turbulent Offset Jet Flows

Two-dimensional, steady, incompressible, forced convection turbulent flow at high Reynolds number is considered. Mean velocity and thermal characteristics are presented for the wall and offset jet flows. The standard k–ϵ model is used. Finite volume-based SIMPLE algorithm is followed and the powerlaw scheme is used for the convective terms. The developed code is tested for offset flow and compared with the experimental results. Computational details of various mean flow and turbulent parameters (k, ϵ, ν t) are presented and explained for different offset ratios (OR).

Application of an ADI scheme for steady and periodic solutions in a lid‐driven cavity problem

Purpose – The purpose of the paper is to study the steady and periodic solution of a lid‐driven cavity flow problem with the gradual increase of Reynolds number (Re) up to 10,000.Design/methodology/approach – The problem is solved by unsteady stream function‐vorticity formulation using the clustered grids. The alternating direction implicit (ADI) method and the central difference scheme have been used for discretization of the governing equations. Total vorticity error and the total kinetic energy have been considered for ensuring the state of flow condition. The midplane velocity distribution and the top wall vortex distribution are compared with the results of other authors and found to show good agreement.Findings – Kinetic energy variation with time is studied for large time computation. Below 7,500, it becomes constant signifying the flow to be in steady‐state. At Re=10,000, the fluid flow has an oscillating nature. The dimensionless period of oscillation is found to be 1.63. It is demonstrated that ...

Experimental validation of a quasi three-dimensional conjugate heat transfer model for the metering section of a single-screw plasticating extruder

Abstract This paper presents a quasi three-dimensional computer model and its validation with experimental results of the thermal transport processes in the metering section of a single-screw plasticating extruder. A finite volume based approach (SIMPLEC) has been used to obtain flow, thermal and pressure fields of a power-law fluid in the screw channel. The accuracy of the present model has been confirmed by the satisfactory tally of the numerical results with the experimental data for the extruder with fully open exit valve, and also by the excellent matching of the dimensionless exit pressure gradient with the experimental data.