A Generalized Magneto-Thermoviscoelastic Problem of a Single-Layer Plate for Vibration Control Considering Memory-Dependent Heat Transfer and Nonlocal Effect

Viscoelastic materials are a kind of representative passive vibration control materials with many applications in civil engineering for earthquake mitigation in building structures, and these materials often serve in a thermo-elastic coupling environment. In this work, a one-dimensional magneto-thermoviscoelastic problem of a single-layer viscoelastic plate is investigated with memory-dependent derivative and nonlocal effect in the context of generalized thermo-elasticity. The plate is placed in a magnetic field, and the upper surface is subjected to a thermal shock. The governing equations for the single-layer plate are formulated considering the time delay and the kernel function of the memory-dependent derivative, nonlocal effect, temperature-dependent properties, and magnetic field. The Laplace transform and its numerical inversion are employed to solve this problem. The nondimensional temperature, displacement, and stress are calculated and presented graphically. Based on the numerical results, the influence of time delay and kernel function of the memory-dependent derivative, nonlocal effect parameters, temperature-dependent properties, and magnetic field parameters on the distributions of the nondimensional temperature, displacement, and stress are discussed.

Effect of Variable Properties and Moving Heat Source on Magnetothermoelastic Problem under Fractional Order Thermoelasticity

A one-dimensional generalized magnetothermoelastic problem of a thermoelastic rod with finite length is investigated in the context of the fractional order thermoelasticity. The rod with variable properties, which are temperature-dependent, is fixed at both ends and placed in an initial magnetic field, and the rod is subjected to a moving heat source along the axial direction. The governing equations of the problem in the fractional order thermoelasticity are formulated and solved by means of Laplace transform in tandem with its numerical inversion. The distributions of the nondimensional temperature, displacement, and stress in the rod are obtained and illustrated graphically. The effects of the temperature-dependent properties, the velocity of the moving heat source, the fractional order parameter, and so forth on the considered variables are concerned and discussed in detail, and the results show that they significantly influence the variations of the considered variables.

A Two-Dimensional Generalized Electromagnetothermoelastic Diffusion Problem for a Rotating Half-Space

In the context of the theory of generalized thermoelastic diffusion, a two-dimensional generalized electromagnetothermoelastic problem with diffusion for a rotating half-space is investigated. The rotating half-space is placed in an external magnetic field with constant intensity and its bounding surface is subjected to a thermal shock and a chemical potential shock. The problem is formulated based on finite element method and the derived finite element equations are solved directly in time domain. The nondimensional temperature, displacement, stress, chemical potential, concentration, and induced magnetic field are obtained and illustrated graphically. The results show that all the considered variables have a nonzero value only in a bounded region and vanish identically outside this region, which fully demonstrates the nature of the finite speeds of thermoelastic wave and diffusive wave.

Thermohydraulic Analysis of Shell-and-Tube Heat Exchanger with Segmental Baffles

In this study, the experimental analysis was performed on the shell-and-tube type heat exchanger containing segmental baffles at different orientations. In the current work, three angular orientations (θ) 0°, 30°, and 60° of the baffles were analyzed for laminar flow having the Reynolds number range 303–1516. It was observed that, with increase of Reynolds number from 303 to 1516, there was a 94.8% increase in Nusselt number and 282.9% increase in pressure drop. Due to increase of Reynolds number from 303 to 1516, there is a decrease in nondimensional temperature factor for cold water (ω) by 57.7% and hot water (ξ) by 57.1%, respectively.

COMBINED NATURAL CONVECTION COOLING OF A DRINK CAN

We investigate natural convection cooling of the fluid in a drink can placed in a refrigerator by simulating the full combined boundary layer system on the can wall. The cylindrical can is filled with water at initial nondimensional temperature 0, and located within a larger cylindrical container filled with air at initial temperature −1. The outer container walls are maintained at constant temperature −1. Initially both fluids are at rest. Two configurations are examined: the first has the inner can placed vertically in the middle of the outer container with no contact with the outer container walls, and the second has the inner can placed vertically at the bottom of the outer container. The results are compared to those obtained by assuming that the inner can walls are maintained at a constant temperature, showing similar basic flow features and scaling relations, but with very different proportionality constants.

Rewetting Analysis of Hot Vertical Surfaces With Precursory Cooling by the Heat Balance Integral Method

The effect of precursory cooling on conduction-controlled rewetting of both slab and solid cylinder is analyzed by the heat balance integral method. A constant heat transfer coefficient is assumed in the wet region behind the wet front, while an exponentially decaying heat flux is assumed in the dry region ahead of the wet front. The physical problem is characterized by two dimensionless constants describing the extent of precursory cooling and three dimensionless numbers, namely, Peclet number, Biot number, and the nondimensional temperature. Results of the present solution are found to be in good agreement with other analytical solutions obtained through the Weiner–Hopf technique and the separation of variables as well as with the published experimental data for different coolants over a varied range of coolant flow rate. It is seen that precursory cooling increases the rewetting velocity particularly at higher flow rates. If it is neglected, the model grossly underpredicts the quench velocities.

Flow in a “Cover-Plate” Preswirl Rotor–Stator System

This paper describes a combined theoretical, computational, and experimental study of the flow in an adiabatic preswirl rotor–stator system. Preswirl cooling air, supplied through nozzles in the stator, flows radially outward, in the rotating cavity between the rotating disk and a cover-plate attached to it, leaving the system through blade-cooling holes in the disk. An axisymmetric elliptic solver, incorporating the Launder–Sharma low-Reynolds-number k–ε turbulence model, is used to compute the flow. An LDA system is used to measure the tangential component of velocity, Vφ, in the rotating cavity of a purpose-built rotating-disc rig. For rotational Reynolds numbers up to 1.2 × 106 and preswirl ratios up to 2.5, agreement between the computed and measured values of Vφ is mainly very good, and the results confirm that free-vortex flow occurs in most of the rotating cavity. Computed values of the preswirl effectiveness (or the nondimensional temperature difference between the preswirl and blade-cooling air) agree closely with theoretical values obtained from a thermodynamic analysis of an adiabatic system.

Flow in a “Cover-Plate” Pre-Swirl Rotor-Stator System

This paper describes a combined theoretical, computational and experimental study of the flow in an adiabatic pre-swirl rotor-stator system. Pre-swirl cooling air, supplied through nozzles in the stator, flows radially outward, in the rotating cavity between the rotating disc and a cover-plate attached to it, leaving the system through blade-cooling holes in the disc. An axisymmetric elliptic solver, incorporating the Launder-Sharma low-Reynolds-number k-ε turbulence model, is used to compute the flow. An LDA system is used to measure the tangential component of velocity, Vϕ, in the rotating cavity of a purpose-built rotating-disc rig. For rotational Reynolds numbers up to 1.2 × 106 and pre-swirl ratios up to 2.5, agreement between the computed and measured values of Vϕ is mainly very good, and the results confirm that free-vortex flow occurs throughout most of the rotating cavity. Computed values of the pre-swirl effectiveness (or the nondimensional temperature difference between the pre-swirl and blade-cooling air) agree closely with theoretical values obtained from a thermodynamic analysis of an adiabatic system.