Impact of nonlinear thermal radiation on nonlinear mixed convection flow near a vertical porous plate with convective boundary condition

This study presents similarity solution for boundary layer flow near a vertical porous plate with combined effects of nonlinear density variation with temperature and nonlinear thermal radiation. To accurately predict the flow phenomenon near the porous plate, the convective boundary condition is considered at the plate surface. The two-dimensional partial differential equations are transformed to ordinary differential equations through the similarity transformation. The resulting ordinary differential equations are solved numerically in Maple software using the Runge–Kutta–Ferhlberg fourth-fifth order (RKF45) algorithm. The influence of the inherit parameters like the nonlinear thermal radiation parameter, suction/injection parameter, nonlinear Boussinesq approximation parameters, local convective heat transfer parameter, local Grashof number, and Prandtl number governing the fluid behaviour is discussed. We found that the rate of heat transfer improves with the injection and nonlinear thermal radiation parameter whereas decreases with suction, local convective heat transfer parameter and local Grashof number when air and mercury are used as the working fluids. Furthermore, with the growth in the values of local Grashof number, convective heat transfer parameter and nonlinear thermal radiation parameter and in the presence of suction/injection, the porous plate surface friction witnessed an observable growth. Suction growth plays a supportive role on the velocity curve near the porous plate but a contrary trend is seen in the free stream. The temperature distribution also decays with suction augment. Injection growth is inversely proportional to the velocity profile near the porous plate but we recorded the opposite phenomenon in the free stream.

Entropy generation analysis for peristalsis of magneto Jeffrey materials

This article communicates peristalsis of Jeffrey material in curved geometry. Here, material has temperature-dependent thermal conductivity and viscosity. Mathematical modeling of an inclined magnetic field in curved configuration has been presented in this article. Irreversibility effects have been analyzed through entropy generation. Slip conditions are entertained both for velocity and thermal fields. Problem is first reduced in wave frame and then lubrication approach has been utilized. Numerical solution of dimensionless problem is obtained and important parameters of curiosity are examined. It is noticed that velocity enhances for higher viscosity whereas temperature decreases for higher thermal conductivity coefficient. Velocity of the flow is maximum for inclination of magnetic field to be zero and it is minimum for [Formula: see text] Heat transfer parameter enhances both for thermal conductivity parameter and Hartmann number. Temperature is high for curved configuration when compared with straight channel. It is observed that entropy remains unchanged in center of the channel and it is maximum near the channel walls. Entropy generation decays near the channel walls by higher viscosity and thermal conductivity parameters. However, entropy is more for higher inclination of magnetic field.

Molded Vial Manufacturing and Its Impact on Heat Transfer during Freeze-Drying: Vial Geometry Considerations

Recent advances in molded vial manufacturing enabled manufacturers to use a new manufacturing technique to achieve superior homogeneity of the vial wall thickness. This study evaluated the influence of the different manufacturing techniques of molded vials and glass compositions on vial heat transfer in freeze-drying. Additionally, the influence of using empty vials as thermal shielding on thermal characteristics of edge and center vials was investigated. The vial heat transfer coefficient Kv was determined gravimetrically for multiple vial systems. The results showed superior heat transfer characteristics of the novel manufacturing technique as well as differences in heat transfer for the different glass compositions. Empty vials on the outside of the array did not influence center vial Kv values compared to a full array. The direct contact area and vial bottom curvature and their correlation to heat transfer parameters were analyzed across multiple vial systems. A new approach based on light microscopy to describe the vial bottom curvature more accurately was described. The presented results for the contact area allowed for an approximation of the pressure-independent heat transfer parameter KC. The results for the vial bottom curvature showed a great correlation to the pressure-dependent heat transfer parameter KD. Overall, the results highlighted how a thorough geometrical characterization of vials with known heat transfer characteristics could be used to predict thermal characteristics of new vial systems as an alternative to a time-consuming gravimetric Kv determination. Primary drying times were simulated to show the influence of Kv on drying performance.

Correcting the infrared images of soft biological tissues

Non-invasive (remote) thermographic methods based on IR images are being actively implemented. Using the calculation results of the temperature increment that occurs when a pathological source exists in the person’s skin, a number of ways of solving “inverse problems” are proposed. These include the determination of the depth of the thermal source by measuring the mono or polychrome increment of the normalized brightness of the tissue surface at one point; the source depth and heat transfer parameter by measuring the poly or monochrome one of the normalized brightness (or temperature) at two points; the thermal power of the source by measuring the increment of absolute brightness or temperature at one point; the depth of the thermal source and its size in the near-surface layer by measuring the increment of the normalized brightness at two points. In order to solve these problems, the thermophysical and optical properties of the soft tissues of the biological organism are indicated. Analytical solutions are given for describing the temperature and the glow that arises under its influence from the sources of cylindrical and spherical shape.

Asymptotic Analysis of the Maxwell Garnett Formula Using the Two-Phase Composite Model

In this paper, a two-phase computational model of a composite (TwPM) with cylindrical inclusion of square cross-sections and small sizes is proposed. The applied asymptotic techniques devoted to the analysis of the constructed TwPM are validated through a comparison of the results reported by others. A simple analytical formula of the reduced heat transfer parameter for small size of inclusions is derived, and an asymptotic character of Maxwell Garnett (MG) formula is illustrated.

Constructal Design of Convective Y-Shaped Cavities by Means of Genetic Algorithm

In the present work constructal design is employed to optimize the geometry of a convective, Y-shaped cavity that intrudes into a solid conducting wall. The main purpose is to investigate the influence of the dimensionless heat transfer parameter a over the optimal geometries of the cavity, i.e., the ones that minimize the maximum excess of temperature (or reduce the thermal resistance of the solid domain). The search for the best geometry has been performed with the help of a genetic algorithm (GA). For square solids (H/L = 1.0) the results obtained with an exhaustive search (which is based on solution of all possible geometries) were adopted to validate the GA method, while for H/L ≠ 1.0 GA is used to find the best geometry for all degrees of freedom investigated here: H/L, t1/t0, L1/L0, and α (four times optimized). The results demonstrate that there is no universal optimal shape that minimizes the thermal field for all values of a investigated. Moreover, the temperature distribution along the solid domain becomes more homogeneous with an increase of a, until a limit where the configuration of “optimal distribution of imperfections” is achieved and the shape tends to remain fixed. Finally, it has been highlighted that the GA method proved to be very effective in the search for the best shapes with the number of required simulations much lower (8 times for the most difficult situation) than that necessary for exhaustive search.

Windows in Buildings - Diagnostics of Selected Properties after Time of Using

In construction projects in a field of residential buildings installation and replacement of fillings of openings (windows) play a very important role. A number of requirements is put on newly built windows, in particular in the field of thermal insulation and airtightness. Will the window elements stand the test even after years of use? The aim of this paper is to compare the declared parameter of heat transfer parameter of glazing Ug [W.m-2.K-1] of insulating glasses found from the print on a between the glass frame with the value which can be determined by measuring directly on the building after a certain period of use.

Investigation and Comparison of Heat Transfers Analysis Used in Commercial FEM for Metal Forming

During an Aluminium extrusion process, the extrusion parameters, i.e. friction, heat transfer, etc. are significantly influence by the temperature gradients produced in the billet during transfer to the container and after upsetting the container. The heat transfer at the tool/billet interface governs the temperature profile throughout the billet and tools during extrusion and consequently has a critical influence on the results. Although FEM technique offers great potential, care must be taken when applying the analysis to the hot extrusion of rate sensitive alloys. The most useful approach of an FEM simulation would thus be to include both the tooling and the billet in the calculation as discretised meshes. Because of the occurrence of the conductive and convective heat transfer, the deformation during hot extrusion is not adiabatic and estimation of the temperature increase is alloy dependent. The aim of this paper is to investigate and to compare how commercial FEM codes assign and deal with the heat transfer parameter at the tool/material interface. Three commercial FEM codes were investigated and compared; Simufact, Deform and Forge. The usefulness and limitation when using commercial FEM codes are discussed. Methods to assess difficulty of comparison are presented. The work illustrates the essentials of numerical analysis in the comprehension of the thermo-mechanical events occurring during large deformation. Results are presented for velocity distribution and temperature evolution in both materials and tools. It is shown that the heat transfer parameter to be extremely sensitive when attempting to simulate the hot deformation. Moreover, the accuracy of the results does not only depended on the geometric definition of the tooling and material data but also the governing boundary conditions between the material and tooling.