Effects Of Thermophysical Parameters Research Articles

Conjugate heat transfer and flow around tandem tubes: Effect of thermophysical parameters and tube arrangement

Thermodynamic calculation and geometry parameters are key issues in thermo-equipment design. The flow and conjugate heat transfer around the tandem tubes are numerically investigated, in which the examined parameters include thermal conductivity ratio (kr), volumetric heat capacity ratio (φr), and Biot number (Bi) which are varied from 200 to 800, 1000 to 3000, and 0.1 to 1.0, respectively. Further, the effect of the space ratio (L/D = 1.0–10.0) between the tandem tubes on the flow pattern and heat transfer is also studied to obtain a proper tube arrangement. In particular, a difference method for lattice Boltzmann algorithm is validated and then adopted on the curve fluid-solid interface to calculate the conjugate heat transfer. Results demonstrate that the thermal conductivity ratio significantly affects the heat transfer performance of the tube while the volumetric heat capacity ratio only affects the rate of heating process. The growth in thermal conductivity ratio leads to a more uniform temperature distribution and higher thermal performance, and this effect becomes weaker as the kr grows. Meanwhile, the increase of Bi strengthens the convective heat transfer inside the tube, further changing the dominant way of heat transfer. Finally, the flow varies considerably with the space ratio, classifying into four typical regimes. It is found that the Nu is sensitive to the flow regime and the case with L/D = 4.0 provides the best thermal performance of tandem tubes. These results can provide more realistic predictions and indications in thermo-equipment design.

Impact of magnetic-field on the dynamic of gas bubbles in N-dimensions of non-Newtonian hybrid nanofluid: analytical study

The aim of this study is to focus mainly on the behavior of gas bubble growth under the effect of a magnetic field in -dimensions of non-Newtonian hybrid nanomaterials. Many types of nanoparticles with base nanofluids have been used to study the problems that arise in the nanotechnology industrial processes. Considering these problems in nanomaterials, the effects of thermophysical parameters, such as nanoparticle size and type, nanoparticle volume fraction, -dimensions, thermal diffusivity, and thermal conductivity are discussed. This investigation has demonstrated that the magnetic field and electrical conductivity have a significant impact on the dynamics of gas bubbles, showing that they play an important role in decreasing the growth processes. Furthermore, we examine the behavior of the gas bubble radius in the cases of pure water, mono nanoparticles, and hybrid nanofluid of nanomaterials (such as and ) in N-dimensions of non-Newtonian fluid. Moreover, the relationship between shear stress and shear rate of non-Newtonian hybrid nanofluids is studied. The results are graphically represented to illustrate the behavior of solutions for the presented model. It is noted that the nanoparticles improve the thermophysical properties, which enhances the efficiency of the heat transfer rate of the nanofluids and decreases the behavior of the gas bubble radius. Based on the analysis of simulation procedures and system stability, we observe that the obtained results provide more accurate solutions and a greater reduction in the growth bubble process compared to previous models. Finally, we apply the phase plane approach to analyze the stability of the corresponding nonlinear system of the proposed model.

Effect of thermo-physical parameters on heat transfer characteristics of the wall implanted with heat pipes

• A new evaluate index (ITRR) is proposed to reflect the thermal response. • The actual environmental of WIHP dynamic experiment system is tested and validation. • The influence of thermal conductivity on the heat transfer of WIHP is analyzed. • The influence of density on the heat transfer of WIHP is analyzed. • The influence of specific heat capacity on the heat transfer of WIHP is analyzed. The heat transfer characteristics of a wall implanted with heat pipes (WIHP), a new passive natural energy utilization technology, significantly differ from that of an ordinary wall. It features effective heat transfer between indoor and outdoor environments due to the pipe’s unidirectional thermal conductivity. The thermal performance of the wall is crucial in terms of reducing a building’s energy consumption. In this paper, the experiment and theoretical analysis were combined, and the numerical simulation calculation was used to analyze the effects of material thermo-physical parameters on WIHP heat transfer performance. The results show that for the inside surface temperature, density and specific heat capacity are negatively related to it, and thermal conductivity is also negatively related to it before the heat pipe is in optimum working condition, and then the thermal conductivity is positively related to it. For the inside surface heat flux, it is opposite to the variation of inside surface temperature. The inside surface temperature rise rate (ITRR) is proposed to reflect the thermal response of the inside surface temperature to the variation of outdoor air temperature. When the thermal conductivity increases, the difference between the maximum and minimum ITRR is 0.053 °C/h. When the density increases, the trend of ITRR decreases first and then increases, and the average value is 0.062 °C/h. When the specific heat capacity gradually increases, the difference between the maximum and minimum of ITRR is 0.006 °C/h.

Investigation of the transient heat transfer to a supersonic air jet impinging on a high-temperature plate based on a discrimination-experiment method.

A discrimination-experiment method is developed to investigate the transient heat transfer of air jet impingement by discretizing the solid domain into mutually adiabatic test cylinders. This method can not only reduce the influence of the transverse heat transfer of a solid domain on the heat transfer characteristics of the jet but can also simplify the two-dimensional or three-dimensional heat conduction problem into a one-dimensional problem. Moreover, the discrimination-experiment method eliminates the embedment of thermocouples into the solid domains, further improving the accuracy and reliability of the proposed method. The transient heat transfer characteristics of a supersonic air jet impinging on a high-temperature target (860°C) and the effects of thermo physical parameters, such as the density, specific heat capacity, thermal conductivity and nozzle-to-target distance (H/D = 3, 4, and 5) are analyzed in detail using the discrimination-experiment method. The results provide important guidance for the thermal design of supersonic air jet impingement.

Natural convection and entropy generation of a nanoliquid in a crown wavy cavity: Effect of thermo-physical parameters and cavity shape

Natural convection (NC) of nanoliquids specifically in enclosures is of use in diverse fields such as solar collectors, HVAC, and medical treatment. Recent research shows that suspension of nano-materials within the base fluid enhanced the heat transfer performance. NC heat transfer of Al2O3–H2O nanoliquid within a crown cavity with a circular cylinder inside it is studied in this paper. The flow is considered buoyancy-driven which is under thermal radiation (Rd) and constant magnetic field within the porous media. Dimensionless modes of Navier-Stokes equations are considered as governing equations, and FEM is used to discrete the equations. Two scenarios are considered in the present paper. In the first scenario, the effect of parameters namely; Rayleigh number (103-105), Darcy number (0.001–0.1), Hartmann number (0–20), Radiation parameter (0.1–0.3), angle of magnetic field (0∘−90∘), and nanoparticle concentration (0.01–0.04) on heat transfer performance and entropy generation (Sgen) is studied. In the second scenario, the effect of geometry on Nusselt number (Nu) and Sgen is investigated. Da, Rd, and nanoparticle concentration have a positive impact on Nuavg and enhance heat transfer. Besides, the geometry with the best heat transfer performance is the one with the base wavy wall and the cylinder at the left side.

Magnetohydrodynamic Casson Fluid Flow Past a Vertical Plate in the Presence of Thermal Conductivity and Chemical Absorption

The present study examines effects of thermal conductivity and chemical absorption on Magnetohydrodynamic (MHD) convective boundary layer, flow of Casson fluid in a vertical plate. The governing flow equations are converted into dimensionless form using suitable non-dimensional parameters and variables and then numerically solved by explicit finite difference method (EFDM). Computations were performed to analyse the effect of thermo physical parameters of engineering interests associated with the flow quantities viz. velocity, temperature, concentration field and presented through graphs. It was found that chemical absorption parameter when increased has the tendency to enhance the fluid velocity as an opposite result is seen with higher values of Casson parameter. Comparison of present results with the previous literature was carried out to show the accuracy of the results.

Study of free convective unsteady magnetohydrodynamic flow of Oldroyd-B fluid in the presence of chemical reaction

This article is concerned with the study of free convective unsteady magnetohydrodynamic flow of the incompressible Oldroyd-B fluid along with chemical reaction. The fluid flows on a vertical plate that is impulsively brought in motion in the presence of a constant magnetic field which is applied transversely on the fluid. The structure has been modeled in the form of governing differential equations, which are then nondimensionalized and solved using a numerical technique, that is, Crank–Nicolson’s scheme to obtain solutions for velocity field, temperature distribution, and concentration profile. These solutions satisfy the governing equations as well as all initial and boundary conditions. The obtained solutions are new, and previous literature lacks such derivations. Some previous solutions can be recovered as limiting cases of our general solutions. The effects of thermophysical parameters, such as Reynolds number, Prandtl number, thermal Grashof number, modified Grashof number, Darcy number, Schmidt number, dissipation function, magnetic field, radiation–conduction, chemical reaction parameter, relaxation and retardation times on the velocity field, temperature, and concentration of fluid, are also examined and discussed graphically.

A Study of Transient Heat Transfer through a Moving Fin with Temperature Dependent Thermal Properties

In this article, heat transfer through a moving fin with convective and radiative heat dissipation is studied. The analytical solutions are generated using the two-dimensional Differential Transform Method (2D DTM) which is an analytical solution technique that can be applied to various types of differential equations. The accuracy of the analytical solution is validated by benchmarking it against the numerical solution obtained by applying the inbuilt numerical solver in MATLAB ($pdepe$). A good agreement is observed between the analytical and numerical solutions. The effects of thermo-physical parameters, such as the Peclet number, surface emissivity coefficient, power index of heat transfer coefficient, convective-conductive parameter, radiative-conductive parameter and non-dimensional ambient temperature on non-dimensional temperature is studied and explained. Since numerous parameters are studied, the results could be useful in industrial and engineering applications.

Numerical Analysis of Transient Heat Transfer in Radial Porous Moving Fin with Temperature Dependent Thermal Properties

In this article, a time dependent partial differential equation is used to model the nonlinear boundary value problem describing heat transfer through a radial porous moving fin with rectangular profile. The study is performed by applying a numerical solver in MATLAB (pdepe), which is a centered finite difference scheme. The thermal conductivity and fin surface emissivity are linearly dependent on temperature while the heat transfer coefficient is given by power law function of temperature. The effects of thermo-physical parameters, such as the Peclet number, surface emissivity coefficient, power index of heat transfer coefficient, convective-conductive parameter, radiative-conductive parameter and non-dimensional ambient temperature on temperature are studied.

Least square spectral collocation method for nonlinear heat transfer in moving porous plate with convective and radiative boundary conditions

In this article, the least square spectral collocation method (LSSCM) is proposed to predict temperature distribution and heat transfer efficiency of moving porous plate. In this moving porous plate, heat is dissipated to ambient flow by radiation and convection, and generated by non-linear internal heat source. Two types of boundary conditions of this moving porous plate, constant temperature boundary condition, and combined convective and radiative boundary conditions are taken into account. Otherwise, radiation heat transfer in moving porous plate is also considered and assumed by Rosseland approximation. Different with traditional porous heat transfer, heat transfer equation of moving porous plate can be considered as a special kind of convective-diffusive equation with strong convection features. The convection term may cause non-physical oscillation of solutions. To overcome this non-physical oscillation, the least square scheme is adopted. Lagrange interpolation polynomials and Chebyshev collocation points are employed for spectral discretization. In order to validate LSSCM for this nonlinear heat transfer process, a test case is examined. The computational results by LSSCM agree well with analytical solutions, which shows that the present model is high accuracy and good flexibility to simulate nonlinear heat transfer in moving porous plate. Then, effects of thermo-physical parameters on dimensionless temperature and heat transfer efficiency are comprehensively investigated.

The Effects of Thermo-Physical Parameters on Free Convective Flow of a Chemically Reactive Power Law Fluid Driven by Exothermal Plate

In this article, the effects of thermo-physical parameters on free convective flow of a chemically reactive power law fluid driven by exothermal plate is studied. The effect of thermal radiation on the fluid flow is investigated. Also, an exothermal surface reaction modeled by Arrhenius kinetics supplied heat to the power law fluid. Suitable similarity transformations are used to transform the non-linear partial differential equations into system of non-linear coupled ordinary differential equations. The obtained coupled non-linear ordinary differential equations are then solved numerically via fourth-order Runge-Kutta Fehlberg method. A parametric study is performed to illustrate the influence of thermal conductivity parameter, Grashof number, power-law index, velocity exponent parameter, Prandtl number, heat generation parameter, magnetic parameter, Eckert number, radiation parameter, Frank-Kamenetskii parameter, activation energy parameter, Brinkman number, reactant consumption parameter, and suction parameter on the fluid velocity and temperature profiles within the boundary layer. Numerical values of different controlling parameters for local skin friction coefficient and local Nusselt number are obtained and discussed. Comparison of the present work with existing literature was carried out and the results are in excellent agreement. The results also shows that skin friction coefficient decreases with increase in Eckert number, while the rate of heat transfer is enhanced at the surface of the plate as the Eckert number increase.

Investigation of the carbon monoxide post-combustion flame in the working space of a steelmaking unit

In order to optimize thermal mode of the steelmaking process and to bring down energy consumption, we examined effect of thermophysical parameters of the carbon monoxide post-combustion flame considering aerodynamic processes on the thermal-technological parameters during melting. Based on modern approaches and methods, we obtained data on the character of macro-physical processes that occur in the working space of the unit and in the reaction zone, taking into consideration the influence of aerodynamic processes in the bath of a steelmaking unit. We conducted a comparative analysis of the shape and temperature fields of the flame taking into consideration the influence of aerodynamic processes at different intensities of blowing the bath of a steelmaking unit with oxygen for different types of blowing devices. It was established that the shape and magnitude of temperature fields of the drigted flame varies depending on the content of carbon (from 4 to 0.1 %) in the melt, the intensity of blowing the bath with oxygen (from 1,800 to 2,400 m 3 /h), as well as design features of the blowing device (nozzle diameter and inclination angle). In this case, lances with an increase in the inclination angle of the nozzles to 50° and varying nozzle diameters from 10 to 20 mm, compared to lances of basic design (at the same inclination angles), make it possible to improve flame organization, to increase the length and temperature of the flame, to improve uniformity of the structure of flame, to increase heat exchanging surface between the flame and the bath, and to improve heating capability of the bath in a steelmaking unit. The studies reported in the present paper are applicable to industrial steelmaking units with the intensity of blowing the bath with oxygen in a range of 1,800 ‒ 2,400 m 3 /h. The results obtained bring us closer to the development of a rational design of the blowing device to optimize the thermal mode of steelmaking process that will make it possible to reduce energy consumption in steel production.

The Effect of Thermophysical Parameters on Temperature Distribution in the Primary Cooling Zone

Abstract The values of thermophysical properties obtained from the experimental research, and those that were calculated with thermodynamic databases, are crucial parameters which were used in the numerical modelling of the steel solidification process. This paper presents the results of research on the impact of specific heat and enthalpy, along with the method of their implementation, on temperature distribution in the primary cooling zone in the continuous steel casting process. A cast slab – with dimensions of 1100 mm and 220 mm and a S235 steel grade – was analysed. A mould with a submerged entry nozzle (SEN), based on the actual dimensions of the slab continuous casting machine, was implemented. The research problem was solved with the finite element method using the ProCAST software package. Simulations were conducted using the “THERMAL + FLOW” module.

Efficiency of Heat Transfer in the Forced Convection of a Heat Carrier (Air) Through the Porous Layers of a Capillary Porous Textile

Results are presented from an experimental study of temperatures and heat-transfer processes during the forced convection of a heat carrier (air) through a porous textile in the presence of counter-pressure. The air flow is laminar. Relations are constructed to predict temperatures in the porous textile with allowance for the effects of thermophysical parameters.

Surface Tension and its Temperature Coefficient of Liquid Sn-X (X=Ag, Cu) Alloys

The surface tension of liquid Sn-X (X=Ag, Cu) alloys was measured by the constrained drop method in the temperatures between 700 and 1500 K across whole composition range. Surface tension of the alloys increased with the content of Ag and Cu, and the temperature coefficient of the surface tension (d�= dT) had both positive and negative values. Experimental results were compared with the calculated results based on Butler’s model. The calculated results reasonably accorded with the measurements. The effect of thermo-physical parameters on the surface tension and the temperature coefficient were examined using the model. It was found that the temperature coefficient increases as the difference in the surface tension of component metals or the excess free energy increases in the high composition range of the component metal having higher surface tension, because of the surface enhancement of the other component metal.