Heat Transmission Properties Research Articles

Mixed Convection Flow and Heat Transfer of Two Rotating Cylinders in a Trapezoidal Enclosure Filled with Porous Medium

The goal of this research is to investigate numerically mixed convection flow and heat transfer characteristics from two rotating cylinders in a trapezoidal enclosure filled with porous material for a variety of factors including rotation speed and direction, Richardson number, and the location of the cylinders. The results of this presentation were checked against accessible data and determined to be very similar. The heat transmission properties within the trapezoid were found to be substantially dependent on the Richardson number, speed, and direction of the spinning cylinders, as well as the location of the cylinders according to the findings of this study. Furthermore, it was discovered that the CW-CW casing produced more heat transfer as compared to the CCW-CW scenario for various Richardson numbers when the cylinders placed vertically. Furthermore, this research revealed that, for higher Richardson values, the rotation speed has no effect on the heat transfer increase inside the trapezoidal enclosure. The effect of the cylinders’ location on the average Nusselt number was also studied in this investigation. It was found the placing the cylinders in the vertical direction produced higher heat transfer compared with horizontal location for a trapezoid heated from below.

Temperature-Dependent Density and Magnetohydrodynamic Effects on Mixed Convective Heat Transfer along Magnetized Heated Plate in Thermally Stratified Medium Using Keller Box Simulation

The heat transmission properties along the non-magnetized geometries have been numerically obtainedby various researchers. These mechanisms are less interesting in engineering and industrial processes because of excessive heating. According to current studies, the surface is magnetized and the fluid is electrically conductive, which helps to lessen excessive surface heating. The main objective of the current analysis is to numerically compute the temperature-dependent density effect on magnetohydrodynamic convective heat-transfer phenomena of electrical-conductive fluid flow along the vertical magnetized and heated plate placed in a thermally stratified medium. For the purpose of numerical analysis, the theoretical process governing heat and magnetic intensity along a vertical magnetic plate is examined. By using suitable and well-known similarity transformations for integration, the non-linear coupled PDEs for the aforementioned electrical-conductive fluid flow mechanism are changed and subsequently converted into non-similar formulation. The Keller Box method is used to numerically integrate the final non-similar equations. The MATLAB software program plots the transformed algebraic equations graphically and quantitatively. The behavior of the physical quantities such asvelocity graph, magnetic field graph, and temperature plot along with their slopes that arerate of skin friction, the rate of heat transfer, and the rate of magnetic intensity for different parameters included in the flow model. The novelty of the current work is to compute the magneto-thermo analysis of electrically conducting flow along the vertical symmetric heated plate. First, we secure the numerical solution for steady part and then these results are used to find skin friction, heat transfer, and magnetic intensity. In the current work, the fluid becomes electrically conducing due to a magnetized surface which insulates heat during the mechanism and reduces the excessive heating. The results are excellent and accurate because they are satisfied by its given boundary conditions. Additionally, the current problems have a big impact on the production of polymer materials, glass fiber, petroleum, plastic films, polymer sheets, heat exchangers, catalytic reactors, and electronic devices.

Impact of the Thermophysical Properties of a Cuo-H<sub>2</sub>O-Based Nanofluid on the Performance of a Cylindrical Solar Concentrator

Sustainability in energy production, energy security, and global warming are major concerns facing the globe today. Cylindrical Solar Concentrator is extensively utilized for technologically advanced processes, heat, and power plant applications by utilizing daylight sunshine at no running cost. Numerous inputs and characteristics impact the concentrator's performance, with the type of heat transfer fluid and its mass flow rate being two of the most important. This paper gives a numerical investigation of the influence of thermo-physical attribute of CuO water-based nanofluids on the effectiveness of the Parabolic Trough Solar Concentrator in Ogbomosho weather condition (lat. 8o011, long. 4o111).The governing equations of nanofluids with laminar flow and steady state, using iterative relaxation techniques, as well as the efficiency of the concentrator, were solved. A C++ simulation program was developed to investigate the impacts of thermo physical parameters on concentrator efficiency, with nanoparticle sizes ranging from 1 to 10 percent and mass flow rates of 0.1 kg/s, 0.15 kg/s, and 0.2 kg/s, at a constant incident solar insolation flux of 186 W/m2. The results demonstrated that increasing the mass flow rate of the nanofluids improves the heat transmission properties. The thermo physical properties of CuO-based nanofluids and its effects on the performance of the solar parabolic trough collector are being examined. The impact of thermophysical attributes on thermal effectiveness results in improved thermal efficacy, heat transfer characteristics of nanofluids, and factors influencing its features in solar collectors, which determines its usability. The Parabolic Trough Collector system based on nanofluids is a promising technology with applications in green surroundings.

Influence of the Aspect Ratio on the Free Convection Heat Transmission Properties of a Container Containing Porous Materials

Nowadays, many industrial and modern applications depend on heat transport in porous zones. An experimental study of the natural convection heat transfer in a corrugated cavity with dimensions of (200, 250, 300) mm in length, a width of 200 mm, a depth of 27 mm, and an amplitude of 30 mm was filled with porous materials: glass balls (3, 6, 10) mm and alumina balls (6) mm, where the water was the working fluid. The top surface was exposed to the environment, while the bottom surface was subjected to constant heat flux (300, 500, 700, 900, 1100 W/m2), The front face, back face, and sides were insulated. In this study, temperature distribution, modified Rayleigh number, and Nusselt number values are foremost criteria, which are presented for three levels of aspect ratio. The influence of various aspect ratios on heat transfer is investigated. The results showed that the heat transfer coefficient decreases with the increase in aspect ratio. The highest value is when aspect ratio = 1. The enhanced Rayleigh number decreases as the aspect ratio increases by 10%.

Stability analysis of diamond-silver-ethylene glycol hybrid based radiative micropolar nanofluid: A solar thermal application

The current study emphasizes the stagnation point flow and heat transmission properties of a hybrid-based micropolar nanofluid over a porous Riga plate that is capable of both shrinking and stretching. A mathematical modeling of diamond-silver-ethylene glycol/water hybrid nanofluid has been explored. Here 20% of ethylene glycol and 80% of water are considered as the base fluid. Heat transfer proficiency of airplane wings is evaluated with the inclusion of distinguished effects like viscous dissipation and solar-based thermal radiation, so we included them in this paper. By employing some suitable transformations, the system of nonlinear ordinary differential equations are attained and numerically solved by using MATLAB software. The dual nature of skin friction, Nusselt number, and micro-rotation gradient solutions are demonstrated for a wide variety of relating parameters. The boundary-layer separation happens when number of results fails to happen ahead of the critical value of the contracting parameter. To show the effect on flow and heat transfer of appropriate parameters, graphs are used. Stability is shown to be better in solution one than in the second, according to the results. It is detected that the temperature has decelerated in the presence of micropolar heat conduction parameter for both solutions The radiation parameter reduces the Nusselt number of the hybrid nanofluid for the first solution and a contrary for second solution. The array of the skin friction values are moving downwards for fluctuating values of heat source/sink. Sun based energy is the chief source of heat from the sun, and it utilizes in photovoltaic cells, sun-based power plates, photovoltaic lights and sun-based hybrid nanofluids. Specialists are currently exploring the utilization of nanotechnology and sun-based radiation to further develop flight effectiveness.

Comparative evaluation of AI ‐based intelligent GEP and ANFIS models in prediction of thermophysical properties of Fe 3 O 4 ‐coated MWCNT hybrid nanofluids for potential application in energy systems

Hybrid nanofluids are gaining popularity owing to the synergistic effects of nanoparticles, which provide them with better heat transfer capabilities than base fluids and normal nanofluids. The thermophysical characteristics of hybrid nanofluids are critical in shaping heat transmission properties. As a result, before using thermophysical qualities in industrial applications, an in-depth investigation of thermophysical properties is required. In this paper, a metamodel framework is constructed to forecast the effect of nanofluid temperature and concentration on numerous thermophysical parameters of Fe3O4-coated MWCNT hybrid nanofluids. Evolutionary gene expression programming (GEP) and an adaptive neural fuzzy inference system (ANFIS) were employed to develop the prediction models. The model was trained using 70% of the datasets, with the remaining 15% used for testing and validation. A variety of statistical measurements and Taylor's diagrams were used to assess the proposed models. The Pearson's correlation coefficient (R), coefficient of determination (R2) was used for the regression index, the error in the model was evaluated with root mean squared error (RMSE). The model's comprehensive assessment additionally includes modern model efficiency indices such as Kling-Gupta efficiency (KGE) and Nash-Sutcliffe efficiency (NSCE). The proposed models demonstrated impressive prediction capabilities. However, the GEP model (R > 0.9825, R2 > 0.9654, RMSE = 0.7929, KGE > 0.9188, and NSCE > 0.9566) outperformed the ANFIS model (R > 0.9601, R2 > 0.9218, RMSE = 1.495, KGE > 0.8015, and NSCE > 0.8745) for the majority of the findings. The generated metamodel was robust enough to replace the repetitive expensive lab procedures required to measure thermophysical properties. Highlights Predictions of thermophysical properties of Fe3O4-coated MWCNT hybrid nanofluid AI-based ANFIS and GEP models performed well on statistical indices ANFIS and GEP-based prognostic models validated and compared with Taylor diagrams

Revisiting the influence of artificial roughness shapes on heat transfer enhancement

Solar air heating is a type of heating that uses the sun's energy to heat air. This technology is most commonly used in commercial and industrial processes. A SAH is simple to install and operates efficiently. However, it is simple to maintained and is usually not energy-efficient. A SAH's poor efficiency is caused by the development of a laminar sub-layer. This contributes to the overall thermal losses and lowers the efficiency. An improved design of a SAH duct can be achieved by roughening up the surface. This study aims to investigate the effects of artificial roughness on the friction and heat transmission properties of the duct. To achieve this goal, this study will examine several research investigations in which various roughening elements have been employed to increase the heat transfer while minimising the effect of the friction factor.

Applied Mathematical Modelling and Heat Transport Investigation in Hybrid Nanofluids under the Impact of Thermal Radiation: Numerical Analysis

Nanofluids are solid-liquid mixtures that have a dispersion of nanometer-sized particles in conventional base fluids. The flow and heat transmission in an unstable mixed convection boundary layer are affected by the thermal conductivity and dynamic viscosity uncertainty of a nanofluid over a stretching vertical surface. There is time-dependent stretching velocity and surface temperature instability in both the flow and temperature fields. It is possible to scale the governing partial differential equations and then solve them using ordinary differential equations. Cu and Al2O3 nanofluids based on water are among the possibilities being investigated. An extensive discussion has been done on relevant parameters such as the unsteadiness parameter and the mixed convection parameter's effect on solid volume fraction of nanoparticles. In addition, alternative nanofluid models based on distinct thermal conductivity and dynamic viscosity formulas are examined for their flow and heat transmission properties. On the basis of the comparison, it is concluded that the results are spot on for steady state flow.

Battery thermal management system using nano enhanced phase change materials

Electric vehicles are being developed as a crucial tool in the fight against global warming and car pollution. As a result, battery heat management is critical for optimal operation in all climates in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Extreme or higher temperatures may cause the battery’s maximum voltage to drop and its durability to deteriorate. An effective battery cooling system is required for the safe operation of electric vehicles throughout their lifecycle. The current work involves the simulation of a battery thermal management system that employs nano-enhanced phase change materials (NEPCM). Ansys Fluent is used to conduct the numerical analysis. To test the thermal performance, paraffin wax is used as the base fluid, into which various combinations of nanoparticles such as Copper Oxide, Copper, and Multi Walled Carbon Tube (MWCNT) are disseminated. The parametric study is carried out by altering the battery temperature and nanoparticle volume fraction. The findings show that at large particle volume fractions, the battery system’s heat transmission properties are greatly improved. The findings of this study will aid in the identification of optimal NEPCMs with increased thermal performance.

Development of an Optimal/Robust Control Strategy for Electrical Energy Cost Minimization in an Air-Conditioning Plant

This paper focuses on modelling the thermal behaviour of buildings and designing an optimal control algorithm for their HVAC systems. The problem of developing a good model to capture the heat storage and heat transmission properties of building thermal elements such as rooms and walls is addressed by using the lumped capacitance method. The equations governing the system dynamics are derived using the thermal circuit approach, and by defining equivalent thermal masses, thermal resistors and thermal capacitors. In the control design part, we have introduced a control algorithm which is composed in Pontryagin’s Minimum Principle controller. The optimal tracking problem is solved in Pontryagin’s Minimum Principle controller where the interconnection of all walls are taken into consideration. The Pontryagin’s Minimum Principle controller 0minimizes a quadratic cost function which has two quadratic terms. One takes into account the comfort level and the other represents the control effort, i.e. the energy consumed to operate the HVAC system. Simulation results for a single room example show energy savings using this control algorithm over a conventional PI controller.

Flammability behavior of fiber–fiber hybrid fabrics and composites

AbstractThe effect of heat flux levels on burning behavior and heat transmission properties of hybrid fabrics and composites has been investigated using cone calorimeter and heat transmission techniques. The hybrid fabric structures woven out of E‐glass (warp) and polyether ether ketone (PEEK) (weft) and E‐glass (warp) and polyester (weft) have been studied at high heat flux levels keeping in view the flame retardant requirements of structural composites. The performance of the glass–PEEK fabric even at high heat flux levels of 75 kW/m2 was comparable with the performance of glass–polyester fabric evaluated at 50 kW/m2. The results further demonstrate that glass–PEEK hybrid fabrics exhibit low peak heat release rate, low heat release rate, low heat of combustion, suggesting an excellent combination of materials and fall under the low‐risk category and are comparable with the performance of carbon fiber‐epoxy‐based systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Measurement and Analysis of Thermal Conductivity of Rocks in the Tarim Basin, Northwest China

Abstract:As a parameter that describes heat transmission properties of rocks, thermal conductivity is indispensable for studying the thermal regime of sedimentary basins, and retrieving high‐quality data of thermal conductivity is the basis for geothermal related studies. The optical scanning method is used here to measure the thermal conductivity of 745 drill‐core samples from the Tarim basin, the largest intermontane basin with abundant hydrocarbon potential in China, and water saturation correction is made for clastic rock samples that are of variable porosity. All the measured values, combined with previously published data in this area, are integrated to discuss the distribution characteristics and major controlling factors that affect the thermal conductivity of rocks in the basin. Our results show that the values of thermal conductivity of rocks generally range from 1.500 to 3.000 W/m·K with a mean of 2.304 W/m·K. Thermal conductivity differs considerably between lithological types: the value of a coal sample is found to be the lowest as being only 0.249 W/m·K, while the values for salt rock samples are the highest with a mean of 4.620 W/m·K. Additionally, it is also found that the thermal conductivity of the same or similar lithologic types shows considerable differences, suggesting that thermal conductivity cannot be used for distinguishing the rock types. The thermal conductivity values of mudstone and sandstone generally increase with increasing burial depth and geological age of the formation, reflecting the effect of porosity of rocks on thermal conductivity. In general, the mineral composition, fabric and porosity of rocks are the main factors that affect the thermal conductivity. The research also reveals that the obvious contrast in thermal conductivity of coal and salt rock with other common sedimentary rocks can induce subsurface temperature anomalies in the overlying and underlying formations, which can modify the thermal evolution and maturity of the source rocks concerned. This finding is very important for oil and gas resources assessment and exploration and needs further study in detail. The results reported here are representative of the latest and most complete dataset of thermal conductivity of rocks in the Tarim basin, and will provide a solid foundation for geothermal studies in future.

The Influence of Sweating on the Heat Transmission Properties of Cold Protective Clothing Studied With a Sweating Thermal Manikin

One of the objectives of the European SUBZERO project was to study the influence of sweat evaporation and condensation on the heat transmission properties of cold protective clothing. With the sweating thermal manikin Coppelius, water vapour transfer through and water condensation in the clothing can be determined simultaneously with the thermal insulation. In this study, 4 cold protective ensembles, intended for use temperatures between 0 and -50 °C, were measured with the dry manikin and at 2 different sweating rates. In addition, the ensembles were measured with non-sweating thermal manikins and in wear trials.

Computation of Solar Radiation and Heat Transmission Properties of Glass for Use in Buildings

The most important example of use of transparent materials in building construction is glass. Detailed knowledge and study of disposal of solar radiation incident upon a glass element, e.g., window and data on its reflection, absorption and transmission properties in tabular or in graphical form can be of much use to architects and building scientists in the thermal design of buildings, application of passive systems and cooling and heating load calculation. The aim of this paper is to discuss the subject in some detail and to provide the above data on solar radiation disposal and heat transmission properties of ordinary glass currently used in buildings in readily usable form to architects and buildings designers for simplified calculation of energy transmission through single and double-glazings.

The Thermal Transmittance of Windows

The thermal transmission properties of modern windows are recognised to be quite complex and difficult to evaluate by measurements alone. This article from the Federal Institute for Materials Testing (BAM) in Berlin shows how numerical methods by computer programs may be used to calculate the thermal transmittance U and the temperature distribution through a steel-stiffened plastic window and several variations of insulating glazing. The results were in agreement with accepted experimental values, and the authors suggest that the numerical methods should now allow manufacturers to predict heat transmission properties of windows at the design stage.

Heat Transmission in Cellulosic Fiber Insulation Materials

Abstract Measurements of heat transmission in a number of different loose fill cellulosic insulations have been made by heat flow meter and guarded hot plate methods. Effect of temperature and density have been studied together with a limited investigation on moisture effects. Variations of up to 18 percent occur in the same nominal materials from different sources. This fact indicates that the raw materials and their processing can have a significant influence on the heat transmission properties. For the optimum density range of 35 to 40 kg/m3 and above, the different materials have a very similar temperature coefficient of thermal conductivity. Lower density materials have a significant radiation contribution to their total heat transmission characteristics.

Total Heat‐Transmission Coefficients of Amber and Green Glasses in Temperatures of Melting Range

Measurements of an over‐all heat‐transmission coefficient for several commercial amber glasses were carried out in a pilot‐scale furnace at temperatures of the melting range. The data obtained were used in deciding depth and insulation of tank furnaces. It appears that the transmission of light of amber glasses in the near‐infrared range gives a practical indication of these heat‐transmission properties. The same pilot‐scale furnace was used to investigate the effect of chromium oxide, nickel oxide, and iron oxide on the over‐all heat‐transmission coefficients of green glasses. An empirical equation was derived, relating the heat‐transmission coefficient to the concentration of the coloring oxides. Of the three oxides, the effect of the nickel oxide on heat transmission is the strongest and the effect of the iron oxide is the weakest.