Evaluation Of Heat Transfer Coefficient Research Articles

Impact of entropy generation and temperature gradient heat source on Couette flow in a permeable magnetic field

AbstractThis research paper focused on investigating the influence of various factors on steady Couette flow beneath a permeable bed. Factors studied included aligned magnetic field, thermal radiation, temperature gradient heat source, viscous dissipation, and Joules dissipation. The momentum and energy equations governing flow and heat transmission were analytically solved to predict the generation of entropy. The findings were visually presented through graphical representations, which effectively demonstrated the effect of these factors on the fluid's velocity, temperature, entropy production, and Bejan number. In addition, the shear stress and rate of heat transfer coefficient at the channel walls were computed and their behavior was documented in tables to provide further insights.

Numerical study on thermal hydraulics characteristics during steam submerged jet condensation from rectangular CD nozzle

The phenomenon of steam-water direct contact condensation (DCC) has significant importance in nuclear industry due to its rapid and efficient heat and mass transfer rates. In this numerical study, three dimensional simulations of steam submerged jet condensation from rectangular converging-diverging (CD) nozzle into subcooled water has been investigated. The steam condensation phenomenon has been captured from thermal phase change model as user defined function (UDF) in ANSYS Fluent software. The computational results were validated using experimental results as well as previously published numerical study. The effects of steam pressure and water temperature on distributions of various thermal hydraulics parameters including velocity, pressure, temperature, heat and mass transfer characteristics have been studied. The steam pressure and water temperature have been kept in the range of 200–500 kPa and 20–60 °C, respectively. The maximum value of jet velocity and heat transfer coefficient have been found as 803 m/s and 2.73 MW/m2K respectively. The peak velocity value increases with steam pressure. After maximum expansion point, the velocity profile curve is shifted downstream with steam pressure. The axial pressure distribution first decreases and then increases from expansion-compression waves. The axial temperature profile followed the similar trend as observed for axial steam pressure distribution. At constant steam pressure, the maximum rate of heat transfer coefficient decreases with the increase in water temperature. The maximum mass transfer rate under prescribed flow conditions has been found as 2789.8 kg/m3s. The peak mass transfer rate decreases with steam pressure and water temperature. The peak rates for heat and mass transfer have been observed in the nearby vicinity of nozzle exit location.

Slip regime MHD 2-liquid plasma heat transfer flow with hall currents between parallel plates

The influence of the slip factor on the MHD 2-liquid heat transfer flow of ionized gases within a channel between two non-conducting plates with Hall currents is investigated theoretically. Slip conditions were used to obtain solutions for the velocity and temperature fields, as well as the heat transfer rates. The flow characteristics of the two liquids are studied for estimates of the leading parameters, for instance the magnetic parameter, Hall and slip factors, viscosity, density, height, electrical conductivity and the thermal conductivity ratios. It was observed that an upsurge in temperature in the two zones is caused by the thermal conductivity proportion. The rate of heat transfer coefficient diminishes up to a certain point, after that it starts to increase as the magnetic and Hall parameters increase

Hall and rotation effects on magnetohydrodynamics two fluids slip flow of ionized gases via parallel conduit

AbstractIn a rotational model, the Hall effect on two‐liquid magnetohydrodynamics plasma flows of ionized gases between two nonconducting horizontal channel plates in a slip regime is researched. The produced magnetic field is omitted under the presumption that the Reynolds magnetic number is low. The modeled governing equations are solved by using the existing analytical method so as to obtain solutions in closed form. We use the first order slip to obtain exact results for the velocity, temperature fields, and hence the rates of heat transfer coefficient. On the basis of different values for the Hartmann number, slip, Hall, and rotation parameters, also viscosity, density, height, and electrical conductivity ratios of the two fluids, a parametric investigation of the velocity, temperature fields is initiated. It was concluded that the velocity declined with the augmented values of Hartmann number and the fluid velocity and temperature profiles in both the zones oscillate with the effect of the Hall parameter. In addition to that, the stimulations are present in the heat transfer coefficient rate with various values of the slip and rotational parameters.

Impact of Arrhenius activation energy on MHD nanofluid flow past a stretching sheet with exponential heat source: A modified Buongiorno’s model approach

Nanofluids have a wide range of applications in biological research. They are employed in targeted medication administration, hyperthermia (for cancer treatment) and differential diagnostics like magnetic resonance image (MRI). In light of these medical applications, the impact of an external magnetic field and an exponential heat source on the dynamics of [Formula: see text]–[Formula: see text] over a nonlinearly stretched surface has been investigated. A realistic modified Buongiorno model has been used which includes the effects of reaction rate, Biot number and activation energy. The boundary value problem governing the model is solved on MATLAB R2022a using the solver, BVP5C. Further, the consequences of different parameters on rate of heat transfer coefficient (Nusselt number), rate of mass transfer coefficient (Sherwood number), drag coefficient, velocity, temperature and volume fraction profile are observed graphically. It is noted that volume fraction and uniform heat source intensity have a positive effect on the Nusselt number and negative effect on Sherwood number. The effects of thermal radiation and magnetic field on volume fraction profile are, respectively, positive and negative. The current physics of flow across a vertical stretching surface is expected to serve as the foundation for various medical science, engineering and technology applications.

Thermal performance analysis of a flat-plate solar heater with zigzag-shaped pipe using fly ash-Cu hybrid nanofluid: CFD approach.

Regarding the detrimental impacts of using non-renewable energy resources on the environment and the importance of increasing heat transfer in heat exchangers, this research is aimed to increase the heat transfer surface of the collector pipe in contact with the absorber plate at the flat-plate solar collector by designing the pipe in a zigzag shape instead of conventional straight pipe. The 3D coupled investigation of fly ash-Cu/water hybrid nanofluids and analyzing the thermal performance of the proposed solar collector comprising zigzag pipe are the innovation of this research. Also, the effect of variations in mass flow rate, fluid inlet temperature, the volume fraction of nanoparticles on thermal efficiency, Nusselt number, pressure drop, Rayleigh number, and rate of heat transfer coefficient in three irradiations with two types of working fluids have been investigated. Results indicate that due to the enhancement in heat transfer surface in the case where the fluid path is zigzag, the thermal efficiency has improved compared to the straight pipe. In addition, with enhancing mass flow rate, temperature, and irradiation, the average Nusselt number increased. The heat transfer coefficient and pressure drop have the highest value by utilizing 0.5% and 3.5% nanoparticle concentration up to 10.84% and 7.603%, respectively, at a mass flow rate of 0.0089kg/s, and irradiation of 800W/m2. Finally, by calculating the efficiency index of the proposed flat-plate solar collector, the proper volume concentration for using copper-fly ash/water hybrid nanofluid is obtained at fraction of 0.5% and a mass flow rate of 0.0045kg/s.

Experimental study on flow and heat transfer of Al-kerosene nanofuels for regenerative cooling application

ABSTRACT In this paper, flow resistance and convective heat transfer of Al-kerosene nanofuels are studied experimentally. Al-kerosene nanofuels with mass fractions of 0.5 , 1 , and 2 g/L are prepared and applied as the flow medium for flow and heat transfer experiment via a heating facility. The experiment results indicate that the addition of aluminum nanoparticles has significant influence on both flow resistance and heat transfer performance. Compared to kerosene experiment, friction coefficient, heat transfer coefficient, and Nusselt number of Al-kerosene nanofuels all increase with different increasing rates. With a mass fraction of 1 g/L, the increase rate of friction coefficient was 11%, while the increase rate of heat transfer coefficient and Nusselt number is 19% and 12%, respectively. In order to evaluate the overall flow and heat transfer performance of Al-kerosene nanofuels, a performance evaluation criteria (PEC) is evaluated, and the present experimental results prove that the addition of aluminum nanoparticles gave a gain to the overall thermal performance of kerosene. The present study is aimed to provide useful references for regenerative cooling improvements.

Extension of the two-layer model to heat transfer coefficient predictions of nanoporous Si thin films

Heat exchange between a solid material and the gas environment is critical for the heat dissipation of miniature electronic devices. In this aspect, existing experimental studies focus on non-porous structures such as solid thin films, nanotubes, and wires. In this work, the proposed two-layer model for the heat transfer coefficient (HTC) between a solid sample and the surrounding air is extended to 70-nm-thick nanoporous Si thin films that are patterned with periodic rectangular nanopores having feature sizes of 100–400 nm. The HTC values are extracted using the 3ω method based on AC self-heating of a suspended sample with better accuracy than steady-state measurements in some studies. The dominance of air conduction in the measured HTCs is confirmed by comparing measurements with varied sample orientations. The two-layer model, developed for nanotubes, is still found to be accurate when the nanoporous film is simply treated as a solid film in the HTC evaluation along with the radiative mean beam length as the characteristic length of the nanoporous film. This finding indicates the potential of increasing HTC by introducing ultra-fine nanoporous patterns, as guided by the two-layer model.

A case study on thermo-hydraulic performance of jet plate solar air heater using response surface methodology

In this present work, the multi-hole jet impingement approach is used to augment the performance of the jet plate solar air heater by improving the rate of heat transfer coefficient between absorber plate and impinging air. The system's usefulness is analytically analyzed, and the influence of airflow rate, length of the collector, jet diameter, pitch distances at a stream, and span-wise directions on thermo-hydraulic efficiency is investigated by adopting Response Surface Methodology (RSM). A quadratic equation is generated by using the RSM technique, which is used to predict the thermohydraulic efficiency. The results show that the optimized results of the design parameters are at the airflow rate of 0.01386 kg/s, 1.5108 m of length, 0.0046 m of jet diameter with a stream-wise pitch distance of 0.05108 span-wise pitch distance of 0 0.03414 m. The comparison results show that the RSM model evaluated values have a deviation within a range of ±1.78% compared with the analytical values developed by the model.

Unsteady Electro-Magneto Hydrodynamic Flow and Heat Transfer of Two Ionized Fluids in a Rotating System with Hall Currents

An unsteady flow and heat transmission of ionized gases via a horizontal channel enclosed by non-conducting plates in a rotating framework with Hall currents is examined using electro-magnetohydrodynamic (EMHD) two-fluid heat flow. The Hall current impact is taken into account by assuming that the gases are totally ionized, the applied transverse magnetic field is very strong. For temperature and velocity distributions in two-fluid flow regions, the governing equations are solved analytically. For numerous physical parameters such as the Hartmann number, Hall parameter, rotation parameter, viscosity ratio, and so on, numerical solutions are visually displayed. It was discovered that an increase in temperature in the two regions is caused by the thermal conductivity ratio. It was also realized that an increase in rate of heat transfer coefficient at the plates is caused by either the Hartman number or the Hall parameter.

Flow and heat transfer analysis of water based copper nanofluid over a nonlinearly stretching sheet: A numerical approach

Specifically, copper nanoparticles are utilized in various fields like biomedicine, drugs, bioengineering, hereditary designing, catalysis, and beauty care products etc. The present study warrants the 3D magnetized flow and heat transfer of water based copper nanofluid past a nonlinearly stretching sheet in presence of thermal radiation and exponential space based heat source (ESHS). By the help of apposite match transformations, the governing partial differential equations (PDEs) are converted to couple nonlinear ordinary differential equations (ODEs) and are solved numerically using shooting method by the aid of MATLAB software. The presence of magnetic field and porous matrix lead to reduce the momentum boundary layer and may be treated as the control mechanism in the technological applications. An asymptotic variation of rate of heat transfer coefficient is marked in heating of the plate with higher power index for heat source, volume fraction and Biot number.

Multiple slips and heat source effects on MHD stagnation point flow of casson fluid over a stretching sheet in the presence of chemical reaction

The numerical analysis of the steady MHD stagnation point flow of a Casson fluid flow over a stretching sheet in the presence of a heat source and the first-order chemical reaction with multiple slip boundary conditions taking into account viscous dissolution, Joule warming, and the first-order chemical response with multiple slip boundary conditions is performed. The governing flow equations are interpreted with the assistance of identity transmutations, and the condensed nonlinear coupled ordinary differential equalisations are determined applying the shooting approach. With the use of graphs, the impacts of several factors on the dimensionless velocity, temperature, and concentration profiles are demonstrated. In addition, graphical representations of the variation in skin friction coefficient for different values of the Casson fluid parameter against the Eckert number, the variation in the rate of heat transfer coefficients for various values of the Radiation specification against the Schmidt number, and the variation in the rate of mass transfer for different values of the chemical reaction specification against the Schmidt number are provided. Our findings indicate that when there is an increase in Heat source and Chemical reaction parameter always leads to degeneration in temperature profile and Chemical reaction. The Chemical reaction parameter was found to enhance the Sherwood number.

Heat transfer and entropy generation analysis in a horizontal channel filled with a permeable medium in the presence of aligned magnetic field and temperature gradient heat source

The current investigation is concerned with heat transfer and entropy generation analysis in a horizontal channel brimming with porous medium in the existence of aligned magnetic field, viscous and joules dissipation and temperature gradient heat source. The boundary conditions are treated as constant values for velocity and temperature at lower and upper walls. An explicit solution of governing equations has been attained in closed system. The repercussions of pertinent parameters on the fluid velocity, temperature, entropy generation and Bejan number are conferred and scrutinized through graphs in detail. Additionally the expressions for shear stress and the rate of heat transfer coefficients at the channel walls are derived and results obtained are physically interpreted through tables. From the conquered results, it is addressed that Brinkman number Br enhances boundary layer thickness. Entropy generation increases with intensifying values of M, aligned angle ϕ, temperature gradient heat source parameter Q, characteristic temperature ration omega and permeability parameter K. The shear stress is same at both the lower and upper walls.

Experimental investigation of thermo-physical properties of drilling fluid integrated with nanoparticles: Improvement of drilling operation performance

Undoubtedly, the extraction of oil and gas from the reservoirs requires drilling processes. Drilling fluid is also required to perform drilling processes. The drilling fluid has several applications and one of its functions is to cool the bit. Normally, drilling fluids used in the world have a relatively low ability to transfer the heating from the bit. Therefore, cooling the bit is not done well. Therefore, solutions to increase the efficiency of drilling fluids in the field of heat transfer should be proposed. It is obvious that specific surface area is one of the variables affecting heat transfer. In other words, if the specific surface area of the drilling fluid molecules increases, the rate of heat transfer will increase. Since nanoparticles have a very high specific surface area, their use can be suggested. Because nanoparticles have a very high specific surface area, they can be used in the structure of drilling fluid components. Therefore, in this study titanium dioxide nanoparticle and carbon nanotube have been used to change the thermo-physical properties of drilling fluid. Results show the amount of specific heat increases about 1.26% by decreasing the size of titanium dioxide nanoparticles from 76 nm to 54 nm. In addition, experimental results show that the ratio of convective heat to conductive heat for drilling fluid integrated with carbon nanotubes is about 30% higher than drilling fluid integrated with titanium dioxide nanoparticles. Results show that the rate of heat transfer coefficient increases from about 2900 W/m2. oC to about 4000 W/m2. oC by decreasing the size of titanium dioxide nanoparticles from 76 nm to 54 nm. Also, it has been observed that the convective heat transfer coefficient increases from 2950 W/m2. oC to 3360 W/m2. oC by decreasing the average size of the carbon nanotubes from 76 nm to 54 nm.

Investigation of fin profile on the performance of the shell and tube heat exchanger

The Performance of the Shell and Tube heat exchanger is estimated by its effectiveness. The rate of Heat transfer differs by developing the temperature difference between the entity and theatmosphere, by raising the rate of heat transfer coefficient or the surface area of the entity. The initial two techniques are not monetarily attainable hence the addition of fins to the entity would improve the rate of heat transfer. Thereby, three various cases are taken into account for this study; it includes a base model (without fins) and two different profiles of fins attached to the hot fluid pipe. The surface area of the fins is the same and fitted to the hot fluid pipe so that the heat transfer increased with suitable boundary conditions, as they are examined for the best profile. Initially, the base model is analyzed with suitable boundary conditions, and the required results obtained. This process is repeated for the other two cases to define the optimum fin profile; then the optimum profile is analyzed for the better angle orientation of the fins and results collated for greater effectiveness.

Innovations in Eyring–Powell radiative nanofluid flow due to nonlinear stretching sheet with convective heat and mass conditions: Numerical study

ABSTRACT The augmentation of heat and mass transfer in an industrial process due to convective boundary conditions plays an important role which cannot be ignored and the study lead to saving energy, reducing process time and increasing thermal rating. The impact of nonlinear thermal radiation on Eyring-Powell nanofluid flow over a nonlinear elongating sheet with Joule and viscous dissipation is investigated. The well-posed boundary layer problem is reduced into a highly nonlinear coupled ordinary differential system by adopting similarity transformations. The resultant equations subject to convective temperature and concentration conditions are then solved by employing a Runge-Kutta-Fehlberg 45 order numerical scheme combined with shooting technique. The flow characteristics affected by the pertinent parameters are calculated and presented through the graphs. It is witnessed that the increase in mass Biot number and Lewis number aggregates to rise in the Sherwood number. Also, the rate of heat transfer coefficient rises with growing values of thermal Biot number and radiation parameter. These investigations are of great importance in food processing, crystal growth, fibre and wire coating, production of glass fibres and in many possible areas.

Numerical simulation of variable thermal conductivity on 3D flow of nanofluid over a stretching sheet

AbstractThe present investigation deals with the steady three-dimensional flow and heat transfer of nanofluids due to stretching sheet in the presence of magnetic field and heat source. Three types of water based nanoparticles namely, copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are considered in this study. The temperature dependent variable thermal conductivity and thermal radiation has been introduced in the energy equation. Using suitable similarity transformations the dimensional non-linear expressions are converted into dimensionless system and are then solved numerically by Runge-Kutta-Fehlberg scheme along with well-known shooting technique. The impact of various flow parameters on axial and transverse velocities, temperature, surface frictional coefficients and rate of heat transfer coefficients are visualized both in qualitative and quantitative manners in the vicinity of stretching sheet. The results reviled that the temperature and velocity of the fluid rise with increasing values of variable thermal conductivity parameter. Also, the temperature and normal velocity of the fluid in case of Cu-water nanoparticles is more than that of Al2O3- water nanofluid. On the other hand, the axial velocity of the fluid in case of Al2O3- water nanofluid is more than that of TiO2nanoparticles. In addition, the current outcomes are matched with the previously published consequences and initiate to be a good contract as a limiting sense.

Utilization of modified Darcy's law in peristalsis with a compliant channel: applications to thermal science

This research addresses the combined influence of MHD and slip on the peristaltic flow of non-Newtonian Sisko fluid model in a symmetric compliant characteristic channel. The fluid under investigation fills the porous space in a channel. The flexible walls of the channel surface propagate sinusoidal along the channel. Using long wavelength and low Reynolds number assumptions, the governing non-linear fluid flow equations are derived and tackled using perturbation scheme. The series form of solution are computed for fluid thermal distribution, concentration profile and momentum field along with the rate of heat transfer coefficient. Effects of numerous significant parameters are studied and deliberated through graphs. Excellent mode for regulating flows are obtained for larger values of electrical and magnetic fields and such results are significantly important at the time of surgery operation. It is observed that momentum distribution is decreased by augmenting the values of the Sisko parameter. The blood velocity can be controlled by regulating the magnetic field strength. Shear- thinning and shear- thickening nature of Sisko fluid model is also explained through these graphs.

Characteristics of primary air condensation in indirect evaporative cooler: Theoretical analysis and visualized validation

In hot and humid regions, an indirect evaporative cooler (IEC) could be utilized to pre-cool and pre-dehumidify fresh air by capturing the cooling potential of exhaust air from indoor air-conditioned space. The condensate retained on the surfaces of primary air channels has a profound impact on the heat transfer performance of the IEC. Although the studies of IEC considering condensation have received extensive attention recently, the micro scale condensation mechanism has seldom been addressed. In this paper, the analytical model and experimental investigation on the condensation heat transfer of the IEC under different dehumidifying conditions are presented based on visualized observation and measured data. An image processing method is developed to determine the area ratios of dropwise condensation (DWC) and filmwise condensation (FWC) on the plate surface. Results show that, with the increase of inlet primary air temperature, the area ratios of the DWC and FWC remain relatively stable at 0.4 and 0.6 respectively, while the overall heat flux slightly increases. The relative humidity of primary air can significantly influence the overall heat flux on the plate surface, as the increased FWC under high relative humidity results in a decreased growth rate of heat transfer coefficient. Higher air velocity can greatly improve the condensation heat transfer performance by enlarging the area ratio of the DWC. The results of this study enlighten the condensation heat transfer characteristics of primary air on the plate surface of the IEC, providing references for heat transfer enhancements of air-conditioning systems by promoting dropwise condensation.

Statistical analysis of enriched water heat transfer with various sizes of MgO nanoparticles using artificial neural networks modeling

In the present research, experimental data of the heat transfer coefficient for MgO aqueous nanofluids are modeled by the MLP artificial neural networks (ANN), for 4 types of nanoparticles with diameters of 20, 40, 50 and 60 nm, at 4 solid volume fractions of 0.5%, 1%, 1.5% and 2%, and at 11 Reynolds numbers from 3000 to 25,000. Modeling and predicting of the data like the empirical data, is proved the well capability of the ANN in modeling the data related to nanofluids’ heat transfer coefficient. Another interesting point is that, the heat transfer coefficient increases by decline of the nanoparticles’ diameter, and there is a direct relationship between the rise of solid volume fraction and the heat transfer coefficient. The increment rate of heat transfer coefficient, remained unchanged by increasing the Reynolds number, and increased with the rise of solid volume fraction. Present investigation showed that, ANN is able to save all the rules hidden in these changes with a high accuracy and take the advantage of them to predict the other data. In addition, a correlation in terms of variables affecting the heat transfer coefficient is obtained and presented in the article.