Values Of Transfer Coefficient Research Articles

PEDOT wrapped biomimetic recognition system for selective determination of carcinogenic phenacetin content in drug samples

A molecular imprinted polymeric (MIP) recognition system comprising of PEDOT swaddled CoWO4 nanocapsules has been developed for the electrochemical detection of carcinogenic phenacetin drug. Facile hydrothermal route was employed to synthesize CoWO4 whereas, EDOT was wrapped around under chemical polymerization at room temperature. A series of characterizations revealed that electrostatic interactions generated between thiophene sulfur of PEDOT and metal atoms of CoWO4 have prompted the homogeneously wrapped molecularly imprinted nanocomposite. The obtained peak potential plotted against the CV scan rate revealed involvement of 2 electrons in the electroxidation detection process of phenacetin. The values of charge transfer coefficient α (0.69) and charge transfer rate constant ks (2.24 s−1) at electrode-electrolyte interface during the detection procedure were also evaluated. The nanoarchitecture of the designed MIP exhibited abundant imprinted sites to selectively bind the template molecule in terms of shape, size and functionalities resulted in significant augmentation in sensitivity (0.14 µA nM−1 cm−2) and a very low detection limit (0.091 nM). Phenacetin content in homeopathic and allopathic drug samples were successfully quantified with more than 95 % accuracy by employing the MIP modified electrode. The present research introduces new possibilities for identification of carcinogenic phenacetin used as adulterants in various narcotic drug samples.

Numerical simulation and optimization of heat pipes using nanoparticles: a feasibility study

This study investigated the effect of different particle sizes on the thermal effectiveness of a cylindrical screen mesh heat pipe using silver nanoparticles as the test substance. The study compared the effects of three different particle sizes (30, 50, and 80 nm) on heat transmission characteristics of the heat pipe. The results showed that the heat pipe’s thermal conductivity increases as the particle size decreases. The thermal conductivity measurements revealed 250 W/mK, 200 W/mK, and 150 W/mK for particles of 30, 50, and 80 nm sizes. Furthermore, the study analyzed thermal resistance of heat pipe for each particle size and found that as particle size decreases, thermal resistance decreases as well. The heat transfer coefficient values for particle sizes of 30, 50, and 80 nm were found to be 5500 W/m2K, 4500 W/m2K, and 3500 W/m2K, respectively. The ANOVA method was used to analyze the results statistically. The 30 nm particle size was found to have significantly higher thermal conductivity, lower thermal resistance, and a higher heat transfer coefficient than other particle sizes. Additionally, simulations were conducted to analyze the temperature variation of the hot source as a function of power dissipation for design and optimization.

Thermo-hydraulic rating of a shell and tube heat exchanger for acetone cooling using bell-delaware method

Shell and tube heat exchangers are becoming the most popular devices for the transfer of heat in industrial process applications. In the present work, the thermo-hydraulic rating of a shell and tube heat exchanger proposed to cool an acetone stream was carried out using the Bell-Delaware methodology. An overall heat transfer coefficient value of 426.70 W/m2.K, a calculated heat transfer area of 121.46 m2, and a percent excess area of 20.83% were obtained. Both the pressure drop of acetone and water had values of 1,622.36 Pa and 3,020.46 Pa, respectively. The proposed shell and tube heat exchanger can be used satisfactorily for the required application, since the percent excess area does not exceed the 25%, and the pressure drops of both fluid streams are below the limit values established by the process.

Trefftz functions methods in analysis of the effect of enhanced heated surface on FC-72 flow boiling in minichannels

This paper focuses on time-dependent flow boiling heat transfer. The main element of the research stand was the test section with 11 rectangular minichannels of 1 mm depth. The FC-72 was heated by a thin foil during upward flow. The temperature of the outer surface of the foil was measured by infrared thermography. Two types of foil surface were tested: smooth and enhanced with recesses produced using emery paper. The main objective was to verify whether the enhanced surface helps to obtain a better heat transfer efficiency compared to the smooth surface. The 2D mathematical model of heat transfer was proposed, while methods with Trefftz functions were applied to solve the time-dependent problem of heat transfer. The Robin condition was used to determine heat transfer coefficients at the interface between the foil and the fluid. Experimental data on temperature and pressure and their validation were presented and discussed. Results based on the heat transfer coefficients were provided. They covered the calculation procedure, the determination of the mean relative error and results validation with using the 1D approach. The heat transfer coefficients as a consequence of application of the Trefftz method and the hybrid Picard-Trefftz method in the calculation procedure with comparison analysis of the results were shown. Furthermore, comparisons aimed at obtaining the results characteristic for smooth and enhanced surfaces were also conducted. In the experiment with an enhanced heated surface, the values of the heat transfer coefficient appeared to be higher. Boiling curves were illustrated and discussed.

Experimental and Numerical Analysis of the Efficacy of a Real Downhole Heat Exchanger

In this paper, a three-dimensional (3D) numerical model based on the finite element method (FEM) is developed to determine the fluid flow and heat transfer phenomena in a real multi-tube downhole heat exchanger (DHE), designed ad hoc for the present application, considering natural convection inside a geothermal reservoir. The DHE has been effectively installed and tested on the island of Ischia, in southern Italy, and the measurements have been used to validate the model. In particular, the authors analyze experimentally and numerically the behavior of the DHE based on the outlet temperature of the working fluid, thermal power, overall heat transfer coefficient, and efficiency. Furthermore, the influence of the degree of salinity on the performance of the DHE has been studied, observing that it degrades with the increase in the degree of salinity. The results show that the DHE allows to exchange more than 40 kW with the ground, obtaining overall heat transfer coefficient values larger than 450 W/m2 K. At the degree of salinity of 180 ppt, a decrease in the efficiency of the DHE of more than 8% is observed.

Experimental study for artificial neural network modeling on thermal and flow performances of electric traction motor with oil spray cooling

The oil spray cooling is emerging as advanced thermal management technique for next generation electric traction motor. The performance of oil spray cooling needs to be mapped and predicted based on various influential factors to develop efficient thermal management system for electric traction motors. In the present work, the thermal and flow performances are experimentally investigated and predicted using an artificial neural network (ANN) for electric traction motor with oil spray cooling. The thermal and flow performances are extracted in terms of maximum temperature, heat transfer coefficient, Nusselt number, spray pressure and spray power consumption. The effects of nozzle types, spray heights, volume flow rates and chiller temperatures are analyzed as operating factors. The ANNs are modeled considering Levenberg-Marquardt (LM) training variant, 10 hidden neurons and Tangential-sigmoidal (Tan) and Logarithmic-sigmoidal (Log) as transfer functions. The thermal and flow performances are superior for full cone followed by hollow cone and spiral nozzles in decreasing order. The higher spray height, higher volume flow rate and lower chiller temperature show optimum values of maximum temperature and heat transfer coefficient. The spray power consumption is maximum in case of higher volume flow rate, reported less variation with change in spray height and chiller temperature. The ANN model comprising of LM-Tan algorithm is recommended as the best model with prediction error within ±1% for all thermal and flow performances. The predicted results from the optimum ANN model are validated with experiments with maximum coefficient of determination (R2) and coefficient of variance (COV) as 0.99 and 3.20, respectively. The correlations for thermal and flow performances in terms of all influential factors are proposed using the optimum ANN model.

Experimental Study on Indirect Liquid Cooling Performance of Metal 3D-Printed Cold Plates for Battery Thermal Management

Two new cold plates manufactured via metal 3D printing were experimentally investigated for thermal performance analysis in indirect liquid cooling operations; then they were compared to the traditional cold plates. Experiments were performed with different coolant inlet temperatures (15.7 °C and 24.5 °C) and ambient air velocities (0.5 m/s and 3 m/s) at tropical conditions; hereby, the impact of high dew point temperatures at tropics was also investigated. Body-centered cubic (BCC) and pillar elements were applied in the cooling cavity of the cold plates. The results showed that the target surface temperature in both BCC- and pillar-filled plate designs was maintained below the limits at the lower inlet temperature. However, at the higher inlet temperature, the temperature was only maintained below the limit when the ambient air velocity was 3 m/s. The convective heat transfer coefficient at the inlet temperature of 15.7 °C was found 1.5 and 2.5 times higher than the convective heat transfer coefficient value at the inlet temperature of 24.5 °C for the pillar- and BCC-filled plates, respectively. The performance evaluation criterion values were found in the range of 1.2 − 2.4, which depended on the operating conditions and were already higher than the referenced studies in the literature.

Heat transfer by transiently superheated fluids: Decay of unstable water-based mixtures

The present study sets out to elucidate the characteristic features of instantaneous heat transfer accompanying transient superheating of partially miscible mixtures having a lower critical solution temperature (LCST) with respect to the liquid–liquid binodal and the diffusion (liquid–liquid) spinodal. The research has employed the method of controlled pulsed heating of a wire probe, which can be used to directly measure heat flux into the medium at a strictly fixed heater temperature Tst. At a characteristic heating time of 100 ms, values of Tst were gradually increased from 100 to 500 °C, while the corresponding pressures varied from 0.1 to 35 MPa. The objects of study were aqueous solutions of PPG-425 and PPG-2000 polypropylene glycols, as well as 2,6-Lutidine, all having LCST in the range convenient for achieving large superheats. The values of the heat transfer coefficient (whose highest values reached 90 kW/m2 K for the solution with 5 wt% PPG-2000 content at the superheat degree of about 390 °C) and the energy absorbed by the solution were calculated on the basis of the primary data. The calculation results related the individual features of the studied systems to the phase diagram and characteristic system relaxation times depending on the concentration and superheat degree with respect to the spinodal. The applicability of such systems as coolants under conditions of high-power heat release for elements with a short response time is demonstrated. Based on the experimental results, we validated the selection of solutions as coolants in the concentration range from the left branch of the spinodal to the critical concentration of the solution.

A sensitive, selective non-enzymatic electrochemical detection and kinetic study of glucose over Pt nanoparticles/SWCNTs/NiO ternary nanocomposite

BackgroundThe coupling of inorganic metal nanoparticles, semiconductor-based metal oxide nanostructures, and carbon nanomaterials is a promising strategy to fabricate efficient electrochemical sensors. Herein, we successfully designed a sensitive and selective electrochemical glucose sensor using Pt nanoparticles (PtNPs) decorated single-wall carbon nanotubes (SWCNTs) and nickel oxide (NiO) nanostructure-based composite materials. MethodsThe nanocomposite was synthesized without applying any dispersant or stabilizer using simple ultrasonication and photo-reduction techniques. Significant findingsThe morphology of nanocomposite reveals a homogenous dispersion of CNTs and PtNPs over the NiO nanostructure. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that the ternary nanocomposite-modified glassy carbon electrode (Pt@CNTs/NiO/GCE) displayed enhanced catalytic activity compared to CNTs/NiO/GCE, NiO/GCE or bare GGE electrodes. Kinetics studies indicated that the glucose electrooxidation using Pt@CNTs/NiO modified GCE followed irreversible diffusion-controlled kinetics with a transfer co-efficient value (α) ≈ 0.50. Amperometric sensing investigation revealed excellent sensitivity (149.36 µA mM−1 cm−2) and a lower limit of detection value (2.16 µM). The currently fabricated sensor electrode showed appropriate selectivity in the presence of various organic and inorganic species with outstanding repeatability, reproducibility, and sensor stability. The newly fabricated nanocomposite can represent a promising electro-catalyst for the efficient sensing of glucose and other biomolecules by the electrochemical approach.

Influence of the Skin and Proximity Effects on the Thermal Field in a System of Two Parallel Round Conductors

This paper presents a semi-analytical method for determining the distribution of the thermal field in a system of two parallel round conductors, taking into account the skin and proximity effects. The method of a suitably constructed Green’s function was applied to find an analytical expression for the eigenfunctions describing the temperature distributions. In turn, the relevant integrals, which cannot be determined analytically, were calculated numerically. The foundation of the method is the knowledge of the current density distribution in the conductors. As a result, the steady-state distribution of the temperature field in the conductors for various parameter values can be determined. The obtained numerical results were positively verified using the finite element method. Using the developed method, the share of skin and proximity effects in the temperature rise and steady-state current rating was evaluated. Closed analytical formulas were obtained for the AC case with the skin effect taken into account. When the skin depth is smaller than the wire radius, the skin effect has quite a large impact on the conductor temperature. The impact of the proximity effect is much smaller but clearly noticeable when the distance between the wires is smaller than five times the wire radius. In addition, the influence of the value of the heat transfer coefficient on the thermal field of the conductors was also examined.

3D numerical investigation on flow boiling characteristics in large length-to-diameter ratio microchannel

To meet the demand of thermal management with large power and high heat flux in the future engineering applications, more and more attentions have been draw to develop the two-phase microchannel cooling technology. In this work, a three dimensional numerical investigation is performed to study the influence of mass flux and heat flux on the two phase flow boiling characteristics in a single microchannel with large length-to-diameter ratio. The related calculation results show that the Volume of Fluid (VOF) model coupled with Lee model can predict the two phase pressure drop and heat transfer coefficient of the microchannel well. And the flow patterns in the microchannel are classified as bubbly flow, slug flow and annular flow, which can be captured by this numerical model precisely. Besides, the transient pressure drop augments with the increase of mass flux. But the effect of mass flux on the amplitude of quasi-steady pressure drop and the peak value of time-averaged heat transfer coefficient along the microchannel is small. At last, the amplitude of quasi-steady pressure drop increases with the augmentation of heat flux. The maximum and fully developed time-averaged heat transfer coefficients along the microchannel increase with the heat flux.

Thermal-hydraulic characterization of R513A during flow boiling inside a 6.0 mm horizontal tube, comparison with R134a and development of a new correlation

This paper presents two-phase heat transfer coefficient and pressure drop data of refrigerant R513A, a new azeotropic mixture conceived as possible alternative to R134a for medium temperature small-size refrigeration systems. All the experiments were performed in a commercial horizontal stainless-steel tube having an internal diameter of 6.0 mm and an outer diameter of 8.0 mm. The channel heating was obtained through DC current and Joule effect. The effect of the main operating parameters in terms of mass flux (from 150 to 500 kg/m2s), heat flux (from 5.0 to 40 kW/m2), saturation temperature (from 30 to 50 °C) and vapor quality (from the onset of boiling up to the dry-out occurrence) was analyzed and discussed for the heat transfer coefficient values, finding that both convective and nucleate boiling were significant contributions. The same ranges of mass flux and saturation temperature were also applied to frictional pressure gradient trends with vapor quality, taken in adiabatic conditions. The thermo-hydraulic performances were then compared with those of R134a, obtaining lower heat transfer coefficients and very similar pressure gradients. Finally, the collected experiments were assessed with values predicted from the most quoted correlations available in literature. A new composite method for nucleate-dominant or convective-dominant mechanisms was proposed for the evaluation of the heat transfer coefficient, with a mean absolute error of 25.3%, whereas the frictional pressure gradient values were well predicted with the Friedel correlation, that provides a mean absolute error of 13.8%.

Feasibility of nitrate adsorption from aqueous solution by nitrogen and oxygen-modified pine bark biochar: experimental and computational approach

Efficient and economical wastewater treatment has presented itself as a global challenge. In this context, adsorption is one of the most effective methods to remove contaminants from wastewater. The present study evaluated the feasibility of chemically modified pine bark biochar’s nitrate adsorption ability. Pine bark biochar was modified with urea and sulfuric acid to remove nitrate from an aqueous solution. The physicochemical properties of the biochar samples, such as pH, pH at point of zero charges, surface atomic composition, surface morphology, and surface area, were evaluated. The equilibrium adsorption data were fitted to the Langmuir and Freundlich isotherm models. The kinetic data were fitted to different kinetic models (pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich). The adsorption data fitted well with the Langmuir and pseudo-first order models. The maximum nitrate adsorption capacity was found to be 1.548 mg g−1. Mass transfer studies were conducted to identify the rate-limiting step, values of the external mass transfer coefficient, and diffusion coefficient in the nitrate adsorption process by the modified biochar. The external mass transfer coefficients were in the range of 2.2 × 10–11–2.86 × 10–10 m s−1. The intraparticle diffusion coefficient ranged from 6.53 × 10–10 to 1.78 × 10–9 m2 s−1. The Biot number value less than 100 indicated that the adsorption was controlled by film diffusion. Interaction energies between nitrate ions and model biochar structures were calculated DFT-based quantum chemical software (Gaussian). The positive interaction energy values (2.3485–2.485 eV) suggested nitrate adsorption on model biochar structures was thermodynamically not feasible.Graphical

Transient thermal behavior of a passive heat sink integrated with phase change material: A numerical simulation

This paper presents a numerical investigation of the thermal performance of a heat sink augmented with phase change material (PCM) for passive electronic cooling applications. The PCM-based heat sink employed N-eicosane as the PCM, which has a suitable melting temperature and high latent heat capacity for electronic cooling applications. A numerical simulation based on the enthalpy-porosity method was developed to analyze the impact of both PCM inclusion and induced natural convection airflow on the base temperature of the heat sink. The operational conditions were selected as three constant heat fluxes of 2, 3, and, 4 kW/m2 and four critical base temperatures of 40, 45, 50, and 55 °C. The influence of fin numbers on the thermal behavior of both PCM-based and conventional (without PCM) heat sinks was also investigated by considering the three fin numbers of 4, 5 and, 6. The PCM integration into the heat sink effectively delayed the rise of base temperature and extended the safe operation time compared to a conventional one. The thermal performance enhancement ratio of the PCM-based heat sink over the conventional heat sink ranged from 1.53 to 2.81, depending on the selected heat flux and critical temperature. The effect of fin numbers on thermal performance was more significant at lower heat fluxes. It was observed that the PCM-based heat sinks achieved a higher time-averaged heat transfer coefficient than the conventional heat sinks, and this coefficient increased with the heat flux and decreased with the fin number. For both PCM-based and conventional heat sinks, it was observed that increasing the fin number reduces the heat transfer coefficient value due to the suppressing effect of fins on natural convection current. The results demonstrate the potential of using passive PCM-based heat sinks for improving the reliability and efficiency of electronic devices compared to conventional heat sinks.

Determination of a mass-transfer coefficient for wood drying by means of thermography

ABSTRACT In the present work, it was demonstrated that mass transfer and mass transfer coefficients related to the wood drying process can be satisfactorily quantified using thermography. The method was based on continuous measurements of the wood’s surface temperature, which were converted to a vapor pressure at the wood surface. The results showed that the values of the experimentally obtained transfer coefficients were in the same order of magnitude as values obtained with classical empirical correlations that apply in boundary layer theory. The measurements also showed that an average value of the mass transfer coefficient obtained during drying satisfactorily describes the complete process. The measurement set-up makes it possible to determine a surface potential accurately and continuously, which is useful in the assessment of wood drying processes.

Математичне моделювання пристінної оливної плівки в камері підшипника ГТД

The most preferable result of modeling the flow in the BC is the determination of the heat transfer coefficient to the inner wall. The complexity of solving this problem is due to both the complex geometry of the BC and the presence of a two-phase flow, the structure of which changes from air-droplet in the core to a nearly liquid in the wall oil film. Available research results show that even three-dimensional CFD modeling of such a flow does not completely solve the problem. At the same time, the calculation time is long, and the results require, at a minimum, selective experimental validation. At the same time, it can be considered proven that the main mechanism of heat transfer from the core to the wall region of the BC is related to the radial flow of droplets, and the thermal resistance of the wall oil film has a decisive effect on the value of the internal heat transfer coefficient. It is advisable to model these media on the basis of a two-dimensional problem with the averaging of phase parameters along the axis. Considering the small volume fraction of droplets, the Lagrangian approach can be used to model the two-phase flow in the core of the BC. This allows consideration of not only the polydispersity of the droplets, but also the creation and movement of secondary droplets during the formation of the wall oil film. One of the main problems in the modeling of the wall film is the definition of its flow regime and the corresponding criterion equations for calculating the coefficients of friction and heat transfer. Most of the equations use the longitudinal coordinate of the plate as a geometric parameter and cannot be applied to the bearing chamber. In this study, the possibility of converting the film flow into a flow similar to that occurring in a flat pipe is substantiated. This allows not only to consider the geometric features of the BC, but also to use the corresponding Reynolds numbers and similarity equations for the equivalent flow. Along with the use of a two-layer model for the boundary region and the concept of the analogy of transfer processes, this made it possible to form a mathematical model of the film, which considers all the components that determine the formation, movement, and heat transfer of the wall oil film. In addition, the model does not contain restrictions on the appearance of the parameters transverse profile, which are, for example, for the EWF model of the oil film in ANSYS FLUENT. The obtained results along with the previously developed air-droplet flow model in the core provide a complete two-dimensional model of the gas-liquid flow in the GTE bearing chamber, which allows the main geometric and all mode parameters to be used to determine the heat transfer coefficient to the inner wall of the chamber. Given the short calculation time, the proposed model allows for a detailed investigation of each factor’s contribution and element-by-element identification of the model based on the results of more detailed modeling and by comparing calculated and experimental data.

Numerical analysis of fluid type and flow mass rate on logarithmic temperature difference and heat transfer coefficient of double pipe heat exchanger

This CFD and statistical article aims to evaluate the impact of fluid type and flow mass rate on the log-mean temperature difference (ΔTLM) and the heat transfer coefficient (Ushell) in a double tube heat exchanger (DPHEX) using computational fluid dynamics (CFD) and statistical analysis. ANSYS Fluent software was utilized to conduct CFD calculations. CFD analyses were implemented using Taguchi L8 orthogonal array containing two variables such as the fluid types and the flow mass rates. The levels of fluid types were considered as water-liquid, ethylene-glycol, engine-oil, and benzene-liquid. The levels of fluid types were decided as 1.1 kg/s to 1.5 kg/s. To determine the optimal levels of variables and their impacts on the ΔTLM and Ushell in DPHEX, analysis of Signal to Noise (S/N) ratio was employed. Analysis of Variance (ANOVA) was also utilized to decide the effective variables and their percentage contribution rates on the outcomes. The CFD result obtained using the optimum levels of variables were compared with Taguchi estimation result. According to the study, the highest effects were obtained using ethylene-glycol, engine-oil, water-liquid, and benzene-liquid on the highest log-mean temperature difference values, respectively. In addition, the highest heat transfer coefficient values were found utilizing water-liquid, benzene-liquid, ethylene-glycol, and engine-oil, respectively. Increasing flow mass rate from 1.1 kg/s to 1.5 kg/s causes an increase in both outcomes. The study provides a reference for resolving issues that may arise in the production of experimental DPHEXs.

The Heat Transfer in Plate Fin Heat Exchanger for Adsorption Energy Storage: Theoretical Estimation and Experimental Verification of the Methodology for Heat Accumulation Process

Adsorption energy storage is a promising resource-saving technology that allows the rational use of alternative heat sources. One of the most important parts of the adsorption heat accumulator is the adsorber heat exchanger. The parameters of heat transfer in this unit determine how fast heat from an alternative energy source, such as the Sun, will be stored. For the design of adsorption heat accumulators, plate fin heat exchangers are mainly used. In this paper, the procedure for the estimation of the global heat transfer coefficient for the adsorber heat exchanger depending on its geometry is considered. The heat transfer coefficient for a LiCl/SiO2 sorbent flat layer under conditions of heat storage stage was measured. Based on these data, the global heat transfer coefficients for a number of industrial heat exchangers were theoretically estimated and experimentally measured for the adsorption cycle of daily heat storage. It was shown that theoretically obtained values are in good agreement with the values of the global heat transfer coefficients measured experimentally. Thus, the considered technique makes it possible to determine the most promising geometry of the plate fin heat exchanger for a given adsorption heat storage cycle without complicated experiments.

Synchronized measurement of instantaneous convective heat flux and velocity fields in wall-bounded flows

This work presents an experimental setup for acquiring synchronized wall and flow field measurements in a turbulent boundary layer (TBL). Instantaneous measurements of the convective heat transfer distribution at the wall and of the flow field are carried out simultaneously, using synchronized wall-parallel planar particle image velocimetry and infrared thermography. A low-thermal-inertia heated-thin-foil sensor is embedded in the wall beneath the TBL to measure the wall temperature maps with enough temporal resolution. The unsteady energy balance of the heated foil can be solved to restore the instantaneous value of the convective heat transfer coefficient on the wall. A detailed description of the sensor design is included. Furthermore, owing to the relatively low signal-to-noise ratio of instantaneous temperature fluctuation measurements, a recipe for data processing is proposed. A study to characterize the uncertainty of the experimental setup design is also performed. The overall agreement in the correlation between wall heat transfer and velocity fields with the literature supports the validity of the proposed approach. This solution is potentially interesting for flow control purposes, where sensing is performed at the wall.

Natural Convection in a Newtonian Nanoliquid-Saturated Porous Enclosure with Local Thermal Non-Equilibrium Effect

Buoyancy-driven convective flow and heat transfer characteristics in a Newtonian nanoliquid-saturated porous square enclosure are analyzed numerically using a local thermal non-equilibrium model. An enclosure’s horizontal walls are considered free–free and adiabatic, and the vertical walls are free–free isothermal boundaries. The dimensionless governing equations are solved using a central finite difference scheme with second-degree accuracy, and the results are in satisfactory agreement with the earlier works. The impact of various parameters on streamlines and isotherms is analyzed and depicted graphically. The effect of Darcy number, thermal Rayleigh number, and the ratio of thermal conductivities slow down the liquid flow. The temperature distribution is maximum at sidewalls and diminishes the amount of heat transport. The opposite phenomenon is observed for the solute Rayleigh number and interphase transfer coefficient of liquid-particle phases. For large values of interphase heat transfer coefficients, liquid-solid and liquid-particle are said to be in the local thermal equilibrium phase. The amount of heat transfer increases with an increasing interphase heat transfer coefficient and the ratio of the phases’ thermal conductivities. Results of local thermal equilibrium situation can be obtained as the particular case of the study. The amount of heat transfer is maximum in the local thermal non-equilibrium situation, and enhanced by 0.09% compared with the local thermal equilibrium situation. Heat transport is 0.74% less in the sparsely packed porous medium compared with the low-porosity medium.