Thermal Entropy Research Articles

Natural convection and entropy generation of Ag-water nanofluid in a finned horizontal annulus: A particular focus on the impact of fin numbers

In this work, numerical investigation of the natural convection and entropy generation characteristics of biological Ag-water nanofluid in a horizontal annulus having fins attached to the inner cylinder is aimed. The impacts of nanoparticle volume concentration (φ = 0, 0.1, 0.5 and 1%), Rayleigh number (Ra = 103, 104 and 105), and number of fins (n = 0, 2, 4 and 8) on the flow structure, temperature distribution, average Nusselt number (Nu) as well as on the thermal, frictional and total entropy generation rates are examined comprehensively. The computational outcomes indicate that the fin attachment and the increment of its number significantly improve Nu up to 35.50%, while the entropy generation rate sourced by heat transfer significantly increases up to 39.07% accordingly, compared to the finless annulus. The frictional entropy generation is remarkably decreased at low Ra by the increment of the number of fins, nevertheless, it is notably increased at high Ra. Besides, the inclusion of nanoparticles significantly contributes to the augmentation of Nu, being attained up to around 30% with a volume fraction of φ = 1%, whereas it significantly increases both thermal and frictional entropy generation rates, which can respectively reach up to 30.25 and 77.60% at the same volume fraction in the finless annulus.

Quantum phases and thermodynamics of a frustrated spin-1/2 ladder with alternate Ising–Heisenberg rung interactions

We study a frustrated two-leg spin ladder with alternate isotropic Heisenberg and Ising rung exchange interactions, whereas, interactions along legs and diagonals are Ising-type. All the interactions in the ladder are anti-ferromagnetic in nature and induce frustration in the system. This model shows four interesting quantum phases: (i) stripe rung ferromagnetic (SRFM), (ii) stripe rung ferromagnetic with edge singlet (SRFM-E), (iii) anisotropic antiferromagnetic (AAFM), and (iv) stripe leg ferromagnetic (SLFM) phase. We construct a quantum phase diagram for this model and show that in stripe rung ferromagnet (SRFM), the same type of sublattice spins (either isotropic S-type or discrete anisotropic σ-type spins) are aligned in the same direction. Whereas, in anisotropic antiferromagnetic phase, both S and σ-type of spins are anti-ferromagnetically aligned with each other, two nearest S spins along the rung form an anisotropic singlet bond whereas two nearest σ spins form an Ising bond. In large Heisenberg rung exchange interaction limit, spins on each leg are ferromagnetically aligned, but spins on different legs are anti-ferromagnetically aligned. The thermodynamic quantities like specific heat C v (T), magnetic susceptibility χ(T) and thermal entropy S(T) are also calculated using the transfer matrix method for various phases. The magnetic gap in the SRFM and the SLFM can be noticed from χ(T) and C v (T) curves.

Performance optimization of a nanofluid-based photovoltaic thermal system integrated with nano-enhanced phase change material

In this study, a nanofluid-based photovoltaic thermal system integrated with nano-enhanced phase change material is numerically simulated using a transient three-dimensional model. Aluminum oxide nanoparticles are dispersed into both the heat transfer fluid, which is water, and the Rubitherm series of organic phase change material. Response surface methodology is applied to gain a predictive model for estimating the behavior of the system in terms of four different design parameters of phase change material layer thickness, heat transfer fluid mass flow rate, and the mass fraction of nanoparticles through the phase change material and working fluid. The relationships between the mentioned parameters and responses, including electrical and thermal power, exergy, and entropy generation along with their interaction impacts on system performance are obtained. Finally, employing single and multi-objective optimization, different scenarios are defined to optimize the system based on the designer’s goals. The results reveal that the dispersion of nanoparticles within the heat transfer fluid leads to a better improvement in photovoltaic thermal system performance compared to its addition to the phase change material. Based on the multi-objective optimization method to maximize electrical and thermal exergies, simultaneously, results show the best electrical and thermal exergies of the system can be achieved to 135.92 and 2.44 W/m2, respectively.

Electronic band structure, mechanical and thermodynamic properties of Erbium chalcogenides ErX (X = S, Se and Te): A computational insight

We have investigated the structural, electronic, magnetic, mechanical, and thermodynamic properties of Erbium chalcogenides, ErX (X = S, Se and Te) using a suitable density functional theory (DFT) approach. ErX compounds were found stable in NaCl-type structure and in the ferromagnetic phase. The electronic band structure diagrams showed metallic nature of the ErX compounds in both the majority and minority spin channels. Higher value of the bulk modulus for ErS showed high stiffness resistance as compare to other two members. The calculated total magnetic moments were found to be 2.18 μB, 2.17 μB, and 2.22 μB for ErS, ErSe and ErTe compounds, respectively. The major contribution in the magnetic moment was found due to f -electrons of Er. The elastic and mechanical properties have also been computed. The calculated values of bulk modulus to shear modulus (B/G) and Cauchy pressure indicated their brittle nature. As per the Zener anisotropy factor, these materials were also found to be elastically anisotropic. The thermodynamic constants including the bulk modulus, specific heat at constant volume, thermal expansion coefficient, entropy and Debye were calculated for ErX compounds for the first time.

An assessment of the mathematical model for estimating of entropy optimized viscous fluid flow towards a rotating cone surface

Entropy optimization in convective viscous fluids flow due to a rotating cone is explored. Heat expression with heat source/sink and dissipation is considered. Irreversibility with binary chemical reaction is also deliberated. Nonlinear system is reduced to ODEs by suitable variables. Newton built in shooting procedure is adopted for numerical solution. Salient features velocity filed, Bejan number, entropy rate, concentration and temperature are deliberated. Numerical outcomes for velocity gradient and mass and heat transfer rates are displayed through tables. Assessments between the current and previous published outcomes are in an excellent agreement. It is noted that velocity and temperature show contrasting behavior for larger variable viscosity parameter. Entropy rate and Bejan number have reverse effect against viscosity variable. For rising values of thermal conductivity variable both Bejan number and entropy optimization have similar effect.

Structural, optoelectronic and thermodynamic characteristic of orthorhombic SnZrCH3(CH=S, Se) compounds: Insights from DFT computations

In this research work, a study on the structural, optoelectronic, and thermodynamics propertiesof the SnZrCH3 (CH = S, Se) compounds is presented. The study is performed by the “full potential linearized augmented plane wave plus local orbitals (FP-(LAPW + lo)) method framed within density functional theory (DFT). To treat with exchange-correlation energy/potential, different approximations; local density approximation (LDA), generalized approximation (GGA) by Wu and Cohen (WC) named as (WC-GGA) are used toestimate structural properties such as lattice constants, bulk moduli,and related results of pressure derivative.Besides that Engel Vosko's approach of GGA named as (EV-GGA) and Becke-Johnson modified form of exchange-correlation potential (mBJ-GGA) is also used to obtain reliable results of the electronic and optical properties. Our calculations of electronic band structures and density of states endorse both compounds of indirect bandgapnature withbandgap energy 1.054 eV and 0.531 eV for SnZrS3 and SnZrSe3, respectively at the level ofmBJ-GGA. Our calculations of the optical absorption parameters show the highest values of absorption coefficients in the ultraviolet (UV) region, attributed to localized Zirconium states lying in the lower region of the conduction band. Hence, our findings show that both SnZrS3 and SnZrSe3 compounds are potential candidates for photovoltaic applications.Moreover, the pressure effects on the lattice constants, heat capacities, thermal expansion coefficients, entropy, and Debye temperature are also explored using the quasi-harmonic Debye model.

Study of non – Newtonian flow, heat transfer and entropy generation characteristics in trapezoidal corrugated channel

This study is focused on the thermo-hydraulic and entropy generation characteristics of a non-Newtonian fluid in a trapezoidal shaped wavy channel. The study has been conducted for different Reynolds number ranging from 25 – 100 and power law index varying from 0.5 – 1.5. The variation of average Nusselt number, pressure drop, thermal entropy generation, viscous entropy generation are being calculated. For the discretization of the governing equations, finite volume method is adopted in Ansys Fluent. Average Nusselt number value increases with an increase in the value of Reynolds number and decreases with an increase in power law index. On the other hand, pressure drop decreases on increasing the value of Reynolds number, whereas on increasing the value of power law index, pressure drop value showing a decreasing trend. Thermal entropy generation and viscous entropy generation follows almost the same trend but both having different order of magnitude. The trend shows that on increasing the value of Re both the entropy generations increases whereas on increasing the power law index, it decreases.

A comparative study of effect of heater orientation on flow and heat transfer characteristics in buoyancy driven flow in cryogenic liquid

The present study aims to analyse the buoyancy driven fluid flow and heat transfer characteristics using different heater orientation in liquid nitrogen for cooling superconductor. For this purpose, a localized circular heater (analogous to superconductor) generating heat at constant rate submerged in liquid nitrogen enclosure is analysed. The study is performed with two orientations of heater; one is vertical and another is horizontal. The entropy generation associated with heat transfer and fluid flow is also discussed in the present study. The Rayleigh number, average Nusselt number, maximum vertical velocity, entropy generation and Bejan number are used as comparing parameters for two orientations of heater. Under same heat generation rate, Rayleigh number is comparatively higher for vertically oriented heater whereas average Nusselt number is comparatively higher for horizontally oriented heater. The maximum vertical velocity of fluid is higher when heater is vertically oriented. The horizontally oriented heater has comparatively less value of thermal entropy generation than vertically oriented heater but horizontally oriented heater has higher value of fluid friction irreversibility. In summary, horizontally oriented heater has comparatively higher value of total entropy generation than vertically oriented heater. Bejan number is higher for horizontally oriented heater. In overall study, the value of Bejan number is less than 0.5; therefore, it can be said that fluid friction irreversibility is more dominated than heat transfer irreversibility.

A machine learning approach to the prediction of transport and thermodynamic processes in multiphysics systems - heat transfer in a hybrid nanofluid flow in porous media

Comprehensive analyses of transport phenomena and thermodynamics of complex multiphysics systems are laborious and computationally intensive. Yet, such analyses are often required during the design of thermal and process equipment. As a remedy, this paper puts forward a novel approach to the prediction of transport behaviours of multiphysics systems, offering significant reductions in the computational time and cost. This is based on machine learning techniques that utilize the data generated by computational fluid dynamics for training purposes. The physical system under investigation includes a stagnation-point flow of a hybrid nanofluid (Cu−Al2O3/Water) over a blunt object embedded in porous media. The problem further involves mixed convection, entropy generation, local thermal non-equilibrium and non-linear thermal radiation within the porous medium. The SVR (Support Machine Vector) model is employed to approximate velocity, temperature, Nusselt number and shear-stress as well as entropy generation and Bejan number functions. Further, PSO meta-heuristic algorithm is applied to propose correlations for Nusselt number and shear stress. The effects of Nusselt number, temperature fields and shear stress on the surface of the blunt-body as well as thermal and frictional entropy generation are analysed over a wide range of parameters. Further, it is shown that the generated correlations allow a quantitative evaluation of the contribution of a large number of variables to Nusselt number and shear stress. This makes the combined computational and artificial intelligence (AI) approach most suitable for design purposes.

Numerical modeling of entropy production in Al2O3/H2O nanofluid flowing through a novel Bessel-like converging pipe

Optimization of thermal systems requires higher heat transfer rate and lower entropy production rate. The review of literature shows that there are limited works on entropy production rate of nanofluids flowing through a converging pipe as the available ones only considered entropy production rate in a linear converging pipe. In this study, a 2D-computational fluid dynamic model is set up to investigate entropy production rate of Al2O3 nanofluid flowing through novel Bessel-like convergent pipes in laminar flow regime. The effect of Reynolds number $$\left( {300 \le {\text{Re}} \le 1200} \right)$$ , nanoparticle concentration $$\left( {0 \le \varphi \le 0.1} \right)$$ , and convergent index $$\left( {n = 0 - 3} \right)$$ on the entropy production rate, heat transfer effectiveness number, and irreversibility distribution ratio were considered. The results obtained revealed that increase in convergent index enhances viscous entropy production rate, but diminishes thermal entropy production rate. For instance, the reduction in thermal entropy production rate at $${\text{Re}} = 900$$ between pipe corresponds to $$n = 0$$ and $$n = 3$$ was 51.98% while the increase in viscous entropy production rate was 753.65%. Furthermore, a new correlation was developed using response surface methodology to estimate the entropy production rate as a function of the Reynolds number, nanoparticle concentration, and convergence index. The overall result shows that the usage of converging pipe in place of straight pipe is more advantageous.

Metamagnetoelectric transitions-enhanced multicaloric effect in multiferroics A2Cu2Mo3O12 (A=Rb and Cs) quantum spin chain

The multicaloric properties of multiferroic A 2 Cu 2 Mo 3 O 12 (A = Rb and Cs) compounds are theoretically investigated through a frustrated one-dimensional spin ribbon chain of CuO 2 . The system submitted to external magnetic and electric field constraints grants the particular interest of metamagnetoelectric effect arising at relatively low temperatures. The isentropes of Rb 2 Cu 2 Mo 3 O 12 and Cs 2 Cu 2 Mo 3 O 12 exhibit about four major sharper dips by lowering temperature. This highlights four meta-transitions points which in turn are simultaneously metamagnetic and metaelectric, and therefore conveniently treated as metamagnetoelectric transitions. In the vicinities of the metamagnetoelectric transitions and in the quantum critical region, the thermal entropies are relatively large, which thus results in metamagnetoelectric transitions-enhanced multicaloric effect. Furthermore, this enhancement appears in the cooling process where the adiabatic magnetic and electric cooling rates diverge in the vicinity of the metamagnetoelectric transition points indicating the prominent low-temperature multicaloric effect. It is then certain that by making use of such large magnetoelectric coupling at metamagnetoelectric transition regions, the refrigerating efficiency of multiferroic materials will be further improved. • The multicaloric properties of multiferroic A 2 Cu 2 Mo 3 O 12 (A = Rb and Cs) compounds are theoretically investigated. • The system submitted to external magnetic and electric field constraints exhibits the metamagnetoelectric effect. • The metamagnetoelectric transitions increase the thermal entropy, leading to an enhancement of the multicaloric effect. • The adiabatic cooling rates at the metamagnetoelectric transitions emphasize prominent low-temperature multicaloric effect.

Radiative thermal criticality and entropy generation of hydromagnetic reactive Powell-Eyring fluid in saturated porous media with variable conductivity

Theoretical study of inherent irreversibility and thermal runaway of an exothermic reactive Eyring-Powell fluid flow through a saturated porous fixed horizontal channel with thermal radiation and variable electrical conductivity is investigated. The reactive conducting fluid under bimolecular chemical rate law is propelled by pressure gradient. Ignoring the material assumptions, the governing dimensionless equations of the flow model are solved using semi discretization finite difference techniques coupled with weighted residual method. The results in terms of flow rate, temperature, thermal runaway, Bejan number and entropy generation are presented in graphical form. From the results, it is observed that parameter which argument the entropy production rate also enhances the Bejan number. Also, minimization of entropy generation is achieved at low values of thermal radiation, dissipation rate, electric field loading and viscosity variables.

Embedding multiple conical vanes inside a circular porous channel filled by two-phase nanofluid to improve thermal performance considering entropy generation

In the present work, thermal performance and entropy generation of two-phase nanofluid in a circular channel equipped with multiple conical vanes filled by porous material are studied. The vanes used in the present study are designed to be able to connect to an electric motor and can rotate (as a feature). However, in this study, only the static case of the vanes is studied. It was shown that the use of the above design can lead to increased heat transfer with an appropriate pressure drop. At a constant pumping power or when there is a limit on the flow rate, the use of the vane design can lead to more heat transfer. It is, therefore, energy-saving and can be used as a viable option for energy storage. The thermal performance illustrates that in the non-porous case, the best PEC occurs for the six rows of vanes, and for the porous case, the best PEC cases occur for three rows and six rows of vanes in Da = 10−3. At maximum flow velocity and minimum permeability, the highest entropy generation is observed, which is affected by thermal entropy generation. Increasing the number of conical branches leads to increased entropy generation. The results show that a 100-fold reduction in permeability can increase heat transfer by up to 8%, while a three-fold increase in Reynolds number can improve heat transfer by more than 100%.

Combined thermal and moisture convection and entropy generation in an inclined rectangular enclosure partially saturated with porous wall: Nonlinear effects with Soret and Dufour numbers

An analysis of thermosolutal convection and entropy generation considering Soret and Dufour effects inside an inclined rectangular enclosure attached with porous wall has been investigated. The physical parameters are in the ranges such as buoyancy ratio (-10 ≤ N ≤ 10), permeability (10−9 ≤ Da ≤ 10−1) and thickness (0 ≤ d ≤ 1.0) of porous wall, enclosure inclination angle (0° ≤ Φ ≤ 90°), Soret number (0 ≤ Sr ≤ 1.5) and Dufour number (0 ≤ Du ≤ 1.5). Heatlines and masslines taking Soret and Dufour effects into account are obtained as effective tools that visualizes the heat and species transported paths. Results demonstrate that Soret number has mild impact on heat transfer rate and promotes moisture transportation, while increasing Dufour number could boot heat transfer rate and reduce moisture transfer rate. Furthermore, increasing Soret numbers enhances entropy generation induced by heat transfer and fluid friction, while entropy generation induced by fluid friction, heat and moisture transfer is dropped with stronger Dufour effect. Present work can benefit the heat and moisture transfer performance and entropy generation minimization of thermal storage wall system.

Numerical and artificial neural network modeling study on the first-law and second-law performance of a novel helical heat sink filled with water–silver nanofluid

This paper is devoted to studying the first-law and second-law performances of a novel helical heat sink (HS). The biologically synthesized water–Ag nanofluid is considered as the coolant. The impacts of volume concentration of nanoparticles ( $$\varphi$$ ), Reynolds number ( $$\mathrm{Re}$$ ) and geometrical parameters of HS on the hydrothermal aspects and irreversibility behavior of HS are evaluated, and their optimal values are found. It was noted that the intensification of both the $$\varphi$$ and $$\mathrm{Re}$$ causes an augmentation in the convection coefficient, average CPU temperature and maximum CPU temperature, while the thermal resistance diminishes by rising $$\varphi$$ and $$\mathrm{Re}$$ . In addition, the fluid friction and heat transfer irreversibilities growth by intensifying the $$\mathrm{Re}$$ diminished with the increment of $$\varphi$$ . Furthermore, the outcomes showed that the best first-law performance of the HS occurs at $$\varphi =1\%$$ and $$\mathrm{Re}=1500$$ , while the lowest irreversibility occurs at $$\varphi =1\%$$ and $$\mathrm{Re}=500$$ . Finally, the obtained numerical data were utilized to develop a predictive model for convective heat transfer coefficient, thermal entropy generation rate and frictional entropy generation rate. The accuracy of the models was evaluated based on three statistical indices including mean relative error percentage (MRE), root mean square error (RMSE) and coefficient of determination (R2). It was found that the $${R}^{2}$$ value for all the developed models is higher than 0.99.

Heat Transfer and Second Law Analysis of Ethylene Glycol-Based Ternary Hybrid Nanofluid Under Laminar Flow

Abstract Experiments were conducted to evaluate the thermal entropy generation, frictional entropy generation, and exergy efficiency of reduced graphene oxide (rGO)–Fe3O4–TiO2 hybrid nanofluid flow in a circular tube under laminar flow. The ternary nanoparticles were synthesized using the sol–gel technique and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The stable ethylene glycol-based ternary hybrid nanofluid was prepared and its thermophysical properties, heat transfer, friction factor, and pumping power at various values of particle weight concentrations (0.05–0.2%) and Reynolds number (211–2200) were studied experimentally. Nusselt number, heat transfer coefficient, friction factor, and exergy efficiency augment with increasing values of particle loading and Reynolds number. Results show the thermal conductivity and viscosity increase, as compared to the base fluid, by 10.6% and 108.3% at ψ = 0.2% and 60 °C. Similarly, for ψ = 0.2% and Reynolds number of 1548, and in comparison to the base fluid data, the Nusselt number and heat transfer coefficient enhancement are 17.78% and 24.76%, respectively, the thermal entropy generation reduction is 19.85%, and the exergy efficiency enhancement is 6.23%. At Reynolds number of 221.1, the rise in pressure drop, pumping power, and friction factor is 13.65%, 11.33%, and 16%, respectively, for ψ = 0.2% as compared to the base fluid data. The overall thermal performance of the system is enhanced by 14.32%. New equations are developed for the evaluation of the thermophysical properties, Nusselt number, and friction factor.

Elemental composition, heat capacity from 2 to 300 K and derived thermodynamic functions of 5 microorganism species

Detailed elemental analysis and low-temperature calorimetric measurement results are reported for the first time for Gram-positive bacteria, Gram-negative bacteria and mold fungi. Microorganism unit carbon formulas (empirical formulas) were calculated. Standard molar heat capacity and entropy were found to be C⁰p,m = 38.200 J/C-mol K and S⁰m = 31.234 J/C-mol K for Escherichia coli, C⁰p,m = 54.188 J/C-mol K and S⁰m = 47.141 J/C-mol K for Gluconobacter oxydans, C⁰p,m = 31.475 J/C-mol K and S⁰m = 33.222 J/C-mol K for Pseudomonas fluorescens, C⁰p,m = 38.118 J/C-mol K and S⁰m = 37.042 J/C-mol K for Streptococcus thermophilus, and C⁰p,m = 35.470 J/C-mol K and S⁰m = 34.393 J/C-mol K for Penicillium chrysogenum. Microorganism heat capacities below 10 K were best described by an expanded Debye-T³ law. Based on the collected data, empirical formulas and entropies per C-mole of the analyzed organisms were determined. The measured heat capacities were compared to predictions of Kopp’s rule and Hurst-Harrison equation, both of which were found to be able to give reasonably accurate predictions. The determined entropies were compared to predictions of Battley and Roels models. The Battley model was found to be more accurate. The measured microorganism entropies lay between the values of their principal macromolecular constituents: DNA, and globular and fibrillar proteins. This indicates that self-assembly of the macromolecular components into cellular structures does not lead to decrease in thermal entropy.

An entropy production analysis for electroosmotic flow and convective heat transfer: a numerical investigation

In the current numerical study, an entropy production analysis is conducted for the electroosmotic flow and convective heat transfer in the microduct. A number of blades are installed inside the system to create the swirl flow and enhance the heat and mass transfer. The results obtained by this investigation are compared with those achieved by other studies to verify the precision of the numerical procedures employed. The length, position, and number of conductive blades, and the electric field intensity are considered as the input parameters. The frictional, thermal, and diffusion types of entropy production are considered as the output parameters. The results show that the frictional entropy production increases, while the thermal entropy production decreases as more number of conductive blades is installed in the system. The amount of diffusion entropy production is very small. In addition by increasing the blade length from 15 to 35 µm, the average velocity in the system increases and accordingly, the frictional entropy production increases up to 140.3% and the thermal entropy production diminishes about 71.2%. By relocating the conductive plate from x = 500 µm to x = 2000 µm toward the outlet section of the system, the frictional entropy production is reduced about 84.4% and the thermal entropy production is boosted up to 261.1%. Increasing the external field strength causes an increase in the frictional entropy production and a decrease in the thermal entropy production.

Entropy Analysis on a Three-Dimensional Wavy Flow of Eyring–Powell Nanofluid: A Comparative Study

The thermal management of a system needs an accurate and efficient measurement of exergy. For optimal performance, entropy should be minimized. This study explores the enhancement of the thermal exchange and entropy in the stream of Eyring–Powell fluid comprising nanoparticles saturating the vertical oriented dual cylindrical domain with uniform thermal conductivity and viscous dissipation effects. A symmetrical sine wave over the walls is used to induce the flow. The mathematical treatment for the conservation laws are described by a set of PDEs, which are, later on, converted to ordinary differential equations by homotopy deformations and then evaluated on the Mathematica software tool. The expression of the pressure rise term has been handled numerically by using numerical integration by Mathematica through the algorithm of the Newton–Cotes formula. The impact of the various factors on velocity, heat, entropy profile, and the Bejan number are elaborated pictorially and tabularly. The entropy generation is enhanced with the variation of viscous dissipation but reduced in the case of the concentration parameter, but viscous dissipation reveals opposite findings for the Newtonian fluid. From the abovementioned detailed discussion, it can be concluded that Eyring–Powell shows the difference in behavior in the entropy generation and in the presence of nanoparticles due to the significant dissipation effects, and also, it travels faster than the viscous fluid. A comparison between the Eyring-Powell and Newtonian fluid are also made for each pertinent parameter through special cases. This study may be applicable for cancer therapy in biomedicine by nanofluid characteristics in various drugs considered as a non-Newtonian fluid.

Experimental study on heat transfer, friction factor, entropy and exergy efficiency analyses of a corrugated plate heat exchanger using Ni/water nanofluids

In the present study, the heat transfer, entropy, friction factor, exergy efficiency, pumping power, and performance index ratio of nickel/water nanofluids flow in a corrugated plate heat exchanger are investigated experimentally. The nickel nanoparticles were synthesized using the chemical precipitation method and characterized by various techniques. The stable water based nickel nanofluids were prepared with particle volume concentrations of 0.1%, 0.3%, and 0.6%. The experiments were conducted at nanofluids Reynolds numbers ranged from 300 to 1000. The properties of nickel nanofluid are evaluated experimentally as well. The thermal conductivity and viscosity enhancements are 33.92%, and 67.45% at a temperature of 60 °C compared to the base fluid data. The increase of nanoparticle loadings and Reynolds number leads to an augmentation of the overall heat transfer coefficient, heat transfer coefficient, and Nusselt number. The overall heat transfer coefficient, convective heat transfer, and Nusselt number enhanced by 38.60%, 57.35%, and 42.68% at 0.6 vol % of nanofluid and a Reynolds number of 707, respectively compared to water data. The thermal entropy generation is decreased by 15.70%, while frictional entropy generation and pumping power are increased by 68.29% and 61.77%, respectively at 0.6 vol % of nanofluid and a Reynolds number of 707 against water data. The exergy efficiency was enhanced by 42.27% at 0.6 vol % of nanofluid and a Reynolds number of 303 compared to water data. The performance index ratio is decreased with the use of nanofluids due to the increase of viscosity, friction factor, pressure drop, and pumping power.