An efficient thermal management system is desirable for improving the performance of key components of electric vehicle (EV), such as battery packs and insulated-gate bipolar transistors (IGBTs). This paper investigates the application of single bubble nucleate boiling heat transfer in battery and IGBT component cooling pack. A semi-mechanistic flow boiling model, which combines four main submodels i.e., phase change model, micro-region model, Marangoni model, and contact angle model, is developed to get the insight of various subprocesses like bubble inception, growth, departure, scavenging effect while the bubble departs, and condensation. For model validation, simulations are carried out for single bubble flow boiling in a vertical rectangular channel and compared against the experimental data available in the literature. Thereafter, simulations are carried out for the battery and IGBT cooling pack to understand the physical phenomena associated with nucleate boiling in such systems. The choice of a single vapor bubble vis-à-vis multiple bubbles has been based on the objective of validating the developed numerical model. An enhancement of ∼30% in heat transfer is achieved for both battery and IGBT components when the system is subjected to a nucleate boiling cooling regime as compared to a conventional single-phase convection cooling system. Nusselt number variation due to the single bubble movement along the coolant path is studied in detail for both serpentine-shaped cooling path in a battery and straight flow path in an IGBT. Moreover, the influence of Reynolds number over bubble dynamics is analyzed.

Specific heat is a vital characteristic of nanofluids. The present work is an experimental assessment for the isobaric specific heat measurements for the Al 2 O 3 nanoparticle dispersed in a base fluid of different mixture ratio of ethylene glycol and water at 30, 40, 50, and 60 vol%. The experiments were conducted over temperature range from 35 to 105 °C with nanoparticle concentrations of 0.5 to 2.5 vol%. The results indicated that the specific heat of nanofluid decreases as the nanoparticle volume increases and EG ratio increases but increases as the temperature increases. This characteristic demonstrates that the use of nanofluids should be at as high temperature as possible to fulfill a good beneficial effect. A new correlation from the measurements with maximum deviation of 2.2% was found to estimate the specific heat for these nanofluids.

Electromagnetic high-temperature therapy is popular in medical engineering treatments for various diseases include tissue damage ablation repair, hyperthermia and oncological illness diagnosis. The simulation of transport phenomena in such applications requires multi-physical models featuring magnetohydrodynamics, biorheology, heat transfer and deformable porous media. Motivated by investigating the fluid dynamics and thermodynamic optimization of such processes, in the present article a mathematical model is developed to study the combined influence of thermal buoyancy, magnetic field and thermal radiation on the fluid and heat characteristics in electrically-conducting viscoelastic biofluid flow through a vertical deformable porous medium. Jefferys elastic-viscous model is deployed to simulate non-Newtonian characteristics of the biofluid. It is assumed that heat is generated within the fluid by both viscous and Darcy (porous matrix) dissipations. The boundary value problem is normalized with appropriate transformations. The non-dimensional biofluid velocity, solid displacement and temperature equations with appropriate boundary conditions are solved computationally using a spectral method. Verification of accuracy is conducted via monitoring residuals of the solutions and Validated with shooting technique is included. The effects of Jeffrey viscoelastic parameter, viscous drag parameter, magnetic field parameter, radiation parameter and buoyancy parameter on flow velocity, solid displacement, temperature and entropy generation are depicted graphically and interpreted at length. Increasing magnetic field and drag parameters are found to reduce the field velocity, solid displacement, temperature and entropy production. Higher magnitudes of thermal radiation parameter retard the flow and decrease Nusselt number whereas they elevate solid displacement.

The authors regret in the published paper referenced above and agree with the discussion by Pantokratoras (2019, “Discussion: “Computational Analysis for Mixed Convective Flows of Viscous Fluids With Nanoparticles” (Farooq, U., Lu, D. C., Ahmed, S., and Ramzan, M., 2019, ASME J. Therm. Sci. Eng. Appl., 11(2), p. 021013 ),” ASME J. Therm. Sci. Eng. Appl., 11(5), p. 055503). In this Closure, the non-similar mathematical model is developed to describe the mixed convective nanofluid flow over vertical sheet which is stretching at an exponential rate. In the published article referenced above, similarity transformations are utilized to convert the governing nonlinear partial differential equations (PDEs) into ordinary differential equations (ODEs). The important physical numbers such as magnetic field (M 2 ), Brownian motion parameter (N b ), thermophoresis (N t ), Eckert number (Ec), ratio of mass transfer Grashof to heat transfer Grashof (N), buoyancy parameter (λ), and Reynolds number (Re) appearing in the dimensionless ODEs are still functions of coordinate “x”; therefore, the problem is non-similar. In this corrigendum, the non-similar model is developed by using ξ(x) as non-similarity variable and η(x, y) as pseudo-similarity variable. The dimensionless non-similar model is numerically simulated by employing local non-similarity via bvp4c. The graphical results show no change in behavior. The important thermal and mass transport quantities such as Nusselt number and Sherwood number have been computed for the non-similar model, and results are compared with the published article.

Multiple water jets and a cross air flow are used to cool a mold segment in a homogeneous and automated manner. The test segment was cooled from an initial temperature of 573 K. An average temperature difference of less than 3 K and a maximum temperature difference of less than 6 K were obtained along the length of the surface of the test segment during the entire duration of the cooling process as opposed to the traditional channel cooling approach where the mean and maximum temperature differences increase over time. The top surface of the test segment represents the mold/part interface which is of interest in this study. Using model predictive control (MPC) and a data-driven predictive model, the cooling speed of the test segment’s top surface was able to be maintained within ±5 K of the cooling ramp imposed. The results were compared to the results obtained when using a simpler On/Off algorithm for automated cooling. Compared to the simpler On/Off algorithm, there was an improvement in the accuracy of the cooling ramp with respect to its reference value of over 30% for most cooling ramps tested (5–25 K/min). A parametric study on the influence of the flowrates of the fluids on the cooling speed of the test segment’s surface was also conducted.

Numerical investigation has been carried out to compare the heat transfer performance and fluid flow behavior of microchannel heat sinks with circular and rhombus pin fins which are arranged in an in-line manner. Diameter and sides are 1 mm for circular and rhombus fins. Three-dimensional (3D) computational domain has been simulated using two types of cooling medium, i.e., water and Al 2 O 3 –H 2 O nanofluid. A comprehensive comparative analysis has been presented considering the coolants and pin fin profiles as variable parameters. Two operating variables, i.e., heat flux (q) and Reynolds number (Re), are varied in the range of q = 100–400 kW/m 2 and Re = 100–400. A total of 64 cases have been simulated to identify the promising features of both the pin fins attributed to improved heat transfer and overall thermal performance. Comparison has also been made between the coolant medium to find out their heat dissipation potential and flow characteristics in the heat sink. Results obtained in terms of average bottom wall temperature, heat transfer coefficient, Nusselt number (Nu), and pressure drop demonstrate that heat sink with rhombus pin fins dissipates more heat compared to its counterpart. It is attributed to the shape and geometry of rhombus fins that facilitate distinct fluid flow behavior; nevertheless, the pressure drop is less in the circular fin heat sink. Moreover, for constant value of Re, nanofluid extracts more heat compared to water in both configurations of the heat sink.

The field of rotating packed bed (RPB) and its applications in the transfer processes are multidisciplinary in nature. Achievement of significant volume reduction by employing the RPB in distillation towers has been fairly established in the mass transfer domain. Nevertheless, the prospect of RPB in the heat transfer domain still remains dormant. The current work addresses this very issue by exploring the characteristics of thermal transactions across the novel RPB device. This study succinctly presents the related aspects with multi-phase flow of participating fluids in the counter-current direction across the porous, rotating packed bed structure. However, the simultaneous involvement of these multivariate intrinsic attributes makes the understanding of the transfer phenomenon quite complex upon viewing from the experimental perspective alone. Hence, computational fluid dynamics (CFD) tool has been used for assimilation of the physical understanding of the thermal transactions along with the effects of operating parameters. The thermal contours, main effect and surface plots for heat transfer rate directly contribute towards better appreciation of the thermal transaction mechanism and could be employed for suitable volume reduction in heat exchanger devices.

Natural convection cooling of an electronic component in an electronic device using water-based Fe 3 O 4 magnetic nanofluids is studied under the presence of the magnetic field. The heated vertical electronic component in an enclosure type electronic device with a magnetic field source is used as a model for the study. Different samples of Fe 3 O 4 -water nanofluid are prepared using different surfactants and the stability of those samples are estimated using visualization and zeta potential technique. Thermal properties of the stable sample of magnetic nanofluid are precisely measured. The experimentally measured properties are used for further theoretical study. The natural convection is characterized in terms of the relative position of the magnetic source and the electronic component, the strength of the magnetic field, and the magnetization of the nanofluids. Nine different combinations of the position of the magnetic source and the electronic component have been compared with the case in which there is an absence of the magnetic field. The dimensionless number used in this investigation are Rayleigh number (10 3 ≤ Ra ≤ 10 6 ), magnetic numbers (Mn = 100, 500, and 1000), and Hartmann Number (0 ≤ Ha ≤ 100). The position of the magnetic source with respect to the electronic component significantly affects the rate of heat transfer. The effect is more pronounced when the magnetic source is placed below any of the two vertical walls of the enclosure. The fluid flow is observed distorted near the magnetic source when the Ha is increased. The increment in the magnetic number strengthens the flow, which leads to the enhanced heat transfer rate.

Due to the exhaustion of fossil fuels and environmental degradation, biodiesel has attracted much attention as a new energy source. Currently, microwave reactors are used extensively for producing biodiesel. However, nonuniform heating of producing biodiesel in microwave reactors is a major problem. In order to solve the problem, a microwave reactor with an interlayer which can obviously improve the uniformity of microwave heating was designed. In this work, the heating efficiency and heating uniformity of the reactor were discussed from two aspects of waveguide position and interlayer thickness by means of multi-physical coupling calculation. According to the calculation results, the optimization model of a microwave reactor with an interlayer was obtained. Then, based on the above optimization model of a microwave reactor with an interlayer, a stirrer that can improve the heat transfer of the fluid material was introduced. The Maxwell equation, heat transfer equation and flow equation were coupled by multi-physical field simulation method to explore the influence of different factors of stirrer on power consumption and heating uniformity. Through response surface analysis, it was found that the primary and secondary order of stirring factors affecting microwave heating uniformity was stirring speed > impeller diameter > bottom clearance, and there was an interaction between different factors. From the two aspects of stirring power consumption and heating uniformity, the best stirring effect was obtained.

The helically coiled tubes (HCTs) have been attracting huge attention for enhancing the heat transfer of supercritical fluids and improving energy efficiency. Moreover, the new refrigerant R1234ze(E) has excellent environmental properties and system performance, but few researches have been concentrated on the supercritical R1234ze(E) heat transfer. In this work, the shear stress transport (SST) turbulence model is adopted for the numerical simulation of the cooling heat transfer performance of s-R1234ze(E) in horizontal HCT. The influences of heat flux, mass flux, coil pitch, and tube radius on the heat transfer coefficient, gravitational buoyancy effect, and centrifugal buoyancy effect are, respectively, investigated. Furthermore, the results reveal heat transfer oscillation occurs when R i g * | cos β | max > 0.17 , and the oscillation mechanism is analyzed. Different from that in the vertical HCT, the angle between the radial component of gravitational buoyancy and centrifugal force varies continuously in the horizontal helical tube, resulting in the fluid with lower temperature may locate in the inner-left region or the inner-right region. Subsequently, the heat transfer piecewise correlation for supercritical R1234ze(E) in horizontal HCT is developed. The average absolute deviation of the predicted results is 5.88%.

This paper presents a steady-state heat transfer model for the natural convection of mixed Newtonian-Non-Newtonian (Alumina-water) and pure non-Newtonian (Alumina-0.5 wt% Carboxymethyl Cellulose (CMC)/water) nanofluids in a square enclosure with adiabatic horizontal walls and isothermal vertical walls, the left wall being hot and the right wall cold. In the first case, the nanofluid changes its Newtonian character to non-Newtonian past 2.78% volume fraction of the nanoparticles. In the second case, the base fluid itself is non-Newtonian and the nanofluid behaves as a pure non-Newtonian fluid. The power-law viscosity model has been adopted for the non-Newtonian nanofluids. A finite-difference based numerical study with the Stream function-Vorticity-Temperature formulation has been carried out. The homogeneous flow model has been used for modeling the nanofluids. The present results have been extensively validated with earlier works. In Case I, the results indicate that Alumina-water nanofluid shows 4% enhancement in heat transfer at 2.78% nanoparticle concentration. Following that there is a sharp decline in heat transfer with respect to that in base fluid for nanoparticle volume fractions equal to and greater than 3%. In Case II, Alumina-CMC/water nanofluid shows 17% deterioration in heat transfer with respect to that in base fluid at 1.5% nanoparticle concentration. An enhancement in heat transfer is observed for increase in hot wall temperature at a fixed volume fraction of nanoparticles, for both types of nanofluid.

This experimental test investigates the effect of filling ratio (FR) and inclination angle on the thermal performance of a nanoengineered copper-water heat pipe. A hydrophilic copper oxide coating (CuO) is synthesized and integrated on the inner wall of the evaporation section of the heat pipe. The heat pipe is fabricated from an inner grooved copper pipe with dimensions of 12.7 mm outer diameter, 11 mm inner diameter, and 440 mm length. Ultra-filtered de-ionized (DI) water is used as a working fluid. Four different FRs of DI water 3%, 5%, 10%, and 15% are investigated to determine the optimum configuration. All samples are tested at various inclination angles and working loads. Experimental results show that the optimum filling ratio is the 5% FR, which was indicated by the lowest thermal resistance of 0.019 K/W.

This paper presents a numerical investigation on heat transfer and flow behavior for non-Newtonian nanofluids with different nanoparticles (Al 2 O 3 and CuO) and carboxymethyl cellulose (CMC) with water as a base fluid. The analysis has been carried out in an elliptical tube. Power-law model is adopted to depict the non-Newtonian nature of nanofluid. The present study has been done with a range of nanosized particles 0–4% by volume, and the variation of Reynolds number is kept under the laminar condition. The physical model covers two concentric tubes used to create an annular space. The effects of volume fraction, particle type, and base fluid have been investigated at different Reynolds numbers numerically. Also, the effect of pressure and heat transfer coefficient on the flow behavior of non-Newtonian nanofluids is analyzed. The results concluded that Al 2 O 3 particles showed 219% and CuO particles give 195% higher heat transfer coefficient as compared with pure water.

Experiments were conducted to evaluate the thermal entropy generation, frictional entropy generation, and exergy efficiency of reduced graphene oxide (rGO)–Fe 3 O 4 –TiO 2 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.

Recently, the development trend of multi-module and multi-function in electronic microsystems makes the ever-increasing heat flux problem more serious. In this study, a highly efficient integrated single-phase microchannel cooler with four heat sources is presented for handling the challenges from both workings independently of all electronic modules and the high heat flux. Both numerical and experimental studies are conducted. By optimizing the structural design and the fabricated process, the presented microchannel cooler has outstanding cooling performance, which contains desired fluid flow distribution, pressure drop, heat transfer, and combination thereof. Results reveal uniform coolant flow dissipates four individual heaters independently, and their maximal temperature difference below 4 °C. Beyond this, high heat flux removal (707.6 W/cm 2 ) is realized with an extremely low coolant flowrate (45 ml/min), and the maximum temperature rise is less than 60 °C. This study provides a referable solution for the thermal management of multi-module heat sources and high heat flux in compact electronic microsystems.

In this research work, heat and mass transport and radiated, two-dimensional, steady, incompressible nanofluid flow of non-Newtonian material (Carreau fluid) over a stretchable moving surface of sheet is examined. The flow is saturated through Darcy-Forchheimer porous medium and generated by stretching phenomenon. Furthermore, magnetodydrodynamics (MHD), mixed convection, heat generation/absorption, nonlinear thermal radiation, thermophoresis diffusion, activation energy, Brownian motion, and chemical reaction effects are accounted to develop the governing expressions, i.e., momentum, energy, and concentration for the considered flow problem. The governing equations are first altered into nonlinear ordinary differential equations with the help of appropriate similarity variables and then computational results are computed by Built-in-Shooting technique via mathematica . The salient aspects of sundry variables are discussed graphically on the velocity field, skin friction coefficient, temperature profile, Nusselt number, concentration field, and Sherwood number. Outcomes illustrate that the velocity field and temperature profile have contrast behavior against higher values of magnetic parameter. Also, the engineering quantities are discussed numerically with the help of important flow variables and the results are demonstrated through tables.

This study presents a thermal performance comparison of various working fluids operating in a parabolic trough collector. Fluids such as gases (helium, carbon dioxide, and air), liquid sodium, and liquids (pressurized water, Therminol VP1, and Syltherm 800) are evaluated. This study also examines the efficiency enhancement obtained from the dispersion of copper nanoparticles in water, Therminol VP1, and Syltherm 800 base fluids. The optimum parameters for nanoparticle concentration, volume flowrate, and inlet temperature to obtain the maximum efficiencies for each working fluid were evaluated in this study. The thermal model used in this study was modeled after the commercially available LS-2 collector, which is designed in the engineering equation solver (EES) and validated with results found in the literature. The results of the study show that the Cu/Syltherm 800 nanofluid showed the most enhancement in thermal efficiency with 0.141%, while Cu/water and Cu/Therminol VP1 had enhancements of 0.037% and 0.088% respectively.

Three-dimensional numerical study is presented in this work that deals with thermo-hydrodynamic and entropy generation analysis of water-based nanofluids in recharging microchannel (RMC). Four different water-based nanofluids (Al 2 O 3 , CuO, SiO 2 , and ZnO) are considered with volume concentrations of 1–5% and nanoparticle diameters of 10–50 nm to understand their effect on thermo-hydrodynamic performance and entropy generation. Substrate bottom surface is subjected to a constant wall heat flux of 100 W/cm 2 while coolant with Reynolds number range of 100–500 flows through the RMC. It is revealed that among all the nanofluids under investigation, water/Al 2 O 3 provides enhanced thermal performance with higher effectiveness parameter (η), and it also shows reduced entropy generation. With increasing volume concentration of water/Al 2 O 3 nanofluid, heat transfer coefficient increases, effectiveness parameter increases, and entropy generation reduces. Water/Al 2 O 3 nanofluid with smaller nanoparticle diameter shows enhanced heat transfer coefficient and reduced entropy generation, whereas it shows decreased effectiveness parameter. This is attributed to increased pressure drop with decreasing particle diameter. This study suggests that an optimized combination of particle diameter and volume concentration should be chosen for using nanofluid-based coolants for high heat flux removal.

Little is known on the three-dimensional flow of a couple stress Casson fluid conveying nanoparticles when the significance of Lorentz force, chaotic gesture of those minute particles, and thermophoresis are significant. The intent of this investigation is to focus on the flow of such fluid along a horizontal surface due to dual stretching and internal heating. A zero nanoparticle mass flux condition is employed at the surface, which specifies that the nanoparticles’ fraction is submissively measured. The dimensional nonlinear equations are reduced into a system of coupled nonlinear ordinary differential equations by employing scaling analysis and later they are solved numerically. The results are discussed graphically for various emerged physical parameters through different plots. The results in the absence of stretching ratio factor indicate that the heat absorption parameter and Prandtl number accelerate the heat transfer rate. The temperature of the non-Newtonian couple stress fluid is found to be higher than that of viscous case. It may be suggested that the Casson couple stress nanofluid can be substituted for the corresponding viscous fluid in industrial applications for greater heat transfer. The outcomes are closely matched with the studies available in the literature as a limiting case.

Steady-state and transient behaviors of single-phase natural circulation loop (SPNCL) are investigated using four thermal oils (Therminol VP1, Paratherm CR, Dowtherm A, and Dowtherm Q) and water-based ternary hybrid (various combinations of different nature and shaped nanoparticles: Al 2 O 3 , Cu, carbon nanotube (CNT) and graphene) nanofluids as loop fluid. The influences of nanoparticle volume concentration and loop height-to-width ratio on the mass flow rate and total entropy generation rate of SPNCL are investigated. Results disclose that ternary hybrid nanofluids enhance flow initiation, reduce fluctuation and are expected to attain a steady-state faster than water. Steady-state mass flow rate increases/decreases for ternary hybrid nanofluid depending on the shape of the nanoparticle, and the total entropy generation rate decreases as compared to water. Thermal oil shows a higher mass flow rate and total entropy generation rate as compared to water. Al 2 O 3 –Cu–CNT–water and Paratherm CR show the best result among all ternary hybrid nanofluids and thermal oils, respectively. The nanoparticle shape decides the optimum nanoparticle volume fraction. Increasing the height-to-width ratio decreases the total entropy generation and upsurges the mass flow rate at specified input power. The optimum height-to-width ratio depends on the loop fluid.