Functional thermal fluids and their applications in battery thermal management:A comprehensive review

With the increasing requirements for fast charging and discharging,higher requirements have been put forward for the thermal management of power batteries.Therefore,there is an urgent need to develop efficient heat transfer fluids.As a new type of heat transfer fluids,functional thermal fluids mainly includ-ing nanofluids(NFs)and phase change fluids(PCFs),have the advantages of high heat carrying density,high heat transfer rate,and broad operational temperature range.However,challenges that hinder their practical applications remain.In this paper,we firstly overview the classification,thermophysical prop-erties,drawbacks,and corresponding modifications of functional thermal fluids.For NFs,the high ther-mal conductivity and high convective heat transfer performance were mainly elaborated,while the stability and viscosity issues were also analyzed.And then for PCFs,the high heat carrying density was mainly elaborated,while the problems of supercooling,stability,and viscosity were also analyzed.On this basis,the composite fluids combined NFs and PCFs technology,has been summarized.Furthermore,the thermal properties of traditional fluids,NFs,PCFs,and composite fluids are compared,which proves that functional thermal fluids are a good choice to replace traditional fluids as coolants.Then,battery thermal management system(BTMS)based on functional thermal fluids is summarized in detail,and the thermal management effects and pump consumption are compared with that of water-based BTMS.Finally,the current technical challenges that parameters optimization of functional thermal fluids and structures optimization of BTMS systematically are presented.In the future,it is necessary to pay more attention to using machine learning to predict thermophysical properties of functional thermal fluids and their applications for BTMS under actual vehicle conditions.

Effects of Potassium Ferrate and Low-Temperature Thermal Hydrolysis Co-Pretreatment on the Hydrolysis and Anaerobic Digestion Process of Waste Activated Sludge

This study evaluated the effect of potassium ferrate(PF)and low-temperature thermal hydrolysis co-pretreatment on the promotion of sludge hydrolysis process and the impact on acid production in the subsequent anaerobic digestion process.The analytical investigations showed that co-pretreatment significantly facilitated the hydrolysis process of the sludge and contributed to the accumulation of short-chain fatty acids(SCFAs).The pretreatment conditions under the optimal leaching of organic matter from sludge were hydrothermal temperature of 75℃,hydrothermal treatment time of 12 h,and PF dosage of 0.25 g g^(−1)TSS(total suspended solids),according to the results of orthogonal experiments.By pretreatment under proper conditions,the removal rate of soluble chemical oxygen demand(SCOD)achieved 71.8%at the end of fermentation and the removal rate of total phosphorus(TP)was 69.1%.The maximum yield of SCFAs was 750.3 mg L^(−1),7.45 times greater than that of the blank group.Based on the analysis of the anaerobic digestion mechanism,it was indicated that the co-pretreatment could destroy the floc structure on the sludge surface and improve organic matter dissolving,resulting in more soluble organic substances for the acidification process.Furthermore,microbial community research revealed that the main cause of enhanced SCFAs generation was an increase in acidogenic bacteria and a reduction of methanogenic bacteria.

Influences of Low-Temperature Hydrothermal Fluids on the Re-distributions and Occurrences of Associated Elements in Coal——A Case Study from the Late Permian Coals in the Zhijin Coalfield, Guizhou Province. Southern China

The occurrences of associated elements and their genetic factors in the No. 30 coal seam in the Zhijin Coalfield were studied using instrumental neutron activation analysis, inductively coupled plasma-atomic emission spectroscopy, and a scanning electron microscope equipped with an energy-dispersive X-ray analyzer. And, a microscope photometer system (Leitz MPV-Ⅲ) was used to observe the characteristics of coal petrology. According to the influence degree by the siliceous low-temperature hydrothermal fluids, the organic matter is divided into four types: A, B, C, and D of the hydrothermally-altered organic matter (HAOM). The study shows that the high content of Fe (2.31%) is not from pyrite, but mostly from the siliceous low-temperature hydrothermal fluids. The occurrences of the associated elements in the four organic matter types are different. The contents of Fe, Si, and Al are decreasing, but S and Cu are increasing in the order of the HAOM-A, HAOM-B, HAOM-C, and HAOM-D. The losing rate of sulfur in organic matter is 0.35% and the content of Fe taken from the low-temperature hydrothermal fluids into the organic matter is 0.794% during the siliceous low-temperature hydrothermal fluids invading the coal seam. The above facts indicate that the low-temperature hydrothermal fluids play a crucial role in the re-distributions and occurrences of associated elements in coal.

Analysis of influence of heat exchangerfouling on heat transfer performancebased on thermal fluid coupling

A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.

The Effects of Thermal Radiation and Viscous Dissipation on the Stagnation Point Flow of a Micropolar Fluid over a Permeable Stretching Sheet in the Presence of Porous Dissipation

In this paper,the effects of thermal radiation and viscous dissipation on the stagnation–point flow of a micropolar fluid over a permeable stretching sheet with suction and injection are analyzed and discussed.A suitable similarity transformation is used to convert the governing nonlinear partial differential equations into a system of nonlinear ordinary differential equations,which are then solved numerically by a fourth–order Runge–Kutta method.It is found that the linear fluid velocity decreases with the enhancement of the porosity,boundary,and suction parameters.Conversely,it increases with the micropolar and injection parameters.The angular velocity grows with the boundary,porosity,and suction parameters,whereas it is reduced if the micropolar and injection parameters become larger.It is concluded that the thermal boundary layer extension increases with the injection parameter and decreases with the suction parameter.

Numerical Analysis of the Mixed Flow of a Non-Newtonian Fluid over a Stretching Sheet with Thermal Radiation

A mathematical model is elaborated for the laminar flow of an Eyring-Powell fluid over a stretching sheet.The considered non-Newtonian fluid has Prandtl number larger than one.The effects of variable fluid properties and heat generation/absorption are also discussed.The balance equations for fluid flow are reduced to a set of ordinary differential equations through a similarity transformation and solved numerically using a Chebyshev spectral scheme.The effect of various parameters on the rate of heat transfer in the thermal boundary regime is investigated,i.e.,thermal conductivity,the heat generation/absorption ratio and the mixed convection parameter.Good agreement appears to exist between theoretical predictions and the existing published results.

Research progress and development direction of low-temperature drilling fluid for Antarctic region

By combing the characteristics of drilling in Antarctic region, performance requirements on drilling fluid for Antarctic low temperature conditions, and research progress of low temperature drilling fluid, current problems of the drilling fluid have been sorted out, and the development direction of the drilling fluid has been pointed out. Drilling in the Antarctic region mainly includes drilling in snow, ice and subglacial rock formations, and drilling in Antarctic low temperature conditions will face problems in four aspects:(1) low temperature and large temperature changes in the drilling area;(2) likely well leakage and drillstring-sticking in the snow layer, creep in the ice layer, ice chip gathering jamming in the warm ice layer, well wall collapse in the subglacial rock formations;(3) lack of infrastructure and difficulty in logistical support;(4) fragile environment and low carrying capacity. After years of development, progresses have been made on low-temperature drilling fluids for the Antarctic region. Low-temperature petroleum-based drilling fluid, ethanol/ethylene glycol-based drilling fluid, ester-based drilling fluid and silicone oil-based drilling fluid have been developed. However, these drilling fluids have problems such as insufficient low-temperature tolerance, low environmental performance and weak wellbore stability, etc. In order to meet the performance requirements of drilling fluid under low-temperature conditions in Antarctic region, the working mechanisms of low-temperature drilling fluid must be examined in depth;environment-friendly low-temperature base fluid of drilling fluid and related additives must be developed to prepare environmentally friendly low temperature drilling fluid systems;multi-functional integrated adjustment method for drilling fluid must be worked out to ensure well wall stability and improve cutting-carry capacity when drilling ice formations and ice-rock interlayers;and on-site support operation codes must be established to provide technical support for Antarctic drilling.

Computational fluid dynamics modeling of rapid pyrolysis of solid waste magnesium nitrate hydrate under different injection methods

This study developed a numerical model to efficiently treat solid waste magnesium nitrate hydrate through multi-step chemical reactions.The model simulates two-phase flow,heat,and mass transfer processes in a pyrolysis furnace to improve the decomposition rate of magnesium nitrate.The performance of multi-nozzle and single-nozzle injection methods was evaluated,and the effects of primary and secondary nozzle flow ratios,velocity ratios,and secondary nozzle inclination angles on the decomposition rate were investigated.Results indicate that multi-nozzle injection has a higher conversion efficiency and decomposition rate than single-nozzle injection,with a 10.3%higher conversion rate under the design parameters.The decomposition rate is primarily dependent on the average residence time of particles,which can be increased by decreasing flow rate and velocity ratios and increasing the inclination angle of secondary nozzles.The optimal parameters are injection flow ratio of 40%,injection velocity ratio of 0.6,and secondary nozzle inclination of 30°,corresponding to a maximum decomposition rate of 99.33%.

Numerical Solution for Thermal Elastohydrodynamic Lubrication of Line Contact with Couple Stress Fluid as Lubricant

In this paper,the detailed analysis of the influence of thermal and non-Newtonian aspects of lubricant(couple stress fluid)on EHL line contact as a function of slide-roll ratio is presented.The novel low complexity FAS(full approximation scheme),of the multigrid scheme,with Jacobi dipole and Gauss Seidel relaxation is used for the solution of coupled equations viz.modified Reynolds equation,film thickness equation and energy equation satisfying appropriate boundary conditions.The analysis reveals the combined influence of non-Newtonian,thermal and slide-roll ratio(of bearing moving with different speeds)on pressure,film thickness and pressure spike covering a wide range of physical parameters of interest.Results show that pressure spike is strongly influenced by thermal,slide-roll ratio and non-Newtonian character of lubricant with negligible effect on the overall pressure distribution.Also,the minimum film thickness is slightly altered and it increases with the increase in the couple stress parameter.These findings confirm the importance of non-Newtonian and thermal effects in the study of EHL.

THE GLOBAL EXISTENCE OF STRONG SOLUTIONS FOR A NON-ISOTHERMAL IDEAL GAS SYSTEM

We investigate the global existence of strong solutions to a non-isothermal ideal gas model derived from an energy variational approach.We first show the global wellposedness in the Sobolev space H^(2)(R^(3)) for solutions near equilibrium through iterated energy-type bounds and a continuity argument.We then prove the global well-posedness in the critical Besov space B^(3/2)_(2,1) by showing that the linearized operator is a contraction mapping under the right circumstances.

Comprehensive Examination of Solar Panel Design: A Focus on Thermal Dynamics

In the 21st century, the deployment of ground-based Solar Photovoltaic (PV) Modules has seen exponential growth, driven by increasing demands for green, clean, and renewable energy sources. However, their usage is constrained by certain limitations. Notably, the efficiency of solar PV modules on the ground peaks at a maximum of 25%, and there are concerns regarding their long-term reliability, with an expected lifespan of approximately 25 years without failures. This study focuses on analyzing the thermal efficiency of PV Modules. We have investigated the temperature profile of PV Modules under varying environmental conditions, such as air velocity and ambient temperature, utilizing Computational Fluid Dynamics (CFD). This analysis is crucial as the efficiency of PV Modules is significantly impacted by changes in the temperature differential relative to the environment. Furthermore, the study highlights the effect of airflow over solar panels on their temperature. It is found that a decrease in the temperature of the PV Module increases Open Circuit Voltage, underlining the importance of thermal management in optimizing solar panel performance.

Effect of Low-Temperature Thermal Oxidation on the Capillary Performance of Sintered Copper Powder Wicks

In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick.The forced flow method and infrared imaging method are used to test the permeability and capillary performance of the samples.The effects of different oxidation temperatures on the performance of capillary wick are investigated.The experimental results show that the wetting performance of the oxidized samples is significantly enhanced.With the increase of oxidation temperature,the permeability decreases.The capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary wick.However,the oxidation temperature needs to be adjusted to obtain the best capillary performance.The highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated ones.Comparisons with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer device.This study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.

Thermal Fluid-Solid Interaction Model and Experimental Validation for Hydrostatic Mechanical Face Seals

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction（TFSI）mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.

Effect of Thermal Buoyancy on Fluid Flow and Inclusion Motion in Tundish without Flow Control Devices——Part II :Inclusion Motion

Following up the fluid flow simulation in a 60 t tundish, the trajectories of inclusions in the 60 t tundish without flow control are simulated by considering the force balance between the drag force and the inertial buoyancy force. The Stochastic model yields more accurate inclusion motion than the non-Stochastic model due to including the effect of the turbulent fluctuation. The average residence time of inclusions decreases with increasing size. The thermal buoyancy favors inclusions removal especially the small inclusions. Using solute transport like the dye injection in water model and copper addition in the real steel tundish cannot accurately study the motion of the inclusions. In the simulation, more than 68% inclusions bigger than 10μm are removed to the top, and less than 32% enters the mold. The thermal buoyancy has little effect on the fraction of inclusions moved to the top of the inlet zone, and it mainly favors the removal of inclusions smaller than 100μm to the top surface of the outlet zone. For inclusions bigger than 100μm, the effect of thermal buoyancy on their motion can be ignored compared to the inertial buoyancy effect.

Numerical Calculation of Thermal Effect on Cavitation in Cryogenic Fluids

A key design issue related to the turbopump of the rocket engine is that cavitation occurs in cryogenic fluids when the fluid pressure is lower than the vapor pressure at a local thermodynamic state. Cavitation in cryogenic fluids generates substantial thermal effects and strong variations in fluid properties, which in turn alter the cavity characteristics. To date, fewer investigate the thermal effect on cavitation in cryogenic fluids clearly by the numerical methods due to the difficulty of the heat transfer in the phase change process. In order to study the thermal effect on cavitation in cryogenic fluid, computations are conducted around a 2D quarter caliber hydrofoil in liquid nitrogen and hydrogen respectively by implementing modified Merkle cavitation model, which accounts for the energy balance and variable thermodynamic properties of the fluid. The numerical results show that with the thermal effect, the vapour content in constant location decreases, the cavity becomes more porous and the interface becomes less distinct which shows increased spreading while getting shorter in length. In the cavity region, the temperature around the cavity depresses due to absorb the evaporation latent heat and the saturation pressure drops. When the vapour volume fraction is higher, the temperature depression and pressure depression becomes larger. It is also observed that a slight temperature rise is found above the reference fluid temperature at the cavity rear end attributed to the release of latent heat during the condensation process. When the fluid is operating close to its critical temperature, thermal effects on cavitation are more obviously in both the liquid nitrogen and hydrogen. The thermal effect on cavitation in liquid hydrogen is more distinctly compared with that in liquid nitrogen due to the density ratio, vapour pressure and other variable properties of the fluid. The investigation provides aid for the design of the cryogenic pump of the liquid rocket.

Effect of Thermal Buoyancy on Fluid Flow and Inclusion Motion in Tundish without Flow Control Devices——Part Ⅰ: Fluid Flow

The κ-ε two-equation model is used to simulate the fluid flow in the continuous casting tundish coupling with the effect of thermal buoyancy. The natural convection induced by the thermal buoyancy generates an upward flow pattern especially at the outlet zone, and has little effect on the fluid flow in the inlet zone. The maximum viscosity is 700 times larger than the laminar viscosity, which indicates the strong turbulent flow in the tundish. The maximum temperature difference in the whole tundish is 82 K. The temperature near the stopper rod and the short wall is obviously lower than that in the inlet zone. The existence of the stopper rod has a big effect on the fluid flow entering the SEN and the mold. All the characteristics of the tundish geometry should be considered to accurately simulate the fluid flow in the tundish.

Dual solutions in boundary layer flow of a moving fluid over a moving permeable surface in presence of prescribed surface temperature and thermal radiation

An analysis of the heat transfer for a boundary layer forced convective flow past a moving permeable flat surface parallel to a moving fluid is presented. Prescribed surface temperature at the boundary is considered, A thermal radiation term in the energy equation is considered. The similarity solutions for the problem are obtained and the reduced ordinary differential equations are solved numerically. To support the validity of the numerical results, a comparison is made with the available results for some particular cases of this study. Dual solutions exist when the surface and the fluid move in the opposite directions.

Heat transfer analysis in peristaltic flow of MHD Jeffrey fluid with variable thermal conductivity

The effect of an inclined magnetic field in the peristaltic flow of a Jeffrey fluid with variable thermal conductivity is discussed. The temperature dependent thermal conductivity of fluid in an asymmetric channel is taken into account. A dimensionless nonlinear system subject to a long wavelength and a low Reynolds number is solved. The explicit expressions of the stream function, the axial velocity, the pressure gradient, and the temperature are obtained. The effects of all physical parameters on peristaltic transport and heat transfer characteristics are observed from graphical illustrations. The behaviors of θ∈ [0, π/2] and θ∈ [π/2, π] on fluid flow and heat transfer are found to be opposite. Further, the size of trapped bolus is greater for the case of the inclined magnetic field （θ≠ π/2） than that for the case of the transverse magnetic field （θ = π/2）. The heat transfer coefficient decreases when the constant thermal conductivity （Newtonian） fluid is changed to the variable thermal conductivity （Jeffrey） fluid.

Three-dimensional stretched flow of Jeffrey fluid with variable thermal conductivity and thermal radiation

This article addresses the three-dimensional stretched flow of the Jeffrey fluid with thermal radiation. The thermal conductivity of the fluid varies linearly with respect to temperature. Computations are performed for the velocity and temperature fields. Graphs for the velocity and temperature are plotted to examine the behaviors with different parameters. Numerical values of the local Nusselt number are presented and discussed. The present results are compared with the existing limiting solutions, showing good agreement with each other.

MHD graphene-polydimethylsiloxane Maxwell nanofluid flow in a squeezing channel with thermal radiation effects

The magnetohydrodynamic (MHD) graphene-polydimethylsiloxane (PDMS) nanofluid flow between two squeezing parallel plates in the presence of thermal radiation effects is investigated. The energy efficiency of the system via the Bejan number is studied extensively. The governing partial differential equations are converted by using the similarity transformations into a set of coupled ordinary differential equations. The set of these converted equations is solved by using the differential transform method (DTM). The entropy generation in terms of the Bejan number, the coefficient of skin-friction, and the heat transfer rate is furthermore investigated under the effects of various physical parameters of interest. The present study shows that the Bejan number, the velocity and thermal profiles, and the rate of heat transfer decrease with a rise in the Deborah number De while the skin-friction coefficient increases. It is also observed that the entropy generation due to frictional forces is higher than that due to thermal effects. Thus, the study bears the potential application in powder technology as well as in biomedical engineering.