Fluid Temperature Distribution Research Articles

Numerical Study of Knocking Combustion in a Heavy-Duty Engine under Plateau Conditions

Diesel engine combustion becomes very rough and can lead even lead to deflagration under high altitude conditions, which is harmful to component durability. In this study, the effects of altitude on the main combustion characteristics—in-cylinder fluid flow, spray behavior, and pressure and temperature distribution—were analyzed with CFD. A numerical model was built on the CONVERGE platform and validated with the optical spray behavior and pressure trace measured by the test bench. The simulation results indicated that the decreases in compression pressure and temperature at 4.5 km led to an over 4 °CA longer ignition delay than those of 1 and 3 km. The combustion efficiency decreased from 90% to 47% when the combustion changed from normal combustion to knocking combustion due to severe spray impingement. The processes of end-gas ignition, sequential combustion, and pressure oscillation in knocking combustion were revealed by the numerical modeling results. These results indicate that super-knocking combustion exists in both spark-ignition (SI) engines and compression-ignition (CI) engines.

Effect of multiple forces on convective micropolar fluid flow in a permeable channel with stretching walls considering second order slip conditions

This paper is intended to study the impact of velocity and thermal slip boundary conditions of order two on MHD buoyancy driven radiative micro-polar fluid in a channel with permeable stretching walls. The governing equations are transformed and solved numerically. Convergence of the numerical results are tested with grid independence test and obtained results are validated by comparing with existing results. The influence of velocity and thermal slip of order two, suction or injection, vortex viscosity, micro-rotation, magnetic and thermal radiation parameters on fluid velocity, microrotation profiles and temperature distributions are discussed over the graphs and tables. It is worth mentioning that second- order velocity and thermal slips dominate the stretchable walls and influence the flow characteristics (axial velocity, micro-rotation and temperature) more prominently. The micro-rotation profile decreases at and increases at of the channel for the first slip. This study is useful in blood rheology and fibre spinning etc. and these findings are highly useful to enhance the effectiveness of catalytic reactors.

Local Thermal Nonequilibrium (LTNE) Modeling of a Partially Porous Channel With Spatial Variation in Biot Number

Abstract The local thermal nonequilibrium (LTNE) model has been used widely for analyzing heat transfer during internal flow through porous media, including when a channel is only partially filled with a porous medium. In such problems, the Biot number describes the rate of convective heat transfer between solid and fluid phases. While uniform Biot number models are commonly available, recent advances in functionally graded materials necessitate the analysis of spatially varying Biot number in such geometries. This paper presents LTNE-based heat transfer analysis for fully developed flow in a channel partially filled with porous medium and with spatially varying Biot number to describe solid-fluid interactions in the porous medium. Fully uncoupled ordinary differential equations for solid and fluid temperature distributions are derived under three different boundary condition models. Solid and fluid temperature fields are presented for a variety of Biot number distributions, including quadratically and periodically varying functions. An explanation of the nature of temperature distribution predictions for such problems is provided. For special cases, the results presented here are shown to reduce to past work on constant Biot number. This work improves the theoretical understanding of porous media heat transfer and facilitates the use of such theoretical models for functionally graded materials.

Effect of gas injection mass flow rates on the thermal behavior in a cryogenic fuel storage tank

Large scale using of liquid hydrogen and liquid oxygen on energy engineering, chemical engineering and petrochemical industries, bring a series of non-equilibrium thermal behaviors within fuel storage tanks. Accurate simulation on the thermal behavior in cryogenic fuel storage tanks is therefore a critical issue to improve the operation safety. In the present study, a 2-dimensional numerical model is developed to predict the active pressurization process and fluid thermal stratification in an aerospace fuel storage tank. Both external heat penetration and heat exchange occurring at the interface are accounted for in detail. The volume of fluid method is adopted to predict the thermal physical process with high-temperature gas injected into the tank. The effect of the gas injection mass flow rate on the tank pressure, the interface phase change, and the fluid temperature distribution are investigated respectively. Finally, some valuable conclusions are obtained. The present study may supply some technique references for the design of the pressurization system. • Tank pressurization and fluid temperature distribution are investigated. • The pressure rise rate increases with the gas injection mass flow rate. • Serious liquid evaporation occurs in the initial pressurization period. • Vapor condensation increases with time and gas injection mass rate. • The penetration depth of thermal capacity experiences increases with time.

Modeling and simulation of non-isothermal three-phase flow for accurate prediction in underbalanced drilling

The present study aims at investigating the effect of temperature variation due to heat transfer between the formation and drilling fluids considering influx from the reservoir in the underbalanced drilling condition. Gas-liquid-solid three-phase flow model considering transient thermal interaction with the formation was applied to simulate wellbore fluid to calculate the wellbore temperature and pressure and analyze the influence of different parameters on fluid pressure and temperature distribution in annulus. The results show that the non-isothermal three-phase flow model with thermal consideration gives more accurate prediction of bottom-hole pressure (BHP) compared to other models considering geothermal temperature. Viscous dissipation, the heat produced by friction between the rotating drilling-string and well wall and drill bit drilling, and influx of oil and gas from reservoir have significant impact on the distribution of fluid temperature in the wellbore, which in turn affects the BHP. Bottom-hole fluid temperature decreases with increasing liquid flow rate, circulation time, and specific heat of liquid and gas but it increases with increasing in gas flow rate. It was found that BHP is strongly depended on the gas and liquid flow rates but it has weak dependence on the circulation time and specific heat of liquid and gas. BHP increase with increasing liquid flow rate and decreases with increasing gas flow rate.

SORET AND DUFOUR EFFECTS ON MHD FLOW WITH HEAT AND MASS TRANSFER PAST AN EXPONENTIALLY STRETCHING SHEET

The current study aims to explore the impact of Soret and Dufour effects past a stretching surface with heat and mass transfer on MHD fluid flow including the effects of heat sink and radiation. Similarity transformations are employed to deduce the governing partial differential equations of flow, heat and mass transfer to system of nonlinear ODE’s. The equations together with boundary conditions so obtained are solved using numerical technique by employing Matlab’s solver bvp4c. The graph of fluid velocity, temperature and concentration distributions are obtained for different parameters for the deep analysis of the problem. It is observed that Soret and Dufour effects show notable contribution towards heat and mass transfer where the latter boosts the rate of mass transfer, and the former raises the heat transfer rate. The accuracy of the numerical solution is confirmed by comparing our results with the outcomes of previous work on stretching sheet and the results show good agreement.

Impact of Al2O3 in Electrically Conducting Mineral Oil-Based Maxwell Nanofluid: Application to the Petroleum Industry

Alumina nanoparticles (Al2O3) are one of the essential metal oxides and have a wide range of applications and unique physio-chemical features. Most notably, alumina has been shown to have thermal properties such as high thermal conductivity and a convective heat transfer coefficient. Therefore, this study is conducted to integrate the adsorption of Al2O3 in mineral oil-based Maxwell fluid. The ambitious goal of this study is to intensify the mechanical and thermal properties of a Maxwell fluid under heat flux boundary conditions. The novelty of the research is increased by introducing fractional derivatives to the Maxwell model. There are various distinct types of fractional derivative definitions, with the Caputo fractional derivative being one of the most predominantly applied. Therefore, the fractoinal-order derivatives are evaluated using the fractional Caputo derivative, and the integer-order derivatives are evaluated using the Crank–Nicolson method. The obtained results are graphically displayed to demonstrate how all governing parameters, such as nanoparticle volume fraction, relaxation time, fractional derivative, magnetic field, thermal radiation, and viscous dissipation, have a significant impact on fluid flow and temperature distribution.

Concentration-dependent viscosity effect on magnetonano peristaltic flow of Powell-Eyring fluid in a divergent-convergent channel

The viscosity of fluids has an essential role in blood circulation through veins and arteries. So, this paper focuses on the influences of dependent-viscosity on the peristaltic flow of Powell-Eyring fluid in a divergent-convergent channel. Viscosity is supposed to vary with the temperature and concentration fluid. A theoretical relation to the concentration-dependent viscosity is introduced mathematically for the Powell-Eyring nanofluid for the first time in our literature. The formulation of the model contains a highly nonlinear system of PDEs that converted to ODEs by physical assumptions to low Reynolds number and long wavelength. A semi-analytical solution was obtained in different theoretical cases of the divergent-convergent channel using the generalized differential transform method (GDTM). Results for velocity profile, temperature distribution, and concentration distribution as well as extra stress tensor profile versus various values flow parameters have been constructed. Results show that the variation parameters of viscosity α, and β can control with flow velocity at each part of channel wall making them improve/get better the blood circulation in veins (Circulatory system). Furthermore, the concentration-dependent viscosity parameter increases the temperature distribution of fluid while it declines the nanoparticle diameter of fluid.

Impact of the electromagnetic flow of an MHD Casson fluid over an oscillating porous plate

AbstractThis study deals with the effect of electric force and magnetohydrodynamics (MHD) of the transient state on natural convection flow past an oscillating vertical plate. In addition to this, thermal radiation and porous media are also examined in the Casson fluid flow. The Poisson‐Boltzmann equation is employed to show the electric potential character within the fluid region, which is put into a linear form by the implementation of Debye–Hückel linearization. It is possible to compute the precise solution to the governing equations using the Laplace transform approach. The expression of fluid velocity, fluid concentration, and temperature are exposed graphically, and numerical results for Nusselt and Sherwood numbers are also derived for vital pertinent flow constraints. Increasing electroosmosis parameters strongly boosts fluid velocity. The nonnegative values of the Helmholtz–Smoluchowski velocity highly induce the axial velocity and the negative value decelerates. With increasing radiation strength and Prandtl number, the fluid's temperature distribution diminishes. These more intricate electrokinetic rheological flows associated with electroosmotic separators, such as biomedical absorbers, are illuminated by these models.

Thermodynamic performance on the pressurized discharge process from a cryogenic fuel storage tank

Due to excellent performance, cryogenic propellants, such as liquid hydrogen and liquid oxygen, are widely used in aerospace engineering. However, low storage temperature and low kinetic viscosity bring a lot of technique issues for high efficient thermal management on cryogen. An actual cryogenic fuel storage tank is selected as the research object, and a two-dimensional axial symmetrical computational model is established to study the pressurized discharge process, by adopting the volume of fluid (VOF) model. Both external environment heat leakage and the heat exchange occurring between the liquid and vapor are considered. Compared to the experimental results, the relative error is limited in 20.0%. Based on the developed numerical model, the temperature variation and heat flux through the insulation and tank wall, the pressurized discharge performance and the fluid temperature distribution are analyzed. The results show that during the pressurized discharge process, the lowest temperature appears in the inner side of the foam, and the external heat invasion does not absolutely penetrate into the tank. The vapor mass experiences fluctuating variations, and the vapor is always in condensation. In the first 200s, the temperature of the outflow fluid keeps constant, and then increases gradually. Under the present initial setting, the violent boiling phenomenon does not form during the whole process. The present study is significant to the depth understanding on the pressurized discharge of cryogenic fuels. • The lowest temperature appears in the inner surface of the foam with high-temperature gas occupied. • The external heat invasion does not penetrate into the tank during pressurized discharge. • The vapor is condensed by the subcooled liquid, and its mass experiences fluctuating variations. • The outflow pressure is higher than the saturated pressure, and the violent boiling does not form.

Influence of fluid flows on electric double layers in evaporating colloidal sessile droplets.

A model is developed for describing the transport of charged colloidal particles in an evaporating sessile droplet on the electrified metal substrate in the presence of a solvent flow. The model takes into account the electric charge of colloidal particles and small ions produced by electrolytic dissociation of the active groups on the colloidal particles and solvent molecules. We employ a system of self-consistent Poisson and Nernst-Planck equations for electric potential and average concentrations of colloidal particles and ions with the appropriate boundary conditions. The fluid dynamics, temperature distribution and evaporation process are described with the Navier-Stokes equations, equations of heat conduction and vapor diffusion in air, respectively. The developed model is used to carry out a first-principles numerical simulation of charged silica colloidal particle transport in an evaporating aqueous droplet. We find that electric double layers can be destroyed by a sufficiently strong fluid flow.

Effect of geological stratification on estimated accuracy of ground thermal parameters in thermal response test

The ground thermal properties are the basic parameters for the design of borehole heat exchanger (BHE) in ground–coupled heat pump system (GCHPs), and their accuracy directly affects the economy and reliability of the heat pump system. In traditional design, ground is usually regarded as an isotropic homogeneous medium, and its thermal properties are obtained by solving the inverse heat transfer problem in BHE through in-situ thermal response test (TRT). In fact, different geological layers can be observed along the depth of BHE, and thermal physical properties of each layer are different based on the ground geological conditions. In order to investigate the effect of geological stratification on estimated accuracy of ground thermal parameters in TRT, a validated numerical layered BHE model (NLBM) is presented to simulated TRT, and the fluid temperature response is used to estimate effective ground thermal conductivity and borehole thermal resistance based on line source model (LSM). Secondly, the distributions of fluid temperature in U-pipe and heat flux of BHE along the depth are compared and analyzed based on the NLBM and the numerical homogeneous BHE model (NHBM). At last, borehole thermal resistance from the NLBM and estimated borehole thermal resistance from LSM are compared. The results show the maximum heat flux in the 3rd layer of the NLBM is 21.1% higher than that of NHBM, and the minimum heat flux in the 1st layer is reduced by 46.9% in the 100 h duration. The estimated λLSM using the fluid temperature responses in the NLBM is 1.3% higher than the thickness-weighted thermal conductivity in the NLBM. The minimum relative error between RLSM and Rb is still up to 10.45% in the duration of 100 h even though extending the duration is helpful to improve the estimated accuracy of RLSM.

The Influence of Baffle Inclination on Fluid Flow and Temperature Distribution of HPH Heat Exchanger

High Pressure Heater is one of the heat exchanger type shell and tube in the plant consisting of a shell on the outside and a tube on the inside where the temperature of a fluid in the shell is different from the temperature inside the tube, resulting in heat transfer between fluid flows. The use of baffle inclination on the shell side serves to direct the fluid flow so that the flow occurs turbulence that can affect the temperature distribution on the shell side. This study aimed to determine the influence of baffle inclination angle on temperature distribution and fluid flow. The results showed that using variations in the angle of baffle inclination can increase the outlet temperature value and the higher temperature at a 20° variation in baffle inclination angle of 349.74 K, the pressure on the shell side decreases at each variation lowest value of 793.19 pa at 0° variation of baffle inclination and the velocity value produced is higher with the increasing angle of the baffle. Given the variation in baffle angle, the change in value in the high-pressure heater is caused by turbulence caused by baffle inclination on the shell side.

Study of Local Structural Changes on Air Cooling at the End of Rotor Windings for Variable Speed Pumped Storage Generator-Motor

The shrink fit retaining ring is currently the easiest to install and the most widely used end fixed for structure AC excitation variable speed generator-motor rotor end windings. However, the current research on the effect of high strength sealing on the ventilation and heat dissipation performance of the end is not enough. In this paper, based on the actual structural parameters and periodic symmetry simplification, the three-dimensional coupled calculation model of fluid field and temperature field is established. After solving the fluid and thermal equations, the influence of the length of rotor support block, the height of rotor support block, and the number of rotor support block on the fluid flow and temperature distribution in the rotor end region of generator-motor is studied using the finite volume method. The rheological characteristics of the air in the rotor domain, such as velocity and inter-winding flow, are analyzed. The law of temperature variation with local structure in the computational domain is studied. The variation law of cooling medium performance inside the large variable speed power generator motor is revealed.

Numerical Analysis of Conjugated Heat and Mass Transfer of Helical Hollow Fiber Membrane Tube Bank for Seawater Distillation

A numerical study on the conjugated heat-mass transfer of helical hollow fiber membrane tube bank (HFMTB) for seawater desalination was carried out. Physical and mathematical models of fluid flow, temperature and humidity distribution were constructed to investigate the influences of flow type, Reynolds number, and temperature on the conjugated heat-mass transfer performance of hollow fibers in the distillation membrane module. The conjugated heat-mass transfer characteristics of HFMTB were discussed by utilizing the friction coefficient, Nusselt number (Nu), and Sherwood number (Sh). Results demonstrate that a distillation efficiency enhancement of 29% compared to the straight HFMTB has been detected for four-helical HFMTB configuration, though the friction coefficient of such a module is about 4 times of their straight counterparts. The values of average Nu and Sh numbers are increasing with tube number, which improves distillation efficiency. The effect of flow type has been studied by employing the upstream and downstream flows to the double-helical HFMTB, demonstrating upstream flow type is more conducive to the heat-mass transfer process. Both the outlet air humidity (ω) and distillation efficiency (η) decrease with the air-side Reynolds number (Rea) and inlet air temperature in the helical HFMTB while increasing with the solution-side Reynolds number (ReS) and inlet solution temperature. Overall, the obtained results indicate that helical HFMTB applying upstream flow has great potential to achieve high-performance SGMD for seawater desalination. It is anticipated that the present work can assist in a better understanding of the membrane desalination process in HFMTB and thus provide theoretical suggestions for further optimization and development.

INVESTIGATION OF THE HEAT PERFORMANCE FOR SQUEEZED HYBRID NANOFLUID FLOW BETWEEN PARALLEL DISKS EMBEDDED IN POROUS MEDIUM WITH THERMAL RADIATION

This study's primary contribution determines the heat transfer performance and flow characteristics of a hybrid nanofluid between two parallel disks. The squeezing aspects of the hybrid nanofluid are investigated considering when the plates shift apart and come together. The impacts of thermal radiation and suction/injection are further investigated. Also, the Darcy-Forchheimer model is used for porous medium. The mathematical formulation for the transport of momentum and heat is portrayed by a partial differential equation set, which is then diagnosed by embracing a fourth-order exactness program (Bvp4c). Graphical findings expose the importance of miscellaneous arising parameters on the velocity, temperature, and local Nusselt numbers. The dominant value of porosity constraint and magnetic parameter reduces the temperature distribution of fluid. Furthermore, increased squeeze number causes the temperature profile to exhibit contrary behavior. Hybrid nanofluid gives notable enhancement in heat transfer rate compared to nanofluid.

Development of a two-dimensional mathematical model of flow boiling heat transfer in micro- and minichannels

The paper concerns flow boiling heat transfer in micro- and minichannels. In the mathematical model, the steady state heat transfer process in a single asymmetrically heated minichannel was considered. Calculations with the use of Trefftz functions were based on the data from own experiments. The temperature of the heater and the refrigerant were assumed to satisfy the Laplace equations and the energy equation respectively. The problem was solved by the Trefftz method using two sets of Trefftz functions. The known heater and refrigerant temperature distributions were used to determine the heat transfer coefficient at the heater – refrigerant contact. To verify the proposed mathematical model, data from experiments were applied to calculations. The essential part of the experimental stand was the test section which comprises a minichannel heat sink. The heated element for Fluorinert FC-72 flowing along minichannels was a thin foil. The temperature of its outer side was measured using infrared thermography. Thermocouples and pressure transducers installed at the inlet and outlet of the test section monitored fluid temperature and pressure. Mass flow rate, the current supplied to the heater and the voltage drop were also recorded. The resulting graphs presented thermograms of measured temperature on outer surface of the heater, temperature distributions of fluid temperature and local values of the heat transfer coefficient.

Effect of shear-thinning behavior on fluid temperature distribution mixed by single rotor

Effect of shear-thinning behavior on fluid temperature distribution mixed by single rotor

Numerical analysis of natural convection behavior in density stratification induced by external cooling of a containment vessel

It is essential to improve computational fluid dynamics (CFD) analysis accuracy to estimate thermal flow in a containment vessel during a severe accident. Previous studies pointed out the importance of the initial and boundary conditions on the analysis. The purpose of this study is to evaluate the influence of initial and boundary conditions by numerical analysis of natural convection experiments. A density stratification layer was initially formed, and natural convection was induced by the external cooling of the vessel. Mixing by natural convection eroded the density stratification. We applied the RANS model with dynamic turbulent Schmidt number model. We used the measured temperature and gas concentration as the boundary and initial conditions. The erosion velocity did not change much with the initial gas distribution. The temperature boundary condition of small internal structures significantly influenced the fluid temperature distribution, and we evaluated this influence of the small internal structure quantitatively.

Validation of analytical model and identification of salt effect on wellbore temperature in underbalanced drilling

Understanding the behavior of the borehole temperature recovery process, which influences drilling operations, requires an adequate estimation of fluid temperature. The presence of salt in a saline formation changes the composition of the annular fluid and has a significant impact on the fluid temperature distribution during drilling operations. As a result, while drilling a saline formation, it is vital to examine the key parameter that determines an accurate estimate of fluid temperature. Using python software and statistical quantitative methods, this study proposes a simplified user-friendly computational system that analyzes the drilling fluid systems performance evaluation and selection optimization.The fluid temperature distribution of X Field in China was analyzed using Shan mathematical model as a base model. When compared to MWD data from the field, the model predicted the temperature distribution of the field with less than 10% error. An adjustment factor was introduced to the base model to accommodate for changes in annular fluid composition while drilling a saline formation. The findings show that salt concentration has an impact on fluid temperature distribution during drilling. The fluid temperature at the wellbore condition changes by at least 7% with both high and low adjustment factors. Because the salt in the formation inflow dissolves in the drilling fluid near the annulus, the rheology of the fluid combination changes.