Variable Fluid Research Articles

Analyzing the effects of variable fluid properties on radiative dissipative hybrid nanofluid over moving wedge with MHD and Joule heating

Understanding and optimizing heat transfer processes in complex fluid systems is the driving force behind studying the magnetohydrodynamic (MHD) flow of [Formula: see text]–[Formula: see text] nanofluid across a radiative moving wedge, taking into account the impacts of viscous dissipation and Joule heating. Nanofluids, such as [Formula: see text]–[Formula: see text], increase heat transmission and thermal efficiency. However, the complicated challenges caused by fluid characteristics and radiative heating need a thorough investigation. This study examines MHD hybrid nanofluid heat transfer via a permeable wedge using joule heating, mass suction, viscous dissipation, variable viscosity, thermal radiation, variable thermal conductivity, and variable Prandtl number. We use similarity transformation to solve the ordinary differential equations that follow from the governing partial differential equations. We then check the results for correctness and dependability. To ensure the reliability and validity of the outcomes, source parameters are crucial to the validation process. The consequence of changing these parameters on the heat transmission properties of the MHD hybrid nanofluid is studied for both the scenario without and with thermal radiation by methodically analyzing the percentage increase or reduction. The validation process also includes a comparison of the computed values, such as the heat transfer rate and skin friction factor, with established theoretical predictions. This examination guarantees that the numerical solution, executed using the bvp4c technique in MATLAB, corresponds to the anticipated physical behavior of the system being studied. In addition, the findings exist using both graphical and tabular forms, which allows for a clear and succinct illustration of how different physical limitations affect flow characteristics.

Modeling saline-fluid flow through subglacial channels

Abstract. Subglacial hydrological systems impact ice dynamics, biological environments, and sediment transport. Previous numerical models of channelized subglacial flow have focused on freshwater in temperate ice without considering variable fluid chemistry and properties. Saline fluids can exist in cold glacier systems where freshwater cannot, making the routing of these fluids critical for understanding their influence on geochemical and physical processes in relevant glacial environments. This study advances previous efforts by modeling saline fluid in cold glacier systems, where variable fluid chemistry significantly influences melt rates and drainage processes. We model the drainage of a hypersaline subglacial lake through an ice-walled channel, highlighting the impact of salinity on channel evolution. The model results show that, in subglacial systems at salinity-dependent melting points, channel walls grow more slowly when fluids have higher salt concentrations, leading to significantly lower discharge rates. At higher salinities, more energy is required to warm the fluid to the new melting point as the brine is diluted, which reduces the energy available for melting the channel walls. We also highlight the impact of increased fluid density on subglacial drainage and the importance of accounting for accurate suspended sediment concentrations when modeling outburst floods. This model provides a framework to assess the impact of fluid chemistry and properties on the spatial and temporal variations of fluid flux.

Insight into thermal dynamic of stagnated flow of MHD Jeffery fluid when the joule heating, viscous dissipation and Soret effect are present: A multistep Milne's approach

The purpose of this work is to use the RK approach in conjunction with Milne's Predictor Corrector method to investigate the numerical solution of the magnetohydrodynamic Jeffery fluid passing over the upper horizontal parabolic surface. Milne's predictor-corrector methodology is highly important since it increases result accuracy when compared to either approach alone. The physical aspects are investigated by using the variable fluid properties, and consider the stagnation point and boundary layer flow of the MHD Jeffery fluid, which flows on the upper horizontal parabolic surface. The influence of Jeffery fluid flowing the paraboloid surface is ascertained by measuring the velocity slip and melting surface effects. We examined both the heat and mass transfer rates with the effects of viscous dissipation, Joule heating, heat source/sink, activation energy, and the Soret effect because these rates are important in chemical reactions, electronic devices, climate change, separation and distillation processes, and water and air pollution. The governing equations in the form of PDEs are obtained by implementing all of the assumptions on the fundamental conservation laws. These equations are then converted into ODEs by using the similarity variables. The "Milne's Predictor-Corrector Method" is a numerical strategy used to solve numerical problems and the results are analyzed both graphically and numerically manners with this numerical technique. Analysis is done on the graphical behavior of many parameters on the temperature, concentration, and velocity regions. The numerical findings of skin friction and Nusselt number are also presented here, and the outcomes are compared with the results of the BVP5c and Milne's (Predictor-Corrector) methods. The obtained results indicated that the motion (velocity) of Jeffery fluid is restricted by the enhancement in Deborah number, retardation to relaxation parameter, Hartmann number, and viscosity parameter, whereas augmentation happens in fluid velocity due to melting parameter and stretching ratio parameter. The temperature region can be increased by the source of the viscosity parameter, Hartmann number, heat source/sink parameters, and Eckert number. The decline in the concentration distribution is noted due to activation energy and the reaction rate parameter, while an upsurge in concentration occurs due to the Soret number.

Tangent hyperbolic MHD nanoliquids on non-isothermal stretched sheets: Analyzing the impact of transport parameters, variable fluid properties and convective boundary conditions

The key focus of this research is to look at how tangent hyperbolic magnetohydrodynamic (MHD) nano-liquids move in a non-isothermal coagulated stretched sheet. In this study, we intend to explore how fluid behavior responds to alternations in transport physical parameters. The coagulated sheet is subjected to two distinct boundary conditions to inspect the heat and mass transport rate of the nano liquid. The convective heat boundary condition (CBC) and mass-convective boundary condition (MCBC) are employed to specify the physical conditions at the boundaries of the problem domain. The boundary conditions, responsible for regulating heat flow and mass transfer rates, play a crucial role in shaping the liquid’s behavior. Using a similarity solution, the partial differential equation describing the flow of mass and heat within the system transforms into an interconnected network of non-linear ordinary differential equations. These mathematical equations are subsequently figured out using a numerical finite difference method. This study additionally examines the correlation between thermophoresis and Brownian motion, two fundamental concepts in the dynamics of colloidal suspensions. The study’s findings indicate that the temperature profile increases in all scenarios when the variable thermal conductivity and variable viscosity parameters are increased. In contrast, for the same parameters, the velocity profile is decreased. Further, increasing wall thickness reduces heat dissipation; consequently, the temperature profile similarly affects the velocity power index. The Biot number improves the rates of temperature transfer. These results underscore the significant influence of these parameters in predicting the behavior of MHD tangent hyperbolic nanofluids. This study elucidates the intricate interaction among different physical parameters in the dynamics of nano liquids, which holds significant implications for various industrial applications.

Performance analysis of diffusive thermo and thermo diffusive aspect in rate type chemically reactive liquid subject to variable fluid properties

Performance analysis of diffusive thermo and thermo diffusive aspect in rate type chemically reactive liquid subject to variable fluid properties

Experimental investigation on flow characteristics of regenerators considering variable fluid properties

A method was proposed to improve the accuracy of permeability and inertial resistance coefficient measurements for the flow characteristics of a regenerator, considering density and dynamic viscosity. Given the thickness of the porous medium at only 2 mm, and to simplify gradient data processing, the harmonic mean of the fluid density and dynamic viscosity was utilized. Various mesh counts of wire mesh and sintered powder filler were tested. The results showed that permeability decreased for both types of fillers as mesh count increased. Due to the high randomness inherent in the sintered powder, repeated tests were conducted, with errors being within 17%. The inertial resistance coefficient fluctuated between 300 and 600 mesh counts, with a significant increase at 700 mesh. In contrast, the inertial resistance coefficient of the wire mesh increased consistently with the mesh count. The significant inertial resistance within the sintered powder was due to its irregularity, and a high positive correlation was observed between the regularity of the filler microstructure and the pressure drop across the regenerator. The flow characteristic correlations for two types of fillers were derived, applicable within the Reynolds number ranges of 6.54 to 99.17 for the wire mesh filler and 0.86 to 15.91 for the powder filler, with both exhibiting a goodness of fit exceeding 95% being achieved.

Soret and Dufour effects on MHD mixed convective unsteady flow over stretching sheet with variable fluid properties and convective boundary condition

In several industrial and engineering applications, variable fluid properties play a major role in flow and heat transport processes. The goal of this communication is to analyse the Soret and Dufour effects for an unsteady MHD flow past a stretching sheet under the influence of temperature-dependent viscosity and thermal conductivity along with the convective boundary condition. The governing partial differential equations are transformed into nonlinear coupled ordinary differential equations with the help of similarity transformations, and a numerical analysis is done by using bvp4c, MATLAB’s built-in solver. The flow properties and heat transfer characteristics have been depicted graphically and numerically. Results show that the wall temperature gradient improves by about 8.5%, while the temperature of the fluid near the stretching sheet significantly improves upon increasing the Biot number. Employing fluids with higher viscosity and thermal conductivity consequently leads to a reduction of the wall temperature gradient by about 0.3% and 10.7%, respectively. Also, as the unsteadiness parameter increases, the wall-skin friction, heat and mass transfer rates significantly rise by about 10.4%, 4.4%, and 9.8%, respectively. Further, to verify the accuracy of the generated results, the computed results have been compared with published literature.

Natural convection and variable fluid properties of tangent hyperbolic nanofluid flow with Cattaneo-Christov theories and heat generation

The main aim behind this work is that we have to determine the enhancement that happens in thermal conductivity by using the Buongiorno model of nanofluid when the nanofluid particles are added to the tangent hyperbolic base fluid moving above the stretched surface. The viscosity of tangent hyperbolic nanofluid is assumed to be temperature-dependent. The modified form of the Fourier law of heat conduction motivated us; therefore, the Cattaneo-Christov heat and mass flux model is considered to observe its significance for heat and mass transport. The chemical reaction and heat generation are also considered to determine their influence on temperature and concentration gradients. This study is crucial because of its application in industrial manufacturing processes such as the coating of wire, the thinning of copper, the production of paper, photographic films, hot rolling, and the purification of crude oil. In electronic cooling systems, the efficient dissipation of heat in smartphones, computers, and data centers is critical to preventing overheating. Nanofluids, with their enhanced thermal properties, can significantly improve heat transfer rates, ensuring better performance, stability, and energy savings. The partial governing equations arising from fluid flow, mass, and heat transfer are transformed into ordinary differential equations via appropriate similarity variables. The obtained ordinary differential equations are solved numerically by using the Runge-Kutta Fehlberg method in the MATLAB software. The effects of the emerging parameters are represented through graphs. According to the results, the velocity profile upsurges due to the natural convection parameters and curvature parameter, while the power law index declines the velocity profile. As the Brownian motion coefficient rises, the concentration profile diminishes while the temperature profile increases. Both the concentration and temperature profiles increase for larger values of the thermophoresis parameter. The concentration profile declines for larger values of chemical reaction parameters, and enhancement happens in the temperature region.

Flow and heat transfer insights into a chemically reactive micropolar Williamson ternary hybrid nanofluid with cross-diffusion theory

Abstract The need for efficient nanotechnology has led to unexpected developments. Conserving continuous thermal propagation is essential in many industrial and thermal systems because it improves the efficiency of thermal engineering engines and machinery. Therefore, a promising platform to increase thermal power energy is the hybridization of magnetic nanoparticles in a heat-supporting, non-Newtonian fluid. In light of the above applications, a mathematical model is established to analyze the variable fluid features of the thermally radiative and chemically reactive flow of a micropolar Williamson ternary hybrid nanofluid with electromagnetohydrodynamic and electroosmosis forces on a porous stretching surface. Stratification boundary conditions and variable fluid properties were used to analyze the thermal and solutal behavior of the fluid flow. Furthermore, to measure the disorder of the flow system, entropy generation was considered by the impact of Joule heating and viscous dissipation. To develop the numerical scheme BVP4C in MATLAB, we first converted the mathematical flow model into two ordinary differential equations using a suitable transformation. The graphical and numerical results were determined against several parameters of a ternary hybrid nanofluid ( MWCNT , A l 2 O 3 , SiC ) ({\rm{MWCNT}},\hspace{0.25em}{\rm{A}}{{\rm{l}}}_{2}{{\rm{O}}}_{3},\hspace{0.25em}{\rm{SiC}}) and unary nanofluid ( A l 2 O 3 ) ({\rm{A}}{{\rm{l}}}_{2}{{\rm{O}}}_{3}) . The results indicate that the heat transfer rate is more prominent in the ternary hybrid nanofluid than in the unary nanofluid because the addition of nanofluids to the base fluid is used to improve the heat transport rate. It can be seen from the figures that a greater estimation of the magnetic and electric field parameters improves the fluid velocity because, for low values of M ≤ 1 M\le 1 , the aiding force is dominant compared to the retarding force, which results in an improvement in the velocity profile. Furthermore, the entropy generation rate increases for higher values of the Brinkman number and temperature ratio parameter because more heat is produced due to the greater values of Br {\rm{Br}} .

Numerical investigation of the effects of variable fluid properties on cilia-driven flow of tangent hyperbolic fluid in a channel with heat and mass transfer: A new approach to microfluidic pumps

Heat, mass transfer, and non-Newtonian fluid flow processes have gained significant interest in various industrial applications due to their substantial significance in the fields of technology, engineering, and science. The aforementioned processes hold significance in the context of polymer solutions, porous industrial materials, ceramic processing, oil recovery, and fluid beds. This study aims to investigate the impact of temperature-dependent viscosity and thermal conductivity on the cilia-driven flow of tangent hyperbolic fluid with mass and heat transfer. The objectives include analyzing how these variable properties affect the velocity, temperature, and concentration profiles within the fluid flow, thereby providing insights into potential applications in bioenergy systems and enhancing the understanding of non-Newtonian fluid dynamics. Viscous dissipation has been taken into consideration. Firstly, governing nonlinear coupled equations are solved in a fixed frame, and then the results are tracked in the wave frame. MATHEMATICA's NDSolve command is utilized to graphically discuss the findings for several different flow parameters. Analytically stated, solving a problem with such a coupled and nonlinear system is tough. The effect of new parameters is discussed on velocity and temperature profile and graphically shown. It has been observed that the thermal conductivity is improved at moderately low temperatures, whereas the opposite pattern is seen at comparatively high temperatures. On the other hand, the temperature distribution demonstrates a behaviour consistent with lowering as the number of heat Bolus increases. The findings that were provided offer beneficial insight into bioenergy systems and serve as a helpful benchmark for both experimental and extra-progressive computational Multiphysics models.

Entropy generated nonlinear mixed convective beyond constant characteristics nanomaterial wedge flow

Background and objectiveNanomaterial flows at present have received much attention of the researchers. Such motivation stems for their utilization in pharmaceutical, industrial, petroleum, manufacturing and engineering applications including regenerative medicine, treatment of cancer, electronic device cooling, solar collector, mineral oil, antimicrobial agents, thermal storage system, transformer cooling and X-imaging etc. Higher thermal energy requirement in several electrical and mechanical systems is desired in recent time due to high advancement of science and technology. For important application here the stagnation point flow due to wedge with nonlinear convection is explored. For porous media, the Darcy-Forchheimer relation is considered. Characteristics of nanofluid is added by utilizing Buongiorno's model. Variable fluid characteristics are under consideration. Applied magnetic field is accounted. Energy expression comprises thermal radiation, Brownian motion, Ohmic heating, thermophoresis and heat generation. First order reaction and entropy rate are considered. MethodologyNonlinear differential expressions are changed into dimensionless ordinary systems through adequate transformations. The resultant nonlinear ordinary systems are solved through optimal homotopy analysis technique (OHAM). ResultsOutcomes for influential variables about temperature, velocity, concentration and entropy rate have been arranged. Here results show that for magnetic field the liquid flow and entropy rate have opposite scenarios. Thermal distribution and concentration have reverse effects for random motion variable while similar effect holds for thermophoresis parameter. Magnetic field and diffusion parameters contribute to augment entropy generation. Higher values of temperature dependent electrical conductivity variable lead to increase entropy rate. Thermal distribution for radiation and Eckert number is similar.

INVESTIGATION OF THE LOADS ON THE ROD PUMPING UNIT WHEN THE FLUID LEVEL IN THE WELL CHANGES

The balance of the pumpjack, which is the most common type of drive for downhole rod pumps, has a significant impact on the efficiency of pumping operation of the well. It determines the degree of loading of the pumpjack, the amount of electricity consumed. However, during the operation of the well, the balance of the drive may be disrupted due to a change in the load on the balancer head due to the weight of the liquid column in the annulus and acting on the pump plunger. This situation is noted for wells operating in the periodic pumping mode, as well as when the inflow of reservoir fluid changes for various reasons (unstable inflow, deterioration of permeability of the downhole zone of the formation, changes in reservoir pressure during development and other reasons). The paper considers the issues of forming loads on the drive of rod installations at a variable dynamic fluid level in the well. A mathematical model is presented describing the formation of loads on the head of the pumpjack balancer, taking into account possible fluctuations in the dynamic level. Verification of the proposed model was performed and a good agreement was obtained between the model and field dynamometer cards. A field example shows that a decrease in the dynamic liquid level causes an increase in maximum loads on the balancer head by more than 10 %. It was found that due to a change in the balance of loads on the drive, the torque on the crank shaft increases when the rods move upwards, which leads to an increase in the asymmetry of loads on the drive and a violation of the balance of the rocking machine. The relevance of the use of dynamic balancing systems is substantiated, which allow maintaining the balance of loads acting on the drive in changing external conditions.

Design, modelling and evaluation of a variable inertance bypass fluid inerter

The inerter emerged as a mechanical analogy to the electrical capacitor, completing the force-current analogy. It operates as a one-port, two terminal device, where the equal and opposite forces at its terminals correlate with the relative acceleration between them. This relationship is governed by ‘inertance’, a quantity that bears the unit of mass, allowing inerters to exert inertial forces. Inerters have gained considerable traction, particularly in vibration control applications. Derived from their passive counterparts, variable inertance inerters enable active control of their inertance through integrated control mechanisms. This work presents the design, modelling and evaluation of a variable inertance inerter prototype dubbed the ‘Variable Inertance Bypass Fluid Inerter’ (VIBFI). An experimental prototype of the concept was designed, constructed and tested. Simultaneously, an effort to develop and validate a mathematical model of the VIBFI is thoroughly documented. Experimental results demonstrate the controllability of performance parameters of the device, including inertance and damping coefficients, through modulating the flow restriction of the bypass channel. The mathematical models derived for the device can serve as an estimate for its performance parameters, though further refinement is required.

Influence of the Presence of Different Signatures on the Heat Transfer Profile of Laminar Flow Inside a Microchannel

Abstract The process of transferring heat and mass involves a high-pressure decline. Hence microchannels are utilized in extremely efficient heat and mass transfer processes, such as in the systems of the lungs and kidneys. Due to their high surface-to-volume ratio and compact volume, microchannels have demonstrated superior thermal performance. In this work, micro-fins of different topologies and arrangements were used inside microchannels for modulating heat transfer from the surface of the fins, in the presence of flowing media. The influx of media was simulated in sinusoidal form, reproducing simplified form of physiological circulatory blood flow. The study was conducted in numerical domain, while heat transfer and mass transfer equations were solved using pardiso solver. Temperature modulation at the fin surfaces was conducted to examine the transient profile of heat transfer, as function of both variable fluid velocity as well as variable feeding heat sources. In case of different input boundary conditions, the effect of heat distributions on fluid flow with respect to spatial distribution of micro-fins within a microchannel was evaluated. Results revealed the difference in heat transfer profiles in microchannels in presence of different sets of fin configurations. It was found that rectangular fins have the highest heat transfer in fluid at all its spatial configurations; while semi-ellipsoidal-shaped fins had shown the least heat transfer profile at same surface area. At the same time, it was also observed that the rate of heat dissipation was faster and limited in semi-ellipsoidal-shaped fins configuration; while the heat transfer rate was found symmetrical and low in presence of rectangular fins. Hence, this article emphasizes the modulation of temperature and velocity variations within the working fluid by emphasizing the thermo-fluid coupling effects in microchannels.

Nonlinear convective transport of nanofluid over an inclined plate situated in a Darcy–Forchheimer porous medium with viscous dissipation and varying thermo-physical features

This article presents a theoretical analysis of the effects of varying thermo-physical properties, chemical reactions, and activation energy on the quadratic convective transport of nanofluids. The flow is created through an inclined plate in a Darcy–Forchheimer porous medium. The nanofluid model includes thermophoresis and Brownian motion to account for nanoparticle movement. The original flow equations are transformed using similarity transformations, and the resulting dimensionless equations are solved with a multi-domain spectral collocation approach. The effects of physical parameters on flow variables, heat and mass transfer coefficients are discussed. Comparisons between vertical and inclined plates reveal that inclination improves thermal performance but decreases velocity and engineering-related quantities. Fluctuating viscosity and nonlinear convection speed up fluid flow, whereas temperature rises with variable thermal conductivity and Biot number. Variable fluid properties, nonlinear convection, and convective heat conditions enhance heat transport coefficients. Activation energy boosts nanoparticle volume fraction profiles but decreases mass transport rates.

CFD elucidation of high-pressure subcooled boiling flow towards effects of variable refrigerant properties using OpenFOAM empirical closures

Boiling flow presents a significant concern, especially when a liquid surpasses its boiling point, potentially leading to catastrophic consequences. This research utilizes a two-phase code in the OpenFOAM software to investigate bubble formation during flow boiling. The well-established empirical models for calculating wall heat components were selected based on the operating conditions. The study incorporates experimental data from high-pressure boiling flow (10–30 bars) with variable properties of refrigerant R-12. The predictions reveal underpredictions in void fraction and liquid temperature compared to experimental observations. Significantly, the impact of the subcooling degree on void fraction behaviour is emphasized, and a potential underprediction of the evaporation portion is highlighted, particularly near the wall. Challenges in modelling bubble size distribution are evident through discrepancies in bubble diameter and velocity data, indicating the necessity for further advancements in the code. In summary, this numerical study provides valuable insights into the intricate dynamics of high-pressure subcooled boiling flow, especially when considering variable working fluid properties. Future efforts will focus on refining models for nucleation site density, bubble departure size, and lift-off frequency to enhance prediction accuracy.

Flow analysis of temperature-dependent variable viscosity Phan Thien Tanner fluid thin film over a horizontally moving heated plate

Comprehending the temperature-dependent variable viscosity Phan Thien Tanner fluid film flow over a horizontal heated plate with surface tension is essential to enhancing coating and lubrication process prediction models. This paper accords with the flow analysis of a temperature-dependent variable viscosity Phan Thien Tanner fluid film over a horizontal heated plate. The flow over a heated plate occurs as a result of the plate’s motion and the surface tension gradient. The Adomian decomposition method is utilized to solve a system of linear and nonlinear ordinary differential equations, resulting in series-form solutions. The series-form expressions for flow variables such as velocity, temperature, volume flow rate, and surface tension are derived. Moreover, the positions of stationary points are computed using MATHEMATICA. The analysis delineated that when the inverse capillary number, variable viscosity parameter, Deborah number, elongation parameter, and Brinkman number increase, the stationary points move closer to the heated plate. The temperature also rises with an increase in these parameters. The temperature rises with increasing viscous dissipation while it lowers with increasing thermal diffusion. When the Deborah number is high, the Phan Thien Tanner fluid behaves like a solid and the flow is only driven by the motion of the plate. A comparison between Newtonian and Phan Thien Tanner fluids is made for velocity, temperature, and stationary points as a special case.

Numerical research on disastrous mechanism of seepage instability of karst collapse column considering variable mass effect

In order to reveal the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect, a variable mass fluid–solid coupling mechanical model of water inrush is established, by considering the random distribution characteristics of a collapse column. Taking Qianjin coal mine as the research background, based on the Weibull distribution theory, the heterogeneous distribution characteristics of rock mass is described, and COMSOL Multiphysics numerical simulation software is employed to simulate the seepage characteristics and inrush water changes in collapse columns under different conditions of homogeneity, water pressure, and initial porosity. The research results show that the greater the homogeneity is, the more water conduction channels are formed, and the porosity increases accordingly, when considering the influence of different homogeneity on the seepage characteristics of broken rock mass, which eventually leads to water inrush accidents and a sharp increase in water inflow. Besides, when studying the seepage evolution law of different water pressures on a broken rock mass, an elevation of water pressure dramatically increases the porosity and seepage rate of the water. Over time, the broken rock particles gradually migrate and the fine particles are transported and eroded by the water flow, resulting in changes in the seepage characteristics and the formation of potential water diversion channels. Finally, when taking into account the effect of different initial porosity on the fractured rock mass seepage characteristics, the greater the original porosity is, the higher the seepage velocity is, and the particle migration increases the permeability. This leads to a more pronounced conductive water passage formation, which reveals the disastrous mechanism of seepage instability of karst collapse column considering variable mass effect.

[formula omitted]-Functions for fields of series- and parallel-connected boreholes with variable fluid mass flow rate and reversible flow direction

A new methodology is developed for the calculation of g-functions for the simulation of geothermal bore fields in non-stationary conditions. The g-functions are able to represent the variations of fluid mass flow rate and reversible flow direction, and model the effect of these variations on the long-term ground temperature response. The thermal model is constructed by coupling an axially-discretized finite line source solution for the ground heat transfer, a thermal resistance circuit model for the interior of the boreholes, as well as connectivity relations between parallel- and series-connected boreholes. Simulation experiments show that the new g-functions are required for the accurate prediction of fluid temperatures in series-connected boreholes with variable mass flow rate and reversible flow direction. A simulation of a borehole thermal energy storage system of 144 boreholes over a period of 20 years shows a maximum absolute error of 0.65 °C. The new g-functions thus extend the simulation capabilities of g-functions to borehole thermal energy storage systems.

Investigating radiative heat transfer, varied wall thickness, and slip effects on Casson nanofluid flow over a stretched sheet with heat source

ABSTRACT Understanding the intricate interplay between variable fluid properties such as slip and thermal conductivity when flowing over porous surfaces is of utmost importance for a wide range of engineering applications. This investigation delves into this uncharted territory, connecting the analytical capabilities of HAM (Homotopy Analysis Method) to reveal captivating insights into the impact of these variables on the dynamics of Casson nanofluid flow. Besides, we documented the flow aspects which include thermal radiation, heat source, variable wall thickness and chemical reaction. We alter the partial differential flow-related conditions into nonlinear ordinary ones employing the similarity transformation approach. Then, using a popular semi-analytical technique known as the Homotopy Analysis Method (HAM), we were able to untangle them. This method yields to power series solutions to nonlinear differential equations. To illustrate the impact of the velocity, temperature and concentration profiles, parametric research has been done using tables and diagrams. In the limiting sense, the numerical results of our methodology are in great association with the outcomes of previous research. Finally, it is noted that higher values of the velocity slip parameter cause an enhancement in fluid velocity, while escalating values of the thermal slip parameter cause a decline in temperature distribution.