Effect Of Frictional Heating Research Articles

Limiting thermal characteristics for flow of non-Newtonian fluids between asymmetrically heated parallel plates: An analytical study

In this work, an analytical study on the limiting thermal transport characteristics for the flow of a non-Newtonian fluid namely, power law liquid, between asymmetrically heated parallel plates is presented. The transport equations for mass, momentum, and energy are analytically solved to obtain closed-form expressions for the temperature distributions in the flow field and the limiting Nusselt number in terms of relevant parameters. The effects of frictional heating due to viscous dissipation on the heat transfer characteristics are studied. Results are presented in terms of degree of asymmetric heating, Brinkman number, and power law index. The most important finding from the present work is the nontrivial interplay between degree of asymmetric heating and the rheological behavior of the fluid in dictating the thermal transport characteristics of heat.

Variational and numerical analysis of a quasistatic thermo‐electro‐visco‐elastic frictional contact problem

AbstractIn this paper, we study a quasi‐static contact problem between a thermo‐electro‐viscoelastic body and an electrically and thermally conductive foundation. The contact is modeled using a normal compliance contact condition with Coulomb's friction law, a regularized electrical contact condition and a heat flux contact condition taking into account the frictional heating effects. After introducing the model, the functional framework and the assumptions about the data, we derive the variational formulation of the model and prove its solvability. The proof is based on results of variational inequalities and fixed point argument. Finally, we investigate a fully discrete approximation using, respectively, Euler scheme and finite element method for the spatial variable and the time derivatives. Some error estimates are then derived, leading to convergence results under suitable additional regularity conditions.

Combined Effects of Frictional and Joule Heating on MHD Nonlinear Radiative Casson and Williamson Ferrofluid Flows with Temperature Dependent Viscosity

The impacts of Joule’s dissipation and frictional heating on non-Newtonian ferrofluid flows past a bidirectionally stretching convective surface are investigated. We assumed that Fe3O4 nanoparticles are mixed with methanol. Both Casson and Williamson models are opted while formulating the basic flow equations. The impact of temperature dependent viscosity is accounted. The Joule heating and viscous dissipation impacts are also considered. Shooting and R.K. numerical procedures are used to solve the flow problem. Graphical and tabular illustrations are presented with a view of understanding the nature of flow and heat transfer for discrete values of flow parameters. It is worth to note that the thickness of velocity boundary layer of Casson fluid flow is greater than that of Williamson fluid flow. Also the presence of Joule and frictional heating leads to more heat energy to Casson fluid flow while compared to that of Williamson fluid. Heat transfer rate is better in Williamson fluid compared to that of Casson fluid.

Model of Effect of Hot Gas Ingress on Temperatures of Turbine Disks

Ingress is the leakage of hot mainstream gas through the rim-seal clearance into the wheel-space between the rotating turbine disk (the rotor) and the adjacent stationary casing (the stator). The high-pressure rotor is purged by a radial outflow of air from the high-pressure compressor, and this cooling air is also used to reduce the ingress. The engine designer needs to predict the stator and rotor temperatures as a function of cooling-flow rate. The sealing effectiveness determines how much air is needed to reduce or prevent ingress; although there are numerous theoretical and experimental papers on the effectiveness of different seal geometries, there are few papers on the effect of ingress on the temperature of the rotating disk. This is an unsolved problem of great practical importance: under high stress, a small increase in metal temperature can significantly reduce operating life. In this paper, conservation equations and control volumes are used to develop theoretical equations for the exchange of mass, concentration and enthalpy in an adiabatic rotor–stator system when ingress occurs. It is assumed that there are boundary layers on the rotor and stator, separated by an inviscid rotating core, and the fluid entrained from the core into the boundary layer on the rotor is recirculated into that on the stator. The superposed cooling flow protects the rotor surface from the adverse effects of hot-gas ingress, which increases the temperature of the fluid entrained into the rotor boundary layer. A theoretical model has been developed to predict the relationship between the sealing effectiveness on the stator and the adiabatic effectiveness on the rotor, including the effects of both ingress and frictional heating. The model involves the use of a nondimensional buffer parameter, Ψ, which is related to the relative amount of fluid entrained into the rotor boundary layer. The analysis shows that the cooling flow acts as a buffer, which attenuates the effect of hot gas ingress on the rotor, but frictional heating reduces the buffer effect. The theoretical effectiveness curves are in good agreement with experimental data obtained from a rotor–stator heat-transfer rig, and the results confirm that the buffer effect increases as the sealing effectiveness of the rim seals decreases. The analysis quantifies the increase in the adiabatic rotor temperature due to direct frictional heating, which is separate from the increase due to the combined effects of the ingress and the indirect frictional heating of the entrained fluid. These combined effects are reduced as Ψ increases, and Ψ = 1 at a critical flow rate above which there is no entrained fluid and consequently no indirect heating of the rotor. The model also challenges the conventional physical interpretation of ingress as, in general, not all the hot gas that enters the rim-seal clearance can penetrate into the wheel-space. The ingress manifests itself through a mixing of enthalpy, which can be exchanged even if no ingested fluid enters the wheel-space.

Numerical Simulation of Frictional Heating Effects of Sliding Friction Bearings for Isolated Bridges

Sliding friction bearings are effective passive devices to mitigate the seismic responses of structures. Extensive researches have been conducted on sliding bearings. However, most previous studies were based on the assumption that the effects of frictional heating are negligible. A three-dimensional thermal-mechanical-coupled finite element (FE) model of the friction pendulum system (FPS) was developed in this study. Good agreements between the numerical results and the data measured in the previous tests, in terms of the force–displacement curves and temperature time-histories, indicate that the proposed FE model can predict the response of the FPS. Based on the developed FE model, the surface temperature distribution, the effective stiffness and the energy dissipation of the double concave friction pendulum and multiple friction pendulum bearings were investigated and compared. In addition, the thermal states of the sliding bearings in the bridge during earthquake were evaluated. The numerical results indicate that the temperature rise in the sliding bearings leads to the degradation of the effective stiffness and less energy dissipation. The relative displacements of the bearings increase considering the frictional heating effects in the bearings. If the frictional heating of the bearings is ignored, the peak bearing displacements will be underestimated.

Temperature and thermal stress distribution in underwater friction stir welding of aluminium plates

This paper studies the effect of ambient operating conditions on temperature and thermal stresses generated in friction stir welding (FSW) of aluminium alloy plates. AA1050 plate was used with 120×60×3 mm dimensions. Both plates were joined with butt weld in air and underwater ambient conditions. Finite element analysis software COMSOL Multiphysics was used to obtain the transient temperature and thermal stresses induced inside the plates during welding under the two conditions. The effect of frictional heat generated on different parts of weld tool was determined. The results show that weld tool pin has the highest temperature in both the ambient conditions and that the thermal stress and heat affected zone was reduced in case of water.

Effect of Friction Heat on Interfacial Wear and Brake System Stability

Effect of Friction Heat on Interfacial Wear and Brake System Stability

Determination of critical condition for initiation of dynamic recrystallisation in Zr-1%Nb alloy

The critical stress and strain for initiation of dynamic recrystallisation (DRX) in Zr-1%Nb alloy have been determined by employing two different approaches. The work hardening rate versus stress curve and the natural logarithm of work hardening rate versus strain were used for this analysis. To evaluate the onset of DRX in Zr-1%Nb alloy, the hot deformation behaviour of this alloy has been studied in the temperature range of 770–850 °C and strain rates range 10−2 to 1 s−1. To reduce friction during the tests, the ends of samples were coated with graphite powder and a thin layer of mica placed between the surface of samples and the anvils. Nevertheless, the flow stress values were corrected to eliminate the effects of friction and adiabatic heating during the tests. The outcomes of work hardening rate analysis showed that the first method (work hardening rate versus stress) is the best method to determine the critical conditions of initiation of DRX. All in all, for Zr-1%Nb alloy, the dynamic recrystallisation was found to start when the normalised stress and strain reach the values of 0.91 and 0.87, respectively. Furthermore, the transmission electron microscopy (TEM) analysis showed that the DRX took place through a continuous mechanism, and optical microstructures confirmed that at low temperature and high strain rate the flow curves could be explained by localised deformation and shear band formation.

Protocol for the visualisation of axial temperature gradients in ultra high performance liquid chromatography using infrared cameras

A protocol was developed for the visualisation of axial temperature gradients on a Kinetex column (1.3 μm C18 100 Å 50 × 2.1 mm) operated at near maximum pressure of the system (Pmax) using an infrared camera. Real time viscous frictional heating effects across the entire column length was observed, and showed that with increasing flow rate there was an increase in the maximum temperature of the column, and the difference between the inlet and outlet temperatures. Temperature profile data over the entire length of the column revealed the dynamics of heat exchange processes along different parts of the column, and raises the question on potential heating effects on eluents. The axial temperature gradients of eluents such as pure methanol, isopropyl alcohol and acetonitrile near Pmax were compared; finding that acetonitrile which had the highest flow velocity at Pmax gave the highest overall temperature increase for these eluents.

Entropy generation in MHD mixed convection stagnation-point flow in the presence of joule and frictional heating

This article looks at the second law analysis of MHD boundary layer stagnation-point flow past over linearly stretched sheet. The thermal boundary condition is supposed to be non-isothermal and the effects of friction and Joule heating have been analysed. By using similarity transformations, the model nonlinear partial differential equations in two independent variables are reduced to ordinary differential equations. The numerical techniques, namely shooting and fourth order Runge-Kutta are used to give a numerical solution. An expression for dimensionless entropy generation and Bejan number are obtained and computed using velocity and temperature profiles. The main objective of this article is to analyse the effects of a magnetic parameter, Prandtl number, Eckert number, stretching parameter, mixed convection parameter and dimensionless temperature parameter on the volumetric rate of entropy production and Bejan number. It is found that entropy generation increases with enhancing values stretching parameter and decrease with the increasing values of dimensionless temperature parameter.

An improved two-phase model for saturated steam flow in multi-point injection horizontal wells under steady-state injection condition

Previous models neglected the effect of frictional heating on steam quality and enthalpy in wellbores when saturated steam is injected into multi-point injection horizontal wellbores.In this paper, new energy conservation equations were developed for increasing the calculation accuracy of steam quality in inner tubing (IT) and annuli. Then, coupled with the momentum balance equations, the distributions of steam quality and pressure along the IT and annuli were obtained by using the straight forward numerical method. The predicted results from the new model were compared against field data and previous models. It is found that: (a). The effect of heat loss to surrounding formation on the temperature profiles is weak. However, the heat loss has a significant influence on the profile of steam quality in wellbores. (b) When removing the item of frictional work from the energy balance equations, the predicted values of steam quality and enthalpy are lower than actual data. This error in energy conservation equation may be hidden when the predicted temperatures showed good agreement with field data. (c) With the help of multi-point injection technique, formation heating effect at both heel-point and toe-point can be improved.

Visualizing and studying frictional heating effects in reversed-phase liquid chromatography using infrared thermal imaging

Column temperature control is a fundamental component of liquid chromatography experiments. However, it is typically monitored indirectly by tracking the temperature of an adjacent heating element that exchanges heat with the column in a controlled environment. The practice of not directly measuring the column temperature means that uncontrolled contributions of heat, such as frictional heating inside the column, can be overlooked. The present work describes the use of a high-resolution infrared thermal imaging camera to directly measure the column heat map during mobile phase flow. The approach was used to measure the longitudinal temperature gradient formed with three common mobile phases: water, methanol, and acetonitrile, in two 50 mm reversed-phase columns, a 1.7 μm particle-packed column and a polystyrene divinylbenzene monolith. In a close approximation to an adiabatic environment, the temperature gradients (ΔT) observed with the 1.7 μm particle column at a linear velocity of 5.8 mm/s were up to +16.6 and + 12.8 °C above an ambient temperature of 23 °C for water and acetonitrile, respectively. In the case of water, the measured temperature gradient values (ΔT) were within 1% difference of theoretically-calculated values and on average within 10% for acetonitrile. By contrast, the ΔT observed in the monolith was negligible. The elevated temperatures that are generated through friction in sub-2 μm particle columns may be particularly important to consider for the design of experiments that measure structural features of temperature-sensitive analytes, such as biomolecules. While frictional heating is one important application of the thermal imaging approach described, the technique can be used to provide a data-rich profile of heat exchange in numerous experimental configurations, chromatographic or otherwise.

Investigation of flow between deformed disks in hydro-viscous drive

Abstract In order to investigate the dynamic behavior of oil film between deformed disks in hydro-viscous drive, revised mathematical models based on steady-state and axisymmetric flow conditions are developed. The models consist of two forms of thermal deformation that are caused by the combined effect of frictional heat and radial constraint. An approximate solution to the theoretical model is obtained assuming that the fluid viscosity remains constant. And the model considering the effect of variable viscosity is solved by means of computation fluid dynamics code FLUENT. Then the analytical and numerical solution profiles are compared. The results show that peak velocity at the outlet, pressure gap and temperature rise between the inlet and outlet of the film increase with increasing axial deformation size. The effect of radial deformation on the increase of friction area of the disks leads to the increase of the flow rate. The friction pairs should be kept in reasonable deformation size in case of turbulent flow. It is also found that both axial deformation and radial deformation significantly contribute to the increase of viscous torque on condition that the deformation size is controllable. Based on the comparison with the experimental results, the performance of the theoretical model is found satisfactory.

Effect of frictional heating and thermal radiation on MHD flow of micropolar-nanoliquid along a curved surface

Effect of frictional heating and thermal radiation on MHD flow of micropolar-nanoliquid along a curved surface

Exploring the Effect of Frictional Heat on Rate of Fuel Combustion by ICE through Modeling and Simulation with Reference to ICE Parameters.

Otto cycle operations of ICEs have relatively higher capacities and efficiency. Factors of efficiency, emission, fuel consumption and output power are considered during design and construction of ICEs. Engine size, engine weight, number of pistons, swept volume, cylinder arrangement and number of valves all differs in accordance to type of ICE. Fundamental principle of ICE is burning of air – fuel mixture of appropriate proportions in air tight chamber to produce heat energy for motion. Fossil fuel of diesel and gasoline obtained from underground are the main fuels used by ICEs. The engine block houses cylinders, pistons rings, connecting rods and pistons. At top seals of cylinders are located inlet valves, outlet valves and channels. Crankcase houses crankshaft and bearings whiles the sump serves as reservoir for lubrication oil. Lubrication oil also known as lubricant reduces friction between moving surfaces in ICEs through piston ring grooves. Connecting rod is the linkage between crankshaft and piston. Gudgeon – pin transmits combustion force from piston to connecting rod then to crankshaft. Thus, crankshaft converts reciprocating motion of piston to cyclic motion. During operations of ICEs, friction occurs between pistons with piston rings collectively and inner walls of cylinder. Frictional effects account for about thirty five percent (35%) of total heat generated in ICEs. The methodology adopted by this article is modeling and simulating frictional models by previous authors. These models were incorporated with ICE parameters before modeling and simulation again. Objectively, graphical results show reduction in heat generation due to friction.

Effect of frictional heating on mixed convection flow of chemically reacting radiative Casson nanofluid over an inclined porous plate

The present study deals with the boundary layer analysis of a 2D magnetohydrodynamic flow of chemically reacting Casson nanofluid flow over a semi-infinite inclined porous plate. The energy and diffusion equation are encompassed with frictional heating, heat generation/absorption, thermo diffusion and thermal radiation effects. For making the analysis more attractive we pondered two distinct type of nanofluids namely, TiO2-water and CuO-water. The transmuted governing PDEs are resolved analytically by employing regular perturbation method. The impact of pertinent flow parameters on momentum, thermal and mass transport behavior including the skin friction factor, thermal and mass transport rate are examined and published with the assistance of graphical and tabular forms. Results describe that thermal radiation and chemical reaction restrictions have a propensity to enhance thermal and mass transport rates, respectively. And also, water based TiO2 nanofluid possess higher velocity compared with water based CuO nanofluids.

Joule heating effect on a continuously moving thin needle in MHD Sakiadis flow with thermophoresis and Brownian moment

In the current study, we investigated the impact of thermophoresis and Brownian moment on the boundary layer 2D forced convection flow of a magnetohydrodynamic nanofluid along a persistently moving horizontal needle with frictional heating effect. The various pertinent parameters are taken into account in the present analysis, namely, the thermophoresis and Brownian moment, uneven heat source/sink, Joule heating and frictional heating effects. To check the variation in the boundary layer behavior, we considered two distinct nanoparticles namely Al50Cu50 (alloy with 50% alumina and 50% copper) and Cu with water as base liquid. Numerical solutions are derived for the reduced system of governing PDEs by employing the shooting process. Computational results of the flow, energy and mass transport are interpreted with the support of tables and graphical illustrations. The obtained results indicate that the increase in the needle size significantly reduces the flow and thermal fields. In particular, the velocity field of the Cu-water nanofluid is highly affected when compared with the Al50Cu50 -water nanofluid. Also, we showed that the thermophoresis and Brownian moment parameters are capable of enhancing the thermal conductivity to a great extent.

Entropy generation in hydromagnetic boundary flow under the effects of frictional and Joule heating: Exact solutions

The objective of the present article is to discuss the effects of viscous dissipation and Joule heating on entropy generation in a hydromagnetic boundary layer flow. Governing equations are reduced to self-similar equations via suitable similarity transformations. The expressions for the volumetric entropy generation rate and the Bejan number are also obtained using similarity transformations. The exact solution of the transformed energy equation is computed using the Laplace transform treatment. The obtained exact solutions are utilized to calculate the entropy generation number and the Bejan number. The impacts of Prandtl number, viscous dissipation parameter (Eckert number), magnetic parameter, mass suction and temperature difference parameter on entropy generation and Bejan number are discussed graphically. The increasing value of the temperature difference parameter reduces the entropy generation. The entropy generation increases with the increasing values of the magnetic parameter, the Eckert number, the mass suction parameter and the Prandtl number.

31P Solid-State NMR Relaxation in the Zirconium Phosphate Network in the Presence of Paramagnetic Centers: A Detailed Relaxation Study in Static and Rotating Samples of Layered Zirconium Phosphate Materials

The careful study of MAS effects on the spin–lattice and spin–spin phosphorus NMR relaxation in two layered zirconium phosphate materials, α-ZrP and m-PEG-PO3/Zr(IV)/DOX/ZrP, has clearly shown that the fast spin-diffusion and limited spin-diffusion mechanisms are completely negligible in spite of the presence of paramagnetic centers detected in these materials by EPR. The 31P T1 relaxation is always nonexponential in static and spinning samples as well. The 31P T1 relaxation in α-ZrP follows a stretched exponential law to show the presence of a 31P T1 distribution. The 31P T1 time remarkably depends on spinning rates only in a 7 mm NMR probe head due to the frictional heating effects in 7 mm rotors but not due to the spin-diffusion mechanism. In accord, the 31P T1 and T2 times are independent of MAS rates in the experiments performed with 2.5 mm rotors. All the 31P T1 and T2 relaxation data support well the interpretation of the 31P T1 times in the zirconium phosphate network by dipolar proton–phosphorus interactions and justify the application of the 31P T1 and 31P T1/T2 approaches to probing molecular mobility in zirconium phosphate materials.

Non-isothermal flow of a Bingham fluid with pressure and temperature dependent viscosity

In this paper we investigate the non-isothermal flow of a Bingham fluid whose viscosity and yield stress depend on temperature and pressure. We consider two situations: in the first one we assume that the buoyancy effects are dominant and influence the development and evolution of the unyielded plug. In this case the governing equations are obtained via the Oberbeck–Boussinesq approximation which is derived using a perturbative approach. We show that within this approximation the heat generated by viscous friction can be safely neglected. In the second situation we assume that the frictional heating effects are dominant and influence the flow via the viscosity and yield stress that depend on temperature. For both situations we investigate the simple unidirectional flow between plates subjected to given thermal conditions. We derive the equations for the steady fully developed flow and we determine the exact position of the yield surfaces separating the yielded and the unyielded domain. We also show some plots to assess the effects due to the dependence of the rheological parameters on the temperature and pressure.