Influence of Thermal Conductivity of Lubricant on the THD Characteristics of a Plain Journal Bearing

1991 ◽  
Author(s):  
C. Rajalingham ◽  
B. S. Prabhu ◽  
R. B. Bhat ◽  
G. D. Xistris
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Variation ◽  
Heat Generation ◽  
Journal Bearing ◽  
Lubricant Film ◽  
Fluid Film ◽  
Adiabatic Conditions ◽  
Viscous Heat ◽  
Hydrodynamic Journal Bearing

Abstract The viscous heat generation in the lubricant film of a hydrodynamic journal bearing causes a rise in temperature of the fluid film. Considering the influence of the temperature variation along and across the film, the performance of a journal bearing is investigated under adiabatic conditions for different values of thermal conductivity of the lubricant. In this analysis, the temperature of the journal surface has been chosen to ensure that there is no net heat transfer from the lubricant The results show that the variation of temperature across the film affects bearing performance significantly and that an increase in lubricant thermal conductivity enhances bearing performance.

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

scholarly journals A NOTE ON THE CONSTANT THERMAL CONDUCTIVITY HYPOTHESIS AND ITS CONSEQUENCE FOR CONDUCTION HEAT TRANSFER PROBLEMS

2014 ◽  
Vol 13 (2) ◽  
pp. 48
Author(s):  
R. M. S. Gama
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
High Temperature ◽  
Heat Generation ◽  
Strong Dependence ◽  
Temperature Gradients ◽  
Conduction Heat Transfer ◽  
Kirchhoff Transformation ◽  
Constant Thermal Conductivity ◽  
Transfer Problems

This work discuss the usual constant conductivity assumption and its consequences when a given material presents a strong dependence between the temperature and the thermal conductivity. The discussion is carried out considering a sphere of silicon with a given heat generation concentrated in a vicinity of its centre, giving rise to high temperature gradients. This particular case is enough to show that the constant thermal conductivity hypothesis may give rise to very large errors and must be avoided. In order to surpass the mathematical complexity, the Kirchhoff transformation is used for constructing the solution of the problem. In addition, an equation correlating thermal conductivity and the temperature is proposed.

Heat Flux and Variable Thermal Conductivity Effects on Casson Flow and Heat Transfer due to an Exponentially Stretching Sheet with Viscous Dissipation and Heat Generation

2016 ◽  
Vol 14 (1) ◽  
pp. 167-174 ◽  
Author(s):  
Ahmed M. Megahed
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Generation ◽  
Stretching Sheet ◽  
Variable Thermal Conductivity ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flow And Heat Transfer ◽  
Exponentially Stretching

AbstractIn this paper, we introduce a theoretical and numerical study for the effects of thermal buoyancy and constant heat flux on the Casson fluid flow and heat transfer over an exponentially stretching sheet taking into account the effects of variable thermal conductivity, heat generation/absorption and viscous dissipation. The governing partial differential equations are transformed into coupled, non-linear ordinary differential equations by using suitable transformations. Numerical solutions to these equations are obtained by using the fourth order Runge-Kutta method with the shooting technique. The effects of various physical parameters which governing the flow and heat treansfer such as the buoyancy parameter, the thermal conductivity parameter, heat generation or absorption parameter and the Prandtl number on velocity and temperature are discussed by using graphical approach. Moreover, numerical results indicate that the local skin-friction coefficient and the local Nusselt number are strongly affected by the constant heat flux.

Finite element thermal analysis of a moving porous fin with temperature-variant thermal conductivity and internal heat generation

2020 ◽  
Vol 1 (1) ◽  
pp. 110
Author(s):  
Gbeminiyi Sobamowo ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Finite Element ◽  
Heat Generation ◽  
Peclet Number ◽  
Numerical Solutions ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Péclet Number ◽  
Porous Fin

This paper focuses on finite element analysis of the thermal behaviour of a moving porous fin with temperature-variant thermal conductivity and internal heat generation. The numerical solutions are used to investigate the effects of Peclet number, Hartmann number, porous and convective parameters on the temperature distribution, heat transfer and efficiency of the moving fin. The results show that when the convective and porous parameters increase, the adimensional fin temperature decreases. However, the value of the fin temperature is amplified as the value Peclet number is enlarged. Also, an increase in the thermal conductivity and the internal heat generation cause the fin temperature to fall and the rate of heat transfer from the fin to decrease. Therefore, the operational parameters of the fin must be carefully selected to avoid thermal instability in the fin.

Heat transfer to power-law fluids flowing in pipes and flat ducts with viscous heat generation

1991 ◽  
Vol 46 (5-6) ◽  
pp. 1385-1392 ◽  
Author(s):  
A.F. Flores ◽  
J.C. Gottifredi ◽  
G.V. Morales ◽  
O.D. Quiroga
Keyword(s):  
Heat Transfer ◽  
Heat Generation ◽  
Power Law ◽  
Viscous Heat ◽  
Power Law Fluids

A semianalytical approach to nonlinear fluid film forces of a hydrodynamic journal bearing with two axial grooves

2019 ◽  
Vol 65 ◽  
pp. 318-332 ◽  
Author(s):  
Yongfang Zhang ◽  
Xianwei Li ◽  
Chao Dang ◽  
Di Hei ◽  
Xia Wang ◽  
...  
Keyword(s):  
Journal Bearing ◽  
Fluid Film ◽  
Hydrodynamic Journal Bearing ◽  
Nonlinear Fluid

scholarly journals Studies on the Process of Ultrasonic Bonding of Nonwovens: Part 1 — Theoretical Analysis

2001 ◽  
Vol os-10 (2) ◽  
pp. 1558925001OS-01
Author(s):  
Zhentao Mao ◽  
Bhuvenesh C. Goswami
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Generation ◽  
Process Model ◽  
Viscoelastic Behavior ◽  
Coupled Model ◽  
Bonding Process ◽  
Heat Generation Rate ◽  
Ultrasonic Bonding ◽  
The Web

A model has been developed to predict the bonding behavior of nonwovens during the ultrasonic bonding process. The model includes the following subprocesses: mechanics and vibrations of the web and horn, viscoelastic behavior of webs and heat generation, and heat transfer. Each subprocess was modeled first and then combined together with the boundary conditions to develop an overall process model. The compressional behavior and thermal conductivity of webs will be discussed and their appropriate equations have been chosen for model. A Finite Element Method (FEM) was used to solve the above coupled model. Subsequently, the heat generation rate and the temperature change during the bonding process were calculated.

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