The Importance of the Heat Capacity of Lubricants With Nanoparticles in the Static Behavior of Journal Bearings

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Rodrigo Nicoletti
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Load Capacity ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Volumetric Heat Capacity ◽  
Static Behavior ◽  
Load Carrying ◽  
Bearing Load ◽  
Interesting Solution

Nanoparticle additives increase the viscosity of lubricants, thus being an interesting solution for improving the load carrying capacity of hydrodynamic bearings. But, nanoparticles also change the thermal properties of the lubricant. Would these thermal properties be important to the static characteristics of lubricated bearings? The answer is yes, being the volumetric heat capacity an important parameter. In this work, the static behavior of journal bearings is studied when nanoparticles are added to the lubricant. A thermohydrodynamic analysis is performed with oil ISO VG68 (base fluid) and six different nanoparticles are considered as additives: Si, SiO2, Al, Al2O3, Cu, and CuO. The numerical results show that the bearing load capacity can be increased up to 10%, not only because of the higher viscosity, but also because of the higher volumetric heat capacity of the lubricant with nanoparticles. Higher volumetric heat capacity of the lubricant decreases temperature development in the bearing gap, thus resulting in higher viscosity distribution for the same operating conditions. In fact, the best results were obtained with ISO VG68 + copper oxide (CuO), whose volumetric heat capacity is the highest among the tested nanofluids. Such results were not equaled when only the viscosity of the lubricant had been changed.

scholarly journals Testing a Gypsum Composite Based on Raw Gypsum with a Direct Admixture of Paraffin and Polymer to Improve Thermal Properties

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3241
Author(s):  
Krzysztof Powała ◽  
Andrzej Obraniak ◽  
Dariusz Heim
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Phase Change ◽  
Large Scale ◽  
Building Materials ◽  
Residential Buildings ◽  
Energy Performance ◽  
Polymer Content ◽  
Volumetric Heat Capacity

The implemented new legal regulations regarding thermal comfort, the energy performance of residential buildings, and proecological requirements require the design of new building materials, the use of which will improve the thermal efficiency of newly built and renovated buildings. Therefore, many companies producing building materials strive to improve the properties of their products by reducing the weight of the materials, increasing their mechanical properties, and improving their insulating properties. Currently, there are solutions in phase-change materials (PCM) production technology, such as microencapsulation, but its application on a large scale is extremely costly. This paper presents a solution to the abovementioned problem through the creation and testing of a composite, i.e., a new mixture of gypsum, paraffin, and polymer, which can be used in the production of plasterboard. The presented solution uses a material (PCM) which improves the thermal properties of the composite by taking advantage of the phase-change phenomenon. The study analyzes the influence of polymer content in the total mass of a composite in relation to its thermal conductivity, volumetric heat capacity, and diffusivity. Based on the results contained in this article, the best solution appears to be a mixture with 0.1% polymer content. It is definitely visible in the tests which use drying, hardening time, and paraffin absorption. It differs slightly from the best result in the thermal conductivity test, while it is comparable in terms of volumetric heat capacity and differs slightly from the best result in the thermal diffusivity test.

An Approximate THD Theory for Journal Bearings

1990 ◽  
Vol 112 (2) ◽  
pp. 224-229 ◽  
Author(s):  
G. Gupta ◽  
C. R. Hammond ◽  
A. Z. Szeri
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Pressure Coefficient ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Substantial Agreement ◽  
Interactive Mode ◽  
Lubricant Flow ◽  
Bearing Load ◽  
Sophisticated Model

The aim of this paper is to make available to the industrial designer results of the thermohydrodynamic theory of journal bearings, by providing a simplified, yet accurate model of journal bearing lubrication that can be implemented on a personal computer and be used in an interactive mode. The simplified THD theory we propose consists of two coupled ordinary differential equations for pressure and energy and an algebraic equation for viscosity, which are to be solved iteratively. Bearing load capacity, maximum bearing temperature, maximum pressure, coefficient of friction and lubricant flow rate calculated from this simplified theory compare well with results from a more sophisticated model. We also make comparisons with experimental data on full journal bearings, demonstrating substantial agreement between experiment and simplified theory.

Measurement of the Thermal Properties of Innovative Highly-Insulating Non-Structural Concretes

2019 ◽  
Vol 390 ◽  
pp. 41-52 ◽  
Author(s):  
Milena Kušnerová ◽  
Marta Harničárová ◽  
Jan Valíček ◽  
Zuzana Palková ◽  
Zdenko Tkáč ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Mass Parameter ◽  
Thermal Characteristic ◽  
Cementitious Composites ◽  
Thermal Mass ◽  
Volumetric Heat Capacity ◽  
Materials Selection ◽  
Material Parameters ◽  
Measurement Results

Thermal characteristic of insulation concretes is one of the key components in materials selection especially in civil constructions. In this article, non–tabulated material parameters of some innovative highly-insulating non-structural concretes are presented. The specific volumetric heat capacity, specific heat capacity, parameter of temperature diffusivity and thermal mass parameter of the innovative highly-insulating cementitious composites were determined. The experiments were conducted using a prototype automated calorimetric chamber. The measurement results are compared with those obtained by using a commercial multifunctional instrument (Isomet 2114) and are accompanied by the measurement of other significant thermal parameters of the cementitious composites under investigation. The results indicated that there is potential of using the newly created types of concrete for insulation purposes.

Measurement of Oil Aeration Effects in Journal Bearings

2002 ◽  
Author(s):  
J. L. Nikolajsen ◽  
D. Dong ◽  
M. J. Goodwin
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Damping Capacity ◽  
Bearing Load ◽  
Bearing Stiffness

Preliminary measurements have been conducted to determine the effect of oil aeration on journal bearing performance. Oil aeration was observed to reduce the bearing load capacity and to increase the bearing stiffness. Also, the bearing damping capacity was improved significantly by oil aeration.

THD Analysis in Tilting-Pad Journal Bearings Using Multiple Orifice Hybrid Lubrication

1999 ◽  
Vol 121 (4) ◽  
pp. 892-900 ◽  
Author(s):  
I. F. Santos ◽  
R. Nicoletti
Keyword(s):  
Load Capacity ◽  
Flow Behavior ◽  
Journal Bearings ◽  
Operational Conditions ◽  
Tilting Pad ◽  
Bearing Load ◽  
Cooling Effects ◽  
Experimental Values ◽  
Oil Injection ◽  
Tilting Pad Journal Bearings

Tilting pad journal bearings (TPJB) using multiple orifice hybrid lubrication are analyzed applying a thermohydrodynamic (THD) theory. Adiabatic boundary conditions are adopted, and a two-dimensional model is used to represent the fluid flow behavior in the bearing gap. The influence of operational conditions on the temperature distribution and on the bearing load capacity is discussed and compared to theoretical and experimental values for a conventional hydrodynamic case (without radial oil injection). To improve the cooling effects, as well as rotor attitudes, the best location for orifices is the area near the pad edges.

Analysis of Noncircular Gas Journal Bearings

1975 ◽  
Vol 97 (4) ◽  
pp. 616-623 ◽  
Author(s):  
O. Pinkus
Keyword(s):  
Reynolds Equation ◽  
Load Capacity ◽  
Full Range ◽  
Maximum Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Significant Advance ◽  
Arbitrary Direction ◽  
Isothermal Conditions ◽  
Load Vector

The compressible Reynolds Equation under isothermal conditions was solved for finite elliptical and 3-lobe bearings with the load vector acting in any arbitrary direction over the full range of 360 deg. Envelopes of minimum and maximum eccentricity for a given set of operating conditions are provided, the first to yield maximum load capacity, and the second to assist stability by a choice of the highest possible ε. Some values of the spring and damping forces are also given and it is shown that in comparison with conventional bearings, the non-circular designs offer a significant advance in stiffness, particularly for low ε, when instability is most often encountered.

Condensing Vapor Lubrication of Self-Acting Long Journal Bearings

1966 ◽  
Vol 88 (1) ◽  
pp. 236-245 ◽  
Author(s):  
W. Unterberg ◽  
J. S. Ausman
Keyword(s):  
Load Capacity ◽  
Saturation Pressure ◽  
Journal Bearings ◽  
Variable Pressure ◽  
Maximum Pressure ◽  
Two Phase ◽  
Bearing Load ◽  
Phase Liquid ◽  
High Pressure Region ◽  
Vapor Region

This is a theoretical investigation into the behavior of self-acting long journal bearings lubricated with vapor which may partially condense in the high-pressure region of a loaded bearing. Thermohydrodynamic considerations indicate that the lubricant temperature remains constant throughout the bearing. When the maximum pressure in the bearing reaches the saturation vapor pressure at the constant temperature, a further increase in bearing load then causes partial condensation instead of a rise in maximum pressure. In the partial condensation regime, the fluid annulus is made up of (a) a single-phase vapor region with variable pressure, and (b) a two-phase liquid-vapor region at constant saturation pressure. The regional interface locations and the bearing pressure distribution are obtained by “linearized ph” methods under the restrictions or boundary conditions of saturation pressure at the interfaces and constant lubricant mass content. It is shown that complete condensation cannot occur, so that the maximum pressure in the condensing vapor-lubricated bearing is limited to the saturation pressure. For this reason, the resulting load capacity always lies below that of a corresponding bearing lubricated with a noncondensing gas.

Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
C. I. Papadopoulos ◽  
E. E. Efstathiou ◽  
P. G. Nikolakopoulos ◽  
L. Kaiktsis
Keyword(s):  
Carrying Capacity ◽  
Stokes Equations ◽  
Load Capacity ◽  
Three Dimensional ◽  
Load Carrying Capacity ◽  
Thrust Bearings ◽  
Micro Channels ◽  
Wide Range ◽  
Load Carrying ◽  
Bearing Load

This paper presents an optimization study of the geometry of three-dimensional micro-thrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as micro-channels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of single-objective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

Influence of Thermal Properties Accuracy on Transient Conduction Models

2010 ◽  
Author(s):  
Pedro Vargas ◽  
Aura L. Lo´pez de Ramos
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Transient State ◽  
Variable Properties ◽  
Volumetric Heat Capacity ◽  
Cooling Process ◽  
Heating And Cooling ◽  
Temperature Variable ◽  
The One ◽  
Typical Temperature

The influence of thermal properties accuracy on the heat transfer mathematical models in transient state for food was studied in this work. To pursue this objective, a model in transient state with temperature variable thermal properties was solved using the method of finite differences and the alternate implicit direction scheme to a food inside a cylindrical container under a sudden heating and cooling process, similar to a method of sterilization and/or pasteurization. The model takes into account a linear dependence of the properties with the temperature. An analysis of the behavior of the main thermal properties of the food based on temperature is presented in this article. The results showed that the prediction of the transient state model is more sensitive to perturbations in the values of volumetric heat capacity than thermal conductivity and diffusivity; however, the volumetric heat capacity varies considerably less with temperature. Models with constant properties yield minor deviations when they are evaluated at typical temperature of the cooling or heating processes. The use of the constant thermal diffusivity model with diffusivity is suggested to be evaluated at temperatures between the average and the final heating or cooling process to ensure deviations less than 5%, between the exact model and the simplified one. This solution is considerably simpler than the one obtained with the variable properties model.

The Effects of Temperature and Inertia on Hydrostatic Thrust Bearing Performance

1971 ◽  
Vol 93 (2) ◽  
pp. 307-312 ◽  
Author(s):  
L. L. Ting ◽  
J. E. Mayer
Keyword(s):  
Load Capacity ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Rotational Inertia ◽  
Adiabatic Flow ◽  
Thrust Bearings ◽  
Adiabatic Theory ◽  
Bearing Life ◽  
Load Carrying ◽  
Effects Of Temperature

The effects of the lubricant rotational inertia and the temperature on the performance of parallel stepped hydrostatic thrust bearings have been investigated. Expressions for pressure and temperature distributions and load carrying capacities are obtained under adiabatic flow conditions. Satisfactory correlation between theory and experiment has been observed especially when the bearing speed is high. In order to insure the increase of load capacity as speed increases, the ratio of step location to bearing radius must be chosen no less than a limiting value which depends on the other geometry and operating conditions of the bearing. Since the bearing performance estimation by adiabatic theory is conservative, the design criteria provided will be practical and useful if long bearing life is essential.

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