Thermal Drift of Floated Gyroscopes

1957 ◽  
Vol 24 (4) ◽  
pp. 506-508
Author(s):  
L. E. Goodman ◽  
A. R. Robinson
Keyword(s):  
Temperature Distribution ◽  
Thermal Effects ◽  
Gravitational Force ◽  
Drift Rate ◽  
Force Convection ◽  
Thermal Drift ◽  
Plane Parallel

Abstract When a floated gyroscope is subjected to a temperature distribution which is not symmetrical about a plane parallel to the gravitational force, convection currents tend to rotate the gimbal. The rebalance torque and the free drift rate due to thermal effects are first determined for the case of an exactly centered gimbal. It is then shown that moderate gimbal eccentricity has little influence on thermal drift, and, in fact, reduces thermal rebalance torque.

scholarly journals A TWO-DIMENSIONAL THERMODYNAMIC MODEL TO PREDICT HEART THERMAL RESPONSE DURING OPEN CHEST PROCEDURES

2016 ◽  
Vol 15 (1) ◽  
pp. 44
Author(s):  
F. G. Dias ◽  
J. V. C. Vargas ◽  
M. L. Brioschi
Keyword(s):  
Cardiac Surgery ◽  
Temperature Distribution ◽  
Thermodynamic Model ◽  
Thermal Effects ◽  
Computational Simulation ◽  
Thermal Response ◽  
Cardiac Response ◽  
The Finite Element Method ◽  
Thermal Distribution ◽  
Open Chest

In this work, the temperature distribution of the heart in an open chest surgery scenario is studied. It is also evaluated the cardiac thermal effects of the injection of a cooling liquid in the aorta root, which is used in infrared thermography. The finite element method was used to develop a model that predicts the temperature distribution modification in a 2-dimensional slice of the heart. This thermodynamic model allows the computational simulation of the thermal cardiac response to open chest procedures, which are required by cardiac surgery. The influence of several operating parameters (e.g., coronary flow rate, temperature) on the resulting thermal distribution is analyzed. Therefore, this analysis allows the identification of parameters that could be controlled to minimize the loss of energy, and consequently, avoiding the hazardous thermal distribution that could put the heart in danger during cardiac surgery.

Characterization and Correction of Geometric Errors Induced by Thermal Drift in CT Measurements

2014 ◽  
Vol 613 ◽  
pp. 327-334 ◽  
Author(s):  
Fabrício Borges de Oliveira ◽  
Maurício de Campos Porath ◽  
Vitor Camargo Nardelli ◽  
Francisco Augusto Arenhart ◽  
Gustavo Daniel Donatelli
Keyword(s):  
Thermal Effects ◽  
Displacement Vector ◽  
Relative Displacement ◽  
Correction Method ◽  
Thermal Drift ◽  
X Ray ◽  
Ct Measurements ◽  
Industrial Computed Tomography ◽  
Roundness Deviation ◽  
Source Of Error

The occurrence of thermal drift in industrial computed tomography (CT) systems has been reported as a significant source of error on geometrical evaluations. During CT-scans, heating inside the cabinet and varying environmental conditions may affect the position of the focal spot and distort the manipulator system, leading to relative displacement of X-ray projections and distortions in the reconstructed 3D image. This paper presents an experimental investigation on influence of the thermal effects on dimensional CT measurements. A correction method based on the manipulation of the projections was developed and evaluated. The method consists in repeating the acquisition of first projection at the end of the scan and calculating the displacement vector between these projections. The remaining projections are then corrected proportionally to this displacement. The results showed a significant reduction of the roundness deviation values measured on a precision sphere after the correction.

Analysis of Microheat Pipes With Axial Conduction in the Solid Wall

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Yew Mun Hung ◽  
Kek-Kiong Tio
Keyword(s):  
Temperature Distribution ◽  
Heat Transport ◽  
Thermal Effects ◽  
Solid Wall ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Working Fluid ◽  
Transport Capacity ◽  
Axial Temperature ◽  
Energy Equations

A one-dimensional, steady-state model of a triangular microheat pipe (MHP) is developed, with the main purpose of investigating the thermal effects of the solid wall on the heat transport capacity of an MHP. The energy equation of the solid wall is solved analytically to obtain the axial temperature distribution, the average of which over the entire length of the MHP is simply its operating temperature. Next, the liquid phase is coupled with the solid wall by a heat transfer coefficient. Then, the continuity, momentum, and energy equations of the liquid and vapor phases are, together with the Young–Laplace equation, solved numerically to yield the heat and fluid flow characteristics of the MHP. The heat transport capacity and the associated optimal charge level of the working fluid are predicted for different operating conditions. Comparison between the models with and without a solid wall reveals that the presence of the solid wall induces a change in the phase change heat transport by the working fluid, besides facilitating axial heat conduction in the solid wall. The analysis also highlights the effects of the thickness and thermal conductivity of the solid wall on its axial temperature distribution. Finally, while the contribution of the thermal effects of the solid wall on the heat transport capacity of the MHP is usually not dominant, it is, nevertheless, not negligible either.

Thermoelastic Whirling Analysis of Cylinders During Grinding

2009 ◽  
Author(s):  
Erno Keskinen ◽  
Timo Karvinen ◽  
Vladimir Dospel ◽  
Mika To¨ho¨nen ◽  
Teppo Syrja¨nen ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Thermal Effects ◽  
Time Integration ◽  
Interaction Mechanism ◽  
Thermoelastic Problem ◽  
Work Piece ◽  
Bending Vibrations ◽  
Thermal Deformations ◽  
Eigenfunction Basis ◽  
Modal Coordinates

Cylinder grinding has been the subject for an intensive research, because delay-type resonances, commonly known as chatter-vibrations, have been reason for serious surface quality problems in industry [1]. As a result of this activity there is available a simulation platform, on which the complete grinding process including delay-resonances can be driven [2]. This platform consists of models for the grinder, for the cylindrical work piece and for the stone-cylinder grinding contact. The elastic cylinder model is based on analytical eigenfunctions in bending vibrations, which basis has been used to present the rotordynamic equations of cylinder in modal coordinates. Stone-cylinder interaction mechanism has been derived by combining the rules of mass and momentum transfer in the material removal process. The contribution of this paper is to update the platform to include the thermal effects of the work body. Following the method to use the eigenfunctions of a non-supported beam to describe the rotordynamic motion of the work body, a promising method could be to use in a similar way the eigenfunctions of a thermally isolated cylinder to solve the temperature distribution of the cylinder. The temperature distribution and terms related to the non-homogeneous boundary conditions will then be the input to the thermoelastic problem. It can be shown that the eigenfunction basis consists of trigonometric functions in axial and circumferential directions while the radial eigenfunctions are Bessel functions. The stone-cylinder interface has to be updated also to include thermal effects. A portion of the mechanical power is transferred to the work piece. The rest goes to the stone, to the material, which is removed and to the cutting coolant. On the other hand, thermal deformations modify the grinding forces, which are loading the work piece. The solution of the coupled thermal and thermoelastic problem will be done in terms of modal coordinates corresponding to the eigenfunction basis. This leads to numerical time integration of two groups of differential equations, the solution of which can be used to perform the temperature distributions and the corresponding thermal deformations.

scholarly journals A New High-Precision Correction Method of Temperature Distribution in Model Stellar Atmospheres

2013 ◽  
Vol 22 (2) ◽  
Author(s):  
A. Sapar ◽  
R. Poolamäe ◽  
L. Sapar
Keyword(s):  
Temperature Distribution ◽  
High Precision ◽  
Linear Optimization ◽  
Correction Method ◽  
Stellar Model ◽  
Temperature Correction ◽  
Stellar Atmospheres ◽  
Local Source ◽  
Plane Parallel ◽  
Iteration Loop

AbstractThe main features of the temperature correction methods, suggested and used in modeling of plane-parallel stellar atmospheres, are discussed. The main features of the new method are described. Derivation of the formulae for a version of the Unsöld-Lucy method, used by us in the SMART (Stellar Model Atmospheres and Radiative Transport) software for modeling stellar atmospheres, is presented. The method is based on a correction of the model temperature distribution based on minimizing differences of flux from its accepted constant value and on the requirement of the lack of its gradient, meaning that local source and sink terms of radiation must be equal. The final relative flux constancy obtainable by the method with the SMART code turned out to have the precision of the order of 0.5 %. Some of the rapidly converging iteration steps can be useful before starting the high-precision model correction. The corrections of both the flux value and of its gradient, like in Unsöld-Lucy method, are unavoidably needed to obtain high-precision flux constancy. A new temperature correction method to obtain high-precision flux constancy for plane-parallel LTE model stellar atmospheres is proposed and studied. The non-linear optimization is carried out by the least squares, in which the Levenberg-Marquardt correction method and thereafter additional correction by the Broyden iteration loop were applied. Small finite differences of temperature (

Research on Cooling Action and Simulation of Temperature Distribution with Water Vapor as Coolants and Lubricants in Green Cutting

2007 ◽  
Vol 10-12 ◽  
pp. 276-280
Author(s):  
Jun Yan Liu ◽  
Rong Di Han ◽  
Yang Wang
Keyword(s):  
Water Vapor ◽  
Temperature Distribution ◽  
Metal Cutting ◽  
Cutting Temperature ◽  
Convection Heat Transfer ◽  
Force Convection ◽  
The Finite Element Method ◽  
Convection Heat Transfer Coefficient ◽  
Dry Cutting ◽  
Vapor Lubrication

Water vapor is a good, pollution-free and economical coolants and lubricants in green machining. In order to research the cutting temperature distributions with water vapor as coolants and lubricants in machining, the experiments conducted under the conditions of water vapor as coolants and lubricants and dry cutting. The cutting temperatures are studied by metal cutting theory, and then by employing the finite element method (FEM), the temperature distribution of cutting region is simulated with application of water vapor as coolants and lubricants and dry cutting conditions. The results show that the water vapor jet flow has high force-convection heat transfer coefficient and directly cooling action to reduce cutting temperature, and the stress, the length of tool-chip interface are reduced with application of water vapor lubrication. So that the cutting thermal is decreased and water vapor has indirect cooling action. Under the conditions of indirect and direct cooling action, the cutting temperature is reduced obviously with application of water vapor as coolants and lubricants.

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