Investigation of Thermal Conductivity of a Polymer Solution as Function of Shearing Rate

1999 ◽  
Author(s):  
Milivoje Kostic ◽  
Haibo Tong
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Virtual Instrument ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Conductive Heat ◽  
Fluid Temperature ◽  
Concentric Cylinders ◽  
And Control ◽  
Measurement And Control

Abstract A novel research apparatus is developed to measure the fluid thermal conductivity while in shearing flow, and to determine its dependence on the shearing itself, contrary to the current state-of-the-art of measuring thermal conductivity under the condition of motionless fluid. A concentric cylinders’ apparatus was developed to provide controlled heat transfer in the radial direction, orthogonal to the circumferential fluid velocity, thus virtually preserving pure conductive heat transfer mode. The measurement and control are accomplished and integrated by using a computerized data acquisition system and a comprehensive virtual instrument, developed using the LabVIEW application software. It was found that the thermal conductivity of a Newtonian fluid, such as distilled water, was virtually independent of the fluid motion, as expected. However, for non-Newtonian fluids such as 1000 and 2000 wppm aqueous polyacrylamide (Praestol) solutions, there was up to 10–20% increase of thermal conductivity in the operating shear rate range (40 ≤ γ ≤ 510 sec−1) at 27°C average fluid temperature.

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.

Experimental heat transfer characteristics of a liquid in Couette motion and with Taylor vortices

1961 ◽  
Vol 261 (1305) ◽  
pp. 215-226 ◽  
Keyword(s):  
Heat Transfer ◽  
Reverse Flow ◽  
Fluid Dynamic ◽  
Fluid Motion ◽  
Heat Transfer Characteristics ◽  
Radial Temperature ◽  
Transfer Characteristics ◽  
Experimental Heat ◽  
Concentric Cylinders ◽  
Primary Fluid

The heat transfer characteristics of water in rotational motion between horizontal concentric cylinders has been studied. Primary fluid motion due to rotation of the inner cylinders alone, and due to rotation of inner cylinder with reverse flow caused by a divider, has been considered experimentally for two ratios of annulus width to inner cylinder radius. The results for two geometries and two primary fluid dynamic conditions are correlated by a parameter related to the generalized stability parameter. Radial temperature profiles are given and are shown to be effective in indicating secondary flow patterns.

Software System Development of Measurement and Control System for a Nonlinear Absorber by Virtual Instrument

2011 ◽  
Vol 188 ◽  
pp. 236-240
Author(s):  
Cong Ling Zhu ◽  
Wei Zhu Jin ◽  
D.R. Ci ◽  
Zhi Gang Ding ◽  
S.T. Wu
Keyword(s):  
Control System ◽  
Virtual Instrument ◽  
System Development ◽  
System Structure ◽  
Software System ◽  
Measurement And Control System ◽  
Nonlinear Absorber ◽  
New Development ◽  
And Control ◽  
Measurement And Control

Measurement and control system is the key equipment for testing and analyzing of the dynamic characteristics for a nonlinear absorber.It is the necessary means of accomplishing to design the rationalization of the nonlinear absorber. This article has conducted the detailed research in the new development of absorber test equipment to the desing of system structure, The constituent of software system, and The process design, and The development of the computer program based on virtual techniques. Debugging and running this software system have shown that the precision and reliability of it have been proved.

Thermal Conductivity Test and Coupling Simulation of Heat-Transfer in Fracture Rock

2011 ◽  
Vol 382 ◽  
pp. 3-6
Author(s):  
Shu Guang Zhang ◽  
Yong Gang Yu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Finite Element ◽  
Temperature Field ◽  
Rock Mass ◽  
Fractured Rock ◽  
Coupling Model ◽  
Fluid Temperature ◽  
Fracture Rock ◽  
Fractured Rock Mass

In order to research thermal conductivity of fracture rock, fluid-heat coupling test and simulation are studied. Empirical equation of thermal conductivity is obtained and conductivity factor is ensured by test data. Based on the fluid-heat coupling model of heat-transfer, temperature field distribution of fracture rock is described. At the same time, the heat-transfer equation is discretized by using weighted residual Galerkin finite element. Combined with boundary condition and parameters, the temperature field in fractured rock mass is simulated by finite element method. The temperature of fractured rock mass under the action of the seepage is combined with the initial rock temperature, fluid temperature and the rate of the flow. Thermo-isoline is discontiguous at boundary of fracture, which shows that the seepage affects the distribution of temperature field. The change rate of temperture isoline is gradually reduced along the single fissure flow, therefore the rate of heat-transfer is decreased. The influence of fluid temperature to temperature distribution is small, but different fluid temperature obviously affects thermo-isoline.

scholarly journals A Way to Visualise Heat Transfer in 3D Unsteady Flows

2009 ◽  
Author(s):  
M. F. M. Speetjens
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Motion ◽  
Unsteady Flows ◽  
Unsteady Motion ◽  
Heat Fluxes ◽  
Flow Visualisation ◽  
Conductive Heat ◽  
Steady Flows ◽  
Transfer Coefficients

Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by the flow field. The paths followed by the total heat flux are the thermal counterpart to fluid trajectories and facilitate heat-transfer visualisation in a similar manner as flow visualisation. This has great potential for applications in which insight into the heat fluxes throughout the entire configuration is essential (e.g. cooling systems, heat exchangers). To date this concept has been restricted to 2D steady flows. The present study proposes its generalisation to 3D unsteady flows by representing heat transfer as the 3D unsteady motion of a virtual fluid subject to continuity. The heat-transfer visualisation is provided with a physical framework and demonstrated by way of representative examples. Furthermore, a fundamental analogy between fluid motion and heat transfer is addressed that may pave the way to future heat-transfer studies by well-established geometrical methods from laminar-mixing studies.

Thermal Conductivity Measurement of CVD Diamond Films Using a Modified Thermal Comparator Method

2000 ◽  
Vol 122 (4) ◽  
pp. 808-816 ◽  
Author(s):  
K. R. Cheruparambil ◽  
B. Farouk ◽  
J. E. Yehoda ◽  
N. A. Macken
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Calibration Curve ◽  
Thermal Contact ◽  
Diamond Films ◽  
Conductivity Measurement ◽  
Cvd Diamond ◽  
Conductive Heat ◽  
Comparator Method

Results from an experimental study on the rapid measurement of thermal conductivity of chemical vapor deposited (CVD) diamond films are presented. The classical thermal comparator method has been used successfully in the past for the measurement of thermal conductivity of bulk materials having high values of thermal resistance. Using samples of known thermal conductivity, a calibration curve is prepared. With this calibration curve, the comparator can be used to determine thermal conductivity of unknown samples. We have significantly modified and extended this technique for the measurement of materials with very low thermal resistance, i.e., CVD diamond films with high thermal conductivity. In addition to the heated probe, the modified comparator employs a thermoelectric cooling element of increase conductive heat transfer through the film. The thermal conductivity measurements are sensitive to many other factors such as the thermal contact resistances, anisotropic material properties, surrounding air currents and temperature, and ambient humidity. A comprehensive numerical model was also developed to simulate the heat transfer process for the modified comparator. The simulations were used to develop a “numerical” calibration curve that agreed well with the calibration curve obtained from our measurements. The modified method has been found to successfully measure the thermal conductivity of CVD diamond films. [S0022-1481(00)00804-5]

scholarly journals Conjugate Effect on the Thermal Characteristics of Air Impinging Jet

CFD Letters ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 25-35
Author(s):  
Ghassan Nasif ◽  
Yasser El-Okda
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Convective Heat ◽  
Thermal Characteristics ◽  
Heat Fluxes ◽  
Conductive Heat ◽  
Stagnation Region ◽  
Jet Cooling ◽  
Air Jet ◽  
Finite Volume Approach

A computational fluid dynamics (CFD) investigation to determine the conjugate heat transfer (CHT) effect on the stagnation and local thermal characteristics due to an impinging process has been carried out in this study using STAR-CCM+ - Siemens PLM commercial code. The transient Navier-Stokes’s equations are numerically solved using a finite volume approach with k-ω SST eddy viscosity as the turbulence model. A fully developed circular air jet with different Reynolds numbers, impinging vertically onto a heated flat disc with different metals, thicknesses, and boundary heat fluxes are employed in the current study to examine the thermal characteristics and provide an enhanced picture for the convection mechanism that used in jet cooling technology. It is found that the thermal characteristics are influenced by the thermal conductivity and thickness of the target upon using air as a cooling jet. The CHT process enhances the local convective heat transfer at the fluid-solid interface due to the variation in transverse and axial conductive heat transfer inside the metal up to a certain redial extent from the stagnation region compared to the process with no CHT. The extent of the radial enhancement depends on the thermal conductivity of the metal. For a given thermal conductivity, the CHT process acts to increase the temperature and convective heat flux of the stagnation region as the metal thickness increases.

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