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Transient temperature distributions in simple conducting bodies steadily heated through a laminar boundary layer

Description: "An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero" (p. 1).
Date: December 1953
Creator: Parker, Hermon M.
Partner: UNT Libraries Government Documents Department

Simple Conduction Model with Phase Change for Fuel Pin

Description: A simple conduction model with phase change has been developed for the transient analysis of a fuel pin based on average properties and lumped-parameter techniques. The transient behavior of fuel and cladding can be accurately described by simple analytical expressions that agree with conventional numerical approaches for under-cooling transient analysis. If it be assumed that the heat-transfer resistance between the fuel and cladding remains the same for both steady-state and transient periods, the phase-change problem for fuel and cladding melting can be significantly simplified. BY using the predetermined average overall heat-transfer coefficient across a fuel pin in the steady-state period, the average transient fuel and cladding temperatures can be formulated analytically. For loss of flow at constant power, the start of melting and complete melting for both the fuel and cladding can be estimated with considerable accuracy.
Date: April 1976
Creator: Chen, W. L.; Ishii, M. & Grolmes, M. A.
Partner: UNT Libraries Government Documents Department

Errors in skin temperature measurements.

Description: Numerical simulation is used to investigate the accuracy of a direct-contact device for measuring skin-surface temperature. A variation of thermal conductivity of the foam has greater effect on the error rather than a variation of the blood perfusion rate. For a thermal conductivity of zero, an error of 1.5 oC in temperature was identified. For foam pad conductivities of 0.03 and 0.06 W/m-oC, the errors are 0.5 and 0.15 oC. For the transient study, with k=0 W/m-oC, it takes 4,900 seconds for the temperature to reach steady state compared with k=0.03 W/m-oC and k=0.06 W/m-oC where it takes 3,000 seconds. The configuration without the foam and in presence of an air gap between the skin surface and the sensor gives the most uniform temperature profile.
Date: December 2008
Creator: Dugay, Murielle
Partner: UNT Libraries

Reduced order models for thermal analysis : final report : LDRD Project No. 137807.

Description: This LDRD Senior's Council Project is focused on the development, implementation and evaluation of Reduced Order Models (ROM) for application in the thermal analysis of complex engineering problems. Two basic approaches to developing a ROM for combined thermal conduction and enclosure radiation problems are considered. As a prerequisite to a ROM a fully coupled solution method for conduction/radiation models is required; a parallel implementation is explored for this class of problems. High-fidelity models of large, complex systems are now used routinely to verify design and performance. However, there are applications where the high-fidelity model is too large to be used repetitively in a design mode. One such application is the design of a control system that oversees the functioning of the complex, high-fidelity model. Examples include control systems for manufacturing processes such as brazing and annealing furnaces as well as control systems for the thermal management of optical systems. A reduced order model (ROM) seeks to reduce the number of degrees of freedom needed to represent the overall behavior of the large system without a significant loss in accuracy. The reduction in the number of degrees of freedom of the ROM leads to immediate increases in computational efficiency and allows many design parameters and perturbations to be quickly and effectively evaluated. Reduced order models are routinely used in solid mechanics where techniques such as modal analysis have reached a high state of refinement. Similar techniques have recently been applied in standard thermal conduction problems e.g. though the general use of ROM for heat transfer is not yet widespread. One major difficulty with the development of ROM for general thermal analysis is the need to include the very nonlinear effects of enclosure radiation in many applications. Many ROM methods have considered only linear or mildly nonlinear problems. In the present study ...
Date: September 1, 2010
Creator: Hogan, Roy E., Jr. & Gartling, David K.
Partner: UNT Libraries Government Documents Department

Response of removable epoxy foam exposed to fire using an element death model.

Description: Response of removable epoxy foam (REF) to high heat fluxes is described using a decomposition chemistry model [1] in conjunction with a finite element heat conduction code [2] that supports chemical kinetics and dynamic radiation enclosures. The chemistry model [1] describes the temporal transformation of virgin foam into carbonaceous residue by considering breakdown of the foam polymer structure, desorption of gases not associated with the foam polymer, mass transport of decomposition products from the reaction site to the bulk gas, and phase equilibrium. The finite element foam response model considers the spatial behavior of the foam by using measured and predicted thermophysical properties in combination with the decomposition chemistry model. Foam elements are removed from the computational domain when the condensed mass fractions of the foam elements are close to zero. Element removal, referred to as element death, creates a space within the metal confinement causing radiation to be the dominant mode of heat transfer between the surface of the remaining foam elements and the interior walls of the confining metal skin. Predictions were compared to front locations extrapolated from radiographs of foam cylinders enclosed in metal containers that were heated with quartz lamps [3,4]. The effects of the maximum temperature of the metal container, density of the foam, the foam orientation, venting of the decomposition products, pressurization of the metal container, and the presence or absence of embedded components are discussed.
Date: September 1, 2004
Creator: Hobbs, Michael L.
Partner: UNT Libraries Government Documents Department

Evaluation of the Use of Existing RELAP5-3D Models to Represent the Actinide Burner Test Reactor

Description: The RELAP5-3D code is being considered as a thermal-hydraulic system code to support the development of the sodium-cooled Actinide Burner Test Reactor as part of Global Nuclear Energy Partnership. An evaluation was performed to determine whether the control system could be used to simulate the effects of non-convective mechanisms of heat transport in the fluid that are not currently represented with internal code models, including axial and radial heat conduction in the fluid and subchannel mixing. The evaluation also determined the relative importance of axial and radial heat conduction and fluid mixing on peak cladding temperature for a wide range of steady conditions and during a representative loss-of-flow transient. The evaluation was performed using a RELAP5-3D model of a subassembly in the Experimental Breeder Reactor-II, which was used as a surrogate for the Actinide Burner Test Reactor. An evaluation was also performed to determine if the existing centrifugal pump model could be used to simulate the performance of electromagnetic pumps.
Date: February 1, 2007
Creator: Davis, C. B.
Partner: UNT Libraries Government Documents Department