Thermal response of superfluid4He nearT λ to an AC heat flux

1997 ◽  
Vol 109 (5-6) ◽  
pp. 801-810
Author(s):  
Daniel Murphy ◽  
Horst Meyer
Keyword(s):  
Heat Flux ◽  
Thermal Response

Thermal response of plasma sprayed tungsten coating to high heat flux

2004 ◽  
Vol 70 (4) ◽  
pp. 341-349 ◽  
Author(s):  
X. Liu ◽  
L. Yang ◽  
S. Tamura ◽  
K. Tokunaga ◽  
N. Yoshida ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal Response ◽  
High Heat ◽  
High Heat Flux ◽  
Tungsten Coating ◽  
Plasma Sprayed

Experimental Validation of Non-Fourier Thermal Response in Porous Media

2001 ◽  
Author(s):  
A. G. Agwu Nnanna ◽  
K. T. Harris ◽  
A. Haji-Sheikh
Keyword(s):  
Heat Flux ◽  
Porous Media ◽  
Experimental Validation ◽  
Thermal Response ◽  
Lag Time ◽  
Equation Model ◽  
Thermal Parameters ◽  
Solid Matrix ◽  
Microscale Model ◽  
Short Time

Abstract An experimental validation of non-Fourier behavior in porous media due to short time thermal perturbation is presented. The governing energy equation is formulated based on the two-equation model and the non-Fourier model. This formulation leads to the emergence of four thermal parameters: lag-time in heat flux τq, lag-time τt in temperature due to interstitial heat transfer coefficient h, and lag-time in the transient response of the temperature gradient τx in the heat flux equation. These parameters account for the microstructural thermal interaction between the fluid and neighboring solid matrix as well as the delay time needed for both phases to approach thermal equilibrium. An experimental verification of the microscale model was performed under standard laboratory conditions. The values of the aforementioned thermal parameters were determined to compute the fluid and solid temperatures. Results predicted from three models (classical Fourier, non-Fourier, and experimental) were compared. It indicates an excellent agreement between the non-Fourier and the experimental model, and a significant deviation of Fourier prediction from the experimental results.

Two-dimensional hybrid analytical approach for the investigation of thermal aspects in human tissue undergoing regional hyperthermia therapy

2020 ◽  
Vol 234 (20) ◽  
pp. 3951-3966
Author(s):  
Jaideep Dutta ◽  
Balaram Kundu
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Cancer Treatment ◽  
Thermal Response ◽  
Skin Tissue ◽  
Hyperbolic Heat Conduction ◽  
Two Dimensional ◽  
Regional Hyperthermia ◽  
Hyperthermia Therapy ◽  
The Impact

The formation of the present work is based on the development of the exact analytical solution of two-dimensional temperature response by employing the hyperbolic heat conduction bioheat model in a single-layered human skin tissue subjected to the regional hyperthermia therapy (RHT) for cancer treatment. The mathematical approach has been utilized as a hybrid form of ‘separation of variables’ and ‘finite integral transform’ method. Three kinds of surface heat fluxes (constant, sinusoidal and cosine) have been employed as an external heat source on the therapeutic surface of the square-shaped skin tissue of 100 mm × 100 mm. An innovative form of initial condition (spatially dependent) has been implemented in the present mathematical formulation as skin tissues are highly non-homogeneous and non-uniform in structure. The present research outcome indicates that cosine heat flux would be a suitable alternative for the sinusoidal heat flux. The impact of the relaxation time lag has been clearly noted in the thermal response with the waveform-like behaviour and it justifies the postulate of hyperbolic heat conduction. The two-dimensional temperature of the skin tissue has been observed in the range of 48.1 ℃–40 ℃ (in decreasing order). Estimated peak temperatures are in the proposed spectrum of hyperthermia therapy for an exposure time of 100 s, and this fact is true in an agreement with the medical protocol of the cancer treatment. The accuracy of the mathematical modelling and in-house computer codes are justified with the published numerical models and the maximum deviation of the thermal response has been noticed in order of 1.5–3%. The two-dimensional surface thermal contours have provided a glimpse of heat flow in the physical domain of skin tissue under different heating conditions and this research output may be beneficial to establish the theoretical standard of the regional hyperthermia treatment for cancer eradication.

scholarly journals The Roseville Bomb Disaster Simulated Train Braking System Tests and Boxcar Wood Floor Ignition Experiments

1991 ◽  
Vol 113 (1) ◽  
pp. 91-99
Author(s):  
B. Ross ◽  
P. G. Parikh
Keyword(s):  
Heat Flux ◽  
Cast Iron ◽  
Ignition Time ◽  
Thermal Response ◽  
Radiant Heat ◽  
Full Scale ◽  
Test Facility ◽  
Shield Effectiveness ◽  
Wood Floor ◽  
Wood Surfaces

A massive chain of property damaging explosions involving an ammunition train occurred at the railroad yard, Roseville, California. The train had pulled into the yard after a night trip of some 100 miles across Donner Summit and down the extended Norden-Roseville grade. Physical evidence confirmed that first explosions were centered at a DODX type boxcar loaded with 250 lb. bombs. Further, bomb cook-off detonation tests established that the triggering bomb blast was not a result of shock loads but rather derived from an engulfing fire initiated in the boxcar wood plank floor under influence of extended heavy braking action on the mountain grade. It was also suspected that high friction composition brake shoes were fitted on the car as replacements for cast iron shoes but the brake mechanical linkage lever ratios had not been modified as required. Results of a comprehensive research program are presented within context of the explosion event, and include analytical computer simulation of train descent profiles on mountain grades through full scale dynamometer tests with actual rail wheels and ultimately more scientific scaled wood floor ignition experiments in the laboratory. The thermal response of a simulated DODX boxcar wood floor was studied through experiments, full scale at a rail wheel dynamometer test facility, and in the laboratory. Certain input data for the wood floor ignition test program were measured on an actual boxcar joined with a freight train consist in transit down the Norden-Roseville grade. Two series of scaled wood ignition experiments were conducted on simulated DODX boxcar floors. Objectives of these tests were to determine: Influence of a cooling air stream on the ignition behavior of radiantly heated wood surfaces, and effectiveness of DODX (stand-off) and AAR (flush) type spark shields in preventing ignition of wood surfaces under radiant heating. It was found that for radiant heat flux levels representative of high friction composition shoes under severe train braking conditions, low speed airflow (wind) exerts a dramatic influence on the wood ignition time. For example, average ignition time for a simulated boxcar floor at a heat flux level of 0.4 cal/cm2sec was determined to be 15.6 min. with a 5 mph wind as compared to 3.6 min. with no wind. In the spark shield effectiveness tests, conducted at heat flux levels representative of cast iron shoes under severe braking conditions, the DODX (stand-off) type spark shield failed to prevent spontaneous flaming ignition of a wood surface directly above it. Under identical conditions, no flaming ignition was encountered with the AAR (flush) type spark shield.

Transient Heat Transfer for Laminar Forced Convection in the Thermal Entrance Region of Flat Ducts

1959 ◽  
Vol 81 (1) ◽  
pp. 29-36 ◽  
Author(s):  
R. Siegel ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady State ◽  
Thermal Response ◽  
Step Function ◽  
Entrance Region ◽  
Arbitrary Time ◽  
Unit Step ◽  
Thermal Entrance Region ◽  
Thermal Entrance

An analysis is made for transient laminar heat transfer in the thermal entrance region of a flat duct (parallel plate channel) whose bounding surfaces are subjected to an arbitrary time variation of temperature or of heat flux. Initially, the system may be either in an already established steady-state heat-transfer situation, or else, the fluid and duct walls may be at the same uniform temperature. The velocity distribution in the flow is taken to be fully developed and unchanging with time. The solution for arbitrary time-dependent conditions is obtained by generalizing the thermal response to a unit step change in wall temperature or in wall heat flux. This step-function response is found by using the method of characteristics. Heat-transfer results are presented as simple analytical expressions. The time required to achieve steady state after a unit step is also given. Working formulas are summarized at the end of the paper.

Flammability Parameters of Materials: Ignition, Combustion, and Fire Propagation

1994 ◽  
Vol 12 (4) ◽  
pp. 329-356 ◽  
Author(s):  
A. Tewarson
Keyword(s):  
Heat Flux ◽  
Heat Release ◽  
Critical Heat Flux ◽  
Thermal Response ◽  
Fire Propagation ◽  
Flammability Parameters ◽  
Param Eters

In this paper, flammability parameters associated with the igni tion, combustion, and fire propagation processes and their usefulness for the development of fire resistant materials are discussed. The flammability param eters discussed are: (a) Critical Heat Flux (CHF) and Thermal Response Param eter (TRP), associated with ignition, (b) Heat Release Parameter (HRP) and Fire Propagation Index (FPI), associated with combustion and fire propagation.

Thermal response of normal and superfluid helium to an AC heat flux

1994 ◽  
Vol 194-196 ◽  
pp. 595-596
Author(s):  
J.S. Olafsen ◽  
R.P. Behringer
Keyword(s):  
Heat Flux ◽  
Superfluid Helium ◽  
Thermal Response

Coupling of Large Fire Phenomenon with Object Geometry and Object Thermal Response

1997 ◽  
Vol 15 (6) ◽  
pp. 427-442 ◽  
Author(s):  
Louis A. Gritzo ◽  
Vernon F. Nicolette
Keyword(s):  
Heat Flux ◽  
Numerical Simulations ◽  
Thermal Response ◽  
Relative Influence ◽  
Radiative Cooling ◽  
Large Fire ◽  
Flame Zone ◽  
Radiative Coupling ◽  
Flow Mixing ◽  
Combustion Processes

The effect of an object in or near a large fire on the physical pro cesses which result in the heat flux from the fire is defined by the object geometry and temperature, and therefore the fire phenomena and the object physical states can be coupled. Two primary modes of coupling, radiative and convective, and their relative influence on heat flux, are investigated using observations from ex perimental data and numerical simulations. Radiative coupling occurs when a comparatively cold object reduces the incident heat flux (by up to 65%) due to radiative cooling of nearby media. Convective coupling includes: (1) changes in the geometry of the flame zone, and (2) object-induced turbulence which alters and often enhances the flow, mixing, and, hence, combustion processes within the fire. Increases in the heat flux approaching a factor of three have been observed due to these phenomena.

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