Estimation of the Mean Temperature Distribution Underneath a Slab-on-ground Structure

2005 ◽  
Vol 29 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Jukka Rantala
1983 ◽  
Vol 105 (4) ◽  
pp. 789-794 ◽  
Author(s):  
M. Kaviany ◽  
R. Seban

The one-equation model of turbulence is applied to the turbulent thermal convection between horizontal plates maintained at constant temperatures. A pseudo-three-layer model is used consisting of a conduction sublayer adjacent to the plates, a turbulent region within which the mixing length increases linearly, and a turbulent core within which the mixing length is a constant. It is assumed that the Nusselt number varies with the Rayleigh number to the one-third power. As a result, the steady-state distributions of the turbulent kinetic energy and the mean temperature are obtrained and presented in closed forms. These results include the effects of Prandtl number. The predictions are compared with the available experimental results for different Prandtl and Rayleigh numbers. Also included are the predictions of Kraichnan, which are based on a less exact analysis. The results of the one-equation model are in fair agreement with the experimental results for the distribution of the turbulent kinetic energy and the mean temperature distribution. The predictions of Kraichnan are in better agreement with the experimental results for the mean temperature distribution.


1973 ◽  
Vol 60 (1) ◽  
pp. 141-159 ◽  
Author(s):  
T. Y. Chu ◽  
R. J. Goldstein

Overall heat transfer and mean temperature distribution measurements have been made of turbulent thermal convection in horizontal water layers heated from below. The Nusselt number is found to be proportional to Ra0·278 in the range 2·76 × 105 < Ra < 1·05 × 108. Eight discrete heat flux transitions are found in this Rayleigh number range. An interferometric method is used to measure the mean temperature distribution for Rayleigh numbers between 3·11 × 105 and 1·86 × 107. Direct visual and photographic observations of the fluctuating interferogram patterns show that the main heat transfer mechanism is the release of thermals from the boundary layers. For relatively low Rayleigh numbers (up to 5 × 105) many of the thermals reach the opposite surface and coalesce to form large masses of relatively warm fluid near the cold surface and masses of cold fluid near the warm surface, resulting in a temperature-gradient reversal. With increasing Rayleigh numbers, fewer and fewer thermals reach the opposite bounding surface and the thermals show persistent horizontal movements near the bounding surfaces. The central region of the layer becomes an isothermal core. The mean temperature distributions for the high Rayleigh number range are found to follow a Z−2 power law over a considerable range, where Z is the distance from the bounding surface. A very limited agreement with the theoretically predicted Z−1 power law is also found.


2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Kamiar Ghoseiri ◽  
Mostafa Allami ◽  
Justin R. Murphy ◽  
Phillip Page ◽  
Duane C. Button

BACKGROUND: Interventions to resolve thermal discomfort as a common complaint in amputees are usually chosen based on the residual limb skin temperature while wearing prosthesis; whereas, less attention has been paid to residual limb skin temperature while outside of the prosthesis. The objective of this study was to explore the localized and regional skin temperature over the transtibial residual limb (TRL) while outside of the prosthesis. METHODOLOGY: Eight unilateral transtibial adults with traumatic amputation were enrolled in this cross-sectional study. Participants sat to remove their prostheses and rested for 30 minutes. Twelve sites were marked circumferentially in four columns (anterolateral, anteromedial, posteromedial, and posterolateral) and longitudinally in three rows (proximal, middle, and distal) over the residual limb and used for attachment of analog thermistors. Skin temperature was recorded and compared for 11 minutes. Furthermore, the relationship of skin temperature with participants’ demographic and clinical characteristics was explored. FINDINGS: The whole temperature of the TRL was 27.73 (SD=0.83)°C. There was a significant difference in skin temperature between anterior and posterior columns. Likewise, the distal row was significantly different from the proximal and middle rows. The mean temperature at the middle and distal zones of the anteromedial column had the highest and lowest skin temperatures (29.8 and 26.3°C, p<0.05), respectively. The mean temperature of the whole TRL had no significant relationships (p>0.05) with participants’ demographic and clinical characteristics. CONCLUSIONS: An unequal distribution of temperature over the TRL was found with significantly higher and lower temperatures at its anterior column and distal row, respectively. This temperature pattern should be considered for thermoregulation strategies. Further investigation of the residual limb temperature with and without prosthesis, while considering muscles thickness and blood perfusion rate is warranted. Layman's Abstract The socket is a plastic hard-shell interface between the residual limb, the remaining part of the amputated limb, and a prosthesis. Heat buildup inside the prosthetic socket and perspiration of the residual limb are major discomforts in amputees when wearing a prosthesis. The majority of prior research measured residual limb skin temperature while the prosthesis was worn. However, less attention has been paid to skin temperature without prostheses. Skin temperature of eight adults with one-sided traumatic below-knee amputation was measured. Participants sat and removed their prostheses. Twelve anatomical sites were marked circumferentially in four columns and longitudinally in three rows over the residual limb and used for temperature recording using temperature sensors. The whole temperature of the residual limb was 27.73 (SD=0.83)°C. Skin temperature was higher at anterior columns compared to posterior columns. Similarly, the distal row of the residual limb had the lowest temperature compared to its middle and proximal rows. From a localized standpoint, the middle part at the anterior medial surface of the residual limb had the highest temperature, whereas the distal part at the anterior-medial surface had the lowest skin temperature. There was no noticeable relationship between the average of the residual limb skin temperature and participants’ demographic and clinical characteristics. Some strategies need to be developed to regulate and control heat dissipation over the residual limb's surface when amputees do not wear prostheses. Further temperature recording research by considering muscle thickness and arterial blood flow rate of the residual limb with and without prosthesis is suggested. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/35070/27313 How To Cite: Ghoseiri K, Allami M, Murphy J.R, Page P, Button D.C. Investigation of localized skin temperature distribution across the transtibial residual limb. Canadian Prosthetics & Orthotics Journal. 2021;Volume 4, Issue 1, No.2. https://doi.org/10.33137/cpoj.v4i1.35070 Corresponding Author: Duane C Button, PhDSchool of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada.E-mail: [email protected]: https://orcid.org/0000-0001-6402-8545    


Author(s):  
Michael Betz ◽  
Max Zahn ◽  
Christoph Hirsch ◽  
Thomas Sattelmayer

Abstract The results of an experimental study on the influence of the purge air mass flow and the acoustic pressure in an annular combustor test rig on the temperature distribution in resonators with perforated plates at the exit are provided in the paper. The amplitude of the acoustic pressure in the combustor is found to have a high impact on the mean temperature and thus on the performance of the resonators, which originates primarily from the temperature sensitivity of the effective eigenfrequency. In the experiments the temperature in the cavity of one of the resonators is spatially and temporally resolved at 13 locations. The dependence of the mean temperature change on the combustor amplitudes and the purge air mass flow is measured quantitatively. In addition, the axial temperature gradient of the resonator is resolved. The mean temperature changes up to 8% depending on the level of siren forcing. Using acoustic pressure data from the cavity, the velocity of the hot gas jets periodically entering the resonator is calculated. If high amplitudes occur in the combustor and there is no adequate purge air flow in the resonators then hot gas ingestion into the cavity of the resonator occurs, leading to detuning of the resonator and the breakdown of its performance. Once hot gas ingestion occurs, the resonator quickly heats up within a few seconds as the generation of the mixture of hot gas and purge air requires only a low number of cycles. This leads to a thermal runaway of the frequency range of the resonator with high damping. When the combustor returns to quiet operation, a cooling phase with two different time constants is observed.


Nature ◽  
1940 ◽  
Vol 145 (3665) ◽  
pp. 148-148
Author(s):  
C. BENEDICKS ◽  
P. SEDERHOLM
Keyword(s):  

1988 ◽  
Vol 110 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Da Yu Tzou

Stochastic temperature distribution in a solid medium with random heat conductivity is investigated by the method of perturbation. The intrinsic randomness of the thermal conductivity k(x) is considered to be a distribution function with random amplitude in the solid, and several typical stochastic processes are considered in the numerical examples. The formulation used in the present analysis describes a situation that the statistical orders of the random response of the system are the same as those of the intrinsic random excitations, which is characteristic for the problem with extrinsic randomness. The maximum standard deviation of the temperature distribution from the mean value in the solid medium reveals the amount of unexpected energy experienced by the solid continuum, which should be carefully inspected in the thermal-failure design of structures with intrinsic randomness.


1983 ◽  
Vol 105 (3) ◽  
pp. 592-597 ◽  
Author(s):  
A. Pignotti ◽  
G. O. Cordero

Computer generated graphs are presented for the mean temperature difference in typical air cooler configurations, covering the combinations of numbers of passes and rows per pass of industrial interest. Two sets of independent variables are included in the graphs: the conventional one (heat capacity water ratio and cold fluid effectiveness), and the one required in an optimization technique of widespread use (hot fluid effectiveness and the number of heat transfer units). Flow arrangements with side-by-side and over-and-under passes, frequently found in actual practice, are discussed through examples.


1966 ◽  
Vol 44 (10) ◽  
pp. 1285-1292 ◽  
Author(s):  
David W. Smith ◽  
John H. Sparling

The temperatures of 18 fires in an open jack pine barren near Timmins, Ontario, have been recorded. The maximum temperature recorded was 545 °C, although in other determinations fire temperatures in excess of 1000 °C were reached. The mean temperature of all fires was 340.6 ± 133.2 °C. Three fires at 230, 345, and 545 °C were considered in detail.The maximum temperature of a fire was normally recorded at heights of 5 cm or 10 cm above the surface. Maximum temperatures of hotter fires usually occurred at greater heights than cooler ones. Duration and the temperature ("intensity") of the fire are important aspects of fire studies.


2014 ◽  
Vol 919-921 ◽  
pp. 1707-1715
Author(s):  
Ya Su Zhou ◽  
Wan Lan Ju ◽  
Zheng Liu

The initial ground temperature (IGT) is one of the most important parameters in designing a ground source heat pump (GSHP) system and evaluating its performance. In this paper, three initial ground temperature test methods are introduced. Except the shallow zone, the ground temperature distribution measured from direct and indirect testing method has very small difference. In direct test, the temperature sensor must be embedded when burying the tube in the borehole which is hard to operate in engineering applications. Thus the direct testing method is suggested to be applied in the scientific research. The indirect testing method could be used in engineering applications. The mean ground temperature could be calculated from temperature distribution except the shallow zone temperature. The results from three calculating methods have a quite small difference. Therefore, the arithmetic average method is suggested for scientific and engineering application to calculate the mean ground temperature. The mean ground temperature is also gotten in TRT conveniently. In the condition of velocity 0.7m/s, water was circulated in the tube system with no heat source for 30 minutes. The average water temperature could be regard as the mean ground temperature with sufficient accuracy.


Author(s):  
Todd A. Oliver ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Robert D. Moser ◽  
Gregory Laskowski

Results of a recent joint experimental and computational investigation of the flow through a plenum-fed 7-7-7 shaped film cooling hole are presented. In particular, we compare the measured adiabatic effectiveness and mean temperature against implicit large eddy simulation (iLES) for blowing ratio approximately 2, density ratio 1.6, and Reynolds number 6000. The results overall show reasonable agreement between the iLES and the experimental results for the adiabatic effectiveness and gross features of the mean temperature field. Notable discrepancies include the centerline adiabatic effectiveness near the hole, where the iLES under-predicts the measurements by Δη ≈ 0.05, and the near-wall temperature, where the simulation results show features not present in the measurements. After showing this comparison, the iLES results are used to examine features that were not measured in the experiments, including the in-hole flow and the dominant fluxes in the mean internal energy equation downstream of the hole. Key findings include that the flow near the entrance to the hole is highly turbulent and that there is a large region of backflow near the exit of the hole. Further, the well-known counter-rotating vortex pair downstream of the hole is observed. Finally, the typical gradient diffusion hypothesis for the Reynolds heat flux is evaluated and found to be incorrect.


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