Numerical investigations of heat transfer in single and multiple thick-walled pipes and countercurrent pairs are used to deduce relationships between fluid and solid temperatures needed to develop more accurate thermal models of living tissue in the extremities. A structural model of heat transfer in living tissue is developed using currently available anatomical and physiological data for the extremities. In order to improve the heat transfer basis of thermal modeling under in vivo conditions, four heat transfer problems based on structures found in the extremities are solved using in vivo parameters-the thick-walled pipe and countercurrent pair, and the multiple thick-walled pipes and countercurrent pairs-are studied. Low resolution numerical models are devised to approximate the thick-walled pipe and the non-concentric thick-walled countercurrent pair in square geometries. A constant heat transfer coefficient at the fluid-solid interface adequately approximates the fluid and solid temperatures for moderate flow conditions (Peclet number of 10 < °Pe < 1000). In the thick-walled countercurrent pair, countercurrent exchange and fluid-solid thermal interaction are found to act simultaneously, giving rise to imperfect countercurrent exchange. Fluid and solid temperatures in the multiple thick-walled pipes and pairs near the outer boundary resemble those of the single thick-walled pipes and pairs. The countercurrent pairs near the center also exhibit imperfect countercurrent exchange. In cylinders with L* > 1 containing multiple countercurrent pairs, the shapes of the temperature profiles cannot be distinguished from the temperature profile shapes of cylinders containing multiple thick-walled pipes. Fluid and solid temperatures in multiple parallel pipes may be approximated with a field equation which has the same form as the Pennes' bioheat equation. Unlike Pennes' equation, the coefficients for the blood thermal energy term quantify the dependence of the amount of thermal energy transferred between blood and tissue with the geometry of the blood the flow rate through the dimensionless axial length L*, and the dimensionless axial coordinate x* . Comparisons of structural model temperatures with available in vivo temperature studies show that blood and tissue temperatures are consistent with fluid and solid temperatures of either multiple unpaired pipes or multiple countercurrent pairs embedded in a solid cylinder. Further improvements of the basis for in vivo heat transfer modeling are crucially dependent upon more extensive comparison with three-dimensional in vivo studies.

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A thesis submitted to the faculty of engineering university of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg 1991 / Analysis of temperatures measured in an experimental coal bed (using the classical conductive-convective approach) confirm previously published permeabilities of similar beds, and furthermore validate the use of heat- transfer coefficients at exposed surfaces of coal stockpiles, The range of the estimated heat transfer coefficients is similar to natural convective coefficients at flat horizontal surfaces, which is expected. [Abbreviated Abstract. Open document to view full version] / GR2017

Les transferts de chaleur constituent la base de nombreux processus industriels qui sont présents dans notre vie quotidienne. L’intensification de ces échanges et l’amélioration du rendement sont devenues aujourd’hui une problématique majeure dans le monde industriel, des organismes de réglementation mais aussi de la société dans son ensemble, qui prend conscience de l’épuisement progressif des ressources énergétiques et qui se soucie de l’avenir en matière énergétique. Face à ces enjeux énergétiques et environnementaux, Le défi technologique réside dans le développement de nouveaux processus pour une meilleure gestion de l’énergie. Ce travail de thèse s’inscrit dans ce cadre, et concerne particulièrement les problèmes liés à l’intensification des échanges thermiques dans les échangeurs de chaleur. Les améliorations des échanges thermiques dites ‘passives’ sont une voie déjà largement élaborée et atteignent leurs limites. De nouvelles stratégies d’optimisation doivent donc être étudiées. Une de ces stratégies consiste à améliorer les propriétés thermiques des fluides caloporteurs utilisés dans les systèmes thermiques, notamment dans les échangeurs de chaleur. Des progrès importants en chimie ont permis dès la fin des années 90 de synthétiser des particules de taille nanométrique, qui, dispersées dans un liquide porteur, constituent des nanofluides. Leur synthèse répond au besoin d’améliorer les propriétés thermiques des fluides caloporteurs en y insérant une phase solide de conductivité thermique très élevée. Le fil directeur de ce travail consiste donc à caractériser de manière approfondie le comportement thermique et rhéologique des nanofluides à base de nanotubes de carbone NTC utilisés tout au long de ce travail afin de quantifier les principaux paramètres influençant leurs propriétés thermo-physiques et les phénomènes physiques régissant l’intensification des transferts thermiques induits par ces nanofluides. Une analyse des travaux de recherche antérieurs a été menée dans le but de s’affranchir des différents paramètres qui peuvent influencer le comportement thermique et rhéologique des nanofluides dont on citera les paramètres liés à la composition des nanofluides (fraction volumique des NTC, type de surfactant, rapport d’aspect des NTC), la température, le fluide de base… Suite à cette étude, nous avons mené une étude expérimentale sur les propriétés thermo-physiques des nanofluides testés (conductivité thermique, viscosité dynamique, masse volumique) et sur les performances thermiques dans un échangeur de chaleur. Nous avons présenté également une analyse des résultats de façon à étudier l’influence des paramètres évoqués ci-dessus. Les résultats obtenus sont comparés et discutés vis-à-vis des modèles classiques existants, en proposant des améliorations et des interprétations selon les tendances obtenues. Les résultats prometteurs de cette étude sont très encourageants et montrent que l’utilisation des nanofluides à base de nanotubes de carbone offre clairement une amélioration des performances thermiques par rapport aux fluides de base classiques. Les nanofluides à base de NTC peuvent constituer ainsi un débouché prometteur des transferts thermiques et présentent de bonnes perspectives et développement. / Heat transfer is one of the most important industrial processes in our daily lives. Nowadays, the intensification of the heat transfer and the improving of the energy efficiency have become a major problem in industry, regulatory agencies, and also the society that becomes conscious of the progressive exhaustion of the world’s energy resources and cares about the future of energy. Due to these energy and environmental issues, the technological challenge is to develop new processes for better energy management. This work fits in that context and applies particularly the problems associated to the improvements of heat exchanger’s energy efficiency. The conventional methods for increasing the heat transfer in heat exchangers have already been extensively explored and have reached their objective limits. There is therefore an urgent need for new strategies with improved performances. The novel concept of improving the thermal properties of the working fluids used in thermal system, especially in heat exchangers, has been proposed as a means of meeting these challenges. The innovative concept of nanofluids heat transfer fluids consisting of suspended of nanoparticles with very high thermal conductivities has been proposed for these challenges. The aim of this work is therefore to characterize profoundly the thermal and the rheological behavior of nanofluids containing carbon nanotubes CNTs used throughout of this work. This is in order to quantify the main parameters influencing their thermophysical properties and physical phenomena governing the intensification of heat transfer induced by these nanofluids. An analysis of previous researches has been conducted for the purpose of establishing various parameters that may influence the thermal and rheological behavior of nanofluids, which including the parameters related to the composition of nanofluids (volume fraction of CNTs, type of surfactant, aspect ratio of CNTs), the temperature, the base fluid... Following this study, experiments have been carried out on the thermal physical properties of tested nanofluids (thermal conductivity, dynamic viscosity, density) and thermal performances in a heat exchanger. Analyses of the results have been presented in order to study the influence of the abovementioned parameters. The results obtained are compared and discussed vis-à-vis the existing conventional models, suggesting improvements and interpretations according to the trends obtained. The promising results of this study are very encouraging and show that the use of nanofluids containing carbon nanotubes clearly improved the thermal performances compared to the conventional base fluids. The CNT-based nanofluids can thus be a promising candidate for heat transfer and presents good perspective and development.

A research report submitted to the Faculty of Engineering and the Build Environment, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2014 / The South African power crisis and corresponding rising costs experienced since 2008, created a paradigm shift in terms of electricity use. The mining sector is the second highest consumer of electricity with metalliferous mines being accountable for 80% of the total power. Recent studies revealed that underground ventilation and cooling accounts for 30% to 40% of total electricity costs in an underground metalliferous mine. Hence the need to look at ways to reduce electricity consumption in ventilation and cooling. Work has been done on optimising efficiencies of ventilation and refrigeration systems of underground mines. Currently, the high energy consumption is driven by efforts to achieve a thermally acceptable environment for workers (manned) in deep metalliferous mines which is currently between 27ºC (wb) and 29ºC (wb). However, no detailed study has been done looking at increasing thermally acceptable environments for deep level metalliferous mine. In this study the impact of increasing rejection temperature to 40ºC (db) was assessed in the automated (unmanned) scenario at a maximum depth of 2811 metres. Then the power demand was compared with the manned scenario. The results proved that automation in an underground mine has the potential of reducing electricity cost of ventilation and cooling by more than 50%. For example, the production rate of about 200 kilo-tons per month yield an annual cost saving of R71 million on electricity. These cost savings can be used to justify automation systems. Automation removes workers from the hazardous environment and replaces them with equipment which can withstand harsher conditions. The introduction of an automation system in underground mines would not come risk-free. Currently, automation systems have not yet reached a level of removing workers completely from underground.There are instances that would require workers to enter production zones. A Bow-Tie risk analysis was used to show the hazards that workers would be exposed to and prevention controls and responses to mitigate the impact the risks. / MT2017

Qiu, Can = / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 82-87). / Abstracts in English and Chinese. / Qiu, Can = / Abstract --- p.i / 摘要 --- p.ii / Acknowledge --- p.iii / Table of Contents --- p.iv / List of Figures --- p.v i i / List of Tables --- p.xi / Chapter Chapters I --- Introduction --- p.1 / Chapter 1.1 --- Turbulence --- p.1 / Chapter 1.2 --- Rayleigh-Benard convection --- p.3 / Chapter 1.2.1 --- Physics picture-Motion in the convection cell --- p.4 / Chapter 1.2.2 --- The governing equations and parameters --- p.6 / Chapter 1.2.3 --- Multilayer convection --- p.9 / Chapter 1.2.4 --- The Nu scaling --- p.9 / Chapter 1.2.5 --- Boundary layers --- p.11 / Chapter 1.3 --- Present work and the organization of the thesis --- p.14 / Chapter II --- Experimental Setup --- p.16 / Chapter 2.1 --- The convection cell --- p.16 / Chapter 2.2 --- The thermistors --- p.20 / Chapter 2.2.1 --- Calibration --- p.20 / Chapter 2.3 --- The multimeter --- p.21 / Chapter 2.4 --- Thermostat box --- p.22 / Chapter 2.5 --- Visualization --- p.23 / Chapter 2.6 --- Motorized translation stage --- p.24 / Chapter 2.7 --- AC Wheatstone Bridge and Lock in amplifier --- p.24 / Chapter 2.8 --- Test different heaters --- p.26 / Chapter III --- "Heat flux, boundary layer and Reynolds number measurement of one-layer FC77 thermal convection" --- p.30 / Chapter 3.1 --- Heat flux measurement with correction --- p.30 / Chapter 3.1.1 --- Sidewall correction --- p.31 / Chapter 3.1.2 --- Bottom plate correction --- p.31 / Chapter 3.1.3 --- Post correction --- p.31 / Chapter 3.2 --- The Nu result --- p.32 / Chapter 3.3 --- Boundary layer measurement --- p.34 / Chapter 3.4 --- The Pr dependence of the Reynolds number Re --- p.37 / Chapter 3.5 --- Summary --- p.40 / Chapter IV --- "Heat transfer, thermal boundary layer and flow property measurement of multilayer immiscible fluid turbulent thermal convection" --- p.41 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Experiment --- p.44 / Chapter 4.3 --- The temperature and temperature fluctuation across the interface --- p.46 / Chapter 4.3.1 --- The temperature near the interface --- p.46 / Chapter 4.3.2 --- Position and temperature of the interface --- p.47 / Chapter (a) --- Using the profile to get the temperature of the interface --- p.47 / Chapter (b) --- Using the traveling microscope to get the absolute position of the interface --- p.50 / Chapter 4.4 --- The Nu result --- p.50 / Chapter 4.5 --- Boundary layer thickness and scaling --- p.54 / Chapter 4.6 --- Statistical properties of the temperature field across the interface --- p.58 / Chapter 4.6.1 --- Temperature time series and the corresponding histogram of the interface --- p.58 / Chapter 4.6.2 --- "The mean, root mean square, skewness, time derivative skewness and flatness of the temperature profiles across the interface" --- p.64 / Chapter 4.6.3 --- Scaling of the temperature fluctuation in two-layer system --- p.71 / Chapter 4.7 --- The temperature oscillation --- p.74 / Chapter 4.8 --- Passive scalar and active scalar --- p.77 / Chapter 4.9 --- Summary --- p.79 / Chapter V --- Conclusion --- p.80 / Chapter 5.1 --- One-layer thermal convection --- p.80 / Chapter 5.2 --- Two-layer thermal convection --- p.80 / Chapter 5.3 --- Future works --- p.81 / References --- p.82

Chu, Wai Siu = 聚合物添加劑對邊界層流動中熱傳輸量的影響 / 朱瑋韶. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 67-68). / Abstracts in English and Chinese. / Chu, Wai Siu = Ju he wu tian jia ji dui bian jie ceng liu dong zhong re chuan shu liang de ying xiang / Zhu Weishao. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.3 / Chapter 3 --- Formulation of the problem --- p.9 / Chapter 3.1 --- Prandtl-Blasius equations with temperature field --- p.9 / Chapter 3.2 --- The evolution equation for Rij --- p.15 / Chapter 3.3 --- Equations of motion with polymers --- p.19 / Chapter 3.4 --- Nusselt number and drag coefficient --- p.26 / Chapter 4 --- Results and discussion --- p.29 / Chapter 4.1 --- Obtaining the converged solutions --- p.29 / Chapter 4.2 --- Studying different parameters --- p.38 / Chapter 4.3 --- The parameter a --- p.54 / Chapter 5 --- Summary and Conclusion --- p.65 / Bibliography --- p.67

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 125-129. / by Kathleen Ann Hurley. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Curtis Harold Stern. / B.S.