Authors:I. Perez-Raya; S.G. Kandlikar Abstract: Publication date: Available online 7 October 2016 Source:Advances in Heat Transfer Author(s): I. Perez-Raya, S.G. Kandlikar Numerical simulation of evaporation and boiling processes is of great relevance in developing a deeper insight into the mechanisms governing these phenomena. In developing the underlying numerical codes, their validation with theoretical models is essential. Previous models have in general relied on the basic case of evaporation from saturated vapor to superheated liquid separated by a planar or curved interface. However, different liquid and vapor conditions are employed in simulating complex evaporation/boiling processes. This chapter conveys eight different cases classified under the Stefan problem that employ different combinations of a saturated, subcooled, or superheated liquid phase and a saturated or superheated vapor phase along with the same or different phase densities. Numerical procedures and theoretical equations for these cases are presented over a planar surface. These cases are recommended for validating numerical codes developed for simulating the evaporation/boiling processes. Specific examples are also given using the commercial software ANSYS-Fluent to demonstrate the validation techniques presented in this chapter.

Authors:Jaluria Abstract: Publication date: Available online 4 October 2016 Source:Advances in Heat Transfer Author(s): Y. Jaluria This review paper focuses on the heat and mass transfer mechanisms that form the basis for many materials processing and manufacturing systems. It is critical to link the basic thermal process with the manufactured product to improve existing manufacturing systems and develop new ones. The approaches that may be adopted to study these processes and their effect on the product are discussed. Of particular interest are practical aspects such as feasibility, product quality, optimal operating conditions, and production rate that are often governed by thermal issues. Many complexities arise in the modeling of the transport phenomena, as well as in experimentation. These are discussed, along with important techniques that may be employed. Several important processes are discussed to present characteristic results and solution strategies. The field is quite extensive and only a few important processes can be considered in detail. Validation of the model is crucial and is based on existing results, as well as on experimental systems specially developed for satisfactory validation. The coupling between the micro/nanoscale transport processes that affect product characteristics and the conditions imposed at the system level are discussed. The current status, future trends, and research needs, regarding new and emerging materials, processes, and applications, are also outlined. It is seen that there is critical need to understand the basic mechanisms that determine changes in the material due to thermal effects, to assess the impact on the overall field of materials processing.

Authors:P.H. Oosthuizen Abstract: Publication date: Available online 22 September 2016 Source:Advances in Heat Transfer Author(s): P.H. Oosthuizen A review of external natural convective heat transfer from bodies that have a wavy surface is given. Surfaces with waves that have sinusoidal, rectangular, and triangular shapes are considered, and the main attention has been given to situations in which laminar, transitional, and turbulent flow exist. Attention has been given to horizontal, vertical, and inclined surfaces. Most of the results discussed were obtained numerically. The increase in the mean heat transfer rate from the surfaces resulting from the presence of the waves, in particular, has been considered and compared to the increase in the surface area resulting from the use of the surface waves. Generally, it is found that significant increases in the heat transfer rate resulting from the use of a wavy surface only occur at relatively high Rayleigh number values and that the increase in the heat transfer rate is not strongly dependent on the wave shape.

Authors:A.F. Emery Abstract: Publication date: Available online 21 September 2016 Source:Advances in Heat Transfer Author(s): A.F. Emery The paper begins in Part I with at least a part of the answer to “Why did I become an engineer and a professor?” Growing up in a family unfamiliar with higher education, neither the implied question about attending college nor the answer were obvious. Because of the cataclysmic beginning of World War II in the Pacific and the associated scare of an attack, I ended up going to school 12months a year. This had a major influence on my early schooling and may have been the impetus that led to my professional development. Part II describes my involvement with inverse problems and parameter estimation. The current emphasis on complex computer models to simulate thermal systems requires that the model parameters be known with precision. In addition, the uncertainties associated with the experimental data and the model predictions are topics of great interest to both experimentalists and modelers. This is particularly true when models are used to extrapolate performance to regions outside of the parameter space used for validation of the model. During a trip to Russia a fortuitous meeting with faculty of the Moscow Aviation Institute introduced me to inverse problems. This was a fascinating area and reading the literature, particularly that which was related to electrical engineering, particularly radar sensing, I became fascinated with Bayesian statistics and inference. This chapter describes the development of my interests and the technical details associated with both inverse problems and parameter estimation. Early parameter estimation efforts were based on the least squares technique which for normally distributed variables is equivalent to maximum likelihood. Unfortunately, these solutions give at best only approximate estimates of the uncertainty associated with the estimates. Bayesian inference supplies more precise estimates, but at a substantial increase in computational cost. An alternative approach is that of Markov Chain Monte Carlo, still very expensive. Part II describes these different methods and presents the results of their application to a number of thermal problems.

Authors:K. Khanafer; K. Vafai Abstract: Publication date: Available online 19 September 2016 Source:Advances in Heat Transfer Author(s): K. Khanafer, K. Vafai A comprehensive synthesis of the thermal conductivity of graphene under various conditions is performed in this review. Results obtained from different experimental techniques and theoretical studies are summarized and discussed for several conditions such as preparation process, shape, sample size, wavelength, and temperature. Broad discrepancies in the measured thermal conductivity results were found in many studies. Based on the cited data, several measured thermal conductivity values of graphene appear to be substantially overestimated. A majority of the documented results reported lower values of thermal conductivity than the earlier reported results. Moreover, large differences in the values of thermal conductivity of graphene were noticed from the cited results using different experimental and numerical methods (0.14–20,000W/mK). This raised a fundamental concern on the accuracy of these techniques when measuring thermal conductivity of graphene at nanoscale sizes. Therefore, more experimental and theoretical studies should be conducted to accurately measure the thermal conductivity of graphene.

Authors:Mark W. Dewhirst; John Abraham; Benjamin Viglianti Pages: 397 - 421 Abstract: Publication date: 2015 Source:Advances in Heat Transfer, Volume 47 Author(s): Mark W. Dewhirst, John Abraham, Benjamin Viglianti The use of heat to treat cancer has been extensively studied in preclinical models and in human clinical trials. When combined with radiotherapy and chemotherapy, hyperthermia can yield synergistic interactions that increase likelihood that tumors will be controlled locally. Some evidence also exists that improvement in local tumor control can lead to survival advantages. The achievement of therapeutic success with thermal therapies, however, requires a robust thermal dosimetry. This paper provides an overview of the evolution of thermometry and thermal dosimetry for both traditional hyperthermia and thermal ablation. Following the thermal dosimetry discussion, a brief review of key clinical trial results is discussed.

Authors:Krsto Sbutega; David Geb; Ivan Catton Pages: 1 - 165 Abstract: Publication date: Available online 9 October 2015 Source:Advances in Heat Transfer Author(s): Krsto Sbutega, David Geb, Ivan Catton This chapter examines application of volume averaging theory for flow and convective heat transfer in multiscale engineered structures. The volume-averaged approach is shown to be an upscaling procedure analogous to other homogenization techniques that are commonly used in transport phenomena, and is applied to the governing equations for laminar and turbulent heat transfer and fluid flow. In the homogenization process information about the underlying fields is lost, which leads to the need to relate these effects on the averaged equations through a closure procedure. The definition of these parameters is discussed in detail, and how they can be obtained from available data or numerical studies. The advantages of the homogenization procedure are shown by applying it to two common heat transfer devices: a heat sink and a heat exchanger. It is found that system performance parameters predicted using the homogenized model are within 5–6% of experimental data, and efficient numerical solution of these equations leads to computational times that are three or four orders of magnitudes lower than those required by direct numerical simulations. The computational savings are exploited by coupling the solution procedure to population-based optimization algorithms, which are used to find an optimum configuration. The result of this coupling is a heat sink with a thermal resistance of 0.058°C/W, and a heat exchanger with 96% effectiveness.

Authors:Vijay K. Dhir Pages: 167 - 202 Abstract: Publication date: Available online 13 August 2015 Source:Advances in Heat Transfer Author(s): Vijay K. Dhir Past efforts in developing an understanding of nucleate boiling under reduced gravity conditions have been mostly experimental. Often conjectures are made to explain the observed phenomena. In this chapter, numerical simulations of the process are used to simulate bubble dynamics and associated heat transfer at earth normal gravity, at 1/100th of earth gravity, and at microgravity conditions. The simulation results have been validated with experiments conducted on earth, in parabolic flights, and on the International Space Station. Numerical simulations are extended to predict nucleate boiling heat transfer on microfabricated and ordinary surfaces that are placed normal to the major gravity vector. In predicting the dependence of nucleate boiling heat flux on superheat correlations available in the literature for number density of active nucleation sites and waiting periods are used. For microfabricated surfaces, number of active sites and their location on the surface, as observed in experiments, were used as input to the model. Consistent with data from experiments, numerical simulations show that with reduced gravity heat transfer rate degrades.

Authors:M. Michael Yovanovich; Waqar A. Khan Pages: 203 - 307 Abstract: Publication date: Available online 1 September 2015 Source:Advances in Heat Transfer Author(s): M. Michael Yovanovich, Waqar A. Khan Models and corresponding correlations are proposed for Poiseuille flow in long micro- and nanochannels of circular and noncircular cross sections. The Poiseuille number is based on the Fanning friction factor, and the characteristic lengths are the conventional hydraulic diameter and the square root of the flow area. The accurate correlations are applicable for regular polygonal and trapezoidal microducts, elliptical, rectangular, and circular annular microchannels. Models and correlations are developed for Poiseuille flow in isosceles trapezoidal and hexagonal microchannels which are KOH-etched in silicon substrates. The equivalent circular annular model is proposed for Poiseuille flows in doubly connected microchannels such as circular microchannels with polygonal cores and polygonal microchannels with circular cores. A comprehensive model and correlation are advanced for Poiseuille flow in arbitrary (scalene) microducts. Models and correlations are proposed for convective heat transfer for Poiseuille flow in circular and noncircular microchannels with isoflux and isothermal walls. A compact model is given for the slip flow regime for circular and noncircular microducts and microchannels, which is based on slip flow parameters and the continuum Poiseuille number. All numerical results for regular polygonal and trapezoidal microducts and elliptical, rectangular, circular annular, and trapezoidal microchannels are in very good agreement with the slip flow model which is extended into the transition regime down to the Knudsen minimum. Rarefied gas flows in elliptical and rectangular microchannels in the slip flow and transition regimes are found to be similar for identical aspect ratios.

Authors:John R. Howell Pages: 309 - 340 Abstract: Publication date: Available online 13 August 2015 Source:Advances in Heat Transfer Author(s): John R. Howell The author's experiences in thermal radiative transfer are outlined, particularly his involvement in Monte Carlo methods, solar energy systems (with applications for residential and commercial structure cooling), inverse solution techniques at the macro- and nanoscales, and developments of solution techniques for the radiative transfer equation and for conjugate solutions. Comments are presented on potential emerging research areas and the possibility of breakthrough applications in radiative transfer visualization and analysis.

Authors:Kenneth R. Diller Pages: 341 - 396 Abstract: Publication date: Available online 1 October 2015 Source:Advances in Heat Transfer Author(s): Kenneth R. Diller Mammals and birds that regulate the core body temperature have an elaborate and highly effective thermoregulatory system. This system depends on the ability to move heat between the body core and surface via the convection of blood. Glabrous areas of skin, located in humans primarily on the palms, soles, ears, and selected facial sites, contain a vascular network with large-bore shunt vessels called arteriovenous anastomoses (AVAs) that have a highly dynamic and specialized control. Under conditions of core energy conservation, AVAs tightly vasoconstrict. Under conditions of core heat rejection, they vasodilate so that a significant fraction of the cardiac output can flow through them to exchange heat with the environment. A primary site of control is the preoptic anterior hypothalamus (POAH). This paper presents evidence that humans have a parallel controller peripheral to the POAH lying along the spinal cord, consistent with prior evidence in other mammalian and avian species. The ability to thermally access the spinal controller simply and safely provides an opportunity to exercise management of the body core temperature independent of the POAH to induce therapeutic hypothermia, which can have life-saving consequences for multiple medical conditions. Data are presented demonstrating the efficacy of selective thermal stimulation (STS) to the spinal cord as a means to regulate blood flow to the AVAs on demand. STS can be used in combination with dedicated heat exchangers placed onto glabrous skin to produce large heat fluxes into and out of the body for therapeutic purposes. This technology provides the basis for a new generation of medical heat transfer devices.

Authors:Ya-Ling He; Wen-Quan Tao Pages: 87 - 186 Abstract: Publication date: 2014 Source:Advances in Heat Transfer, Volume 46 Author(s): Ya-Ling He , Wen-Quan Tao In this chapter, the existing mechanisms for enhancing single-phase convective heat transfer are reviewed and the fundamental mechanism, that is, to reduce the intersection angle between fluid velocity and temperature gradient, is presented in detail. This basic idea is called the field synergy principle (FSP). A great number of examples are provided to demonstrate the validity of the FSP. Some typical convective heat transfer phenomena are analyzed and found that their characteristics can be well understood by the FSP. An effective way for improving convective heat transfer performance of an existing heat transfer structure is to reveal the locations with a bad synergy (i.e., large local synergy angle) and improve the performance by changing the local structure of the surface. Examples of new enhanced surfaces are provided which are developed under the guidance of the FSP. It is demonstrated that for the best synergy case where fluid velocity coincides with temperature gradient, the exponent in Nu ∞ Re m reaches its maximum value of 1. Then, the thermohydraulic performance comparisons of the enhanced configurations with the reference one are discussed under three constraints: identical pumping power, identical pressure drop, and identical flow rate. All the three constraints can be unified in a picture with log(f e /f o ) and log(Nu e/Nu 0) as abscissa and ordinate, respectively. The entire plane is divided into four quadrants by the two coordinates, and the first quadrant is the most frequently encountered. An enhanced technique can be represented in this plot and the constraint under which heat transfer is enhanced can be clearly identified.

Authors:West B.E.; Launder Iacovides Abstract: Publication date: Available online 1 October 2014 Source:Advances in Heat Transfer Author(s): A. West , B.E. Launder , H. Iacovides This chapter reexamines the problem of computationally modelling the flow over moderately close-packed, in-line tube banks that are a frequently adopted configuration for large heat exchangers. While an actual heat exchanger may comprise thousands of tubes, applied computational research aimed at modelling the heat-exchanger performance will typically adopt, at most, a few tens of tubes. The present contribution explores the sensitivity of the computed results to the pitch:diameter ratio of the tube, to the number of tubes in the domain, and to the particular modelling practices adopted. Regarding the last aspect, both large-eddy simulation (LES) and URANS (unsteady Reynolds-averaged Navier–Stokes modelling) approaches have been tested using periodic boundary conditions. The results show that URANS results adopting a second-moment closure are in closer accord with the LES data than those based on linear eddy-viscosity models. Moreover, the treatment of the near-wall region is shown to exert a critical influence not just on wall parameters like the Nusselt number but also on such fundamental issues as the flow path adopted through the tube bank. Comparison is also made with experiments in two small, confined, tube-bank clusters such as are typically used to provide data for performance estimation of a complete industrial tube bank. It is shown that such small clusters generate very substantial secondary flows that may not be typical of those found in a full-sized heat exchanger.

Authors:Raymond Viskanta Pages: 47 - 86 Abstract: Publication date: Available online 20 September 2014 Source:Advances in Heat Transfer Author(s): Raymond Viskanta Developments in thermal radiation are presented by the author from his perspective of teaching a graduate-level radiation heat transfer course at Purdue University for about 40 years. The account starts with the nineteenth century. The major findings on the physical nature of radiation are discussed and are continued with the birth of the quantum theory. The focus in the article is on modeling of radiation heat exchange among ideal and real surfaces. Conjugate heat transfer—radiation combined with conduction and/or convection—is briefly discussed. Radiative transfer in participating media is considered next, and the interaction of radiation with other modes of heat transfer is examined. Finally, some unsolved problems needing future research attention are identified.

Authors:Ping Cheng; Xiaojun Quan; Shuai Gong; Xiuliang Liu; Luhang Yang Pages: 187 - 248 Abstract: Publication date: Available online 1 October 2014 Source:Advances in Heat Transfer Author(s): Ping Cheng , Xiaojun Quan , Shuai Gong , Xiuliang Liu , Luhang Yang Recent analytical and numerical studies on boiling and condensation heat transfer are reviewed in this paper. Thermodynamic analyses on heterogeneous nucleation of bubbles on superheated surfaces in pool boiling, as well as on heterogeneous condensation of droplets on subcooled surfaces in stagnant moist air are presented. Numerical results obtained by level-set/VOF methods and by the newly developed phase-change lattice Boltzmann method on bubble nucleation, growth and departure in pool and flow boiling, as well as on film and dropwise condensation on vertical plates are summarized. Closed-form analytical solutions for critical heat fluxes on smooth and rough surfaces based on force balance analyses of a bubble are discussed and compared with experimental data. These recent analytical and numerical studies have not only provided improved understanding of complex physical processes involving boiling and condensation heat transfer but also clarified many contradictory results obtained from experimental investigations.