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.