Raymond Viskanta

Bio: Raymond Viskanta is an academic researcher from Purdue University. The author has contributed to research in topics: Heat transfer & Radiative transfer. The author has an hindex of 36, co-authored 158 publications receiving 4491 citations.

Journal of Heat Transfer Policy on Reporting Uncertainties in Experimental Measurements and Results

Abstract: The JOURNAL OF HEAT TRANSFER (JHT) has, for some time, recognized the need to prepare a set of guidelines on estimating experimental uncertainty. This was warranted for two major reasons: to ensure uniformity of presenting experimental data, and to raise the authors' awareness regarding the importance of giving a more precise statement about their measurement uncertainties.

Jet Impingement Boiling

Abstract: Publisher Summary Impinging liquid jets have found usage in many industrial applications, in both submerged (liquid-into-liquid) and free-surface (liquid-into-gas) arrangements. Because of the attractiveness of jet impingement cooling for high-heat-flux applications, numerous studies have been performed for both single- and two-phase conditions. This statement is particularly true for jet impingement boiling, that is distinguished by its ability to dissipate heat fluxes at the high end of the cooling spectrum. This chapter addresses liquid jets with continuous cross sections, thereby excluding spray and droplet impingement studies. Throughout this chapter, jet configurations are delineated into five categories of free-surface jets, plunging jets, submerged jets, confined jets, and wall jets. This chapter attempts to provide a comprehensive review and analysis of the current knowledge base on nucleate boiling heat transfer and on the critical (maximum) heat flux in impinging jet systems. This chapter addresses jet impingement literature pertinent to the transition and film boiling regime.

Heat Transfer in Semitransparent Solids

Abstract: Publisher Summary The chapter presents an overview of the background information needed to formulate and analyze heat transfer in semitransparent materials systematically and then reviews the literature in some specific problem areas Primary emphasis is placed on semitransparent solids, although the principles presented are general and apply to any phase The chapter also discusses the wide variety of applications and involves nature of heat transfer phenomena in semitransparent condensed phases The radiation characteristics of semitransparent materials are not only dependent on surface but also volume phenomenon since some of the emitted radiation originates at considerable depths In short, the radiation characteristics depend on the spectral absorption coefficient and index of refraction, thickness, boundary conditions, and temperature distribution The transient heating of semitransparent materials under idealized conditions in which the emission of radiation from the material is neglected is also discussed This implies that the body is cold and the rate of emission of radiation per unit volume is negligible compared to absorption This simplification limits the applicability of analysis and results to those early stages of heating during which temperatures have not raised high enough to render the assumption invalid The chapter also presents an analysis to show the influence of physical parameters on the temperature field in a semitransparent solid irradiated from a high temperature source such as the sun The results intend to aid the designer of solar collectors in selecting the optimum material by indicating physical parameters, which determine maximum efficiency of solar energy conversion in different semitransparent solids

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Jet Impingement Heat Transfer: Physics, Correlations, and Numerical Modeling

Abstract: Publisher Summary This chapter presents a discussion on jet impingement heat transfer. The chapter describes the applications and physics of the flow and heat transfer phenomena, available empirical correlations and values they predict, and numerical simulation techniques and results of impinging jet devices for heat transfer. The relative strengths and drawbacks of the Reynolds stress model, algebraic stress models, shear stress transport, and v 2 f turbulence models for impinging jet flow and heat transfer are compared in the chapter. The chapter provides select model equations as well as quantitative assessments of model errors and judgments of model suitability. The review of recent impinging jet research publications identified a series of engineering research tasks that are important for improving the design and resulting performance of impinging jets: (1) clearly resolve the physical mechanisms by which multiple peaks occur in the transfer coefficient profiles, and clarify which mechanism(s) dominate in various geometries and Reynolds number regimes, (2) develop a turbulence model, and associated wall treatment if necessary, that reliably and efficiently provides time-averaged transfer coefficients, (3) develop alternate nozzle and installation geometries that provide higher efficiency, meaning improved Nu profiles at either a set flow or set blower power, and (4) further explore the effects of jet interference in jet array geometries, both experimentally and numerically. This includes improved design of exit pathways for spent flow in array installations.