K. B. Anoop

Bio: K. B. Anoop is an academic researcher from Texas A&M University at Qatar. The author has contributed to research in topics: Nanofluid & Viscosity. The author has an hindex of 2, co-authored 2 publications receiving 362 citations.

Rheological and flow characteristics of nanofluids: Influence of electroviscous effects and particle agglomeration

Abstract: Nanofluids have shown remarkable attraction in heat transfer community due to its reported enhanced thermal properties. One factor which can restrict nanofluids in heat transfer application is the increased viscosity value (compared to classical predictions). Particle aggregation occurring was the major reason for this observation. Even though majority of the aqueous nanofluids prepared in literature were stabilized electrostatically by adjusting the pH, studies on the effect of the electrical double layer thus created and its influence on viscosity increase has not been investigated for these nanofluids so far. Thus, in the present paper, rheological properties of alumina-water nanofluids, which are electrostatically stabilized, are measured and the increase in suspension viscosity due to presence of this electrical double layer causing additional electroviscous effects is brought out. Based on dynamic light scattering studies, particle agglomeration and its subsequent effect in increasing the viscosity ...

Mechanism of enhancement/deterioration of boiling heat transfer using stable nanoparticle suspensions over vertical tubes

Abstract: Boiling heat transfer using nanofluids has been a subject of a few investigations in the past few years and incongruous results have been reported in literature regarding the same. Conflicting explanations for deterioration of pool boiling heat transfer coefficient at higher concentrations (4–16wt%) have been presented by various researchers. Recently, a few works have reported a significant enhancement in pool boiling heat transfer coefficient at lower concentrations (0.32–1.25wt%) and the physical reasons for this have not been explained. The present work is aimed at removing these ambiguities. Experiments have been carried out by using stable water based nanofluids containing alumina nanoparticles (average sizes of 47 and 150nm) with vertical tubular heaters of various surface roughnesses (48, 98, and 524nm). It has been observed that with the rough heater (Ra=524nm), heat transfer is significantly enhanced and the enhancement reaches ∼70% at a particle loading of 0.5wt%. With the smooth heater (Ra=48n...

Small particles, big impacts: A review of the diverse applications of nanofluids

Abstract: Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.

Nanofluids: from vision to reality through research

Abstract: Nanofluids are a new class of nanotechnology-based heat transfer fluids engineered by dispersing and stably suspending nanoparticles with typical length on the order of 1-50 nm in traditional heat transfer fluids. For the past decade, pioneering scientists and engineers have made phenomenal discoveries that a very small amount (<1 vol %) of guest nanoparticles can provide dramatic improvements in the thermal properties of the host fluids. For example, some nanofluids exhibit superior thermal properties such as anomalously high thermal conductivity at low nanoparticle concentrations, strong temperature- and size-dependent thermal conductivity, a nonlinear relationship between thermal conductivity and concentration, and a threefold increase in the critical heat flux at a small particle concentration of the order of 10 ppm. Nanofluids are of great scientific interest because these unprecedented thermal transport phenomena surpass the fundamental limits of conventional macroscopic theories of suspensions. Therefore, numerous mechanisms and models have been proposed to account for these unexpected, intriguing thermal properties of nanofluids. These discoveries also show that nanofluids technology can provide exciting new opportunities to develop nanotechnology-based coolants for a variety of innovative engineering and medical applications. As a result, the study of nanofluids has emerged as a new field of scientific research and innovative applications. Hence, the subject of nanofluids is of great interest worldwide for basic and applied research. This paper highlights recent advances in this new field of research and shows future directions in nanofluids research through which the vision of nanofluids can be turned into reality.

Structured surfaces for enhanced pool boiling heat transfer

Abstract: We experimentally investigated surface roughness-augmented wettability on critical heat flux (CHF) during pool boiling with horizontally oriented surfaces. Microstructured surfaces with a wide range of well-defined surface roughness were fabricated, and a maximum CHF of ∼208 W/cm2 was achieved with a surface roughness of ∼6. An analytical force-balance model was extended to explain the CHF enhancement. The excellent agreement found between the model and experimental data supports the idea that roughness-amplified capillary forces are responsible for the CHF enhancement on structured surfaces. The insights gained from this work suggest design guidelines for new surface technologies with high heat removal capability.