Preparation, Characterization, Properties, and Application of Nanofluid

I. M. Mahbubul

• Publisher: William Andrew
• Year: 2018
• ISBN:
  9780128132999
• Topic: Physical Sciences
• Subtopic: Physics
• Index: Physics

Preparation, Characterization, Properties and Application of Nanofluid begins with an introduction of colloidal systems and their relation to nanofluid. Special emphasis on the preparation of stable nanofluid and the impact of ultrasonication power on nanofluid preparation is also included, as are characterization and stability measurement techniques. Other topics of note in the book include the thermophysical properties of nanofluids as thermal conductivity, viscosity, and density and specific heat, including the figure of merit of properties. In addition, different parameters, like particle type, size, concentration, liquid type and temperature are discussed based on experimental results, along with a variety of other important topics.

The available model and correlations used for nanofluid property calculation are also included.

• Provides readers with tactics on nanofluid preparation methods, including how to improve their stability
• Explores the effect of preparation method and stability on thermophysical and rheological properties of nanofluids
• Assesses the available model and correlations used for nanofluid property calculation

1

Introduction to Nanofluid

Abstract

This chapter introduces a general idea about nanofluids. It starts with background information on heat flow, then introduces colloidal systems and nanofluids. It includes brief information about colloidal properties: particle structure (size and shape), particle aggregate, polydispersity, and zeta potential. Then, the basics of nanofluids, heat transfer mechanism of nanofluids, properties of nanofluids, including how other parameters (particle size, concentration, and temperature) affect thermophysical properties and types of nanofluid are introduced.

Keywords

Colloid; particle aggregate; polydispersity; zeta potential; nanofluids; heat transfer mechanism; thermophysical properties

1.1 Introduction

The importance of manipulating and controlling substances at a small scale was highlighted by Richard Feynman (Feynman, 1992) in “There’s Plenty of Room at the Bottom” (Mahbubul, Elcioglu, Saidur, & Amalina, 2017). In this modern era, customers are looking for high-performance equipment, but in a compact size with less weight. Therefore, the optimization of engineering devices is a major concern of many types of research since this approach affects performance and efficiency (Mahbubul et al., 2014). The performance of heat transfer equipment depends on the following equation:

$Q=A·\mathrm{\Delta }T·h$ (1.1)

(1.1)

where, $Q$

is the heat flow, $A$

is the heat transfer area, $\mathrm{\Delta }T$

is the temperature gradient, and $h$

is the heat transfer coefficient (HTC).

Therefore, heat transfer improvement can be made by increasing (1) heat transfer area, (2) temperature, and (3) HTC (Saidur, Leong, & Mohammad, 2011). Case (1) is usually avoided because increasing the heat transfer area will increase the bulkiness (size and weight) of the equipment. Case (2) needs more input power to increase the temperature and as a result operating costs will be increased. Therefore, technologies have already reached their limit for cases (1) and (2). Tremendous researches are on-going for case (3) by changing different parameters. Now researchers are trying to increase the HTC of liquids by mixing solid particles into these liquids. These types of heterogeneous mixtures are called colloidal systems, which are made up of the dispersed phase and dispersion medium. As the addition of solid particles in a liquid increases the viscosity of the suspension, as a result the pumping power and pressure drop increase, and clogging and blockage of the flow passage can also happen. Therefore, nanosized (10⁻⁹ m) solid particles (called nanoparticles and mostly in powder form) are proposed to mix with heat transfer fluids to increase their HTC.

1.2 Colloid

The study of physics and chemistry introduces three states of matter: solid, liquid, and gas, as well as the transformations (melting, sublimation, and evaporation) among them (Everett, 1988). Besides the pure substances, there are solutions, which are the homogeneous/heterogeneous dispersion of two or more similar or different species mixed together on a molecular scale. The system of this kind is called “colloids,” where one component is finely dispersed in another (Everett, 1988). Table 1-1 shows an example of some typical colloidal systems. Previously, Thomas Graham distinguished substances into two types as crystalloids and colloids based on diffusion characteristics. If a substance can directly diffuse a parchment membrane it is a crystalloid, for example, acids, bases, sugars, and salts. On the other hand, if a substance very slowly diffuses through parchment paper it is a colloid, for example, glue. However, these terminologies have been proved to be inappropriate, as with a change of environmental conditions these states can be changed. Hiemenz and Rajagopalan (1997) define colloid as “any particle, which has some linear dimension between 10⁻⁹ m (1 nm) and 10⁻⁶ m (1 µm) is considered a colloid.” Nevertheless, these limits are not rigid, for some special cases (emulsion and some typical slurry) particles of larger size are present. Fig. 1-1 shows some real-life examples of nanometer to millimeter scale substances.

Table 1-1

Some Typical Colloidal Systems

Example	Class	Dispersion Phase	Dispersion Medium
Fog, mist, tobacco smoke, aerosol sprays	Liquid aerosol	Liquid	Gas
Industrial smokes	Solid aerosol	Solid	Gas
Milk, butter, mayonnaise	Emulsions	Liquid	Liquid
Inorganic colloids	Sols or colloidal suspensions	Solid	Liquid
Clay slurries, toothpaste, muds	Paste	Solid	Liquid
Opal, pearl, stained glass, pigmented plastics	Solid suspension or dispersion	Solid	Solid
Froths, foams	Foam	Gas	Liquid
Meerschaum	Solid foam	Gas	Solid
Jellies, glue	Gels	Macromolecules	Solvent

Source: Adapted from Everett, D.H. (1988). Basic principles of colloid science, Royal Society of Chemistry, London with permission from The Royal Society of Chemistry.

Figure 1-1 Examples of nanometer to millimeter scale substances. Reprinted from Serrano, E., Rus, G., and Garcia-Martinez, J. (2009). Nanotechnology for sustainable energy. Renewable and Sustainable Energy Reviews 13, 2373–2384 (Serrano, Rus, & Garcia-Martinez, 2009), copyright (2009), with permission from Elsevier.

Colloid science is an interdisciplinary subject; its field of interest overlaps with chemistry, physics, biology, material science, and several other disciplines (Hiemenz & Rajagopalan, 1997). It is the particle dimension—not the chemical composition (organic or inorganic) or physical state (e.g., one or two phases)—i.e., crucial. The last century has seen a renaissance of interest in colloids (Everett, 1988). Therefore, the important properties of colloids have been identified. Some common physical properties of colloids that are studied to evaluate the dispersion characteristics are now discussed.

1.2.1 Particle Structure (Size and Shape)

Physical dimensions, the defining characteristic of colloids, are considered as the most significant feature of colloidal particles. Particle movement depends on its size and shape. Many other properties (e.g., specific surface area, aggregation behavior, and microstructure) are strongly influenced by the particle dimensions. Thermophysical properties of a suspension also depend on particle size and shape (Baheta & Woldeyohannes, 2013; Timofeeva et al., 2010; Timofeeva, Routbort, & Singh, 2009). The easiest particle structure is considered as uniform-size particles with spherical geometry, however, colloidal particles come in all sizes and shapes.

1.2.2 Particle Aggregate

It is a general phenomenon that the smaller particles of a suspension want to join together and makes greater structures known as aggregates. The interparticle force is considered to be the reason behind this aggregation. Particle size distribution is analyzed to check the aggregate size. Fig. 1-2 shows the effective parti...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Acknowledgments
• 1. Introduction to Nanofluid
• 2. Preparation of Nanofluid
• 3. Stability and Dispersion Characterization of Nanofluid
• 4. Thermophysical Properties of Nanofluids
• 5. Rheological Behavior of Nanofluid
• 6. Optical Properties of Nanofluid
• 7. Correlation and Theoretical Analysis of Nanofluids
• 8. Application of Nanofluid
• Nomenclature
• Index