Heat Transfer Enhancement Techniques E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 624

Veröffentlichungsjahr: 2024

Beschreibung

This comprehensive guide explores the latest heat transfer enhancement techniques and provides the knowledge and insights required to tackle present and future challenges associated with heat dissipation, making it an essential resource for researchers, engineers, and professionals in the field.

In today’s rapidly evolving world, where technological advancements are driving industries forward, the need for innovative solutions for heat transfer and dissipation challenges is becoming increasingly critical. This book serves as a comprehensive guide that explores the latest heat transfer enhancement techniques and their potential to inspire the development of new devices and technologies. By delving into this subject matter, the book aims to empower researchers, engineers, and professionals in the field with the knowledge and insights required to tackle the present and future challenges associated with heat dissipation. It provides a roadmap for pushing the boundaries of traditional thinking and fostering innovation in the field.

Heat Transfer Enhancement Techniques: Thermal Performance, Optimization and Applications will be helpful to readers in presenting the basic and advanced technological developments of heat transfer enhancement techniques. Each chapter will cover a specific problem with future scope to further extend this research. This book contains new methodologies, models, techniques, and applications, as well as fundamental knowledge of heat transfer techniques.

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Heat Transfer Enhancement Techniques

Thermal Performance, Optimization and Applications

Edited by

Ashwani Kumar

Nitesh Dutt

and

Mukesh Kumar Awasthi

This edition first published 2025 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2025 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.

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Library of Congress Cataloging-in-Publication Data

ISBN 978-1-394-27096-5

Front cover images supplied by Pixabay.comCover design by Russell Richardson

Aim and Scope

The book Heat Transfer Enhancement Techniques: Thermal Performance, Optimization and Applications is designed to consider the cutting-edge heat transfer enhancement techniques that will obliterate the barriers of traditional thinking. It defies delving into the realms of the next generation, igniting a relentless pursuit of new devices and ground-breaking technologies. This book aims to bridge the gap between conventional methodologies and innovative strategies in the realm of heat transfer. This book will serve as a beacon for researchers, practitioners, and scholars seeking a deeper comprehension of cutting-edge techniques that go beyond conventional boundaries, aiming to revolutionize the field of heat transfer.

The practical guidelines provided by the authors can help engineers select the appropriate enhancement technique based on the specific requirements of the application, i.e., sustainable buildings, electronics industry, and batteries.

Furthermore, the book’s overarching objective is to integrate theoretical insights with practical implications, catering to a diverse audience invested in various industries. Its comprehensive approach not only focuses on elucidating complex heat transfer phenomena but also accentuates the practical implementation of these techniques across multiple sectors. By delving into interdisciplinary aspects, this book endeavors to offer a holistic understanding of heat transfer enhancement, thereby empowering professionals and researchers to leverage these advancements across diverse fields such as energy, electronics, construction, and automotive industries.

Top of form. The book has dedicated industrial application of heat transfer enhancement techniques, which makes it ideal for students and industry professionals since it helps them comprehend the background, current, and prospective future of the subject under discussion. The research content will work as a reference book for post-graduate students, Ph.D. researchers, heat transfer scientists, mechanical engineers, budding researchers, production engineers, design engineers, and energy study professionals. The applicability of this book covers a wide range of industries such as heat transfer, production sector, fluid dynamics, research and development engineer, automotive industry, electronics industry, civil engineers, and researchers in nuclear heat transfer sectors, and it will help the audience conducting research in these industries.

Editors

Preface

The book Heat Transfer Enhancement Techniques: Thermal Performance, Optimization and Applications have eighteen chapters covering from introduction to advanced heat transfer enhancement techniques.

Chapter 1 provides a concise overview of the recent advancements in heat transfer enhancement methods, encompassing both experimental and computational approaches. It also covers recent technological advancements which enable the development of intelligent thermal management systems capable of adapting to dynamic operating conditions, thereby enhancing overall system efficiency. In continuation, Chapter 2 covers sustainable development goals and highlights the role of different governments, organizations, and communities worldwide for implementing renewable energy policies, investing in research and development, and promoting the adoption of clean energy technologies.

Chapter 3 deals with the application portion of heat transfer enhancement techniques in heating, ventilation, and air conditioning (HVAC) system. The chapter describes a concise overview of the fundamental methods that are employed to optimize the HVAC system performance through heat transfer enhancement. The enhancement of HVAC system efficiency through heat transfer enhancement techniques may offer multiple feasible design solutions that can be used by suitable trade-offs to meet specific building requirements and local climate conditions. Chapter 4 highlights the inventive strategy for sustainable cooling that can be achieved by the use of desiccant-assisted dehumidification and cooling systems in place of contemporary air conditioning systems to save energy and employ green cooling techniques for building comfort. To meet the energy demands in sustainable buildings, Chapter 5 highlights the use of eco-friendly paints. The primary objective of this chapter is to highlight the potential of ecofriendly paint as a sustainable option for smart buildings. The future of the study is concluded for the construction sector to develop energy efficient paint materials with better sustainability by incorporating natural waste. Chapter 6 promotes renewable energy application in green buildings to meet out the energy demands. The chapter presents an in-depth exploration of the integration and enhancement of renewable energy technologies in sustainable building practices. The chapter systematically dissects the current state of renewable energy technologies, focusing on solar energy, geothermal energy, and Earth-air heat exchangers (EAHE).

Chapter 7 present numerical approaches to examine the thermo-hydraulic behavior of micropin fin heat sink with a different shape of pin fins (diamond), constant surface area, and air at 4% volumetric concentration with Reynolds number variations from 1500 to 4000 for further optimization of heat transfer enhancement in solar-based systems. In continuation, Chapter 8 deals with the particle swarm optimization (PSO) to find the optimal operating parameters for maximizing the heat transfer rate in the double pipe heat exchanger (DPHE). In this study, the PSO-based process parameter optimization of the counter flow double pipe heat exchanger [CF-DPHE] is tested. Initially, real-time experiments are conducted with the CP-DPHE rig at the heat and mass transfer laboratory, Saranathan college of Engineering, A.P., India.

Chapter 9 discusses the application of geothermal energy-based Earthair heat exchanger (EAHE) systems within the context of sustainable building designs and operations. It is possible to draw the conclusion that effective usage of EAHE systems in conjunction with environmentally friendly energy sources and cutting-edge technology will be crucial in reducing energy consumption and protecting the environment not just in India but globally.

Chapter 10 presents a numerical study of solar air heater for drying application. The chapter presents a numerical investigation at various design parameters of roughness elements such as tube pitch ratios (P/H) of 1 to 4, roughness height ratios (er/H) of 0.2 to 0.5, under various values of Re from 3000 to 19000. This research could prove useful for further studies and industries to develop efficient SAH for drying applications. Chapter 11 deals with the development and assessment of a solar tracking system capable of optimizing the solar panel’s power output is the primary goal of this chapter. The solar tracking system prototype was constructed and put to the test. The data results are collated, and a graphical method is used to compare the performance of a static solar panel with a solar tracking system. As a result, tracking solar panels are able to produce greater current, voltage, and power than stationary solar panels.

Moving towards the second industrial application of heat transfer enhancement techniques, Chapter 12 provides a thorough overview of the thermal characterization of lithium-ion batteries (LIBs). The chapter serves as a valuable resource for researchers, engineers, and practitioners seeking a comprehensive understanding of thermal characterization techniques applied to lithium-ion batteries, particularly concerning the promotion of more durable, reliable, and safer lithium-ion batteries. The advanced techniques employed in battery state of health (SOH) prediction are discussed in Chapter 13. The SOH of a lithium-ion (Li-ion) battery is a measure of its overall health and performance relative to its original or designed specifications. Chapter 14 focuses on the computational analysis of mass and heat relocation upon the flow of Casson Cu-AA7075-AA7072/Methanol tri-hybrid nanofluids across a spinning disk under thermal radiation, slip condition, and chemical reaction. Cu nanoparticles are utilized as coolant in disk drives, computer monitors, televisions, and in many other electronic equipment. Chapter 15 investigates the thermal conduction and rate of heat transmission due to MXene (Ti3C2) nanoparticles flowing in blood arteries. For this purpose, mathematical modeling for blood flow on the curved region of the artery is developed using the Navier-Stokes equation.

Chapter 16 aims to create a precise mathematical solution for the movement of a shockwave in a gas that is not perfect and contains tiny solid particles. Additionally, the study will take into account the impact of a magnetic field. Chapter 17 investigates the influence of magnetite (Fe3O4) nanoparticles mixed with water (H2O) on a Casson fluid with a stagnation point on a porous stretched sheet.

Chapter 18 concludes the book with the idea of green building technologies. The chapter conducts a thorough examination of recent innovations, methodologies, and practices driving the evolution of smart green buildings. The socio-economic impact of smart green buildings is also investigated, highlighting their potential contribution to creating sustainable and resilient communities. The chapter concludes by envisioning the future trajectory of thermal renewable energy application in smart green buildings, foreseeing their continued integration into urban planning and the construction industry.

The above short summary of each chapter states the book’s nature, which makes it ideal for usage in graduate students curricula and makes it useful for research and academic purposes. It is helpful for mechanical-electrical-electronics-automobile engineers, policy makers, energy scientists, and industry professionals to study the subject under discussion.

Editors

Dr. Ashwani Kumar

Dr. Nitesh Dutt

Dr. Mukesh Kumar Awasthi

Acknowledgement

We express our gratitude to Wiley Scrivener Publishing and the editorial team for their suggestions and support during the completion of this book. We are grateful to all contributors and reviewers for their illuminating views on each book chapter presented in the book Heat Transfer Enhancement Techniques: Thermal Performance, Optimization and Applications.

“This book is dedicated to all engineers, researchers, and academicians.”

1Recent Innovation in Heat Transfer Enhancement Techniques

Ashwani Kumar1*, Mukesh Kumar Awasthi2, Nitesh Dutt3 and Varun Pratap Singh4,5

1Department of Mechanical Engineering, Technical Education Department, Uttar Pradesh, Kanpur, India

2Department of Mathematics, Babasaheb Bhimarao Ambedkar University, Lucknow, India

3Department of Mechanical Engineering, COER University, Roorkee Uttarakhand, India

4Solar Thermal Energy Research Group (STERG), Department of Mechanical Engineering and Mechatronics Engineering, University of Stellenbosch, Stellenbosch, South Africa

5Department of Mechanical Engineering, School of Advanced Engineering, UPES, Bidholi, Dehradun, Uttarakhand, India

Abstract

Heat transfer plays a critical role in various industrial processes, electronic cooling systems, battery thermal management and renewable energy applications. In recent years, significant strides have been made in the field of heat transfer enhancement techniques to improve efficiency and optimize thermal management. This abstract provides a concise overview of the recent advancements in heat transfer enhancement methods, encompassing both experimental and computational approaches. Innovative materials, such as advanced nanomaterials and metamaterials, have emerged as key contributors to enhanced heat transfer. Nanofluids, which consist of nanoparticles dispersed in traditional heat transfer fluids, exhibit improved thermal conductivity, leading to more efficient heat transfer in various applications. Additionally, the design and fabrication of structured surfaces with micro and nano-scale features, known as surface modifications, have proven effective in augmenting convective heat transfer. Additive manufacturing technologies have revolutionized the fabrication of intricate heat exchanger geometries, offering a high degree of customization and geometric complexity. This has led to the creation of compact and efficient heat exchangers with improved thermal performance. The integration of artificial intelligence and machine learning algorithms in heat transfer research has opened new avenues for optimization and control. These technologies enable the development of intelligent thermal management systems capable of adapting to dynamic operating conditions, thereby enhancing overall system efficiency. Integration of novel materials, innovative surface modifications, advanced computational simulations, additive manufacturing, and the incorporation of artificial intelligence plays a crucial role in heat transport enhancement.

Keywords: Heat transfer, innovative techniques, artificial intelligence, advance materials, heat exchangers

1.1 Introduction

Heat transfer is a fundamental process that plays a crucial role in the exchange of thermal energy between systems and their surroundings. Three distinct mechanisms govern heat transfer: conduction, convection, and radiation. Each method operates in unique ways, influencing the transfer of heat through different mediums and under diverse conditions. Understanding these mechanisms is essential for comprehending the thermal behavior of materials and systems in various environments, paving the way for advancements in fields such as engineering, physics, and materials science. Figures 1.1 and 1.2 show brief descriptions of methods of heat transfer. Table 1.1 highlights the factors and parameters that collectively contribute to the effectiveness of heat transport enhancement in various applications such as cooling systems, heat exchangers, and thermal management devices.

Figure 1.1 Methods of heat transfer.

Figure 1.2 Classifications of heat transfer methods [1–3].

Conduction, convection, and radiation are three fundamental methods of heat transfer. Conduction involves the direct transfer of heat through a material, typically a solid, by the collision of particles. In convection, heat is transferred through the movement of fluid (liquid or gas) particles, creating a cycle of warmer and cooler regions. This method is commonly observed in fluids where warmer portions rise and cooler portions sink, establishing a continuous circulation. Radiation, on the other hand, is the transfer of heat through electromagnetic waves that can propagate through a vacuum. Unlike conduction and convection, radiation does not require a medium and can occur in the absence of material substance. These three methods are crucial in various scientific and engineering applications, ranging from designing efficient heat exchangers to explaining the thermal dynamics of natural phenomena [1, 2].

1.1.1 Industrial Application of Heat Transfer Enhancement Techniques

Table 1.2 and Figure 1.3 highlight the key factors and different industrial applications of the heat transport enhancement techniques. Heat transfer enhancement techniques are often utilized in combination based on specific industrial requirements. Power generation, particularly in thermal power plants, the use of advanced heat exchanger designs and surfaces with enhanced thermal conductivity improves overall energy conversion efficiency. In the aerospace industry, where thermal management is critical, techniques such as finned surfaces and phase change materials aid in dissipating excess heat generated during flight. Additionally, in electronics and microelectronics manufacturing, heat transfer enhancement is vital to prevent overheating and ensure the reliability of electronic components. Furthermore, in the field of chemical processing, innovative heat exchanger configurations and materials facilitate more efficient heat transfer, reducing energy consumption and enhancing overall process productivity. Overall, the integration of heat transfer enhancement techniques is pivotal across industries, contributing to increased energy efficiency, improved system reliability, and enhanced performance in a wide range of applications.

Table 1.1 Important factors and their effect [1–4].

Important parameters

Effect

Surface area

Increased surface area improves heat transfer.

Use of extended surfaces, fins, or enhancements.

Fluid velocity

Higher fluid velocity enhances convective heat transfer.

Turbulent flow is more effective than laminar flow.

Temperature difference

Larger temperature gradients increase heat transfer.

Maintaining a large ΔT across surfaces.

Thermal conductivity

Greater thermal conductivity materials transfer heat more effectively.

Selection of materials in heat exchanger design.

Fluid properties

Heat transfer coefficient varies with fluid properties.

Consideration of specific heat, viscosity, density, etc.

Heat exchanger design

Efficient design improves heat transfer performance.

Optimization of geometry and arrangement of surfaces.

Surface roughness

Controlled roughness can enhance convective heat transfer.

Impact on boundary layer and flow characteristics.

Phase change

Latent heat transfer during phase change (

e.g.

, boiling, condensation).

Utilizing phase change for enhanced heat transfer.

Flow regimes

Transitioning from laminar to turbulent flow enhances heat transfer.

Understanding and controlling different flow regimes.

Agitation/mixing

Stirring or mixing enhances heat transfer in fluids.

Promotes better heat distribution within the fluid.

Thermal resistance

Reducing thermal resistance in the system improves heat transfer.

Minimizing resistances in series and parallel paths.

Heat transfer fluid

Selection of appropriate fluid for the specific application.

Consideration of thermal properties and stability.

1.1.2 Standards and Regulations

International standards and regulations pertaining to heat transfer are crucial for ensuring safety, efficiency, and environmental sustainability in various industries. Organizations such as the International Organization for Standardization (ISO) play a significant role in developing and maintaining these standards. ISO 22007 establishes guidelines for determining thermal conductivity, while ISO 6946 addresses heat transfer through building elements. Some general standards and organizations that are relevant to heat transfer and related fields are listed in Table 1.3. The applicability of these standards may vary depending on the industry and specific applications.

Table 1.2 Techniques to enhance heat transfer and their industrial applications [5, 6].

Heat transfer enhancement technique

Applications in industrial processes

Fins and extended surfaces

Cooling of electronic components

Heat exchangers for HVAC systems

Radiators in automotive engines

Heat exchangers

Chemical processing

Oil and gas refining

Power generation

Phase change materials (PCMs)

Thermal energy storage

Solar water heaters

Food processing

Nanofluids

Electronics cooling

Solar collectors

Biomedical applications

Jet impingement

Electronics cooling

Aerospace applications

Metal quenching

Fluidized bed heat transfer

Chemical and petrochemical processes

Biomass and coal combustion

Pharmaceutical manufacturing

Thermosyphon

Solar water heaters

Refrigeration systems

Heat recovery systems

Vortex generators

Heat exchangers

Automotive radiators

HVAC systems

Porous media

Electronics cooling

Nuclear reactors

Heat exchangers

Ribbed surfaces

Air-cooled heat exchangers

Gas turbine blades

Compact heat exchangers

Figure 1.3 Different industrial applications of heat transfer enhancement techniques.

1.2 Important Heat Transfer Enhancement Techniques and Their Effect

1.2.1 Effect of Fins and Extended Surfaces

The effect of fins and extended surfaces on heat transfer is a fundamental concept in thermal engineering and heat transfer. Fins are protrusions or extended surfaces attached to a heat-conducting base, such as a heat exchanger or a cooling system, designed to enhance the rate of heat transfer. The primary purpose of fins is to increase the surface area available for heat exchange, thereby improving the overall heat dissipation efficiency. This increased surface area promotes greater convection and radiation, facilitating the transfer of thermal energy from the solid base to the surrounding fluid or environment (Table 1.4). Fins are especially useful in applications where efficient heat dissipation is crucial, such as in electronic devices, radiators, and various industrial heat exchangers. The design and arrangement of fins play a significant role in optimizing heat transfer performance (Table 1.5), and engineers carefully consider factors such as fin geometry, material properties, and operating conditions to achieve the desired thermal performance.

Table 1.3 International standards and regulations related to heat transfer [1, 2].

Standards and regulations

Details

ASME Boiler and Pressure Vessel Code

Contains standards for the design, fabrication, and inspection of boilers and pressure vessels, including heat exchangers.

ASTM International

Creates and disseminates voluntary consensus technical standards for a variety of goods, services, systems, and materials, including heat transfer-related ones.

ISO 22000:2018

Lays out specifications for a food safety management system, which might take heat transfer in food processing into account.

API Standard 560

Covers the design, fabrication, installation, and maintenance of fired heaters for general refinery service.

ASHRAE Standards

The Refrigerating, American Society of Heating, and Air-Conditioning Engineers developed these standards, which cover a wide range of HVAC and heat transfer-related topics.

NEMA MG 1

Standard for motors and generators, which may have implications for heat dissipation and thermal management.

European Pressure Equipment Directive (PED)

Provides requirements for the design, manufacturing, and conformity assessment of pressure equipment, including heat exchangers.

ASCE 7

Thermal loads are one of the minimum design loads and related requirements for buildings and other structures.

ANSI/IEEE C62.41

Provides guidelines for the selection of surge arresters used in protecting electrical equipment from over-voltage transient events, which can affect heat transfer in electrical systems.

Table 1.4 Details of fin and extended surfaces [7, 8].

Aspect

Fins

Extended surfaces

Purpose

Increase surface area. Length, thickness, and spacing are crucial parameters.Pin fins, the diameter is an additional parameter.

Increase surface area

Heat transfer mechanism

Convection and radiation

Conduction, convection, and radiation

Primary application

Cooling electronic devices, heat exchangers

Heat exchangers, fins in engines, air-cooled systems

Heat transfer rate

Increases

Increases (dependent on material conductivity)

Surface area

Greater plane area for the dissipation of heat

Greater plane area for the dissipation of heat

Material selection

Good thermal conductivity (

e.g.

, aluminum)

Good thermal conductivity (

e.g.

, metals)

Geometry

Various shapes (Straight, pin, annular, louvered, serrated) fins

Louvered fins

focus on improving airflow around the surface.

Serrated fins

introduce turbulence to enhance heat transfer

Typically planar, but various shapes possible

Effectiveness

Highly effective in enhancing heat transfer

Effective, especially in applications with limited airflow

Table 1.5 Geometrical details of fins and their effects [9–12].

Geometry

Shape

Effect

Fins

Rectangular

Higher surface area improves heat dissipation

Triangular

Efficient for certain applications, enhances convective heat transfer

Circular

Suitable for cylindrical structures, improves heat dissipation

Annular

Effective for certain compact designs

Pin fins

Long, slender structures perpendicular to base

Enhances heat transfer in compact spaces, improves convective heat transfer

Plate fins

Flat surfaces attached to the base material

Effective for applications with limited space, enhances convective heat transfer

Louvered fins

Fins with spaced openings or slots

Improves airflow and convective heat transfer, suitable for forced convection

Serrated fins

Fins with serrations or notches

Enhances heat transfer by disrupting boundary layer, effective in forced convection

Wavy fins

Fins with a wavy or sinusoidal profile

Increases surface area and disrupts boundary layer, enhances convective heat transfer

Extended tubes

Tubes with external fins or ribbed surfaces

Increases heat transfer area, improves convective heat transfer in tubes

Microfins

Extremely small fins on a microscale

Enhances heat transfer in microchannels, suitable for miniaturized devices

Spine fin

Central spine with fins extending radially

Enhances heat transfer in both radial and axial directions

Swirl fins

Fins with a swirling or helical pattern

Enhances heat transfer through increased turbulence, suitable for certain applications

1.2.2 Effect of Phase Change Materials (PCMs)

Phase change materials (PCMs) show unique thermal and mechanical properties that make them integral in various heat transfer applications (Table 1.6). Phase change materials’ thermal properties involve their ability to absorb or release latent heat during phase transitions, providing a stable temperature within a defined range. The mechanical properties of PCMs, such as solid-liquid transition, enable them to undergo reversible phase changes without significant degradation. In heat transfer enhancement, PCMs play a crucial role by efficiently storing and releasing thermal energy, acting as thermal buffers to regulate temperature variations (Table 1.7). This is particularly beneficial in maintaining a constant temperature in applications like building insulation, electronics cooling, and renewable energy systems. The industrial applications of PCMs extend to diverse fields, including energy storage, heating, ventilation, and air conditioning (HVAC) systems, and thermal management in electronics, showcasing their versatility and significance in addressing heat transfer challenges across various sectors (Figure 1.4).

Table 1.6 PCM thermal and mechanical properties.

PCM

Thermal properties

Mechanical properties

Paraffin waxes

Melting range: 20°C to 70°C

Soft and pliable at room temperature

Bio-based PCMs

Variable depending on the specific material

Mechanical properties depend on the source and process

Salt hydrates

Melting range: 0°C to 100°C

Brittle at low temperatures, can be encapsulated

Metallic PCMs

High thermal conductivity, variable melting temperatures

Mechanical properties depend on the specific metal

Eutectic alloys

Sharp melting point, good thermal stability

Mechanical properties depend on the specific alloy

Polymer-based PCMs

Variable depending on the polymer used

Mechanical properties depend on the specific polymer

Inorganic PCMs

Variable depending on the specific material

Mechanical properties vary; some may be brittle

Carbon-based PCMs

High thermal conductivity, tunable properties

Mechanical properties depend on the carbon structure

Table 1.7 Role of PCM in heat transfer enhancement [12, 70–75].

Role

Details

Thermal energy storage

PCM absorbs and releases heat energy through phase change (solidification and melting), providing a high latent heat capacity for effective energy storage.

Temperature regulation

PCM helps regulate temperatures by maintaining a nearly constant temperature during phase change, preventing temperature spikes.

Heat transfer enhancement

PCM improves heat transfer efficiency by storing and releasing energy at a constant temperature, leading to a more uniform and controlled thermal profile.

Thermal mass

PCM adds thermal mass to systems, which helps in stabilizing temperature variations and reducing temperature fluctuations.

Energy conservation

PCM aids in conserving energy by storing excess heat during peak periods and releasing it during low-demand or off-peak periods.

Thermal comfort improvement

In buildings and textiles, PCM can contribute to improved thermal comfort by absorbing and releasing heat to maintain a comfortable environment.

Increased efficiency in cooling

PCM can enhance the efficiency of cooling systems by absorbing heat during the day and releasing it during the night when ambient temperatures are lower.

Reduced energy consumption

The use of PCM can lead to reduced energy consumption in heating and cooling systems, as it allows for better utilization of energy and reduces peak energy demands.

Temperature smoothing

PCM helps in smoothing out temperature variations by absorbing and releasing heat, contributing to a more stable and controlled thermal environment.

Passive cooling applications

PCM finds applications in passive cooling systems, such as building materials and textiles, where it helps maintain comfortable temperatures without active energy input.

Figure 1.4 Different industrial applications of phase change materials.

1.2.3 Effect of Heat Exchangers

Heat exchangers are devices designed to efficiently transfer thermal energy between two or more fluids, and their effectiveness is crucial for optimizing processes that involve heat exchange. These devices play a vital role in improving the overall efficiency of heat exchange systems. Heat exchangers facilitate the transfer of heat from one fluid to another, either for the purpose of heating or cooling, and their design and functionality can be tailored to enhance heat transfer rates. This enhancement is achieved through features such as increased surface area, improved fluid flow patterns, and the incorporation of advanced materials (Table 1.8). By employing heat exchangers with enhanced heat transfer capabilities, industries can achieve better energy efficiency, reduced operating costs, and improved overall performance in various thermal processes.

1.2.4 Effect of Microchannels

For improving heat transport in a variety of engineering applications, microchannels are vital. Heat exchangers, electronic cooling systems, and other thermal management devices use these channels, which usually have dimensions in the micrometer range [14]. There are various reasons why microchannels have such a large impact on heat transfer enhancements:

Increased surface area: because of their high plane area to volume ratio, microchannels help the working fluid and the channel walls make better contact. Higher heat transfer rates are encouraged by the more effective heat exchange made possible by the larger surface area.

Table 1.8 Roles of heat exchangers in heat transfer enhancement [13, 79].

Role

Description

Transfer of heat

Makes it easier for heat to be transferred between fluids or between a solid surface and a fluid without combining them.

Increased surface area

Enhances heat transfer by providing a larger surface area for contact between the hot and cold fluids, improving the overall efficiency of heat exchange.

Temperature control [

71

,

72

]

Allows for precise control of temperatures in industrial processes, HVAC systems, and various applications by regulating the flow rates of the hot and cold fluids.

Energy efficiency

Improves the overall energy efficiency of systems by recovering and utilizing waste heat, reducing the need for additional energy input.

Phase change applications

Used in applications involving phase changes (

e.g.

, condensation or evaporation), contributing to efficient heat transfer in processes such as refrigeration and power generation.

Heat recovery

Captures and reuses heat that would otherwise be lost, minimizing energy waste and reducing operational costs. Common in industrial processes and power generation.

Thermal integration

Integrates with other systems for efficient heat management, allowing for the optimization of processes and reducing environmental impact.

Preventing fouling and scaling

Helps prevent the buildup of deposits, fouling, and scaling on heat exchange surfaces, ensuring continuous and efficient heat transfer over time.

Enhanced heat transfer surfaces

Incorporates advanced surface geometries, materials, or coatings to increase heat transfer rates, promoting efficient thermal performance.

Compact design

Enables the design of compact systems, reducing space requirements while maintaining effective heat transfer, crucial in applications with limited space availability.

Fluid mixing control

Aids in controlling and minimizing undesirable mixing of fluids, maintaining the integrity of each fluid stream during heat exchange.

Maintenance ease

Designed to be easily maintainable, allowing for inspection, cleaning, and repairs to ensure longterm and reliable operation.

Versatility

Adaptable to a wide range of industries and applications, including chemical processing, power generation, HVAC, automotive, and more.

Temperature homogenization

Contributes to achieving uniform temperatures within a fluid or system, important in processes where temperature consistency is critical.

Safety

Plays a role in maintaining safe operating temperatures in various systems, preventing overheating or excessive cooling.

Reduced thermal resistance: microchannels have less thermal resistance than larger channels or traditional heat exchangers because of their smaller dimensions. A lower thermal resistance results in faster heat dissipation and better heat transfer efficiency overall.

Enhanced convective heat transfer: forced convection is encouraged by microchannels, and fluid flow displays special properties at the microscale, such as higher heat transport coefficients. The fluid’s high velocity within the microchannels facilitates convective heat transfer, increasing the process’s efficiency.

Increased heat transfer coefficient: the heat transport coefficients of microchannels are generally higher than those of macroscale channels. Increased surface area, decreased thermal resistance, and improved convective heat transfer work together to produce the intensified heat transfer coefficients.

Phase change heat transfer: microchannels are also utilized in applications relating phase change heat transfer, such as condensation and boiling. The small dimensions of microchannels facilitate rapid phase change processes, leading to improved heat transfer rates.

Compact design and space efficiency: microchannels enable the design of compact heat exchangers, making them suitable for applications with limited space. The compact design also reduces the thermal inertia of the system, allowing for faster response to changes in heat load.

In summary, microchannels contribute to heat transfer enhancements through their ability to increase surface area, reduce thermal resistance, promote convective heat transfer, and facilitate efficient phase change processes. These advantages make microchannels valuable in a variety of applications where effective thermal management is critical [15–17].

1.2.5 Effect of Nanofluids

The amazing heat transfer capabilities of nanofluids—engineered colloidal suspensions of nanoparticles in a base fluid—have attracted a lot of attention. When compared to their base fluids, these nanofluids have higher convective heat transport coefficients and thermal conductivities. Improved heat transfer performance is the outcome of changing the thermal characteristics of the base fluid by adding nanoparticles, such as metal oxides, carbon-based compounds, or other nanoparticles [19, 20]. Because of their enhanced thermal conductivity, nanofluids are good candidates for a variety of heat transfer applications because of their ability to carry heat efficiently [21–23]. Colloidal combinations of metallic or ceramic particles of nano-metric sizes suspended in a base fluid, like oil, ethylene glycol, or water, are known as nanofluids. In recent years, a great deal of research has been done on the application of nanofluids in heat transfer improvement strategies [24–26].

Particle composition, size, shape, concentration, and type of base fluid are among the variables that affect how well heat transfer is enhanced by nanofluids [27]. The degree of the thermal conductivity increase is dependent on the size of the nanoparticles; the largest increase was noted in nanofluids containing high aspect ratio nanoparticles [25]. To further optimize the nanofluid, a mixture of particles can be used to increase thermal conductivity without producing excessive viscosity. According to the results that are currently available in the literature, raising the heat exchanger’s flow rate could improve heat transfer more than adding nanoparticles could [24]. Furthermore, a standard for impartially assessing the impact of adding nanoparticles to working fluids is needed for the use of nanofluids in heat transport enhancement approaches.

One of the significant advantages of nanofluids in heat transport techniques is their ability to improve heat transfer rates. Due to their enhanced thermal conductivity, nanofluids can effectively dissipate heat, leading to better thermal performance in heat exchangers, refrigeration systems, and cooling applications. The nanoparticles in nanofluids can significantly modify the convective heat transport characteristics, promoting better heat transfer efficiency. Their use can contribute to more compact and efficient heat exchange systems, leading to improved energy efficiency and reduced operational costs in various industries.

However, despite their promising potential, challenges exist in the practical implementation of nanofluids. Issues related to nanoparticle stability, aggregation, and the cost of producing stable nanofluids at large scales are areas that require further research and development. Nonetheless, ongoing studies continue to explore and optimize nanofluid formulations and application techniques to harness their potential benefits for advancing heat transfer technologies.

It has been discovered that nanofluids have greater heat transfer coefficients than their base fluids, which makes them more efficient cooling agents in a range of circumstances. However, there are many drawbacks to using nanofluids in real-world heat exchangers, such as agglomeration, reduced heat transfer, and the expensive price of traditional nanoparticles. The type of base fluid, concentration, size, shape, and composition of the particles all affect how well heat transfer is enhanced by nanofluids. A higher order of magnitude improvement in heat transfer could be achieved by increasing the flow rate inside the heat exchanger than by adding nanoparticles.

1.2.5.1 Analytical Approaches to Understanding Physical Characteristics of Nanofluids

1.2.5.1.1 Density

The density ρn of nanofluids depends upon the base fluid’s density and nanoparticle’s density of nanoparticles. The expression of density can be represented as (Awasthi et al. [28, 29], Agarwal et al.[30]):

(1.1)

In this context, ρf denotes the base fluid’s density, ρp signifies the density of the metal particles, and ϕ is the volume fraction of nanoparticle.

To assess the accuracy of Equation 1.1, experimental investigations were conducted separately by Pak and Cho [31] as well as by Ho et al.[32] to determine the room temperature’s density of Al2O3–water nanofluids. Their findings showcased remarkable conformity between the experimental data and the predictions made through Equation 1.1.

Engineering computations heavily rely on the physical properties observed at various temperatures. Ho et al.[32] conducted density measurements of Al2O3–water nanofluid across different temperature ranges and varying nanoparticle volume fractions. In this study, a correlation for the density of Al2O3–water nanofluid was established, utilizing the experimental data from Ho et al.[32], factoring in temperature and nanoparticle volume fraction. The newly formulated correlation can be denoted as

(1.2)

With a regression R2 of 99.97% and a maximum relative error of 0.22%, this correlation exhibits high precision.

1.2.5.1.2 Viscosity

The expression of viscosity of nanofluids can be written as

(1.3)

Here, μef denotes the base fluid’s density, ϕm the maximum volume fraction that can be attained for spheroidal nanoparticles, and δ the shape parameter of the nanoparticles. According to Agarwal et al.[30], the equivalent volume fractions of the nanoparticles, represented as ϕag, and the fractal index ϕmod can be used to express the aggregate volume fraction of the nanoparticles, denoted as d.

(1.4)

The equivalent volume fractions of the nanoparticles, represented by the ϕmod, can be expressed in this context in terms of the volume fraction (ϕ), the thickness of the interfacial layer (γ), and the lengths of the semi-major and semi-minor axes (b