Adrian Bejan's Blog, page 5

Adrian Bejan I Diversity, Bismarck & Civilization, from Design in Nature

In this video, Adrian Bejan discusses the concept of design in nature, exploring the configurations of systems that can move and evolve. He emphasizes the importance of diversity and innovation, linking it to historical references such as Bismarck's perspective on politics and how it reflects the desire to improve systems. He advocates for understanding designs' essence, evolution, and impact on civilization.

Design in Nature

Bejan introduces the concept of design in nature as the configurations of things that move, explaining that this concept covers everything in existence and correlates with evolution and design improvement.

Importance of Diversity

He discusses how variations in designs lead to diversity and presents this diversity as vital for progress, emphasizing that the essence of successful designs lies in their ability to adapt and improve.

Bismarck and Political Art

Referencing Otto von Bismarck, Bejan connects the concept of engineering designs to politics, suggesting that just as Bismarck worked to unify Germany, engineers strive to innovate and refine their designs for better functionality.

Politics as Civilization

Bejan challenges negative perceptions of politics by linking it to civilization, stating that politics historically represented the management and improvement of communities, akin to engineering.

Evolutionary Design

He highlights the role of engineers as constant innovators who seek to improve things. Bejan describes this as 'evolutionary design'—a relentless pursuit of improvement in system configurations.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Rivers and Earthworms, from Design in Nature

In this video, Adrian Bejan discusses the design of river cross-sections and how their shapes impact flow efficiency. Through a mathematical and historical exploration, he illustrates the optimal geometric shapes that allow for better water flow, including triangular and circular shapes, comparing their physical properties and mathematical implications.

Optimal Cross-Section Shapes

Bejan explains that the optimal shape for river cross-sections can facilitate easier water flow. He uses mathematical equations to derive relationships between width and depth to determine the most efficient configurations, focusing particularly on triangular and circular shapes.

Mathematics of River Flow

The discussion includes the mathematical understanding of cross-sectional areas and perimeters, emphasizing the significance of minimizing the perimeter in achieving efficient designs. Various geometric forms are compared, noting that a circular cross-section generally provides the best flow characteristics.

Natural Erosion and Design Effects

Natural erosion processes are highlighted as factors that influence the shape of riverbanks. Bejan suggests that sharp corners in river designs are eroded over time, leading to more rounded and natural shapes that improve flow.

Subterranean Water Flow

An exploration of subterranean river flows is provided, illustrating how natural shapes, like rounded pipes formed by water erosion, create efficient underground water channels. This serves as a foundation for understanding both surface and underground water dynamics.

Connections Between Shapes and Nature

The lecture draws analogies between river cross-sections and designs found in nature. Bejan discusses the unexpected similarities between the shapes of river flows and biological forms, such as earthworms, suggesting a natural underpinning to these forms in fluid dynamics.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Wide rivers should be deep, from Design in Nature

In this lecture by Adrian Bejan, the dynamics of river flow and the importance of river depth are discussed. The focus is on how gravitational forces drive water flow down a river channel and the impact of channel shape and surface roughness on flow resistance. Bejan explains mathematical relationships that govern the behavior of rivers and offers insights into why rivers should be designed to be deep for optimal flow.

Gravity Drives River Flow Bejan explains that river flow is primarily driven by gravity rather than pressure differences. The weight of the water creates a component that pushes water downhill, influencing the overall dynamics of river movement.

Key Mathematical Relationships The lecture delves into various mathematical concepts and details how they relate to river fluid dynamics. The force balance involves shear stress and weight components, forming a foundation for understanding river flow.

Impact of Channel Shape The shape of a river channel, particularly its cross-section, significantly affects flow resistance and efficiency. A proper channel shape can maximize flow by reducing resistance, thus allowing deeper rivers to form.

Friction Factors and Flow Resistance Bejan discusses how the friction factor is essential in determining flow resistance within a river. When considering flow dynamics, the impacts of rough surfaces, such as boulders found in mountainous rivers, are emphasized.

Historical Context of Rivers and Mountains The relationship between the age of rivers and the geological formation of mountains is explored, providing insights into why rivers often have deep channels. Older rivers erode the landscape over time, resulting in distinct geographic features. Such insights redefine our understanding of river morphology.

Optimal River Design The lecture concludes with recommendations for designing river systems to be deeper and more efficient, emphasizing the importance of minimizing the wetted perimeter for improved flow accessibility.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Technique, from Design in Nature

Adrian Bejan discusses the importance of technique in problem-solving and reporting. He emphasizes that technique is personal, learned through experience, and essential in various fields. Using examples from nature, he illustrates that deeper rivers are typically wider, presenting a phenomenon worth exploring. Bejan encourages students to adopt a mindset of curiosity and continuous improvement by questioning their assumptions and learning from comparisons.

Importance of technique

Technique is viewed as an essential approach to problem-solving, emphasizing that it is personal and involves learned methods. Individuals are encouraged to develop unique techniques based on past experiences, much like athletes in sports.

Phenomena in nature

Bejan discusses the observation that wide rivers are typically deeper, illustrating a phenomenon that can be analyzed and understood through technique. This example highlights the importance of recognizing patterns in nature and applying them to problem-solving.

Reporting techniques

Effective reporting is critical across various fields, requiring clarity and respect for the audience. Bejan stresses the importance of communicating findings and solutions, suggesting that methodical comparison and learning from feedback improve one's ability to report effectively.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Unlocking nature’s secret behind energy and patterns

Most of us know that over time, things change, water flows, rocks fall, living creatures grow, and weather patterns shift. Scientists have long tried to explain these changes with the laws of thermodynamics—especially something called the ‘second law,’ which talks about how useful energy becomes less available (or how processes are irreversible). But there is more to the story of how nature changes (or ‘evolves’) than just energy flowing downhill.

This article introduces two important ideas, irreversibility and evolution:

Irreversibility, guided by the second law of thermodynamics (energy flows happen in one direction, and you can’t fully undo them).

Evolution of shape and design, guided by the constructal law (natural systems change their form over time in ways that make it easier for them to move, flow, and persist).

They are distinct, self-standing, not the same thing.

Read more on theacademic.com

Adrian Bejan I Economies of Scale, Air Conditioning, from Design in Nature

Adrian Bejan discusses economies of scale in air conditioning systems, primarily focusing on how duct design affects pressure drops and efficiency. He explains the connection between tube diameters and the resulting pressure loss, emphasizing that larger tubes can significantly minimize energy waste in air conditioning systems. He highlights the revolutionary effect of air conditioning, crediting its invention to Willis Carrier, and reflects on the significance of technology in enhancing comfort and productivity.

Pressure Drop in Ducts: The video explains that the diameter of the tubes significantly influences the pressure drop (Delta P) in a duct system. Smaller tubes result in a greater pressure drop, whereas larger tubes considerably reduce it, underscoring the importance of proper design in ventilation systems.

Comparison of Duct Systems: Bejan compares two duct systems: a single larger duct and two smaller parallel ducts. He mathematically demonstrates how the pressure drop in the system with two ducts can be halved compared to that of a single duct, highlighting the benefits of utilizing multiple ducts for efficiency.

Willis Carrier's Contribution: The discussion emphasizes the crucial role of Willis Carrier, who invented the air conditioner, marking a technological revolution. Bejan notes that air conditioning has revolutionized workplaces and living environments in hot climates, enhancing comfort and productivity.

Impact of Air Conditioning: Adrian Bejan concludes by reflecting on the broader societal impact of air conditioning. He suggests that it has created new opportunities for work and life in previously inhospitable climates, thereby shaping modern life.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Possible, Impossible, Diversity, from Design in Nature

In this video, Adrian Bejan explores the fundamental principles that govern the movement of fluids and energy in natural and engineering systems. He discusses the application of Constructal Law, which explains how flow systems evolve easier and greater access to what flows. The video examines the evolution of natural flows, illustrating how designs such as river networks, blood circulation, and engineering systems follow universal patterns to minimize resistance and maximize efficiency. In addition, Bejan explores the concept of economies of scale, emphasizing how a larger, organized flow can outperform multiple smaller channels.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I da Vinci, Galilei, Newton, from Design in Nature

The video explores Leonardo da Vinci's life and legacy. It highlights his self-taught thinking and innovations, which laid the foundation for modern science. The video discusses his philosophical writings, inventions, and impact on subsequent scientists like Galileo and Newton.

Da Vinci's Background: Leonardo da Vinci was an illegitimate child raised by his grandmother in a village near Florence. Despite lacking formal education, he became a renowned self-taught thinker who significantly contributed to art and science.

Notebooks of Da Vinci: After his death, Da Vinci's marginal notes and sketches were compiled into famous notebooks. These contain philosophical musings and annotations that reveal his insights on art, mechanics, and the essence of life.

Maxims and Mechanics: Da Vinci's maxims showcase his grasp of mechanics. For example, he identified four external forces that influence visible actions and connected them to the core principles of mechanics.

Motive Power and Life: He proposed that 'Motive Power' is essential for life, suggesting that all movement, which signifies life, is driven by power. This notion is fundamental in understanding the principles of motion.

The Importance of Language: Da Vinci's work precedes and influences notable scientists like Galileo and Newton, underscoring how he communicated complex ideas through images and words rather than mathematics.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Size of Heat Exchanger, from Design in Nature

In this video, Adrian Bejan discusses the principles of heat exchangers, focusing on their design and efficiency. He explores how size and geometry affect heat transfer and the energy costs associated with heating systems. Using various examples and formulas, he illustrates the relationship between the heat exchanger's area, thickness, and overall efficiency in fuel consumption and power dissipation.

Basics of Heat Exchangers

Bejan introduces the concept of heat exchangers and explains their function in transferring heat from a hot fluid to a cold fluid, emphasizing the importance of the surface separating these fluids.

Weight and Size Considerations

He discusses the significance of the heat exchanger's weight and size in vehicles' overall energy consumption, highlighting that heavier vehicles require more power due to friction and drag.

Heat Transfer Efficiency

The video elaborates on the principles of heat transfer, specifically how the power dissipation rate is proportional to the heat transfer area and the temperature difference between the fluids.

Cost Implications in Design

Bejan stresses that size matters in heat exchanger design. Larger surface areas can result in more efficient heat transfer and higher costs, necessitating a balance between these factors.

Historical Context

He provides a historical perspective on the evolution of scientific thought, alluding to the contributions of Da Vinci, Galileo, and Newton in shaping modern science.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com

Adrian Bejan I Carnot Efficiency Impossibility, from Design in Nature

In this video, Adrian Bejan explores the concept of Carnot efficiency and its status as an unattainable ideal in practical systems. He outlines the historical development of engines, beginning with the early steam engines and continuing with James Watt's innovations that enhanced efficiency. Bejan underscores the significance of grasping thermodynamic principles, especially the laws governing heat transfer, energy loss, and the unavoidable imperfections within engine systems. He clarifies that while Carnot’s theoretical efficiency represents the maximum possible, real engines face limitations due to material properties, heat escapes, and design obstacles that hinder reaching this ideal. Through practical examples, Bejan demonstrates how power is transmitted and lost across different systems, ranging from animal movement to large energy plants, emphasizing the inevitable losses attributed to thermal conductivity and structural constraints.

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Umit Gunes, Ph.D.
Assoc. Prof., Yildiz Technical University
umitgunes.com