Heat conduction is the process by which thermal energy (heat) is transferred through a material due to a temperature difference. It occurs at the microscopic level as faster-moving particles (atoms or molecules) collide with slower-moving ones, transferring energy in the form of kinetic energy. Key points about heat conduction include: 1. **Mechanism**: Heat conduction occurs primarily in solids, where particles are closely packed. When one part of the material is heated, its particles gain energy and vibrate more vigorously.
High-temperature superconductors (HTS) are materials that exhibit superconductivity at temperatures significantly higher than traditional superconductors, which require cooling to near absolute zero (around -273.15°C or 0 Kelvin). Superconductivity is the phenomenon where a material can conduct electricity without resistance, allowing for the lossless transport of electric current. HTS materials typically become superconducting at temperatures above 77 Kelvin (-196°C), which is the boiling point of liquid nitrogen.
The 3ω-method is a technique used in the field of thermal conductivity measurement, particularly for thin films and materials with small geometries. This method is based on the principles of frequency-domain thermography and utilizes a periodically heated sensor to measure thermal properties. ### Basic Principles: - **Sensor Design**: The technique typically involves a thin metallic line or film, which acts as both a heater and a thermometer. This line is usually deposited onto the material whose thermal properties are to be measured.
Annealed pyrolytic graphite is a type of synthetic graphite that is produced through a high-temperature process known as pyrolysis, where organic materials (usually gas, such as methane) are decomposed in an inert atmosphere to form carbon. The term "annealed" refers to a subsequent heat treatment that enhances the structural properties of the graphite.
The Biot number (Bi) is a dimensionless quantity used in heat transfer calculations to characterize the relationship between conductive and convective heat transfer. It is defined as the ratio of thermal resistance within a body to the thermal resistance at its surface.
Copper is a widely used metal in heat exchangers due to its excellent thermal conductivity, resistance to corrosion, and antimicrobial properties. Here are some key points regarding the use of copper in heat exchangers: 1. **Thermal Conductivity**: Copper has one of the highest thermal conductivities of any commercially available metal, which makes it very effective at transferring heat. This property allows for efficient heat exchange between fluids.
The general equation of heat transfer can be described through different modes of heat transfer: conduction, convection, and radiation. Each mode has its own governing equations, but the principle behind them is the conservation of energy.
The heat equation is a fundamental partial differential equation that describes how the distribution of heat (or temperature) in a given region evolves over time. It is a mathematical model used in various fields such as physics, engineering, and finance to study heat conduction, diffusion, and other related processes.
Heat flux measurements of thermal insulation refer to the quantification of heat transfer through insulating materials under specific conditions. Heat flux is defined as the rate of heat energy transfer per unit area and is typically measured in watts per square meter (W/m²). Understanding heat flux is crucial for evaluating the performance of thermal insulation materials in various applications, such as buildings, industrial processes, and equipment.
A heat pipe is a highly efficient thermal device used for transferring heat from one location to another. It operates on the principle of phase change and convection to move heat away from hot surfaces. Here's a breakdown of how a heat pipe works: ### Structure 1. **Container**: Usually made of metal, the container is sealed and evacuated to create a vacuum. 2. **Working Fluid**: Inside the container, a small amount of liquid (working fluid) is present.
The heat transfer coefficient is a measure of the ability of a material or surface to transfer heat between two fluids or between a fluid and a solid surface. It quantifies the rate of heat transfer per unit area per unit temperature difference between the two entities in contact.
Interfacial thermal resistance, often referred to as thermal interface resistance or thermal boundary resistance, is a measure of the resistance to heat transfer across the interface between two different materials. This phenomenon is significant in various applications, including electronics, thermoelectrics, and materials science, where efficient heat dissipation is crucial.
Internally grooved copper tubes are specialized tubes used primarily in applications that require enhanced heat transfer and improved fluid flow characteristics. These tubes feature a series of longitudinal grooves or indentations on the inner surface, which increases the surface area available for heat exchange and helps to disrupt the layer of fluid adjacent to the tube wall. This disruption reduces thermal boundary layers, allowing for more efficient heat transfer. **Key features and benefits of internally grooved copper tubes include:** 1.
Laser Flash Analysis (LFA) is a technique used primarily to measure the thermal conductivity of materials. It involves heating a sample using a short laser pulse and then measuring the temperature rise on the opposite side of the sample over time. The key components of the LFA method include: 1. **Sample Preparation**: The material being tested is typically in the form of a thin disc or pellet, which should be uniform in thickness and density.
A Loop Heat Pipe (LHP) is a highly efficient thermal management system that is used to transfer heat from a heat source to a heat sink over relatively long distances with minimal temperature drop. It works through a passive mechanism, utilizing the principles of phase change and capillary action to circulate a working fluid. ### Key Components of a Loop Heat Pipe: 1. **Evaporator**: This is where the heat is absorbed from the heat source.
Multi-layer insulation (MLI) is a thermal insulation technology commonly used in spacecraft, satellites, and other applications where thermal control is critical, particularly in the vacuum of space. The primary purpose of MLI is to minimize heat transfer between different areas, especially to protect sensitive equipment from extreme temperatures. ### Structure: MLI consists of multiple layers of thin, shiny materials—usually metallic and non-metallic films—separated by small spacers.
Newton's Law of Cooling describes the rate at which an exposed body changes temperature through radiation and convection with its surroundings. Specifically, it states that the rate of heat loss of a body is proportional to the difference in temperature between the body and its environment, provided this temperature difference is small.
The Péclet number (Pe) is a dimensionless number used in fluid mechanics and heat transfer to characterize the relative importance of advection and diffusion in a flowing system. It is defined as the ratio of the rate of advective transport of a quantity (such as heat or mass) to the rate of diffusive transport of that same quantity.
Searle's bar method is an experimental technique used in materials science and engineering to measure the mechanical properties of materials, particularly the yield strength and elastic modulus of materials in a way that allows for precise control and measurement. It is named after physicist John Searle. The method involves placing a small, slender bar (the specimen) under tensile load, usually with two points of support at either end.
The table of specific heat capacities lists the specific heat capacities of various substances. Specific heat capacity is a physical property that indicates how much heat energy is required to raise the temperature of a unit mass of a substance by one degree Celsius (°C) or one Kelvin (K). The specific heat capacity can vary depending on the phase of the substance (solid, liquid, or gas) and can also change with temperature.
Thermal conductance quantum refers to a quantized unit of thermal conductance, usually expressed in the context of nanoscale and mesoscopic systems where quantum effects become significant. In these systems, heat transfer does not necessarily follow classical laws, and the discrete nature of heat carriers can lead to interesting phenomena.
Thermal conductivity is a physical property of a material that measures its ability to conduct heat. It quantifies how well heat energy can transfer through a material when there is a temperature gradient. Materials with high thermal conductivity can quickly transfer heat, while those with low thermal conductivity are better insulators.
Thermal diffusivity is a material property that indicates how quickly heat can spread through a material. It is defined as the ratio of thermal conductivity to the product of density and specific heat capacity.
Thermal effusivity is a property of materials that describes their ability to conduct and store thermal energy. It is a measure of how well a material can exchange heat with its surroundings or with another material when they come into contact.
Thermal paste, also known as thermal compound, thermal grease, or thermal interface material (TIM), is a substance used to enhance the thermal conductivity between two surfaces, typically in electronic devices including CPUs, GPUs, and heat sinks. Its primary function is to fill microscopic gaps between the surfaces of these components, enabling more efficient heat transfer.
Thermal resistance is a measure of a material's ability to resist the flow of heat. It quantifies how well a material or a system conducts thermal energy and is often used in the context of thermal insulation and heat transfer.
A thermally conductive pad is a type of material designed to efficiently transfer heat from one surface to another. These pads are typically made from materials that have high thermal conductivity, such as silicone, graphite, metals, or specialized composites. They are commonly used in electronics to manage heat dissipation from components like CPUs, GPUs, power transistors, and various other devices that generate heat during operation.
The Transient Hot Wire (THW) method is a technique used to measure the thermal conductivity of materials, particularly solids and liquids. It is based on the transient response of a thin wire that has an electric current passing through it, which heats up due to electrical resistance. The key features of the THW method include: ### Principles of Operation 1. **Heating the Wire**: A thin wire, typically a metal, is inserted into the material whose thermal conductivity is to be measured.
The Wiedemann–Franz law is a principle in solid-state physics and materials science that relates the electrical conductivity of a metal to its thermal conductivity. It states that the ratio of the thermal conductivity (\(K\)) to the electrical conductivity (\(\sigma\)) of a metal is proportional to the temperature (\(T\)).
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