Adiabatic Cooling
|
Adiabatic cooling occurs when the pressure of a substance is decreased as it does work on its surroundings. Adiabatic cooling does not have to involve a fluid.
|
Adsorption
|
A process that occurs when a gas or liquid solute accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the adsorbate). Most industrial adsorbents fall into one of three classes: 1. Oxygen-containing compounds (e.g.silica gel and zeolites 2. Carbon-based compounds (e.g. activated carbon and graphite) 3. Polymer-based compounds
|
Adsorption Refrigerator
|
A refrigerator that uses a heat source to provide the energy needed to drive the cooling system. Sometimes used where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is available (e.g., from turbine exhausts or industrial processes, or from solar plants).
|
Aeration
|
The process by which air is circulated through, mixed with or dissolved in a liquid or substance.
|
Aerosol
|
A suspension of fine solid particles or liquid droplets in a gas.
|
Bong Cooler
|
A bong-shaped device that is able to cool water to temperatures below room temperature (sub-ambient) via evaporative cooling.
|
Conduction (thermal)
|
The spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature. Conduction acts to equalize temperature differences. It is also described as heat energy transferred from one material to another by direct contact.
|
Cooling
|
The act of reducing temperature.
|
Cryogenics
|
The behavior of materials at very low temperatures (typically below -150 °C, -238 °F or 123 K).
|
Cryolysis
|
Destruction by cold (usually in a medical context)
|
Curie Point (ferromagnetic)
|
The Curie point of a ferromagnetic material is the temperature above which it loses its characteristic ferromagnetic ability
|
The ferromagnetic 'phase change' that occurs at the Curie Point requires (or releases) energy in the form of heat.
|
Electrocaloric Effect
|
A phenomenon in which a material shows a reversible temperature change under an applied electric field. Often considered the physical inverse of the pyroelectric effect. The effect comes from the voltage raising or lowering the entropy of the system. Analogous to the magnetocaloric effect.
|
Endothermic Reaction
|
A process or reaction that absorbs energy typically (but not always) in the form of heat. The concept is frequently applied in physical sciences to e.g. chemical reactions, where thermal energy (heat) is converted to chemical bond energy.
|
Evaporation
|
The change of the physical state of aggregation (or simply state) of matter from liquid phase to gaseous phase.
|
Evaporative Cooler
|
A device that cools air through the evaporation of water. Evaporative cooling works by employing water's large enthalpy of vaporisation.
|
Fan
|
A device used to produce flow in a gas (and, in principle, a liquid). Mechanical revolving blade fans are made in a wide range of designs. There are three main types of fans used for moving air, axial, centrifugal (also called radial) and cross flow (also called tangential).
|
Fluid Spray
|
When a liquid is dispersed as a stream of droplets (atomisation), it is called a spray. Spray nozzles are used to achieve two primary functions: increase liquid surface area to enhance evaporation, or distribute a liquid over an area.
|
Free Fall
|
The motion of a body where gravity is the only or dominant force acting upon it, at least initially.
|
Freezing
|
A phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. Colloquially it is applied to water, but technically it applies to any liquid. All known liquids, except liquid helium, freeze when the temperature is lowered enough.
|
Fusible Alloy
|
A fusible alloy is one that is capable of being fused, as well as being liquefied by heat. Examples: Wood's metal, Field's metal, Rose metal, Galinstan, NaK.
|
The melting of a fusible alloy (phase change from solid to liquid) requires heat
|
Graphene
|
A one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. It can be visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The name comes from graphite + -ene; graphite itself consists of many graphene sheets stacked together.
|
Graphene has exceptionally good heat conduction properties.
|
Heat Exchanger
|
A device built for efficient heat transfer from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact
|
Heat Pipe
|
A heat pipe is a heat transfer mechanism that can transport heat with a very small difference in temperature between the hotter and colder interfaces. Inside a heat pipe, at the hot interface a fluid turns to vapour and the gas naturally flows and condenses on the cold interface. The liquid falls or is moved by capillary action back to the hot interface to evaporate again and repeat the cycle.
|
Heat Sink
|
A component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid.
|
Incandescence
|
The emission of light (visible electromagnetic radiation) from a hot body due to its temperature.
|
Infrared Radiation
|
Infrared (IR) radiation is electromagnetic radiation whose wavelength is longer than that of visible light (400-700 nm), but shorter than that of terahertz radiation (3-300 µm) and microwaves (~30,000 µm). Infrared radiation spans roughly three orders of magnitude (750 nm and 1000 µm).
|
By emission of Infrared Radiation.
|
Intumescent Materials
|
An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection.
|
Latent Heat
|
Energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process. An example is a state of matter change, meaning a phase transition, such as ice melting or water boiling.
|
Loop Heat Pipe
|
A two-phase heat transfer device that uses capillary action to remove heat from a source and passively move it to a condenser or radiator. Similar to heat pipe but has advantage of being able provide reliable operation over long distance and ability to operate against gravity. Designs range from powerful & large to miniature (micro loop heat pipe). Widely used in both ground based as well as space applications.
|
Magnetic Refrigeration
|
A cooling technology based on the magnetocaloric effect. This technique can be used to attain extremely low temperatures (well below 1 K), as well as the ranges used in common refrigerators, depending on the design of the system.
|
Magnetocaloric Effect
|
(or Magnetothermal Effect) A magneto-thermodynamic phenomenon in which a reversible change in temperature of a suitable material is caused by exposing the material to a changing magnetic field. Also known as adiabatic demagnetisation. Can be used to attain extremely low temperatures (well below 1 K), as well as the ranges used in common refrigerators.
|
Melting
|
A process that results in the phase change of a substance from a solid to a liquid. The internal energy of a solid substance is increased (typically by the absorbtion of heat) to a specific temperature (called the melting point) at which it changes to the liquid phase.
|
Melting is endothermic
|
Mixed Convection
|
Movement of fluids or gases (or particles carried by fluids or gasses) by a combination of Free and Forced Convection
|
Peltier Effect
|
Heat is evolved or absorbed at the junction of two dissimilar metals carrying a small current, depending upon the direction of the current. One of a number of thermoelectric effects (See Seebeck Effect and Thompson Effect).
|
Phase Change
|
The transformation of a thermodynamic system from one phase to another. Most commonly used to describe transitions between solid, liquid and gaseous states of matter, in rare cases including plasma.
|
Pulse Tube Refrigerator
|
A type of cryocooler having no moving parts in the low temperature part of the device making it suitable for a wide variety of applications.
|
Reflection
|
The change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves.
|
Refractory Material
|
A (typicaly non-metallic) material that retains its strength at high temperatures. Refractory materials are used in linings for furnaces, kilns, incinerators and reactors. They are also used to make crucibles.
|
Righi-Leduc Effect
|
A magnetic field applied at right angles to the the direction of a temperature gradient in an electrical conductor will produce a temperature difference at right angles to the direction of both the temperature gradient and the magnetic field.
|
Rubber Band Thermodynamics
|
Stretching a rubber band will cause it to release heat, while releasing it after it has been stretched will lead it to absorb heat, causing its surroundings to become cooler. Heating causes a rubber band to contract, and cooling causes expansion.
|
Second Sound
|
A quantum mechanical phenomenon in which heat transfer occurs by wave-like motion, rather than by the more usual mechanism of diffusion. Heat takes the place of pressure in normal sound waves. This leads to a very high thermal conductivity. It is known as 'second sound' because the wave motion of heat is similar to the propagation of sound in air.
|
Stirling Cycle
|
A thermodynamic cycle that describes the general class of Stirling devices. The cycle is reversible: if supplied with mechanical power, it can function as a heat pump for heating or refrigeration cooling, or cryogenic cooling. The cycle is a closed-cycle (the working fluid is permanently contained within the thermodynamic system) regenerative (uses an internal heat exchanger) cycle with a gaseous working fluid.
|
Sublimation
|
The change of the physical state of aggregation (or simply state) of matter directly from solid phase to gaseous phase without passing through an intermediate liquid phase.
|
By latent heat of sublimation.
|
Supercritical Fluid
|
Any substance at a temperature and pressure above its critical point. It can diffuse through solids like a gas, and dissolve materials like a liquid. Additionally, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties to be 'tuned'.
|
Thermal Hall Effect
|
The thermal analog of the Hall effect, i.e. a thermal gradient is produced across a solid instead of an electric field. When a magnetic field is applied, an orthogonal temperature gradient develops. For conductors, a significant portion of the thermal current is carried by the electrons. In particular, the Righi-Leduc Effect describes the heat flow resulting from a perpendicular temperature gradient and vice versa, and the Maggi-Righi-Leduc effect describes changes in thermal conductivity when placing a conductor in a magnetic field.
|
Thermal Radiation
|
Electromagnetic radiation emitted from the surface of an object due to the object's temperature.
|
A radiating object will lose energy.
|
Thermionic Emission
|
Emission of electrons or ions caused by thermal vibrational energy . Also known as the Edison Effect.
|
Thermoacoustic Effect
|
Acoustic waves can be used for heat transfer. The pressure variations in the acoustic wave are accompanied by temperature variations due to compressions and expansions of the gas which, being inherantly associated with a displacement, results in a net transfer of heat. Direction of heat flow can be fixed by, for example, a standing wave pattern generated by an acoustic resonator.
|
Thermoacoustic Engine
|
Thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or use a heat difference to induce high-amplitude sound waves. Can be divided into standing wave and travelling wave devices. These two types can again be divided in two thermodynamic classes, a prime mover (or simply heat engine), and a heat pump. The prime mover creates work using heat and a heat pump creates or moves heat using work.
|
Thermoacoustics
|
The interaction between thermodynamic and acoustic phenomena, for example the relation between pressure changes, and temperature changes. A dynamic pressure would cause a dynamic temperature and vice versa.
|
Thermolysis
|
(or Thermal decomposition) A chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition. If decomposition is sufficiently exothermic, a positive feedback loop is created producing thermal runaway and possibly an explosion.
|
Thermolysis is usually endothermic.
|
Thermomagnetic Convection
|
Ferrofluids can be used to transfer heat, since heat and mass transport in such magnetic fluids can be controlled using an external magnetic field.
|
Thermosyphon
|
A method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump. Can either be open-loop, as when liquid in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point - even one mounted above the originating tank - or it can be a vertical closed-loop circuit with return to the original vessel.
|
Thompson Effect
|
The heating or cooling of a current-carrying conductor with a temperature gradient Depending on the material it may cause heating or cooling. One of a number of thermoelectirc effects (see Seebeck effect and Peltier Effect).
|
Wind
|
The flow of air or other gases that compose an atmosphere
|
