Adiabatic Cooling
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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.
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Capillary Condensation
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The process by which multilayer adsorption from the vapour phase into a porous medium proceeds to the point at which pore spaces become filled with condensed liquid from the vapour phase. The unique aspect of capillary condensation is that vapor condensation occurs below the saturation vapor pressure of the pure liquid. Can affect contact between solids, modifying macroscopic adhesion & friction properties.
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Compression
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The result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is tension. In simple terms, compression is a pushing force.
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Condensation
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The change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase.
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Conduction (thermal)
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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.
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Cooling
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The act of reducing temperature.
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Deposition (physical)
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A process in which gas transforms into solid (also known as desublimation). The reverse of deposition is sublimation. One example of deposition is the process by which, in sub-freezing air, water vapour changes directly to ice without first becoming a liquid. This is how snow forms in clouds, as well as frost and hoar frost on the ground.
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Endothermic Reaction
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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.
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Joule-Thomson Effect
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The temperature change of a gas resulting from expansion without production of work or the transfer of heat. For example, when a gas or liquid is forced through a valve or porous plug while kept insulated.
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Nucleation
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The extremely localised budding of a distinct thermodynamic phase. Some examples of phases that may form via nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation. Most nucleation processes are physical, rather than chemical, but a few exceptions do exist (e.g. electrochemical nucleation).
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Peltier Effect
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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).
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Through cooling of the gas
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Phase Change
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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.
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Phase Changes are exothermic or endothermic and can be used to trigger other phase changes.
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Porosity
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The quality of being porous - i.e. having voids or spaces within a solid substance within or through which fluids can be present.
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Pressure Increase
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Pressure is an effect which occurs when a force is applied on a surface. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point.
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Radiation
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A process in which energetic particles or waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing.
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Through cooling of the radiating gas.
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Supercritical Fluid
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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'.
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Temperature Gradient
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The variation in temperature over distance.
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Thermal Radiation
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Electromagnetic radiation emitted from the surface of an object due to the object's temperature.
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A hot gas cools as a result of the loss of energy required to generate the thermal radiation.
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Vapour Cone
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(also referred to as shock collar, or shock egg) The creation of a visible condensation cloud caused by a sudden drop in air pressure. Occurs under the right atmospheric conditions - for example by an aircraft traveling at transonic speeds.
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