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Heat Transfer Enhancement
Heat transfer enhancement is the process of increasing the effectiveness of heat exchangers. This can be achieved when the heat transfer power of a given device is increased or when the pressure losses generated by the device are reduced. A variety of techniques can be applied to this effect, including generating strong secondary flows or increasing boundary layer turbulence. Principle During the earliest attempts to enhance heat transfer, plain (or smooth) surfaces were used. This surface requires a special surface geometry able to provide higher values per unit surface area in comparison with a plain surface. The ratio of of an enhanced heat transfer surface to the plain surface is called Enhancement Ratio " E_h ". Thus, E_h= The heat transfer rate for a two-fluid counterflow heat exchanger is given by In order to better illustrate the benefits of enhancement, the total length 'L' of the tube is multiplied and divided in the equation Where is the ove ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant. Flow arrangement Image:Heat_exc_1-1.svg, Fig. 1: Shell and tube heat exchanger, single pass (1–1 parallel f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Transfer
Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, Convection (heat transfer), thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system. Heat conduction, also called diffusion, is the direct microscopic exchanges of kinetic energy of particles (such as molecules) or quasiparticles (such as lattice waves) through the boundary between two systems. When an object is at a different temperature from another body or its surroundings, heat flows so that the body and the surroundings reach the same temperature, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Flow
In fluid dynamics, flow can be decomposed into primary plus secondary flow, a relatively weaker flow pattern superimposed on the stronger primary flow pattern. The primary flow is often chosen to be an exact solution to simplified or approximated (for instance, inviscid) governing equations, such as potential flow around a wing or geostrophic current or wind on the rotating Earth. In that case, the secondary flow usefully spotlights the effects of complicated real-world terms neglected in those approximated equations. For instance, the consequences of viscosity are spotlighted by secondary flow in the viscous boundary layer, resolving the tea leaf paradox. As another example, if the primary flow is taken to be a balanced flow approximation with net force equated to zero, then the secondary circulation helps spotlight acceleration due to the mild imbalance of forces. A smallness assumption about secondary flow also facilitates linearization. In engineering secondary flow also id ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boundary Layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condition (zero velocity at the wall). The flow velocity then monotonically increases above the surface until it returns to the bulk flow velocity. The thin layer consisting of fluid whose velocity has not yet returned to the bulk flow velocity is called the velocity boundary layer. The air next to a human is heated resulting in gravity-induced convective airflow, airflow which results in both a velocity and thermal boundary layer. A breeze disrupts the boundary layer, and hair and clothing protect it, making the human feel cooler or warmer. On an aircraft wing, the velocity boundary layer is the part of the flow close to the wing, where viscous forces distort the surrounding non-viscous flow. In the Earth's atmosphere, the atmospheric boun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two Fluid Counter-flow
2 (two) is a number, numeral and digit. It is the natural number following 1 and preceding 3. It is the smallest and only even prime number. Because it forms the basis of a duality, it has religious and spiritual significance in many cultures. Evolution Arabic digit The digit used in the modern Western world to represent the number 2 traces its roots back to the Indic Brahmic script, where "2" was written as two horizontal lines. The modern Chinese and Japanese languages (and Korean Hanja) still use this method. The Gupta script rotated the two lines 45 degrees, making them diagonal. The top line was sometimes also shortened and had its bottom end curve towards the center of the bottom line. In the Nagari script, the top line was written more like a curve connecting to the bottom line. In the Arabic Ghubar writing, the bottom line was completely vertical, and the digit looked like a dotless closing question mark. Restoring the bottom line to its original horizonta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Transfer Coefficient
In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the proportionality constant between the heat flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference, ). It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per square meter kelvin (W/m2/K). The overall heat transfer rate for combined modes is usually expressed in terms of an overall conductance or heat transfer coefficient, . In that case, the heat transfer rate is: :\dot=hA(T_2-T_1) where (in SI units): *: surface area where the heat transfer takes place (m2) *: temperature of the surrounding fluid (K) *: temperature of the solid surface (K) The general definition of the heat transfer coefficient is: :h = \frac where: *: heat flux (W/m2); i.e., thermal power per unit area, q = d\dot/dA *: difference in temperature bet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Resistance
Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. * (Absolute) thermal resistance ''R'' in kelvins per watt (K/W) is a property of a particular component. For example, a characteristic of a heat sink. * Specific thermal resistance or thermal resistivity ''Rλ'' in kelvin–metres per watt (K⋅m/W), is a material constant. * Thermal insulance has the units square metre kelvin per watt (m2⋅K/W) in SI units or square foot degree Fahrenheit– hours per British thermal unit (ft2⋅°F⋅h/Btu) in imperial units. It is the thermal resistance of unit area of a material. In terms of insulation, it is measured by the R-value. Absolute thermal resistance Absolute thermal resistance is the temperature difference across a structure when a unit of heat energy flows through it in unit time. It is the reciprocal of thermal conductance. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coil Spring Wire Insert
Coil or COIL may refer to: Geometry * Helix * Spiral Science and technology * Coil (chemistry), a tube used to cool and condense steam from a distillation * Coil spring, used to store energy, absorb shock, or maintain a force between two surfaces * Inductor or coil, a passive two-terminal electrical component * Electromagnetic coil, formed when a conductor is wound around a core or form to create an inductor or electromagnet ** Induction coil, a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply *** Ignition coil, used in internal combustion engines to create a pulse of high voltage for a spark plug * Intrauterine device or coil, a contraceptive device * Chemical oxygen iodine laser * Coil, a binary digit or bit in some communication protocols such as Modbus * COIL, the gene that encodes the protein coilin * Coiled tubing Music * Coil (band), an English experimental band * ''Coil'' (album), a 1997 album by Toad the W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twisted Tape Tube Insert
Twisted may refer to: Film and television * ''Twisted'' (1986 film), a horror film by Adam Holender starring Christian Slater * ''Twisted'' (1996 film), a modern retelling of ''Oliver Twist'' * ''Twisted'', a 2011 Singapore Chinese film directed by Chai Yee Wei * ''Twisted'' (2004 film), a thriller starring Ashley Judd and Andy Garcia * ''Twisted'', a parody musical by StarKid Productions * ''Twisted'' (TV series), 2013 * "Twisted" (''Star Trek: Voyager''), a television episode * ''Twisted'' (web series), an Indian erotic thriller web series Software and games * '' Twisted: The Game Show'', a 1994 3DO game * Twisted (software), an event-driven networking framework * '' WarioWare: Twisted!'', a 2005 game for the Game Boy Advance Books * ''Twisted'' (book), a short story collection by crime writer Jeffery Deaver ** ''More Twisted'', a second short story collection by Deaver * '' Twisted'', a novel by Laurie Halse Anderson * ''Twisted'', a ''Pretty Little Liars'' novel by Sar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longitudinal Fins
Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian * Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back * Longitudinal mode, a particular standing wave pattern of a resonant cavity formed by waves confined in the cavity * Longitudinal redundancy check, in telecommunication, a form of redundancy check that is applied independently to each of a parallel group of bit streams. * Longitudinal study, a research study that involves repeated observations of the same items over long periods of time — often many decades * Longitudinal voltage, in telecommunication, a voltage induced or appearing along the length of a transmission medium * Longitudinal wave, a wave with oscillations or vibrations along or parallel to their direction of travel * Longitudinal/longitudinally are also anatomical terms of location. See also * Latitudinal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helical Ribs
Helical may refer to: * Helix, the mathematical concept for the shape * Helical engine, a proposed spacecraft propulsion drive * Helical spring, a coilspring * Helical plc, a British property company, once a maker of steel bar stock * Helicoil A threaded insert, also known as a threaded bushing, is a fastener element that is inserted into an object to add a threaded hole. They may be used to repair a stripped threaded hole, provide a durable threaded hole in a soft material, place a thr ..., a mechanical thread repairing insert * H-el-ical//, stage name for Hikaru, Japanese singer {{disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convection is unspecified, convection due to the effects of thermal expansion and buoyancy can be assumed. Convection may also take place in soft solids or mixtures where particles can flow. Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces. Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be identified by clouds, with stronger convection resulting in thunderstorms. Natural convection also plays a role in stellar physics. Convection is often categorised or d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
