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Overheating (electricity)
Overheating is a phenomenon of rising temperatures in an electrical circuit. Overheating causes damage to the circuit components and can cause fire, explosion, and injury. Damage caused by overheating is usually irreversible; the only way to repair it is to replace some components. Causes When overheating, the temperature of the part rises above the operating temperature. Overheating can take place: *if heat is produced in more than expected amount (such as in cases of short-circuits, or applying more voltage than rated), or *if heat dissipation is poor, so that normally produced waste heat does not drain away properly. Overheating may be caused from any accidental fault of the circuit (such as short-circuit or spark-gap), or may be caused from a wrong design or manufacture (such as the lack of a proper heat dissipation system). Due to accumulation of heat, the system reaches an equilibrium of heat accumulation vs. dissipation at a much higher temperature than expected. Preventiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Circuit
An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, current sources, resistances, inductances, capacitances). An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Linear electrical networks, a special type consisting only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines), have the property that signals are linearly superimposable. They are thus more easily analyzed, using powerful frequency domain methods such as Laplace transforms, to determine DC response, AC response, and transient response. A resistive circuit is a circuit containing only resistors and ideal current and voltage sources. Analysis of resistive circuits is less compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conflagration
A conflagration is a large fire. Conflagrations often damage human life, animal life, health, and/or property. A conflagration can begin accidentally, be naturally caused (wildfire), or intentionally created (arson). A very large fire can produce a firestorm, in which the central column of rising heated air induces strong inward winds, which supply oxygen to the fire. Conflagrations can cause casualties including deaths or injuries from burns, trauma due to collapse of structures and attempts to escape, and smoke inhalation. Firefighting is the practice of extinguishing a conflagration, protecting life and property and minimizing damage and injury. One of the goals of fire prevention is to avoid conflagrations. When a conflagration is extinguished, there is often a fire investigation to determine the cause of the fire. Causes and types During a conflagration a significant movement of air and combustion products occurs. Hot gaseous products of combustion move upward, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoelectric Cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC) and occasionally a thermoelectric battery. It can be used either for heating or for cooling, although in practice the main application is cooling. It can also be used as a temperature controller that either heats or cools. This technology is far less commonly applied to refrigeration than vapor-compression refrigeration is. The primary advantages of a Peltier cooler compared to a vapor-compression refrigerator are its lack of moving parts or circulating liquid, very long life, invulnerability to leaks, smal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Runaway
Thermal runaway describes a process that is accelerated by increased temperature, in turn releasing energy that further increases temperature. Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. It is a kind of uncontrolled positive feedback. In chemistry (and chemical engineering), thermal runaway is associated with strongly exothermic reactions that are accelerated by temperature rise. In electrical engineering, thermal runaway is typically associated with increased current flow and power dissipation. Thermal runaway can occur in civil engineering, notably when the heat released by large amounts of curing concrete is not controlled. In astrophysics, runaway nuclear fusion reactions in stars can lead to nova and several types of supernova explosions, and also occur as a less dramatic event in the normal evolution of solar-mass stars, the "he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Resistance In Electronics
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. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Management Of High-power LEDs
High power light-emitting diodes (LEDs) can use 350 milliwatts or more in a single LED. Most of the electricity in an LED becomes heat rather than light (about 70% heat and 30% light). If this heat is not removed, the LEDs run at high temperatures, which not only lowers their efficiency, but also makes the LED less reliable. Thus, thermal management of high power LEDs is a crucial area of research and development. It is necessary to limit both the junction and the phosphor particles temperatures to a value that will guarantee the desired LED lifetime. Thermal management is a universal problem having to do with power density, which occurs both at higher powers or in smaller devices. Many lighting applications wish to combine a high light flux with an extremely small light emitting substrate, causing concerns with LED power management to be particularly acute. Heat transfer procedure In order to maintain a low junction temperature to keep good performance of an LED, ev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Management Of Electronic Devices And Systems
All electronic devices and circuitry generate excess heat and thus require thermal management to improve reliability and prevent premature failure. The amount of heat output is equal to the power input, if there are no other energy interactions. There are several techniques for cooling including various styles of heat sinks, thermoelectric coolers, forced air systems and fans, heat pipes, and others. In cases of extreme low environmental temperatures, it may actually be necessary to heat the electronic components to achieve satisfactory operation. Overview Thermal resistance of devices This is usually quoted as the thermal resistance from junction to case of the semiconductor device. The units are °C/W. For example, a heatsink rated at 10 °C/W will get 10 °C hotter than the surrounding air when it dissipates 1 Watt of heat. Thus, a heatsink with a low °C/W value is more efficient than a heatsink with a high °C/W value. Given two semiconductor devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Design Power
The thermal design power (TDP), sometimes called thermal design point, is the maximum amount of heat generated by a computer chip or component (often a CPU, GPU or system on a chip) that the cooling system in a computer is designed to dissipate under any workload. Some sources state that the peak power rating for a microprocessor is usually 1.5 times the TDP rating. Intel has introduced a new metric called ''scenario design power'' (SDP) for some Ivy Bridge Y-series processors. Calculation The ''average CPU power'' (ACP) is the power consumption of central processing units, especially server processors, under "average" daily usage as defined by Advanced Micro Devices (AMD) for use in its line of processors based on the K10 microarchitecture ( Opteron 8300 and 2300 series processors). Intel's thermal design power (TDP), used for Pentium and Core 2 processors, measures the energy consumption under high workload; it is numerically somewhat higher than the "average" ACP ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics. A radiator is always a source of heat to its environment, although this may be for either the purpose of heating this environment, or for cooling the fluid or coolant supplied to it, as for automotive engine cooling and HVAC dry cooling towers. Despite the name, most radiators transfer the bulk of their heat via convection instead of thermal radiation. History The Roman hypocaust is an early example of a type of radiator for building space heating. Franz San Galli, a Prussian-born Russian businessman living in St. Petersburg, is credited with inventing the heating radiator around 1855, having received a radiator patent in 1857, but American Joseph Nason developed a primitive radiator in 1841 and received a number of U.S. patents for hot water and steam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oil Cooling
Oil cooling is the use of engine oil as a coolant, typically to remove surplus heat from an internal combustion engine. The hot engine transfers heat to the oil which then usually passes through a heat-exchanger, typically a type of radiator known as an oil cooler. The cooled oil flows back into the hot object to cool it continuously. Usage Oil cooling is commonly used to cool high-performance motorcycle engines that are not liquid-cooled. Typically, the cylinder barrel remains air-cooled in the traditional motorcycle fashion, but the cylinder head benefits from additional cooling. As there is already an oil circulation system available for lubrication, this oil is also piped to the cylinder head and used as a liquid coolant. Compared to an oil system used solely for lubrication, oil cooling requires additional oil capacity, a greater flow rate through the oil pump, and an oil cooler (or a larger cooler than normal). If air-cooling proves sufficient for much of the running t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Spreader
A heat spreader transfers energy as heat from a hotter source to a colder heat sink or heat exchanger. There are two thermodynamic types, passive and active. The most common sort of passive heat spreader is a plate or block of material having high thermal conductivity, such as copper, aluminum, or diamond. An active heat spreader speeds up heat transfer with expenditure of energy as work supplied by an external source. A heat pipe uses fluids inside a sealed case. The fluids circulate either passively, by spontaneous convection, triggered when a threshold temperature difference occurs; or actively, because of an impeller driven by an external source of work. Without sealed circulation, energy can be carried by transfer of fluid matter, for example externally supplied colder air, driven by an external source of work, from a hotter body to another external body, though this is not exactly heat transfer as defined in physics. Exemplifying increase of entropy according to the secon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Pump
A heat pump is a device that can heat a building (or part of a building) by transferring thermal energy from the outside using a refrigeration cycle. Many heat pumps can also operate in the opposite direction, cooling the building by removing heat from the enclosed space and rejecting it outside. Units that only provide cooling are called air conditioners. When in heating mode, a refrigerant at outside temperature is being compressed. As a result, the refrigerant becomes hot. This thermal energy can be transferred to an indoor unit. After being moved outdoors again, the refrigerant is decompressed — evaporated. It has lost some of its thermal energy and returns colder than the environment. It can now take up the surrounding energy from the air or from the ground before the process repeats. Compressors, fans, and pumps run with electric energy. Common types are air-source heat pumps, ground-source heat pumps, water-source heat pumps and exhaust air heat pumps. They ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
