The autoignitiontemperature or kindling point of a substance is the lowest temperature at which it will Spontaneous combustion spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion . The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture. Autoignition temperatures of liquid chemicals are typically measured using a 500 mL flask placed in a temperature controlled oven in accordance with the procedure described in ASTM E659. ref E659 78 Reapproved 2000 , Standard Test Method for AutoignitionTemperature of Liquid Chemicals , ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428 2959 ref Autoignition equation The time math t ig , math it takes for a material to reach its autoignitiontemperature math T ig , math when exposed to a heat flux math q , math is given by the following equation math t ig left frac pi 4 right left k rho c right left frac T ig T o q right 2 math ref Principles of Fire Behavior. ISBN 0 8273 7732 0. 1998. ref where k thermal conductivity W m K , density kg m , and c specific heat capacity J kg K of the material of interest. math T o , math is the temperature, in kelvins, the material starts at or the temperature of the bulk material , and math q , math is the heat flux W m incident to the material. To be consistent in units the group math left frac T ig T o q right math should be squared. Autoignition point of selected substances Temperatures vary widely in the literature and should only be used as estimates. Factors which may cause variation include partial pressure of oxygen, altitude, humidity, and amount of time required for ignition. Triethylborane convert 20 C F abbr on Silane convert 21 ... Thick Materials . Fire DEFAULTSORT AutoignitionTemperature Category Chemical properties Category ... more details
pp move indef About the thermodynamic property Temperature disambiguation Image MonthlyMeanT.gif thumb .... Temperature is a physical property of matter that quantitatively expresses the common notions of heat hot and cold . Objects of low temperature are cold, while various degrees of higher temperatures ... temperature to bodies of lower temperature. No net heat will be exchanged between bodies of the same temperature such bodies are said to be in thermal equilibrium . The temperature of a substance ... in temperature upon receiving external kinetic energy as heat is also inversely proportional to heat capacity . Temperature can be thought of as the concentration of kinetic energy relative to its ... a cold object. Quantitatively, temperature is measured with thermometers , which may be calibration calibrated to a variety of Temperature conversion formulas temperature scales . Image Thermally Agitated ... of the vibrations increases with temperature. Temperature plays an important role in all fields ... in science File Annual Average Temperature Map.jpg thumb 400px Annual mean temperature around the world ... depend on the temperature. Temperature also plays an important role in determining the rate and extent ... mechanisms for maintaining the temperature at 310 K, since temperatures only a few degrees higher can result in harmful reactions with serious consequences. Temperature also determines the thermal ... a tungsten filament is electricity electrically heated to a temperature at which significant quantities of visible light are emitted. Temperature scales see also Scale of temperature Some of the world uses the Celsius scale C for most temperature measurements. It has the same incremental scaling ... point of water. ref group note Historically, the Celsius scale was a purely empirical temperature ... at 212 F. For practical purposes of scientific temperature measurement, the International System of Units SI defines a scale and unit for the thermodynamic temperature by using the easily reproducible ... more details
Temperature range may refer to Atmospheric temperature An aspect of Climate Climate classification climate classification Diurnal temperature variation Operating temperatureTemperature Thermoregulation Disambiguation ... more details
wiktionarypar temperatureTemperature is a physical property of a system that underlies the common notions of hot and cold. Closely related are Thermodynamic temperature Color temperature Effective temperature Normal human body temperature The term may also refer to Noise temperature , a measure of the noise of an electronic component. Temperature meat , or doneness, a description of how thoroughly cooked a cut of meat is Temperature song Temperature song , a song by Sean Paul Temperature Zion I song Temperature Zion I song Temperature , a song by Blaque from Blaque Out Temperature , a song by Little Walter Albums Little Walter See also Lookfrom Temperature disambig ca Temperatura desambiguaci de Temperatur Begriffskl rung la Temperatura discretiva lt Temperat ra reik m s pl Temperatura ujednoznacznienie ... more details
wiktionarypar melting temperature Melting temperature may refer to Melting point , the temperature at which a substance changes from solid to liquid state. DNA melting temperature , the temperature at which a DNA double helix dissociates into single strands. disambig ... more details
Unreferenced date February 2008 Transition temperature is the temperature at which a material changes from one crystal state Allotropy allotrope to another. There are seven crystal system s and every crystallized material exists in one of them. In the case of ferroelectric or ferromagnetic crystals a transition temperature may be known as the Curie temperature . Transition temperature is the temperature at which a solid changes State of matter state , either becoming softer when Heat heated or more brittle when cooled. Transition temperature is the temperature above and below which solubility changes in a noticeably different way. On a graph the transition temperature is deduced by the intersection of two lines each of which have a different gradient. Category Crystallography Chemistry stub ... more details
Refimprove date April 2009 Orphan date February 2009 The permissive temperature is the temperature at which a temperature sensitive mutant gene product takes on a normal, functional phenotype. ref http www.biology online.org dictionary Permissive temperature ref When a temperature sensitive mutant is grown in a permissive condition, the mutant mutated gene product behaves normally meaning that the phenotype isn t observed , even if there is a mutant allele present. This results in the survival of the cell or organism, as if it were a wild type strain. In contrast, the nonpermissive temperature or restrictive temperature is the temperature at which the mutant phenotype is observed. Most temperature sensitive mutations affect proteins, and are recessive and cause loss of protein function at the non permissive temperature. The permissive temperature is one at which the protein typically can fold properly, or remain properly folded. References Reflist Category Temperature Category Cell biology Category Biology terminology biochemistry stub ... more details
Temperature Rising may refer to Temperature Rising album Temperature Rising , a studio album by Thai singer Tata Young Temperatures Rising , an American television situation comedy Temperature s Rising , an album by rock group Loverboy Temperature s Rising Mobb Deep song Temperature s Rising a single by Mobb Deep off of the 1995 album The Infamous disambig ... more details
Temperature cycling or temperature cycle is the process of cycling through two temperature extremes, typically at relatively high rates of change. It is an environmental Stress testing stress test used in evaluating product Reliability engineering reliability as well as in manufacturing to catch early term, latent defects by inducing failure through thermal Fatigue material fatigue . External links http www.motorola.com testservices temperature1.html Temperature Testing Motorola http www.jedec.org download search 22a104d.pdf Temperature Cycling JEDEC Standard No. 22 A104D http www.siliconfareast.com TCT.htm Temperature Cycle Test SiliconFarEast.com http www.siliconfareast.com faq tc life.htm Equivalent Life of Temperature Cycle Testing SiliconFarEast.com Category Reliability engineering ... more details
Apparent temperature is the general term for the perceived outdoor temperature, caused by the combined effects of air temperature , relative humidity and wind speed , this term was coined by Conor. The Heat index measures the effect of humidity on the perception of temperature. In humid conditions, the air feels hotter than it actually is, because of the reduction in evaporation of perspiration . The Wind chill measures the effect of wind speed on the perception of temperature. In windy conditions, the air feels cooler than it actually is, because of the increase in evaporation of perspiration. The Wet Bulb Globe Temperature WBGT combines the effects of radiation, humidity, temperature and wind speed on the perception of temperature. It is not often used as the resulting figure is very location specific eg cloud cover and or wind shielding . Category Temperature ... more details
Junction temperature is the highest temperature of the actual semiconductor in an electronic device. In operation it is higher than case temperature and the temperature of the part s exterior. The difference is equal to the amount of heat transferred from the junction to case multiplied by the junction to case thermal resistance . Maximum junction temperature is specified in a part s datasheet and is used when calculating the necessary case to ambient thermal resistance for a given power dissipation. This in turn is used to select an appropriate heat sink if necessary. An estimation of the chip junction temperature, T sub J sub , can be obtained from the following equation T sub J sub T sub A sub R sub JA sub P sub D sub where T sub A sub ambient temperature for the package C R sub JA sub junction to ambient thermal resistance C W P sub D sub power dissipation in package W DEFAULTSORT Junction temperature Category Semiconductors engineering stub zh ... more details
Comparison US standard atmosphere 1962.svg Atmospheric temperature is a measure of temperature at different levels of the Earth s atmosphere . It is governed by many factors, including insolation incoming solar radiation , humidity and altitude . When discussing surface temperature , the annual atmospheric temperature range at any geographical location depends largely upon the type of biome , as measured by the K ppen climate classification . Temperature versus height File EarthAtmosphereBig.jpg thumb 50px right main lapse rate In the Earth s atmosphere, temperature varies greatly at different heights relative to the Earth s surface. The coldest temperatures lie near the mesopause , an area approximately convert 85 km mi abbr on to convert 100 km mi abbr on above the surface. In contrast, some of the warmest temperatures can be found in the thermosphere , which receives strong ionizing radiation at the level of the Van Allen radiation belt . Temperature varies as one moves vertically upwards from the Earth s Surface. Global temperature seealso Schumann resonances Global temperature The concept of a global temperature is commonly used in climatology , and denotes the average temperature of the Earth based on surface ref cite web last Hansen first James E. title GISS Surface Temperature Analysis GISTEMP url http data.giss.nasa.gov gistemp work National Aeronautic and Space Administration publisher Goddard Institute for Space Studies accessdate 1 September 2011 authorlink James Hansen ref , near surface or troposphere tropospheric measurements. These temperature record s and measurements are typically acquired using the satellite temperature record satellite or instrumental temperature record ground instrumental temperature thermometer measurements , then usually compiled using ... proxy climate proxy data . See also Atmospheric thermodynamics Brightness temperature Emissivity Emissivity ... Category Atmospheric thermodynamics Category Climate Category Thermodynamics Category Temperature ... more details
38.7.JPG thumb right A medical clinical thermometer showing the temperature of 38.7 C Attempts of standardized temperature measurement have been reported as early as 170 AD by Galen Claudius Galenus . ref name quinn cite book author T. J. Quinn year 1983 title Temperature publisher Academic Press ... in the 17th century. Early devices to measure temperature were called thermoscope s. The first ... The development of today s thermometer s and temperature scales began in the early 18th century, when ... and the Kelvin scale. Technologies Many methods have been developed for measuring temperature. Most of these rely on measuring some physical property of a working material that varies with temperature. One of the most common devices for measuring temperature is the mercury in glass thermometer glass ..., which acts as the working fluid. Temperature increase causes the fluid to expand, so the temperature ... so that one can read the temperature simply by observing the level of the fluid in the thermometer ... standpoint, is the gas thermometer . Other important devices for measuring temperature include Thermocouple s Thermistor s Resistance Temperature Detector RTD Pyrometer Langmuir probe s for electron temperature of a Plasma physics plasma Infrared Other thermometer s One must be careful when measuring temperature to ensure that the measuring instrument thermometer, thermocouple, etc. is really the same temperature as the material that is being measured. Under some conditions heat from the measuring instrument can cause a temperature gradient, so the measured temperature is different from the actual temperature of the system. In such a case the measured temperature will vary not only with the temperature of the system, but also with the heat transfer properties of the system. An extreme ... windy conditions than calm conditions even though the temperature is the same. What is happening is that the wind ... temperature for the same ambient temperature. The theoretical basis for thermometers is the zeroth ... more details
The vibrational temperature is commonly used in thermodynamics , to simplify certain equations. It has units of temperature and is defined as math theta vib frac hc nu k B math br where math k B math is Boltzmann s constant The vibrational temperature is used commonly when finding the vibrational partition function . References http www.chem.arizona.edu salzmanr 480b statt02 statt02.html Statistical thermodynamics University Arizona See also Rotational temperature Rotational spectroscopy Vibrational spectroscopy Infrared spectroscopy Spectroscopy Category Atomic physics Category Molecular physics ... more details
Unreferenced date November 2006 The Excitation Temperature math T ex math often called the spin temperature for the 21 cm line is defined for a population of particles via the Boltzmann factor . It satisfies math frac n u n l frac g u g l exp frac Delta E k T ex , math where n sub u sub and n sub l sub represent the number of particles in an upper e.g. excited and lower e.g. ground state, and g sub u sub and g sub l sub their statistical weights respectively. Thus the excitation temperature is the temperature at which we would expect to find a system with this ratio of level populations. However it has no actual physical meaning except when in local thermodynamical equilibrium. The excitation temperature can even be negative for a system with inverted levels such as a maser . DEFAULTSORT Excitation Temperature Category Temperature Category Physics ... more details
In heat transfer and fluid dynamics , the film temperature math T f math is an approximation to the temperature of a fluid inside a convection boundary layer . It is calculated as the arithmetic mean of the temperature at the surface of the solid boundary wall math T w math and the free stream temperature math T infty math ref Incropera & DeWitt Fundamentals of Heat and Mass Transfer , 4th Ed ref math T f frac T w T infty 2 math The film temperature is often used as the temperature at which fluid properties are calculated when using Prandtl number , Nusselt number , Reynolds number or Grashof number to calculate a heat transfer coefficient , because it a reasonable first approximation to the temperature within the convection boundary layer. Somewhat confusing terminology may be encountered in relation to boilers and heat exchangers, where the same term is used to refer to the limit hot temperature of a fluid in contact with a hot surface. ref http www.paratherm.com tipsheets tipsheet fluid life film temperature.asp Film Temperature ref ref http www.multitherm.com technical articles bulk film temp impact.html Bulk and Film Temperatures ref References references Category Fluid dynamics Category Heat transfer it Temperatura di film pt Temperatura de pel cula ... more details
In fluid dynamics , the bulk temperature , or the average fluid bulk temperature , is a convenient reference point for evaluating properties related to convective heat transfer , particularly in applications related to flow in pipe material pipes and duct HVAC ducts . The concept of the bulk temperature is that adiabatic mixing of the fluid from a given cross section of the duct will result in some equilibrium temperature that accurately reflects the average temperature of the moving fluid, more so than a simple average like the film temperature . ref Kreith, Frank, and Bohn, Mark S. Principles of Heat Transfer, Sixth Edition. Brooks Cole Pacific Grove, CA, 2001. ref References references Category Fluid dynamics Category Thermodynamics Category Heat transfer fluiddynamics stub ... more details
Other uses Degree disambiguation The term degree is used in several scale measurement scales of temperature . The symbol is usually used, followed by the initial letter of the unit, for example C for degree s Celsius. A degree can be defined as a set change in temperature measured against a given scale, for example, one degree celsius is one hundredth of the temperature change between water melting and water boiling. Scales of temperature measured in degrees Common scales of temperature measured in degrees Celsius C Kelvin K , which uses the Celsius scale, adjusted so that 0 kelvins is equal to absolute zero . Fahrenheit F Rankine scale Rankine R or Ra , which uses the Fahrenheit scale, adjusted so that 0 degrees Rankine is equal to absolute zero . Other scales of temperature Delisle scale Delisle De Newton scale Newton N R aumur scale R aumur R R mer scale R mer R Kelvin main Kelvin The degree Kelvin K is a former name for the SI unit of temperature on the thermodynamic temperature thermodynamic absolute temperature scale . Since 1967 it has been known simply as the kelvin , with symbol K. Degree absolute A is obsolete terminology, often referring specifically to the kelvin but sometimes the degree Rankine as well. ref cite web url http www.bipm.org en si si brochure chapter2 2 1 kelvin.html title Unit of thermodynamic temperature kelvin International System of Units SI brochure, Section 2.1.1.5 publisher International Bureau of Weights and Measures accessdate 2009 02 10 ref ... body temperature 37.0 C 98.6 F Room temperature the 20 25 C 68 77 F source ref cite web url http lamar.colostate.edu hillger temps.htm title Metric system temperature kelvin and degree Celsius publisher Colorado State University Lamar accessdate 2009 02 10 ref Temperature conversions Timeline Temperature Conversion See also Comparison of temperature scales Degree sign International System of Units References references Category Units of temperature measurement stub physics stub de Grad Temperatur ... more details
For temperature control in organisms Thermoregulation Unreferenced date August 2009 Temperature control is a process in which change of temperature of a space and objects collectively therewithin is measured or otherwise detected, and the passage of heat energy into or out of the space is adjusted to achieve a desired average temperature. Control loops A home thermostat is an example of a closed control loop It constantly assesses the current room temperature and controls a heater and or air conditioner to increase or decrease the temperature according to user defined setting s . A simple low cost, cheap thermostat merely switches the heater or air conditioner either on or off, and temporary overshoot and undershoot of the desired average temperature must be expected. A more expensive thermostat varies the amount of heat or cooling provided by the heater or cooler, depending on the difference between the required temperature the setpoint and the actual temperature. This minimizes over undershoot. The process is called PID and is implemented using a PID controller PID Controller . Energy balance An object s or space s temperature increases when heat energy moves into it, increasing the average kinetic energy of its atoms, e.g., of things and air in a room. Heat energy leaving an object or space lowers its temperature. Heat flows from one place to another always from a higher temperature to a lower one by one or more of three processes heat conduction conduction , convection and radiation . In conduction, energy is passed from one atom to another by direct contact. In convection ... or thing, more energy is received than is lost, its temperature increases. If the amount of energy coming in and going out are exactly the same, the temperature stays constant there is thermal ... System Thermodynamic equilibrium External links http www.hbtem.com Global Temperature Controller DEFAULTSORT Temperature Control Category Temperature control ... more details
The temperature coefficient is the relative change of a physical property when the temperature is changed by 1 Kelvin K . In the following formula, let R be the physical property to be measured and T be the temperature at which the property is measured. T sub 0 sub is the reference temperature, and T is the difference between T and T sub 0 sub . Finally, is the linear temperature coefficient ... Delta T math Here has the dimension s of an inverse temperature 1 K or K sup 1 sup . This equation is linear with respect to temperature. For quantities that vary polynomial ly or logarithm ically with temperature, it may be possible to calculate a temperature coefficient that is a useful approximation ... with temperature, such as Arrhenius equation the rate of a chemical reaction , any temperature coefficient would be valid only over a very small temperature range. Different temperature coefficients are specified for various applications, including nuclear, electrical and magnetic. Negative temperature coefficient A negative temperature coefficient NTC occurs when the thermal conductivity of a material rises with increasing temperature, typically in a defined temperature range. For most materials, the thermal conductivity will decrease with increasing temperature. Materials with a negative temperature coefficient have been used in floor heating since 1971. The negative temperature coefficient ... frac B T math where R is resistance, A and B are constants, and T is absolute temperature K . The constant ... sensitivity to temperature. Such is the importance of the B constant value, that it is possible to characterize ... T 0 e frac B T math where math R 0 math is resistance at temperature math T 0 math . Therefore, many ... for the electrical conduction from these defect centers. Reversible temperature coefficient Residual magnetic flux density or Magnetic field B and H Br changes with temperature and it is one of the important ... wave tube s TWTs , need to have constant field over a wide temperature range . The reversible ... more details
The Krafft temperature also known as Krafft point , or critical micelle temperature is the minimum temperature at which surfactant s form micelle s. Below the Krafft temperature, there is no value for the critical micelle concentration CMC , i.e., micelles cannot form. The Krafft temperature is a point of phase change below which the surfactant remains in crystalline form, even in aqueous solution. Surfactants in such a crystalline state will only solubilize and form micelles if another surfactant assists it in overcoming the forces that keep it crystallized, or if the temperature increases, thus causing entropy to have a stronger force and encouraging the crystalline structure to break apart. The Krafft point is named after German chemist Friedrich Krafft . Structural Effects Surfactants are usually composed of a hydrocarbon chain and a polar head group. Increasing the length of the hydrocarbon chain increases the Krafft temperature because it improves Van der Waals force Van der Waals forces. External links http goldbook.iupac.org K03415.html IUPAC Gold book Krafft temperature chem stub Category Colloidal chemistry Category Physical chemistry de Krafft Punkt it Temperatura di Krafft nl Krafft temperatuur ja ... more details
Unreferenced stub auto yes date December 2009 If the velocity velocities of a group of electron s, e.g., in a plasma physics plasma , follow a Maxwell Boltzmann distribution Distribution of the velocity vector Maxwell Boltzmann distribution , then the electron temperature is well defined as the temperature of that distribution. For other distributions, two thirds of the average energy is often referred to as the temperature, since for a Maxwell Boltzmann distribution with three Degrees of freedom physics and chemistry degrees of freedom , math langle E rangle 3 2 langle k BT rangle math . The International System of Units SI unit of temperature is the kelvin K , but using the above relation the electron temperature is often expressed in terms of the energy unit electronvolt eV . Each kelvin 1 K corresponds to 8.617343 15 10 sup 5 sup eV this factor is the ratio of the Boltzmann constant to the elementary charge . The electron temperature of a plasma can be several orders of magnitude higher than the temperature of the neutral species or of the ion s. This is a result of two facts. Firstly, many plasma source s heat the electrons more strongly than the ions. Secondly, atoms and ions are much heavier than electrons, and energy transfer in a two body collision is much more efficient if the masses are similar. DEFAULTSORT Electron Temperature Categories Category Plasma physics Physics stub sv Elektrontemperatur ... more details
Annealing temperature may refer to Annealing glass Annealing metallurgy Polymerase chain reaction dab Long comment to avoid being listed on short pages ... more details
Refimprove date December 2009 Operative temperature math t o math is defined as a uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual nonuniform environment. ref ASHRAE Terminology, ASHRAE Handbook CD, 1999 2002 ref Some references also use the terms equivalent temperature or effective temperature to describe combined effects of convective and radiant heat transfer. ref Nilsson, H.O., Comfort Climate Evaluation with Thermal Manikin Methods and Computer Simulation Models, National Institute for Working Life, 2004, pg. 37 ref In design, operative temperature can be defined as the average of the Mean radiant temperature mean radiant and Dry bulb temperature ambient air temperatures , weighted by their respective heat transfer coefficient s. ref Thermal Comfort, ASHRAE Handbook, Fundamentals, Ch. 9, pg.3, 2009 ref The instrument used for assessing environmental thermal comfort in terms of operative temperature is called a eupatheoscope and was invented by A. F. Dufton in 1929. ref Glossary of Meteorology, American Meteorological Society, http amsglossary.allenpress.com glossary browse?s e&p 42 , accessed Sept 2010 ref Mathematically, operative temperature can be shown as big math t o frac h r t mr h c t a h r h c math big where, math h c math convective heat transfer coefficient math h r math linear radiative heat transfer coefficient math t a math air temperature math t mr math mean radiant temperature Application Operative temperature is used in heat transfer and thermal comfort analysis in transportation and buildings. ref Dufton, A. F. The Equivalent Temperature of a room ... psychrometric charts used in HVAC design only show the dry bulb temperature on the x axis abscissa , however, it is the operative temperature which is specified on the x axis of the psychrometric chart ... also HVAC Psychrometrics Underfloor heating ASHRAE References Reflist DEFAULTSORT Operative Temperature ... more details
About radiometric dating blocking temperature in a ferromagnet Superparamagnetism In radiometric dating , closure temperature or blocking temperature refers to the temperature of a system, such as a mineral , at the time given by its radiometric date. In physical terms, the closure temperature at which a system has cooled so that there is no longer any exchange of parent or daughter isotopes with the external environment. This temperature varies broadly between different minerals and also differs depending on the parent and daughter atoms being considered. ref Earth a Portrait of a Planet http www.wwnorton.com college geo earth2 glossary b.htm Glossary W.W. Norton & Company ref It is specific to a particular material and isotopic system. ref name Rollinson Rollinson, 1993. Using Geochemical Data Evaluation, Presentation, Interpretation Longman Scientific & Technical. ISBN 978 0 582 06701 1 ref These temperatures are experimentally determined in the lab by Petrology Branches artificially resetting sample mineral s using a high temperature furnace. As the mineral cools, the crystal structure begins to form and diffusion of isotope s is less easy. At a certain temperature, the crystal structure has formed sufficiently to prevent diffusion of isotopes. This temperature is what is known as blocking temperature and represents the temperature below which the mineral is a closed system to isotopes. ref name Rollinson Thus an igneous or metamorphic rock or melt, which is slowly cooling, does not begin to exhibit measurable radioactive decay until it cools below the blocking temperature ... cooled to blocking temperature. These temperatures can also be determined in the field by comparing ... values of the closure temperature require more precise calculations and characterizations of the diffusion ... 1 Mineral Closure temperature C Hornblende 530 40 Muscovite 350 Biotite 280 40 Uranium lead method class wikitable border 1 Mineral Closure temperature C ref cite journal doi 10.1130 G21010.1 title ... more details
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