Absolute Temperature
Absolute temperature refers to a temperature scale that starts at absolute zero, the lowest possible temperature where molecular motion ceases. The most commonly used absolute temperature scale is the Kelvin scale, where 0 K represents absolute zero. Absolute temperature is important in engineering and technology for calculations involving gas laws, thermodynamics, and heat transfer.
6 Key excerpts on "Absolute Temperature"
eBook - ePub- Kaveh Azar(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...However, if there is one general principle that can be very highly recommended, it is simplicity. It is usually advantageous to choose boundary conditions (sample shape, heater placement) so as to keep the heat flow simple, preferably one-dimensional. It is also wise, especially for novices, to avoid techniques that rely on a complicated mathematical model of the experimental situation. It is usually preferable to simplify the experimental arrangement rather than to try to build a more complicated (and probably inaccurate) model. The difficulty of making accurate thermal measurements is not widely appreciated. This difficulty arises from problems in thermometry and in the control of heat flow, e.g., avoiding heat loss by radiation or convection. However, with the observation of certain precautions which can be rather demanding, it is possible to obtain accurate data over a wide temperature range for a large variety of materials. 7.7 Definitions Absolute Temperature Temperature measured on the Kelvin scale, for which (absolute) zero occurs at approximately −273°C. The size of the degree is the same on the Kelvin and Centigrade scales (1 K = 1°C), so that room temperature is approximately 300 K. Anisotropy The dependence of a vector or tensor property on direction in space. For example, the thermal conductivity in some materials depends on the direction in which the heat is flowing. Convection The movement of fluid (gas or liquid) caused by fans or pumps, or by gravitational instabilities caused, for example, by heating from below. Emissivity ε A numerical constant proportional to the amount of thermal radiation given off by a specified material at a specified temperature...
- Martin Novák(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...3 Temperature—contact Temperature is one of the most important properties. It influences virtually all other properties. Temperature is an integral property. It is a measure of average kinetic energy of the molecules. There are different temperature scales. Absolute Temperature is expressed in kelvin (K). By definition, the temperature at absolute zero is 0 K. The second point defining the thermodynamic scale is the triple point of water (0.01°C). In thermodynamics, the triple point of a substance is the temperature and pressure at which three phases (for example, gas, liquid and solid) of that substance coexist in thermodynamic equilibrium. Other used temperature scales are Celsius, Fahrenheit and Rankine. The Celsius scale uses the freezing point (0°C) and boiling point (100°C) of water as definition points. The formulas to recalculate between different selected scales are shown in table 3.1. TABLE 3.1: Conversion between selected temperature units - K ° C F K - [K] = [ ° C] + 273.15 [K] = ([ ° F] + 459.67) · (5/9) ° C [ ° C] = [K] − 273.15 - [ ° C] = ([ ° F] − 32)/1.8 F [ ° F] = (9/5)x[K] − 459.67 [ ° F] = 1.8[ ° C] + 32 - Defining points for temperature are nowadays defined by the International Temperature Scale (ITS-90) [ 7 ]. 3.1 Resistive temperature detectors (RTD) Resistive temperature detectors are based on changes of electrical resistance on temperature. They are among the most common industrial temperature sensors due to their accuracy, robustness and reliability. The dependence of electrical resistance on temperature for some materials in a small temperature range can be considered linear. As small range ±100°C is usually considered...
eBook - ePub- Colin Salter(Author)
- 2021(Publication Date)
- Pavilion(Publisher)
...Instead of measuring existing extremes of temperature therefore, he approached it with the theoretical logic of a scientist – three scientists in fact. He corresponded with James Joule about the mechanical equivalent of heat, and with Henri Victor Regnault on the thermal properties of gases; and he studied Nicolas Carnot’s theory of motive power from heat. Thomson observed that for a given volume of any gas, the relationship between temperature and pressure remains constant. Plotting one against the other on a graph produced a straight line. He proposed that when the pressure reached zero, it would be because there was no heat to generate energy, and therefore the temperature at that point on the graph would be absolute zero. He thus determined a value for absolute zero of -273˚C. With the benefit of greater experimental accuracy we now know that 0˚K, the absolute zero of the Kelvin scale, is -273.15˚C, or -459.68˚F. The Kelvin Scale advances in degrees Celsius. Another scale, which also starts at absolute zero but advances in degrees Fahrenheit, is called the Rankine scale, after another Glasgow University physicist, Macquorn Rankine. Setting a value for absolute zero spurred the experimental scientific community on to try to reach it. The average temperature of the universe is 2.73˚K, or -270.42˚C (-454.756˚F), but a temperature of approximately 1˚K was observed in the Boomerang Nebula; and scientists have artificially reached 0.0000000001˚K by slowing the nuclear activity within a sample of the element rhodium. It is currently accepted that engineering a temperature of absolute zero is impossible. Oymyakon in Siberia is the coldest permanently inhabited place on Earth and is found in the Arctic Circle’s Northern Pole of Cold. In 1933, it recorded its lowest temperature of -67.7°C. Quite warm on the Kelvin Scale. William Thomson became a professor at Glasgow University at the age of 22....
eBook - ePub- G. M. S. de Silva(Author)
- 2012(Publication Date)
- Routledge(Publisher)
...7 Measurement of temperature 7.1 Introduction Temperature is one of the most important measurement parameters from an industrial point of view. Large numbers of temperature measuring instruments such as mercury-in-glass thermometers, dial thermometers, thermocouple sensors, resistance temperature devices (RTDs) and temperature transmitters are used in most industrial systems. It is also an important parameter in health services, for monitoring of the environment and safety systems. 7.2 SI units The SI base unit for temperature is the kelvin, defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The degree Celsius is also recognized in the SI system and is defined by the relation: (7.1) where t is a temperature in degrees Celsius and T is the equivalent kelvin temperature. 7.3 Thermodynamic scale Temperature is the degree of hotness of an object and is governed by the laws of thermodynamics. The temperature scale based on the first and second laws of thermodynamics is known as the thermodynamic temperature scale. The lowest limit of the thermodynamic scale is absolute zero or 0 kelvin (K). Since the scale is linear by definition only one other non-zero reference point is needed to establish its slope. This reference point was originally defined as the freezing point of water (0°C or 273.15 K). In 1960 the reference point was changed to a more precisely reproducible point, namely the triple point of water (0.01 °C). However, measurement of temperature on the thermodynamic scale is hardly suitable for practical thermometry. In practice there are three main reasons: (a) It is difficult to measure thermodynamic temperatures...
eBook - ePubUnderstanding Fever and Body Temperature
A Cross-disciplinary Approach to Clinical Practice
- Ewa Grodzinsky, Märta Sund Levander, Ewa Grodzinsky, Märta Sund Levander(Authors)
- 2019(Publication Date)
- Palgrave Macmillan(Publisher)
...© The Author(s) 2020 E. Grodzinsky, M. Sund Levander (eds.) Understanding Fever and Body Temperature https://doi.org/10.1007/978-3-030-21886-7_4 Begin Abstract 4. Technical Accuracy Ewa Grodzinsky 1 and Märta Sund Levander 2 (1) Department of Pharmaceutic Research, Linköping University, Linköping, Sweden (2) Department of Nursing, Linköping University, Linköping, Sweden Ewa Grodzinsky (Corresponding author) Märta Sund Levander Email: [email protected] End Abstract Calibration Temperature is a measure of the hotness or coldness of an object, where hot has a higher ‘temperature’ than cold. Several units of temperature have been suggested over the centuries, and today the most common are the Celsius, Fahrenheit, and Kelvin scales. The two formers are common units of temperature used by the public, and the latter is the SI unit of thermodynamic temperature (SI from the Système International d’unités, or international system of units). One Kelvin is defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water—the unique temperature at which the three phases of water are in equilibrium. This fixed point is the basis for the International Temperature Scale (ITS) [ 1 ]. The measurement of temperature is a well-established field of metrology (measurement science), which broadly divides into two practical methods of implementation: contact and non-contact thermometry [ 2 ]. Non-contact thermometry, unlike contact thermometry, is a modern technique that has developed significantly over the last 50 years (see Chap. 3). Improved understanding of the theoretical aspects of the technique, along with improved technology, has increased its practical application...
eBook - ePubMeasurement and Instrumentation in Engineering
Principles and Basic Laboratory Experiments
- Francis S. Tse, Ivan E. Morse(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
...9 Temperature Measurements 9-1. INTRODUCTION The objective of this chapter is to give an overview of modern industrial temperature sensors. The emphasis is on thermocouples and resistance devices, since they are used for more than 80% of temperature measurements in industry [ 1 ]. Pyrometers and integrated circuits are gaining popularity. Some sensors for temperature monitoring are mentioned for completeness. Temperature is measured by its effect. Any object that has a property influenced by temperature is potentially a thermometer. The effect may be a change in (1) the physical/chemical states of an object, (2) dimensions, (3) electrical properties, (4) radiation properties, and (5) others [ 2 ]. The topics in the chapter are also grouped by the type of changes. The temperature of an object can also be related to the mean kinetic energy of its molecules, but the kinetic energies are not measurable at present. The thermodynamic temperature scale based on the Carnot cycle is independent of material properties, but it is not practical and gives only the ratio of temperatures. The temperature scale based on ideal gas law is identical to the thermodynamic scale [ 3 ], but its implementation is not practical except in a standards laboratory [ 4 ]. The four fundamental units in measurement are mass, length, time, and temperature. The first three are extensive quantities. For example, the addition of two bodies of equal mass gives twice the mass. Temperature is an intensive quantity. When two bodies of the same temperature are brought together, they are in thermal equilibrium, and no change in temperature is observed. This is the basis for using fixed points in the International Practical Temperature Scale (IPTS) for calibration. Instrumentation and temperature measurement practices are covered by many standards [ 5 ]...
