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Temperature—contact
Published in Martin Novák, Introduction to Sensors for Electrical and Mechanical Engineers, 2020
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.
The Laws of Thermodynamics
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
Each of these regions has a well-defined boundary for a given temperature and pressure. A pressure–temperature diagram for a pure substance is shown in Figure 6.20, and pressure–temperature diagrams for water and carbon dioxide are shown in Figure 6.21. Most materials have phase diagrams that look similar to this. Every phase diagram also has a line of demarcation between the liquid and vapor phases that is called a vaporization line. This line is the line of demarcation between a liquid and a gas. In addition, all phase diagrams also have a triple point. A triple point is a P–T combination where all three of the phases (solid, liquid, and vapor) coexist in thermodynamic equilibrium at the same time. For example, the triple point of water is reached at a temperature of 0.01°C (273.16°K) and a pressure of 611.73 Pa, 6.1173 mbar, 0.0883 PSI, or 0.0060373 atm. The triple point for other materials can occur at different pressures and temperatures. Finally, the vaporization line will eventually end at what is known as the critical point. Here, the liquid phase and vapor phases can no longer be distinguished from one another. At pressures above the critical point, the liquid can no longer convert itself into a vapor. Instead, the liquid will convert itself into a very dense fluid.
Supercritical Fluid Chromatography Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Thomas L. Chester, J. David Pinkston
The three common states of matter—solid, liquid, and vapor (or gas)—are well known to beginning students. The areas where these phases exist in a two-dimensional pressure–temperature representation for a pure material are depicted in Figure 24.2a. All three phases coexist at just one combination of temperature and pressure, the triple point. Liquid (l) and vapor (v) phases can coexist at various combinations of temperature (T) and pressure (P) falling on a line defining the l–v phase boundary, that is, the boiling line.
The Development of Shattered Pellet Injector on HL-2A
Published in Fusion Science and Technology, 2019
H. B. Xu, L. Nie, G. L. Zhu, C. Y. Chen, W. Pan, D. Q. Liu, Z. Cao, M. Xu
The gas vacuum system consists of two independent subsystems, as shown in Fig. 4. The first subsystem consists of lines of helium input to the fast valve (0 to 6 MPa) and to the vacuum pumping system. The second subsystem is a line of fuel gas feeding to the gun. Fuel gas at constant pressure will be admitted inside both sides of the barrel. The fuel gas pressure is below the triple point, causing the gas to freeze directly from vapor phase to solid phase on the internal barrel wall. The barrel is connected to both a propellant and a fuel valve. Parker’s pulse valve was used as the fast valve. This valve is a high-pressure, solenoid-driven valve capable of opening in less than 1 ms. Parker’s Iota One valve driver is also used as the control unit. Pulse duration ranges in microseconds. Milliseconds or longer can be selected.
Application of a non-cubic equation of state to predict the solid-liquid-vapor phase coexistences of pure alkanes
Published in Chemical Engineering Communications, 2022
José Manuel Marín-García, Ascención Romero-Martínez, Felipe de Jesús Guevara-Rodríguez
On the other hand, using the last definition is also possible to calculate substance fugacity, which is defined as In this work, substance fugacity is used to determine the solid-liquid, solid-vapor, and liquid-vapor coexistences with the following considerations (see Figure 1):If temperature is above the critical temperature, only the solid-liquid coexistence exists. In this case, fugacity of solid phase is equal to fugacity of liquid phase, i.e. and is the common value of the pressure at each phase.If temperature is below the liquid-vapor critical temperature but above the triple point temperature, two different coexistence states appear: solid-liquid1 (with and ) and liquid2-vapor (with and ). Liquid1 phase is different to liquid2 phase because and However, at the triple point temperature, and are fulfilled.If temperature is below the triple point temperature, only the solid-vapor coexistence exists. Therefore, and (where Pt is the common value of pressure at the triple point).
A meticulous overview on drying-based (spray-, freeze-, and spray-freeze) particle engineering approaches for pharmaceutical technologies
Published in Drying Technology, 2021
Sagar Pardeshi, Mahesh More, Pritam Patil, Chandrakantsing Pardeshi, Prashant Deshmukh, Arun Mujumdar, Jitendra Naik
Nowadays for better stability and easy handling purposes, freeze-drying is widely used in pharmaceutical industries. In addition, the utmost quality of a dried product can be obtained in freeze-drying, also known as lyophilization. The freeze-drying process comprises three steps freezing, primary, and secondary drying. Freezing is a competent desiccation step, where an aqueous solution is frozen to a solid-state. The freezing process is associated with cooling, carried out by spraying into a flow of chilly gas, immersing in liquid nitrogen, or placing on a cold plate as depicted in Figure 1b.[15] If the rate of cooling is not prohibited correctly, freezing may cause undesirable changes in the product and sublimation rate.[20] In general, the glass transition temperature of the drug solution must be greater than the ending temperature of pre-freezing. Freezing rate whether it is slow or fast influences the sublimation, slow freezing would shorten the sublimation period as the massive pores developed from the sublimation of big ice crystals, while recombination and aggregation of the particle are eluded by the fast-freezing rate (desirable).[21] The second step is primary drying or ice sublimation performed at low temperature and vacuum, where frozen solvent mostly ice is sublimated. During primary drying, sublimation can be accomplished by chamber pressure reducing to a value below the triple point. The annealing step may introduce before the primary stage in some operations for the unfrozen water which can diffuse through the frozen matrix and crystal ice will grow in size.[21,22] The optimization of primary drying is very important for the process economics of freeze-drying. The ending stage of freeze-drying is secondary drying, which desorbs the water/solvent from the frozen concentrate at a temperature higher than the freezing point of the solvent and lower than the glass transition temperature of the medium. In addition, the vacuum level can be less than the primary drying. Ten to thirty percent of water content is removed from the material by desorption during the secondary drying stage.[20,21]