Gases thermal expansion

Figure 10.5 Van Der Waals.m file for retrieving critical properties of a substance and estimating the molar volume of both the gas, GasVol, and liquid, LiqVol, the compressibility factor, Zval, the gas thermal expansion coefficient, alpha (a), and the gas isothermal compressibility, kappa (k), for a selected substance at the given absolute pressure, P, and temperature, T.

The Gas Thermal Expansion Coefficient=0.0033906 The Gas Isothermal Compressibility Factor .008... 

The electronic configuration for an element s ground state (Table 4.1) is a shorthand representation giving the number of electrons (superscript) found in each of the allowed sublevels (s, p, d, f) above a noble gas core (indicated by brackets). In addition, values for the thermal conductivity, the electrical resistance, and the coefficient of linear thermal expansion are included. 

Moleculady mixed composites of montmorillonite clay and polyimide which have a higher resistance to gas permeation and a lower coefficient of thermal expansion than ordinary polyimides have been produced (60). These polyimide hybrids were synthesized using montmorillonite intercalated with the ammonium salt of dodecylamine. When polymerized in the presence of dimethyl acetamide and polyamic acid, the resulting dispersion was cast onto glass plates and cured. The cured films were as transparent as polyimide. 

Low Expansion Alloys. Binary Fe—Ni alloys as well as several alloys of the type Fe—Ni—X, where X = Cr or Co, are utilized for their low thermal expansion coefficients over a limited temperature range. Other elements also may be added to provide altered mechanical or physical properties. Common trade names include Invar (64%Fe—36%Ni), F.linvar (52%Fe—36%Ni—12%Cr) and super Invar (63%Fe—32%Ni—5%Co). These alloys, which have many commercial appHcations, are typically used at low (25—500°C) temperatures. Exceptions are automotive pistons and components of gas turbines. These alloys are useful to about 650°C while retaining low coefficients of thermal expansion. Alloys 903, 907, and 909, based on 42%Fe—38%Ni—13%Co and having varying amounts of niobium, titanium, and aluminum, are examples of such alloys (2). 

High Temperature. The low coefficient of thermal expansion and high thermal conductivity of sihcon carbide bestow it with excellent thermal shock resistance. Combined with its outstanding corrosion resistance, it is used in heat-transfer components such as recuperator tubes, and furnace components such as thermocouple protection tubes, cmcibles, and burner components. Sihcon carbide is being used for prototype automotive gas turbine engine components such as transition ducts, combustor baffles, and pilot combustor support (145). It is also being used in the fabrication of rotors, vanes, vortex, and combustor. 

The ceramic oxide carrier is bonded to the monolith by both chemical and physical means. The bonding differs for a ceramic monolith and a metallic monolith. Attrition is a physical loss of the carrier from the monolith from the surface shear effects caused by the exhaust gas, a sudden start-up or shutdown causing a thermal shock as a result of different coefficients of thermal expansion at the boundary between the carrier and the monolith, physical vibration of the cataly2ed honeycomb, or abrasion from particulates in the exhaust air (21) (see Fig. 6d). 

No tables of the coefficients of thermal expansion of gases are given in this edition. The coefficient at constant pressure, l/t)(3 0/3T)p for an ideal gas is merely the reciprocal of the absolute temperature. For a real gas or liquid, both it and the coefficient at constant volume, 1/p (3p/3T),, should be calculated either from the equation of state or from tabulated PVT data. 

Thermal-expansion and -contraction loads occur when a piping system is prevented from free thermal expansion or contraction as a result of anchors and restraints or undergoes large, rapid temperature changes or unequal temperature distribution because of an injection of cold liquid striking the wall of a pipe cariying hot gas. 

Turboexpander thermal effieieney (TTE isentropie) is defined as the ratio of aetual work produeed by the fluid, divided by the work produeed from the isentropie expansion proeess. Depending on gas eomposition, expansion ratio, and liquid formation, TTE varies between 80%-90%. These high effieieneies are the result of improvements to the thermodynamie and meehanieal design of turboexpanders sinee the early 1960s and their use in gas proeessing plant applieations. 

In large gas turbines labyrinth seals are used in statie as well as dynamie applieations. The essentially statie funetion oeeurs where the easing parts must remain unjoined to allow for differenees in thermal expansion. At this junetion loeation, the labyrinth minimizes leakage. Dynamie labyrinth applieations for both turbines and eompressors are interstage seals, shroud seals, balanee pistons, and end seals. 

Instruments based on the contact principle can further be divided into two classes mechanical thermometers and electrical thermometers. Mechanical thermometers are based on the thermal expansion of a gas, a liquid, or a solid material. They are simple, robust, and do not normally require power to operate. Electrical resistance thermometers utilize the connection between the electrical resistance and the sensor temperature. Thermocouples are based on the phenomenon, where a temperature-dependent voltage is created in a circuit of two different metals. Semiconductor thermometers have a diode or transistor probe, or a more advanced integrated circuit, where the voltage of the semiconductor junctions is temperature dependent. All electrical meters are easy to incorporate with modern data acquisition systems. A summary of contact thermometer properties is shown in Table 12.3. 

In filled thermometers the thermal expansion of a gas or a liquid is transmitted through a thin capillary tube to a bellows or helix, where the deformation indicates the temperature. The temperature range of filled thermometers is very wide, approximately -200 to +700 °C. They are extremely robust but are not very high in accuracy. The application is mainly for process instrumentation and as stand-alone control devices. 

Overpressure Blocked or restricted outlet Inflow exceeds outflow Gas blowby (upstream component) Pressure control system failure Thermal expansion Excess heat input High pressure... 

Water can be trapped behind heat exchanger baffles and then suddenly vaporized by circulation of hot oil. It can also be trapped in dead-ends and U-bends in pipework (see Section 9.1.1). Such U-bends can form when one end of a horizontal pipe is raised by thermal expansion. The trays in a distillation column were damaged during startup when hot gas met water, from previous steaming, dripping down the column [3J. Section 17.12 describes an incident somewhat similar to a foamover. 

CWorine is an elemental ehemieal tliat exists as a gas at ambient eonditions but liquefies at moderate pressures. Some of its eommon pliysieal properties are listed in Table 8.1.1. Chlorine is sliglitly water soluble, is yellow-green in the gaseous state, and lias a strong eliaraeteristie odor. Because ehlorine gas is about 2.5 times denser titan air, it tends to stay elose to the ground when released into tlie atmosphere. Liquid ehlorine lias a elear amber color one volume of liquid ean vaporize to about 460 volumes of gas. In addition, liquid elilorine has a large eoeffieient of thermal expansion. 

Cyclic Oxidation In many industrial applications it is particularly important for the component to be resistant to thermal shock for example, resistance-heating wires or blading for gas turbines. Chromia, and especially alumina, scales that form on nickel-base alloys are prone to spalling when thermally cycled as a result of the stress build-up arising from the mismatch in the thermal expansion coefficients of the oxide and the alloy as well as that derived from the growth process. A very useful compilation of data on the cyclic oxidation of about 40 superalloys in the temperature range 1 000-1 I50°C has been made by Barrett et... 

There are, however, three important factors that control the nature and properties of the deposit to some degree which must be reviewed at this time epitaxy, gas-phase precipitation, and thermal expansion. 

Consider a planar premixed flame front, such as that sketched in Figure 5.1.1. For the moment, we will be interested only in long length scales and we will treat the flame as an infinitely thin interface that transforms cold reactive gas, at temperature and density T p, into hot burnt gas at temperature and density T, A.-The flame front propagates at speed Sl into the xmbumt gas. We place ourselves in the reference frame of the front, so cold gas enters the front at speed = Su and because of thermal expansion, the hot gases leave the front at velocity 14 = Sl(Po/a)- The density ratio, Po/Pb, is roughly equal to the... 

Liquefied Petroleum Gas (LPG) (Cont d) storage, 403 transportation, 483 Liquids density, 49 effluent, 509 flashing, 50 immiscible, 49 thermal expansion, 49, 65 vaporization, 45, 246... 

Develop a detailed mechanical design of the CO conversion reactor, paying particular attention to the choice of alloy steels versus refractory linings, provisions for thermal expansion, inlet gas distribution, catalyst bed-support design, facilities for charging and discharging catalyst and provisions for instrumentation. 

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