Gas calorimeter

Abel (64), of Burlot-Malsallez (65), and of Bichel Mettegang (66-9)- Also are described Calorimeters of Landrieu-Malsallez and Gas Calorimeter (69-70) Determination of Temperature of Explosion (70-1) Determination of Ignition Temperature (72-3 108-... 

As was mentioned already, heats of combustion can be determined either experimentally or by calculation, the latter method being slightly less accurate than the former. The experimental methods may be subdivided into those employing the "universal burner (or gas) calorimeter or the "bomb calorimeter . The former method is applicable only to gases or to substances easily volatile at room temperature, whereas the latter method is applicable to liquids and solids... 

Other calorimeters include heat-leak calorimeters", such as of Thomas Parks (Ref 25,p 545), "automatic calorimeters such as of Andrews, Berl Stull (Ref 25,p 551) "vacum-walled calorimeter (Ref 3,p 153) "aneriod (unstirred) calorimeters" (Ref 3,pp 23,160-7), "rotating bomb calorimeters", such as of Popov, Shirokikh and of Hubbard (Ref 25,p 594) liquid-phase calorimeter" of Kistiakowsky (Ref 25,p 636), "gas calorimeter of Cutler- Hammer (Ref 18a), calorimeter for gaseous heat capacities of Waddington (Ref 15,p 802), "flow calorimeter of Junkers (Ref 15,p 805)," flow calorimeter of Osborne et al (Ref 25,p 565), "flow calorimeter of Pitzer (Ref 25,p 566), "flow calorimeter of Bennewitz Schulze (Ref 25,p 567) and "fiame calorimeter of Rossini" (Ref 25,pp 600--2). An apparatus for detn of heats of vaporization is described in Ref 25,p 615 and an "adsorption calorimeter in Ref 25,p 618... 

In Europe and in other countries where the metric system is used, natural gas calorimeters are calibrated in megajoule units, and in the United States in Btu units. The output of the calorimeter may represent the gross calorific value (sometimes referred to as upper heating value or gross heating value), the net calorific value (sometimes referred to as lower heating value or net heating value), or the Wobbe index. 

A new state-of-the-art reference gas calorimeter has been developed recently for the more accurate determination of the calorific values of pure hydrocarbons, as well as for fuel-gas mixtures [188]. 

The sensor gas calorimeter (SGC) basically consists of a classical volumetric gas adsorption device complemented by two gas thermometers (cp. Fig. 2.9). The core of the instrument is an adsorption vessel which is placed within a second vessel, the sensor gas jacket. This jacket vessel is filled with gas at pressure (psc) acting as a sensor via a capillary (1) coimecting the vessel with a difference manometer (P3). Additionally, a reference vessel also filled with the (same) sensor gas at pressure (prg) is placed in the thermostat and cormected via capillary (2) to the manometer (P3). Upon opening the valves (V7, V7A) the pressures (psc, Prg) of the sensor gases in the jacket vessel and the reference vessel are equalized, i. e. we have pso = Prg. Thermal equilibrium at temperature (T ) in the system... 

Figure 2.10. Sensor gas calorimeter (SGC) for simultaneous measurements of adsorption isotherms and enthalpies. IFT, University of Siegen, 2003.

Figure 2.11. Calibration experiments of the sensor gas calorimeter (SGC). Ohm s heat of (0.5, 1.0, 1.5. .. 5.0) J is supplied by electric heating inside the adsorption vessel. The corresponding pressure signals increase in height and size with increasing heat input. The area below these curves is direct proportional to the total heat supplied to the SGC. Sensor gas used N2, 5.0, p = 0.15 MPa, T = 298 K.

In conclusion it can be said, that the sensor gas calorimeter (SCjC) is a very useful instrument for simultaneous measurements of adsorption isotherms and (integral and differential) heats of adsorption. Also hints on the kinetics of the gas adsorption process can be gained from the time dependence of the pressure signal curve, cp. Fig. 2.11. However, to achieve high sensitivity and accuracy of measurements, type and amount of the sensor gas have to be chosen very carefully. At low temperatures (77 K) helium is recommended at reference pressures of about (0.1 - 0,2) MPa. At higher temperatures (298 K) nitrogen should be preferred at the same pressures, [2.23, 2.29]. 

The instrument can also be described further in terms of technical characteristics that are self-explanatory to the specialist. Examples are the titration calorimeter, bomb calorimeter, gas calorimeter, fiow calorimeter, drop calorimeter, heat flow calorimeter, and ice calorimeter. The designation microcalorimeter should be avoided because it does not show whether the term micro refers to the size of the device, the sample container, or the quantity of heat measured. 

Alexandrov, Y.I. (2002) Estimation of the uncertainty for an isothermal precision gas calorimeters. Thermochim. Acta, 382, 55-64. 

Figure 8. Schematic diagram of a sensor gas calorimeter (SGC) allowing simultaneous measurements of the heat and the mass of a gas adsorbed on a sorbent sample [8]. On the right hand side a laboratory scaled instrument and auxiliary equipment (stirrer, gas supply system, PC etc.) is shown as is used at IFT, University of Siegen, since 2003.

Figure 9. Differential and integral heat of adsorption of n-butane 1500 at 298 K measured with a sensor gas calorimeter [8].

Equilibrium is characterized by constancy of some properties but it is not the only requirement. When some of the properties of a system are constant but equilibrium does not exist, the system is said to be in a steady state. In the experimental determination of calorific value of a gaseous fuel by Boy s Gas Calorimeter, the following conditions characterise the steady state ... 

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