Joule-Thompson effect expansion

Eor the experimental determination of the temperature dependence, the whole sample with the electrical leads has to be in temperature equilibrium at least for the time ofmeasure-ment. Due to the sniall size of the samples, the van der Pauw technique is particularly suited for such measurements and some corresponding measurement systenns are equipped with an integrated temperature chamber. A very flexible and convenient temperature control can be realized with a vacuum chamber, with the sample cooled by the Joule-Thompson effect (expansion cooling of N2 from a capillary nozzle), or heated by a resistive heater. In this way, temperature dependent measurements in the range between 80 and 580 K can be performed and the temperature can be set very accurately, which is also an important precondition for the Hall measurement (Section Hall effect measurement ). Simpler systems are using a cryostat with liquid nitrogen or helium, which allows measurements at temperatures down to 77 and 4 K, respectively. 

Dehydration may also be accompHshed by expansion refrigeration which utilizes the Joule-Thompson effect. This technique is normally used when the prime objective is hydrocarbon recovery. 

Physical characteristics Molecular weight Vapour density Specific gravity Melting point Boiling point Solubility/miscibility with water Viscosity Particle size size distribution Eoaming/emulsification characteristics Critical temperature/pressure Expansion coefficient Surface tension Joule-Thompson effect Caking properties... 

A Mollier Diagram is useful for the expansion of a specific gas/vapor or multicomponent vapor fluid. See Figure 12-91 for comparison of (1) constant enthalpy (Joule-Thompson effect), isenthalpic, and (2) isentropic (constant entropy), which provides the colder temperature. Note that the expander indicated on the figure is somewhere between isenthalpic and isentropic or polytropic. See Figure 12-92. ... 

An additional complication may arise in a few cases from the Joule-Thompson effect during expansion of a gas through a membrane changing the temperature. High-pressure CO2 is an example. 

Josephson junctions, 23 820, 821 Josephson string, 23 827 Josephson vortex, 23 827 Jost Report, 15 201, 202 Joule-Thompson effect, 12 374 Joule-Thomson expansion, 24 647, 648, 650-651... 

By dissolving the compressible media in a liquid, a so-called gas-saturated solution may be formed. By expansion of such a solution in an expansion unit (e.g., a nozzle) the compressed medium is evaporated and the solution is cooled. Owing to the cooling caused by evaporation and/or the Joule-Thompson effect the temperature of the two-phase flow after the expansion nozzle is lowered. At a certain point, the crystallization temperature of the substance to be solidified is reached, and solid particles are formed and cooled further. 

Liquefaction of the purified air is accomplished using the Joule-Thompson effect, which is the cooling effect obtained from a compressed gas when it is allowed to expand. By using this expansion-cooling effect repetitively, and by employing the chilled expanded gas to prechill the compressed gas before expansion, air may be liquefied by employing compression pressures of only about 10 atm (about 150 psig, Eig. 11.1). It is not possible to accomplish... 

The Linde cycle is a simple cryogenic process based on Joule-Thompson effect. It is composed of different steps the gas is first compressed, then preliminarily cooled in a heat exchanger using liquid nitrogen, finally it passes through a lamination throttle valve to exploit the benefits of Joule-Thomson expansion. Some liquid is produced, and the vapour is separated from the liquid phase and returns back to the compressor through the heat exchanger. A simplified scheme of the overall process is reported in Fig. 2.9. 

A metering valve PRV for pressure reduction after the vessel. It must be heated to compensate for Joule-Thompson effects during expansion. 

Many studies on systems in the current literature did not consider the Joule-Thompson effect caused by the expansion of permeate gas due to the pressure difference between the high retentate pressure and the low permeate pressure, also known as transmembrane pressure. This expansion leads to a decrease in the permeate temperature, which in turn decreases the membrane permeance. So, ignoring the Joule-Thomson effect may result in a wrong estimation of membrane separation performance and consequently of the reboiler/condenser duties and utility savings obtained from an HMD system. The membrane model employed in the present study takes into account the Joule-Thompson effect by including the following energy balance [Equation (10.2)] ... 

On expansion the gas cools rapidly (Joule-Thompson effect) and tends to block the back pressure restrictor valve (particularly when the simple manual valves are used) with solid carbon dioxide and precipitated solutes. 

Where they have a positive slope, water cools on adiabatic expansion and warms if adiabatically compressed, and the two regions are separated by the Joule-Thompson inversion curve. Much the same information is contained in the enthalpy-pressure diagram (Figure 8.6), where it can be seen that constant enthalpy changes in pressure lead to increases in temperature in one region and decreases in another. The effect of dissolved NaCl on the Joule-Thompson coefficient has been calculated by Wood and Spera (1984), and the effect will be similar for other electrolytes. Because the addition of most electrolytes to water results in a decrease in V and in a, fijT is smaller, and the net effect is to move the inversion curve to higher temperatures, as shown in Figure 8.5. 

J.P. Joule and W. Thompson discovered the cooling effect caused by the expansion of gases during pressure release. 

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