Joule-Thompson effects

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... 

EXAMPLE Throttling or Joule Thompson Effect. PROBLEM If a gas of 0.8 Sp. Gravity at 2,000 5 Abs. and 200°F expands through a small orifice without the addition or subtraction of heat and is brought finally to its initial velocity and a pressure of 50 Abs., what is its temperature ... 

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... 

The equation-of-state method, on the other hand, uses typically three parameters p, T andft/for each pure component and one binary interactioncparameter k,, which can often be taken as constant over a relatively wide temperature range. It represents the pure-component vapour pressure curve over a wider temperature range, includes the critical data p and T, and besides predicting the phase equilibrium also describes volume, enthalpy and entropy, thus enabling the heat of mixing, Joule-Thompson effect, adiabatic compressibility in the two-phase region etc. to be calculated. 

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. 

Joule-Thompson effect The physical process in which the temperature of a gas is changed by allowing the gas to expand. Depending on the gas, the pressure, and the temperature, the change can be positive or negative. 

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. 

Use Table 2.1 to derive an expression for the total differential of the enthalpy in terms of C° and a(= (1 /V)(dV/dT)p). In other words, start with dH = (dH/dT)pdT + (dH/dP)TdP and find expressions for the two partial derivative terms from Table 2.1. You will find that if in this resulting equation you let dH = 0, you get an expression for (dT/dP)H identical to that in equation 8.1 (Chapter 8). This derivation is used by Ramberg (1971) in his elegant discussion of the Joule-Thompson effect in a gravitational field. 

In a PGSS experiment, the SCF is first dissolved in the HC by increasing the pressure until a melt is obtained. The gas-saturated solution is then expanded through a nozzle where it is cooled simultaneously by evaporation and Joule-Thompson effects. In this way supersaturation conditions are reached, and solid particles are formed. Again, the product is completely free of organic solvents. The amount of SCF needed is low, between 0.2 and 0.6 kg per kilogram of HC. 

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

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