Liquefaction of gases

An expansion turbine (also called turboexpander) converts gas or vapor energy into mechanical work as the gas or vapor expands through the turbine. The internal energy of the gas decreases as work is done. The exit temperature of the gas may be very low. Therefore, the expander has the ability to act as a refrigerator in the separation and liquefaction of gases. 

Cryogenics -150° to -200°F Liquefaction of gases, and power/temperature recovery from natural gas... 

Laplace s equation, 146 Least action, principle of, 69, 304 Line of heterogeneous states, 172 Liquefaction of gases, 167, 173 of mixtures, 428... 

INDUSTRIAL GASES, together with the Liquefaction of Gases. By various authors, including H. S. REDGROVE. (Crosby Lockwood, Second Impression, 1918, 9S. net.)... 

Absorption Air-Conditioning Brayton Gas Refrigeration Cycle Stirling Refrigeration Cycle Ericsson Cycle Liquefaction of Gases Nonazeotropic Mixture Refrigeration Cycle Design Examples Summary... 

Faroday, Michael (1791—1867). A Brit chemist and physicist noted for liquefaction of gases, the effect of electric current on the magnetic needle, electrolysis, and as discoverer of benzene. He also introduce d the law stating that the wt of an ion deposited electrolyti-cally is proportional to the strength of the current passing thru the soln... 

Equations of state (EOS) offer many rich enhancements to the simple pV = nRT ideal gas law. Obviously, EOS were developed to better calculate p, V, and T, values for real gases. The point here is such equations are excellent vehicles with which to introduce the fact that gases cannot be really treated as point spheres without mutual interactions. Perhaps the best demonstration of the existence of intermolecular forces that can also be quantified is the Joule-Thomson experiment. Too often this experiment is not discussed in the physical chemistry course. It should be. The effect could not exist if intermolecular forces were not real. The practical realization of the effect is the liquefaction of gases, nitrogen and oxygen, especially. 

The attractions of interest in colloid stability usually arise from the van der Waals forces, and we see below that they are scaled-up versions of the same intermolecular attractions discussed in the following section and that contribute to the nonideality and ultimately liquefaction of gases. In view of Figure 10.1a, we are interested in both the magnitude and the distance dependence of these attractive forces. 

Cryogenetic piston pumps are applied for the liquefaction of gases and for process applications at high-pressure [11] - and extremely low-temperature conditions. 

The temperatures on the envelope where pn = 0 are called inversion temperatures, Tt. At any given pressure, up to a maximum pressure, a given gas exhibits two inversion temperatures. The Joule-Thomson effect is important in refrigeration and in the liquefaction of gases. Modern refrigeration uses the larger effect of the evaporation of working fluids such as the chlorofluorocarbons. 

Problem 13 Mention the various methods that are adopted for producing cold and what is the lowest temperature hitherto attained How has it been reached Show how these have been used in the liquefaction of gases Mention the importance of liquefaction. What is inversion temperature. 

Oxygen was not obtained in the liquid state by Faraday m his classical investigations on the liquefaction of gases, because the refrigerating agents used by him did not suffice for the attainment of the critical temperature of the gas, above which it is impossible to effect liquefaction, no matter how great the pressure. 

However, as the temperature of a gas is lowered, the kinetic energy of the molecules decreases. The volume occupied by the gas also decreases. At a sufficiently low temperature, some of the slow moving molecules cannot resist the force of attraction and they come closer and closer and ultimately the gas change s into the liquid state. Thus, liquefaction of gases results from decrease of temperature. 

Increase of pressure has also the effect of bringing the gaseous molecules closer and closer to one another (due to decrease in volume). This is an additional helpful factor in converting a gas into liquid. Thus, increase of pressure and decrease of temperature both tend to cause liquefaction of gases. For instance, sulphur dioxide can be liquefied at -8 C if the pressure is 1 atm. But it can be liquefied even at a higher temperature of 20 C if the pressure is increased to 3.24 atm. 

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