Linde refrigerator

The solution to Problem 2.33 shows that the Joule-Thomson coefficient can be expressed in terms of the parameters representing the attractive and repulsive interactions in a real gas. If the attractive forces predominate, then expanding the gas will reduce its energy and hence its temperature. This reduction in temperature could continue until the temperature of the gas falls below its condensation point. This is the principle underlying the liquefaction of gases with the Linde refrigerator, which utilizes the Joule-Thomson effect. See Section 2.12 for a more complete discussion. 

Prepare a plot that shows the nitrogen mass flow rate that is required to provide 0.5, 1, and 2 kW of refrigeration at 77.3 K as a function of the upper operating pressure of a simple Linde refrigeration system. Assume that the heat exchanger and compressor are ideal. Compression is isothermal at 300 K. 

A precooled Linde refrigerator employs parahydrogen and nitrogen as the working fluids. The separate nitrogen cycle operates between 0.101 and 20.2 MPa while the hydrogen cycle... 

Linde process A high-pressure process for the production of liquid oxygen and nitrogen by compression to about 200 bar (20MN/m ) followed by refrigeration and fractionation in a double column. 

We will then describe the Collins helium liquefier and coolers which use turboexpanders (Linde He liquefier). At the end of the chapter, we will describe cooling cycles which use regenerators and other cycles used in cryocoolers (Philips-Stirling, Gifford-McMahon (GM), Klimenko cycles and pulse tube refrigerators (PTRs)). 

The industry got its start in 1895 when Dr. Carl von Linde, a pioneer in refrigeration technology, received the first patent for the liquefaction and rectification of air into its major components oxygen and nitrogen (Almqvist, E., IOMA). Georges Claude soon developed this work further in Paris, France, improving the efficiency of the liquefaction process. 

FIGURE 2 (a) Schematic for simple Linde-cycle refrigerator (b) temperature-entropy diagram for cycle. 

This simplest kind of liquefaction system, known as the Linde process, is shown in Fig. 9.9. After compression, the gas is precooled to ambient temperature. It may even be further cooled by refrigeration. The lower the temperature of the gas entering the throttle valve, the greater the fraction of gas that is liquefied. For example, evaporating a refrigerant in the precooler at -40(°F) gives a lower temperature into the valve than if water at 70(°F) is the cooling medium. 

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