Claude cycle

FIG. 11-113 Claude cycle refrigerator utilizing both expansion processes. 

This cycle also uses continuous counterflow heat exchanger and is closely related to the Joule-Thomson and Claude cycles as shown in Fig. 5.15(a) [60], The cryocooling or reverse Brayton cycle derives from a reciprocating gas engine patented by G. B. Brayton in... 

It is not uncommon to combine the isentropic and isenthalpic expansions to allow the formation of liquid in the refrigerator. This is done because of the technical difficulties associated with forming liquid in the engine. The Claude cycle is an example of a combination of these methods and is shown in Fig. 5a along with the corresponding temperature-entropy diagram (Fig. 5b). 

One modification of the Claude cycle that has been used extensively in high-pressure liquefaction plants for air is the Heylandt cycle. In this cycle, the first warm heat exchanger in Fig. 5a has been eliminated, permitting the inlet of the expander to operate with ambient temperature... 

FIGURE 23.9 Temperature vs. entropy diagram for the Claude cycle of liquefaction. Details are given in... 

The Claude cycle is shown in Figure 6. This is a compound cycle which is actually a combination of the simple Joule-Thompson cycle and Brayton cycle. Most modern air separation plants utilize a variation of the Claude cycle to provide the refrigeration needed to liquefy air for distillation. 

The Claude cycle has the advantage of being more efficient than the simple Linde cycle on the basis of work per unit mass of gas liquefied. As a result, it is possible to operate at a lower compressor discharge pressure than in the Linde cycle. 

This cycle is a variation of the Claude cycle. If air is the working fluid, the compressor discharge pressure is 200 bars (2885 psig) and the liquid fraction produced in the Joule-Thompson expansion is about 0.6, then the optimum temperature for the inlet to the expansion turbine is about ambi-... 

The Claude cycle may be used without modification to liquefy hydrogen or neon, since this system does not primarily depend on the expansion valve to produce low temperatures. However, by using a liquid nitrogen precooling bath with the Claude system (see Fig. 4.13), a figure of merit 50-70% higher than that for the precooled Linde system may be obtained. 

Example 4.12. Many of the large hydrogen liquefaction plants use a precooled Claude cycle with one expander similar to that shown in Fig. 4.13. This system could also be used as a refrigerator to cool helium gas. For the operating conditions shown below, determine the following ... 

Fig. 4.13. Precooled Claude cycle used for liquefying neon and hydrogen.

The Kapitza system, on the other hand, has been used extensively in the low-pressure liquefaction of air. This modified Claude cycle was one of the first systems to use a rotary expansion engine in place of a reciprocating expander. This permitted the third or low-temperature heat exchanger of the Claude cycle to be eliminated. In addition, the first or high-temperature heat... 

Another modification of the basic Claude cycle is the dual-pressure Claude cycle, similar in principle to the Linde dual-pressure system presented in Fig. 4.8. In this dual-pressure cycle, shown in Fig. 4.17, only the gas that is sent through the expansion valve is compressed from the low pressure to the high pressure this reduces the w ork requirement per unit mass of gas liquefied. To illustrate the advantage of the Claude dual-pressure cycle over the Linde dual-pressure cycle, Barron has shown that, in the liquefaction of air, the liquid yield can be doubled while the work per unit mass liquefied can... 

Still another extension of the Claude cycle is the Collins helium liquefier, schematically represented in Fig. 4.18 with a typical set of operating conditions. Depending upon the helium inlet pressure, from two to five expansion engines are used in this system. The addition of a liquid nitrogen precoolant bath to this system results in a two- to threefold increase in liquefaction performance. 

Fig. 5.38. Two types of journal bearings developed for miniature Claude cycle refrigerators.

A Claude cycle may be used to demonstrate the effect that compressor and expander efficiencies have on a system. Figure 5.40 shows the T-S diagram of such a cycle. The actual work of isothermal compression per unit mass of gas liquefied is... 

Fig. 5.40. Claude cycle with an expander having a thermodynamic efficiency less than unity. The gas leaves the expander at point e in the case of the reversible expander.

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