Kapitza system

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... 

From Fig. 10.13, we see the latter condition is fulfilled in the first three cases, but not in the fourth case. The most stable situation is obtained with Rx. The choice R = RcosL is however usually adopted when the power supplied to the resistor must be measured. The control of temperature in the real (dynamic) case is much more complex. The problem is similar to that encountered in electronic or mechanical systems. The advantage in the cryogenic case is the absence of thermal inductors . Nevertheless, the heat capacities and heat resistances often show a steep dependence on temperature (i.e. 1 /T3 of Kapitza resistance) which makes the temperature control quite difficult. Moreover, some parameters vary from run to run for example, the cooling power of a dilution refrigerator depends on the residual pressure in the vacuum enclosure, on the quantity and ratio of 3He/4He mixture, etc. 

Wientjes KJC, Grob U, Hattemer A, Hoogenberg K, Jungheim K, Kapitza C, Schoonen AJM. Effects of microdialysis catheter insertion into the subcutaneous adipose tissue assessed by the SCGM1 system. Diabetes Technology Therapeutics 2003,5,615-620. 

The c ontrol o f p honon t emperature i n e lectron-phonon c oupling measurements i s critical for a correct estimation of the electron-phonon coupling constant. In our experiment an additional electrically isolated S-Sm-S thermometer was placed near the Si film. Below IK the electron-phonon thermal resistance in silicon is considerably larger than the Kapitza resistance between Si film and the silicon oxide layer, and therefore the S-Sm-S thermometer next to the silicon film was assumed to be at approximately the same temperature as the phonon system in the silicon film. 

Hoffmann, M., Borchert, C., Dietrich, C., Schirmeier, H., Kapitza, R., Spinczyk, O., Lohmann, D. Effectiveness of fault detection mechanisms in static and dynamic operating system designs. In 17th IEEE Int. Symp. on OO Real-Time Distrib. Computing, ISORC 2014. IEEE (2014)... 

The work of Kapitza [7] and the exceptionally notable developments of Collins [8] had in common the utilization of expansion engines in combination with counterflow heat exchangers, and both were successful in liquefying helium. The Collins system was the first to use multiple engines operating at intermediate temperatures and thereby eliminate the need for any auxiliary refrigeration. This feature, combined with certain constructional advantages [9], has led to a wide acceptance of the Collins system for helium liquefaction. 

The early concepts of Kirk and Stirling in which a reciprocating-flow thermal regenerator is used in place of a countercurrent heat exchanger have recently been refined and developed effectively into an air liquefier by the Philips Company [10]. The system is characterized by the use of two articulated pistons which provide a compression space and an expansion space, interconnected through a thermal regenerator. Unlike the Kapitza or Collins system, there are... 

In an ideal Kapitza liquefaction system, nitrogen gas enters the compressor at 0.101 MPa and 295 K and is compressed isothermally and reversibly to 5.05 MPa. The gas enters the adiabatic and reversible expander at a condition of 5.05 MPa and 250 K. The expander handles 60 % of the high-pressure gas. Assuming ideal heat exchangers, determine the liquid yield, the work per unit mass compressed, and the work per unit mass liquefied when the expander work is utilized in the compression process. 

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