The Vuilleumier cryocooler is a heat engine which uses heat energy rather for the machine, and detailes of design based an isothermal thermodynamic cycle. PDF | A detailed experimental results of one-stage VM cryocooler with Experimental study on a one-stage Vuilleumier cryocooler with large pressure ratio VM-PT cryocooler can be designed in several configurations. Download Citation on ResearchGate | Study of a Vuilleumier cycle cryogenic This effort led to the selection of an optimum refrigerator design for the LSIR the feasibility of using a Vuilleumier cryocooler to cool a flight-type detector .
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A Cryocooler is a standalone cooler, usually of table-top size. It is used to cool some particular application to cryogenic temperatures. A review is given by Radebaugh. Heat exchangers are important components of all cryocoolers.
Ideal heat exchangers have no flow resistance and the exit gas temperature is the same as the fixed body temperature T X of the heat exchanger. Note that even a perfect heat exchanger will not affect the entrance temperature T i of the gas.
This leads to losses. An important component of refrigerators, operating with oscillatory flows, is the regenerator. A regenerator consists of a matrix of a solid porous material, such as granular particles or metal sieves, through which gas flows back and forth. Periodically heat is stored and released by the material. The heat contact with the gas must ceyocooler good and the flow resistance of the matrix must be low. These are conflicting requirements. The thermodynamic and hydrodynamic properties of regenerators are very complicated, so one usually makes simplifying models.
In its most extreme form an ideal regenerator has the following properties:. The recent progress in the cryocooler field is for a great deal due to the development of new materials with a cryicooler heat capacity below 10K. The basic type of Stirling-type cooler is depicted in Fig. From left to right it consists of a piston, a compression space, and heat exchanger all at ambient temperature T aa ov, and a heat exchanger, expansion space, and a piston all at the low temperature T L.
Left and right the thermal contact with the surroundings at the temperatures T a and T L is supposed to be perfect so that the compression and expansion are isothermal. The work, performed during the expansion, is used to reduce the total input power.
Usually helium is the working fluid. The cooling cycle is split in 4 steps as depicted in Fig.
The cycle starts when the two pistons are in their most left positions:. In the pV diagram Fig.
Cryocooler – Wikipedia
The volume V is the volume between the two pistons. In practice the cycle is not divided in discrete steps as described above. Usually the motions of both pistons are driven by a common rotary axes which makes the motions harmonic. It is not so practical to have a cold piston, as described above, so, in many cases, a displacer is used instead of the cold piston. A displacer is a solid body which moves back and forth in the cold head driving the gas back and forth between the warm and the cold end of the cold head via the regenerator.
No work is required to move the displacer since, ideally there is no pressure drop over it. Typically its motion is 90 degrees out of phase with the piston. Another type of Stirling cooler is the split-pair type Fig. Usually there are two pistons moving in opposite directions driven by AC magnetic fields as in loudspeakers.
The pistons can be suspended by so-called flexure bearings. They provide stiffness in the radial direction and flexibility in the axial direction. The pistons and the compressor casing don’t touch so no lubricants are needed and there is no wear.
The regenerator in the cold finger is suspended by a spring. The cooler operates at a frequency near the resonance frequency of the mass-spring system of the cold finger. Gifford-McMahon GM coolers  have found widespread application in many low-temperature systems e.
Helium at pressures in the 10 to 30 bar range is the working fluid. The cold head contains a compression and expansion space, a regenerator, and a displacer. Usually the regenerator and the displacer are combined in one body. The pressure variations in the cold head are obtained by connecting it periodically to the high- and low-pressure sides of a compressor by a rotating valve. Its position is synchronized with the motion of the displacer. During the opening and closing of the valves irreversible processes take place, so GM-coolers have intrinsic losses.
This is a clear disadvantage of this type of cooler.
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In this way the swept volume of the compressor can be 50 60 times smaller than of the cooler. Basically cheap compressors of domestic refrigerators can be used, but one must prevent overheating of the compressor as it is not designed for helium. One must also prevent oil vapor from entering the regenerator by high-quality purification traps.
The cycle starts with the low-pressure lp valve closed, the high-pressure hp valve open, and the displacer all the way to the right so in the cold region. All the gas is at room temperature. The pulse tube refrigerator is treated in a separate article. From left to right it consists of: Basically it is a very simple type of cooler which is widely applied as cryocooler or as the final stage of liquefactors.
It can easily be miniaturized, but it is also used on a very large scale in the liquefaction of natural gas. A schematic diagram of a JT liquefier, is given in Fig. It consists of a compressor, a counterflow heat exchanger, a JT valve, and a reservoir. At the inlet of the compressor the gas is at room temperature K and a pressure of 1 bar point a. The compression heat is removed by cooling water. After compression the gas temperature is ambient temperature K and the pressure is bar point b.
Next it enters the warm high-pressure side of the counterflow heat exchanger where it is precooled. It viulleumier the exchanger at point c. After the JT expansion, point d, it has a temperature of The liquid fraction is x.
The liquid leaves the system at the bottom of the reservoir point e and the gas fraction 1- x flows into the cold low-pressure side of the counterflow heat exchanger point f. It leaves the heat exchanger at room temperature point a. In order to keep the system in the steady state gas is supplied to compensate for the liquid fraction x that has been removed.
When used as a cryocooler it is preferable to use gas mixtures instead of pure nitrogen. In this way the efficiency is improved and the high pressure is much lower than bar. A more detailed description of Joule-Thomson coolers and Joule-Thomson refrigerators can be found in .