EP1247050B1 - Periodic refrigerating machine - Google Patents

Abstract

The machine has a thermal power amplifier based on the pulsed pipe process and a pulsed pipe cooler connected in series. The thermal power amplifier consists of a compressor, first and third heat exchangers delivering heat to the surroundings, a regenerator, a second heat exchanger taking heat into the amplifier and a pulsed pipe. The pulsed pipe cooler consists of a regenerator, two heat exchangers, a pulsed pipe and an expander.

Description

The invention relates to a periodically operating chiller.

Kompression des Gases;

Verschiebung des Gases in Richtung Expander;

Expansion des Gases;

Verschiebung des Gases in Richtung Kompressor:
Eine solche Kältemaschine ist aus Dokument US-A-5 269 147 schon bekannt.

It is known that a refrigeration process, which works on the principle of a Stirling engine, can be constructed so that there are no mechanical components to be moved in the cold part of such an engine. The cooler of this type consists of a compressor piston which is moved periodically at ambient temperature, a thermally insulated regenerator, a likewise thermally insulated pulse tube which is provided with heat exchangers at both ends and an expansion piston which is also operated at ambient temperature. Both pistons are moved in such a way that the following cycle is run in the pulse tube:

Compression of the gas;

Displacement of the gas in the direction of the expander;

Expansion of the gas;

Shifting the gas towards the compressor:
Such a refrigerator is already known from document US-A-5 269 147.

The closer analysis shows that with the compressor is relatively a lot of work is done. A small proportion of it will recovered on the expander. The difference is converted into heat which is essentially derived in the area of the compressor must be (see also Figure 6).

Chillers of this type are in differently modified operating modes been realized. With one-step arrangements can the temperature typically from room temperature to about 25K can be lowered [I, II], with two-stage devices even to below 4 K [III].

The following consideration led to the invention:

If at the heat exchanger between the regenerator and the So much heat is supplied to the pulse tube that there is no cooling but heating takes place above room temperature, the work to be performed on the expander is greater than that compression power mechanically supplied to the system. A part the one at the heat exchanger between the regenerator and the pulse tube that of the heat exchanger at the end of the pulse tube Heat is converted into work and thus leads to reinforcement mechanical performance.

The work gained is for driving a pulse tube cooler available.

In claim 1 is the construction of such a thermal Power amplifier and one connected to its output, So pulse tube cooler connected in series in his Characteristics marked.

The thermal power amplifier from a compressor device to which a first heat exchanger is attached, to the Environment gives off heat. A regenerator is attached to this. At the other end there is another heat exchanger over which Heat is introduced into the power amplifier. This heat exchanger is therefore referred to as a heater. To the heater as a result, the pulse tube of the power transmitter is installed and is completed with a heat exchanger that gives off heat. On the pulse tube cooler is attached to this last heat exchanger, the last heat exchanger of the power amplifier the first of the pulse tube cooler, if you will. Between the The regenerator and pulse tube of the pulse tube cooler is the heat exchanger, which forms the useful cold zone. Finally, that closes Pulse tube with a last heat exchanger and the one to be coupled to it Expander device from.

Zunächst die beiden Varianten mit bewegten Bauteilen:

Anspruch 2 der Stirling-Prozess mit Kolbenexpander,

Anspruch 3 der Stirling-Prozeß mit passivem Expander, und dann die beiden Varianten, die keine bewegten Bauteile haben:

Anspruch 4 die Gifford-McMahon-Betriebsweise mit einem Hoch- und

Niederdruckreservoir, die beide über mit je einem Ventil versehenen Zuleitungen am Regenerator ankoppeln, und mit passivem Expander wie in Anspruch 3 und schließlich

Anspruch 5 die Gifford-McMahon-Betriebsweise mit einer Kompressionseinrichtung, wie in Anspruch4 beschrieben, und je einer mit einem steuerbaren Ventil versehen Zuleitung vom Hoch- und Niederdruckreservoir, dem ventilgesteuertem Expander, zum Pulsrohr.

In subclaims 2 to 5, different operating variants are listed according to the known operating variants of pulse tube coolers [I to III]:

First the two variants with moving components:

Claim 2 the Stirling process with piston expander,

Claim 3 the Stirling process with a passive expander, and then the two variants that have no moving parts:

Claim 4 the Gifford-McMahon mode with a high and

Low-pressure reservoir, both of which couple to the regenerator via supply lines each provided with a valve, and with a passive expander as in claim 3 and finally

Claim 5 the Gifford-McMahon mode of operation with a compression device, as described in claim 4, and each with a controllable valve supply line from the high and low pressure reservoir, the valve-controlled expander, to the pulse tube.

The pulse tube amplifier can be electrically heated on the one hand (Claim 6), on the other hand, similar to a Stirling engine, can also use other heat sources such as solar heating or Combustion [5] can be used (claim 7). In this case the cooler is operated with even lower primary energy requirements become.

besserer Wirkungsgrad, d.h. weniger Primärenergie bei gleicher Kälteleistung;

kostengünstige Fertigung des Kühlers - im Vergleich zu einem mechanischen Kompressor ist der Pulsrohrverstärker eine sehr einfach zu fertigende Baugruppe, der Zusatzaufwand wiegt die Kosteneinsparung aufgrund eines kleineren Kompressors auf;

geringere Betriebskosten;

geringe Wartungskosten - der Pulsrohrverstärker selbst ist wartungsfrei, die für den Pulsrohrkühler in jedem Fall erforderlichen Zusatzkomponenten wie Kompressor und Ventile, die regelmäßige Wartung bzw. Austausch erfordern, genügen in kleinerer Bauweise und sind dadurch billiger.

The following advantages are achieved with the invention:

better efficiency, ie less primary energy with the same cooling capacity;

Cost-effective production of the cooler - compared to a mechanical compressor, the pulse tube amplifier is a very easy to manufacture assembly, the additional effort outweighs the cost savings due to a smaller compressor;

lower operating costs;

Low maintenance costs - the pulse tube amplifier itself is maintenance-free, the additional components required for the pulse tube cooler such as compressors and valves, which require regular maintenance or replacement, are sufficient in a smaller design and are therefore cheaper.

Figur 1 den schematischen Aufbau der Kältemaschine als Reihenschaltung aus einem thermischen Verstärker mit einem Pulsrohrkühler und die Darstellung des Temperaturverlaufs entlang derselben,

Figur 2a die Realisierung als Stirling-Typ mit Doppelkolben,

Figur 2b die Realisierung als Stirling-Typ mit Einfachkolben und Doppeleinlaß-Phasenschieber,

Figur 2c Gifford-McMahon-Typ mit Doppeleinlaß-Phasenschieber,

Figur 2d Gifford-McMahon-Typ mit aktivem Phasenschieber,

Figur 3a das Phasendiagramm der Oszillationen von Druck und Volumenstrom am optimierten Pulsrohrkühler,

Figur 3b das Phasendiagramm der Oszillationen von Druck und Volumenstrom an der Kältemaschiene, der Reihenschaltung von Pulsrohrverstärker und Pulsrohrkühler,

Figur 4 den Aufbau der Kältemaschine mit ventilbetriebenem thermischen Verstärker,

Figur 5 den Heizer als Brennkammer-Heizung,

Figur 6 Funktionsprinzip des Pulsrohrkühlers und der Temperaturverlauf entlang ihm.

The invention is described below with reference to the drawing. The drawing consists of several figures. It shows:

FIG. 1 shows the schematic structure of the refrigeration machine as a series circuit comprising a thermal amplifier with a pulse tube cooler and the representation of the temperature profile along the same,

2a shows the realization as a Stirling type with a double piston,

FIG. 2b the realization as a Stirling type with a single piston and a double inlet phase shifter,

FIG. 2c Gifford-McMahon type with double inlet phase shifter,

FIG. 2d Gifford-McMahon type with active phase shifter,

FIG. 3a shows the phase diagram of the oscillations of pressure and volume flow on the optimized pulse tube cooler,

FIG. 3b shows the phase diagram of the oscillations of pressure and volume flow on the refrigeration machine, the series connection of pulse tube amplifier and pulse tube cooler,

FIG. 4 shows the structure of the refrigeration machine with a valve-operated thermal amplifier,

FIG. 5 the heater as a combustion chamber heater,

Figure 6 Principle of operation of the pulse tube cooler and the temperature curve along it.

First, the principle of operation of the Pulse tube cooler briefly recalls in its four phases of a period:

• Kompression des Gases.
• Verschiebung des Gases in Richtung Expander um eine Länge Δl, die kleiner als die Gesamtlänge des Pulsrohrs ist. Hierbei wird dem durch den Wärmeübertrager WÜ3 am Ende des dem Regenerator zugewandten Ende des Pulsrohrs strömenden Gas Wärme entzogen.
• Expansion des Gases.

The compressor and expander are operated in such a way that the following cycle is run through in the pulse tube:

• Compression of the gas.
• Displacement of the gas in the direction of the expander by a length Δl that is less than the total length of the pulse tube. This removes heat from the gas flowing through the heat exchanger WÜ3 at the end of the end of the pulse tube facing the regenerator.
• Expansion of the gas.

• Verschiebung des Gases zum Kompressor hin.

The entire gas column cools down, at the left end below the temperature of the heat exchanger located there.

• Displacement of the gas towards the compressor.

This causes the left heat exchanger WÜ1 to cool down or heat must be supplied there if this heat exchanger WÜ1 is operated at constant temperature.

The temperature occurring in the stationary case along the Pulse tube cooler is shown below.

The pulse tube cooler can be operated in different ways. Appropriate Operating schemes are in combination in Figures 2a to 2d represented with the thermal amplifier. The respective Art according to Figures 2a and 2b are based on the availability of a suitable piston compressor for driving the amplifier. According to the well-known Stirling process, the expansion Recovered work. According to the principle of the two Figures 2c and 2d is the gas flow supplied to the amplifier stamped with periodically switched valves. This becomes one High pressure tank, HD, (pressure reservoir) removed and into one Low pressure tank, LP, (low pressure reservoir) relaxed, similar to operating a Gifford-McMahon (GM) cooler. This GM mode of operation has a poorer efficiency than the Stirling mode of operation, but has the advantage that it is less expensive Compressors can be used. The same applies also for the pulse tube amplifier as well as for the series connection of both units. In Figure 1 is the combination of the thermal Power amplifier with the pulse tube cooler shown schematically.

Furthermore, an exemplary interpretation for the from the Series connection of the thermal power amplifier and with pulse tube cooler operated by him, existing periodically working Chiller described.

Since the thermal power amplifier, also called a compressor or pulse tube compressor, works like a pulse tube cooler, both systems, the power amplifier and the pulse tube cooler, can be treated with the same methods. A known calculation method [IV] provides good agreement with experiments in pulse tube coolers. A cooler is considered as a typical case, which requires a working current ("pV power") of 1000 W at the regenerator input. At a pulsation frequency of 2 Hz, a harmonically pulsating gas flow with a peak value of U _s = 4.8 l / s of the volume flow and p _s = 5.7 bar of the pressure with a phase difference of 45 ° is required. With valve-controlled operation, the pulsations are no longer harmonious. However, it was found that even with this calculation model, a design with a good approximation can be made. In the GM mode of operation, the "pV power" is provided by a compressor with approx. 6000 W electrical drive power. It works with a compression ratio of approximately 1.9 at 18 bar medium pressure. For an optimally adapted pulse tube cooler, the calculation method results in a cooling capacity of approx. 110 W at 50 K cooling temperature and 300 K ambient temperature.

Harmonic, i.e. sinusoidal pulsations of pressure and volume flow are assumed in the calculation. In the optimized system, the relationships between pressure p and volume flow U shown in the pointer / phase diagram according to FIG. 3a result at different positions, such as the regenerator inlet, RE, pulse tube inlet, PTE, and pulse tube outlet, PTA. The volume flow U _{PT, E} in the pulse tube on the side facing the compressor leads the pressure p _PT present in the pulse tube by approximately 30 °, whereas the gas flow U _{PT, A} on the opposite side lags the pressure by approximately 45 °. Similar operating conditions should arise on a pulse tube amplifier if it is designed for optimal energy conversion.

If, however, the pulse tube amplifier, 1, and the pulse tube cooler, 2, are connected in series, as is the case with the arrangement according to the invention according to FIGS. 1, 2 and 4, the phase shifts add up, as shown in FIG. 3b. In the pulse tube of the pulse tube or power amplifier, 1, both volume flow indicators U _{PT1, E} and U _{PT1, A lead} the pressure p _PT1 and in the cooler, 2, the volume flows U _{PT2, E} and U _{PT2, A lag} the pressure p _PT2 , In addition, the pointers of the pressure and volume flow oscillation at other positions are also shown in FIG. 3b. U _{R, E} thus identifies the volume flow fed into the regenerator of the amplifier at room temperature. The volume flow U _{R, A} present at the heated end of this regeneration generator is distinguished by a greater length due to the thermal expansion of the gas and by a slight rotation due to the empty volume in the regenerator. The difference between U _{R, A} and U _{PT1, E} the gas flow present at the hot end of the pulse tube comes about when the heater unit flows through. Correspondingly, the pointers p _{R, E} , P _PT1 and p _PT2 indicate the pressures at the room temperature end of the regenerator belonging to the amplifier, in the pulse tube of the amplifier unit and in the pulse tube of the cooler unit.

Both components are not in their optimal condition operated. As a result, the efficiency of the pulse tube cooler deteriorates compared to the mode of operation with direct connection on the compressor. By modifying the dimensions, this can harmful effect but reduced to the extent that a profit is achieved.

For example, one operated in a conventional manner Pulse tube cooler in GM mode with 6000 W electrical Drive power of the compressor has a cooling capacity of 110 W. 50 K can be achieved. When using a pulse tube amplifier with The compressor output is 1000 K medium temperature in the area of the heating reduced by 50%, but in addition one Heating power of 1700 W at 1000 K can be fed. So reduced the total electric drive power of 6000 W to 4700 W, 3000 W on the compressor and 1700 W on the heating.

The effect becomes even more favorable when materials with higher Temperature tolerance are used, or if the heating power is not applied electrically, but e.g. about a gas burner chamber, for example, as outlined in FIG. 5. The pipe connection between the outlet of the regenerator and the entrance to the pulse tube is heated by the gas flame. At the The pulse tube cooler connects the output of the recooler.

The practical design of a cooler with the aforementioned performance data is shown by way of example in FIG. 4. The left module in the figure represents the compressor with high and low pressure buffer tanks, HD and LP, and the alternately operated valves, solenoid or rotary valves. The middle group represents the single-stage pulse tube cooler to be operated, and the right module shows to scale the adapted power or pulse tube amplifier. Its regenerator is constructed similarly to that of the cooler, with only the pore size being adapted to the higher temperature range. A ceramic body wrapped with heating wire in a largely conventional design can be used as direct heating. The pulse tube is optimized in terms of length and diameter so that a temperature a little above ambient temperature (approx. 300 K + ΔT) occurs at the lower end, and that the phase relationship between pressure and gas flow is adapted to the requirements of the series connection. In the downstream, water-cooled heat exchanger, the heat previously supplied at high temperature is recooled to ambient temperature. A similar recooling takes place in the compressor. Therefore, the heat exchanger installed between the pulse tube amplifier and the pulse tube cooler can be constructed similarly to the plate exchanger integrated in the compressor. The linear alignment of the pulse tube power amplifier in Figure 4 is based on practical considerations. Pulse tube amplifiers and coolers are shown on the same scale. The main dimensions and operating parameters are summarized in Table 1. Parameters of a pulse tube amplifier ◆ frequency (Hz) ◆ 2 ◆ pressure (bar) ◆ ◆ min ◆ 12.4 ◆ Max ◆ 23.6 ◆ Mean Mass flow (g / s) ◆ ◆ 5 ◆ regenerator ◆ ◆ length (mm) ◆ 140 ◆ diameter (mm) ◆ 60 ◆ heating ◆ ◆ length (mm) ◆ 140 ◆ diameter (mm) ◆ 60 ◆ pulse tube ◆ ◆ length (mm) ◆ 600 ◆ diameter (mm) ◆ 60

The regenerator consists of stacked 100 mesh SS, 62 mm Diameter, 2 mm thick. This is followed by the heat exchanger in the form of a heater that needs 1700 W and generates 1000 K. It has an inner diameter of 55.2 mm and is 140 mm long. The white space is 50%. The pulse tube with the above dimensions closes itself. It has a wall thickness of 2 mm and is made of high-temperature steel 1.4961. A flow straightener is located at the pulse tube exit from a 200 mesh SS, about 15 mm thick. The stoker is covered with a first radiation shield. Another one encased this, about a third of the regenerator and about one Third of the pulse tube.

If other heating energies are to be used for the heater, the heat must be from outside the gas compartment Burner chamber or a collector room for solar heating to the Working gas are transferred. The problem is the same Way with Stirling engines. The solutions developed for this, at which working temperatures are currently up to about 1000 K. can be implemented with minor modifications become. In analogy to this, the pulse tube amplifier according to the schematic representation of Figure 5 with a gas or oil burner operate. The U-shaped arrangement of Regenerator and pulse tube proved to be advantageous. The warmer Gas from the regenerator and the pulse tube are at the top, Natural convection heat cannot flow away.

literature

IS Wild: Investigation of single and multi-stage pulse tube coolers , progress reports VDI, row 19, No. 105, VDI-Verlag Düsseldorf 1997, ISBN 3-18-310519-5

II. J.Blaurock, R.Hackenberger, P.Seidel, and M. Thürk. Compact Four-Valve Pulse Tube Refrigerator in Coaxial Configuration. Proc. 8 ^th int. Cryocooler Conf, Vail (USA) 1994, p. ...

III. Wang, G. Thummes, and C. Heiden: Experimental Study of Staging Method for Two-Stage Pulse Tube Refrigerators for Liquid Helium Temperatures , Cryogenics Vol. 37 (1997), p. 159-164

IV. Hofmann and S. Wild: Analysis of o two-stage pulse tube cooler by modeling with thermoacoustic theory . Proc. 10 ^th Int. Cryocooler Conf., May 26-28, 1998, Monterey, Ca. (UNITED STATES)

VH Carlson: 10 kW Hermetic Stirling Engine for Stationary Application, 6 ^th International Stirling Engine Conference, Eindhoven (NL), May 26-28, 1993 (Paper ISEC-93086)

Claims (7)

1. A periodically operating refrigerating machine, comprising:

   a thermal power amplifier based on the pulse tube process and

   a pulse tube cooler, which is connected in series to a heat exchanger of said thermal power amplifier operating as a cooler, wherein the thermal power amplifier comprises:

   a compressor device (K),

   a first heat exchanger (WÜ1), which releases heat to the environment, a regenerator (R1),

   a second heat exchanger (WÜ2), which introduces heat into the power amplifier, the heater,

   a pulse tube (PR1),

   a third heat exchanger (WÜ3), which releases heat to the environment, to which the pulse tube cooler is connected,

   said pulse tube cooler consisting of

   a regenerator (R2),

   a heat exchanger (WÜ4),

   a pulse tube (PR2),

   a heat exchanger (WÜ5) and

   an expander (E).
2. A periodically operating refrigerating machine according to claim 1, characterised in that the refrigerating machine is the Stirling-type machine, which, in the form of a compressor device (K), has a compressor piston and, in the form of an expander device (E), has an expander piston - double piston construction.
3. A periodically operating refrigerating machine according to claim 1, characterised in that the refrigerating machine is a Stirling type machine, which, in the form of a compressor device (K), has a compressor piston - single-piston construction - and, in the form of an expander, has a double inlet phase shifter in the form of a pipe connection with a variable cross-section from the heat exchanger (WÜ3) to the heat exchanger (WÜ5) and a pipe connection with a variable cross-section from the heat exchanger (WÜ5) to an expansion container.
4. A periodically operating refrigerating machine according to claim 1, characterised in that the refrigerating machine is the Gifford-McMahon type machine, the GM type machine, which, in the form of a compressor device (K), has respectively a valve-controlled supply line from a high pressure reservoir (HD) and a low pressure reservoir (ND) - double valve arrangement - and, in the form of an expander, has a double inlet phase shifter in the form of a pipe connection with a variable cross-section from the heat exchanger (WÜ3) to the heat exchanger (WÜ5) and a pipe connection with a variable cross-section from the heat exchanger (WÜ5) to an expansion container.
5. A periodically operating refrigerating machine according to claim 1, characterised in that the refrigerating machine is the Gifford-McMahon type machine, a GM type machine, which, in the form of a compressor device (K), has respectively a valve-controlled supply line from a high pressure reservoir (HD) and a low pressure reservoir (ND) and, in the form of an expander, also has respectively a valve-controlled supply line to the high pressure reservoir (HD) and a low pressure reservoir (ND) - four valve arrangement.
6. A periodically operating refrigerating machine according to one of claims 1 to 5, characterised in that the heat source for the heater is installed directly in the heat exchanger (WÜ2), the heater.
7. A periodically operating refrigerating machine according to one of claims 1 to 5, characterised in that the heat source for the heater is disposed externally of that of the power amplifier and is connected to the heat exchanger (WÜ2), the heater, so as to conduct heat well.

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