WO1988007654A1

WO1988007654A1 - Apparatus for recovering refrigerant, in particular from a refrigeration system

Info

Publication number: WO1988007654A1
Application number: PCT/EP1988/000232
Authority: WO
Inventors: Kurt Sorschak; Günter Pöschl
Original assignee: Kurt Sorschak
Priority date: 1987-03-25
Filing date: 1988-03-22
Publication date: 1988-10-06
Also published as: DE3709737C2; DE3709737A1

Abstract

The apparatus (10) consists of a positive type compressor (36) which is driven by a motor (42) and to which refrigerant to be recovered is supplied via a centrifugal separator (24) into which an evaporator (23) and a heat exchanger (25) are integrated. In the housing wall (13) of the centrifugal separator (24) a passage (50) of the heat exchanger (25) is disposed helically and is traversed by refrigerant from the positive type compressor (36), said refrigerant giving up its heat to the refrigerant entering via a connecting point (52) before reaching in liquefied form, possibly via a condenser (44), a collecting bottle (68). Foreign constituents such as oil, water and acid are centrifuged out of the refrigerant and corresponding to their densities separately extracted by means of diaphragm pumps from grooves which are disposed helically at the inner side of the housing wall (13). The apparatus is able not only to rapidly extract refrigerant from a refrigeration system and simultaneously process said refrigerant but also to fill a refrigeration system rapidly with refrigerant.

Description

Apparatus for recovering refrigerant, in particular from a refrigeration system

The invention relates to an apparatus of the type set forth in the preamble of claim 1.

When a defect occurs in a refrigeration system, making solde ing or welding necessary, the refrigerant must first be re¬ moved because fluorinated hydrocarbons, which are usually employed as refrigerant, can only be heated to a certain temperature because they otherwise become highly toxic. The refrigerant cannot simply be discharged into the atmos¬ phere because this would be very harmful to the environment. For fluorinated hydrocarbons damage the ozone layer of the earth. Conseguently, refrigerant recovery apparatuses have already been developed. These are constructed in the manner of a second refrigeration system and in addition so designed that the recovered refrigerant can be simultaneously puri¬ fied, for which purpose usually filters and driers are provided.

Such a known refrigerant recovery apparatus (US patent 3,699,7 removes moisture, chlorides, oil and sludge residues from recovered re¬ frigerant so that said refrigerant is returned to its original purity state. For this purpose this known apparatus comprises an oil separator, a drier and a filter. To enable the re¬ covered refrigerant to be liquefied it must be brought to a higher pressure and the heat of the refrigerant must be dissipated. The compressor is therefore followed by a coole as condenser/ and at the inlet of the apparatus a heating element is provided which causes the liquid refrigerant to vaporize since only gaseous refrigerant can be sucked in by the compressor and brought to a higher temperature. The known apparatus is complicated, requires a lot of space and is expensive to maintain. The use of filters is disadvan¬ tageous because they must be cleaned or replaced and there is a danger of refrigerant getting into the atmosphere.

A further known apparatus (DE 3 001 224 A1) , which corres¬ ponds to the apparatus set forth in the preamble of claim 1, differs from the aforementioned known apparatus in that the heat exchanger and the evaporator are arranged in series and connected together by common heat exchange ribs and a surrounding air flow generated by a fan is first conducted via the heat exchanger and then via the evaporator. This gives a certain reduction of the space requirement and makes the supply of electrical power for evaporating the refriger¬ ant superfluous. However, otherwise this known apparatus has the same disadvantages as the known apparatus mentioned above. It must also employ in the drier a desiccant which binds the moisture and like the filter must be renewed from time to time. Furthermore, the oil separator employed is as usual not able to separate the oil completely. The re¬ covered refrigerant can also not be reprocessed properly because mechanical means such as molecular screens, molecu¬ lar filters and the like must be employed and these are necessarily subjected to restrictions in their efficacy.

Admittedly, a refrigeration system is already known having a centrifugal separator (US patent 4,509,341) which is also suitable for separating liquid refrigerant components; how¬ ever, it cannot separate any impurities from the inspired refrigerant in order to make filters, driers and oil separ¬ atorssuperfluous.

The problem underlying the invention is to construct an apparatus of the type set forh in the preamble of claim 1 as a compact constructional unit with which impurities can be separated from the inspired refrigerant so that filters, ? driers and oil separatorsare superfluous.

This problem is solved according to the invention by the features set forth in the characterizing clause of claim 1.

Due to the fact that in the apparatus of the invention the evaporator and heat exchanger are integrated in a centrifuga separator, filters,driersand oil separatorsare made super¬ fluous because undesired components such as solids, moisture oil and acids are removed simply by centrifugal separation from the inspired and gasified refrigerant. The refriger¬ ant, which reaches the centrifugal separator in the liquid state, is atomized as soon as it strikes the turnine wheel. The turbine thus acts as a sort of gasifier or atomizer which breaks the liquid refrigerant down into extremely fine droplets without heat having to be supplied. The "gasifi¬ cation" of the refrigerant thus occurs purely mechanically, at least at the beginning. As soon as the operation has started and the positive type compressor furnishes hot re¬ frigerant gas passing through the heat exchanger in the housing wall additional heat is supplied to the evaporator and leads to thermal evaporation of the atomized liquid re¬ frigerant. The separation of the undesired constituents from the refrigerant then takes place in the apparatus according to the invention by gradient separation or specif¬ ic gravity separation as known per se in medicine in the separation of blood plasma. The undesired constituents are separated in grooves corresponding to their specific weight (firstly oil and solids, then water and acids). The solids, for example metallic particles, are deposited in the initial grooves and then withdrawn with the oil.

Advantageous further developments of the invention are set forth in the subsidiary claims.

In the further development of the invention according to claim 2 the withdrawal is simply by diaphragm μu ps which V are actuated by the pressure difference between the intake and pressure side of the positive type compressor, i.e. similar to a petrol pump in a motor vehicle.

An example of embodiment of the invention will be described in detail hereinafter with reference to the drawings.

The single Figure of the drawing shows in a partial longi¬ tudinal section a preferred embodiment of the apparatus according to the invention for recovering refrigerant from a refrigeration system.

The apparatus denoted as a whole with the reference numeral 10 comprises a three-part housing which consists of a one- piece turbine housing 12 and connected thereto a compressor and motor housing 14 divided into two parts in the longi¬ tudinal direction. The compressor and motor housing 14 is provided at the bottom with two feet 16 and at the top with a hand grip 18. The two halves of the compressor and motor housing 14 are connected together by screws, not illustrated, and then connected by screws, likewise not illustrated, at an annular flange 20 to a likewise annular flange 22 of the turbine housing.

The turbine housing 12 is part of a centrifugal separator 24 which is constructed as separator turbine and which is described in detail below. The compressor and motor housing 14 contains a bearing support 26 with a radial bearing 28 for mounting a shaft 30 of a positive type compressor, said shaft carrying at the one end a turbine wheel 32 and at the other end a rotor 34 of the positive type compressor which is mounted with its housing 38 in the compressor and motor housing 14. On the opposite side of the rotor 34 on the shaft 30 a coupling 40 is disposed via which the shaft 30 is connected to the output shaft (not shown) of an electric motor 42 which forms the drive motor of the apparatus. On r the side of the motor 42 opposite the coupling 40 there is a condenser 44 which is mounted in a manner not illustrated on the compressor and motor housing 14 and blown with air by a fan 46 which as illustrated is the fan of the electric motor 42 or may be a separate fan driven by the electric motor 42. The compressor and motor housing 14 may contain further bearings similar to the radial bearing 28 but these have not been illustrated because they are not essential to the invention. The shaft 30 is introduced in sealing manner into the housing 38, as illustrated by a 0 ring seal 48.

The centrifugal separator 24 comprises a passage 50 which is part of a heat exchanger 25 integrated in the housing wall 13 of the centrifugal separator. The passage 50 is arranged helically in the housing wall 13. The turbine housing 12 is provided on the intake side with a connection point 52 via which the apparatus 10 can be connected by means of a hose, a conduit or the like to a refrigeration system which is not illustrated and the refrigerant of which is to be recovered. On the pressure side the turbine hous¬ ing 12 merges into a spiral screw 54, of which as illustrate one half is integrally formed on the turbine housing 12 and the other half on the compressor and motor housing 14. The division plane of the spiral screw 54 forms the connecting plane of the flanges 20 and 22. An inlet 56 of the passage 50 is connected by a conduit 58 to the pressure side of the positive type compressor 36. An outlet 60 of the pass¬ age 50 is connected to a collecting bottle 68 via a conduit 62 in which the condenser 44 and two shutoff valves 64 and 66 are arranged. An outlet 70 of the spiral screw 54 is connected via a conduit 72 to the suction side of the po¬ sitive type compressor 36. The shutoff valve 64 prevents refrigerant from escaping from the conduit 62 during trans¬ port of the apparatus 10. The shutoff valve 66 prevents refrigerant escaping from the portion of the conduit 62 disposed between said valve and the shutoff valve 64 when the collecting bottle 68 is disconnected from the conduit 62.

The turbine housing 12 as a whole is made conical or dome- shaped, as illustrated, and its housing wall 13 carries oute ribs 15 for heat dissipation. The turbine housing 12 is preferably a cast housing which can be made for example by precision casting; the passage 50 can be made with the aid of the lost wax process. Due to the helical configuration of the passage 50 the outlet 60 thereof should in fact lie in the vicinity of the connection point 52 but in the exampl of embodiment illustrated for simplicity it has been assumed that the convolutions of the passage 50 are short-circuited at the bottom by a connecting passage which is not illustrat The interior of the centrifugal separator 24 forms an evapor ator which is denoted as a whole by 23 and in which the heat exchanger 25 traversed by hot refrigerant from the po¬ sitive type compressor 36 gives up heat to refrigerant sucke in via the connection point 52. The centrifugal separator 24 is therefore constructed at the same time as a sort of recuperator

For separating components such as solids, oil, water, acid, etc., from the sucked-in refrigerant the turbine wheel 32 and the inner side of the housing wall 13 have a particular surface configuration and as will be explained in detail hereinafter diaphragm pumps 74 are connected via suction conduits 76, 78 to the turbine housing 12. Although in the example of embodiment illustrated the conduits 62, 76, 78 are illustrated as conduits located partially outside the turbine housing 12 and the compressor and motor housing 14, it is clear that these conduits, in practice largely inte¬ grated into the housing, will be similar to the conduits 58, 72 (i.e. bores, cast-in passages or the like). 1-

The housing wall 13 is provided at the inner side with a plurality of helically rising grooves 11a, lib, etc., which are arranged in series in the direction of flow and to the end turns of which the suction conduits 76 and 78 respect¬ ively are connected, said conduits being connected at the other end to diaphragm pumps 74a and 74b respectively. The diaphragm pumps 74 are each connected via conduits 75 to th conduits 72 on the suction side of the positive type com¬ pressor 36 and via a conduit 77 to the conduit 58 on the pressure side of the positive type compressor, as is indi¬ cated in dashed line only for the diaphragm, pump 74a. The diaphragm pumps 74 are thus actuated as usual by a press¬ ure difference which in the present case is the pressure difference between the suction and pressure sides of the positive type compressor 36.

The turbine wheel 32 is made substantially conically taper¬ ing in the direction towards the connection point 52 and comprises two regions 32a, 32b with differently formed surf The first surface region 32a comprises grooves 80 (indicate in dot-dash line). The second surface region 32b is simply roughened. The generatrices of the turbine wheel 32 have however in this second surface region 32b a parabolic or hyperbolic path. The turbine wheel surface can also be mad stepped.

The apparatus 10 operates as follows:

Via a hose or the like a connection of the connecting point 52 is established with the refrigeration system from which refrigerant is to be recovered and behind said connection point 52 the turbine wheel 32 is disposed. The turbine wheel 32 rotates in operation at very high speed (e.g. 6000 to 8000 rp ). The refrigerant, which may be liquid and/or gaseous, sucked in via the connecting point 52 by the positive type compressor 36 is pressed onto the inner side of the housing wall 13. In the region of the centri¬ fugal separator 24 adjacent the first surface region 32a oil and metallic constituents contained in the refrigerant are separated, i.e. all constituents having the greatest diameter. In the second surface region 32b therebehind, in which the turbine wheel 32 has conically extending gener¬ atrices and a roughened surface, water, acid, etc., are separated. To bring the constituents to be centrifuged out onto another radius, to enable them to be thrown off, ele¬ vations must be provided on the turbine wheel surface; a surface roughening in the second surface region 32b suffices for this purpose. The refrigerant is completely vaporized in the evaporator 23 by the kinetic energy which is trans¬ mitted to said refrigerant by the rotating turbine wheel 32 and by the heat from the heat exchanger 25. Said refriger¬ ant then enters the spiral screw 54 in gaseous form and is sucked from said screw by the positive type compressor 36. The positive type compressor used here operates by the dis¬ placement principle, which means that it is a compressor which has no valves and can thus take up liquid refrigerant without being damaged.

The positive type compressor 36 forces the refrigerant sucked in from the spiral screw 54 out on the pressure side through the conduit 58 into the passage 50 of the heat exchanger 25. The refrigerant flows through the passage 50 formed like a tube coil and thereby gives its heat up to the refrigerant in the evaporator 23 which is sucked by the turbine via the connecting point 52 into the evaporator. When the apparatus 10 is switched on no heat is yet present which could be given up to the incoming refrigerant in the evaporator 23. Thus, at the start a refrigerant mist is present which is generated by the turbine. When the refrigerant is then compressed by the positive type compressor 36 the operation builds up so that finally in the evaporator 23 heat is supplied to the incoming refrigerant. The complete gasifi¬ cation or vaporization thereof is then effected by this heat supply and by the kinetic energy supplied.

Finally, the refrigerant passes via the condenser 44 and in liquid form into the collecting bottle 68. In the example of embodiment illustrated the fan 46 supplies the condenser 44 with air. The condenser 44 may be necessary for after- liquefaction should complete liquefaction of the refrigerant not occur in the turbine housing 12.. Although in this case the fan 46 blows heated air via the condenser 44 the refrige ant contained in the condenser is still far hotter than the air blown via the condenser (otherwise the motor 42 would be incorrectly designed).

The apparatus 10 can be used not only to recover refrigerant from a refrigeration system but also to fill a refrigeration system with refrigerant. The problem when filling a refrige ation system with refrigerant is that the filling operation is very tedious because liquid refrigerant must not under any circumstances reach the conventional refrigeration syste because otherwise the refrigerant compressor could be damage

Instead of the usual direct connection of a collecting bottl to the refrigeration system to be filled the collecting bottle is connected via the apparatus 10 described herein to the system and the refrigerant is pumped by means of the apparatus into the system. All that need be done to do this is reverse the direction of rotation of the motor 42 so that the apparatus 10 can suck refrigerant out of the col¬ lecting bottle 68. The apparatus 10 can readily suck in liquid refrigerant because via the connecting point 52, now functioning as outlet, it is certain that atomized and finally gaseous refrigerant is delivered to the refrigeratio system to be filled. l o

Although the apparatus 10 has been described in conjunction with a refrigeration system it can also be used with other thermodynamic cyclic processes, for example with a heat pump.

The term "refrigerant" used in the description and claims is intended to cover all fluids necessary for a thermodynami cyclic process, for example ammonia, helium, oxygen or in general all gases which can be liquefied.

Claims

C l a i m s

1. Apparatus for recovering refrigerant, in particular fro a refrigeration system, comprising a positive type com¬ pressor (36) driven by a motor (42), a collecting bottle (68) for the recovered refrigerant and an evaporator (23) which precedes the positive type compressor (36) and to which heat is supplied with the aid of a heat exchanger (25) following the positive type compressor (36), character ized in that the evaporator (23) and the following heat ex¬ changer (25) are integrated into a centrifugal separator (24), that the centrifugal separator (24) has a connecting point (52) for the refrigerant to be sucked off and is con¬ nected via a spiral screw (54) to the positive type com¬ pressor (36), that in the centrifugal separator (24) a turb wheel (32) driven by the motor (42) is provided, that in a housing wall (13) of the centrifugal separator (24) a pass¬ age (50) of the following heat exchanger (25) extends, the positive type compressor (36) being connected on the press¬ ure side to the inlet (56) of the passage (50.) and the outlet (60) of the passage (50) being connected to a con¬ duit (62) leading to the collecting bottle (68), that the turbine wheel (32) tapers substantially conically in the direction towards the connecting point (52), that a first surface region (32a) of the turbine wheel facing the connec ing point (52) has grooves (80) and that a second surface region (32b) following in the flow direction of the refriger ant is roughened, that the grooves (80) have a helical form, that the generatrices of the turbine wheel (32) in the second surface region (32b) have a conical path and that the housing wall (13) is provided at the inner side with a plurality of helically rising further grooves (11a, lib) which are arranged in series in the flow direction and to the end convolution of each of which a suction conduit (76, 78) is connected.

2 . Apparatus according to claim 1, characterized in that the suction lines (76, 78) are each connected to a diaphragm pump (74a, 74b) which is actuable by the pressure difference between the suction and pressure sides of the positive type compressor (36).

3. Apparatus according to claim 1 or 2, characterized in that the passage (50) is disposed helically in the housing wall (13).

4. Apparatus according to any one of claims 1 to 3, charact ized in that the turbine wheel (32) is arranged on a shaft (30) of the positive type compressor (36), said shaft being coupled to the motor (42).

5. Apparatus according to claim 1-, characterized in that the surface of the turbine wheel (32) is made stepped.