EP0216889A1

EP0216889A1 - Heat pump

Info

Publication number: EP0216889A1
Application number: EP19860902526
Authority: EP
Inventors: Johan P. Haga
Original assignee: Kongsberg Vapenfabrikk AS
Current assignee: Kongsberg Gruppen ASA
Priority date: 1985-04-16
Filing date: 1986-04-08
Publication date: 1987-04-08
Also published as: WO1986006156A1; AU5692586A

Abstract

Une pompe à chaleur comprend un évaporateur (1) en forme de tambour à rotation rapide et un condenseur (2) en forme de tambour qui est combiné à l'extrémité avec le tambour de l'évaporateur à une unité à tambour ayant une chambre annulaire intermédiaire (6) ayant un diamètre plus grand que le tambour de l'évaporateur (1) et le tambour du condensateur (2), et étant adapté pour contenir un réservoir annulaire de condensat (11). Une roue de pompe (12) pour un compresseur annulaire de liquide s'étend dans l'anneau de condensat (11) et sert à la fois de séparation pour maintenir séparés les gaz (vapeurs) dans l'évaporateur (1) et le condenseur (2), respectivement, et de compresseur de manière à comprimer un milieu de travail en forme de vapeur issu de l'évaporateur (1) et fournir ce milieu au condenseur (2). La chambre annulaire (6) sert en même temps de passage de retour du condensat depuis le condenseur (2) dans l'évaporateur (1) et forme un joint liquide entre le condenseur et l'évaporateur pour résister au différentiel de pression existant, ce qui est possible, à cause de la rotation rapide de la pompe à liquide et le poids spécifique élevé du condensat dans l'anneau de liquide.A heat pump comprises a rapidly rotating drum-shaped evaporator (1) and a drum-shaped condenser (2) which is combined at the end with the evaporator drum with a drum unit having an annular chamber intermediate (6) having a larger diameter than the evaporator drum (1) and the condenser drum (2), and being adapted to contain an annular condensate tank (11). A pump impeller (12) for an annular liquid compressor extends into the condensate ring (11) and serves both as a separation to keep the gases (vapors) in the evaporator (1) and the condenser separate (2), respectively, and of a compressor so as to compress a working medium in the form of vapor coming from the evaporator (1) and supply this medium to the condenser (2). The annular chamber (6) serves at the same time to return the condensate from the condenser (2) into the evaporator (1) and forms a liquid seal between the condenser and the evaporator to resist the existing pressure differential, this which is possible, due to the rapid rotation of the liquid pump and the high specific gravity of the condensate in the liquid ring.

Description

Heat Pump

The invention relates to a closed working medium loop heat pump for transporting heat from one air stream to another, comprising a drum-shaped evaporator having exterior ribs and arranged for rotation in one of the air streams to evaporate the working medium, a likewise drum-shaped condenser having exterior ribs and being coaxial with the evaporator drum for rotation therewith in the second air stream to condense the working medium, a compressor provided in the heat pump for compressing the vapourized working medium in the evaporator and transmitting it to the condenser, and a return passage for condensate from the condenser to the evaporator.

The object of the invention is to improve the previously known heat pumps by giving them a simplified design which reduces the production costs and the maintenance costs, while at the same time providing for a sufficient heat exchange between the air streams to be cooled and heated, respectively, on one side and the evaporator and the condenser, respectively, of the heat pump, on the other side.

The heat pump according to the invention is characterized in that the condenser drum and the evaporator drum are combined endwise into a drum unit having an intermediate ring chamber rotating together with the drum and constituting the return passage for condensate, said ring chamber having a larger diameter than both the evaporator drum and the condenser drum and being adapted to contain an annular reservoir for condensate, a partition between the evaporator and the condenser extending into the ring of condensate to keep apart the gases (vapours) in the evaporator and the condenser, respectively.

If the rotational speed of the drum unit and thereby of the ring of condensate is sufficiently high, sufficiently high centrifugal forces may be created for a difference in the level of the liquid of relatively few centimeters of the ring of condensate to seal against the required pressure differential between the evaporator and the condenser. Thus, if the pressure in the condenser is for instance 1.73 ata at a condensation temperature of +39ºC and the pressure in the evaporator is about 0.094 ata at an evaporating temperature of -30º, the pressure ratio will be 1.73 : 0.094 = 18.4, whereas the pressure differential is only about 1.64 ata. When using Freon 11 as a working medium and a rotational speed of 750 r.p.m. the pressure differential between the evaporator and the condenser may be taken up by a difference in level in the ring of condensate of about 4 cm when the diameter is about 850 mm. For transporting the condensate liquid from the annular chamber to the surfaces of the evaporator on which the condensate is again to be evaporated, a pitot tube can be used according to the invention.

The compressor incorporated in the heat pump can be of a number of different designs. Thus, a high speed multiple stage centrifugal compressor can be used. However, in connection with the ring of condensate present in the annular chamber according to the invention the partition extending into the condensate ring can preferably constitute a pump wheel for a liquid ring compressor. This liquid ring compressor differs from ordinary liquid ring compressors by the fact that the compressor housing is also rotating, preferably at the same rotational speed as the pump wheel.

A liquid ring compressor can usually co-operate with stationary inlet and outlet ports positioned in control discs as long as the pressure ratio is below about 7. If the pressure ratio is higher than 7, a valve system must usually be provided in the pressure port. However, according to the present invention a rotating siphon can be provided on the pressure side. This siphon also functions as a check valve and prevents gas from flowing back from the condenser into the liquid ring chambers during the suction phase.

The use of a liquid ring compressor has hitherto not been regarded as feasible when the gas to be compressed is the same medium as the condensate used in the liquid ring, since in this case undesired evaporation will occur in the liquid ring chamber. However, according to the present invention it is possible to use a liquid ring which in addition to a working medium consists of a liquid having a lower specific gravity. For example, the working medium can consist of Freon 11 and the other liquid of ethylene glycol. Due to the difference in the specific gravity the working medium will take up the outer part of the liquid ring, whereas the ethylene glycol will be present at the inner side of the liquid ring, thereby forming the surface of the liquid ring which constitutes a boundary of the compressor chambers.

Further features and advantages of the present invention will appear from the following description of an embodiment of a heat pump having a liquid ring compressor.

Fig. 1 is longitudinal view through a heat pump according to the invention.

Fig. 2 is a section along the line II-II in Fig.

1.

Fig. 3 is a section through a part of one of the drum shells and illustrates a stationary comb-shaped device for increasing the air exchange around the drum.

Fig. 4 illustrates an embodiment having a centrifugal compressor instead of a liquid ring compressor.

Fig. 5 illustrates an embodiment of a heat pump according to the invention installed in a housing.

The heat pump illustrated in the drawing consists of an evaporator drum 1 and a condenser drum 2 which are interconnected to form a drum unit by means of flanges 3, 4 which are bolted together. The flange 3 is formed on an enlarged wall portion 5 forming an annular chamber 6 of larger diameter than both the evaporator drum 1 and the condenser drum 2.

The drum shells of the evaporator 1 as well as the condenser 2 are slightly conical, the end having the larger diameter facing the annular chamber. However, the drums can also taper in the opposite direction, and in this case a radially enlarged annular sink 6' (see Fig. 4) which communicates with the annular chamber for transfer of liquid therebetween, can be provided at the end of the evaporator drum 1 and/or the condenser drum 2 opposite the annular chamber 6. The two drum shells carry exterior ribs 7 in order to improve the heat transfer between the working medium inside the evaporator and the condenser, respectively, and the air stream to be cooled and heated, respectively. The heat transfer can be further enhanced by means of at least one adjustable, but non-rotatable comb-shaped device 33 extending into the space between the ribs, thereby increasing the air exchange around the drum, as shown in Fig. 3. Due to a high rotational speed of the heat pump the ribs 7 will be self-cleaning, since they will remain clean due to the centrifugal force, even when operating in air containing solid matter originating from the ventilation of an industrial process . It can furthermore be expected that ice will not form on the cooling ribs, since the centrifugal forces will hurl condensed drops away from the cooling surfaces. For these reasons and due to the high relative speed between the surrounding air and the cooling ribs higher heat transfer values between the air and the cooling ribs than what is usual in conventional air batteries will be obtained.

The drum unit is mounted on journals 8, 9 and intended for operation by means of a motor which is not illustrated. The journal 8 is not directly connected to the evaporator 1, but instead secured to a bell-shaped end cover 10 which is bolted to the end of the evaporator 1.

The combined shells 1, 2 are filled with a closely metered amount of a working medium, such as Freon 11, and a likewise closely measured, smaller amount of ethylene glycol. During rotation of the heat pump the working medium and the ethylene glycol form a liquid ring 11 rotating together with the annular chamber 6. Because of the difference in specific gravity between the working medium and the ethylene glycol the liquid working medium will take up a position at the outer side of the liquid ring 11, whereas the ethylene glycol will form a layer on the inner side of the liquid ring. In order to separate the gas volumes in the evaporator 1 and the condenser 2, respectively, a pump wheel 2 has been provided, which extends into the condensate ring 11. The pump wheel 12 consists of two end discs 13, 14, an annular wall 15 connecting the end discs 13, 14, and a suitable number, such as eight, radial partitions 16 which divide the portion of the pump wheel between the end discs 13 and 14 and radially outside the annular wall 15 into a corresponding number of outwardly open pumping chambers 17. Each chamber 17 has a suction port 18 in the end disc 13 for admitting vapours or gases from the evaporator 1 and a discharge port 19 for compressed working medium in the end disc 14.

In connection with the suction port 18 inlet passages 20 formed by baffles 21 are formed. Each discharge port 19 is connected to a discharge passage 22 formed by two baffles 23, 24 arranged so as to form a siphon during rotation. This siphon is dimensioned to provide an opening pressure slightly larger than the pressure in the condenser 2. Such a siphon replaces a valve system having movable parts and also functions as a check valve preventing gas from flowing from the condenser 2 back into the liquid ring chambers 17 during the suction phase.

The pump wheel 12 is mounted on an eccentric journal 25' carried by a shaft 25 which is concentric with the drum unit 1, 2 and mounted in the evaporator 1. The end of the shaft 25 extends through the end wall 26 of the evaporator 1 and into the chamber formed by the cover 10. In this chamber the shaft 25 carries a laminated wheel 27 which is kept stationary by a magnet 28 outside the cover 10, so that the shaft 25 will not rotate. The laminated wheel 27 and the magnet 28 are associated with the evaporator 1, since the lower pressure therein provides better conditions for the magnetic lines of force than the condenser 2. The pump wheel 12 rotates on-the stationary eccentric journal 25' due to the fact that the pump wheel 12 is coupled to the annular chamber portion 6 of the drum unit by means of a linkage 29. Thereby, the pump wheel 12 will rotate with the same speed as the evaporator 1 and the condenser 2, while at the same time performing an approximately radial, cyclic, reciprocating movement with respect to the annular chamber 6 and thereby the liquid ring 11. Thus, each of the working chambers 17 in the pump wheel 12 will perform a cyclic movement with respect to the liquid ring 11 , whereby the volume of the working chambers 17 is varied.

On the side opposite to the eccentric journal 25' the shaft 25 carries a counterweight 30 which may partly or completely balance the non-symmetric forces which may occur if the shaft 25 and thereby the eccentric journal 25' should begin to rotate together with the evaporator

I and the condenser 2.

For transporting condensate from the liquid ring

II onto the inner wall of the drum shell of the evaporator 1 , where the condensate can evaporate while absorbing heat from the air passing on the outside of the evaporator

1, there is provided a pitot tube 31. This pitot tube can be secured to the counterweight 30. Alternatively, the pitot tube can be mounted on the shaft 25 at the end of the evaporator opposite to the annular chamber 6, which is an especially suitable arrangement when the compressor is a centrifugal compressor. In this case the pitot tube can extend into the sink (not shown) referred to previously. The pitot tube can pass condensate to the narrowest end of the shell surface of the evaporator, from which it flows back to the annular chamber due to the tapering form of the shell surface. However, as shown, the condensate can also be sprayed onto the inner surface of the evaporator shell through nozzles 32. The object thereof is to prevent that a laminar liquid layer is formed on the inner wall of the evaporator drum. Although not shown in the drawing, the interior surfaces of the condenser drum can be provided with axially extending ribs. Also in this case the object is to prevent the forming of a laminar liquid layer with a radial pressure gradient. Furthermore, the ribs will extend through the layer of condensate and enhance the heat transfer by condensation of the cooling medium vapours.

The drum unit can be made by aluminium which is a good heat conductor. Since Freon 11 has a low vapour pressure, the pressure in the condenser may be kept sufficiently low for the apparatus not to require certification as a pressure vessel.

The heat pump as described operates as follows:

The working medium in the form of condensate in the liquid ring 11 is passed by means of the pitot tube 31 to the inner wall of the evaporator drum, where the working medium will evaporate while absorbing heat from air passing the cooling ribs 7 on the outer side of the evaporator 1. The evaporated working medium will be sucked in through the suction port 18 during the suction stroke in each working chamber 17 and forced out through the discharge port 19 and the siphon 22 and into the condenser 2 during the subsequent compression stroke. In the condenser the pressure can for instance be 1.73 ata at a temperature of 39°C when Freon 11 is used as a working medium. The pressure in the evaporator 1 can be about 0.094 ata at a temperature of -30°C. The pressure differential between the gas volumes in the evaporator 1 and the condenser 2 will result in the level of the liquid ring 11 facing the evaporator 1 not being flush with the level facing the condenser 2. However, the difference will only amount to a few centimeters when the liquid ring is rotating at a suitable speed.

In the condenser 2 the compressed freon vapour will condense on the shell surface while transferring heat to the air passing the condenser on the outer side thereof. Due to the tapering shape of the drum condensate will flow back to the liquid ring 11, whereby the circuit is completed. The heat pump will usually be arranged in a housing having two separate air channels. The air to be cooled is passed through the channel passing the outer side of the evaporator 1. The air to be heated is passed by the outer side of the condenser 2. In each air channel there may be provided fans, usually propeller fans. If desired, the radial cooling ribs 7 can be shaped so as to contribute to the transportation of the air past the evaporator and the condenser, respectively. A heat pump embodying this feature will be discussed later in connection with Fig. 5. The heat pump may for instance be used for heating ventilation air to a building. If this is the only use, the air channel around the evaporator 1 can be omitted and the heat taken simply from the ambient air. However, if the system is also to be used for cooling of the ventilation air, for instance in the summer, it must be possible to switch the stream of air, so that the ventilation air is passed by the evaporator 1, whereas the ambient air. (atmospheric air) is passed by the condenser 2. Such a switching can be obtained simply by reversing the propeller fans used for passing the air streams by the heat pump.

However, the heat pump can also be used for other purposes than for heating or cooling of ventilation air. Thus, the heat pump can be used for heat recuperation and dehumidification.

An aggregate incorporating a heat pump according to the invention can be adjusted with respect to its capacity in various ways. First of all, the rotational speed of the evaporator and the condenser can be changed. Further, the rotational speed of the fan passing air to the evaporator can be adjusted. Thereby the flow of heat to the aggregate is changed. A combination of the adjustment facilities referred to above is also possible. Furthermore, the magnetic force restraining the eccentric journal 25' from rotating can be reduced or removed. When the eccentre rotates together with the pump wheel, no compression is obtained. It is thus possible to achieve a stepless adjustment of the output of the compressor. These adjustment facilities permit continuous operation of the heat pump.

The preceding description of the structure relates to its operation as a heat pump. However, the structure can also function merely as a heat recuperator having a thermal efficiency of for instance 50-60%. This is obtained simply by removing the pump wheel 12.

The pitot tube 31 will still pass cooling medium condensate to the evaporator shell. Because of the exterior temperature conditions the pressure in the evaporator will adjust itself to a higher level than the pressure in the condenser, and the cooling medium vapours will pass from the evaporator to the condenser, where condensation will take place. Therefrom the condensate will flow to the annular chamber 6.

In Fig. 4 an embodiment is illustrated, in which the compressor is a centrifugal compressor 34 instead of a liquid ring compressor. The compressor is mounted partly in the partition 12' between the evaporator 1' and the condenser 2', partly on a journal 35 secured to the end wall 26' of the evaporator 1'. The compressor is operated at a high rotational speed by an hydraulic motor 36 to which hydraulic operating medium is supplied through the journal 35. Figure 4 also illustrates the provision of an annular sink 6' at the end of the evaporator shell 1 remote from the annular chamber 6, and the conduit 6" through which the annular chamber 6 communicates with the sink 6'. In this embodiment the pitot tube 31' extends into the sink 6' and is rotatably mounted on the journal 35. It is restrained against rotation by a counterweight 37. The shell unit 1', 2' is driven by a motor 38 which is positioned in a cup-shaped end cover 39 for the condenser 2' .

In Fig. 5 a heat pump according to the invention is shown to be mounted in bearings 40, 41 in an isolated housing 42. Ribs 7' on the outer side of the evaporator 1 as well as the condenser 2 are in this case helical in order to provide a pumping effect on the air streams flowing past the condenser and/or the evaporator. The housing closely surrounds the ribs 7, which transport air from both ends of the heat pump to the centre of the heat pump, where the substantially axial flows are transformed into radial flows to separate tangential outlets. Vanes 43 for producing a further transportation effect are provided on the drums at the centre portion thereof.

Other constructional features are similar to those already discussed in connection with the other Figures and are designated by similar reference numerals. Thus, the condenser drum is designated by 2", the evaporator drums by 1", the partition/pump wheel by 12", the pumping chambers by 17', the suction ports by 18', the discharge ports by 19', the pitot tube with its counterweight by 31' and 30', respectively, the spraying nozzles by 32', the rotation preventing wheel by 27', the magnet by 28', the linkage between the wheel 12" and the drums 1", 2" by 29', and the motor for rotating the combined drums 1" and 2" by 38'.

Apart from the helical ribs 7' the main difference between this embodiment and that in Fig. 1 relate to the valves in the suction ports and the discharge ports to and from the pumping chambers 17'. These valves are designed as flap valves 44, 45, the valve 45 replacing the siphon formed by the baffles 23, 24 in Fig. 1.

Claims

P a t e n t C l a i m s

1. A closed working medium loop heat pump for transporting heat from one air stream to another, comprising a drum-shaped evaporator (1) having exterior ribs (7) and arranged for rotation in one of the air streams to evaporate the working medium, a likewise drum-shaped condenser (2) having exterior ribs (7) and being coaxial with the evaporator drum for rotation therewith in the second air stream to condense the working medium, a compressor provided in the heat pump for compressing the vapourized working medium in the evaporator ( 1 ) and transmitting it to the condenser (2), and a return passage for condensate from the condenser to the evaporator, c h a r a c t e r i z e d i n that the condenser drum and the evaporator drum are combined endwise into a drum unit having an intermediate ring chamber

(6) rotating together with the drum and constituting the return passage for condensate, said ring chamber having a larger diameter than both the evaporator drum (1) and the condenser drum (2), and being adapted to contain an annular reservoir for condensate (11), a partition (12) between the evaporator (1) and the condenser (2) extending into the ring of condensate (11) to keep apart the gases (vapours) in the evaporator and the condenser, respectively.

2. Heat pump as claimed in claim 1, c h a r a c t e r i z e d i n that a radially enlarged, annular sink communicating with the annular chamber (6) is provided at the end of the evaporator and/or condenser drums opposite the annular chamber ( 6 ).

3. Heat pump as claimed in claim 1 or 2, c h a r a c t e r i z e d i n that the drum shell of the evaporator (1) is slightly conical, the end of the drum having the larger diameter facing the annular chamber (6) or a sink, if any, at the opposite end.

4. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the drum shell of the condenser (2) is slightly conical, the end of the drum having the larger diameter facing the annular chamber (6) or a sink, if any, at the opposite end.

5. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d by a pitot tube (31) extending into the condensate ring (11) formed in the annular chamber (6) or the sink, and adapted to pass condensate to the inner surface of the evaporator drum.

6. Heat pump as claimed in claim 5, c h a r a c t e r i z e d i n that the pitot tube (31) ends in the nozzle for supplying condensate to the evaporator surface.

7. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the ribs (7) on the drums are substantially radial.

8. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the ribs (7) are shaped with a view to giving a pump effect to the air which is to flow past the ribs for cooling or heating.

9. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the partition extending into the condensate ring (11) in the annular chamber (6) constitutes a pump wheel (12) for a liquid ring compressor.

10. Heat pump as claimed in claim 9, c h a r a c t e r i z e d i n that it contains ethylene glycol in addition to a working medium such as Freon 11, the condensate of which has a higher specific gravity.

11. Heat pump as claimed in claim 9 or 10, c h a r a c t e r i z e d i n that the pump wheel (12) is eccentrically mounted and connected to the drum shells or the annular chamber (6) for rotation therewith.

12. Heat pump as claimed in any of the claims 9-11, in which the pump wheel consists of two end discs (13, 14) which at all times extend into the liquid ring (11) consisting of working medium and of ethylene glycol, if applicable, and of several circumferentially spaced working chambers (17) between the end discs, suction ports (18) and discharge ports (19, 22) respectively for the working chambers (17) being provided in the end discs (13, 14).

13. Heat pump as claimed in claim 12, c h a r a c t e r i z e d i n that the discharge port (19, 22) from each chamber (17) contains a pressure valve in the form of a rotating siphon (23, 24).

14. Heat pump as claimed in claim 12 or 13, c h a r a c t e r i z e d i n that the suction port (18) to each chamber (17) has an inlet passage (20), the inlet of which is positioned radially inside of the liquid ring (11).

15. Heat pump as claimed in any of the claims 9-14, c h a r a c t e r i z e d i n that the pump wheel (12) is mounted eccentrically with respect to the condenser and the evaporator drums on a journal (25') which is rigidly connected to a centrally mounted shaft (25) which can be restrained from rotation.

16. Heat pump as claimed in claim 5 or 6 and in claim 15, c h a r a c t e r i z e d i n that the pitot tube (31) is carried by the mounting for the pump wheel (12).

17. Heat pump as claimed in claim 15, c h a r a c t e r i z e d i n that the centrally mounted shaft (25) is restrained from rotation by means of weights.

18. Heat pump as claimed in claim 15, c h a r a c t e r i z e d i n that the centrally mounted shaft (25) is restrained from rotation by a magnetic system (27, 28).

19. Heat pump as claimed in claim 18, c h a r a c t e r i z e d i n that the restraining force of the magnetic system (27, 28) is adjustable in order to vary the compressor capacity.

20. Heat pump as claimed in claim 15, c h a r a c t e r i z e d i n that the centrally mounted shaft (25) carries counterweights (30) for balancing the eccentrically mounted pump wheel (12) in case the shaft (25) should start rotating.

21. Heat pump as claimed in claim 6, c h a r a c t e r i z e d by at least one movable, but non-rotating comb-shaped device (33) extending into the space between the radial ribs.

22. Heat pump as claimed in any of the preceding claims, c h a r a c t e r i z e d by the modification that the partition (12) is omitted, whereby the structure will work as a heat recuperator.