WO2011154595A1

WO2011154595A1 - Rotor assembly and rotary heat exchanger having rotor

Info

Publication number: WO2011154595A1
Application number: PCT/FI2011/050503
Authority: WO
Inventors: Aki Rosenqvist; Jukka SETÄLÄ
Original assignee: Swegon Ilto Oy
Priority date: 2010-06-09
Filing date: 2011-05-31
Publication date: 2011-12-15
Also published as: FI20105655A0

Abstract

The invention relates to a rotor and a rotary heat exchanger in which inlet air (I) is heated to supply air (S) by using thermal energy of discharge air (D) such that the discharge air (D) is cooled to outlet air (O). The heat exchanger comprises: a rotor (1), an inlet plenum (14) for conducting inlet air (I) to the rotor (1), a supply plenum (15) for receiving supply air (S) from the rotor (1), a discharge plenum (16) for conducting discharge air (D) to the rotor (1), an outlet plenum (17) for receiving outlet air (O) from the rotor (1), a circumferential sealing unit (2, 6), a first axial sealing unit (4, 7). The sealing units (2, 6; 4, 7; 5, 0) are provided with a pressure balancing volume (8, 9) between the plenums (14, 15, 16, 17).

Description

ROTOR ASSEMBLY AND ROTARY HEAT EXCHANGER HAVING ROTOR

FIELD OF THE INVENTION

[0001 ] The present invention relates to a rotor assembly for a rotary heat exchanger and particularly to a rotor assembly according to the preamble of claim 1 , the rotor assembly comprising: a rotor arranged to rotate around a rotation axis, the rotor having a first side and a second side in the direction of the rotation axis, a circumferential sealing unit arranged around the periphery of the rotor for isolating the first side and the second side of the rotor, a first axial sealing unit on the first of the rotor for dividing the first side of the rotor to two adjacent plenums and a second axial sealing unit on the second side of the rotor for dividing the second side of the rotor to two adjacent plenums. The present invention further relates to a rotary heat exchanger and particularly to a rotary heat exchanger according to the preamble of claim 1 in which inlet air is heated to supply air by using thermal energy of discharge air such that the discharge air is cooled to outlet air, the rotary heat exchanger having a rotor unit comprising: a rotor for carrying out the heat exchange, an inlet plenum for conducting inlet air to the rotor, a supply plenum for receiving supply air from the rotor, a discharge plenum for conducting discharge air to the rotor, an outlet plenum for receiving outlet air from the rotor, a circumferential sealing unit for isolating the inlet plenum from the supply plenum and discharge plenum from the outlet plenum, a first axial sealing unit for isolating the inlet plenum from the outlet plenum and a second axial sealing unit for isolating the supply plenum from the discharge plenum.

BACKGROUND OF THE INVENTION

[0002] A rotary air-to-air heat exchanger, otherwise known as heat or enthalpy wheel is a regenerative heat exchanger where a mass made of corrugated channels rotates through airstreams. Adjacent supply and exhaust air streams each flow through half of the wheel in a counter flow direction. A rotary heat exchanger offers high efficiency heat recovery and is a common choice of heat exchanger in a ventilation unit.

[0003] A limitation of the rotary heat exchanger is cross contamination or mixing of the two air streams which occur by carryover and leakage across the seals surrounding the rotor and separating the air streams. When ventilating an area with fresh outside air it is often important to minimise the amount of extract air crossing over into the supply fresh air side since the extract air can be contaminated, for example by smells, or which can be very humid.

[0004] Leakage from one air stream to another occurs due to the static air pressure difference between the air streams which drives some air from the higher pressure stream into the lower pressure one. To ensure that there is no leakage from the extract side to the fresh air of the supply side a pressure balance damper of the prior art, is commonly used to create additional under pressure in the extract ducting to ensure that the supply ducting has the greater pressure.

[0005] The disadvantage of this prior art is either that you accept the potentially large leakage rates or that one balances the pressure by increasing pressure losses on the extract ducting side with the pressure balance damper and then accepts the increased loading and hence energy consumption and noise on the extract side fan.

BRIEF DESCRIPTION [DISCLOSURE] OF THE INVENTION

[0006] An object of the present invention thus to provide a rotor assemble and a rotary heat exchanger so as to overcome the above mentioned prior art disadvantages. The objects of the invention are achieved by a rotor assembly according to the characterizing portion of claim 1 wherein at least one of the sealing units is provided with a pressure balancing volume for balancing the pressure difference over the sealing unit. The objects of the invention are achieved by a rotary heat exchanger according to the characterizing portion of claim 1 wherein at least one of the sealing units is provided with a pressure balancing volume between the plenums.

[0007] The preferred embodiments of the invention are disclosed in the dependent claims.

[0008] The present invention uses a pressure balancing volume and an extra seal to complement the existing seals in the rotor assembly. The rotor assembly of a rotary heat exchanger functions such that inlet air is heated to supply air by using thermal energy of discharge air such that the discharge air is cooled to outlet air. In other words inlet air is heated by discharge air in the rotor assembly of the rotary heat exchanger such that the inlet air becomes heated supply air and the discharge air becomes cooled outlet air. The rotor assembly comprises an inlet plenum on the first side of the rotor for conducting inlet air to the rotor, a supply plenum on the second side of the rotor for receiving supply air from the rotor, a discharge plenum on the second side of the rotor for conducting discharge air to the rotor and an outlet plenum on the first side of the rotor for receiving outlet air from the rotor. The rotor assembly is further provided with a circumferential sealing unit for isolating the inlet plenum from the supply plenum and discharge plenum from the outlet plenum, in other words for isolating the first side of the rotor from the second side of the rotor. The rotor assembly further comprises a first axial sealing unit on the first side of the rotor for isolating the inlet plenum from the outlet plenum and a second axial sealing unit on the second side of the rotor for isolating the supply plenum from the discharge plenum. In the present invention the mentioned sealing units are provided with a pressure balancing volume for balancing the pressure difference over the sealing unit. The pressure balancing volume is provided to the sealing unit between the adjacent plenums. The sealing unit is further provided with two sealing elements provided between the pressure balancing volume and the adjacent plenums. Thus there is one sealing element between one plenum and the pressure balancing volume and another sealing element between the other plenum and the pressure balancing volume. The sealing elements are provided such that they are at least partly pressure permeable for balancing the pressure difference between the adjacent plenums in the pressure balancing volume.

[0009] The present invention has the advantage that it provides a similar function as the pressure balancing damper without the associated disadvantages since no or reduced resistance needs to be supplied to the extract ducting. Furthermore, using the pressure balancing volume of the present invention decreases or prevents the leakage problems in connection with the rotor assembly of a rotary heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

[0011] figure 1 is schematic view of a rotor assembly;

[0012] figure 2 is schematic view of prior art rotary heat exchanger; [0013] figure 3 is schematic view of another prior art rotary heat exchanger;

[0014] figure 4 is a graph showing leakage through a prior art rotary heat exchanger;

[0015] figure 5 is graph showing leakage through a prior art rotary heat exchanger having a pressure balance damper;

[0016] figure 6 is rotor assembly according to the present invention;

[0017] figure 7 shows an axial sealing unit of figure 6;

[0018] figure 8 shows a circumferential sealing unit of figure 6; and

[0019] figure 9 is a graph showing leakage through the rotary heat exchanger of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] A conventional rotor assembly for ventilation unit or rotary heat exchanger is shown in figure 1 . The rotor assembly comprises a rotor 1 , a rotor box 2, divider planes 4, 5 for isolating air streams. A first axial seal 7, also known as transverse seal, is used to isolate the air streams on first side 12 of the rotor 1 . Similar second axial seal 10 is provided on the on the second side 13 of the rotor 1 . A circumferential seal 6, also known as peripheral seal, is used to form a seal around the outside periphery 3 of the rotor 1 to reduce leakage flow via the internal of the rotor box 2 from the first side 12 of the rotor 1 to the second side 13 of the rotor 1 and vice versa. Instead of the rotor box 2 encasing the rotor, a single plane or plate surrounding the rotor periphery 3 may be used to divide the upstream, first side 12 of the rotor 1 , and downstream, second side 13 of the rotor 1 , sides of the rotor 1 . The rotor 1 has a first side surface 24 on the first side 12 of the rotor and a second side surface 25 on the second side 13 of the rotor 1 .

[0021] There are various pressure zones surrounding the rotor assembly. These pressure zones are shown in figures 2 and 3 and described below. As shown in figures 2 and 3 are shown a conventional prior art rotary heat exchanger having a rotor unit 30. The rotor unit comprises a rotor 1 , an inlet plenum 14 into which fresh outside air is conducted as inlet air I. The inlet air I is conducted to the rotor 1 in which it is heated to supply air S which is received to the supply plenum 15 from the rotor 1 . The supply air S is further conducted to a room 32 by using a supply fan 34. From the room 32 air is dis- charged as discharge air D conducted to discharge plenum 16 of the rotor unit 30. The discharge air D is conducted from the discharge plenum 16 to the rotor 1 in which it is cooled such that it transfers heat to the inlet air I. The cooled discharge air D is received to the outlet plenum 17 as outlet air O and the outlet air is extracted by using discharge fan 36.

[0022] The inlet plenum 14 and the outlet plenum 17 are on the first side 12 of the rotor 1 , and the supply plenum 15 and the discharge plenum 16 are on the second side of the rotor 1 . The inlet plenum 14 and the outlet plenum 17 as well as the supply plenum 15 and the discharge plenum 16 are isolated or separated from each other by using axial sealing units. A first axial sealing unit comprises the first axial seal 7 and the first axial divider 4 for isolating the inlet plenum 14 from the outlet plenum 17 on the first side of the rotor 1 . A second axial sealing unit comprises the second axial seal 10 and the second axial divider 5 on the second side of the rotor 1 . Furthermore, a circumferential sealing unit comprises one or two circumferential seals 6 and one or two circumferential dividers 2, as shown in figures 2 and 3.

[0023] Inlet air I is taken from the outside at the atmospheric air pressure PA. The air passes through the inlet duct and due to the pressure drop caused by the resistance of the inlet duct has a pressure P1 in the inlet plenum 14. After passing through the rotor 1 the supply air S has a reduced pressure of P2 at the supply plenum 15. From the supply plenum 15 the air is drawn through supply fan 34 and passes through the supply duct to the ventilated room 32. In the room 32 it is assumed that the pressure is that of atmospheric air pressure PA since in normal ventilation installation the pressure is close to that of atmospheric pressure PA. The discharge air D is drawn through the discharge duct and due to the duct losses has a pressure of P3 in the discharge plenum 16. The discharge air D passes through the rotor 1 and due to the resistance of the rotor 1 the outlet air O has a reduced pressure of P4 in the outlet plenum 17. From the outlet plenum 1 7 the outlet air O is drawn through the discharge fan 36 and is driven through the exhaust duct. A balance damper 38 can be placed between the extract duct and the rotor 1 in the location shown in figures 2 and 3.

[0024] When the rotor 1 is contained within a rotor box 2 then the internal pressure of the rotor box 2 PO is the average of the P1 , P2, P3 and P4 pressures when the circumferential seals 6 are of the same design, as is shown in figure 2. In the case where the rotor 1 has a single rotor wall and not a rotor box 2, as is shown in figure 3, for there is only one circumferential sealing unit having the circumferential seal 6 between the respective plenums 14, 15 and 16, 17 on the opposing sides 12, 13 of the rotor 1 . In the embodiment of figure 3 the rotor box 2 of figure 2 is replaced with circumferential divider extending around the periphery 3 of the rotor 1 . Therefore in figure 3 there is only one circumferential seal 6 that separates the pressure P1 in inlet plenum 14 and the pressure P2 in the supply plenum 15. The same applies for the discharge plenum 16 and the outlet plenum 17.

[0025] Results of calculations, which have been confirmed by testing, are shown in figure 4 for a small ventilation unit, or small rotary heat excganger, having a brush type axial seals 7, 10 and brush type circumferential seal 6 with a rotor 1 of 300mm diameter supplying a balanced ventilation supply of 40 l/s which at the example flow rate has a pressure drop through the rotor 1 , AProtor, of 80Pa. The graph of figure 4 shows the resultant axial seal 7, 10 leakage rates identified as curve "m" and circumferential seal 6 leakage rate identified as "p". At point (ii), which is assumed the nominal cases for the following examples, the resistances of the discharge ducting of discharge air D and the outlet ducting for inlet air I are the same so that P1 =P3. Since P2 = P1 minus the pressure drop of the rotor 1 AProtor then the P2 will have an under pressure against P3 equal to pressure drop of rotor 1 , from here on referred to as "AProtor" i.e. P2=P1 -AProtor. The leakage through the axial seal 7, 10 and the circumferential seal 6 are proportional to the pressure difference of AProtor. At point (i) the inlet duct resistance for inlet air I is higher than that of the discharge plenum 16 causing the P3 pressure to be increased by 80Pa so that P3-P2=0 so there is no leakage flow. Point (iii) on the diagram is where the discharge air D resistance is increased such that the P1 pressure is increased by 80Pa and the pressure difference is now P3-P2=160Pa. The curve between point i, ii and iii show a range of inlet duct pressure P1 to discharge duct pressure P3 differences.

[0026] Figure 4 is then an example of the leakages through the rotary heat exchanger seals 7, 1 0, 6 with a prior art seal arrangement with no countermeasures, such as balance damper 38, are used to improve this. Throughout the range of pressure range from points (ii) to (iii) the axial seal leakage "m" and circumferential seal leakage "p" are positive indicating that the leakage flow into supply side of the rotor, inlet plenum 14 and supply plenum 15, hence in the wrong direction since this leakage contaminates the air supplied to room 32.

[0027] This problem is partially solved in a prior art solution by using a pressure balance damper 38 to provide in increased pressure loss in the discharge, in discharge plenum 16 and outlet plenum 17, such that the P2 would be greater or equal to P3. Figure 5 shows where the pressure balance damper 38 has been adjusted to give an extra 80Pa pressure loss so that P3- P2=0 (case ii) thus the axial seal 10 and circumferential seal 6 leakages are zero at the nominal flow through the rotary heat exchanger.

[0028] In the range of pressure range from points (i) to (ii) the axial seal leakage "m" and the circumferential seal leakage "p" negative, meaning that the leakage is out of the supply plenum 15. Only between points ii) to iii) is the axial seal leakage "m" and the circumferential seal leakage "p" in towards the supply plenum 15. At point (ii) the axial seal leakage "m" and the circumferential seal leakage "p" is 0%. At point (iii) the axial seal leakage "m" and the circumferential seal leakage "p" 64% of the original leakage.

[0029] One significant disadvantage of applying the extra pressure loss at the discharge side is that the discharge fan 36 is constantly operating against the additional pressure which consumes extra energy and increases the noise emitted from the discharge fan 36. Another disadvantage is than the pressure difference across the inlet duct to outlet duct is increased so if the above example P3-P2=0Pa then P1 -P4=160Pa which would give the corresponding leakage to the discharge at point (iii) which would increase the flow rate and load on the discharge fan 36.

[0030] The present invention as shown in figures 6, 7 and 8 provides a solution with similar advantages with providing extra pressure balancing damper 36, but without the associated disadvantages.

[0031] Figure 6 shows a rotor assembly having a rotor 1 and a first axial seal 7, second axial seal 10 and a circumferential seal 6. The invention is characterised in that the seals 7, 10, 6, or at least one of them, are provided with provided a pressure balancing volume 8, 9, as shown in figures 7 and 8. The seals 7, 10, 6 form together with the axial dividers 4, 5 and the circumferential divider 2 sealing units respectively.

[0032] Figure 5 A shows a first embodiment of the second axial seal 10 of the present invention. It should be noted that the first axial seal 7 is usually identical to the second axial seal 10 and thus it is not shown. The second axial seal 10 comprises a wall portion 26 which together with the second axial divider 5 forms a pressure balancing volume 8. The first and second axial seals 7, 10 are provided respectively in connection with the first and second side surfaces 24, 25 of the rotor 1 , as shown in figure 6, for sealing the gap between the dividers 4, 5 and the side surfaces 24, 25 of the rotor 1 . The second axial seal 10 is provided with two sealing elements 22, 23 provided between the pressure balancing volume 8 and the adjacent plenums 15, 16. The first axial seal 7 respectively with two sealing elements between the between the pressure balancing volume 8 and the adjacent plenums 14, 17. Therefore the second axial seal 10 comprises a first axial sealing element 22 between an axial pressure balancing volume 8 and supply plenum 14 and a second axial sealing element 23 between an axial pressure balancing volume 8 and the discharge plenum 16.

[0033] The circumferential seal 6 comprises a wall portion 27 which together with the circumferential divider 2 forms a circumferential pressure balancing volume 9. The circumferential seal 6 is provided in connection with the periphery 3 of the rotor 1 or the outside edge of first or second side surface 24, 25 of the rotor 1 , as shown in figure 8, for sealing the gap between the circumferential divider 2 and the periphery 3 and/or side surfaces 24, 25 of the rotor 1 . The circumferential seal 6 comprises a first circumferential sealing element 20 between a circumferential pressure balancing volume 9 and the first side 12 of the rotor 1 and a second circumferential sealing element 21 between a circumferential pressure balancing volume 9 and the second side 13 of the rotor 1 . Thus the first circumferential sealing element 20 is between the circumferential pressure balancing volume 9 and the inlet plenum 14 or the outlet plenum 17, and the second circumferential sealing element 21 is between the circumferential pressure balancing volume 9 and the supply plenum 15 or the discharge plenum 17.

[0034] Figures 7A, 7B, 7C, 8A, 8B and 8C show different kinds of embodiments of the pressure balancing volume 8, 9 and the sealing elements 20, 21 , 22, 23. The sealing elements 20, 21 , 22, 23 are arranged to be pressure permeable such that allow the pressure of the adjacent plenums 14, 15, 16, 17 to balance. Thus the sealing elements 20, 21 , 22, 23 may provided as brush type sealing element, cloth type sealing element, a narrow gap or diffusion gap. The narrow gap may be provided with the axial divider 4, 5 or with the circumferential divider 2 or with the wall portions 26, 27 defining the pressure balancing volume 8, 9. The narrow gap is thus provided between the side surface 24, 25 or the periphery of the rotor 1 and the divider 4, 5, 2 or the wall portion 26, 27. The narrow gap provides a high resistance to the hinder leakage flow.

[0035] The circumferential pressure balancing volume 9 is arranged to extend circumferentially around the periphery 3 of the rotor 1 or the outside edge of the side surface 24, 25 of the rotor 1 . Thus the circumferential seal 6 is arranged to the circumferential divider 2 such that the circumferential seal extends between the circumferential divider 2 and the periphery 3 of the rotor 1 .

[0036] The axial pressure balancing volume 8 is arranged to extend across a first and second side surface 24, 25 of the rotor 1 on the first and second side 12, 13 of the rotor 1 , respectively. Thus the axial seals 7, 10 are arranged to the first and second axial dividers 4, 5 such that the axial seals 7, 10 extend between the axial divider 4, 5 and the side surface 24, 25 of the rotor 1 .

[0037] The axial pressure balancing volume 8 is arranged such that it sits offset from the rotation axis 1 1 and the circumferential pressure balancing volume 9 is arranged such that it covers an area of the side surface 24, 25 of the rotor 1 . In a preferred embodiment of the axial pressure balancing volume 8 the cross sectional area of axial pressure balancing volume extends across the full side surface 24, 25 of the rotor 1 . In a preferred embodiment of the circumferential pressure balancing volume 9 the cross sectional area of the circumferential pressure balancing volume 9 follows circumferentially around the periphery 3 of the rotor. The cross section of the pressure balancing volume 8, 9 may be may be rectangular, triangular, polygonal, circular, oval or any other shape. The overall volume of the pressure balancing volume 8, 9 may be chosen according to the application and the parameters of the rotor 1 and the rotary heat exchanger. Thus the pressure balance volume 8, 9 can take any form such as to create a suitable pressure balancing effect.

[0038] Analysis and test results of the present invention, shown in figure 9, present that reduction in the axial seal leakage is very similar to that of the prior art where a pressure balancing damper 38 is used to minimise the flow leakage, as shown in figure 5. The leakage through the circumferential seal 6 is actually decreased by 25 to 50 % in the solution of the present invention in relation to the prior art when a pressure balance damper 38 is used.

[0039] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. A rotor assembly for a rotary heat exchanger, the rotor assembly comprising:

- a rotor (1 ) arranged to rotate around a rotation axis (11 ), the rotor (1) having a first side (12) and a second side (13) in the direction of the rotation axis (11);

- a circumferential sealing unit (2, 6) arranged around the periphery (3) of the rotor (2) for isolating the first side (12) and the second side (13) of the rotor (1);

- a first axial sealing unit (4, 7) on the first (12) of the rotor (2) for dividing the first side (12) of the rotor (2) to two adjacent plenums (14, 17); and

- a second axial sealing unit (5, 10) on the second side (13) of the rotor (2) for dividing the second side (13) of the rotor (2) to two adjacent plenums (15, 16),

characterized in that at least one of the sealing units (2, 6; 4, 7; 5, 10) is provided with a seal (7, 10, 6) having a pressure balancing volume (8, 9) for balancing the pressure difference over the sealing unit (2, 6; 4, 7; 5, 10).

2. A rotor assembly according to claim 1, characterized in that the seal (7, 10, 6) having two sealing elements (20, 21; 22, 23) provided between the pressure balancing volume (8, 9) and the adjacent plenums (14, 17; 15, 16) or the first and second side (12, 13) of the rotor (1 ).

3. A rotor assembly according to claim 1 or 2, characterized in that the first axial sealing unit (4, 7) and the second axial sealing unit (5, 10) comprise an axial seal (7, 10) having a first axial sealing element (22) between an axial pressure balancing volume (8) and one plenum (14, 15) and a second axial sealing element (23) between an axial pressure balancing volume (8) and the other plenum (16, 17).

4. A rotor assembly according to claim 1 or 2, characterized in that the circumferential sealing unit (2, 6) comprises a circumferential seal (6) having a first circumferential sealing element (20) between a circumferential pressure balancing volume (9) and the first side (12) of the rotor (1 ) and a second circumferential sealing element (21) between a circumferential pressure balancing volume (9) and the second side (13) of the rotor (1 ).

5. A rotor assembly according to any one of claims 2 to 4, c h a r - acterized in that the sealing element (20, 21 , 22, 23) is arranged to be pressure permeable.

6. A rotor assembly according to any one of claims 2 to 5, c h a r - acterized in that the sealing element (20, 21 , 22, 23) is a brush type sealing element, cloth type sealing element, a narrow gap or diffusion gap.

7. A rotor assembly according to any one of claims 1 to 6, c h a r - acterized in that the circumferential pressure balancing volume (9) is arranged to extend circumferentially around the periphery (3) of the rotor (1).

8. A rotor assembly according to claim 7, characterized in that the circumferential sealing unit (2, 6) comprises a circumferential divider (2) provided on periphery (3) of the rotor (1 ) for isolating the first and second side (12, 13) of the rotor (1), and that the circumferential seal (6) is arranged to the circumferential divider (2) such that the circumferential seal extends between the circumferential divider (3) and the periphery (3) of the rotor (1).

9. A rotor assembly according to any one of claims 1 to 8, c h a r - acterized in that the axial pressure balancing volume (8) is arranged to extend across a first and second side surface (24, 25) of the rotor (1) on the first and second side (12, 13) of the rotor (1), respectively.

10. A rotor assembly according to claim 9, characterized in that the first and second axial sealing unit (4, 7; 5, 10) comprise respectively a first and second axial divider (4, 5) extending in the direction of the rotation axis (11 ) of the rotor (1 ) for isolating the two adjacent plenums (14, 17; 15, 16) from each other on the first and second side (12, 13) of the rotor (1 ) respectively, and that the axial seals (7, 10) are arranged to the first and second axial dividers (4, 5) such that the axial seals (7, 10) extend between the axial divider (4, 5) and the side surface (24, 25) of the rotor (1).

11. A rotary heat exchanger in which inlet air (I) is heated to supply air (S) by using thermal energy of discharge air (D) such that the discharge air (D) is cooled to outlet air (O), the rotary heat exchanger having a rotor unit (30) comprising:

- a rotor (1 ) for carrying out the heat exchange;

- an inlet plenum (14) for conducting inlet air (I) to the rotor (1 );

- a supply plenum (15) for receiving supply air (S) from the rotor (1);

- a discharge plenum (16) for conducting discharge air (D) to the ro- tor (1 );

- an outlet plenum (17) for receiving outlet air (O) from the rotor (1);

- a circumferential sealing unit (2, 6) for isolating the inlet plenum

(14) from the supply plenum (15) and discharge plenum (16) from the outlet plenum (17);

- a first axial sealing unit (4, 7) for isolating the inlet plenum (14) from the outlet plenum (17); and

- a second axial sealing unit (5, 10) for isolating the supply plenum

(15) from the discharge plenum (16),

characterized in that at least one of the sealing units (2, 6; 4, 7; 5, 10) is provided with a pressure balancing volume (8, 9) between the plenums (14, 15, 16, 17).

12. A rotary heat exchanger according to claim 11, characterize d in that sealing unit (2, 6; 4, 7; 5, 10) is provided with a seal (7, 10, 6) having two sealing elements (20, 21; 22, 23) provided between the pressure balancing volume (8, 9) and the adjacent plenums (14, 17; 15, 16).

13. A rotary heat exchanger according to claim 11 or 12, characterized in that the first axial sealing unit (4, 7) comprise a first axial seal (7) having a first axial sealing element (22) between a first axial pressure balancing volume (8) and inlet plenum (14) and a second axial sealing element (23) between the first axial pressure balancing volume (8) and the outlet plenum (16).

14. A rotary heat exchanger according to any one of claims 11 to

13, characterized in that the second axial sealing unit (5, 10) comprise a second axial seal (10) having a first axial sealing element (22) between a second axial pressure balancing volume (8') and supply plenum (15) and a second axial sealing element (23) between the second axial pressure balancing volume (8') and the discharge plenum (16).

15. A rotary heat exchanger according to any one of claims 11 to

14, characterized in that the circumferential sealing unit (2, 6) comprises a circumferential seal (6) having a first circumferential sealing element (20) between a circumferential pressure balancing volume (9) and the inlet plenum (14) or the outlet plenum (17) and a second circumferential sealing element (21) between a circumferential pressure balancing volume (9) and the supply plenum (15) or the discharge plenum (16).

16. A rotary heat exchanger according to any one of claims 11 to

15, characterized in that the circumferential sealing unit (2, 6) comprises a circumferential divider (2) provided on periphery (3) of the rotor (1) for isolating the first and second side (12, 13) of the rotor (1 ), and that the circumferential seal (6) is arranged to the circumferential divider (2) such that the circumferential seal (6) extends between the circumferential divider (3) and the periphery (3) of the rotor (1 ).

17. A rotary heat exchanger according to any one of claims 11 to

16, characterized in that the first and second axial sealing unit (4, 7; 5, 10) comprise respectively a first and second axial divider (4, 5) extending in the direction of the rotation axis (11 ) of the rotor (1 ) for isolating the two adjacent plenums (14, 17; 15, 16) from each other on the first and second side (12, 13) of the rotor (1) respectively, and that first and second axial seals (7, 10) are arranged to the first and second axial dividers (4, 5) such that the first and second axial seals (7, 10) extend respectively between the axial divider (4, 5) and the side surface (24, 25) of the rotor (1).