WO1994014015A1 - Regenerative heat exchanger for gaseous media, especially air heat exchanger for room ventilation of buildings - Google Patents

Abstract

The regenerative heat exchanger proposed, which operates preferably on a countercurrent-flow basis, uses as its heat-storage unit or heat-exchange element a net-like structure through which the heat-releasing and heat-absorbing gas (air) flows in alternation. Viewed in the direction of flow, this structure consists of a relatively large number of superposed layers. The structure (24) is preferably manufactured from thin, flexible woven fabric made, in particular, of synthetic material. In a preferred embodiment, the structure (24) is mounted on the wall of a rotating body (5).

Description

 Regenerative heat exchanger for gaseous media, especially air heat exchangers for the ventilation of buildings

- 1

The invention relates to a regenerative heat exchanger for gaseous media, in particular an air heat exchanger for the ventilation of rooms in buildings, with a heat storage device through which the heat-emitting and the heat-absorbing gaseous medium flow in an alternating sequence.

The regenerative heat exchanger according to the invention is preferably intended for room ventilation or air conditioning of buildings and is explained in more detail below in connection with this purpose. However, it goes without saying that it has a broader range of use and can in principle be used for the heat exchange between heat-emitting and heat-absorbing gaseous media, e.g. for heat recovery from exhaust air or from exhaust gases, for example from heating systems, in gas turbines and. like.

To a large extent, the heating of building rooms is still carried out by opening the windows or also by means of fans which convey the used room air to the outside or suck in fresh air from outside. The associated heat losses are considerable (approx. 2000 KWh primary energy per capita and year). Central air conditioning systems, which can usually only be found in large buildings, use heat exchangers for the exchange of heat between the supply and exhaust air. also regenerative heat exchangers, which, however, work with efficiencies of up to about 70%. Even smaller ventilation devices, which are intended for room ventilation or room air conditioning in the living area, only enable heat recovery in the order of about 45%.

CORRECTED SHEET (RULE 91) ISA / EP The lower the efficiency of a room ventilation with heat recovery from the exhaust air, the easier the gain achieved by heat recovery is wasted due to over-ventilation. Normally, the air conditioning systems that work with heat recovery are therefore equipped with complex sensors and controls. The reduced air quality that can often be observed in this way often leads to the fact that the fresh air requirement is covered by opening additional windows. Central systems also require a very high proportion of energy for pure air ventilation. System pressure losses of 1000 to 2000 Pa are not uncommon.

The object of the invention is above all to create a regenerative heat exchanger which can be used with particular advantage as a fresh air heat exchanger for room ventilation or air conditioning and which can also be carried out as a small device with comparatively low construction costs, but with can work much more efficiently than comparable devices.

According to the invention, this object is achieved in that the heat storage device consists of a multilayer, network-like structure. The net-like structure preferably has a woven structure, although a lattice structure is also possible. The mesh-like structure is preferably made of plastic, e.g. Polyethylene, manufactured.

According to the invention, a mesh-like structure, preferably made of a thin fabric material, is used for the regenerative heat exchanger as a heat-absorbing and heat-storing device, which can be made comparable to the fabrics used for fly screens or can consist of such a fabric material. This thin fabric or net material, seen in the direction of flow of the air, is put together in several layers or layers to form the net-like structure forming the heat storage device and has a sufficiently high heat absorption capacity for the heat exchange. The fabric or lattice material forming a laminated body is an inexpensive and easy-to-process material which enables the construction of a heat exchanger with comparatively small dimensions in the flow direction.

CORRECTED SHEET (RULE 91) ISA / EP device and small weight, can also be easily cleaned if necessary.

With the use of the above-mentioned heat-absorbing and storing structural material in a more or less large number of layers arranged one behind the other in the direction of flow of the gas or air, a highly efficient regenerative heat exchanger with a high efficiency can be created, which is also easily achieved 90% can lie. In addition to the high heat transfer figures and the relatively large heat capacity of the network-like structure constructed in a plurality of layers lying one above the other, its low thermal conductivity in the flow direction proves to be advantageous. A high thermal conductivity in the flow direction would have a negative effect on the possible degree of heat exchange as a result of temperature compensation of the temperature gradient between the individual layers. The low thermal conductivity in the flow direction is particularly important in the case of heat exchangers with a small flow length and at the same time a low flow rate. The low conductivity of the multilayer network-like structure, which is advantageous for the high efficiency, in the flow direction results on the one hand from its production from plastic material, and on the other hand also because, when the individual layers or layers lie directly on top of one another, essentially only point contact between the layers of the fabric - or mesh material are available. On the other hand, there is also the possibility of spacing the individual layers of the net-like structure used as a heat storage device from one another by means of spacing elements arranged between them. The at least extensive deactivation of the thermal conductivity in the flow direction of the air is indicated in particular in the case of heat exchangers operated in counterflow with small dimensions in the flow direction with regard to the high efficiency. The poor thermal conductivity of the fabric or lattice material made of plastic plays almost no role for the absorption and storage of the heat because of the comparatively small wire thicknesses of the net-like structure.

It goes without saying that the number of layers or layers of the net-like structure used as a heat storage device depends on the nature of the fabric or grid material (thickness of the material used for this purpose).

CORRECTED FLOW (RULE 91) ISA / EP wires and mesh size) and can vary depending on the conditions of use. It is determined by the relationship

N. 1 - 1 (N = number of layers, i ^ = efficiency) 1-q

For the heat exchanger according to the invention or its net-like structure forming the heat storage device, a thin and flexible fabric (or grid material) is expediently used, which in particular in a heat exchanger for room ventilation consists of thin wires with a wire thickness of approximately 0.15 to 0.3 mm is made and the clear square mesh size is preferably 0.5 mm to 1.4 mm. Just like the number of layers of the net-like structure, the mesh size and the wire thickness can vary in relatively wide ranges. A favorable ratio of clear mesh size to wire size is in the range 3 to 6.

The individual layers or layers of the network-like structure used as a heat exchanger can be formed by placing the desired number of individual fabric or lattice blanks on top of each other in layers. From a manufacturing point of view, however, it is generally more advantageous if the net-like structure is made from a thin, flexible fabric or lattice band, which is folded in a zigzag pattern to form the layer. An arrangement in which the thin, flexible fabric tape (or mesh tape) with the desired number of winding layers is wound into a winding body is particularly advantageous. As mentioned, the regenerative heat exchanger according to the invention can be used with particular advantage as a fresh air heat exchanger for room ventilation or for room air conditioning, it being able to be designed as a lightweight, small device for individual room ventilation or room cooling. It can be installed in a window of the room or in an opening in the outer wall of the building. Due to the high efficiency, the moisture contained in the exhaust air, which condenses on the network-like structure as it flows through, can be fed directly to the fresh air supplied in countercurrent, so that even in colder outside temperatures, the fresh air almost into the room with the temperature and humidity of the room air

CORRECTED SHEET (RULE 91) ISA / EP reached. In addition, the fresh air can also be actively cooled with the heat exchanger according to the invention if the exhaust air is moistened up to about the cooling limit upon entry into the heat exchanger device and then allowed to flow through the heat exchanger. The fresh air then almost enters the room at the cooling limit temperature corresponding to the room air condition, but without having taken up additional moisture.

The regenerative heat exchanger according to the invention, which preferably works in countercurrent to the heat-emitting and heat-absorbing air (or another gaseous medium), can be designed in various ways using the multi-layer network-like structure, e.g. in a simple way as a countercurrent heat exchanger with a built-in network-like structure, which is alternately flowed through by the exhaust air and the supply air. In this case, heat exchangers working in opposite directions must be used.

In a particularly advantageous embodiment of the invention, the multilayer network-like structure is arranged at the beginning of a, preferably cylindrical, rotating body, the interior of which is separated by a partition in counterflow chambers for the flow of the heat-emitting and the heat-absorbing gaseous medium (exhaust and supply air) in the counter Current is divided, the partition wall is expediently arranged fixed with respect to the rotating rotating body and the rotating body is preferably a support grid or the like. formed gas-permeable jacket as a carrier for the net-like structure. It is advisable to wind the flexible fabric or mesh material with the desired number of winding layers on the rotating body jacket. The drivable rotating body with the multi-layered net-like structure (winding body) arranged on its casing has a comparatively large heat storage capacity in the case of small structural dimensions in the flow direction and a small structural weight and can be operated with small fan powers due to the comparatively small air flow resistance, so that the energy expenditure for the extraction of exhaust and supply air is comparatively low. It can easily be accommodated in building rooms, in particular, as mentioned, in a window or in a room

Outside wall opening.

CORRECTED SHEET (RULE 91)

ISA / EP Further advantageous design features of the heat exchanger designed as a rotating rotating body are specified in the individual claims.

The invention is explained in more detail below in connection with the preferred exemplary embodiment shown in the drawing. The drawing shows:

1 shows a regenerative heat exchanger according to the invention in the attached state on a window, an outer wall of the building or the like.

2 shows the heat exchanger according to FIG. 1 in a view from the room side in the direction of arrow II of FIG. 1;

3 shows the heat exchanger according to FIGS. 1 and 2 in a perspective view, partially broken away;

4 shows, in large enlargement and in partial section, the heat storage device according to the invention consisting of several layers;

5 is a plan view in the direction of arrow V of FIG. 4th

The regenerative heat exchanger 1 shown forms a fresh air heat exchanger for the ventilation or air conditioning of a room within a building. It is mounted on the inside of the room in front of an opening 3 of a window 4 by means of a mounting plate 2. Instead, the heat exchanger 1 can also be installed on or in the opening of an outer wall of the building.

The heat exchanger 1 has a cylindrical rotating body 5. This consists of a cylindrical jacket 6, which is provided with a plurality of openings for the passage of the supply and exhaust air and suitably consists of a support grid or the like carrying the heat exchange body. With the jacket 6 is an end plate 7, the rotary body 5 on the room side, i.e. closes on the side of its jacket 6 opposite the mounting plate 2.

CORRECTED SHEET (RULE 91) ISA / EP In the interior of the rotating body 5 there is a partition 8 fixedly arranged on the mounting plate 2, which, as shown in FIGS. 2 and 3, passes through the rotating body 5 in the diameter direction and divides the interior of the rotating body 5 into two counterflow chambers 9 and 10 which are sealed off from one another. The partition 8, which is fixed with respect to the rotating body 5 rotating about its axis, is sealed with respect to the end wall 7 of the rotating body by means of a flexible seal 11. In the exemplary embodiment shown, this consists of an elastic sealing strip which is arranged on the relevant longitudinal edge of the partition 8 and which seals against the inside of the end plate 7. The partition 8 also has a sealing element 12 (FIGS. 2 and 3) on its two parallel narrow sides, which produces the seal of the partition against the cylindrical inner surface of the jacket 6 and, in the exemplary embodiment shown, also from one on the partition attached flexible sealing strips. Instead of the flexible sealing strips, other sealing elements can also be provided to seal the partition against the rotating body.

The jacket 6 of the rotating body 5 is sealed on the side opposite the end plate 7 via a circumferential seal 13 with respect to the mounting plate 2, this seal 13 also being able to consist of an annular elastic sealing strip or another mechanical seal. It is essential that the two countercurrent spaces 9 and 10 in the interior of the rotating body 5 are sealed off from one another and at the circumference of the casing against the mounting plate 2.

The rotating body 5 is supported with its end plate 7 centrally on an axis of rotation 14 arranged on the mounting plate 2, which, as shown in FIG. 1, extends through the closed partition 8 and an opening arranged in the middle of the end plate 7. The position of the rotating body 5 with respect to the mounting plate 2 and the partition 8 is ensured with the aid of a securing member 15 on the passage of the axis of rotation 14 through the end plate 7. This securing member 15 can be made from a simple nut, e.g. a knurled nut, which is screwed onto the threaded end of the axis of rotation 14. The axis of rotation 14 can be rotatably mounted on the mounting plate 2 and in this case forms a shaft connected to the rotating body 5 or its end plate 7 in a rotationally locking manner. But it can also

CORRECTED SHEET (RULE 91) ISA / EP be fixed to the mounting plate 2 so that the rotating body 5 is rotatably mounted on the free end of the axis of rotation 14 by means of a rotary bearing, for example a plain bearing. When the securing member 15 is released, the entire rotating body 5 can be pulled off the partition 8 and the mounting plate 2 toward the inside of the room, for example in order to clean the heat storage device arranged on the rotating body jacket.

A plurality of rollers 16, in the exemplary embodiment shown (FIG. 2), four rollers 16 are mounted on the mounting plate 2 in the circumferential direction and are mounted on roller holders 17, which roll on the inner surface of the cylindrical rotating body shell 6 and thus the rotating body 5 on the side Support and store the mounting plate 4 in a rotatable manner. The rollers 16 are preferably made of a rubber or plastic material or are covered on their circumference with such a material. One of these rollers 16 can be driven with the aid of a small electric drive motor 18. It forms the drive roller for a friction wheel drive. With the help of this friction wheel drive, the rotating body 5 can be rotated about its axis relative to the mounting plate 2 and the partition 8. The drive motor 18 is arranged like the rollers 16 in the interior of the rotating body 5.

The mounting plate 2 has an opening 19 and 20 on both sides of the partition 8. The openings 19 and 20 lie within the opening 3 of the window pane 4 or within the building wall opening receiving the heat exchanger 1. At or in each opening there is a fan 21 which is driven by a small electric motor 22. The fans 21 with their electric motor 22 are each arranged on a bracket 23 which is attached to the partition 8 in the interior of the rotating body 5.

The heat storage device of the heat exchanger, which consists of a multilayer network-like structure 24, is located on the cylindrical jacket 6, which is designed as a support grid or the like. The net-like structure 24 has a woven structure, i.e. it consists of thin, flexible fabric elements, which are arranged in several superimposed layers on the support grid of the rotating body shell. 4 and 5 show exaggeratedly large for clarification, the thin fabric material consists of longitudinally and transversely running, interwoven

CORRECTED SHEET (RULE 91) thin wires 25 or 26 made of plastic, for example polyethylene or polyamide or the like. For simplification, FIG. 4 shows only four layers A to D lying on top of one another, each of which consists of a thin fabric element. The multi-layered net-like structure 24 advantageously consists of a thin fabric tape wound on the jacket 6 of the rotating body 5 with the desired number of winding layers, the width of which corresponds approximately to the width of the cylindrical rotating body 5. The thin, flexible fabric tape is thus wound up in the manner of a bandage with a tension sufficient for the tight fit and with the desired number of winding layers on the jacket 6 of the rotating body 5 and fixed to it in a suitable manner. FIG. 4 shows that the overlapping layers or winding layers A, B, C, etc. essentially lie on one another only with point-like or line-shaped contact of their thin wire elements 26. On the two opposite annular end faces of the cylindrical winding body, the winding layers can be fixed against one another by an annular border 27, the border 27 also closing the winding body on its ends. The bezels 27 can consist of a plastic ring or be formed by a hardening casting compound.

The regenerative heat exchanger described works as a countercurrent heat exchanger. The room or exhaust air is sucked out of the room by one of the two ventilators 21 and led outside through the opening 3. Here, the room air flows in the direction of arrow 34 over the half circumference of the rotating body through the net-like structure 24 arranged on the jacket 6 into the counterflow chamber 9 and from there in the direction of the arrow 33, 31 through the opening 19 of the mounting plate 2 to the outside. The fresh or supply air flows in the opposite direction, i.e. in the direction of the arrow 29 from the outside through the opening 20 of the mounting plate 2 into the other counterflow chamber 10 and from there over the other half circumference of the jacket 6 and the area of the net-like structure 24 located here in the direction of the arrow 28 into the room. Since the rotary body carrying the heat storage device executes a continuous rotary movement in the ventilation mode with the aid of the rotary drive 16, 18, there is a heat exchange between the exhaust and supply air. The e.g. from the room air as it flows in the direction of arrow 34 to the net-like structure 24 and heat absorbed and stored by the latter

CORRECTED SHEET (RULE 91) When the rotating body 5 continues to rotate, the supply or exhaust air flowing through the net-like structure 24 in the direction of the arrow 28 from the inside to the outside is released to the latter, so that room ventilation with heat recovery is achieved. The same applies in principle if the fresh air supplied from outside has a higher temperature level than the room air discharged from the room.

With the help of the heat exchanger described, the moisture contained in the exhaust air is also fed directly to the supply air or fresh air, since the moisture given off to the net-like structure 24 by the exhaust air is absorbed by the fresh air which heats up when the net-like structure flows through it. The heat exchanger can also be used to cool the fresh air supplied to the room by humidifying the exhaust air with the aid of a suitable humidification device arranged on the device, approximately up to the cooling limit, and then flowing it through the heat exchanger. The fresh air then almost enters the room at the cooling limit temperature corresponding to the room air condition, without having absorbed additional moisture.

With the heat exchanger described above, high efficiencies can be achieved even in the order of 90%. The desired operating conditions can be set via the number of winding layers of the net-like structure 24 forming the heat storage device and the size of the outer surface of the rotating body shell 6 and thus the area through which the net-like structure 24 flows.

Some examples of the design of the heat exchanger described are given below with different volume flows for the supply and exhaust air and with different numbers of layers or winding layers of the net-like structure 24. The values given in the table below relate to a total passage area of the net-like structure 24 (cylinder circumference x length) of 1 m, it being assumed that the same supply and exhaust air quantities are used. A plastic fabric material with a thickness of the wires 25 and 26 of 0.3 mm and a light mesh width of the square fabric mesh of 1.4 mm is used for the net-like structure 24.

CORRECTED SHEET (RULE 91) With similar geometric relationships (variation of the wire thickness), the table data n change by the factor (d / do) ', t by the factor (d / do)' and the speed by the factor (d / do) ^" ", if d means the wire gauge and do the reference wire gauge. The other specific data remain largely unaffected.

table

In the above table are:

V = volume flow per side (m / h) dP = pressure loss per side (Pa) n = number of layers t = depth in flow direction (mm) i ^ = degree of heat exchange (%)

Surprisingly, the high efficiencies given in the above table can be achieved with a relatively low rotational speed of the rotating body. In order to achieve an efficiency of the order of 90% with a pressure loss of the air in the net-like structure 24 of 25 Pa and an air flow velocity of approximately 0.39 m / s through the net-like structure, a speed of 10 U / mi is already sufficient out. If the speed is halved, the heat exchanger still works with an efficiency of about 89%.

The heat exchanger described above can be modified in various ways. In general, it is sufficient if the rotating body 5 is mounted on the side of the mounting plate 4 only on three bearing or rollers. The two fans 21 can also be installed with their housings directly in the openings 19 and 20 of the mounting plate 2. The air- permeable jacket 6 of the rotating body 5 can also consist of plastic or metal, for example from a sufficiently rigid metal mesh. The partition 8 can also consist of plastic, metal or wood. Instead of the preferably provided fabric material for the construction of the multilayer heat storage device, a correspondingly thin, flexible grid element made of intersecting plastic wires 25 and 26 can also be used, these being fixed to one another at the crossing points. The multilayered net-like structure 24 should be made from a woven material or a lattice material with a relatively open regular structure. The thermal conductivity of the net-like structure 24 in the flow direction should be kept as low as possible. This is given by the preferably used plastic material and by the described point or line contact of the individual layers A, B, C etc. lying one on top of the other. In a departure from the exemplary embodiment described, the body 5 carrying the net-like structure 24 can also be arranged in a fixed manner. In this case, the partition 8 can be made rotatable with respect to the body 5 together with the fan device.

As mentioned, the regenerative heat exchanger according to the invention can also be part of an air cooling device which uses evaporating water to generate cold. The device can also be used for air humidification. It then has a humidifying device through which the air to be humidified flows, e.g. one or more air-permeable elements, arranged one behind the other, made of an absorbent material and moistened by a water supply on the device. If the supply or fresh air flowing through the heat exchanger is to be cooled, the exhaust air discharged from the room can be moistened with a suitable device before it flows through the network-like structure. This can be carried out with an extremely low expenditure of energy if the air-humidifying elements are also fabric or grid elements made of an absorbent material, e.g. Cotton or the like is produced and, viewed in the direction of flow of the exhaust air, is arranged in several, suitably about 3 to 8 layers, the fabric or grid elements being e.g. be moistened with water using a spray device.

Finally, the multi-layer network-like structure according to the invention can also be used as a heat storage device in heat exchangers of other designs

CORRECTED SHEET (RULE 91) and / or used as a heat exchanger for other purposes, for example for heat recovery from exhaust gases. Particularly when the regenerative heat exchanger is used at high operating temperatures, the network-like structure consisting of several layers according to the invention can also be made from a woven or lattice material made of metal. In this case, it is advisable to arrange spacer elements between the individual layers, preferably in the form of a grid or fabric layer, the mesh size of which is, for example, 5 times greater than the mesh size of the fabric or grid material used for the heat-exchanging net-like structure. The multilayer network-like structure according to the invention can also be used as a heat storage device even in static heat exchangers. Advantageously, the heat storage device according to the invention can also be designed in such a way that the multi-layered net-like structure is formed overall into an approximately zigzag-shaped or meandering structure. Such a design is particularly recommended in the case of a static heat exchanger through which the heat-absorbing and the heat-emitting gaseous medium flow alternately in alternating directions. With this design of the net-like structure, particularly small dimensions for the heat exchanger can be achieved. As mentioned, the net-like structure is made from thin wires or monofilament threads, the thickness of which is advantageously up to about 1 mm, in a preferred embodiment less than 0.3 mm. The ratio of the clear mesh size of the fabric or grid material to the wire thickness is expediently in the range from 2 to 8, preferably 5.

CORRECTED SHEET (RULE 91) ISA / EP

Claims

Claims 1. Regenerative heat exchanger for gaseous media, in particular air heat exchanger for the ventilation of rooms in buildings, with a heat storage device through which the heat-emitting and the heat-absorbing gaseous media flow in an alternating sequence, characterized in that the heat storage device consists of a multilayer network-like structure (24). there, the network-like structures are largely thermally decoupled in the flow direction. 2. Heat exchanger according to claim 1, characterized in that the netzar¬ term structure (24) made of plastic, e.g. Polyethylene. 3. Heat exchanger according to claim 1, characterized in that the individual layers (A, B, C etc.) of the net-like structure (24) by spacing elements arranged between them, e.g. Tissue or lattice layers with a larger mesh size are spaced. 4. Heat exchanger according to claim 1, characterized in that the number of layers of the net-like structure (24) is at least equal to l - l, preferably lies above. ~ ¹ ^ 5. Heat exchanger according to claim 1, characterized in that the ratio of the clear mesh size to the wire thickness of the net-like structure is in the range of 2-8, preferably 5. 6. Heat exchanger according to claim 1, characterized in that the multilayer network-like structure (24) is arranged on the circumference of a, preferably cylindri¬'s, rotating body (5), the interior of which by a partition (8) in counterflow chambers (9 , 10) for the flow through the heat-emitting and the heat-absorbing gaseous medium (exhaust air and supply air) is divided in countercurrent. 7. Heat exchanger according to claim 6, characterized in that the rotary body (5) or the like, preferably of a support grid. formed, gas-permeable jacket (6) as a carrier for the multi-layer network-like structure (24). CORRECTED SHEET (RULE 91) 8. Heat exchanger according to claim 1, characterized in that it is arranged on a window or building wall opening (3) of the room. 9. Heat exchanger according to claim 8, characterized in that it is provided with an exhaust-side device for air humidification, comprising a substantially perpendicular to the direction of flow, humidified, preferably multi-layered fabric of high absorbency with a lattice structure approximately corresponding to that of the net-like structures. 10. Heat exchanger, characterized in that it forms a device limitation on the room outlet side. CORRECTED SHEET (RULE 91) ISA / EP