EP1613863A1

EP1613863A1 - A ventilating device comprising a cross-flow impeller

Info

Publication number: EP1613863A1
Application number: EP04725886A
Authority: EP
Inventors: Ole Hansen
Original assignee: Danfoss AS
Current assignee: Meinertz AS
Priority date: 2003-04-14
Filing date: 2004-04-06
Publication date: 2006-01-11
Also published as: WO2004090337A1; RU2005135906A; CN1798928A

Abstract

The present invention relates to a ventilating device with a cross-flow impeller and a holder for attaching the device to a building component. The holder does not interfere with the air-stream generated by the impeller and therefore, it is possible to integrate the ventilating device more flexibly into various building components without having to consider inlet and outlet directions determined in relation to the holder holding the impeller. The invention further relates to a stabilizing member with a porous material which dampens the noise which is normally generated by stabilizers of cross-flow blowers.

Description

A VENTILATING DEVICE COMPRISING A CROSS-FLOW IMPELLER

Introduction

The present invention relates to a ventilating device comprising a cross-flow impeller, and in particular, to a holder which connects a cross-flow impeller to a building component at least substantially without interfering with the generated air-stream. The ventilating device can be used, e.g. for forcing thermal convection between a heat exchanger, e.g. a radiator and the surrounding atmosphere. Furthermore, the invention relates to a stabilizing member to be arranged between an inlet zone and an outlet zone of a cross-flow blower for stabilizing an air stream from the blower and to a method for establishing convection in a building.

Background of the invention

In general, cross-flow blowers are used for ventilation and for forcing thermal convection, e.g. in combination with central-heating units for houses. The use of a cross- flow blower enables a highly improved convection between a radiator and the surroundings and, accordingly, the need for large radiators is reduced. In the known blowers, a cross- flow blower is provided in a housing comprising a chassis and a cover. The purpose of the chassis is partly to provide an air-passage which forces the air through the impellers of the cross-flow blower and partly to carry the impeller in a supporting unit which can be fixed, e.g. to the floor or the roof of a building. The purpose of the cover is mainly to ensure the safety of the cross-flow blower in operation and, sometimes, the cover is adapted in order to defuse the air-stream exiting from the blower. An unshielded impeller of the regular type for a cross- flow blower would under normal conditions not be capable of generating an air-stream to and from the impeller. On the contrary, rotation of the impeller would merely cause a slight turbulence around the impeller. Also for that reason, it has always been a general view that cross-flow blowers must have an air guiding housing ensuring the generation of an air-stream forming convection with the surroundings .

GB 1,146,503 discloses a cross-flow blower of the above mentioned kind. The blower is provided with a guide plate 2 forming a chassis which guides the air from an inlet part of the blower to an outlet part of the blower. In order to separate an inlet stream of air from an outlet stream of air, the blower is fitted with a vortex inducing tongue 3.

Since the housing of the traditional blowers is used for guiding the air streams in certain directions and since the housing takes up relatively much space compared to the ventilating impeller, difficulties in the adaptation of traditional cross-flow blowers in building structures has been experienced. As an example, it can be difficult to fit the traditional cross-flow blowers into narrow spaces, e.g. in connection with thermal convective constructions, such as radiators for heating or cooling, or, such as for establishing convection around pipes, e.g. in connection with old installations and in cases wherein the space is limited. Moreover, the housing implies additional costs to the making of the cross-flow blower and it may even be undesired for architectural and design related reasons or the housing may prevent the air from leaving the blower in a specifically desired direction.

Description of the invention

It is an object of the present invention to overcome the disadvantages of the known cross-flow blowers.

Accordingly, the present invention, in a first aspect, relates to a ventilating device comprising:

- a cross-flow impeller extending in a longitudinal direction around an axis of rotation and being adapted to generate an air-stream extending from the ambience towards an inlet zone, from the inlet zone to an outlet zone and from the outlet zone towards the ambience, and - a holder comprising fastening means adapted to connect the impeller to a building component,

characterized in that the holder connects the impeller to the building component at least substantially without interfering with the generated air-stream so as to allow the direction from the inlet to the outlet to be selected independently upon the direction of the holder in relation to the building component .

Since the holder of the impeller does not interfere with the generated air-stream, it is possible, to integrate the impeller more flexibly into existing buildings or into architectural features of a modern house, e.g. by attaching the impeller directly onto pipes of a central heating system, onto or behind wall panels, or by any similar integration of the impeller into the building. In particular, the holder of the ventilating device could be formed as an ad-on component or integrally with a pipe holder such as a clip-on pipe holder or any similar arrangement for holding pipes to walls, roofs, floors etc.

The impeller could be a regular oblong impeller known per se from traditional cross-flow blowers. At one end zone, and optionally at both of the two axially disposed end- zones of the impeller, the impeller could be fastened to the holder via a rotational bearing allowing the impeller to rotate in relation to the holder and the surrounding building. The rotation of the impeller would normally be caused by an electrical motor connected to or integrated with the impeller. In this respect, it should be noted, that the impeller itself could constitute the rotor of this motor while the holder constitutes the stator of the motor. The impeller could also be fastened to the holder at a point in between the two end zones from which point one part of the impeller extends axially in one direction from the holder and one part extends axially in the opposite direction from the holder. Most preferably, however, is a holder which is capable of holding the impeller in one out of two axially disposed end-portions thereof, at least substantially without hindering passage of an air-stream extending into and out of the outer peripheral surface of the impeller in a direction perpendicular to the longitudinal axis of the impeller. Moreover, the holder may form a suspension for holding two impellers extending in a longitudinal direction from the holder. The holder may allow rotation of a first one of the two impellers to be transferred to the other one of the two impellers thus allowing a row of impellers to be driven by one motor. The holder may hold the rotational bearing thus allowing the impeller to rotate around its axis of rotation and may further comprise a spherical bearing connected between the rotational bearing and the holder. The spherical bearing could allow the impeller to be rearranged in space, i.e. allow the longitudinal direction of the impeller in relation to the building component to be changed. It is, however, often desirable to lock the longitudinal direction of the impeller to a fixed direction in respect of the building component. As an example, it may be desired to use the building component, e.g. a substantially plan wall panel for guiding the air-stream generated by the impeller. In such a setup, the wall panel inherits the function of the traditional housing for the cross-flow blower, namely the function of generating an air-stream between the impeller and the surroundings. For that reason, the ventilation device according to the present invention may preferably have a holder with fastening means which determines a longitudinal direction of the impeller in relation to a building component to which the ventilating device is connected.

In order to use the building component, e.g. a wall panel, a roof, a part of the floor, a window, a radiator, a pipe or any similar building component for guiding an air- stream to and from the ventilating device and thus for ensuring that the impeller does not merely generate turbulent flow rotating around the impeller, the holder may be adapted to hold the impeller within a distance which is smaller than the largest diametric size of the impeller from the building component. When a cross-flow impeller, in the above described manner, is operated in close vicinity to a surface, the turbulent airflow around the impeller is forced by the surface to form an air-stream to and from the impeller. This creates an inlet zone and an outlet zone of the blower to and from which zones air from the ambience is sucked from and blown into the ambience, respectively. Between the inlet zone and the outlet zone, pressure variations are likely to occur. Such variations are caused by instability in the air-stream going from the outlet zone towards the ambience. During the operation of the impeller, a high pressure in the outlet zone is being build up. When the pressure reaches a certain limit, the air which is blown from the outlet zone into the ambience creates a loop around the impeller towards the inlet . Since the flow direction in the zone between the inlet zone and the outlet zone is not very well defined, the flow between the inlet zone and the outlet zone is typically turbulent . This creates a sudden drop in the pressure difference between the inlet zone and the outlet zone resulting in a reduced efficiency of the impeller to exchange air with the ambience. In order to avoid instability in the pressure difference between the inlet zone and the outlet zone, it may be an advantage to separate these zones.

In the ventilating device according to the present invention, the impeller may be arranged in close vicinity to building components, e.g. to wall panels, pipes etc. As previously described, such building components may advantageously be used to replace the traditional components of the blower, e.g. a chassis for guiding the air-stream and also for replacing the stabilising member. As an example, the ventilating device may be attached in close vicinity to a wall panel and adjacent a pipe. The wall panel may thus be used for guiding the air-stream and the pipe may be used for separating the inlet zone from the outlet zone. Still, it may be an advantage to provide the ventilating device with a stabilizing member specifically designed for the purpose of separating the inlet zone from the outlet zone. Preferably, the stabilizing member is detachably connected to the ventilating device, e.g. to the holder. As an alternative, the stabilizing member can be attached directly to the heat exchanger, e.g. directly to a pipe or the stabilizing member could also be attached to a chassis holding the heat exchanger.

In order to improve the efficiency of the ventilating device, the air-gab between the member and the outer peripheral surface of the impeller should be kept relatively low and preferably below 1/3 of the largest diametric size of the impeller. The stabilizing member is preferably provided in a length substantially equal to the longitudinal length of the impeller to allow the member to cover the entire longitudinal length thereof.

The stabilizing member can under certain circumstances generate a whistling sound. In order to reduce this noise from stabilizing member, it has been found to be an advantage to allow a controlled amount of air to defuse from the outlet zone of the ventilating device to the inlet zone of the device. For that purpose, a stabilizing member comprising a material which is permeable to the air of the air-stream may advantageously be used. As an example, a porous material, e.g. a material with a porosity which allows the air to defuse through the material but which gives a certain resistance may be selected. The material could be arranged along a rim portion of the stabilizing member which faces towards the impeller. Alternatively, the entire member could be made from a porous material, e.g. from a material provided with a stiffness which allows the material in a sel -supporting manner to maintain its shape. The porous material could be made from PPI or PVC or any similar plastic materials which have been foamed to form a porous spongy body.

According to a preferred embodiment of the invention, the holder and its fastening means are specifically adapted to hold the ventilating device against a heat exchanger. For that purpose, the fastening means may comprise one or more magnets capable of holding the ventilating device against a surface of a magnetically conductive material, e.g. steel. It may sometimes be an advantage to attach the ventilating device to a set of pipes, e.g. to pipes of a regular central heating installation. For that purpose, the fastening means may comprise a pair of semi-circular gripping elements adapted to grip a pipe, the elements forming a circular arc segment, preferably larger than 180 degrees .

The heat exchanger, e.g. the pipe(s) may be attached to the building via a heat exchanger or pipe chassis or similar housing. As an example, the chassis may comprise an extruded assembly profile, e.g. a profile made from aluminium. The profile could have fixation means for fixation of the heat exchanger or pipe (s) . In that way, the user may attach a chassis to the building, e.g. to a wall, a floor, a roof or similar building component and subsequently, the heat exchanger, e.g. a pipe is attached to the chassis.

Often, central heating installations comprises sets of two pipes, one pipe with water going from a boiler or similar heat exchanger towards a number of radiators and one returning the water from the radiators to the boiler or heat exchanger. Typically, the pipes are mounted to the building in parallel. The holder may therefore comprise a second pair of semi-circular gripping elements adapted to grip a second pipe, preferably a pipe which is running in parallel with the first pipe.

If one of the gripping elements connects the holder more strongly to the pipe than the other one of the gripping elements, the most strongly connected pipe can function as a hinge pin allowing the ventilating device to be pivoted away from the other pipe or away from other building components, e.g. for cleaning purposes.

Sometimes, finned pipes are used as heat exchangers in central heating installations. For the purpose of attaching the ventilating device to a finned pipe, the inner surface of the gripping elements may have fins adapted to engage corresponding fins of such a finned pipe.

If the ventilating device is used for ventilating a cooling installation, e.g. for ventilating one or more pipes for a cooling medium, it may be an advantage to provide attachment means for attaching a tray for collecting a condensed liquid from such pipes or from a similar heat exchanger. The tray may be attached to the holder or the tray may be formed as an integrated part with the holder. Furthermore, the tray could be formed as an integrated part of the stabilizing member. As an example, the stabilizing member could be made with a cross-sectional shape forming an air-guide for the heat- exchanger, e.g. in the form of a plate pressed or moulded into a shape serving to guide the air across the heat- exchanger. The tray could be provided with a surface capable of absorbing the condensed liquid, e.g. a surface of a spongy material or a surface comprising a hydrophilic polymeric material, clay, a ceramic material or any similar material. Moreover or alternatively, the tray could have a drain for draining the condensed liquids into a place of disposal. Moreover, the tray could be provided with a draining pipe for leading away a condensed liquid and at least one opening for letting the condensed liquid into the pipe. The draining pipe could be subject to a pressure which is lower than the pressure of the ambient atmosphere. This will allow the condensed liquid to be led away by suction. The opening in the pipe could be made as a longitudinally extending slot at the top part of the draining pipe. When the pipe is arranged in the tray, it will remove the water by suction along the entire length of the slit. Alternatively, the pipe could be made from a porous material or the pipe could have a plurality of small holes.

The tray could also be formed as an evaporator, e.g. with a surface which has been enlarged by the provision of ribs, holes or similar uneven surface structure.

The holder could also be provided with attachment means for attaching an electrical motor to the ventilating device for driving the rotation of the impeller. The holder could also be formed as a stator part of such a motor.

The holder could also have attachment means or for attaching a shield to the ventilating device. Most preferably, such a shield should be formed so that it can be attached flexibly to the ventilating device to cover a part of the impeller which is exposed in a specific setup of the ventilating device. The shield could also form an integrated part of the holder, but in that case, the shield should preferably be formed from a flexible material allowing the user to attach the ventilating device to a building component and subsequently to reshape or in similar way to adjust the shield to match the specific purpose. In a similar way, a sound shield or a decorative shield or even a power supply for the electrical motor could be connectable or integrated into the holder. The holder, impeller or any other part of the ventilating device may further comprise solar cells for generation of power for driving the rotation of the impeller. Furthermore, the ventilating device may comprise a control circuit which is capable of controlling the rotational speed or at least to turn the rotation of the impeller on or off based on a measured temperature compared with a desired temperature setting.

In order to protect the ventilating device from overheating, e.g. in connection with attaching of the ventilating device to a heat exchanger, the device may comprise a layer of a thermally insulating material arranged to reduce thermal convection between the heat exchanger and the impeller, e.g. arranged between the heat exchanger and the holder or between the holder and the motor driving the impeller.

In order to allow a better control of the exchange of thermal energy between a heat exchanger, e.g. a set of pipes, and the surrounding atmosphere, the ventilating device may comprise an isolating shield for partly isolation of a heat exchanger connected to the ventilating device. The isolation could be made with a set of openings allowing the stream of air generated by the impeller to establish forced convection between the heat exchanger and surrounding atmosphere, i.e. the holes could be arranged across the air-stream so that the air-stream blows air through the isolating layer across the heat exchanger. If the holes are relatively small, whey will limit natural convection between the heat exchanger and surrounding atmosphere. The shield could be integrated in or attached to the aforementioned heat exchanger or pipe chassis .

According to a second aspect, the present invention relates to a holder for a ventilating device and with any of the features as described for the holder of the ventilating device described under the description of the first aspect of the invention.

According to a third aspect, the present invention relates to a stabilizing member for a cross-flow blower, the stabilising member forming an oblong member to be arranged in parallel to a rotational axis of a cross-flow impeller with a rim portion arranged in close vicinity to the surface of the impeller, the rim portion being made from a material which is permeable to an air-stream generated by the impeller. The member or at least a part of the member, preferably a rim portion thereof, to be arranged in close vicinity to the impeller could be made from a material selected from the group consisting of PPI, PUR, PU and PVC. As an example, the member could comprise PPI 15-40-60 which is an open pored material allowing the air to defuse through the material .

The member could in general be made with any of the features described for the stabilising member of the ventilating device of the first aspect of the invention, in particular, it is desirable to make the member from a material which causes a flow resistance to the air permeating the stabilizing member.

According to a fourth aspect, the present invention relates to a method of generating a forced stream of air wherein an cross-flow impeller is fastened to a building component so close to the building component that a surface of the building component forms an air guiding surface for guiding air to and from the impeller and thus establishes an inlet zone and an outlet zone of the impeller.

Detailed description of the invention

In the following, a preferred embodiment of the invention will be described in further details with reference to the drawing in which:

Fig. 1 shows cross sectional view of a ventilating device according to the invention mounted to a building component, Fig. 2 shows the ventilating device of Fig. 1, wherein a stabilizing member is attached for improving the efficiency of the ventilator,

Fig. 3 shows the ventilating device with a holder for holding the device to a set of two pipes, e.g. pipes of a central heating installation in a building,

Fig. 4 shows the ventilating device of Fig. 3, wherein the impeller has been rotated away from the building component, one of the pipes serving as a hinge element for that purpose,

Fig. 5 shows a cross sectional view of the ventilating device with a stabilizing member having an edge of a porous material,

Figs. 6 and 7 show two different embodiments of the stabilizing member attached in a regular cross-flow ventilator, and

Fig. 8 shows a cross sectional view of a heat exchanger or pipe chassis to which the ventilating device is attached.

As best seen in Fig. 1, the ventilating device according to the present invention comprises an impeller 1, e.g. made from a plurality of longitudinally extending profiles 2, e.g. made from aluminium or any similar metal or plastics material. The profiles are assembled via circular disks 3 provided with slots for receiving the profiles there through. The impeller may alternatively be made by injection moulding and it could even be made in a single injection into a mould. Preferably, the impeller is made with a longitudinally centre hole 4. The impeller is, at a first end portion, and alternatively at both ends, fastened to a building component, in this case a wall panel 6, via one or more holders. Since the holder of the impeller does not interfere with the generated air-stream, the ventilating device can be mounted in any direction, and the direction of the air-stream from the impeller can be established subsequently, e.g. by using the wall panel 6 as a guiding surface for the air-stream.

In Fig. 2, the ventilating device is fitted with a stabilising member 21. The stabilizing member extends in the entire length of the impeller and in close vicinity to the outer peripheral surface thereof. During use, the stabilizing member stabilizes the air-stream by separating an inlet zone of the ventilating device from an outlet zone of the ventilating device. In this respect, it can be seen, that the stabilizing member of Fig. 2, is attached adhesively to the outer surface 22 of the holder. In this way, the user of the ventilating device may attach the stabilizing member after the ventilating device has been affixed to the building component and to any desired location on the ventilating device. In other words, the user may define the inlet zone and the outlet zone, e.g. by using the building component for guiding the air, and subsequently by arranging the stabilizing member on a corresponding place on the holder.

In Fig. 3, the ventilating device is fitted with a holder which is split into a first holding part 31 capable of gripping a set of two pipes 32, 33. The pipes could form a part of a regular central heating system and thus carry a heating or cooling medium. For gripping the pipes, each of the disclosed holders is fitted with two sets of gripping elements 34, 35 (best seen in Fig. 4 as 41, 42) adapted to grip a pipe. The gripping elements form circular arc sections which - at least in the case of one of the elements - advantageously could be a circular section larger than 180 degrees. The elements are made from a material which allows the elements to flex in and out during the mounting of the holder onto the pipes. As shown, the holder is made to grip two adjacent pipes. On one side of the two pipes, the first holding part extends in a direction visualised by the arrow 36 substantially perpendicularly to a longitudinal direction of both of the pipes and terminates in fastening means 37 for fastening a stabilizing member 38 to the first holding part. The stabilizing member is attached to the first holder at a first one 39 of its two widest surfaces 39, 40 arranged in an angle, α. The angle α being in the range between 20-60 degrees to a plan extending through the longitudinal centre axes of both of the pipes. A second holding part 41, holding the impeller 42, is attached to the opposite surface of the stabilizing member. In an alternative embodiment, the first and second holding members and/or the stabilizing member could be made in one piece. As shown in Fig. 4, this specific arrangement of the impeller in relation to the two pipes offers the advantage that the impeller, e.g. for the purpose of removing dust and dirt from the pipes, can be pivoted away from the building component, in this case from the wall panel. During the pivoting of the impeller, one of the pipes functions as a pivoting pin and forms the axis of rotation. Accordingly, one of the two gripping elements may be adapted to grip the pipe more strongly than the other one of the two gripping elements. Accordingly, one of the elements may form an arc section larger than 180 degrees while the other one forms an arc section less than 180 degrees. As shown in Fig. 4, the first holding part of the holder may grip the pipe on locations fitted with sleeves 43. The sleeves could be made from a material which is durable to the scratching impact of the gripping elements while they engage the pipe and thus serve for the protection e.g. of a painted pipe which could have been scratched.

In Fig. 5, a ventilating device is sketched in a cross sectional view. The device comprises a holder which carries a tray 51 for collecting dripping liquids, e.g. condensed liquids from cooling pipes 52, 53. A stabilizing member 54 with a porous material 55 is attached to a rim portion 56 of the tray. The stabilizing member separates an inlet zone 57 from an outlet zone 58 of the ventilating device. Due to the porosity of the material, air from the outlet zone can defuse through the stabilizing member, or at least through a rim portion thereof, to the inlet zone.

In Figs 6 and 7, two different stabilizing members 61, 71 have been shown when fitted to a regular cross-flow blower of the kind fitted with a housing 62, 73 forming a flow channel for guiding the air-stream. The stabilising member 61 is made from a material which is self-supporting, i.e. it has a stiffness which allows the material to be arranged in close vicinity to the impeller without any stiffening members attached thereto. The stabilizing member 71, on the other hand, is attached to a stiffening member 72. Fig. 8 shows a heat exchanger or pipe chassis, to which the ventilating device is fitted with an isolating shield 81 for partly insulation of a heat exchanger, e.g. sets of pipes 82, 83 connected to the ventilating device. The shield forms openings 84, allowing passage for an air- stream generated by the impeller across the pipes. At the same time, the shield strongly limits natural convection of heat between the surroundings and the pipes when the ventilating device is switched off. It is thus possible effectively to control the energy exchanged between the pipes and the surroundings by controlling the power to an electrical motor driving the impeller. The stabilising member 85 is connected directly to the shield, whereas the impeller 86 could be connected to a neighbouring building component, e.g. directly to a wall panel 87 or similar.

Claims

1. A ventilating device comprising:

— a cross-flow impeller extending in a longitudinal direction around an axis of rotation and being adapted to generate an air-stream extending from the ambience towards an inlet zone, from the inlet zone to an outlet zone and from the outlet zone towards the ambience, and

- a holder comprising fastening means adapted to connect the impeller to a building component,

characterized in that the holder connects the impeller to the building component at least substantially without interfering with the generated air-stream so as to allow the direction from the inlet to the outlet to be selected independently upon the direction of the holder in relation to the building component.

2. A ventilating device according to claim 1, wherein the holder forms a part of a pipe holder for holding pipes .

3. A ventilating device according to claim 1 or 2, wherein the holder is adapted to hold the impeller in one out of two axially disposed end-portions of the impeller at least substantially without hindering passage of an air-stream extending into and out of the outer peripheral surface of the impeller in a direction perpendicular to the longitudinal axis of the impeller.

4. A ventilating device according to any of the preceding claims, wherein the holder is adapted to hold the impeller within a distance which is smaller than the largest diametric size of the impeller from the building component so as to allow the building component to function as a guide for guiding the generated air stream.

5. A ventilating device according to any of the preceding claims, further comprising a stabilizing member arranged to at least partly separate the inlet zone from the outlet zone.

6. A ventilating device according to claim 5, wherein the stabilizing member is arranged to form an air-gab between the member and the outer peripheral surface of the impeller, the air-gab being smaller than 1/3 of the largest diametric size of the impeller.

7. A ventilating device according to claims 5-6, wherein the member comprises a material which is permeable to the air of the air-stream.

8. A ventilating device according to claim 7, wherein the material is selected with a porosity which causes a flow resistance to the air permeating the stabilizing member.

9. A ventilating device according to any of claims 7-8, wherein the material is arranged along a rim portion of the member, said rim portion facing the outer periphery of the impeller.

10. A ventilating device according to any of claims 2-8, wherein the stabilizing member is detachably fixed to the holder.

11. A ventilating device according to any of claims 2-9, wherein the stabilizing member extends substantially along the entire peripheral surface of the impeller.

12. A ventilating device according to any of the preceding claims, wherein the fastening means comprises a least a first pair of semi-circular gripping elements adapted to grip a first pipe, the elements forming a circular arc larger than 180 degrees.

13. A ventilating device according to claim 12, wherein the fastening means further comprises a second pair of semi-circular gripping elements adapted to grip a second pipe, the first and second pairs of gripping elements being arranged to grip two adjacent pipes having parallel longitudinal axes .

14. A ventilating device according to claim 13, wherein one of the gripping elements is adapted to connect the holder more strongly to one of the pipes than the other one of the gripping elements, so as to allow the more strongly connected pipe to be used as a hinge pin for pivoting the ventilating device away from the other one of the pipes .

15. A ventilating device according to claim 12 or 13, wherein the holder is adapted to connect the impeller to the pipe(s) with its longitudinal direction at least substantially parallel to the longitudinal axes of the pipes .

16. A ventilating device according to claim 12-15, wherein an inner surface of the gripping elements is provided with fins adapted to engage corresponding fins of a finned pipe .

17. A ventilating device according to any of the preceding claims, further comprising attachment means for attaching a tray for collecting condensed liquid from a heat exchanger.

18. A ventilating device according to claim 17, wherein the tray is an integrated part of the holder.

19. A ventilating device according to claims 17-18, wherein the tray is provided with a surface capable of absorbing the condensed liquid.

20. A ventilating device according to claims 17-19, wherein the tray comprises a drain for draining the condensed liquids into a place of disposal.

21. A ventilating device according to claims 17-20, further comprising a draining pipe for leading away a condensed liquid and at least one opening for letting the condensed liquid into the pipe.

22. A ventilating device according to claim 21, wherein the pressure in the draining pipe is lower than ambient pressure, so as to allow a condensed liquid to be led away by suction.

23. A ventilating device according to claim 21 or 22, wherein said at least one opening comprises a longitudinally extending slot at the top part of the draining pipe .

24. A ventilating device according to claims 17-23, wherein the tray is formed as an evaporator with a surface structure offering an enlarged evaporation surface for evaporating the condensed liquid.

25. A ventilating device according to any of the preceding claims, further comprising attachment means for attaching a motor for forced rotation of the impeller around the axis of rotation.

26. A ventilating device according to claim 25, wherein the motor is an electrical motor and wherein a stator part of the motor is an integrated part of the holder.

27. A ventilating device according to any of the preceding claims, further comprising attachment means for attaching a shield for shielding the impeller.

28. A ventilating device according to claim 27, wherein the shield is an integrated part of the holder.

29. A ventilating device according to claims 26-28, further comprising attachment means for attaching a noise reducing cover over the motor.

30. A ventilating device according to claim 29, wherein the shielding cover is an integrated part of the holder.

31. A ventilating device according to any of the preceding claims, wherein the fastening means comprises a magnet.

32. A ventilating device according to any of the preceding claims, further comprising attachment means for attaching a power supply unit to the holder.

33. A ventilating device according to claim 32, wherein the power supply is an integrated part of the holder.

34. A ventilating device according to any of the preceding claims, comprising a layer of a thermally insulating material arranged to reduce thermal convection between the heat exchanger and the impeller.

35. A ventilating device according to any of the preceding claims, further comprising insulation for partly insulation of a heat exchanger connected to the ventilating device, the insulation being adapted to allow the steam of air to establish forced convection between the heat exchanger and surrounding atmosphere and to limit natural convection between the heat exchanger and surrounding atmosphere .

36. A ventilating device according to claim 35, wherein the insulation envelopes at least a part of the heat exchanger, the insulation being provided with a through passage allowing the air stream to flow across the heat exchanger through the insulation.

37. A holder for a ventilating device according to any of claims 1-36.

38. A holder according to claim 37, formed to attach the ventilating device to a heat exchanger.

39. A holder according to claim 37, formed to attach to fastening means for a heat exchanger.

40. A holder according to claim 38 or 39, wherein the heat exchanger is a pipe.

41. A holder according to claim 40, formed to attach the ventilating device to a set of two pipes.

42. A holder according to claim 41, formed to attach the ventilating device to a set of two pipes having substantially parallel longitudinal axes, the holder being formed to hold the impeller of the ventilating device with its longitudinal axis substantially in parallel to the longitudinal axes of the pipes.

43. A holder according to claim 38 or 39, wherein the holder is formed to allow the ventilating device to be pivoted around the heat exchanger.

44. A stabilizing member for a cross-flow blower, forming an oblong member to be arranged in parallel to a rotational axis of a cross-flow impeller with a rim portion arranged in close vicinity to the surface of the impeller, the rim portion being made from a material which is permeable to an air-stream generated by the impeller.

45. A stabilizing member according to claim 44, made from a material selected from the group consisting of PPI, PUR, PU, PVC.

46. A stabilizing member according to claims 44-45, wherein the material is selected with a porosity which causes a flow resistance to the air permeating the stabilizing member.

47. A stabilizing member according to claims 44-46, wherein the stabilizing member comprises attaching means of detachably fixing of the member to a cross-flow blower.

48. A method of generating a forced stream of air wherein a cross-flow impeller is fastened to a building component so close to the building component that a surface of the building component forms an air guiding surface for guiding air to and from the impeller and thus establishes an inlet zone and an outlet zone of the impeller.