EP1261807A1

EP1261807A1 - Air conditioning apparatus

Info

Publication number: EP1261807A1
Application number: EP01910303A
Authority: EP
Inventors: Gunnar Berg; Dan ÖRTENGRAN
Original assignee: PM-Luft AB; PM Luft
Current assignee: PM-Luft AB; PM Luft
Priority date: 2000-03-09
Filing date: 2001-03-06
Publication date: 2002-12-04
Also published as: SE0000788L; SE0000788D0; AU2001237874A1; AU2001237873A1; WO2001066952A1; NO20024282L; NO20024282D0; SE522560C2; WO2001066953A1

Abstract

The present invention relates to an air conditioning plant comprising a fan with double inlet (2), whereby the apparatus comprises a space (6) which is substantially quadratic in a cross-section perpendicular to the fan shaft (3); that the fan (2) which is a radial fan having blades turned backward, is centrally placed in said space, at least in relation to three of its sides radial to the fan shaft, and is provided with a diffuser formed between diffusor sheets (5) having a diameter being at least 50 % larger than the diameter of the fan impeller.

Description

TITLE

AIR CONDITIONING APPARATUS

DESCRIPTION Technical field

The present invention relates to an air treatment apparatus comprising a radial fan with double inlet.

Background of the invention There are different types of fans present in air treatment apparatuses. The most common one is radial fan with double inlet provided with a helically shaped fan house. Other types are axial fans and chamber fans.

Radial fans with double inlet are built as free standing units. It is common that the fan deliverer delivers these units to different producers of air treatment apparatuses for further installation. The installation measures can vary. Two different types of fan impellers are used in these fans. Fan impellers having blades bent forward, and fan impellers having blades bent backward. Fan impellers having blades bent backward become more and more common due to a better consciousness of energy issues and one requires a higher yield. Fans having blades bent forward have, however, that advantage that they can be manufactured more compact than fans having blades bent backward with regard to a given air flow.

One has high requirements on isolation of vibrations when it comes to a fan unit. To obtain a good isolation space is required between the fan unit and the housing of the apparatus. The height of the fan unit is thereby considerably reduced as space is required both above and under the unit to provide a good isolation.

Radial fans with double inlet having a helical fan house have a high and uneven outlet speed. This requires a straight channel upstream of the fan to minimize systemic losses. The fan allows however different outlet directions, forward, upward, and downward but requires a large space due to the required straight channel after the fan house. The space in fan rooms is, however, normally relatively small and thus one is forced to add an channel bend or another disturbing means such as channel silencer close to fan outlet providing an increased pressure drop as a consequence in spite of the different outlet directions. With regard to axial fans the situation is even more troublesome when only forward exists as outlet direction. Furthermore there is required some sort of flow director not to obtain a rotating flow which gives still higher pressure drop in the subsequent channel system and components.

The space after the fan impeller in a chamber fan can be regarded as a pressure box. The outlet area can be made large and any disturbance, such as a channel bend can be mounted directly at the outlet without any increased pressure drop.

Radial fans with double inlet having a helical fan house and axial fans have higher efficiency than chamber fans if the subsequent channel system is not provided with any disturbance close to the outlet and are thus desired per se.

Radial fans with double inlet are normally provided with a belt transmission.

Chamber fans are advantageously construed direct driven i.e., without any transmission losses.

DE-A-2,253,309 describes a single sucking radial fan which via a nozzle in a wall sucks air into the fan and then throws the air radially into a house provided with guiding plates in its corner to provide an effect similar to that one obtained in a helical fan house. The fan as such is asymmetrically placed in the fan house to increase the outlet area. Such a fan can at most obtain the same performance as a double sucking fan in a half-house. Performance of double sucking fan in half-house will be described in the technical part below. According to the description of said patent the construction is compromise between size and efficiency, and in reality a simplification to reduce production costs. The construction has its origin in a helical house where radiuses have been replaced by three straight lines (the fan walls radially to the fan impeller).

US-A-4,798,518 and US-A-5,547,339 describe a fan unit having a single sucking radial fan provided with an inlet nozzle. GB-A-575,909 describes a pure radial fan with double inlet without any diffusor but having a solidly added helical house as outlet for the air. The problem using this type of design is that the air speed is high and uneven. The inlet of the fan is designed as nozzles to guide the air.

In the Nordic countries one normally provides an air treatment apparatus with some type of heat reclaiming means. One of the most common ones is a rotating heat exchanger. It has the highest temperature yield. A common type of apparatuses are the so called unit apparatuses. These apparatuses are construed with regard to rotating heat exchangers. The cross-section of the apparatus is quadratic and in height, split into two air streams, to and fro streams. The advantage using these apparatuses are that they have an even width and are compact. The same advantages are achieved using a module apparatus if it is similarly construed If all apparatuses can be built as module apparatuses this means a considerable reduction of the number of articles to be produced, as well as the fact the building constructor well knows the measures which will be due.

The technical problem

In order to obtain flexibility with module and air conditioning units such apparatuses parts are construed which serves an air stream with identical cross-sections. Hereby disadvantages occur for the module apparatus with regard to the unit apparatus as one is forced to split the quadratic cross-section into two identical air streams. This provides for a low height in relation to the width of the fan insert. One is forced to reduce maximum air flow , alternatively increase air flow speed through the fan.

In order to obtain a low pressure drop and to minimize sound creation channel systems are construed for low air flow speeds, normally less than 6 m/s. When radial fans with double inlet having helical fan houses are used, some type of transmission to the desired larger channel dimension is inserted.

Inserts with a radial fan with double inlet having helical fan house have to be produced for different outlet directions. This leads to an increased number of articles in the production. In a radial fan with double inlet having helical fan house sound is created, on one hand as noise, on the other hand as a tone. Sound is created i.a., when the fan blades pass the most narrow sector of the fan house. This sector is present at the air former which breaks the air flow around the fan impeller against the outlet. There are different shapes of more or less complicated air formers to reduce the tone part, the so called blade frequency. Humans recognize tones more than noise. For this reason the blade frequency is extra annoying. The blade frequency occurs still more at axial fans.

Description of the present invention It has now surprisingly turned out possible to be able to meet these requirements and to solve outstanding problems by means of the present invention which is characterized in that the apparatus comprises a space which is substantially quadratic in a cross-section perpendicular to the fan shaft; that the fan which is a radial fan having blades turned backward, is centrally placed in said space, at least in relation to three of its sides radial to the fan shaft, and is provided with a diffusor formed between diffusor sheets having a diameter being at least 50% larger than the diameter of the fan impeller.

The term substantially quadratic means here that the sides of the quadrate can vary ±10-20%

The nominal diameter of the fan impeller is hereby measured over the largest diameter of the radial fan blades.

The term diffusor means a part of a channel or apparatus which enlarges in the direction of the flow and serves to re-establish speed energy as pressure energy (Technical Nomenclature Centre publication No. 69, page 24, (1978)).

The fan is so integrated in the apparatus part that it, with regard to its function to transport air can be regarded as one unit. The fan impeller is preferably a radial fan impeller with double inlet. The fan impeller is placed in a ring diffusor having a diameter which is at least 50%) larger than the diameter of the fan impeller. By integrating a fan into the plant part there is created more space for a larger diameter of the fan impeller. This also calls for the fact there is space to place the fan impeller in a ring diffusor. Using the diffusor dynamic pressure is recovered as static pressure. This leads to less pressure losses and thereby the yield increases.

The dimension of the fan outlet can be made large to obtain a low air flow speed. The fan is insensitive to normal disturbances after the fan outlet, i.e., channel bend or silencer can be mounted close to the outlet without any increased pressure drop.

As whole construction can be seen as a compact pressure box the outlet opening can be placed as desired without influencing the fan construction as such. The number of articles in a production can be minimized. There is also a possibility to use several, simultaneous outlet directions which is a novelty per se.

The lack of any air former provides for a reduced sound level, and then in particular with regard to the blade frequency. Demands on vibration isolation can be easily met using the present fan.

The term "that the fan which is a radial fan having fan blades turned backward, is centrally placed in said space, at least in relation to three of its sides radial to the fan shaft", means that the fan is centrally placed in a way given in the drawing below, but in some case a displacement towards or from the outlet side may occur.

The present invention will be described more in detail in the following with reference to the accompanying drawing, however, without being restricted thereto, and wherein

FIG. 1 shows a module unit seen from the front;

FIG. 2 shows the embodiment according to FIG. 1 seen in perspective view;

FIG. 3 shows the embodiment of FIG. 1 in a cross-section perpendicular to the front view of FIG. 1; and

FIG. 4 shows a detail of the engine mounting.

FIG. 5 and 6 show diagrams showing effect and efficiency comparisons. 1 denotes a module unit in general, in which a radial fan with double inlet 2 is arranged onto a shaft 3 connected to a belt transmission 4. The radial fan with double inlet 2, which is provided with blades 8 bent backward, is provided with a diffusor created between two diffusor sheets 5, suitably circular discs whereby the diffusor has a diameter which is at least 50% larger than the diameter of the fan, and preferably 55 to 80 % larger than the diameter of the fan impeller. Outside the diffusor discs 5 there are inlet sheets 9 which are isolated from the inlet wall 25 by means of sleeves 21 and, further there are supply air channels for feeding the fan, which channels end in an inlet opening around the shaft 3 of the radial fan with double inlet. The fan 2 is centrally placed in a space 6 which has a quadratic cross- section in a plane peφendicular to the shaft 3 of the radial fan with double inlet 2. In any direction out from this space there is an outlet opening 7 which normally takes the whole side of the unit 1 in front of the radial fan with double inlet 2. The size of the opening 7 can of course be varied upon demand. A channel tube (not shown) can be connected directly to the opening 7, whereby such a channel tube can be bent directly if the space thus requires.

The fan 2 is driven by a motor 8 which transfer the rotation to the fan 2 via a belt transmission connected to the shaft 3 of the fan 2.

By means of the quadratic cross-section of the space of the radial fan with double inlet a stable flow is created in the remainder of a ventilation system.

In a particular embodiment of the invention there is obtained an engine support for radial fan with double inlet in air conditioning plants. For the fan part of an air conditioning plant there are a number of construction requirements, such as that the fan part, i.e., the housing comprising the complete fan with driving unit shall be as short as possible due to the normally existing lack of space to the air conditioning plant; the fan part shall be possible to inspect from alternative sides seen in the direction of the air flow; the fan part shall be belt driven to be able to vary the size of the motor and rotation speed of the fan; fan parts shall be able to be mounted vertically; engine support with its engine is not allowed to influence the inlet flow of the fan aerodynamically; the fan part shall independent of engine support be given a possibility of different outlet directions; fan part with motor shall be vibration isolated; the engine support shall be adaptable to different engines; the engine support shall allow a careful alignment of belt transmission; the engine support shall allow a simple inspection and maintenance of the fan part; and the fan part shall be able to be cleansed.

By tradition the engine is placed on or between beams whereby the beams are vibration isolated on their insides towards the housing of the plant, most often closest to its bottom. Usually, the engine is placed upstream the fan which provides for a simple and rugged construction whereby, however, the drawback is that the fan part becomes longer. Alternatively, the engine can be placed at the side of the fan, but this can only be done when the fan part has enough width. The problem is hereby to make the construction enough torsi onal stiff without increasing the costs of the construction. At a vertical mounting of the fan part a torsional moment exists due to the weight of the fan insert as the vibration isolation is adapted to a horizontal mounting between beams and the bottom of the plant housing.

If one places a substantially large engine beside the fan part an unsymmetric air flow is created which gives raise to a vortex at the inlet of the fan, which inlet is placed on the engine side, which leads to a reduced fan capacity.

Further the shift of an engine of a fan part an environmental problem as heavy engines shall be placed therein with precision in narrow spaces. In particular fan parts of radial fans with double inlet are difficult to cleanse due to beams and hollow profiles in the building of the plant.

The problem has been solved by placing the engine 8 on a foldable bridge 10. The bridge 10 is thereby mounted on a support 11 comprising two beams 12 running in parallel, which beams 12 at their lower ends 13 are pivotally, rotatably arranged to a holder 14 and at its upper ends 15 are releasably mounted to a holder 16. From a production technical point of view the holders 14 and 16 are identical whereby the mounting of the beams 12 are carried out in different ways. The holders 14 and 16 comprise in this embodiment on one hand a hole 17 for a pivotal, rotational mounting of a journal 18 through the beams 12, on the other hand a slot 19 for tensioning the belt between the engine 8 and the belt disc 4. The engine 8 is thereby secured to the adjustment slots 19 via securing screws 20 running in said slots 19 and which screws are fastened to the upper ends 15 of the respective beams 12. By eliminating the securing screws 20 the engine can be folded forward passing the fan unit 2. The holders 14 and 16 are, in turn, fixedly mounted to a tubular support 11 arranged to receive a torsional moment created by the engine 8 during work. The tubular support 11 is further arranged to the fastening beams of the air conditioning plant via dampening attachments 22 to eliminate vibrations to its support, such as a building.

Below a comparison between a fan with diffusor according to the present invention and a fan with half-house will be shown.

The applicant has since 1997 produced and sold a radial fan with double inlet in accordance with Fig. 5, i.e., a fan which very much reminds of the single fan shown in DE-A-2,253,309 with regard to geometric placement of the fan into the fan room. The fan impeller is circumvented to 180o by a logarithmic helix. The helix is a perforated steel sheet having sound absorbing material placed on the rear side. The fan room has its right side of Fig. 5 completely open, which side forms the outlet. The fan is here denoted a fan with half-house.

In a helical house dynamic pressure is recovered as static pressure. If a fan has been made without any helical house dynamic pressure will be lost, i.e., the yield is reduced. The quadratic house described in DE-A-2,253,309 can, as understood from the geometry, at most obtain the same performance as a fan with half-house in the following comparisons.

In Fig. 6 a comparison is shown where the plant housing restricts the fan size. One can easily note that a fan having a diffusor provides for a higher air flow rate which means that a smaller plant housing can be used in narrow spaces. The desire late years with regard to air conditioning plants is to reduce the pressure drop in channel systems and plant to minimize energy consumption. For plant fans this means that one strives towards the right side of the fan graph. It is then interesting if one in that part can increase the yield. In the fan diagram the working line most common today has been drawn. It shall be noted that a fan works at the same aerodynamical working point along a working line which means that the yield is maintained, however, the rotational speed of the fan is varied. Using the new construction an increase of the yield of 9 % is obtained, which in the present situation provides for an effect reduction of 13 %. In Fig. 7 the fan variants are compared at the same nominal diameter of the fan impeller. The top yield has, using the present construction, increased with plus 2 %. The fan with diffusor has then been measured in a smaller plant housing which influences the yield negatively compared to a freely mounted fan.

Claims

1. Air conditioning plant comprising a fan with double inlet (2), characterized in that the apparatus comprises a space (6) which is substantially quadratic in a cross-section peφendicular to the fan shaft (3); that the fan (2) which is a radial fan having blades turned backward, is centrally placed in said space, at least in relation to three of its sides radial to the fan shaft, and is provided with a diffusor formed between diffusor sheets (5) having a diameter being at least 50% larger than the diameter of the fan impeller.

2. Air conditioning plant according to claim 1, characterized in that the diameter of the diffusor is 55 to 80 % larger than the diameter of the fan impeller.

3. Air conditioning plant according to claims 1-2, characterized in that the space (6) has an outlet opening (7) which substantially corresponds to the width of the fan and the diameter of the diffusor.

4. Air conditioning plant according to claims 1-2, characterized in that the space (6) has an outlet opening (7) which substantially corresponds to the width of the fan but is less than the diameter of the diffusor.