EP2286646A1

EP2286646A1 - Cooling plate for a frequency converter and compressor using said cooling plate

Info

Publication number: EP2286646A1
Application number: EP09742450A
Authority: EP
Inventors: Gianni Candio
Original assignee: Refcomp SpA
Current assignee: Refcomp SpA
Priority date: 2008-05-09
Filing date: 2009-05-08
Publication date: 2011-02-23
Also published as: ITVI20080106A1; CN102017827A; WO2009136277A1; CN102017827B

Abstract

The invention concerns a cooling plate (6; 30) for a frequency converter (4), comprising a surface (6a) suited for coupling with the frequency converter (4) and a duct assembly (10) that develops between an inlet opening (7) and an outlet opening (8; 32), between which it is possible to identify an outflow direction (V) of a cooling fluid along the duct assembly (10). The surface area of the cross section of the duct assembly (10) increases along the outflow direction (V).

Description

"COOLING PLATE FOR A FREQUENCY CONVERTER AND COMPRESSOR

USING SAID COOLING PLATE".

DESCRIPTION

The present invention concerns a cooling plate particularly suitable for coupling with a frequency converter.

The invention also concerns a compressor fed by a frequency converter and equipped with the above mentioned plate for cooling the converter itself.

As is known, a frequency converter is an electronic device that makes it possible to control the number of revolutions of an electric motor, A converter is often used, for example, for feeding the motors of motor pumps or compressors, whose performance can thus be adapted to the user's needs.

It is also known that a frequency converter develops a certain quantity of heat during its operation and that, therefore, it must be properly cooled in order to avoid malfunctions and any possible damage to its electronic components. According to the known art, the above mentioned cooling effect is obtained by means of a heat dissipation element placed in contact with the hottest electronic components of the converter, from which it takes the heat in order to transfer it to a cooling fluid with which the heat dissipation element comes into contact. In the case of compressors, in particular of the volumetric compressors used in cooling systems and similar systems, the heat dissipation element is often cooled by the same fluid that flows in the cooling system and in the compressor itself.

According to a known construction form, the above mentioned heat dissipation element is a coil pipe with uniform diameter, in which said cooling fluid circulates and which is arranged in contact with the hot components of the converter.

According to a construction variant of the invention, a dissipation plate is added, interposed between the coil and the converter in order to increase the heat exchange surface between the two elements.

The above mentioned variant is used, for example, in the converters associated with cooling systems.

In this case, the cooling fluid circulating in the cooling system is used also to cool the heat dissipation element. The cooling fluid is drawn downstream of the condenser in the liquid state and is conveyed to the coil of the heat dissipation element, along which it evaporates removing heat from the converter.

The above mentioned evaporation allows more efficient heat removal, making it possible to reduce both the overall fluid flow rate required and the overall dimensions of the coil.

Nonetheless, the known coil described above has limited heat exchange efficiency, and makes it necessary to take from the cooling system a correspondingly high cooling fluid flow rate.

This high flow rate poses the drawback that it negatively affects the overall efficiency of the cooling system.

Furthermore, since the diameter of the coil pipes must be proportional to the flow rate, there is a further drawback represented by the fact that a high flow rate leads to an increase in the overall dimensions of the coil itself.

The overall dimensions of the converter and of the relevant heat dissipation element generates a further drawback represented by the fact that it makes it difficult to install a converter in a pre-existing system that is not equipped with such a device.

The object of the present invention is to overcome all the above mentioned drawbacks that are typical of the known art. In particular, it is a first object of the invention to carry out a cooling plate for a frequency converter whose efficiency is higher than that of the known heat dissipation elements suited for analogous purposes.

It is also the object of the invention to construct a compressor with frequency converter whose overall dimensions can be compared to those of a compressor without converter and are in any case smaller than the overall dimensions of a compressor with converter of known type.

The objects described above are achieved by a cooling plate carried out according to the main claim.

The same objects are also achieved by a compressor carried out according to claim 14.

Advantageously, the increased efficiency of the plate that is the subject of the invention makes it possible to use a lower cooling fluid flow rate compared to the heat dissipation elements of known type capable of removing the same heat flow, which improves the overall efficiency of the system. Furthermore, advantageously, the lower fluid flow rate required makes it possible to reduce the size of the plate of the invention compared to other heat dissipation elements of known type having the same heat dissipation capacity. Therefore, to advantage, the cooling plate that is the subject of the invention is sufficiently compact to be integrated in the compressor together with the converter, so as to further reduce the overall dimensions of the assembly.

Still advantageously, the above mentioned integration makes it possible to reduce the complexity of the system in which the compressor is inserted. The compact size offers a further advantage, represented by the fact that the compressor of the invention can be used in existing systems and replace a compressor without converter, with no need to make major changes to the system.

The said objects and advantages, and others which will be highlighted in greater detail below, are illustrated in the description of a preferred embodiment of the invention and of a variant of the same, which are provided by way of non-limiting examples with reference to the attached drawings, wherein:

- Figure 1 shows an axonometric, partial section view of the compressor that is the subject of the invention;

- Figure 2 shows an axonometric view of the cooling plate that is the subject of the invention;

- Figure 3 shows an axonometric view of a detail of the cooling plate that is the subject of the invention;

- Figure 4 is a partial view of a cross section of the cooling plate of Figure 2 along plane IV-IV; - Figure 5 is a side view of a cross section of the cooling plate of Figure 2 along plane V-V;

- Figure 6 shows a plan view of the cooling plate shown in Figure 2;

- Figure 7 shows an axonometric view of a construction variant of the cooling plate that is the subject of the invention. The compressor that is the subject of the invention is shown in Figure 1 , where it is indicated as a whole by 1.

The compressor 1 comprises a case 2 containing an electric motor 3 fed by a frequency converter 4.

The electric motor 3 is operatively connected to compression means 5 which preferably but not necessarily comprise a pair of counter-rotating screws. The screws define a plurality of chambers 5a, each one provided with an inlet way and a delivery way, in order to contain an operating fluid to be compressed.

As is known, the screws are structured in such a way that, during their rotation, the volume of the chambers 5a decreases, thus compressing the operating fluid.

The above mentioned screw compressor 1 is known per se and widespread, especially in the field of refrigeration.

It is clear, however, that the invention can be applied to any other known type of compressor 1 like, for example, positive displacement compressors, reciprocating compressors, vane superchargers, centrifugal compressors, or any other type of compressor, provided that it is equipped with a motor fed by a frequency converter 4.

The compressor 1 comprises a cooling plate 6 provided with a coupling surface 6a in contact with the frequency converter 4, preferably at the level of the most delicate electronic components that develop the greatest quantity of heat.

The plate 6 comprises a duct assembly 10 for a cooling fluid which preferably but not necessarily is the same operating fluid that circulates in the compressor 1 .

This last condition is advantageous especially when the compressor 1 is included in a cooling circuit, since in this case the operating fluid of the circuit is particularly suited to remove heat from the plate 6.

In fact, the above mentioned fluid has a low temperature and, furthermore, its evaporation can be exploited to obtain the efficient cooling of the plate 6.

As shown in Figure 2, the above mentioned duct assembly 10 is developed between an inlet opening 7 and an outlet opening 8, which define an outflow direction V of the cooling fluid along the duct assembly 10.

Clearly, the above mentioned outflow direction V can take different directions along the duct assembly 10, following the more or less curvilinear trajectory defined by the duct assembly 10 itself.

According to the invention, the surface area of the cross section of the duct assembly 10 increases along the outflow direction V.

The surface area of the cross section of the duct assembly 10 preferably increases by discrete values along the outflow direction V. More precisely, and as shown in greater detail in Figures from 3 to 6, the duct assembly 10 comprises a plurality of rectilinear ducts 11 arranged side by side and preferably parallel, each one of which has uniform cross section. Advantageously, the above mentioned rectilinear ducts 11 can be carried out in a very simple manner, for example by drilling a monobloc body 17, as will be described below.

It is obvious, however, that in construction variants of the invention, not illustrated herein, the surface area of the cross section of the duct assembly 10 may increase continuously, and not discretely, along the outflow direction V. The rectilinear ducts 11 are preferably divided in three groups 12, 13, 14, arranged in series according to the outflow direction V, each one of said groups having an overall flow cross section larger than that of the preceding group. In particular, a first group 12 and a second group 13 are provided with the same number of ducts 11 , and a first end 12a of each duct of the first group 12 is connected to a first end 13a of a corresponding duct of the second group 13 by means of a corresponding first connection duct 15, one of which is entirely visible in Figure 3. The third group of ducts 14, instead, preferably but not necessarily comprises two of the above mentioned ducts 11, respectively arranged on opposite sides with respect to the ducts of the first group 12 and of the second group 13 altogether.

Obviously, in different construction variants of the invention not illustrated herein, the number of groups of ducts can be higher than three. It is also evident that in further construction variants of the invention one or more groups of ducts can have the same overall flow cross section, provided that there are at least two groups of ducts whose overall flow cross sections are different and increasing along the outflow direction V. Regarding the ducts of the third group 14, each one of them has a first end 14a connected, through a second connection duct 16, to a second end 13b of the ducts of the second group 13 opposite the corresponding first end 13a. Obviously, different construction variants of the invention not represented herein may comprise several second connection ducts 16, each one of which can connect each duct of the third group 14 to one or more ducts of the second group 13. It can be noted that in the figures, for the sake of simplicity, the ends 12a, 13a, 13b, 14a of the ducts 11 are indicated only once for each group 12, 13, 14, it being understood that such indication is repeated and is exactly the same also for the ends of the other ducts 11 of the same group. The above clearly shows that the duct assembly 10 has increasing overall flow cross section.

The increasing cross section makes it possible to optimize the speed of the cooling fluid in the various areas of the duct assembly 10 according to the state and specific volume of the fluid itself, taking in consideration the progressive evaporation of the fluid along the duct assembly 10.

In particular, the cross section of the duct assembly 10 can be defined in such a way as to force the fluid to flow at a fixed uniform or variable speed, in order to obtain in any case the maximum heat removal efficiency in each group of ducts 12, 13, 14. Therefore, the duct assembly 10 with increasing cross section gives the cooling plate 6 higher heat exchange efficiency compared to the heat dissipation elements of known type, thus achieving the object of the invention. Consequently, to advantage, the plate 6 of the invention requires a lower cooling fluid flow rate compared to the known heat dissipation elements, with the same heat flow to be dissipated.

The lower fluid flow rate advantageously makes it possible to proportionally reduce the average flow cross section of the duct assembly 10 and therefore the overall dimensions of the plate 6. Furthermore, the duct assembly 10 is shaped similarly to a coil and therefore the cooling fluid inverts its motion in each one of the successive groups of ducts 12, 13, 14.

However, differently from what happens with the coils of known type, the presence of more than one duct 11 in parallel in some sections of the duct assembly 10 advantageously ensures better distribution of the fluid in the plate 6, in such a way as to further improve its efficiency.

Clearly, the ducts of the cooling plate 6 can be provided in any number and arranged in various ways, according to the cooling needs of the frequency converter 4, provided that the duct assembly 10 they make up has an increasing overall cross section. Furthermore, the second group of ducts 13 should be preferably included between the first group of ducts 12 and the frequency converter 4, so that the second group of ducts 13 is nearer the coupling surface 6a of the converter 4, where the plate 6 is hotter, and the first group of ducts 12 is farther, where the plate 6 is colder. The above mentioned arrangement, which can be observed in Figures 2 and 5, advantageously makes it possible to exploit at best the cooling power of the fluid, consequently further increasing the efficiency of the plate 6.

In fact, the cooling fluid has more cooling power when it is in the first group of ducts 12 than when it flows in the second group of ducts 13, where it is already warm.

Therefore, arranging the ducts 11 as described above, the average difference between the temperature of the plate 6 and that of the fluid along the duct assembly 10 is minimal.

In other words, we have a condition that is analogous to that of a countercurrent heat exchange between two fluids that, as is known from thermodynamics, allows the maximum heat exchange efficiency to be obtained with the same fluid flow rate.

Preferably, each duct of the duct assembly 10 is a blind hole obtained in a monobloc body 17 belonging to the cooling plate 6. In particular, as shown in Figure 3, each duct of the first group 12 is a first blind hole 18 having the opening 18a arranged on a first side 17a of the monobloc body 17.

Analogously, the ducts of the second group 13 and of the third group 14 comprise, respectively, the same number of second blind holes 19 and third blind holes 20 with the corresponding openings 19a, 20a arranged on a second side 17b of the monobloc body 17 opposite said first side 17a.

Finally, the connection ducts 15, 16 are respectively fourth blind holes 21.

According to the above, the second blind holes 19 preferably have larger overall cross section than the first blind holes 18, as can be observed in the cross section shown in Figure 4.

Furthermore, as can be better observed in the cross section of Figure 5, the fourth blind holes 21 corresponding to the first connection ducts 15 are preferably orthogonal to the first blind holes 18 and intersect them at the level of the corresponding bottoms 18b. As regards the second connection duct 16, it corresponds to a fourth blind hole 21 , preferably orthogonal to the second blind holes 19 and passing at the level of the corresponding bottoms 19b.

Each one of the openings 19a, 21a of the second blind holes 19 and of the fourth blind holes 21 is closed by a corresponding plug 22, in such a way as to create the duct assembly 10.

Advantageously, the duct assembly 10 obtained by means of the blind holes

18, 19, 20, 21 integrated in the volume of the monobloc body 17 favours the compactness of the cooling plate 6, as it avoids the use of a network of pipes external to the plate 6. Furthermore, to advantage, the plate 6 with the duct assembly 10 integrated therein is structurally simpler than a plate provided with a separate duct assembly.

Still advantageously, since the above mentioned plate 6 has a minimum number of components, its cost is reduced compared to that of analogous cooling plates.

As shown in Figure 2, the cooling plate 6 also comprises a first head 23 and a second head 24, respectively associated with the first side 17a and the second side 17b of the monobloc body 17.

In the first head 23 there is an inlet manifold, not represented herein, operatively connected to the inlet opening 7 of the plate 6 and communicating with the openings of each first blind hole 18.

Furthermore, the first head 23 preferably comprises also the inlet opening 7.

Regarding the second head 24, it is provided with an outlet manifold 25, visible in particular in Figures 2 and 6, which places the third blind holes 20 in communication with each other at the level of the corresponding openings 20a and which preferably but not necessarily is also a blind hole whose end 25a is closed by a corresponding plug 22.

The outlet opening 8 of the plate 6 is also created in the second head 24, by means of a hole communicating with the above mentioned outlet manifold 25. Figure 7 shows a construction variant of the cooling plate that is the subject of the invention, indicated as a whole by 30.

This variant differs from the previous one due to the fact that the blind holes 33 of the third group of ducts 31 are operatively connected to one another by means of ducts 34 which are external to the plate 30 and to which the outlet opening 32 belongs. Consequently, the plate 30 is not provided with the second head, meaning that its construction is less difficult.

The above clearly shows that both the plates 6, 30 described above have limited overall dimensions, which makes it possible to integrate them in the case 2 of the compressor 1.

Consequently, the compressor 1 is more compact than the compressors with frequency converter of known type, thus achieving another object of the invention.

Furthermore, if the plate 6, 30 is arranged in the compressor 1 , it is particularly advantageous to cool it by means of the same operating fluid that circulates in the compressor 1.

Preferably, the outlet opening 8, 32 of the plate 6, 30 communicates with the variable volume chamber 5a, so that the fluid flowing out of the plate 6, 30 flows back in the main circuit of the system directly at the level of the variable volume chamber 5a.

The latter represents the most favourable point for introducing the fluid in the circuit, since the fluid that flows out of the plate 6, 30 has thermodynamic conditions that are very similar to those of the fluid contained in the chamber 5a of the compressor 1. Therefore, advantageously, it is possible to improve the overall efficiency of the system.

Furthermore, the plate 6, 30, being integrated in the case 2 of the compressor 1 , can be connected to the chamber 5a through a connection way 2a housed in the case 2 of the compressor 1 , advantageously avoiding an external pipe that would mean increasing the overall dimensions. From an operational point of view and with reference to the plate 6, the cooling fluid is tapped at the liquid state and under high pressure from the main circuit in which the compressor 1 is inserted.

In particular, in a cooling system the above mentioned condition takes place, as is known and as previously mentioned, downstream of the condenser. The high pressure makes it possible to convey the tapped fluid through a throttling valve 9 and successively through the duct assembly 10 of the plate 6, which advantageously makes it possible to avoid using an apposite pumping device. The throttling valve 9, operatively connected to the inlet opening 7 of the cooling plate 6, lowers the pressure and the temperature of the tapped fluid. The fluid flows along the duct assembly 10 of the cooling plate 6, where it absorbs the heat produced by the frequency converter 4 and at the same time evaporates.

Said throttling valve 9 is preferably but not necessarily associated with the first head 23, between the inlet opening 7 and the inlet manifold.

Clearly, the above can be analogously applied also to the variant 30 shown in Figure 7.

The above shows that the plate and the compressor that are the subjects of the invention achieve all the set objects. In particular, the invention achieves the object to produce a cooling plate that is more efficient than the heat dissipation elements of the known type, thus making it possible to limit the overall dimensions of the plate itself. Furthermore, the invention achieves the object to produce a compressor with frequency converter that is more compact than the analogous compressors of known type.

On implementation, the plate and the compressor that are the subjects of the invention may undergo further changes that, though not illustrated or described herein, shall nonetheless be covered by the present patent, provided that they come within the scope of the claims that follow. Where technical features mentioned in any claim are followed by reference signs, those reference sings have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1) Cooling plate (6; 30) for a frequency converter (4), comprising a surface (6a) suited for coupling with said frequency converter (4) and a duct assembly (10) that develops between an inlet opening (7) and an outlet opening (8; 32), between which it is possible to identify an outflow direction (V) of a cooling fluid along said duct assembly (10), characterized in that the flow cross section of said duct assembly (10) has increasing surface area along said outflow direction (V).

2) Cooling plate (6; 30) according to claim 1), characterized in that said duct assembly (10) comprises a plurality of rectilinear ducts (11) arranged side by side.

3) Cooling plate (6; 30) according to claim 2), characterized in that each one of said rectilinear ducts (11) has uniform cross section.

4) Cooling plate (6; 30) according to claim 3), characterized in that said rectilinear ducts (11) comprise a first group of ducts (12) and at least one second group of ducts (13) arranged downstream of said first group of ducts (12) according to said outflow direction (V), the overall flow cross section of said second group of ducts (13) being larger than the overall flow cross section of said first group of ducts (12). 5) Cooling plate (6; 30) according to claim 4), characterized in that a first end (12a) of each duct of said first group (12) is connected to a first end (13a) of a corresponding duct of said second group (13) through a corresponding first connection duct (15).

6) Cooling plate (6; 30) according to claim 5), characterized in that said second group of ducts (13) is included between said first group of ducts (12) and said frequency converter (4).

7) Cooling plate (6; 30) according to any one of claims 5) or 6), characterized in that said rectilinear ducts (11) comprise a third group of ducts (14; 31) whose overall flow cross section is at least equal to the overall flow cross section of said second group of ducts (13).

8) Cooling plate (6; 30) according to claim 7), characterized in that a second end (13b) of each duct of said second group (13) is connected to a first end (14a) of the ducts of said third group (14) through at least one second connection duct (16). 9) Cooling plate (6; 30) according to any one of the preceding claims, characterized in that it comprises a monobloc body (17) provided with a plurality of holes (18, 19, 21, 20; 33) that define said duct assembly (10).

10) Cooling plate (6; 30) according to claim 9) when in combination with claim 8), characterized in that each duct of said first group (12) is a first blind hole (18), each duct of said second group (13) is a second blind hole (19), each duct of said third group (14; 31) is a third blind hole (20; 33), each one of said first connection ducts (15) and of said second connection ducts (16) is a fourth blind hole (21).

11) Cooling plate (6; 30) according to claim 10), characterized in that the openings (18a) of said first blind holes (18) are arranged on a first side (17a) of said monobloc body (17) and the openings (19a) of said second blind holes (19) are arranged on a second side (17b) of said monobloc body (17) opposite said first side (17a).

12) Cooling plate (6; 30) according to claim 11), characterized in that the openings (19a, 21a) of said second blind holes (19) and of said fourth blind holes (21) are closed by plugs (22).

13) Cooling plate (6; 30) according to any one of the claims from 10) to 12), characterized in that it comprises a first head (23) associated with the first side (17a) of said monobloc body (17) and provided with an inlet manifold operatively connected to said inlet opening (7) and communicating with the openings (18a) of said first blind holes (18).

14) Cooling plate (6) according to any one of the claims from 10) to 13), characterized in that it comprises a second head (24) associated with the second side (17b) of said monobloc body (17) and provided with a third connection duct (25) suited to connect the openings (20a) of said third blind holes (20).

15) Compressor (1) comprising a case (2) containing an electric motor (3) fed by a frequency converter (4) and operatively connected to means (5) for compressing an operating fluid, characterized in that it comprises a cooling plate (6; 30) carried out according to any one of the preceding claims, whose coupling surface (6a) is placed in contact with said frequency converter (4).

16) Compressor (1) according to claim 15), characterized in that said cooling plate (6; 30) and said frequency converter (4) are arranged inside said case (2). 17) Compressor (1) according to claim 16), characterized in that said compression means (5) delimit at least one variable volume chamber (5a) provided with an inlet way and one delivery way for said operating fluid.

18) Compressor (1) according to claim 17), characterized in that said case (2) comprises a connection way (2a) between said outlet opening (8; 32) of said plate and said variable volume chamber (5a).

19) Compressor (1) according to any one of the claims from 15) to 18), characterized in that it comprises a throttling valve (9) operatively connected to said inlet opening (7) of said cooling plate (6; 30).