Patent Application
20110164997
Described below is a pump, in particular a circulating pump, which has an impeller in a pump housing and with which a fluid can be delivered from a pump inlet of the pump housing to a pump outlet of the pump housing. A rotor of an electric motor is mechanically coupled to the impeller via a shaft such that, by rotation of the rotor, the impeller can be placed into a corresponding rotating movement. Furthermore, the pump cools the rotor of the electric motor.
In order to increase the efficiency of circulating pumps, it is known to produce the circulating pumps from particularly high-quality materials in order to improve the efficiency thereof. Circulating pumps of this type are referred to as high efficiency circulating pumps. Thus, for example, short-circuit bars of the rotor are manufactured from copper instead of the aluminum which is frequently used. However, these high efficiency circulating pumps have the disadvantage of high costs.
An aspect is to provide a pump in which the efficiency can be increased in a simpler and more cost-effective manner.
A pump includes an impeller in a pump housing and with which a fluid can be delivered from a pump inlet of the pump housing to a pump outlet of the pump housing. The pump furthermore includes an electric motor, the rotor of which is mechanically coupled to the impeller via a shaft such that, by rotation of the rotor, the impeller can be placed into a corresponding rotating movement. Furthermore, cooling of the rotor of the electric motor is provided by a thermosiphon which is arranged in the shaft, the impeller serving as a heat sink for a working medium of the thermosiphon.
The pump makes use of the fact that better cooling of the rotor in electric motors results in an increase in the efficiency. This effect is made use of in the pump and a shaft thermosiphon is inserted in the rotor shaft. Cooling of the shaft also results in cooling of the rotor of the electric motor, thus resulting in the desired increase in efficiency. The heat conducted away from the rotor is dispensed via the thermosiphon to the pump wheel which is located in a fluid, for example heating water, the pump wheel being used and designed as a condenser. This has the consequence that heat lost from the rotor of the electric motor is recycled into the fluid circuit. If the latter is, as mentioned, a heating circuit, then the efficiency thereof can also be increased, since heat is supplied to the heating water.
The pump furthermore has the advantage of being able to be produced more cost-effectively by comparison to the high efficiency circulating pumps known from the related art, since use can be made of known materials, such as short circuit bars of the rotor made from aluminum. Furthermore, however, the efficiency of already optimized high efficiency circulating pumps can also be further increased. Although a smaller increase in efficiency than with conventional circulating pumps should be anticipated owing to the losses from high efficiency circulating pumps already being lower, nevertheless the provision of a thermosiphon in the shaft and the use of the impeller as a heat sink permit a further improvement in the efficiency.
According to an advantageous refinement, in order to form the thermosiphon in the shaft, a recess is provided, the recess extending in the longitudinal direction and in which the working medium circulates owing to a change in the state of aggregation between liquid and gaseous. It is expedient in this case if the recess extends over the entire width of the rotor of the electric motor so that as good an amount of heat as possible can be admitted into the working medium in the thermosiphon. Furthermore, it is also advantageous if the recess is formed in the region of bearings of the electric motor. In addition to the cooling of the rotor, the bearing temperatures are also evened out and reduced at the bearings, thus increasing the service life of these highly stressed wearing parts.
In one refinement, the shaft has a central section and an end section which is fixedly connected to the central section and to which the impeller is fastened, the recess being of cylindrical design in the central section and the recess being of conical design in the end section. This refinement ensures the circulation of the working medium which has different states of aggregation during the operation of the pump. In contrast to known thermosiphons, the circulation of the working medium is not made possible by capillary forces but rather by rotational forces. For this purpose, the conical design of the recess in the end section of the shaft is necessary in order to press condensed working medium back in the direction of the rotor of the electric motor.
In one specific refinement, the electric motor and at least part of the central section of the shaft are arranged in a fluid tight manner in a housing part, and the end section is arranged outside the housing part. In particular, the end section and the central section of the shaft are surrounded on the outer circumferential side by a seal which may be arranged outside the housing part, fitting snugly onto a passage opening for the shaft. The housing part may be, for example, a motor housing surrounding the electric motor. In a practical refinement, the housing part and the pump housing may be combined with each other. The seal ensures that the fluid conveyed by the impeller cannot come into contact with components of the electric motor, which could result in the destruction thereof.
According to a further refinement, a device with spokes extending radially from a central hub is provided in the conical recess of the end section in order to improve the formation of a film of condensate of the working medium on the conical wall of the end section. The device may be arranged in the conical recess and is intended to improve the circulation of the working medium in the thermosiphon.
It is furthermore expedient if the ratio of the diameter of the recess, in particular in the central section, to the diameter of the shaft is such that at least a predetermined torque can be transmitted to the impeller. By the provision of a recess in the shaft, the torque which can be transmitted by the electric motor to the impeller is reduced. In this structural refinement of the thermosiphon, care should therefore be taken to ensure that a torque which is not less than necessary can still be transmitted by the shaft to the impeller. The provision of the thermosiphon in the shaft may possibly result in the diameter of the shaft having to be increased in order still to be able to meet the necessary operating parameters of the pump.
It has furthermore been shown that the thermosiphon is particularly efficient if the wall of the recess is rough. This means that, in particular when making the recesses in the central and end sections of the shaft, the walls do not have to be finished in a particular way. On the contrary, it has been shown that the thermosiphon is most efficient if, after the recess has been made, no further recess machining steps take place. Thus, in addition to a maximum increase in the efficiency, the costs for producing the thermosiphon can be kept low.
It is furthermore expedient if the working medium is placed into the recess under vacuum and, by sealing the recess permanently without any loss. A refrigerant, in particular water, FC72, R124a, R600a, isobutane, etc., having an evaporation temperature of less than 100° C. is provided as the working medium. In principle, any refrigerant which has an evaporation temperature which is lower than the heat generated by the rotor of the electric motor is suitable as the working medium.
In a further refinement, an end of the shaft which is outside the housing part and is opposite the end section has a hub which is provided for connection to a fan wheel for cooling the electric motor. The additional fan wheel can constitute a further heat sink for the thermosiphon. In principle, however, the refinement of the thermosiphon with the impeller as a heat sink renders the provision of a further fan wheel unnecessary.
According to a further refinement, in an installation situation, the shaft is mounted horizontally or is mounted in such a manner that, with respect to the direction of gravitational force, the impeller on the end section of the shaft is located higher than the central section of the shaft. Both of these cases ensure that the thermosiphon is capable of functioning in order to reduce the temperature of the rotor of the electric motor. In other differing installation situations, cooling of the rotor can no longer be ensured. Although, then, the efficiency of the pump can no longer be increased, operation of the pump with the conventional efficiency is readily possible.
These and other aspects and advantages will become more apparent and more readily appreciated from the following description of an exemplary embodiment, taken in conjunction with the accompanying drawings of which:
The single figure shows a section through a pump used, for example, as a circulating pump in a heating circuit
Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
The pump which is illustrated in the figure has an impeller 2 which is arranged in a two-part pump housing 1a, 3. The pump housing 1a has a pump inlet 1c, for example, from a heater, which opens into a collecting duct 1b. The collecting duct 1b extends spirally in the radial direction of the impeller 2 and opens into a pump outlet 1d of the pump housing 1a. The pump outlet 1d is connected, for example, to an inlet to a radiator. In the exemplary embodiment, the pump housing 3 is formed integrally with a motor housing 5 and has a passage opening 14 for a shaft 7 which connects the impeller 2 mechanically directly, i.e. without an intermediate gear mechanism, to a rotor of an electric motor 6. The electric motor 6 is arranged in the motor housing 5. In order to obtain sealing of the electric components provided in the motor housing 5 from the fluid, for example water, conveyed by the impeller 2, a seal 4 is provided outside the motor housing 5 in the region of the passage opening 14. The seal 4 fits snugly onto the outer edge of the passage opening 14 and is connected to a disk spring 13 which is arranged on the outer circumferential side of the shaft 7.
The shaft 7 is designed in two parts and has a central section 9a, 9b (having different diameters merely by way of example) and an end section 10 connected to the central section. A recess which is provided with respect to the axis of rotation is formed in the central section 9a, 9b and in the end section 10. In the central section 9a, 9b, the recess is of continuous cylindrical design. In the end section 10, the recess is of conical design. As can be gathered from the figure, the impeller 2 is connected to the end section 10 of the shaft 7. The central section 9a, 9b and the end section 10 are connected to each other in such a manner that a working medium which is placed into the recess 8 under vacuum is arranged in the recess permanently without any loss. A refrigerant having an evaporation temperature of. e.g., less than 100° C. is provided as the working medium in the recess 8. The refrigerant used may be, for example, water, R124a, R600a, FC72, isobutane, etc.
The provision of the recess 8 in the shaft 7 with the described shape of the recess in the central section 9 and in the end section 10 and with the refrigerant being placed into the recess 8 results in the formation of a thermosiphon which is arranged in the shaft and in which the impeller 2, which is connected to the shaft, serves as a heat sink for the refrigerant of the thermosiphon. The effect achieved by the thermosiphon is cooling of the rotor of the electric motor and of the bearings 15, 16 thereof. During operation of the electric motor, temperatures of approx. 150° C. to 300° C. are achieved in the vicinity of the rotor, as a result of which the refrigerant provided in the recess 8 begins to evaporate. In an installation situation in which the shaft of the circulating pump is mounted horizontally or is mounted in such a manner that, with respect to the direction of gravitational force, the impeller 2 on the end section 10 of the shaft 7 is located higher than the central section 9a, 9b of the shaft, the evaporated refrigerant is forced in the direction of the end section 10 of the shaft 7 because of the rotation of the shaft. The impeller 2 is arranged in the fluid, which is at a maximum of 70° C., for example in the case of a heating circuit, and constitutes a condenser of the thermosiphon.
Owing to the lower temperature of the impeller 2 and the conical configuration of the recess 8 in the region of the end section, the evaporated working medium condenses and is pressed onto the wall of the conical recess of the end section 10 because of the rotating shaft 7. The conical design of the recess 8 in the region of the end section 10 ensures that the condensed working medium is pressed in the direction of the central section 9a, 9b until the working medium enters, in turn, into the region of the electric motor 6 (and therefore of the heat source) and is evaporated there again. The working medium therefore circulates owing to this change in the state of aggregation between liquid and gaseous in the recess 8 of the shaft 7. Thus, waste heat is transported away from the electric motor and admitted via the impeller 2 to the fluid which is conveyed by the latter. In contrast to known thermosiphons, the circulation of the working medium of the thermosiphon formed in the shaft 7 is not based on capillary forces but rather on the rotational forces which occur in the shaft 7 during operation.
As a result, the rotor of the electric motor 6 and the bearings 15, 16 of the shaft 7 in the region of the electric motor 6 are thereby cooled, thus resulting in an increase in the efficiency. At the same time, the heat which is lost and is conducted away from the electric motor 6 can be recycled into the fluid circuit in which the impeller 2 is located.
The exemplary embodiment, which is illustrated in the figure, of the pump has an optional hub 12 which projects with the shaft 7 out of the motor housing 5 and is arranged at that end of the shaft 7 which is opposite the end section. The hub 12 serves to accommodate a conventional fan wheel in order optionally to bring about further cooling of the electric motor.
The ratio of the diameter of the recess 8, in particular in the central section 9a, 9b, to the diameter of the shaft 7 has to be dimensioned in such a manner that at least a predetermined torque can be transmitted to the impeller 2. In the exemplary embodiment illustrated, the shaft 7 has sections of differing diameter and therefore differing wall thicknesses in its central section 9a, 9b in order to transmit the required torque. This illustration is merely by way of example and is not compulsory. Irrespective of the wall thicknesses of the shaft 7 in different sections of the central section 9a, 9b, the bore 8 in the central section 9a, 9b has the same diameter continuously, thus ensuring circulation of the working medium in the recess 8.
When producing the recess 8 in the shaft, the wall of the recess 8 does not need to be finished. It has turned out on the contrary that the thermosiphon is much more efficient the rougher the wall of the recess 8 is. However, it is expedient to remove lubricants which may have been introduced into the recess 8 in order to produce the latter, since the lubricants may have a disadvantageous effect on the state of aggregation of the working medium.
The thermosiphon provided in the shaft 7 of the circulating pump can be provided in conventional pumps, for example circulating pumps, and in what are referred to as high efficiency pumps. If a thermosiphon is installed in a conventional pump, pumps having efficiency comparable to the high efficiency pumps can be realized substantially more favorably, since materials which are more cost-effective can be used in the production of the pumps.
For example, in standard pumps having an asynchronous motor within the range of 10 to 20 kW, an increase in efficiency of 1.5% can be obtained. The provision of a thermosiphon in the shaft of a high efficiency pump also results in an improvement in the efficiency there, but the increase in efficiency is smaller than in conventional pumps since high efficiency pumps inherently already have lower losses.
A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 046 293.4 | Sep 2008 | DE | national |
This application is the U.S. national stage of International Application No. PCT/EP2009/059235, filed Jul. 17, 2009 and claims the benefit thereof. The International Application claims the benefits of German Application No. 102008046293.4 filed on Sep. 8, 2008; both applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/059235 | 7/17/2009 | WO | 00 | 3/8/2011 |
