Fan and heat exchanger assembly comprising a fan

Abstract

The invention relates to a fan (15) comprising an annular housing (20) with an inlet opening (45) and an opposite outlet opening (50), the housing having an aerodynamic profile (30) in the cross-section and a radially inwardly facing inner surface (25), along which a slot (35) is provided through which air from a first source can flow via a fan (115), the air flowing in the direction of the outlet opening (50) via the aerodynamic profile (30). An axial fan (55) having a rotor blade (60) is provided in the interior of the annular housing (20), the axial fan conveying air from the inlet opening (45), as a second source, in the direction of the outlet opening (50) such that the discharged air is composed of the air flow from the first source (110) and the air flow from the second source (95). The invention also relates to a heat exchanger assembly (75) comprising such a fan (15).

Description

[0001] FAN AND HEAT EXCHANGER ASSEMBLY WITH FAN

[0002] The invention relates to a fan and a heat exchanger arrangement with this fan.

[0003] The use of fossil fuels is not only becoming increasingly uneconomical, but is also being questioned more and more due to its associated negative impacts on the climate. In addition to increasing the use of renewable energy sources, efficient energy storage systems are therefore essential. These systems, combined with intelligent controls, can reduce energy consumption, for example, when heating or cooling buildings or facilities. Such measures can create significant savings potential, regardless of the energy source used, which also offsets the associated installation costs.

[0004] From DE 10 2015 121 177 A1, a floating device for introducing thermal energy into a body of water and for extracting thermal energy from the body of water is known, comprising a water heat exchanger which, after the device is placed in the body of water, is immersed in it and has an inlet and an outlet for a heat transfer fluid that can transfer thermal energy to the body of water or extract thermal energy from the body of water. The device further comprises an air heat exchanger that can be penetrated by ambient air and also has an inlet for water originating from the body of water with a corresponding outlet, so that water from the body of water can flow through the air heat exchanger, whereby thermal energy can be transferred between the ambient air flowing through the air heat exchanger and the water flowing through the air heat exchanger.From DE 10 2019 118 223 A1, a device for energy transfer and energy storage in a liquid reservoir is known, comprising a water heat exchanger arranged on a base and an air heat exchanger arranged above the water heat exchanger, wherein the water heat exchanger is arranged in a liquid reservoir surrounded by an inner shell that separates the device from an outer shell covering the inner shell from the base, wherein the outer shell is at least partially embedded in a layer of earth, and the device is closed off at the top by a cover in such a way that an airflow from an air inlet to an air outlet can be generated through the air heat exchanger.

[0005] The devices described above typically work in conjunction with a heat pump installed in a building. This heat pump can be powered, for example, via the electrical grid or a dedicated energy storage system. In particular, the air heat exchangers used in these systems require a fan to circulate air through the heat exchanger.

[0006] From WO 2005 / 096715 A2 a heat exchanger arrangement is known in which a radial fan is arranged for forward operation above a heat exchanger, so that the supply air is transported through the heat exchanger to the suction side located in the radial fan and then transported via the pressure side to an exhaust air opening.

[0007] DE 10 2007 003 568 B4 describes a fan arrangement with a radial fan, wherein the radial fan draws in air along its central axis in forward operation and discharges it via an external downstream guide arrangement. DE 10 2017 102 303 A1 describes a heat recovery device comprising a heat exchanger arranged in a housing buried in the ground. The housing has an air inlet and an air outlet between which an airflow generated by a fan flows. The heat exchanger is arranged in the underground housing to avoid disturbing noise emissions. The underground housing is located within an excavation filled with drainage material such as gravel. This document also addresses the requirements regarding the resulting fan noise.

[0008] The JP S55 155125 A shows a thin air conditioning unit in which a blowing centripetal fan is provided opposite an air outlet and a heat exchanger is arranged around it.

[0009] JP H09 303853 A shows the arrangement of a rectification heat exchanger at an airflow passage located between a crossflow fan and an interior heat exchanger.

[0010] WO 2021 / 191371 A1 describes a heat exchanger arrangement comprising a housing in which at least one supply air opening is arranged circumferentially, a cover which covers the housing on a top side and in which at least one exhaust air opening is arranged, wherein a backward-operated radial fan is arranged inside the housing in such a way that it can generate an airflow directed radially inwards with respect to its axis of rotation between the supply air opening and the exhaust air opening, which flows through at least one air heat exchanger arranged in the housing.

[0011] WO 2010 / 100448 A1 describes a blower assembly for generating an airflow, comprising a base including an outer housing having a side wall comprising at least one air inlet, the outer housing accommodating an impeller housing having an air inlet and an air outlet, an impeller arranged within the impeller housing, a motor for driving the impeller about an axis to generate an airflow through the impeller housing, and a noise-dampening element arranged below the air inlet of the impeller housing, and a nozzle attached to the base, the nozzle comprising an internal passage for receiving the airflow from the air outlet of the impeller housing and a mouth through which the airflow is directed out of the blower assembly.wherein the noise-dampening element is spaced at a distance in the range of 5 mm to 60 mm from the air inlet of the impeller housing along the axis, and wherein the nozzle extends about a nozzle axis to define an opening through which air from outside the blower assembly is drawn by the airflow directed out of the orifice.

[0012] Without special measures, the noise level of heat exchanger systems, particularly the acoustic emissions from the fans, would be above the perception threshold of most people. A further problem arises when operating outdoors, especially during the winter months. Here, there is a risk that ice formation will prevent the fan from functioning correctly or damage it.

[0013] The task now is to specify a fan or heat exchanger arrangement with such a fan that is insensitive to ice formation at low acoustic emissions.

[0014] This problem is solved by the features of claim 1. Further advantageous embodiments of the invention are the subject of the dependent claims. These can be combined with one another in a technologically meaningful manner. The description, particularly in conjunction with the drawing, further characterizes and specifies the invention.

[0015] According to the invention, a fan is specified comprising an annular housing with an inlet opening and an opposite outlet opening, which has an aerodynamic profile in cross-section for generating a negative pressure and in which a slot is arranged along a radially inwardly directed inner surface, through which air from a first source can flow via a blower, which reaches the outlet opening via the aerodynamic profile, wherein an axial fan with a rotor blade is arranged inside the annular housing, which conveys air from the inlet opening as a second source towards the outlet opening, so that the discharged air is composed of the airflow from the first source and the airflow from the second source.

[0016] The design of the ring-shaped housing with the blower follows the air multiplier principle described in WO 2010 / 100448 A1 above. Ambient air is drawn in at the inlet by the airflow generated at the slot and transported via the aerodynamic profile towards the outlet. Surprisingly, it has been found that combining this principle with an axial fan creates a fan that, compared to the two individual components, not only has a significantly higher flow rate but also almost completely eliminates the otherwise disruptive noise of the axial fan. The airflow generated by the blower at the slot is harmonized by the negative pressure created at the aerodynamic profile and shields the exterior of the axial fan, thus reducing noise generated there and preventing it from escaping.This creates a fan that is particularly suitable for use in environments where low noise emissions are important. The airflow at the slot can be generated, for example, by several axial fans arranged along the ring-shaped housing, or by a central fan unit that does not generate the airflow directly at the aerodynamic profile, but instead transports the air to the aerodynamic profile via connecting channels.An alternative way to generate the airflow at the slot is a backward-running radial fan whose axis of rotation coincides with an axis of rotation of the axial fan, and whose diameter is larger than that of the annular housing, so that the blades with a blade vertical axis parallel to the axis of rotation can rotate beyond the inner radial fan and generate an airflow directed radially inwards with respect to its axis of rotation, which then exits through the aerodynamic profile.

[0017] According to one embodiment of the fan according to the invention, the rotor blade of the axial fan is arranged within the annular housing adjacent to the slot.

[0018] The position of the axial fan relative to the slot can be optimized through simple experiments regarding the flow rate and noise emissions.

[0019] According to a further embodiment of the fan according to the invention, the rotor blade of the axial fan is arranged between the slot and the outlet opening.

[0020] The position of the axial fan in relation to the outlet opening can also be part of the optimization. According to a further embodiment of the fan according to the invention, the rotor blade of the axial fan projects to a predetermined distance from the inner surface.

[0021] This approach allows for two things: firstly, the efficiency of the axial fan can be increased, as this depends on the gap between the rotor blade and the surrounding housing, defined by the specified distance. Secondly, the specified distance also influences the effect of the airflow from the first source through the slot on the airflow from the second source through the axial fan, meaning the fan's noise level depends on this distance. Therefore, the specified distance should not be too large, as this would at least result in increased noise. Ideally, however, the specified distance should be large enough to prevent even the slightest droplet of ice from forming on the axial fan's rotor blades, thus ensuring the fan's uninterrupted operation.

[0022] According to a further embodiment of the fan according to the invention, the blower is designed as a radial compressor.

[0023] In this way, a high delivery volume can also be achieved for the blower, whereby compressor wheels can be used that are borrowed from the field of turbochargers. For example, a spiral casing can also be connected to the compressor wheel.

[0024] According to a further embodiment of the fan according to the invention, the blower is driven by an electric motor. According to a further embodiment of the fan according to the invention, the axial fan is driven by another electric motor.

[0025] Furthermore, a heat exchanger arrangement is specified which has an air heat exchanger arranged around a central area, which is closed off at the top by a cover which is equipped with a fan as described above, so that in operation air is drawn laterally from the air heat exchanger through it into the central area and from there to the inlet opening of the fan as an airflow from the second source.

[0026] As mentioned earlier, low noise emissions from the fans used in heat exchanger systems, especially in residential areas, are a key consideration. The fan described above allows for both low noise emissions and a high volume of airflow through the air heat exchanger. The air heat exchanger can, for example, be constructed from several individual components arranged around a central area. Ambient air is drawn through the air heat exchanger by the fan and then expelled back into the environment. Consequently, the radially drawn-in air is deflected upwards and exits the heat exchanger system through the cover.

[0027] According to one embodiment of the heat exchanger arrangement according to the invention, exhaust air from a building is supplied to the blower as an airflow from the first source.

[0028] It is particularly advantageous to use the building's exhaust air as the primary heat source. Especially during the winter months, this warms the fan within the ring-shaped housing, almost completely eliminating the risk of ice formation. With previously known devices, the ambient air passing through the air heat exchanger transfers energy to the heat exchanger and thus cools down, resulting in a risk of ice formation, which is further increased by high humidity.

[0029] According to a further embodiment of the heat exchanger arrangement according to the invention, the exhaust air is first guided over fins immersed in a water reservoir before being fed to the blower.

[0030] In this way, a portion of the heat contained in the exhaust air can be transferred to a water reservoir, where it can be used in combination with a water heat exchanger. The exhaust air does not cool down so much that the heating effect of the annular housing described above would no longer occur. However, it is desirable to select the specified distance between the rotor blade and the annular housing alternatively or additionally in such a way that, in the event of droplet icing of the axial fan's rotor blades, they do not touch the annular housing, thus ensuring the axial fan can operate without malfunction.

[0031] According to a further embodiment of the heat exchanger arrangement according to the invention, the fan is arranged in a horizontal installation position in the lid.

[0032] Because the risk of malfunction due to ice formation is almost completely eliminated, the fan can be installed horizontally, unlike the usual installation positions for heat pumps. The predetermined distance between the axial fan's rotor blade and the housing provides additional operational safety, as small ice clumps on the rotor blades do not interfere with operation, allowing the fan to run quietly.

[0033] According to a further embodiment of the heat exchanger arrangement according to the invention, the fan at the outlet opening is covered by a protective grille.

[0034] This reduces the risk of accidental contact with the axial fan.

[0035] According to a further embodiment of the heat exchanger arrangement according to the invention, the delivery rate of the axial fan and the delivery rate of the blower are coordinated.

[0036] To minimize the noise level of the axial fan, the fan's airflow rate should not be too low, otherwise sufficient shielding of the axial fan's airflow will not be achieved. Therefore, it may be possible to supply additional air sources to the fan if the building's exhaust air supply is insufficient. For example, after the air has passed the louvers described above, additional ambient air could be supplied to the fan to achieve a sufficient airflow rate.

[0037] Some exemplary embodiments are explained in more detail below with reference to the drawing. The drawing shows:

[0038] Figure 1 shows a first embodiment of a fan according to the invention in a top view.

[0039] Figure 2 shows a detail of the fan from Figure 1 in a cut side view, and Figure 3 shows an embodiment of a heat exchanger arrangement with the fan from Figure 1 in a side view cut through the central axis.

[0040] In the figures, identical or functionally equivalent components are marked with the same reference symbols.

[0041] With reference to Figure 1, a first embodiment of a fan 15 according to the invention is shown in a top view. The fan 15 comprises an annular housing 20, which is hollow inside and can be filled with air from a first source. On the inner surface 25 of the annular housing 20 there is a circumferential or nearly circumferential slot (not shown in Figure 1), so that this design corresponds to the air multiplier already known from the prior art and described in detail above.

[0042] The structure of the annular housing 20 is shown again in detail in Figure 2, in which the housing 20 is cut along line BB' perpendicular to the plane of the drawing. It can be seen that the annular housing 20 has an aerodynamic profile 30 in cross-section, which serves to generate a negative pressure. The aerodynamic profile 30 can be bulbous or in the form of an airfoil. Furthermore, the slot 35 is visible, through which air from a first source can be passed via a blower and exits the annular housing, as schematically indicated by reference numeral 40. In this way, the ambient air adhering to an inlet opening 45 is additionally set in motion and flows towards an outlet opening 50, which are located on opposite sides of the annular housing 20.As can be seen in Figure 1, an axial fan 55 is arranged inside the annular housing 20. The fan has a rotor blade 60 whose outer edges are positioned at a constant, predetermined distance 65 from the inner surface 25 of the annular housing 20 during rotation. The center point 70 of the axial fan 55 or the rotor blade 60 is identical to the center point of the annular housing 20, resulting in a coaxial arrangement. The predetermined distance 65 can be chosen to be large enough that, in the event of icing of the axial fan 55, the rotor blades 60 do not touch the annular housing 20 at its inner surface 25, thus allowing the axial fan 55 to function without malfunction. However, the predetermined distance 65 must not be chosen to be too large, as this would at least result in increased noise.As the distance 65 increases, the noise-dampening effect of the airflow from the first source via the slot 35 on the airflow from the second source via the axial fan 55 diminishes, so that the noise level of the fan 15 increases when the distance 65 is too large. The airflow generated by the blower at the slot 35 is harmonized by the negative pressure generated at the aerodynamic profile 30 in the area of ​​the tips of the rotor blade 60, thus reducing noise generated there.

[0043] With reference to Figure 3, a schematic sectional view shows a heat exchanger arrangement 75, which comprises an air heat exchanger 85 arranged around a central area 80 and closed at the top by a cover 90. The cover 90 is equipped with a fan 15 above the central area 80, so that during operation, air is drawn laterally from the air heat exchanger 85 through it into the central area 80 and from there to the inlet opening 45 of the fan 15 as an airflow from the second source 95. The air heat exchanger 85 can be constructed from several individual components arranged around the central area 80. Ambient air 100 is then drawn through the air heat exchanger 85 by the fan 15 and exits back into the environment via the fan 15. Consequently, the radially drawn-in air is deflected upwards and exits the heat exchanger arrangement 75 through the cover 90.

[0044] It is particularly advantageous to supply the exhaust air 105 of a building to the heat exchanger assembly 75 as an airflow from the first source 110 to a blower 115, which transports the airflow via channels 120 to the slot 35 in the annular housing 20. In this way, the fan 15 in the area of ​​the annular housing 20 is heated by the exhaust air, which can further reduce the risk of ice formation. Before being supplied to the blower 115, the exhaust air 105 can first be guided over louvers 130 immersed in a water reservoir 125.

[0045] It is important to emphasize that the fan 15 is installed horizontally in the cover 90, which is contrary to the usual vertical installation positions for heat pumps. The flow rate of the axial fan 55 and the flow rate of the blower 115 are coordinated. To keep the noise level of the axial fan 55 as low as possible, the flow rate of the blower 115 should not be too low, otherwise the airflow from the axial fan will not be adequately shielded. Therefore, it may be possible to supply additional sources to the blower 115 of the fan 15 if the exhaust air 105 from a building is insufficient. For example, after the air has passed the louvers 130 described above, additional ambient air could be supplied to the blower 115 to achieve a sufficient flow rate.The features described above and in the claims, as well as those shown in the illustrations, can be advantageously implemented both individually and in various combinations. The invention is not limited to the described embodiments but can be modified in many ways within the scope of expert knowledge.

[0046] List of reference symbols:

[0047] 15 fans

[0048] 20 cases

[0049] 25 interior surface area

[0050] 30 aerodynamic profile

[0051] 35 slots

[0052] 40 reference marks

[0053] 45 Entrance opening

[0054] 50 Exit opening

[0055] 55 Axial fan

[0056] 55 axial fans

[0057] 60 rotor blades

[0058] 65 distance

[0059] 70 Center point

[0060] 75 Heat exchanger arrangement

[0061] 80 Central area

[0062] 85 air heat exchangers

[0063] 90 lids

[0064] 95 second source

[0065] 100 ambient air

[0066] 105 Exhaust air

[0067] 110 first source

[0068] 115 blowers

[0069] 120 channels

[0070] 125 Water reservoir

[0071] 130 slats

Claims

Patent claims:

1. Fan (15) comprising an annular housing (20) with an inlet opening (45) and an opposite outlet opening (50), which has an aerodynamic profile (30) in cross-section and in which a slot (35) is arranged along a radially inwardly directed inner surface (25), which can be supplied with air from a first source via a blower (115), which passes over the aerodynamic profile (30) towards the outlet opening (50), wherein an axial fan (55) with a rotor blade (60) is arranged inside the annular housing (20), which conveys air from the inlet opening (45) as a second source towards the outlet opening (50), so that the discharged air is composed of the airflow from the first source (110) and the airflow from the second source (95).

2. Fan (15) according to claim 1, wherein the rotor blade of the axial fan (55) is arranged within the annular housing (20) adjacent to the slot (35).

3. Fan (15) according to claim 1 or 2, wherein the rotor blade (60) of the axial fan (55) is arranged between the slot (35) and the outlet opening (50).

4. Fan (15) according to one of claims 1 to 3, wherein the rotor blade (60) of the axial fan (55) projects to a predetermined distance (65) from the inner surface (25).

5. Fan (15) according to one of claims 1 to 4, wherein the blower (115) is designed as a radial compressor.

6. Fan (15) according to any one of claims up to 5, wherein the blower (115) is driven by an electric motor.

7. Fan (15) according to one of claims up to 6, wherein the axial fan (55) is driven by a further electric motor.

8. Heat exchanger arrangement (75) comprising an air heat exchanger (85) arranged around a central area (80), which is closed off at the top by a cover (90) which is provided with a fan (15) according to one of claims 1 to 7, so that in operation air is drawn laterally from the air heat exchanger (85) through it into the central area (80) and from there to the inlet opening of the fan (15) as an airflow from the second source (95).

9. Heat exchanger arrangement according to claim 8, in which exhaust air (105) of a building is supplied to the blower (115) as a second source (110).

10. Heat exchanger arrangement according to claim 9, in which the exhaust air (105) is first guided over fins (130) immersed in a water reservoir (125) before being supplied to the blower (115).

11. Heat exchanger arrangement according to one of claims 8 to 10, wherein the fan (15) is arranged in a horizontal installation position in the cover (90).

12. Heat exchanger arrangement according to one of claims 8 to 11, wherein a delivery rate of the axial fan (55) and a delivery rate of the blower (115) are matched to each other.

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