GB2422003A

GB2422003A - Combined fan and heat exchanger

Info

Publication number: GB2422003A
Application number: GB0500142A
Authority: GB
Inventors: Garry Royston Fish; Robyn Pritchard; John Moffat
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2005-01-06
Filing date: 2005-01-06
Publication date: 2006-07-12
Also published as: GB0500142D0

Abstract

A method of transferring heat between a fluid and a gas comprises passing the fluid through passages 16 in a rotating body which is disposed in the stream of gas. The rotating body may comprise of an axial 10 or radial (210, fig 3) fan and the passages 16 may be formed in the hub 12 and blades 14 (214) of the fan. The centripetal forces acting on the fluid in the axial fan 10 may pump the fluid though the passages 16 and avoid the need for a separate pump to pump the fluid though the passages 16. A rim 18 connecting the blades 14 together may be received in a stationary channel 20 and the passages 16 in the blades 14 may communicate with an annular chamber, which functions as a header tank with a connector and is disposed between the rim and channel. The passages (116, fig 2) in the blades may be a closed circuit with an inlet and outlet in the hub (112). The fan may cool an engine bay, a condenser of an air conditioning system, an intercooler or transmission oil, may replace a conventional fan and radiator engine cooling system or may act as a centrifugal pump. The fluid may be a liquid or gas and the fan may be driven by an electric motor, or by the engine.

Description

HEAT EXCHANGER

The present invention relates to a heat exchanger for transferring heat between a fluid (which may be a liquid or a gas) and a gas. Though the heat exchanger of the invention is particularly applicable to the cooling of the engine coolant in a motor vehicle, it may be used in other applications such as an intercooler to cool charge air, as a transmission oil cooler or possibly as a condenser of an air conditioning system.

To extract heat from the coolant circulating through an internal combustion engine, the coolant is conventionally passed through a radiator over which ambient air is blown by means of a fan. The fan is driven by the engine or powered by an electric motor. The radiator is a heat exchanger that provides a large surface area over which heat can be transferred from the coolant to the airflow. The radiator typically comprises two header tanks connected to one another by fine tubes through which the coolant flows. A pump is provided to circulate the coolant through the engine and the radiator. Ribs projecting from, or in thermal contact with, the outer surfaces of the tubes increase the surface area of which heat transfer can take place.

The present invention makes it possible to dispense with the need for a heat exchanger that is separate from the fan.

In accordance with a first aspect of the invention, there is provided a method of transferring heat between a fluid and a gas which comprises passing the fluid through passages in a body while the body is rotated in a stream of the gas.

Preferably, the body itself acts as the fan serving to create the gas stream.

It can be seen that in this way, the invention integrates the heat exchanger into the fan, resulting in space saving as well as improved heat transfer.

If the fan is formed as an axial flow fan with radially extending blades, and the fluid passages extend from a hub to a rim of the fan, the centripetal forces acting on the fluid will serve to pump the fluid through the passages, avoiding the requirement for a separate pump to pump the fluid through the passages. Alternatively, or in addition, some form of turbine can be utiljsecj to increase the internal fluid pressure.

In a second aspect of the invention, there is provided a heat exchanger which comprises a body formed with a plurality of internal passages and mounted for rotation within a gas stream, inlet and outlet connectors being provided to enable a fluid to flow through the passages as it is rotated within the gas stream, so as to transfer heat between the fluid and the gas stream.

The body is preferably constructed as a fan.

The fan may be an axial flow fan comprising a plurality of generally radial blades, a hub connected to the radially inner end of each blade and a rim connected to the radially outer end of each blade.

Connectors can readily be provided on the hub but if it is desired to connect the outlet connector to the rim then the latter may be rotatably received in a stationary housing to form a fluid flow passage between the rim and the surrounding housing, a rotary seal being provided between the rim and the stationary housing.

The body of the heat exchanger may be formed of any suitable material, for example of a plastics material or of aluminium. In the case of aluminium, the passages can be formed by known die casting techniques and in the case of plastics materials the body be moulded in two halves that are assembled to one another to define passages between them.

The heat exchanger body may be driven by an electric motor or, when used to extract heat from the coolant of an engine, it may be driven by the engine itself or by the motion of the coolant through the device.

If the heat exchanger forms part of an automotive vehicle, then the body may act as a fan to pull or blow cooling air over the engine and if the vehicle is fitted with an air conditioning system having a condenser then the body may also act as a fan to blow ambient air over the condenser of the air conditioning system.

If additional surface area is required, then straw-like members which have the hot fluid flowing internally, can be placed in the air stream.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which Figure 1 is a schematic front view of a combined heat exchanger and axial flow fan of a first embodiment of the invention representation of the invention, Figure 2 is a similar view of a second embodiment of the invention, Figure 3 is a side view of a combined heat exchanger and radial flow fan of a third embodiment of the invention, and Figure 4 is a section along the line IVIV in Figure 3.

Figure 1 shows a combined fan and heat exchanger 10 for use in the cooling system of a vehicle mounted engine. The fan 10 is formed of a hub 12 and blades 14. Passages 16 represented by dotted lines in the drawing are formed in the hub 12 and in the blades 14 to allow engine coolant water to enter the hub and to flow radially outwards along the blades 14.

The outer ends of the blades 14 are connected to one another by means of a rim 18. The rim 18, which of course revolves with the fan blades 14, is received in a stationary channel 20 that surrounds the fan. The passages in the blades 14 communicate with an annular chamber defined between the rim 18 and the channel 20. Circumferential seals on opposite sides of the fan seal between the rim 18 and the channel 20 to ensure that coolant does not escape from the chamber as the fan rotates. The chamber effectively acts as a radiator header tank and is fitted with a connector 30 leading back to the engine.

In this embodiment of the invention, the combined heat exchanger and fan serves different purposes. First, it acts as a fan to circulate ambient air which can be used to cool the engine bay and can blow or pull cooling air over other heat exchangers, such as the condenser of air conditioning system, an air charge intercooler, or a transmission oil cooler mounted in the vehicle. Second, the fan acts in place of the fan that is normally used to blow air over the radiator through which the coolant flows. Third, it acts itself in place of the conventional radiator in that the coolant flowing in the blades 14 comes into contact with a fast moving air stream which extracts heat from the coolant.

Last, the fan acts as a centrifugal pump which can be used in place of the coolant pump normally employed in an engine to circulate the coolant.

The fan can be manufactured in several sections which are assembled to one another or it may be cast in one piece.

The fan may be formed of any suitable material, for example aluminium or a plastics material.

In use, the combined fan and heat exchanger may be driven either by an electric motor or by means of fan belt passing over a crankshaft pulley. In the latter case, an electrically operated clutch may be provided in the pulley to avoid the fan being driven under all conditions. If connected to be driven mechanically by the engine, the fan also offers the advantage of acting as a fluid flywheel tending to make the engine run more smoothly.

The embodiment of the invention shown in Figure 2 differs from that of Figure 1 in that the rim 18 and the channel 20 have been omitted. Instead, the coolant enters and leaves the fan 110 through the hub 12 and the coolant channels in the blades 114 are looped so that coolant first travels from the hub 112 to the end of each blade up one passage and then returns to the hub 112 down another passage. In this case, there is no centrifugal pump action and the coolant needs to be circulated by the use of a separate pump. However, the fan may be rotated by incorporating internal blades within the hub to extract momentum from the fluid. To improve the heat exchange area, fins 122 are provided on the blades 114. Of course, such fins can also be incorporated into the embodiment of Figure 1.

In a further alternative design, a connecting rim is present and the fluid is returned from the rim to the hub through a second set of fan blades or straw-like tubes.

Figures 3 and 4 shown an embodiment of the invention in which the a heat exchanger is combined with a radial flow fan rather than an axial flow fan. In this case, the fan 210 has two axially spaced hollow rings 212 and blades 214 extending axially between the two rings 212. Each ring 212 is connected by radial arms 224 to a hub 226 which provides a bearing support for the fan 210 and acts as a rotary connector allowing coolant to enter the fan at one end and leave at the other, flowing through the blades 214 in the manner represented by arrows in Figure 3.

The principle of operation of this embodiment of the invention is the same as that of the embodiments of Figures 1 and 2. Instead of the maintaining the tubes carrying the coolant stationary and blowing air past them, the tubes carrying the coolant are themselves moved through the air, so that the fan and the heat exchanger are integrated with one another. The air flow created by the rotation of the fan not only extracts heat from the engine coolant but also from the condenser of the air conditioning system and from the engine bay itself, where heat can be emitted from components of the exhaust system, such as a turbocharger or a catalytic converter.

In all the embodiments of the invention, the temperature of the fluid can be controlled by varying the rotational speed of the fan or by regulating the flow rate of the fluid through the passages in the fan.

Claims

1. A method of transferring heat between a fluid and a gas which comprises passing the fluid through passages in a body while the body is rotated in a stream of the gas.

2. A method as claimed in claim 1, wherein the body is constituted by a fan serving to create the gas stream, the passages being formed in the blades of the fan.

3. A method as claimed in claim 2, in which the fan is an axial flow fan with radially extending blades.

4. A method as claimed in claim 3, in which the fluid passages extend from a hub to a rim of the fan, whereby the centripetal forces acting on the fluid serve to pump the fluid through the passages.

5. A method as claimed in claim 2, in which the fan is a radial flow fan, the passages extending axially between two end rings.

6. A heat exchanger which comprises a body formed with a plurality of internal passages and mounted for rotation within a gas stream, inlet and outlet connectors being provided to enable fluid to flow through the passages as it is rotated within the gas stream, so as to transfer heat between the fluid and the gas stream.

7. A heat exchanger as claimed in claim 6, wherein the rotating body is a fan serving to create the gas stream.

8. A heat exchanger as claimed in claim 7, wherein the fan is an axial fan with radially extending blades, the passages being formed within the blades.

9. A heat exchanger as claimed in claim 8, wherein the fan comprises a hub connected to the radially inner end of each blade and a rim connected to the radially outer end of each blade.

10. A heat exchanger as claimed in claim 9, wherein the rim is rotatably received in a stationary channel to form a chamber between the rim and the surrounding channel, rotary seals being provided between the rim and the stationary channel.

11. A heat exchanger as claimed in claim 10, wherein each of the hub and the rim has a circumferentially continuous passage acting as a header tank, one connector being provided on the hub and the other on the housing surrounding the rim.

12. A heat exchanger as claimed in claim 8, wherein the passages in the blades define closed circuits and the inlet and outlet connectors are provided in the hub.

13. A heat exchanger as claimed in claim 8, wherein the fan is a radial fan comprising a plurality of blades extending axially between two rings.

14. A heat exchanger as claimed in any of claims 6 to 13, wherein the body is formed of aluminium.

15. A heat exchanger as claimed in any of claims 6 to 14, in which an electric motor is connected to the body.

16. A heat exchanger as claimed in any of claims 6 to 14, in combination with an engine, wherein the body is mechanically coupled for rotation with the engine crankshaft and the fluid in the passages acts as a coolant for the engine.

17. A heat exchanger as claimed in claim 16, wherein the engine forms part of an automotive vehicle and wherein the body acts as a fan to blow or pull cooling air through the engine compartment.

18. A heat exchanger as claimed in claim 16 or 17, wherein the vehicle is fitted with an air conditioning system having a condenser and the body acts as a fan to blow ambient air over the condenser of the air conditioning system.

19. A heat exchanger, constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in Figure 1, Figure 2 or Figures 3 and 4 of the accompanying drawings.