GB2371354A

GB2371354A - A heat exchanger

Info

Publication number: GB2371354A
Application number: GB0101219A
Authority: GB
Inventors: Peter Radford
Original assignee: LINEAR FIN CO Ltd
Current assignee: LINEAR FIN CO Ltd
Priority date: 2001-01-17
Filing date: 2001-01-17
Publication date: 2002-07-24
Anticipated expiration: 2021-01-17
Also published as: GB0101219D0; GB2371354B

Abstract

A heat exchanger, for example, a condenser for an air conditioning system, comprises an upwardly extending duct (2)in which coaxial helically formed heat exchanger tubes(18)extend between manifolds (20, 22). The tubes (18) are disposed one within another, and surround an impeller (16) which is freely rotatable so as to be driven in rotation by spraying means within the duct. The spraying means are also provided for generating a mist within the duct (2) to enhance cooling of the heat exchanger tubes (18). The impeller (16) may be in the form of a cylindrical steel drum (26), having domed end caps (28) provided with bearing trunnions (30). The drum (26) has a series of perforations (32) forming impeller blades (34). A fan (4) may assist any upward air flow in the duct (2).

Description

A HEAT EXCHANGER This invention relates to a heat exchanger, and is particularly, although not exclusively, concerned with heat exchangers in the form of condensers or evaporators for refrigerant in air conditioning or refrigeration systems.

A conventional condenser for an air conditioning system comprises condenser tubing through which the refrigerant-flows, and over which air is driven by means of a fan. Such condensers are commonly disposed on an outside wall or the roof of the building to be air conditioned. The condenser tubing follows a convoluted path and is arranged in the form of a rectangular panel in which lengths of the tubing extend parallel to each other through fins across the width of the panel. In many condensers the panel is disposed vertically, and air is forced past the tubing in a horizontal direction by a fan.

Such condensers are invariably noisy, more noticably at night, and rely heavily on the fans to operate properly.

According to the present invention there is provided a heat exchanger comprising a duct in which a heat exchanger coil unit is situated, the coil unit comprising refrigerant tubing which extends circumferentially of the duct, a rotatable impeller being disposed within the duct to impart a swirling motion, about the axis of the duct, to air passing through the duct and over the heat exchanger coil unit.

Rotation of the impeller thus causes air passing through the duct to travel in a generally helical motion so as to increase the duration of contact between the air and the refrigerant tubing, so increasing the heat exchange between the refrigerant and the air.

The impeller is preferably mounted for free

rotation within the duct, and may be of cylindrical form, coaxial with the duct.

The impeller may be configured so as to be driven in rotation by air flow through the duct. For example, the impeller may comprise a drum having perforations through which air may flow, and the material surrounding these perforations may extend obliquely of the wall of the drum so as to serve the function of aerofoils. The impeller may also be configured so as to be driven by at least one jet of water.

The refrigerant tubing may extend helically around the impeller. In a preferred embodiment, there is a plurality of helical refrigerant tubes, disposed coaxially one within the helical coils of another. The helical tubes may be connected at each end to a respective common manifold. Each tube may, for example, have a diameter in the range 5 to 25 mm and be wound in a helix having a pitch in the range 20 to 75 mm. The radial distance between adjacent coils of the tubes 18 may be in the range 10 to 75 mm.

The duct may be disposed with its axis upright, in which case the duct may serve as a chimney, drawing air through it by convection. Whether or not the duct is upright, a fan may be provided to induce air flow through the duct. If the duct is upright, the fan may be disposed at the top.

To enhance cooling of the refrigerant in the heat exchanger, means may be provided for spraying water into the air flow through the duct, in order to generate a mist. If the duct is vertical, the spraying means may be disposed at or near the bottom of the duct. Additional spraying means may be directed at the impeller in a direction which assists rotation of the impeller.

To provide an increased capacity for refrigerant in the system, there may be provided a refrigerant

reservoir. This may take the form of helically wound reservoir tubes similar to the refrigerant tubes, and may be of larger diameter.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which : Figure 1 is a sectional view of a condenser of an air conditioning system ; Figure 2 is a sectional view of the condenser taken generally on the line II-II in Figure 1 ; Figure 3 is a sectional view of the condenser taken generally along the line III-III in Figure 1 ; Figure 4 is a partial perspective view of a former ; Figure 5 is a partial side view of the former of Figure 4 comprising part of the condenser ; and Figure 6 is a plan view of an assembly of formers as shown in Figures 4 and 5.

The condenser shown in Figure 1 comprises a duct 2 which may be a metal tube or, more preferably, may be made from plastics material as a two-piece rotational moulding.

The duct 2 is disposed with its axis generally vertical, and at its top end there is a fan 4 driven by a motor 6. The duct 2 stands on a base 8 which includes a frame having oppositely disposed open sides defining air inlet openings 10 (Figure 3) provided with filters 12 and accommodating a reservoir constituted by reservoir tubes 13. Within the duct 2 there is a heat exchanger coil unit, shown generally at 14, which is of cylindrical form, extending between the wall of the duct 2 and an internal space which accommodates an impeller 16.

The coil unit 14 comprises refrigerant tubing disposed as six coaxial helical tubes 18 (Figure 2).

Each tube may, for example, have a diameter of 10mm and be wound in a helix having a pitch of 50mm. The radial distance between adjacent tubes 18 is 25mm, giving an overall radial depth of 185mm for the coil unit.

At the top, each tube is connected to an inlet manifold 20, which is fed by a single supply pipe (not shown). At the bottom, each tube 18 communicates with a connecting manifold 22, from which extends the reservoir tubes 13. There are three of the reservoir tubes 13 of larger diameter than the refrigerant tubes 18. At the bottom the reservoir tubes communicate with an outlet manifold 23. The base 8 accommodates water spray nozzles 24 and associated pipe work. These nozzles are disposed to supply an atomised water spray into the air flow over the reservoir tubes and through the duct 2. The base also accommodates a drip tray 27 provided with an outlet 29.

The tubes 18 are supported by formers 35 (Figure 4), each of which comprises an elongate body 39, having a rib 40 running centrally along one side and a corresponding channel 41 running centrally along the opposite side for receiving the rib 40 of an adjacent former 35. Assemblies 42 (Figure 6) of adjacent formers 35 are disposed radially within the duct 2 and are located in vertical channels 38 provided in the duct inside wall. Each former 35 has transverse recesses 50 spaced regularly along its length. Each alternate recess 50b (Figure 5) supports vertically a section of the helical tubes 18. Each other recess 50a is left open to allow air flow through the assemblies 42. In the preferred embodiment, the formers 35 are mounted vertically offset such that the supporting recesses 50b are positioned appropriately in a manner to support the helical tube 18. In another embodiment, the formers 35 are vertically aligned, and the refrigerant tubing 18 comprises coils each lying in a

single transverse plane and interconnected by inclined transitional sections.

At the top and bottom of the heat exchanger coil unit 14, support bars (not shown) are provided, which are secured to opposite former assemblies 42 and which receive the trunnions 30 of the impeller. Thus, the heat exchanger coil unit 14 and the impeller 16 are assembled as a module which can be installed as a unit in the duct. 2 and located in the six vertical channels 38.

The impeller 16 is in the form of a cylindrical steel drum 26, having domed end caps 28 provided with the bearing trunnions 30. The drum 26 has a series of perforations 32. The material of the drum 26 surrounding the perforations is deformed away from the cylindrical wall of the drum 26 to define impeller blades 34 so that upwards air flow past the drum 26 causes the impeller 16 to rotate. Water spray nozzles 25 are accommodated around the impeller 16 and mounted on the inner ends of the former assemblies 42. The water jets 25 are oriented to spray water in a direction so as to generally assist the rotation of the impeller 16.

For use, the condenser shown in the Figures would be installed outside a building to be air conditioned, for example on the roof. Inlet and outlet pipework for conveying refrigerant from the condenser to a refrigerant compressor and evaporator of an air conditioning installation are connected respectively to the manifolds 20 and 23. In use, the relatively warm refrigerant in the coil unit 14 induces an upwards air flow in the duct 2, causing air to be drawn in through the openings 10. This upward air flow may be assisted, under some conditions, by the fan 4.

The upwards air flow in the duct 2 acts on the blades 34 of the impeller 16, causing it to rotate.

This in turn induces a swirling motion in the upwards flowing air, causing the air to circulate within the duct 2, following a path approximating to the coils of the tubes 18. This increases the duration of contact between the air and the refrigerant tubes 18, so enhancing heat transfer from the refrigerant in the tubes 18 to the air.

If additional cooling of the refrigerant is required, water can be supplied through the nozzles 24 and/or 25 to create a mist within the air flow. This mist not only reduces the temperature of the air flowing through the duct 2 by evaporation of the atomised droplets, but also causes additional evaporative cooling of the refrigerant as droplets falling on the refrigerant tubes 18 and reservoir tubes 13 are evaporated. Water discharged from the nozzles 25 impinges on the blades 34 to assist rotation of the impeller 16. Surplus water which does not evaporate to be carried upwards for discharge from the duct 2 is collected in the drip tray 27 and passes through the outlet 29 for recirculation or discharge to drain.

Although not shown, appropriate control means is provided for controlling the speed of the fan 6 and the volume of water discharged through the nozzles 24.

Control may be based on the modelling of various parameters of the condenser, for example the air and refrigerant air and inlet temperatures, and the humidity of the air at the exit from the duct 2.

Although the invention has been described with reference to a condenser in an air condition system, it will be appreciated that it can also be applied to an evaporator of a refrigeration system.

Claims

CLAIMS 1. A heat exchanger comprising a duct in which a heat exchanger coil unit is situated, the coil unit comprising refrigerant tubing which extends circumferentially of the duct, a rotatable impeller being disposed within the duct to impart a swirling motion, about the axis of the duct, to air passing through the duct and over the heat exchanger coil unit.
2. A. heat exchanger as claimed in claim 1, in which the impeller is freely rotatable.
3. A heat exchanger as claimed in claim 2, in which the impeller is configured so as to be driven in rotation by air flow through the duct.
4. A heat exchanger as claimed in any one of the preceding claims, in which the impeller comprises a hollow cylindrical body which is coaxial with the duct.
5. A heat exchanger as claimed in claim 4, in which the impeller comprises a perforated drum.
6. A heat exchanger as claimed in claim 5, in which the material of the drum around the perforations extends obliquely to the drum surface to define impeller blades.
7. A heat exchanger as claimed in any preceding claim, in which spraying means provides a spray within the duct.
8. A heat exchanger as claimed in claim 7. in which the spraying means is directed so as to assist rotation of the impeller.
9. A heat exchanger as claimed in any one of the preceding claims, in which the refrigerant tubing extends helically around the impeller.

.
10. A heat exchanger as claimed in claim 9, in which the refrigerant tubing comprises a plurality of coaxial helical tubes disposed one within another.
11 A heat exchanger as claimed in claim la, in which the helical tubes communicate with common

manifolds at each end.
12 A heat exchanger as claimed in claim 10 or 11, in which the refrigerant tubes are supported within the duct by supporting elements which engage adjacent turns of each tube.
13. A heat exchanger as claimed in any one of the preceding claims, in which the duct is disposed with its axis extending upwardly.
14. A heat exchanger as claimed in any one of the preceding claims, in which a fan is provided for causing air flow through the duct.
15. A heat exchanger as claimed in claim 14 when appendant to claim 13, in which the fan is disposed at the top of the duct.
16. A heat exchanger as claimed in any one of the preceding claims, in which a reservoir is provided.
17. A heat exchanger as claimed in claim 16, in which the reservoir comprises helical tubing.
18. A heat exchanger as claimed in claim 17 when appendant to claim 10, in which the reservoir tubing is of larger diameter than the refrigerant tubing.
19. A heat exchanger as claimed in any one of claims 16 to 18, in which the reservoir is accommodated in a base on which the duct is supported.
20. A heat exchanger as claimed in any one of the preceding claims, in which spraying means is provided for creating a water spray directed at the reservoir.
21. A heat exchanger as claimed in claim 20, in which the spraying means is disposed at the bottom of the duct.
22. A heat exchanger substantially as described herein with reference to, and as shown in, the accompanying drawings.
23. An air conditioning installation, including a heat exchanger in accordance with any one of the preceding claims.