EP0244229A2

EP0244229A2 - Air conditioning apparatus

Info

Publication number: EP0244229A2
Application number: EP87303818A
Authority: EP
Inventors: Wilfred Alan Link
Original assignee: IMI Air Conditioning Ltd
Current assignee: IMI Air Conditioning Ltd
Priority date: 1986-04-30
Filing date: 1987-04-29
Publication date: 1987-11-04
Also published as: EP0244229A3

Abstract

Air conditioning apparatus and a drip tray (7) for such apparatus in which the air is directed in a downward direction through an evaporator (4) and in which the drip tray is provided below the evaporator to catch drips entrained in the air. The drip tray being permeable to air but catching the water drops, preferably being formed of a series of side by side 'S' shaped overlapping strips which interlink to catch water drops but which permit air to flow through the drip tray, the drip tray being formed of a material of lower thermal conductivity than metal.

Description

This invention relates to air conditioning apparatus and the drip trays for such apparatus and has particular reference to air conditioning apparatus in which air flows in a downward direction through an evaporator coil.
Air conditioning apparatus is well known in which there is provided an evaporator unit comprising a evaporator coil or other type of heat exchanger through which is passed air to cool the air for distribution inside a room. The action of cooling the air frequently gives rise to the formation of water by condensation of moisture in the air. It is normal practice therefore to provide a drip tray beneath the evaporator coil into which water droplets can pass for subsequent disposal. In conventional air conditioning apparatus air is passed substantially horizontally at right angles to the coil which is mounted in a vertical plane and water drips vertically downwards and is collected in a drip tray for disposal.
There are certain situations where the provision of a vertical coil causes problems because of the height of the coil, thus in ceiling mounted air conditioning apparatus the height of the evaporator unit can be a significant problem if the ceiling height is low.
If the coil is disposed horizontally or substantially horizontally so that air is passed downwardly through the coil, there are problems in arranging for the drip tray to catch drops of condensate since the drip tray must be in the flow of condensate from the evaporator.
In British Patent Specification 341 249 there is described a drip tray in the form of a plurality of Z-section elements which permit air to flow through the drip tray whilst catching drops of condensate. It is stated that the strips of Z-shaped section are to be formed of zinc or other suitable metal. It has unexpectedly been found that when attempting to use drip trays of the design shown in British Patent Specification 341 249, condensation still falls from the drip tray, and it was originally thought that this resulted from condensate passing through the drip tray rather than being caught by the strips. Thus, the drip tray described in the earlier patent specification has been found not to be completely satisfactory in that drips still fall from the metal strips.
In US Patent 4 592 210, there is described a heat exchanger unit for an air conditioning system in which air passes vertically up through the unit through a drip tray which has a form in section similar to that shown in British Patent Specification 341 249. In the US Patent however, the drip tray is located on the inlet side of the air conditioning unit rather than on the outlet side as described in the British Patent Specification and also the air conditioning unit is adapted to be floor mounted and to dispense conditioned air horizontally through an outlet fitted to the top of the unit.
By the present invention there is provided an air conditioning apparatus including an evaporator adapted to permit the flow of air in a downward direction therethrough, there being provided a drip tray to catch condensate in which the drip tray is formed in such a manner as to catch drops of liquid entrained in the flowing air but which permits air to flow therethrough the drip tray having a thermal conductivity less than that of metal.
The present invention also provides a drip tray for air conditioning apparatus in which the air is passed in a downwards direction through the evaporator, the drip tray being formed in such a manner as to permit air to pass therethrough and to catch drops of liquid entrained in the air, the drip tray having a thermal conductivity less than that of metal.
The drip tray may be formed of a series of side by side spaced strips of generally "S" shape in cross-section interlinked so as to permit air to flow through the strips. The downwardly directed portion of the upper end of each strip with the exception of one end strip is adapted to overlie the bottom portion of the adjacent "S" shaped strip. The "S" shaped strip may be formed of elongated "S's". The strips may be inclined so that condensate runs to one end and falls into a collecting channel for disposal. The plane of the drip tray may be inclined so as to reduce the amount of overlap required from the upper portion of one strip over the lower portion of its adjacent "S" strip to catch the condensate.
The drip tray may be formed of a series of "V" or "U" shaped channels each alternate channel being inverted and co-operating so as to catch drops passing therethrough.
The drip tray may be in the form of a planar tray with a plurality of holes having flanges extending towards the evaporator there being provided caps located over the flanges to prevent the direct flow of water drops through the holes but being spaced from the flanges to permit air to flow therethrough.
The drip tray may be of metal and there may be provided a layer of insulating material on the lower surface of the drip tray. Alternatively the drip tray may be formed of plastics material.
The present invention further provides air conditioning apparatus including a housing adapted to be mounted in, on or adjacent to the roof of a room and to contain an evaporator for cooling air and a drip tray to catch drips of water formed by condensation of water vapour from air passing through the evaporator, characterised in that the drip tray is formed in such a manner as to permit the flow of air therethrough, but to catch drops of liquid entrained in the air, and in that those portions of the drip tray which have a downstream surface from which condensate may be carried into the air stream from the housing have a thermal conductivity lower than that of metal.
The drip tray may be formed of metal components having an insulating layer on their lower surface, typically a layer of plastics material. Alternatively, the drip tray may be formed of plastics material.
By way of example embodiments of the present invention will now be described with reference to the accompanying drawings of which

Figure 1 is a cross section through the central portion of an evaporator unit formed in accordance with the present invention;
Figure 2 is a cross section in a plain parallel to that of Figure 1 but adjacent to one end of the evaporator;
Figure 3 is a perspective view of a collector channel;
Figure 4 is a perspective view of a lower end plate for the evaporator of Figure 1;
Figures 5 and 6 are schematic sectional views of alternate forms of drip trays; and
Figure 7 is a sectional view of a yet further form of drip tray.

The evaporator shown in Figure 1 is part of a split system in which the condensor is located separately from the evaporator unit. Typically the condensor will be located outside a window of a room or there may be a central condensor providing coolant to a number of evaporator units.
The assembly comprises an upper housing 1 and a lower housing 2. Located within the upper housing 1 is a cross-flow fan 3 which directs incoming air over a coil 4. Air is fed into the fan 3 via an inlet orifice 5 into the lower housing 2. The direction of flow of air is shown by the arrows 6. Once the air is passed through the coil 4, in a substantially downward direction, it encounters a drip tray 7 which is in the form of a series of spaced "S" shaped side by side strips 8. It can be seen that air may readily flow through the "S" shaped strips but water will be trapped on the strips and cannot pass through them. The dried air is then sent out through the lower housing 2 via outlets such as 9 and 10. Water which drops on to the "S" shaped strips accumulates in the lower portion of the strips and, because the strips are inclined to the horizontal, the water drips off the ends of 11 into a collecting channel 12. From the collecting channel 12 water is led into a sump 13 and from there via a suitable tube 14 to a drain.
Because of the fact that the coil is in a substantially horizontal position the overall height of the unit is low and it can be located satisfactorily within a roof space above a ceiling 15.
It will be appreciated that the drip tray can be formed of a series of "V" shaped strips 16, 17 (which may, of course, be "U" shaped) or may be in the form of a planar sheet 18 with a series of upwardly directed flanges 19 which are located around holes 20. Caps 21 prevent the direct flow of drops through the drip tray.
With the preferred form of the drip tray as shown in accordance with Figures 1 - 3 the air flow is little restricted and there is no need for the air to be turned through 180° as is the requirement with the embodiment illustrated in Figure 6 thus the inclined "S" shaped members form the preferred type of drip tray.
The drip tray may be of metal components 22 with an insulating layer 23 on the lower side to restrict or prevent condensation on the drip tray lower surface. Alternatively the drip tray may be formed of plastics material.
In all cases, the drip tray components have a thermal conductivity lower than that of metal. It is now believed that there is a temperature difference between the temperature of the condensate and the temperature of the air. In most cases, this temperature difference between air and condensate temperature is of no significance. However, with the drip tray of the present invention, condensate falls into the sections of the drip tray and consequently cools the upper surface of the drip tray below that of the air passing through the drip tray. This can mean that immediately below the drip tray the cold air is cooled below its dew point causing condensation to form below the drip tray itself. It is this condensation which can fall from the air conditioning unit.
This problem is overcome by the adoption of drip tray components of insulating material, ie of material having a thermal conductivity lower than that of metal. The result of this is that the condensate can be warmed very slightly by the air passing over it and insufficient temperature difference between the upper and lower surface of the drip tray can arise to cause further condensation on the underside of the drip tray. By forming a drip tray of a material having a low thermal conductivity the air passing over the drip tray can warm the condensate, thus preventing the underside of the drip tray reaching a temperature below the dew point for air passing through the drip tray.
Thus, the provision of the insulation material or the use of drip tray components having a low thermal conductivity enables practical embodiments of air conditioning apparatus to be manufactured having a low overall height compared to systems utilising vertically disposed evaporator coils.

Claims

1. An air conditioning apparatus including an evaporator adapted to permit the flow of air in a downward direction therethrough, there being provided a drip tray to catch condensate in which the drip tray is formed in such a manner as to catch drops of liquid entrained in the flowing air, but which permits air to flow therethrough, the drip tray having a thermal conductivity less than that of metal.

2. A drip tray for air conditioning apparatus in which the air is passed in a downwards direction through an evaporator, the drip tray being formed in such a manner as to permit air to pass therethrough and to catch drops of liquid entrained in the air, the drip tray having a thermal conductivity less than that of metal.

3. Air conditioning apparatus including a housing adapted to be mounted in, on or adjacent to the roof of a room and to contain an evaporator for cooling air and a drip tray to catch drips of water formed by condensate of water vapour from air passing through the evaporator, characterised in that the drip tray is formed in such a manner as to permit the flow of air therethrough, but to catch drops of liquid entrained in the air, and in that those portions of the drip tray which have a downstream surface from which condensate may be carried into the air stream from the housing have a thermal conductivity lower than that of metal.

4. Apparatus as claimed in Claim 3 in which there is provided a horizontally disposed rotary scroll fan to pass air through the evaporator.

5. Apparatus as claimed in Claim 4 in which air is drawn into the housing from a grill mounted on the lower side thereof.

6. Apparatus as claimed in any one of Claims 1-5 in which the drip tray is formed of a series of side by side spaced strips of downwardly "S" shape in cross section interlinked so as to permit air to flow through the strips.

7. Apparatus as claimed in Claim 6 in which the strips are formed by a metal having a layer of insulating material on the lower surface.

8. Apparatus as claimed in Claim 6 in which the strips are formed of plastics material.

9. Apparatus as claimed in Claim 6 in which the drip tray is formed of a series of "V" or "U" shaped channels, each alternate channel being inverted and cooperating so as to catch drops passing therethrough.

10. Apparatus as claimed in Claim 9 in which the lower set of "V" or "U" shaped channels have an insulated underside.