GB2059286A

GB2059286A - Process and system for humidifying air for air-conditioning

Info

Publication number: GB2059286A
Application number: GB8030609A
Authority: GB
Original assignee: Luwa Ltd
Current assignee: Luwa Ltd
Priority date: 1979-09-28
Filing date: 1980-09-23
Publication date: 1981-04-23
Also published as: FR2466709A1; DE3036344A1; IT1133138B; JPS5656546A; GB2059286B; ES495678A0; ES8201721A1; IT8024863A0

Abstract

Air which has been drawn in by means of a fan-wheel (30) is subjected to humidification in a first humidification stage (I), where water emerging from an annular chamber (16) is whirled up and disintegrated into droplets of wide size spectrum by the blades of a fan-wheel (30). The air is led through a drop-separator (36), which separates out the large drops, but allows the fine water droplets, which are required for humidifying and cooling the air to pass through. At a second, downstream, humidification stage (II) a second humidification stage takes place with the air being subjected to a water fog containing very small water droplets. <IMAGE>

Description

SPECIFICATION Process and system for humidifying air for airconditioning The present invention relates to a process of and apparatus for humidifying air wherein the air is humidified in two successive stages along its direction of flow In air-conditioning systems having long air ducts, the moisture content of air which has been humidifed in a humidification stage decreases as it flows along such ducts due to the separation of water drops from the air. In order to restore the moisture content of the air to its original value before use, that is to make good the losses caused by such separation of drops, it is known to provide a second humidification stage, which is normally located at a considerable distance from the first humidification stage.Due to the normally large distance between the humidification stages, the air when it reaches the second humidification stage no longer contains large water drops, onto which the water droplets produced in the second humidification stage could deposit and thus tend not to humidify the air further.

The aim of the present invention is to provide a process of and apparatus for air-conditioning having improved efficiency, and by which a high degree of saturation and even super-saturation of the air can be obtained in a simple manner.

According to one aspect of the present invention there is provided process for humidifying air for air-conditioning, in which the air is humidified with water droplets in two stages occurring successively in the air flow direction wherein droplets introduced in the first stage and having a size exceeding a specified value are separated out from the air after the first stage, and the moisture content of the air is increased in the second stage relative to the moisture content of the air emerging from the first humidification stage using only small water droplets.

According to another aspect the present invention provides air-conditioning apparatus having first and second humidifying stages at which the air is humidified by water droplets, arranged in the flow direction of the air, wherein a drop-separator is arranged between the two humidification stages to remove from the air droplets introduced in the first stage and exceeding a specified size.

With the present invention, in the first humdification stage, in which water drops of a wide range of sizes are produced, an initial humidification takes place, by means of which the moisture content of the air is brought up to a first value, that to say to a base value. In the second humidification stage, in which the water used is finely atomised, the moisture content of the air is increased to a second, higher, value. Since, in practical terms, only a supplementary humidification is required in this second humidification stage, the exact extent depending on the moisture content of the air emerging from the first humidification stage, fine water atomisation can be employed with a comparatively low expenditure of energy.In this way, highly saturated and supersaturated air can be produced, without great expenditure on energy and equipment, irrespective of the moisture content of the air entering the first humidification stage.

All of those water drops contained in the air emerging from the first humidification stage which exceed a specified size, and onto which the fine water droplets used in the second humidification stage could deposit, are separated out in the dropseparator. By this means, the loss, in or after the second humidification stage, of fine water droplets, which are desired for the humidification and cooling of the air, is avoided. In addition, an undesired deposition of water drops on the air duct walls can be prevented. The fine water drops which are produced in the first humidification stage and whose presence in the air flow is desired, pass straight through the drop-separator.In contrast to the known processes involving two stage humidification, the distance between the two humidification stages can be kept comparatively small, since no great distance is required for the separation of the large drops.

Preferably, in the present invention, the distance between the first humidification stage and the drop-separator is larger, preferably at least twice as large, than the distance between the drop-separator and the second humidification stage.

In a preferred embodiment, the water atomising device of the first humidification stage possesses at least one fan-wheel which is acted on by water. By using the fan-wheel both for delivering the air and also for the water atomisation, a simple and compact construction is obtained. It is additionally advantageous if the drop-separator simultaneously serves as a flow-redresser.

The invention will be more clearly understood from the following description which is given by way of example only with reference to the accompanying drawings in which the sole Figure shows, in schematic longitudinal section, a portion of an airconditioning system containing the humidification section of the invention.

In the drawing, a tube of duct section 10 has an intake nozzle 12 at its inlet end. Next to the nozzle 12, in the flow direction A, the tube section 10 possesses a part 14, of U-shaped cross-section which defining an annular chamber 16 which extends around the entire periphery of the tube section 10. This annular chamber 16 possesses an outlet opening, in the form of an annular gap 16a, directed towards the interior of the tube section 10. However, this or other outlet openings can have a different configuration. Two water feed pipes 18 and 20 open into the annular chamber 16 and are connected to the pressure side of a water pump 22. The suction side of this pump 22 is connected to a sump 24 of a water reservoir 26, which is provided with an overflow pipe 28. A fan-wheel 30 carrying fan blades is located in the region of the annular chamber 16, and is driven by a drive motor 32.The fan-wheel 30 draws the air to be treated through the intake nozzle 12 and delivers the air through the tube section 10. Upstream of the fan-wheel 30, namely on its side facing the incoming air is a water feed line 34 which has an outlet in the region of the hub 30a of the fan-wheel 30, this water feed line also being connected to the pressure side of the water pump 22. A plurality of such water feed pipes can be provided, with their outlets in the region of the hub 30a. These parts together constitute a first humidification stage I.

A drop-separator 36 for separating large droplets from the airflow is located downstream of the fan-wheel 30 and has a drain pipe 38 opening into the water reservoir 26. Water separated in the separator 36 flows through the drain pipe 38 into the sump 24, as indicated by the arrow 40, so that separated water is recirculated.

The drop-separator 36 is preferably also designed as a silencer. At the same time, it is also advantageous to design the drop-separator 36 as flowredresser. This combination of drop-separation and flow-redressing in the same component offers the advantage of a compact form of construction.

A second humidification stage II is located downstream of the drop-separator 36 and has a number of atomising nozzles 42, arranged at uniform intervals on the periphery of the tube section 10. These nozzles 42, which form the second humidification stage 11, are located at a comparatively small distance from the drop-separator 36, this distance being smaller than the distance between the fan-wheel 30 of the first humidification stage land the dropseparator 36. The distance between the fan-wheel 30 and the drop-separator 36 amounts to at least twice, and usually several times, the distance between the drop-separator 36 and the atomising nozzles 42 of the humidification stage II.

The nozzles 42, which are preferably made of two materials for strength and long life, are connected, via a line 44, to a source 46 of compressed air and, via a second line 48, to a source 50 of water under pressure. The local water supply system can form the water source 50. The pressurised water source 50 is connected, via an additional line 52, to the reservoir 26. A float-actuated valve 54 is located in the line 42. Valves 56 and 58 are similarly fitted in the lines 44 and 48, these valves, together with the water pump 22, being controlled by means of a control unit 60, in a manner known per se. A hygrostat 62 is connected to the control unit 60.

When the air-conditioning system is operating, the rotated fan-wheel 30 draws in air from the surroundings, through the intake nozzle 12, and delivers the air through the tube section 10. The water pump 22 delivers water to the annular chamber 16, via the water feed pipes 18 and 20. The water emerges, through the annular gap 16a, into the interior of the tube section 10, in the form of a film. This water film is whirled up and disintegrated by the blades of the fan-wheel 30, so forming water drops having a size spectrum from very fine droplets to larger water drops. This atomisation of the water by the fanwheel 30 is adequate for certain operating conditions and for certain conditions relating to the air on entry. If necessary, water can additionally be fed into the region of the hub 30a, via the water feed line 34.

The water emerging from the line 34 is disintegrated by shearing forces produces by the blades of the fan-wheel 30 and is atomised to droplets of a range of size from fine to large.

The air, which has been brought in this way to a specified moisture content in the first humidification stage I, flows between the fan-wheel 30 and the drop-separator 36 which serves as a humidification section. Water drops which are too large, i.e. those having a size exceeding a specified value, are separated from the air flowing through this dropseparator 36 and are fed back to the reservoir 26 through the drain pipe 38. Only the large drops are selectively separated in the drop-separator 36, while the small droplets needed for humidifying and cooling the air are maintained and are likely to precipitate in the absence of large drops. These desired small water droplets can pass, unhindered, right through the drop-separator 36. As already mentioned, the drop-separator 36 can also serve for redressing the air flow, that is to say for eliminating rotation of the air.

The initially humidified air reaching the second humidification stage II is subjected, by means of the atomising nozzles 42, to a water fog containing only very small water droplets. By means of these droplets, the moisture content of the air is increased relative to the moisture content of the air upon leaving the first humidification stage I, and a high degree of saturation of the air, or even supersaturation, is achieved. In contrast to the first humidification stage I, the spectrum of the water droplets produced in the second humidification stage II is very narrow. The "Sauter diameter" characterising the drop spectrum of the second humidification stage il is preferably related to the characterising "Sauter diameter" of the first stage by the ratio of up to about 1:10.Specialists skilled in the art are aware that the "Sauter diameter" serves as an important indicative parameter with regard to the quality and uniformity of a drop spectrum.

The two-stage humidification, as described, enables highly saturated and super-saturated air to be obtained, irrespective of the physical characteristics of the air entering the intake nozzle 12. The initial humidification in the first humidification stage I produces a favourable starting situation for the further humidification procedure in the second humidification stage II. Since the humidification in the second stage II starts from a base value of the air moisture content, the expenditure of energy for the atomisation in this second humidification stage is relatively low. Highly saturated and super-saturated air can thus be produced, under all conditions at the air intake, with a comparatively low total energy expenditure.

It is self-evident that the design of the airconditioning system described in the preceding text can be different, with respect to various features, from that shown.

Thus, any suitable water atomising device, capable of producing the necessary quantity of water drops having the desired drop spectrum, can be employed in the first humidification stage I. The fan for delivering the air can also be located separated from the water atomisation device. However, the utilisation of the fan-wheel 30, which delivers the air, for the water atomisation, as described, possesses the advantage of allowing a simple and space-saving form of construction.

Other types of atomising nozzle, for example, high pressure nozzles, can be used in the second humidification stage II, instead ofthetwo-material nozzles 42. Any suitable device for the fine atomisation of water may, of course, be employed in the second humidification stage II.

If necessary, each ofthe humidification stages I and II can consist of two or more partial stages. For example, several rows of atomising nozzles 42 may be located along the flow direction A.

In a preferred embodiment, the separating-baffles in the drop-separator 36 are hollow and a suitable coolant is introduced into them.

Claims

1. Process for humidifying airforairconditioning, in which the air is humidified with water droplets in two stages occurring successively in the air flow direction wherein droplets introduced in the first stage and having a size exceeding a specified value are separated out from the air after the first stage, and the moisture content of the air is increased in the second stage relative to the moisture content of the air emerging from the first humidification stage using only small water droplets.

2. Air-conditioning apparatus having first and second humidifying stages at which the air is humidified by water droplets arranged in the flow direction of the air, wherein a drop-separator is arranged betwen the two humidification stages to remove from the air droplets introduced in the first stage and exceeding a specified size.

3. Air-conditioning apparatus according to claim 2, wherein the distance between the first humidification stage and the drop-separator is larger, and preferably at least twice as large, than the distance between the drop-separator and the second humidification stage.

4. Air-conditioning apparatus according to claim 2 or 3, wherein the second humidification stage includes at least one device for finely atomising water.

5. Air-conditioning apparatus according to claim 4, wherein the device for finely atomising water includes an atomising nozzle, preferably a twomaterial nozzle or a high pressure nozzle.

6. Air-conditioning apparatus according to claim 5, wherein the or each atomising nozzle is connected to a source of compressed air and to a source of water under pressure.

7. Air-conditioning apparatus according to any one of claims 2 to 6, wherein the first humidification stage includes a water atomising device, which produces water drops of wide range of sizes.

8. Air-conditioning apparatus according to claim 7, wherein the water atomising device of the first stage includes a fan-wheel which is acted on by water.

9. Air-conditioning apparatus according to claim 8, wherein there is a water supply which directs water to act on the fan-wheel at its periphery.

10. Air-conditioning apparatus according to claim 9, wherein an annular chamber connected to a water feed line is provided around the fan-wheel and this chamber includes at least one outlet opening directed towards the fan-wheel.

11. Air-conditioning apparatus according to claim 10, wherein the outlet opening is an annular gap.

12. Air-conditioning apparatus according to claim 10, wherein the water feed line is connected to a reservoir, into which the outlet of the dropseparator opens.

13. Air-conditioning apparatus according to any one of claims 8 to 12, wherein the water atomising device includes at least one water feed line, with an outlet in the region of the hub of the fan-wheel.

14. Air-conditioning apparatus according to any one of claims 2 to 13, wherein the drop-separator is designed in the form of a flow-redresser.

15. Air-conditioning apparatus according to any one of claims 2 to 14, wherein the drop-separator is designed in the form of a silencer.

16. Air-conditioning apparatus according to any one of claims 2 to 15, wherein separating-baffles of the drop separator are provided with cavities in which a coolant is circulated.

17. Air-conditioning apparatus constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

18. A process for humidifying air substantially as hereinbefore described with reference to the accompanying drawing.