AU737816B2 - Water bleed system for an evaporative cooler sump - Google Patents

Description

WO 98/40677 PCT/AU98/00161 1 WATER BLEED SYSTEM FOR AN EVAPORATIVE COOLER SUMP Field of Invention This invention relates to limiting the build-up of impurities in the water supply sump of evaporative coolers and the like.

Background Evaporative coolers have a sump for water, the level of which is maintained by a float operated valve controlling inlet water to the sump. During operation of the evaporative cooler, a pump draws water from the sump and delivers it to the top of evaporation pads through which the water trickles. Air passing through the pads is cooled by the evaporation of water. Surplus water reaching the bottom of the pads is returned to the sump.

In the course of prolonged operation, the effect of light and air contact can facilitate bacteria or algae growth in the water in the sump. Also, impurities arising from dissolved salts in the water may lead to encrustation due to progressive concentration of the sump water by evaporation. Impurities reduce the life of the evaporation pads and excessive salinity can impair efficiency of the evaporation process and can accelerate corrosion of metal components.

Known responses to these difficulties have involved either water bleed systems or dump systems. Known water bleed and dump systems have typically been ineffective, unreliable and expensive, causing difficulties for operators and manufacturers of such evaporative coolers.

Of known existing water bleed systems, there are two basic types. One uses the sump to collect water draining from cooler pads and discharges it to an overflow pipe. The water bleed rate is controlled by the location of the sump relative to the cooler pad(s) such that different amounts of water are collected according to that location. A second type of system pumps the water bleed to SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 2 a drain via a manually operated variable flow valve. Both these systems only bleed water when the pump is operating. That is, they leave the sump containing some water when the evaporative cooler is not in use so that the effect of evaporation, dust and light promoting algae growth fails to keep the level of impurities in the water at a desirably low level during periods when the cooler is not in service.

Dump valve systems generally comprise a dumping plunger and water inlet isolation means. Opening the dumping plunger on provision of some appropriate signal indicating a significant level of impurity causes water to be drained via a hole in the cooler's sump; during this stage an electronic valve is used to isolate the water inlet so the tank can be completely drained. This type of arrangement is preferable to the abovementioned water bleed system in that the tank is left dry when the cooler is not in use which prevents the growth of algae in the sump. It should be mentioned that in the closed position the plunger seals the hole in the sump and the inlet isolation valve is enabled to release water to allow the sump to be filled to the required operating level. The operation of the dumping of the water can be controlled either at timed intervals or with the switching off of the unit or by measuring some property of the sump water indicating a high impurity level.

Both the abovementioned systems have failed to perform totally satisfactorily in service, repeated problems being as follows:.

In bleed off system, since most require a small bleed orifice so as not to be wasteful of water, the bleed orifice is very prone to becoming blocked by solids present or other contaminants in the water as a result of prolonged use.

Bleed off systems where the bleed is pumped to drain particularly require a small orifice due to the relatively high pressure in the pumped circuit. As mentioned above, when the cooler is not operating for long periods, the water remains stagnant in the tank so encouraging algae growth and evaporates, so tending to deposit salt crystals.

SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 3 On the other hand, dump systems using a water actuated cylinder operate inconsistently due to the pressure relief orifice in the cylinder becoming blocked with solids in the water. Those type of dump systems using electrical actuators commonly fail by unreliability of the electrical parts. Dump valve outlets typically leak due to solids becoming caught between the tank and the plunger, preventing a continuous seal. Known dump systems are considerably more expensive than bleed systems because of their greater complexity.

Summary of the Invention Thus there is provided according to the invention a liquid storage control means associated with a liquid sump; having a liquid supply means to the sump capable of providing liquid at a high flow rate; a means for interrupting the liquid supply to the sump; a means for maintaining the liquid at an operating level in the sump when liquid supply is available to the sump; an outflow orifice adapted to drain water at a low flow rate from the surface of the liquid both when liquid supply is available to the sump and when liquid supplied to the sump is interrupted.

In a preferred form of the invention, the bleed orifice is buoyantly supported by liquid in the sump.

In a further preferred form the bleed orifice comprises an opening of variable cross-sectional area buoyantly supported to intersect the level of liquid in the sump.

In one particularly preferred embodiment of the invention, the bleed orifice is buoyantly supported to intersect the liquid level in the sump by adjustable means. Preferably that adjustable means comprises a series of V-shaped grooves having differing depth adjacent to each other and adapted to support SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 4 a pivotable attachment means adjacent to and movable with the liquid bleed orifice.

Brief Description of the Drawings The invention is further described by way of an example with reference to the accompanying illustrations in which: Fig 1 is a schematic cross-section of a part of the sump of an evaporative cooler according to the invention; Fig 2 is a schematic cross-section of the part of the sump of an evaporative cooler as shown in Fig 1 with the sump empty; and Fig 3 is a perspective view of water bleed system for an evaporative cooler sump of the invention as shown in Figs 1 and 2.

Fig 4 is a perspective view of a further embodiment of the invention; and Fig 5 is a perspective view of a tubular headpiece component of the embodiment shown i Fig 4.

Detailed Description of Preferred Embodiment and Variations.

With reference to Figs 1 to 3, the sump 10 of an evaporative cooler is shown with a sump bottom 12 and vertically upstanding overflow pipe 16. A water level 14 is maintained in the sump 10 by a water supply source and float valve (not illustrated) as is well known in existing evaporative coolers.

The invention is illustrated by reference to the following structure. A small diameter overflow branch 20 which may be situated low in the overflow pipe as a branch thereof is connected at a lower end to a connection tube 22, of flexible plastics material such as silicone rubber, PVC or the like which, at its other end, is inserted into a tubular headpiece 24. The other end of the SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 headpiece 24, opposite to its connection point to the connection tube 22, is provided with a slot 26 as will be described. An attachment means is provided on the headpiece 24 generally in the vicinity of slot 26, the connection point possibly being a pivot shaft 28 as illustrated or some arrangement performing a similar function.

On the surface of the water is a float chamber 30 which, as best seen in Fig 3, can be U-shaped. A transverse slot extends across both legs of the U-shaped float 30 parallel to the end of each leg of the float and is in the form of a series of parallel stepped slots 34 having progressively increasing depths from the upward facing surface of the float 30. The pivot shaft 28, headpiece 24 and Ushaped float 30 are complementarily sized as best seen in Fig 3 to enable the extreme top of the headpiece 24 to be maintained by the float above the water level in the sump 10. The outflow slot 26 in the headpiece is formed with a U shape extending from the top of the headpiece 24 and becoming radiused at its lower end. By means of the succession of grooves 34, transverse to the U shaped float legs, the outflow slot 26 may be adjusted relative to the depth of water in the sump and the buoyant equilibrium position of the float chamber by selecting a particular groove pair to support the headpiece 24 by the pivot shaft 28 such that whenever the sump contains water a small quantity of that water, from the surface 14 of the sump 10, flows into the connection tube 22 and out the overflow pipe 16. The height of the V shaped outflow slot 26 relative to the water level can be readily adjusted to increase or decrease the flow rate as may be found most effective given the varying concentrations of water contamination present at different geographical locations; in those locations where water impurity levels are relatively high, a relatively more rapid rate of bleed off is preferable.

With particular reference to Fig 2, when the evaporative cooler is to be taken from service, the unit including the pump is switched off whereupon a known type of automatic isolation valve (not illustrated) shuts off the water supply system to the sump. Water remaining in the sump continues to drain from the surface of the sump as described until, as shown in Fig 2, the connection hose SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 6 adopts a flat disposition along the bottom of the sump. Therefore, the sump is left substantially dry or with a minor residual water level that is capable of quickly evaporating. Alternatively, a specific shaping of the tank bottom and the position in which the connection hose 22 and headpiece 24 may lie when the tank is substantially empty can result in the tank bottom being left free of water to such a substantial extent such that it very quickly becomes totally dry.

One particular advantage of the described system is that the floating headpiece 24, by taking water from the surface 14 of the sump so allows the use of the relatively large bleed orifice slot 26 due to the absence of hydrostatic pressure at the water surface. This large bleed orifice is not prone to blockage of the drain path by solids in the water.

One particularly preferred embodiment of the invention is shown in Fig 4, in which the sump 10 of an evaporative cooler is again shown with a sump bottom 12 and vertically upstanding overflow pipe 16. The water level 14 is maintained in the sump 10 as before described. The small diameter overflow branch 20 situated low in the overflow pipe 16 as a branch thereof is connected to a lower end of the connection tube 22, in this case preferably of flexible silicone rubber which, at its other end is inserted into the tubular headpiece 24. The headpiece 24 opposite to its connection point to the connection tube 22, is again provided with a U-shaped slot 26. An attachment means is provided on the headpiece 24 and generally in the vicinity of the slot 26, the connection point being suitably a pivot shaft 28.

On the surface of the water is a float chamber 30 which is C-shaped and is located as a loose sliding fit over the overflow pipe 16, free to readily move up and down with the changing water level 14. Carried on the float chamber 30 is a form of parallel stepped slots 34 (not visible) but arranged at an inclined angle opposite the visible incline 35 and, similarly to Fig 3 enables adjustment of the relative height of the bottom edge of the slot 26 in relation to the adjacent water level 14. The U-shaped outflow slot 26 in the headpiece is SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 7 illustrated facing upward to show its principle but it is preferred to be actually assembled rotated 1800 relative to the connection tube 22 as illustrated. This is to enable the sump to drain to a very complete extent when the evaporative air conditioner is switched off.

The embodiment of Fig 4 operates analogously to that described in relation to Fig 2 but because the connection tube rises and falls in a hellical path centred around the overflow pipe 16, it leads to a more compact construction.

Fig 5 shows the tubular headpiece of Fig 4 in more detail: The U-shaped slot 26 and the pivot connection 28 are in Fig 5 visible, to a greater extent than in Fig 4.

A further advantage of the described system is that it can be fabricated at a relatively low cost and does not have the complication of known drain systems such as described in Australian patent AU-B 18201192 or equivalent or others listed as references at the conclusion of this specification. Likewise, the presently disclosed invention adds no additional electrical parts to fail. Unlike previously disclosed bleed only systems, with this invention the tank drains when not in use, to prevent the growth of algae, bacteria or other water breeding life forms in the sump.

The invention may be applied to installations other than evaporative coolers where there is often required a supply of liquid to be held in a storage tank so that the liquid is available when required. This may include such applications as refrigerated cooling systems where there is a requirement for stored liquid such as treated water used in a cooling tower for condensing coils of a refrigerated cooling system.

The invention disclosed therefore provides a much simpler, more effective and fail safe arrangement than known prior art sump drain systems including those disclosed in the following earlier references: SUBSTITUTE SHEET (RULE 26) WO 98/40677 PCT/AU98/00161 US 4422829 US 5374380 US 3963376 US 4966534 AU-A-52220/93 AU-B-18201/92 AU-A-65900/94 Sump drain system, Buchanan Salinity control of sump water using conductivity probes, James, assignee to FF Seeley Nominees Pty Ltd Automatic water powered sump drainer, Miskin Sump draining apparatus, Hasslen Control valve for draining a liquid storage tank in an air conditioning system, Nurex Pty Ltd Automatic drain plug for evaporative air conditioner reservoir, Pollution Control Pty Ltd Water control system for an evaporative air conditioner, Pollution Control Pty Ltd SUBSTITUTE SHEET (RULE 26)

Claims (4)

1. A liquid storage control means associated with a liquid sump; having a liquid supply means to the sump capable of providing liquid at a high flow rate; a means for interrupting the liquid supply to the sump; a means for maintaining the liquid at an operating level in the sump when liquid supply is available to the sump; an outflow orifice adapted to drain water at a low flow rate from the surface of the liquid both when liquid supply is available to the sump and when liquid supplied to the sump is interrupted.

2. A liquid storage control means associated with a liquid sump as claimed in claim 1 in which the outflow orifice is buoyantly supported by liquid in the sump.

3. A liquid storage control means associated with a liquid sump as claimed in claim 1 or claim 2 in which the outflow orifice comprises an opening of variable cross-sectional area buoyantly supported to intersect the level of liquid in the sump.

4. A liquid storage control means associated with a liquid sump as claimed in any one of the preceding claims in which the bleed orifice is buoyantly supported to intersect the liquid level in the sump by adjustable means. A liquid storage control means associated with a liquid sump as claimed in claim 4 in which the adjustable means comprises a series of U-shaped grooves having differing depth adjacent to each other and adapted to support a pivotable attachment means adjacent to and movable with the liquid bleed orifice. SUBSTITUTE SHEET (RULE 26)