GB2173117A - Aerating apparatus - Google Patents

Abstract

Aerating apparatus, e.g. for carbonation, comprises an enclosed outer chamber 1 with inlet ducts 7, 8 arranged in the upper part thereof for introducing gas and liquid under pressure into the chamber to establish a turbulent mixing zone 13 therewithin. This promotes dissolving of the gas by the liquid, aerated liquid being removed via an outlet duct 3. A tubular shroud 9 is arranged in the upper part of the chamber, the shroud communicating with the inlet ducts 7, 8 and being effective to channel the inlet gas and liquid downwardly into the turbulent mixing zone 13. The mixing zone may be located in an inner chamber 2, which is closed at its lower end. <IMAGE>

Description

SPECIFICATION Aerating apparatus This invention relates to aerating apparatus, that is apparatus for dissolving a gas in a liquid, and is particularly, though not exclusively, concerned with such apparatus for dissolving carbon dioxide in water to produce carbonated water suitable for use in drinks.

A known type of aerating apparatus comprises an enclosed vessel into which gas and high pressure liquid are introduced via respective inlet ducts provided at the top of the vessel so that a highly turbulent mixing zone consisting of a so-called matrix of gas bubbles is formed within the vessel which, owing to the high turbulence and large gas/liquid interface, promotes rapid dissolving of the gas by the liquid. The aerated liquid collects at the bottom of the vessel and is discharged therefrom via a suitable outlet duct which communicates with the lower part of the vessel interior and which is shielded from the turbulent mixing zone by means of a suitable baffle member.The aerated liquid may be drawn off as required by means of a suitable pump or alternatively may be discharged to a dispensing point under the pressure of the gas in the vessel; the level of the aerated liquid in the vessel may be regulated by suitable sensor means adapted to control the high pressure inlets of gas and liquid in order to maintain the volume of aerated liquid in the lower part of the vessel between appropriate upper and lower limits.

Such apparatus is commonly used e.g. in bars, restaurants and hotels to provide a source of carbonated water for non-alcoholic drinks dispensed directly to the glass from taps. The apparatus is relatively simple mechanically and thus inexpensive to manufacture and install and is reliable in operation.

With such known apparatus experience has however shown that the efficiency, i.e. the proportion of the inlet gas which is dissolved by the liquid, of the apparatus is partly dependent on the rate at which aerated liquid is drawn off from the vessel and it is therefore difficult to achieve a substantially constant level of aeration for differing output rates. The reason for this appears to be that when there is no outlet flow from the vessel, the level of the aerated liquid within the vessel increases as more high pressure liquid and gas is introduced into the vessel, and such as increase in the liquid level is effective to raise the pressure in the mixing zone which in turn promotes an increase in the volume of gas dissolved.

However, where aerated liquid is drawn off from the vessel during the aerating operation, as may often occur during normal use in a bar, the outlet flow rate may be substantially equal to the high pressure inlet flow rate so that the liquid level in the lower part of the vessel remains substantially constant. In this event, the pressure increase discussed above does not occur, and the amount of gas dissolved by the liquid is not increased.

In a known carbonating system where the high pressure inlet flow rates of carbon dioxide and water are chosen to provide a carbonation level of approximately 4 volumes (i.e. a carbon dioxide to water ratio of 4:1 by volume) it has been found that a high proportion of the gas is absorbed when there is no outlet flow, whilst when the outlet and inlet flow rates are substantially equal the absorption drops sharply. Whilst such delivery rate-dependent variations in the level of aeration are acceptable in the case of highly carbonated soft drinks, applications may be envisaged where a more constant level of aeration is required over a wider range of aeration.

According to the invention there is provided aerating apparatus comprising an enclosed outer chamber, means arranged in the upper part of the chamber for introducing liquid under pressure and a gas into the chamber so that in use a turbulent mixing zone is established therewithin which promotes dissolving of the gas by the liquid, and an outlet conduit for the discharge of aerated liquid from the chamber, wherein said introducing means includes a tubular shroud which communicates with inlet ducts for said gas and liquid and which projects downwardly into the interior of the chamber whereby an incoming mixture of liquid and gas is channeled downwardly by the shroud and in normal use is thereby introduced into said turbulent mixing zone formed within the chamber below the upper level of the mixing zone.

In accordance with the invenion it has been found that the consistency of absorption is such that at least over a certain range of gas and liquid inlet flow rates and operating temperatures almost all of the gas introduced into the chamber is dissolved regardless of the rate at which aerated liquid is drawn off.

Thus, by providing constant inlet flow rates and a constant operating temperature a predetermined level of aeration may be obtained which is substantially unaffected by pressure variations in the chamber consequent upon whether the liquid level therein is raised or remains constant during operation, and accordingly the variations in the volume of gas dissolved with changes in output flow rate associated with known apparatus of this type may be significantly reduced.

The apparatus is applicable to any system where an aerated liquid is required having a substantially constant aeration level. Thus, apparatus in accordance with the invention is particularly suitable for providing supply of carbonated water which may be mixed with a concentrate and thereafter dispensed directly via suitable.taps in an establishment such as a bar or restaurant.

In apparatus of this type, it is generally necessary to shield the entrance to the outlet conduit from the turbulent mixing zone since otherwise there -is- an increased tendency for bubbles of undissolved gas to be discharged from the outer chamber, and therefore apparatus in accordance with the invention preferably includes a baffle member arranged to so shield the entrance to the outlet duct. It is envisaged that the baffle member could simply comprise a horizontal plate extending partially across the chamber in thelower part thereof, the outlet duct communicating with the region below the plate where the aerated liquid is shielded from the turbulent mixing zone formed above the plate.In a particularly advantageous embodiment, however, a tubular inner chamber is provided within the outer chamber, such inner chamber being closed at its lower end and open at its upper end, the arrangement being such that the shroud extends partially into the interior of the inner chamber. Thus, in this embodiment at least a major part of the turbulent mixing zone is contained by the inner chamber, the aerated liquid spilling over the top of the inner chamber and collecting in the lower region of the outer chamber which thus acts as a reservoir.

The outlet duct communicates with the lower part of the outer chamber and is thus shielded from the turbulent mixing zone by the inner chamber. The provision of an inner chamber which contains the mixing. zone is- preferable not only to provide a liquid reservoir which is shielded from the mixing zone, but is also advantageous- in that in normal use the upper level of the mixing zone always lies in; the region of the top of the inner chamber, and the vertical extent of the mixing zone does not vary with changes in the level of the aerated liquid collected in the outer chamber.Thus, so long as the inlet shroud terminates below the top ofthe inner chamber and sufficient high pressure liquid and gas is introduced: into the chamber to establish the required turbulent mixing zone or bubble matrix, it will be- ensured that the mixture of liquid and gas is introduced into the mixing zone below the upper level thereof, regardless of the volume of aerated liquid in the outer chamber.

In a preferred embodiment, high pressure liquid is pumped into the chamber via a nozzle-like ductor ducts communicating with the upper end of the shroud so that high velocity downwardly directed liquid.

jets are formed therein, whilst the gas is introduced into the shroud laterally via a duct communicating with the shroud- part of the way along its length. In this way the gas -is entrained and carried downwardly into the mixing zone bathe high pressure liquid jets. Experience has suggested that if an insufficient quantity of gas passes into the shroud for entrainment by the liquid then.an adequate turbulent mixing- zone or bubble matrix for efficient operation will not be established, and this could present problems where lower levels of aeration are required and accordingly the maximum. overall flow rate of gas into the apparatus is restricted.Therefore, in a preferred embodiment, a venting aperture of apertures is/àre formed in the side wall of the shroud, which permit gas present in the upper part of the interior of the chamber to be drawn into the shroud for re-entrainment by the liquid, so that a sufficient quantity of gas is always permitted to enter the shroud, even when the required inlet gas flow rate into the apparatus is relatively low.

As with known apparatus of this type, suitable sensors may be provided to sense the level of the aerated liquid collected in the chamber and to control the inlet supplies of high pressure liquid :and gas in order to maintain the liquid level between desired upper and lower limits. The outlet conduit may conveniently comprise a tube projecting downwardly into the interior of the chamber and terminating near thebase Thereof. The aerated liquid may be pumped from the chamber, or alternatively discharged via the outlet conduit under the internal gas pressure.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing. which is a partly schematic side elevation in cross-section of an aerating apparatus suitable for producing carbonated water.

The apparatus compnses an enclosed outer chamber 1 mounting therewithin a tubular inner chamber 2 which is closed at its lower end and open at its upper end. The chambers may be formed of arty suitable corrosion resistant material. A tubular outlet duct 3 extends downwardly into the outer chamber 1 and terminates near the base thereof, and liquid level sensing means are provided in the form of resistance probes 4 protected by an apertured housing 5.

A lid assembly 6 is sealingly engaged with the top of the outer chamber 1 and releasably clamped thereto by suitable means (not-shown). The lid assembly carries means for introducing- high pressure liquid e.g. water and a gas e.g. carbon dioxide into the chamber in the form of respective inlet ducts 7,38 communicating with a tubular shroud 9 which projects downwardly from the lid assembly and terminates within the inner chamber 2 below the upper edge thereof.The shroud is fixed in s-paced- relation-to the inner chamber2 by means of circumferentially spaced bolts 12. In the illustrated embodiment the shroud is approximately 4 1/4 ins. in length, 1 1/4 ins. in diameter and extends approximately 1 3/4 ins.

below the upper edge of the inner chamber 2. The inner chamber itself measures approximately 3 ins. in width and 18 ins. in height, whilst.the largest dimensions of the outer chamber 1 are 8 ins. in width by 22 ins. in height.

In use of the apparatus, water is pumped into the inlet duct 7 at high pressure, and enters the shroud 9 via four spaced nozzles (not shown) provided in the lid assembly 6, such that downwardly directed waterjets are formed in the shroud. Carbon dioxide is introduced laterally into the shroud via a conduit 10 communicating with the-interior of the shroud approximately midway along its length, such that the car bon dioxide is entrained by the high pressure jets. Additional gas may enter the shroud 9 for for.entrainment.

bythe jets via a small venting aperture 11 formed in the side wail of the shroud. The ingress of high pressure liquid and gas is effective to establish a highly turbulent mixing zone 13 consisting of a matrix of bubbles within the inner chamber, the incoming liquid and gas being introduced into the mixing zone below the upper level of the bubble matrix during normal i.e. equilibrium operation. The.high turbulence and large gas/liquid interface in the mizing zone promotes rapid solution- of the gas by the liquid, the carbonated liquid spilling over the top of the inner chamber 2 and collecting in the outer chamber 1 which acts as a reservoir.Carbonated liquid may then be drawn off from the outer chamber 1 as required either by gas pressure or by means of a suitable pump, e.g. for mixing with a suitable concentrate to produce an aerated beverage which may thereafter be directly dispensed via a suitable tap in an establishment such as a hotel, bar or restaurant, or even in the home.

The level of the carbonated liquid in the outer chamber 1 is maintained between desired upper and lower limits by means of the probes 4 which control a high pressure pump (not shown) for the supply of the inlet liquid to the apparatus.

In a preferred embodiment, the operating parameters have been varied as follows: Water input rate (constant) : 1.25GFM Carbonation range (set by varying CO2 pressure) : 0.5 to 2.5 volumes Temperature range : 10-30"C Carbonated water output range : 0.5 to 2GPM For any desired carbonation level within the quoted range, which was set by selecting an appropriate inlet gas pressure for a given water temperature, the maximum variation from the desired level which occured was +0.15 volumes over a range of output flow rates of 0.5 to 2GPM.

Claims (8)

1. Aerating apparatus comprising an enclosed outer chamber, means arranged in the upper part of the chamber for introducing liquid under pressure and a gas into the chamber so that in use a turbulent mixing zone is established therewithin which promotes dissolving of the gas by the liquid, and an outlet conduit for the discharge of aerated liquid from the chamber, wherein said introducing means includes a tubular shroud which communicates with inlet ducts for said gas and liquid and which projects downwardly into the interior of the chamber whereby an incoming mixture of liquid and gas is channeled downwardly by the shroud and in normal use is thereby introduced into said turbulent mixing zone formed within the chamber below the upper level of the mixing zone.

2. Aerating apparatus as claimed in claim 1 further comprising a baffle member arranged to shield the entrance to the outlet duct from said turbulent mixing zone.

3. Aerating apparatus as claimed in claim 2 wherein the baffle member comprises or forms part of an inner chamber provided within the outer chamber, such inner chamber being closed at its lower end and open at its upper end, the arrangement being such that the shroud extends partially into the interior of the inner chamber.

4. Aerating apparatus as claimed in any preceding claim wherein high pressure liquid is pumped into the chamber via a nozzle-like duct or ducts communicating with the upper end of the shroud so that high velocity downwardly directed liquid jets are formed therein, whilst the gas is introduced into the shroud laterally via abduct communicating with the shroud part of the way along its length.

5. Aerating apparatus as claimed in any preceding claim comprising a venting aperture or apertures formed in the side wall of the shroud.

6. Aerating apparatus as claimed in any preceding claim comprising sensors adapted to sense the level of the aerated liquid collected in the chamber and to control the inlet supplies of high pressure liquid and gas in order to maintain the liquid level between desired upper and lower limits.

7. Aerating apparatus as claimed in any preceding claim wherein the outlet duct comprises a tube projecting downwardly into the interior of the outer chamber and terminating near the base thereof.

8. Aerating apparatus substantially as herein described with reference to the accompanying drawing.