EP2070587B1

EP2070587B1 - Refrigerator comprising a beverage dispenser, and method for dispensing a refrigerated beverage

Info

Publication number: EP2070587B1
Application number: EP07023987.6A
Authority: EP
Inventors: Daniel L. Johansson; Susanne Hedblom; Giuseppe Pol; Thomas Volker
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2007-12-11
Filing date: 2007-12-11
Publication date: 2013-05-29
Anticipated expiration: 2027-12-11
Also published as: EP2070587A1; PL2070587T3; ES2426347T3

Description

The present invention concerns a refrigerator provided with a water/liquid beverage carbonation system and a method for dispensing a refrigerated beverage.
There are various carbonation systems known in the art, which permits the production of carbonate water on a demand basis.
Commonly, on demand systems utilize specialized apparatus, so called in-line carbonators (where the carbonation is carried out at the time of dispensing the beverage), for combining water and carbon dioxide (CO₂) (or any other gas, for example oxygen, or to enhance the mixing and/or area of contact there between.
US 6,060,092 discloses a device for carbonation of drinking water in a continuous in-line process comprising a water supply line provided with a pressurizing pump adapted to feed an injector nozzle which projects into a mixing tube fluidly connected to a CO₂ supply line having a predetermined low working pressure, into which CO₂ is sucked and then mixed with the water. Because of the high intake pressure of the injector the flow velocity of the water in the injector nozzle is increased so greatly that CO₂ is sucked in by the reduced pressure that results at the end of the nozzle and is delivered under turbulence conditions into the mixing tube.
This in-line carbonator is extremely complex. It requires high pressure in the water supply line and low pressure in the CO₂ supply line and most of all a predetermined difference between such pressures is needed in order to ensure the effective operation of the carbonator. Hence, the right pressures balance has to be maintained during the usage of the system.
WO 98/47812 discloses a water carbonation system comprising a source of pressurized CO₂ connected to a gas line having a flow restrictor adapted to deliver CO₂ at a predetermined pressure above that of the water to a T-fitting. A pump is connected to a source of potable water and serves to pump the water along the water line to the T-fitting. The CO₂ and water are initially mixed at the T-fitting and flow therefrom through an in-line carbonator and along the carbonated water line to the dispenser point.
Other on demand systems, as disclosed in WO 2005/105279 and WO 2006/114086 , utilize in-line carbonator comprising structures filled with bulky material to enhance the mixing between CO₂ and water.
A drawback of these carbonation systems is that at the liquid/gas mixing point a predetermined and precise gas working pressure value is required with respect to the liquid working pressure value for effectively introducing the gas into the liquid.
In practise, the carbonation system has to supply the gas to the liquid/gas mixing point with a determined pressure value according to the pressure value of the liquid which is delivered to liquid/gas mixing point.
For this reasons, the CO₂ supply line of these carbonation systems includes check valve arranged upstream the liquid/gas mixing point for controlling and precisely adjusting the pressure value of the gas upon the installation of the carbonation system and for maintaining such a pressure value constant during usage of the latter. Therefore, these carbonation systems are poorly flexible and need a continuous adjustment.
A further drawback of these carbonation systems is that a high liquid pressure value is needed at the liquid/gas mixing point for achieving a satisfactory level of carbonation. Therefore, the liquid supply line must include a pressurizing or booster pump arranged upstream the liquid/gas mixing point in order to increase the pressure value of the liquid to be carbonated.
It is clear that all these pressure requirements make these carbonation systems complex and costly.
In addition, the components, which have to be used in order to comply with the above-mentioned pressure requirements (pumps and regulation valves), make these carbonation systems unreliable and subject to malfunctions.
The document US-A-4 915 261 discloses a carbonated beverage dispensing system for dispensing a mixed beverage consisting of a flavoring constituent contained in an individual serving packet and a base liquid. The dispensing system includes an actuating unit having a platen that is movable between a retracted position in which a flavoring constituent containing packet is positionable into the actuating unit with a rupturable discharge end thereof directed downwardly and an actuated position which progressively presses against a side of the packet for forcing the contents of the packet in a downward direction for rupturing the discharge end of the packet and for expelling the contents thereof into a discharge nozzle. A carbonated water supply is provided for simultaneously dispensing a predetermined quantity of carbonated water into the nozzle for mixing with the expelled flavoring constituent prior to discharging therefrom. The carbonated water supply is adapted for substantially instantaneously carbonating fresh water as it is being dispensed to the mixing nozzle.
The document GB-A-1 441 658 discloses a water carbonator comprising, in the direction of water flow, a first stage in which CO2 is drawn from a source at lower pressure than that of the water by aspiration into the water and partly absorbed therein, and a second stage in which the water with partly absorbed CO2 is accelerated, to decrease static pressure and increase turbulence, so that the surface area of the water exposed to the CO2 is increased to achieve substantially complete CO2 absorption. Preferably, the water pressure is 90-95 psi, the CO2 is 2-5 psi less than the water pressure, and the water temperature is between 32-40 F. A stage is provided comprising an annular chamber receiving CO2 through an entry port, an inner chamber receiving CO2 from a chamber through radial ports, and axial water flow passages communicating with a water inlet port and each intersecting at least one radial CO2 aspiration passage. The stage comprises a conical chamber having a wall tapering to a throat which communicates with a collection chamber. The taper angle of the wall is preferably less than 45. The cross sectional area of the water inlet port exceeds the total cross sectional area of the passages which in turn exceeds the cross sectional area of the throat. In operation, water passing through the passages draws CO2 radial inwards and outwards respectively from the chambers the entrainment of CO2 molecules causing water flow turbulence and part CO2 absorption. Water streams ejected from the passages are impinged against the chamber wall and are then combined at the throat to enter the collection chamber, the acceleration towards the throat causing decreased static pressure and increased turbulence. In the arrangement of Fig. 1, water from a tank is pumped through a cooler to a line having carbonators disposed in parallel. Pressure in the line is determined by a pressure regulating valve relieving to atmospheric pressure. As alternatives, the pump may be disposed downstream of the cooler, and the latter may cool the water whilst in the tank. The valve and a CO2 pressure regulating valve are operatively interconnected. The outlet from each distributor comprises a push button opened faucet which may be fixed directly to the carbonator body. The cooled water and CO2 may be fed to the carbonators through flexible lines. Cooled pressurised water for the carbonator may be provided from a coil in, or in the wall of, a conventional refrigerator.
The document US-A-3 761 066 discloses an inline water carbonator which introduces CO2 and fresh water into a conduit leading to a carbonated water dispensing valve each time the valve is opened. The CO2 and water are thoroughly mixed in the conduit as the carbonated water is dispensed through the valve so that the water is charged with CO2 when it is dispensed.
The document EP-A-1 614 986 discloses a refrigerator door with a carbonator installed therein includes a heating device provided at an inner portion of the refrigerator door, for supplying heat to the carbonator. The refrigerator door further includes a temperature detecting device for measuring a temperature of the carbonator and then generating a signal indicating the measured temperature; and a controller for controlling the heating device according to the signal from the temperature detecting device. If the temperature of the carbonator is lower than or equal to a preset operation temperature, the controller controls the heating device to generate heat.
The document EP-A-1 580 502 discloses a refrigerator capable of fabricating a carbonated water including a water vessel, a mounting area for mounting therein the water vessel, and a dispenser unit for carbonising the water in the water vessel, the water area having a changeable vertical distance. Further, the mounting area has a first area with a specific height and a second area a predetermined height formed under the first area, the second area being selectively opened to communicate with the first area.
It is therefore a main object of the present invention to provide a refrigerator, which is effective in reducing the above-noted drawbacks of the cited prior art.
According to the present invention, this aim, along with further ones that will become apparent in the following disclosure, is reached by a refrigerator according to claim 1, and a method for dispersing a refrigerated beverage according to claim 12.
Features and advantages of the present invention will anyway be more readily understood from the description that is given below with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a refrigerator according to the present invention;
Figure 2 is a schematic view of a refrigerator according to a further embodiment the present invention;
Figure 3 is an enlarged sectional view of the carbonation inlet port of figure 1;
Figure 4 is an enlarged sectional view of the carbonation inlet port of figure 2;
Figure 5 is a graph showing the CO2 concentration of the dispensed liquid beverage in function of the CO₂ working pressure value in bar with and without the carbonation inlet port of figure 1 and 3;
Figure 6 is a graph showing the CO₂ concentration of the dispensed liquid beverage in function of the CO₂ working pressure value in bar with and without the carbonation inlet port of figure 2 and 4;

With reference to the above-cited Figures, the beverage dispenser, as generally indicated with the reference numeral 1, of the refrigerator comprises a liquid beverage supply line 2 fluidly connected to a water source 3, a carbon dioxide supply line 4 fluidly connected to a pressurized carbon dioxide source 5, al least one mixing device 6 for carbonating the liquid beverage, an carbonation inlet port 7 fluidly connecting the carbon dioxide supply line 4 to the liquid beverage supply line 2 or to the mixing device 6 for introducing carbon dioxide into the liquid beverage, a dispenser point 8 for dispending the carbonated liquid beverage.
The carbonation inlet port 7 has reduced flow cross-section for generating frictional resistance adapted to reduce the velocity of the carbon dioxide flow entering into the liquid beverage supply line 2 or into the mixing device 6 to a predetermined value.
The liquid beverage supply line 2 of the beverage dispenser can be connected directly to the water supply mains (for example the municipal water supply mains) through a suitable connection or alternatively the water source 3 can be in the form of a pressurized tank. Normal building water pressure is sufficient
The liquid beverage supply line 2 connects the water source 3 to a water pressure reducer 9 which is adapted to reduce the water pressure to a specified working pressure value, for example of 2 to 3 bar, in order to have the same starting conditions for the processing procedure independent of the pressure value of the water supply mains.
In practice, the water pressure reducer 9 renders the pressure value of the incoming water constant so as to avoid the problems connected to the pressure value fluctuations which normally affect the municipal water supply mains.
In an embodiment which does not form part of the present invention, it can however be most readily appreciated that in case the water is supplied via a pressurized tank, there is no need for a pressure reducer, since the pressurized tank is adapted to feed the liquid beverage supply line with water having a constant pressure value, for example of 2 to 3 bar, as in the aforementioned embodiment including the pressure reducer fluidly connected to the municipal water supply mains.
Expediently, but not necessarily, a cooling unit 10 is provided to cool down the liquid beverage to be carbonated or the carbonated beverage to be dispended.
Preferably, the cooling unit 10 is fluidly connected to the water source 3 via the liquid beverage supply line 2 and it is provided upstream the carbonation inlet port 7 in order to decrease the temperature of the liquid beverage in order to enhance the amount of carbon dioxide that can be dissolved in the liquid beverage. As is known, lower temperature enhance the ability of water to absorb carbon dioxide.
The cooling unit 10 can be a compression cooling system operating in a known manner, namely with compressor, evaporator, and condenser, Alternatively a Peltier cooling system or other known cooling system can be used.
Further, the liquid beverage supply line 2 can comprise at least one filter device for filtering the liquid beverage to be delivered to the carbonation inlet port 7.
Preferably, a non-return valve 11 in provided in the liquid beverage supply line 2 just upstream the carbonation inlet port 7, where the carbon dioxide is introduced into the liquid beverage, in order to prevent liquid beverage flowing back towards the cooling unit 10,
The carbon dioxide supply line 4 extends from the pressurized CO₂ source 5 to the carbonation inlet port 7 and it comprises a CO₂ pressure reducer 12 for reducing the pressure of the gas flowing through the carbon dioxide supply line 4 below an upper limit, for example 7 bar in order to ensure safety working conditions of the beverage dispenser according to the present invention.
The carbon dioxide supply line 4 comprises an electro-valve 13 arranged downstream the CO₂ pressure reducer 12 and adapted to fluidly connects, selectively, the CO₂ pressurized source 5 to the carbonation inlet port 7 in order to produce carbonated liquid beverage when it is required. Advantageously, the electro-valve 13 is adapted to control and adjust the amount of CO₂ to be supplied to the carbonation inlet port 7 so that the CO₂ content of the liquid beverage to be dispensed can be varied according to the desired level selected by the user.
Preferably, a non-return valve 14 is provided in the carbon dioxide supply line 4 between the electro-valve 13 and the carbonation inlet port 7 for preventing CO₂ flowing back to the electro-valve 13.
In the embodiments being described here to mere exemplary purposes, the water working pressure, downstream the water pressure reducer 9, has a value of 1.5 to 3 bar depending on the intake pressure available from of the urban water supply mains, which in some country can be particularly low, around 2 bar.
In this connection, the pressurized tank simply ensures that slightly pressurized water at 1.5 to 3 bar, as in the case the liquid beverage supply line 4 is directly connected to the water supply mains, is delivered to the liquid/mixing point wherein carbonation takes place. In fact, for the carbonation to be carried out with better results (high carbonation level), a water pressure value slightly higher than the atmospheric pressure value would be preferable.
As regards the carbon dioxide side, in the embodiment being described here to mere exemplary purposes, the working pressure value of the CO₂ gas can vary in a range of 2 to 7 bar.
The refrigerator according to the present invention includes at least one liquid/gas mixing section 15 wherein the carbon dioxide is mixed with the liquid beverage. In particular, the carbon dioxide supply line 4 comprises a carbonation inlet port 7 which is adapted to supply the CO₂ flow to the liquid/gas mixing section 15 for the carbonation to be carried out.
In a first configuration of the present invention (see figures 1 and 3) the liquid/gas mixing section 15 comprises a junction point where the carbon dioxide supply line 4 fluidly intercepts or joints into the liquid beverage supply line 2 via the carbonation inlet port 7 in order to enable the CO₂ to be introduced into the liquid beverage supply line 2 and thereby to be mixed with the liquid beverage.
Further, the liquid/gas mixing section 15 comprises a mixing device 6 to be fed with the liquid/gas mixture emerging from the junction point in order to complete the absorption of CO₂ and then increases the final carbonation level.
In practise, the junction point acts as a three-way connector where the carbon dioxide flow and the liquid beverage flow joint into and the resulting mixing flow is delivered to the mixing device 6.
In a second configuration of the present invention (see figures 2 and 4) the liquid/gas mixing section 15 comprises a mixing device 6 fluidly connected to the liquid beverage supply line 2 via a suitable connection fitting and to the carbon dioxide supply line 4 via the carbonation inlet port 7, which is adapted to introduce carbon dioxide directly into the mixing device 6.
The flow cross-section of the carbonation inlet port 7 has a diameter dimension chosen, after exhaustive test runs, so that fluid frictional resistance is generated (when the CO₂ flows) which is adapted to reduce the velocity of the carbon dioxide flow passing through the carbonation inlet port 7 and entering into the liquid beverage supply line 2 or into the mixing device 7.
In practise, the fluid frictional force tends to lower the speed of the CO₂ flow to a reduced predetermined value, which is a value substantially constant, quite independently of the pressure value of the carbon dioxide passing through the carbonation inlet port 7.
In addition, increasing the length (i.e. the longitudinal extension perpendicular to the inlet port cross-section) of the reduced carbonation inlet port 7 will further decrease the amount of gas allowed to pass at each moment
Therefore, the carbon dioxide working pressure value can vary widely during the operation of the beverage dispenser without affecting the velocity of the CO₂ flow entering into the liquid beverage supply line 2 or into the mixing device 6.
The reduced velocity of the CO₂ flow enables the gas to effectively mix with the liquid beverage so as to maximize the carbon dioxide absorption inside the mixing device.
In this way it is possible to achieve a high carbonation level in spite of carbon dioxide working pressure value does not remain constant during the usage or operation of the beverage dispenser or even if it varies in a wide, broad range and further even if the carbon dioxide working pressure has not been set correctly during the installation of the refrigerator according to the present invention or due to component variation or change.
In other words, there is no need to accurately control or adjust the CO₂ working pressure upon installation or during usage of the refrigerator.
It has been found that fluid frictional resistance adapted to lower the velocity of the carbon dioxide flow is generated by using a carbonation inlet port having a flow cross-section diameter comprised between .
0.3 and 0.5 mm.
For both the aforementioned configurations, the carbon dioxide supply line 4 is comprised of a conduit having an internal diameter less than 20 mm and a preferred diameter range of 6 to 8 mm. It can however be most readily appreciated that the above diameter dimensions of the carbon dioxide supply line 4 upstream the carbon inlet port 7 serves only to optimize and maximize the fluid frictional resistance effect determined by the restriction of the carbonation inlet port 7.
It is well known that according to the Bernoulli theorem of compressible fluids that the decreasing of the internal diameter of a port causes the increasing of the velocity of the fluid flowing through it.
However, it has been experienced that below a certain diameter dimension, the frictional resistance generated by the internal wall surfaces of the port are so high as to reduce the velocity of the flow and, as described above, such a velocity is substantially constant despite of pressure of the fluid (at least for a given range of pressure). This is called choked flow.
Clearly there is a lower limit of the diameter dimension below which the fluid is prevented to pass through the port at all, only an extremely high working pressure would force the fluid to flow.
As regards the first configuration of the present invention, wherein the carbon dioxide supply line 4 fluidly intercepts or joints into the liquid beverage supply line 2 via the carbonation inlet port 7 and the mixing device is fed with the liquid/gas mixture emerging from the junction point, a series of tests has been performed leading to the graph shown in fig. 5 where the Y-axis depicts the CO₂ concentration of the dispensed liquid beverage in gram per liter and X-axis depicts the CO₂ working pressure value in bar (the experimental points of the graph are obtained for a working water pressure of 2 bar).
It is clear that with a conventional carbonation inlet port (2-6 mm) effective carbonation (in order to produce complete sparkling beverage) can be achieved only if the CO₂ working pressure value is around 1.7-2 bar, outside such a range the CO₂ concentration rapidly drops below 5 g/l.
On the other hand, by utilizing a carbonation inlet port having an internal diameter of around 0.4 mm, the CO₂ concentration remains above 5 g/l for a CO₂ working pressure of 2 to 3.7 bar and above 5,5 g/l for a CO₂ working pressure of 2,3 to 3.2 bar
Further by utilizing a carbonation inlet port having an internal diameter of around 0,3 mm, the CO₂ concentration remains above 5 g/l for a CO₂ working pressure of 3 to 6 bar.
It can be fully appreciated that the present invention enables the CO₂ working pressure to vary within a broad range without adversely affecting the final CO₂ concentration of the dispensed beverage and hence, no adjustment of the CO₂ working pressure value is required.
In addition, according to a preferred embodiment of the present invention the carbon dioxide supply line 4 and the liquid beverage supply line 2 are reciprocally arranged so that the gas flow, entering into the liquid beverage supply line 2 through the carbonation inlet port 7, has at least a vectorial component of the velocity vector oriented in the opposite direction of the liquid flow in order to enhance the turbulence and thereby the liquid/gas contact surface.
In particular, at the carbonation inlet port 7 the carbon dioxide supply line 4 and the liquid beverage supply line 2 form an angle V of 90° to 180° and preferably of about 135°.
The liquid/gas mixture emerging upstream from the carbonation inlet port 7 is then supplied to the mixing device 6 via a suitable fitting 15.
A carbonated beverage supply line 17 fluidly connects the mixing device 6 to the dispenser point 8.
The dispenser point 8 includes an outlet valve 18 for dispensing the carbonated beverage. Operation of the outlet valve 18 causes the simultaneous opening of the electro-valve 13.
Optionally, a compensator can be provided in correspondence to the dispenser point 8 so that the carbonated beverage can be issued with a pleasant jet.
As regards the second configuration of the present invention, wherein the carbon dioxide supply line 4 is fluidly connected directly to the mixing device 6 through the carbonation inlet port 7, which is adapted to introduce carbon dioxide directly into the mixing device, a series of tests has been performed leading to the graph shown in fig. 6 where the Y-axis depicts the CO₂ concentration of the dispensed beverage in gram per liter and further the flow rate of the dispensed liquid in liter per minute, the X-axis depicts the CO₂ working pressure value in bar (the experimental points of the graph are obtained for a working water pressure of 2 bar).
By utilizing a conventional carbonation inlet port (2-6 mm) the CO₂ concentration remains above 5.5 g/l for a CO₂ working pressure of 3.7 to 4.7 bar. However, as it is shown in the lower portion of the graph, the flow rate of the dispensed liquid rapidly decreases when the CO₂ working pressure exceeds 4 bar and above 4.7 bar the flow rate is extremely low.
By utilizing a carbonation inlet port having an internal diameter of around 0.4 mm, the CO₂ concentration remains above 5.5 g/l for a CO₂ working pressure of 4.2 to 7, whereas the flow rate starts to slightly decrease when the CO₂ working pressure is above 5.5 and up to 7 bar CO₂ working pressure the flow rate is still sufficiently high for the refrigerator to operate in an effective manner.
It can be fully appreciated again that the present invention enables the CO₂ working pressure to vary within a broad range without adversely affecting the final CO₂ concentration of the dispensed beverage and hence, no adjustment of the CO₂ working pressure value is required.
The mixing device 6 can comprise any turbulating structures adapted to produce the largest possible CO₂/liquid contact surface in order to facilitate the absorption of CO2.
In case of the first configuration according to the present invention, the turbulating structures are adapted to mix the flow of carbonated liquid beverage and free CO2 to enhance further combination thereof.
In a preferred embodiment, the mixing device 6 comprises a rotor having a plurality of blades and adapted to rotate inside a chamber.
According to the first or to the second configuration of the present invention, the liquid /gas mixture or the flat liquid beverage flow entering into the chamber causes the rotor to be driven into rotation in order to carry out carbonation.
In a further preferred embodiment, the mixing device comprises a positive displacement pump and in particular a diaphragm pump or a gear pump which has been found to be adapted to effectively carry out the carbonation process.
It can be easily appreciated that in case of the last described embodiment, operation of the outlet valve 17 causes the simultaneous opening of the electro-valve 13 and operating of the positive displacement pump.
It has to be stressed that according to the present invention, the liquid beverage working pressure downstream the water pressure reducer 9 can also be higher than 3 bar, in some countries, in fact, the intake pressure available from the municipal water supply mains is around 4-5 bar and also near 6 bar.
The extreme values of the CO2 working pressure range are determined by the fact that below 2 bar, extremely low or no liquid/gas mixing at all occurs, whereas above 7 bar the liquid beverage is prevented to reach the liquid/gas section 15 and thereby the carbonation inlet port 7.
According to the present invention, the water working pressure value can be higher or lower than the CO2 working pressure value in correspondence to the carbonation inlet port 7 depending on the nozzle dimensions, the hydraulic characteristic of the fluid circuit and of the in-line carbonator.
Optionally, the beverage dispenser of the refrigerator according to the present invention can be in the form of a post-mix dispenser adapted to mix syrup or concentrate to the flat or carbonated water to produce beverage of different flavour wherein the mixing is carried out at the time of dispensing. For this purpose, the beverage dispenser comprises a plurality of reservoirs containing syrups or concentrates to be mixed with water. The concentrate reservoirs can be fluidly connected to the liquid beverage supply line 2 or to the carbonated beverage supply line 17 in order to introduce the concentrate into the flat water, i.e. upstream the liquid/gas section 15, or into the carbonated water, i.e. downstream the liquid/gas section 15.
The refrigerator according to the present invention provides a carbonation system utilizing few, simple and low cost components, which do not need particular requirements about adjustment, operation and maintenance.
Conclusively, it can therefore be stated that the carbonation system provided in the refrigerator according to the present invention is fully effective in solving the drawbacks connected with prior-art systems in a simple manner.

Claims

A refrigerator comprising a beverage dispenser, the beverage dispenser comprising:
a liquid beverage supply line (2) fluidly connected to a water source (3) and including a pressure reducer (9) configured to render the water pressure constant,

a gas supply line (4) fluidly connected to a pressurized carbon dioxide source (5),

at least one mixing device (6) for mixing the gas with the liquid beverage,

an inlet port (7) fluidly connecting the gas supply line (4) to the liquid beverage supply line (2) or to the mixing device (6) for introducing the gas into the liquid beverage, and

a dispenser point (8) for dispensing the liquid beverage mixed with gas,

characterized in that said inlet port (7) has a flow cross-section diameter comprised between 0,3 and 0,5 mm, so that fluid resistance is generated for reducing the velocity of the gas flow entering into the liquid beverage supply line (2) or into the mixing device (6) to a predetermined value.
A refrigerator according to claim 1, wherein said mixing device (6) is adapted to be fed with the liquid/gas mixture emerging from a junction point where the gas supply line (4) joints into or fluidly intercepts the liquid beverage supply line (2) via the inlet port 7.
A refrigerator according to claim 2, wherein the gas supply line (4) and the liquid beverage supply line (2) are reciprocally arranged so that the gas flow, entering into the liquid beverage supply line (2) through the inlet port (7), has at least a vectorial component of the velocity vector oriented in the opposite direction of the liquid beverage flow in order to enhance the turbulence and thereby the liquid/gas contact surface,
A refrigerator according to claim 3, wherein at the inlet port (7) the gas supply line (4) and the liquid beverage supply line (2) form an angle V of 90° to 180° and preferably of about 135°.
A refrigerator according to claim 1, wherein said mixing device (6) is fluidly connected to the liquid beverage supply line (2) via a liquid beverage connection and to the gas supply line (4) via the inlet port (7).
A refrigerator according to any of the preceding claims, wherein said mixing device (6) comprises a rotor having a plurality of blades.
A refrigerator according to any of the preceding claims, wherein said mixing device (6) comprises a positive displacement pump and in particular a diaphragm pump or a gear pump.
A refrigerator according to any of the preceding claims, wherein said liquid beverage supply line (2) is connected to the municipal water supply mains or alternatively the water source (3) is a pressurized tank.
A refrigerator according to any of the preceding claims, wherein the gas supply line (4) comprises an electro-valve (13) adapted to fluidly connect, selectively, the gas pressurized source (5) to the inlet port (7), to control and adjust the amount of gas to be supplied to the inlet port (7).
A refrigerator according to any of the preceding claims, comprising a post-mix dispenser to introduce syrup or concentrate into the flat water upstream the mixing device (6), or into the water mixed with gas downstream the mixing device (6).
A refrigerator according to any of the preceding claims, wherein a cooling unit (10) is provided to cool down the liquid beverage in which the gas is to be introduced or the liquid beverage mixed with gas to be dispended,
A method for dispensing a refrigerated beverage, comprising:
- supplying a liquid beverage from a water source with a constant pressure,

- supplying a gas from a pressurized gas source, wherein the gas is carbon dioxide,

- mixing the gas with the liquid beverage,

- reducing the gas flow cross-section before the gas is mixed with the liquid beverage by passing the gas flow through an inlet port having a flow cross-section diameter comprised between 0,3 and 0,5 mm, so that fluid resistance is generated for reducing the velocity of the gas flow to a predetermined value
and

- dispensing the liquid beverage mixed with gas.
A method according to claim 12, wherein the working pressure value of the liquid beverage into which the gas is to be introduced is of 1.5 to 7 bar.
A method according to claim 12, wherein the working pressure value of the gas to be supplied to the inlet port is of 2 to 7 bar.