GB2376737A

GB2376737A - A beverage cooling device

Info

Publication number: GB2376737A
Application number: GB0115325A
Authority: GB
Inventors: Peter Michael Julian Henry; Thomas Charles Brannam Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-06-22
Filing date: 2001-06-22
Publication date: 2002-12-24
Also published as: GB0115325D0

Abstract

A beverage cooling device (1) comprises a thermally insulated reservoir (8) for a cryogenic substance (12), an inlet (4) to the device by which a beverage (25) may enter the device, an outlet (6) from the device by which said beverage may leave the device (1). The device includes a cooling region (18) where the flowing beverage (25) is brought into cooling contact with the cryogenic substance (12). The cooling region (18) has a thermal barrier (20) between the cryogenic substance (12) and the beverage (25). The thermal barrier (20) has a thermal conductivity of less than about 10 Wm<SP>-1</SP>K<SP>-1</SP> in the temperature range of around -198{C to 0{C. The thermal barrier may be formed of polyethylene. The cryogenic substance may be liquid nitrogen or solid carbon dioxide. If the beverage remains stationary within the cooling region (18) for too long, two shut-off valves (44,24) are closed and two bleed valves (28,38) opened. The beverage can then drain through pipe (30) and a sterile gas can enter via vent pipe (40).

Description

Beverage Cooling Device The present invention relates to a beverage cooling device capable of cooling a beverage supply to a given temperature prior to dispensing said beverage. The invention is especially intended for use in a mobile kitchen.

When providing a commercial food service it is desirable to be able to provide customers with cold beverages. In a fixed location, such as a restaurant or café, an electric vapour compression cooler powered by mains electricity is used to supply cold beverage at the required rate.

In a mobile food service a mains powered cooler may be used, but it must be compact due to the limited space available within the mobile kitchen. If no mains power is available, a passive cooler unit containing an ice pack may be used.

Before an ice pack cooling unit can be operated, the ice pack must be frozen. Once the ice pack is frozen, the unit may be taken to the desired location and used to supply cold beverages. The ice pack can take several days to freeze completely and may only provide a single day's use in a hot climate or during periods of high demand. This means that several ice packs must be used in rotation if several days of use are required from such a unit.

It is an object of the present invention to provide a more convenient beverage cooling device.

According to the present invention there is provided a beverage cooling device, comprising a thermally insulated reservoir for a cryogenic substance, an inlet to the device by which a beverage may enter the device, an outlet from the device by which said beverage may leave the device, the inlet and outlet being connected by a conduit so that a beverage may flow from the inlet to the outlet through the conduit, wherein the conduit includes a cooling region where the flowing beverage is brought into cooling contact with the cryogenic substance, said cooling region including a thermal barrier between the cryogenic substance and the beverage, the thermal barrier having a thermal conductivity of less than about 10 Wm-K-l in the temperature range of around-198 to 0 C.

Also according to the invention there is provided a method of cooling a beverage using a beverage cooling device, said device comprising a thermally insulated reservoir for a cryogenic substance, an inlet to the device by which a beverage may enter the device, an outlet from the device by which said beverage may leave the device, the inlet and outlet being connected by a conduit so that a beverage may flow from the inlet to the outlet through the conduit, wherein the conduit includes a cooling region where the flowing beverage is brought into cooling contact with the cryogenic substance, said cooling region including a

thermal barrier between the cryogenic substance and the beverage, the thermal barrier having a thermal conductivity of less than about 10 Wm-'K-'in the temperature range of around-198 to 0 C, the method comprising the steps of: i) filling the insulated reservoir with a cryogenic substance; and ii) causing a beverage to flow through the device.

The term"cryogenic substance"is used herein to describe a substance that undergoes a phase change to a gas at a temperature of less than about -500C and includes, particularly, liquid Nitrogen and solid Carbon Dioxide ("Dry Ice").

The use of cryogenic substances in a beverage cooling device provides a very large temperature gradient between the beverage to be cooled, usually entering at an ambient or room temperature and the cryogenic substance. As the cryogenic substance gains thermal energy from the beverage a phase change occurs. This provides the advantage that the temperature of the cold side of the cooling region remains constant at the phase change temperature. The latent energy for the phase change is gained by cooling the beverage. Since the latent energy required for a phase change is large, and the temperature of the cryogenic substance is low, a given volume of water can be cooled

quickly. For example, it is estimated that 31.8 litres (0. 0318 m3) of liquid Nitrogen could cool 133 litres (0.133 m3) of water from 200C to 1 C in an hour, if the cold exhaust gases are used to pre-cool the water.

The large thermal gradient across the thermal barrier means that energy loss from the beverage occurs at a high rate. If the thermal barrier were made of a standard material for heat exchanger pipes, such as copper or stainless steel with a thickness of less than a millimetre, the energy loss from the beverage would be so great that the beverage would freeze rapidly on contact with the cooling region. The use of a material that has a low thermal conductivity (less than about 10 Wm-1K-1) in the temperature range in question means that the rate of energy loss is slower and rapid freezing of the beverage is avoided.

Preferably the cooling device comprises means to remove substantially all of the beverage and/or substantially all of the cryogenic substance from the cooling region and allow a gas to enter in its place when use of the device is paused or ceases. If the beverage were to remain static within the cooling region for too long, it would be expected that the beverage would freeze within the cooling region. By removing the beverage or cryogenic substance from the cooling region during periods when it is expected that the beverage would remain static, the problem of beverage freezing can be greatly reduced.

Preferably the cooling device has the cooling region of the conduit located within the insulated reservoir, the cooling region of the conduit having an inlet and an outlet passing through the walls of the insulated reservoir. This helps reduce or eliminate the need to transport the cryogenic substance within the cooling device and hence reduces the manufacturing complexity.

The cooling region of the conduit may be in the form of a tube for ease of manufacture. The cooling region may be located in the lower half of the insulated reservoir when the device is orientated for use. This provides the advantage that as the phase change occurs in the cryogenic substance the gas will rise to the top of the reservoir and the level of cryogenic substance in the reservoir will fall. Heat transfer between a solid and a gas does not occur quickly, so once the cooling region of the conduit is above the level of the cryogenic substance, the efficiency of the device will be reduced.

Preferably the cooling region of the conduit is inclined

4 S at an angle to the horizontal when the device is orientated for use. This reduces the possibility of an air bubble becoming trapped within the cooling region and reducing the efficiency of the device.

Preferably the conduit includes two or more shut-off valves and two or more bleed valves. A pair of shut-off

valves are located upstream and downstream of the cooling region which, when shut ! prevent any beverage from entering or leaving the cooling region via the conduit. A pair of bleed valves may be located between each one of said shut-off valves and the cooling region such that when the shut-off valves are shut, and the bleed valves are opened, a gas is admitted into the cooling region and beverage is drained from the cooling region. This is a simple way in which beverage can be removed from the cooling region using gravity as the driving force. This reduces the complexity of the device and helps to reduce costs.

Additionally the thermal barrier in the cooling region could include a heater on the beverage side. This could be activated when the beverage has been removed in order to melt any frozen beverage that has formed on the walls of the cooling region. This arrangement would help to reduce the thickness of frozen beverage built up without warming the beverage, or the need to remove the cryogenic substance from the cooling region.

To prevent beverage from regularly remaining static within the cooling region a reservoir of beverage could be included with the device, either internally, or externally from which a supply of beverage is drawn into the cooling region, cooled and returned to the reservoir. Cold beverage could be drawn from a point between the beverage being cooled and the beverage being returned to the

reservoir. This arrangement would have the benefit of a rapid supply of cold beverage, but the almost continuous flow of beverage through the cooling region will result in less ice build up. This will help to reduce the frequency with which beverage is held static within the cooling region.

During operation of some embodiments of the device, frozen beverage may be permitted to form within the cooling region and form part of the thermal barrier. Simulation or trials can be used to assess how much frozen beverage will form and this can be accounted for in calculations. This reduces the need to counteract the freezing of the beverage and hence reduces manufacturing complexity.

As mentioned above, during operation of the cooling device, it is possible that the beverage may freeze. In some embodiments this can cause problems. For example, if the beverage is passing through a narrow tube, any frozen beverage will constrict the tube and restrict flow. In other embodiments, the freezing of the beverage may not cause a flow restriction, and the cooling region can be designed so as to permit a certain amount of beverage freezing. This frozen beverage will act as an additional thermal barrier between the cryogenic substance and the beverage.

At least part of the thermal barrier can be made of polyethylene, a polymer having the required low thermal

conductivity. Food grade polyethylene is already used as a polymer plastic in certain food preparation processes and so is safe to use with a beverage. This material is also stable at the operating temperatures of the device.

The beverage exit temperature can be controlled by adjusting the flowrate of beverage through the cooling region in response to information from a temperature sensor in the beverage outlet. If the beverage is too warm, the flow rate is reduced giving the beverage more time in the cooling region. Any method that adjusts the time the beverage spends in the cooling region could be used to control the outlet temperature, for instance, mechanically adjusting the length of the cooling region by withdrawing some of it from the cryogenic substance.

As the beverage is cooled, the cryogenic substance undergoes a phase change to gas. This gas could be vented from the insulated reservoir through a heat exchanger located upstream of the cooling region in the conduit. This heat exchanger may be co-current, counter current, a combination of the two or a direct contact device that bubbles the vented gas through the liquid stream and will provide pre-cooling of the beverage. This means that the cryogenic substance is being used in a more efficient manner and will enable the volume of cryogenic substance needed to cool a given volume of water by a given amount to be reduced.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic diagram of a cooling device according to the invention having a cooling region surrounded by a cryogenic substance ; Figure 2 shows a side view of one embodiment of the cooling region of the cooling device of Figure 1, the cooling region being within an insulated reservoir; Figure 3 shows a plan view of the preferred embodiment of Figure 2 ; Figure 4 shows a second embodiment of the cooling region having a beverage passing through coils containing the cryogenic substance; Figure 5 shows a further embodiment of the cooling region where the cooling region forms a cold finger upon which ice is permitted to form; and Figure 6 shows a different embodiment of the cooling device of Figure 1, the insulating reservoir including a vent line and the conduit including a pre-cooling heat exchanger.

Figure 1 shows a schematic drawing of a cooling device 1.

The cooling device 1 has an outer case 2, through which an inlet pipe 4 and an outlet pipe 6 pass.

Within the case 2 there is a reservoir 8. The reservoir 8 is insulated by a reservoir wall 10. The insulating wall 10 may consist of vacuum insulation, as in the case of a vacuum dewar, or a solid insulation such as fibreglass with an aluminium jacket. A cryogenic substance 12 is contained within the reservoir 8.

During operation of the cooling device 2 a beverage (not shown) is drawn through the inlet pipe 4 by a pump 14 located within the case 2. The pump 14 causes the beverage to flow through a conduit 16 that extends from the inlet pipe 4 to the outlet pipe 6. The conduit 16 passes from the pump 14 and through a shut-off valve 24, which is open when the device 1 is used to cool a beverage 25 flowing through the conduit 16. Upstream of the shut-off valve there is a T-junction 26, one branch 27 of which leads through a bleed valve 28 which is closed when the device is used to cool the beverage 25, to a drain pipe 30.

The other branch 32 of the T-junction 26 passes through the insulating wall 10 of the reservoir 8 and into a cooling region 18 in the lower portion of the reservoir 8 within which the beverage 25 is in cooling contact with the cryogenic substance 12. In the cooling region 18, a thermal barrier 20 separates the cryogenic fluid 12 and the beverage. The thermal barrier has a low thermal

conductivity ( < 10 Wm-1K-1), and in this example is made of Polyethylene.

As the beverage is cooled within the cooling region 18, the cryogenic substance undergoes a phase change to form a gas 52, which rises to the top of the reservoir 8. It is for this reason that the cooling region is low down in the reservoir 8.

After cooling within the cooling region 18, the beverage enters a pipe 22, which passes through the insulating wall 10 and enters a second T-junction 34. One branch of this T-junction 36 passes through a bleed valve 38 and to a vent pipe 40.

The other branch 42 of the T-junction 34 passes through a shut-off valve 44, which is usually open and into the outlet pipe 6.

If the beverage remains stationary within the cooling region 18 for too long, it is expected to freeze. To prevent this, when it is expected that the beverage will be stationary for a long time ( > 5 minutes), the two shutoff valves 44,24 are closed and the two bleed valves 28,38 opened. This allows beverage to drain through the drain pipe 30, while a gas enters the cooling region 18 through the vent pipe 40. Since this device 1 is for cooling a beverage 25, the gas entering the cooling region must be sterile. The gas could be filtered air, or an inert gas

like Nitrogen.

The speed of the pump 14 is controlled by a signal 45 from a control unit 46. The control unit 46 alters the control signal 45 in response to a signal 48 from a temperature sensor 50 in the conduit 22 at the exit from the cooling region 18. The signal 48 is indicative of the temperature of the beverage 25 in the region of the sensor 50.

Controlling the speed of the pump 14 in response to the beverage temperature allows simple feedback control of the beverage outlet temperature.

In subsequent figures, the above reference numerals will be retained for features common to embodiments shown, in the case where a feature differs from that shown in Figure 1, the reference numeral will be incremented by 200.

Figure 2 shows a side view of an embodiment of the cooling region 18. In this case the cooling region 18 takes the form of a loop of pipe 100 joining the inlet and outlet conduits 22 and 32. The walls 102 of the pipe 100 form the thermal barrier 20 of Figure 1. It can be seen that in this embodiment the inlet 32 and the outlet 22 are displaced vertically in the wall 10 of the reservoir 8. This is so at least part of the cooling region 18 is at an angle to the horizontal.

Figure 3 shows a plan view of the cooling region 18 embodiment shown in Figure 2. It can be seen that that in

this embodiment the inlet 32 and the outlet 22 are also displaced horizontally in the wall 10 of the reservoir 8.

This is so the cooling region 18 has a greater surface area than if the inlet 32 and outlet 22 had been vertically aligned. By way of example, it is estimated that for a cooling region made of a polyethylene tube with an outer diameter of 20 mm and a wall thickness of 4 mm, the length of the cooling region would have to be 1.067 m to cool 133 litres (0.133 m3) of water per hour from 30 C to 5 C.

Figure 4 shows a cross section of another embodiment of the cooling region of Figure 1. In this case the cooling region 218 is outside the reservoir 8.

In this embodiment, beverage enters through the inlet conduit 232 and passes through an enlarged pipe region 104 and exits via an outlet conduit 222.

Within the enlarged pipe region 104 there are hollow coils 106 with walls 107, having an inlet 108, and an outlet 110. A pump or gravity feed from a storage dewar (not shown) is used to force the cryogenic substance 12, in this case a liquid, through conduits (not shown) from the reservoir 8, through the coils 106 and back into the reservoir 8. The walls 107 form the thermal barrier 20 of Figure 1.

Figure 5 shows another embodiment of the cooling region

618. In this case the beverage enters the cooling region 618 through the inlet conduit 232, passes through a substantially cone shaped region 112, with the inlet 232 in a narrow end 114 of the cone shaped region 112, aligned substantially along an axis 118 of the cone 112. The beverage exits the cooling region through the outlet 222, which is located in a side wall 120 of a wide end 116 of the cone shaped region 112 and is aligned substantially perpendicular to the axis 118.

The cryogenic substance 12, in this case a liquid, is pumped, or gravity fed through an inlet 128 into a cold finger 122 having a wall 124. The cold finger 122 orientated along the axis 118 and attached to an end plate 126 at the wide end 116 of the cone 112. The cryogenic liquid 12 and/or gas leaves the cold finger through an outlet 130. Both the inlet 128 and the outlet 130 pass through the end plate 126. During operation of the cooling device 1, beverage is allowed to freeze on the wall 124 of the cold finger 122. This frozen beverage forms a frozen beverage pack 132 that does not completely fill the interior of the cone 112. The frozen pack 132 and the cold finger wall 124 in combination form the thermal barrier 20 of Figure 1.

Figure 6 shows a different embodiment of the cooling device of Figure 1. In this embodiment 201 a heat exchanger 150 is located in the in the branch 32 of Tjunction 26.

A vent pipe 152 links the gas 52 in the insulated reservoir 8 with the heat exchanger 150. As the cryogenic substance 12 undergoes the phase change to gas, gas 52 is forced through the vent pipe 152 and through the heat exchanger 150. The gas then exits the heat exchanger 150 through an exit pipe 154 into the atmosphere.

Beverage flows through the heat exchanger 150 prior to entering the cooling region 18. As beverage flows through the heat exchanger 150 it is in thermal contact with the gas 52.

The gas 52 is at a temperature substantially the same as the temperature at which the phase change occurs in the cryogenic substance 12. This means that as the beverage passes through the heat exchanger 150 it is cooled by thermal contact with the gas 52.

The device has been described as a stand-alone cooling device, but it should be understood that the device could form a part of a larger beverage machine. Particularly, the device could form the cold water supply for a post mix drink system in which water is cooled to the desired temperature and then mixed with a concentrate to create a flavoured beverage.

Claims

Claims 1. A beverage cooling device, comprising a thermally insulated reservoir for a cryogenic substance, an inlet to the device by which a beverage may enter the device, an outlet from the device by which said beverage may leave the device, the inlet and outlet being connected by a conduit so that a beverage may flow from the inlet to the outlet through the conduit, wherein the conduit includes a cooling region where the flowing beverage is brought into cooling contact with the cryogenic substance, said cooling region including a thermal barrier between the cryogenic substance and the beverage, the thermal barrier having a

thermal conductivity of less than about 10 Wm-1K-1 in the temperature range of around-1980 to OOC.
2. A cooling device as claimed in claim 1, in which the device further comprises means to remove substantially all of the beverage from the cooling region and allow a gas to enter to replace the beverage being removed, when the device is not being used to cool the beverage.
3. A cooling device as claimed in claim 1, in which the device further comprises means to remove substantially all of the cryogenic substance from the cooling region and allow a gas to enter to replace the cryogenic substance being removed, when the device is not being used to cool the beverage.

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4. A cooling device as claimed in any claim 1, in which the cooling region of the conduit is located within the insulated reservoir, the cooling region of the conduit having a separate inlet and outlet passing through the walls of the insulated reservoir.
5. A cooling device as claimed in claim 4, in which the cooling region of the conduit is in the form of a tube, the tube having inner and outer surfaces which, in use, are in contact with, respectively, the beverage and the cryogenic substance.
6. A cooling device as claimed in claim 4 or claim 5, in which the cooling region of the conduit is located in a lower portion of the insulated reservoir when the device is orientated for use.
7. A cooling device as claimed in any of claims 4,5 or 6, in which at least part of the cooling region of the conduit is inclined at an angle to the horizontal when the device is orientated for use.
8. A cooling device as claimed in claim 7, in which the conduit includes two or more shut-off valves and two or more bleed valves, including a pair of shut-off valves located upstream and downstream of the cooling region which, when shut, prevent any beverage from entering or leaving the cooling region via the conduit;

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a pair of bleed valves located between each one of said pair of shut-off valves and the cooling region such that when the shut-off valves are shut, and the bleed valves are opened, a gas is admitted into the cooling region and beverage is drained from the cooling region.
9. A cooling device as claimed in claim 2 or claim 3, in which the gas allowed to enter is boiled cryogenic substance that has undergone a phase change to a gas.
10. A cooling device as claimed in any preceding claim, in which the at least part of the thermal barrier is made of polyethylene.
11. A cooling device as claimed in any preceding claim, in which the thermal barrier includes a heating device on the beverage side, activated when the device is not in use in order to melt any frozen beverage that has formed within the cooling region.
12. A cooling device as claimed in any preceding claim, in which the device includes means by which the beverage may be made to flow from the inlet to the outlet through the conduit.
13. A cooling device as claimed in any preceding claim, in which boiled cryogenic substance is vented from the insulated reservoir through a heat exchanger in the conduit so as to pre-cool beverage before it enters the

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cooling region.
14. A method of cooling a beverage using a beverage cooling device, said device being as claimed in any preceding claim, the method comprising the steps of: i) filling the insulated reservoir with a cryogenic substance; and ii) causing a beverage to flow through the device.
15. A method as claimed in claim 14, in which the exit temperature of the beverage is controlled by altering the residence time of the beverage within the cooling region.
16. A method as claimed in claim 15, in which, during operation of the device, frozen beverage is permitted to form within the cooling region and form part of the thermal barrier.
17. A method as claimed in any of claims 14,15 or 16, in which the beverage is water.
18. A beverage cooling device substantially as herein described, with reference to or as shown in the accompanying drawings.
19. A method of cooling a beverage, using a beverage cooling device, substantially as herein described, with

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reference to the accompanying drawings.