The present invention relates to an apparatus for cooling beverages as they are served. More specifically, the present invention relates to an apparatus for use in-line with a beverage dispensing system that can cool a beverage to a desired temperature while the beverage is being dispensed at a high volumetric flow rate.
Carbonated beverages, especially soda and beer, are generally served cold. The two reasons for serving them cold are to increase the perception of refreshment to the consumer and to ease the dispensing of the beverage. Many carbonated beverages, especially beer, are stored in stainless steel containers and dispensed through a series of tubes that carry the beer to the beer dispensing faucet at the dispensing point. More specifically, beer is often stored in 15.5 gallon stainless steel kegs. When possible, the entire keg is kept at the appropriate temperature for serving. Vendors of these beverages use a variety of methods to cool the beverage before it is served. Under some circumstances, the keg is stored at a temperature above the optimal temperature for serving.
One method of cooling a beverage for consumption is to present a single serving in a container with a cold media, typically ice. Ice is a very effective way to cool beverages because of the thermodynamic properties of frozen water. In order for one gram of ice to increase one degree Centigrade, it must absorb 4.18 Joules of energy from its surroundings. Once the ice has reached its melting point, each gram of ice must absorb an additional 334 Joules of energy in order to undergo the transformation from the solid phase to the liquid phase. The same effect can be achieved by using any media that undergoes a phase change as it warms. This is a very effective way to cool a beverage as long as the liquid water generated by the ice mixing with the beverage is deemed acceptable to the consumer. However, with some carbonated beverages, such as beer, adding ice to the beer is not an acceptable method for cooling the beer, as it results in watering down the beer.
The cooling properties of water and ice are also used in two other techniques for cooling beverages: The cold plate (
When the ice is exposed to the warmer plate, it melts. The temperature of the plate near the center of the cold plate is typically higher than it is near the edges due to the higher ratio of warm liquid to surface area available for cooling. Thus, the ice in contact with the center of the plate melts faster and the resulting liquid then runs off, leaving the cold plate relatively ineffective in the central region. This phenomenon is often referred to as “bridging” by those in the beverage industry. Bridging greatly reduces the effectiveness of the cold plate.
The second known way of cooling beverages, as shown in
With previous coils, as shown in
The temperature of a carbonated beverage is closely related to the pressure under which it is stored. With carbonated beverages, the partial pressure of the dissolved carbon dioxide, the solute, varies with the temperature of the beverage, the solvent. In order to maintain the desired level of carbonation, the pressure of the applied carbon dioxide must be varied according to the temperature of the beverage.
In-line cooling devices, such as cold plates and cold coils, are typically used in situations where the beverage is not stored at ideal serving temperatures. In order to keep the dissolved gas in solution, higher than normal pressures must be applied. To counter-act these pressures, known in-line cooling devices use a long length of tubing having a small internal diameter, which result in a very large head loss as the beverage flows. This head loss is large enough such that equilibrium between the high keg (storage container) pressure and atmospheric pressure is reached at a low flow rate, often less than 1 gal/minute (4.2 liters/minute). In high volume concession environments, the low flow rate is very inconvenient and inefficient, causing long wait lines for beverages and potential loss or reduction in sales.
Thus, there is a need for a more effective system of cooling beverages in in-line dispensing systems without sacrificing flow rate.
The present invention relates to an apparatus for cooling beverages as they are served. More specifically, the present invention relates to an apparatus that is installed in-line with a beverage dispensing system that can effectively cool the beverage to a desired temperature while the beverage is being dispensed at a high volumetric flow rate. The apparatus may include a beverage conduit encased within a thermally conductive body, and a cooling medium. In operation, substantially all of the surface area of the conduit is in contact with the thermally conductive body and substantially the entire surface of the thermally conductive body is in contact with the cooling medium. The apparatus may cool at beverage traveling through conduit from a temperature of about 70° F. to a temperature of about 38° F., with a steady-state throughput of beverage through the conduit of about 1.0 gallons or greater of beverage per minute.
An in-line beverage dispensing system 10, for dispensing a carbonated beverage such as beer, is shown in
As shown in
As shown in
A helical coil conduit 32 may be constructed by winding a straight section of stainless steel tubing around a drum. Stainless steel tubing is one material that may be used when working with beverages, especially beer, due to its non-corrosive nature. However the conduit also may be made from copper, brass, silver, titanium or any other material provided the melting point of the conduit material is higher than the melting point of the material from which the thermally conductive body 34 is formed.
The conduit 32 may be wound such that there is some spacing between adjacent turns of the coil. The spacing between the revolutions of tubing may be achieved by moving the drum or moving the source of the straight tubing. In one example, the spacing between consecutive revolutions of the helix will be equal to the radius of the conduit 32 itself. The diameter of the conduit may be between about 6 mm and about 25 mm. For example, the diameter of the conduit may be between about 8 mm and about 20 mm. Further, the diameter of the conduit may be between 10 mm and about 14 mm. The tubing may be trimmed after the coil is completed in order to leave the tangential inlet and outlet tubes for use in the casting process.
The shape of the conduit 32 is not limited to a helical coil. The arrangement of the beverage conduit 32 may be serpentine, serpentine-like, or double helical as it is routed within the thermally conductive body 34. For example, as shown in
As shown in
The geometry of the thermally conductive body 34 maximizes the surface area exposed to the cooling media. For example, a toroidal shape (as shown in
Generally speaking, for a given material, the more massive the thermally conductive body 34, the greater its capacity for cooling the beverage. Portability of this invention, however, is a highly desirable characteristic that places practical constraints on the mass of the body 34. Additionally, this device desirably fits within a readily available thermally insulated container. Accordingly, the mass of the thermally conductive body 34 may be between about 5 kg and about 30 kg. In one example, the mass of the thermally conductive body 34 may be between about 10 kg and about 20 kg. Further, the mass of the thermally conductive body 34 may be between about 12 kg and about 16 kg. The height of the thermally conductive body 34 may be between about 10 cm and about 60 cm. For example, the height of the thermally conductive body 34 may be between about 20 cm and about 40 cm. Further, the height of the thermally conductive body 34 may be between about 25 cm and about 32 cm. For a toroidal configuration, the diameter of the thermally conductive body 34 may be between about 10 cm and about 60 cm. For example, the diameter of the thermally conductive body 34 may be between about 20 cm and about 40 cm. Further, the diameter of the thermally conductive body 34 may be between about 25 cm and about 32 cm.
As shown in FIGS. 9A-B and 11 (in perspective and top views, respectively), the thermally conductive body 34 may be provided with projections 40 on the outward facing surface 42 and, if present, the inward facing surface 44 of the thermally conductive body 34 to increase the surface area exposed to the cooling media. The projections may be fins, wedges, blocks, rings, or any other geometry that increases the surface area of the thermally conductive component of the apparatus.
The projections 40 may be tapered such that they are circumferentially wider near their bottom 46 and narrower near their top 48. The projections 40 may be arranged in such a way that as a piece of ice or other cooling media is reduced in size due to melting, and is drawn toward the bottom by gravity, it remains in contact with the thermally conductive body 34. This is to counter the “bridging” effect experienced with known cooling devices.
Although the apparatus has been described here as having a toroidal shape, the shape of the apparatus may be of other geometries, for example the shapes illustrated in FIGS. 12A-D. As shown, the body 34 may be constructed to have a repeating H-shape, which may be broader at its base. As shown, the longitudinal dimension or surface 60 has a greater area than the lateral dimension or surface 62. In this configuration, the conduit 32 may be configured in vertical or horizontal undulations or bends throughout the interior of the body 34.
As shown, for example in
As shown in
The maximum angle of taper is limited by the thickness of the base 46 and the target height of the thermally conductive body 34. The total angle of taper between the outer 42 and inner 44 surfaces of the thermally conductive body may be between about 0.5 and 90 degrees. For example, the total angle of taper may be between about 2 and about 45 degrees. Further, the total angle of taper may be between about 3 and about 15 degrees. For example, a tapered toroidal shape ensures that gravity will keep an inverted frustum of ice cubes in contact with the inward facing surface 44 of the body 34 at all times. The reverse is true on the outer surface 42. Gravity continually draws the melting ice downward and the body 34 itself is the frustum being wedged into the ice. As shown
Because warm beverages are poured, then stopped, then poured again, ice near the top of the device will melt the fastest upon introduction of warm beverage, where as the thermally conductive material absorbs most of the heat from the beverage as it flows through the lower portion. When the flow of beverage is stopped, the ice from around the lower portion absorbs the heat from the thermally conductive material. Ultimately, the rate of ice melting as the flow of beverage is repeatedly started and stopped is fairly uniform. This keeps the amount of ice in contact with the thermally conductive solid at a maximum.
The thermally conductive body 34 may be constructed of aluminum, copper, brass, silver or any other thermally conductive material having thermal conductivity, k, of about 50 W/m° C. or greater. For example, the material may have a k-value of about 100 W/m° C. or greater. In another example, the k-value of the material may be about 200 W/m° C. or greater.
The thermally conductive material makes any number of beverage conduits more effective at cooling the beverage than the conduit would be by itself. For example, the principal behind the existing cold plate technology is to cool a block of thermally conductive material, which in turn cools the walls of the passage which in turn cools the beverage. The heat transfer rate, or cooling, is a function of surface area. All existing cold plates are arranged such that the cooling media, in most cases, ice, is only applied to one surface of the cold plate, less than half of the available surface area. Previous beverage cooling coils included multiple layers of closely packed tubing with a smaller diameter in an attempt to maximize surface area of tubing exposed to a cooling media. However, the small diameter of the tubing restricted the flow rate of the beverage through the tubing, and the close packing of the coils limited available cooling surface area.
The beverage cooling apparatus 24 may incorporate larger diameter conduits than conventional conduits. The use of larger diameter conduit has two advantages. First, it reduces the head loss of the beverage as it flows through the tubing. This enables a higher flow rate at the same keg pressure. For a given length of conduit 32, the second advantage is that the beverage will spend a longer period of time within the device. With the higher volume and a given volumetric flow rate, the beer remains in the device longer and has more time to cool. The time that the beverage remains within the thermally conductive solid 34, the resident time, may be calculated by the formula:
where
At steady state, the warm beverage will be sufficiently cooled if it has about 7 seconds to cool within a thermally conductive body encasing the tubing. The beverage will have about a 9 second resident time or more within the thermally conductive body. For example, the beverage may have a resident time within the thermally conductive body 34 of about 11 seconds or more. For a given conduit radius, resident time, and volumetric flow rate, the length of the conduit can be determined. The length of the conduit 32 may be between about 4 and about 40 meters. For example, the length of the conduit 32 may be between about 5 and about 20 meters. Further, the length of the conduit 32 may be between about 6 and about 15 meters.
A flow rate of greater than about 1 gallon per minute at pressures ranging from about 14 psi (0.965 bar) to about 40 psi (2.76 bar) may be achieved with the beverage cooling apparatus 24 described. A flow rate of between about 1.5 and about 4 gallons per minute at pressure ranging from about 18 psi (1.25 bar) to about 28 psi (1.85 bar) further may be achieved.
In typical concession environments, two or three servings are dispensed, the faucet 14 is closed as the transaction is completed, and then the faucet 14 opens again to dispense the servings for the next transaction. The few seconds between dispenses allows multiple servings to be contained within the device during which additional cooling takes place.
The cooling apparatus 24 makes use of the basic principles of heat transfer. Heat transfer is a product of three quantities: thermal conductivity, surface area, and thermal gradient.
where
When a helical coil is used as the conduit, the adjacent turns of the coil may be space from one another, as shown in
T=−cd2
Where
When two channels of conduit 32 run very close to each other, the heat conducting from the two tubes warms the thermally conductive material around them, thereby reducing the temperature gradient. Even a small separation of the tubing 32 greatly reduces the temperature of the thermally conductive material due to the quadratic nature of the temperature distribution function. With tubing 32 close together, the temperature between the tubes increases, decreasing the dT/dx. With a smaller dT/dx, the magnitude of q goes down. In other words, there is virtually no heat transfer in the axial direction when the tubing 32 is packed closely together, as illustrated in
High flow rate at a wide range of pressures may be achieved by the beverage cooling apparatus 24. The pressure loss as fluid flows through a channel is often referred to as “head loss” in the plumbing trade and “restriction” in the beer trade. Restriction is an important part of any draft beer system, and for the most part is managed with experience, trial and error, and some rough tables. Scientists studying fluid mechanics have modeled restriction, or more generally, pressure loss with the equation
Rearranged and solved for the Q, the flow rate, the equation becomes
Where
The plot of the flow rate, Q, as it varies with the change in pressure, ΔP, is parabolic in shape. Given the temperature range at which the beverage is stored, the concentration of carbon dioxide that is dissolved in the beverage, and the desired flow rate, it is a simple calculation to use the above mathematical model to design an apparatus that will maintain a consistent flow rate over a range of pressures necessary to maintain carbon dioxide equilibrium. Regardless of the pressure necessary to maintain proper carbonation, the flow rate stays within the capacity of the dispensing device.
When the flow of beverage through the device is regularly interrupted, the thermally conductive body 34 acts as a heat sink. The mass ratio of thermally conductive material to beverage combined with the specific heat capacities of the material defines the cooling capacity of the apparatus 24. When a certain mass of warm beverage, for example beer, is cooled by a certain mass of a thermally conductive solid, for example aluminum, although any material having the desired k-value may be used, the heat gained by the aluminum is equal to the heat lost by the beer.
ΔHaluminum=−ΔHbeer
The heat gained or lost by a material is defined by
ΔH=(m)(c)(ΔT)
where
Generally speaking, for a given thermal conductivity, the more massive the thermally conductive body 34, the greater its capacity for cooling a beverage. Similarly, the longer the beverage conduit 32, the greater the amount of time the beverage will spend circulating within the device at a given flow rate, and the greater its capacity for cooling the beverage.
When in the apparatus 24 is in its operating position, substantially all of the outer surface area of the conduit 32 is in contact with the thermally conductive body 34 and substantially all of the surface of the thermally conductive body 34 is in contact with the cooling medium. The storage temperature of the beverage may be as high as 80° F. Typically, the storage temperature of a beverage is about 42° F. to 55° F. Preferably, the apparatus 24 may cool the beverage from its storage temperature to a temperature of about 45° F. or below. For example, the dispensing temperature of a beverage may be in the range of 32° F. to 45° F. In one example, such as in the United States, the brewery recommended serving temperature of a beer is about 38° F. The steady-state throughput of beverage through the conduit 32 may be about 1.0 gallons or greater of beverage per minute. For example, a flow rate of between about 1.5 and about 4 gallons per minute at pressure ranging from about 18 psi (1.25 bar) to about 28 psi (1.85 bar) further may be achieved.
It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of the invention.
Applicants claim priority to U.S. Provisional Patent Application Ser. No. 60/789,643, filed on Apr. 5, 2006, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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60789643 | Apr 2006 | US |