Note: Descriptions are shown in the official language in which they were submitted.
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"Improvements in heat exchangers for dispensing sub-zero beer"
Cross-Reference to Related Applications
The present application claims priority from Australian Provisional Patent
Application No 2008900054 filed on 4 January 2008, the content of which is
incorporated herein by reference.
Field of the Invention
This invention relates to an improved apparatus for dispensing cooled fluids,
in
particular beverages, such as beer.
Background of the Invention
In most commercial establishments where beer is served, the beer is supplied
in
barrels or kegs. The kegs are stored in a refrigerated cold room or cellar at
a
temperature range of between 3 and 10 degrees C. The beer is normally
dispensed
through beer dispensing valves/taps located away from the cold room. A heat
exchanger or some form of extra cooler is also normally included in the system
to
further cool the beer in line between the cold room and the tap.
The beer is delivered to the taps from the kegs through a conduit containing
the
beer delivery lines. The conduit also contains coolant transfer lines for
recirculation of
cold water or water containing a percentage of antifreeze components such as
glycol.
In practice, the beer is moved through the beer delivery lines by means of CO2
gas
pressure applied to the barrel or keg.
Recently, due to changes in customer preferences and fashions, it has become
desirable to serve beer at temperatures below 0 degrees C.
Existing systems using heat exchangers installed in line between the cold room
and the beer dispensing tap, have relied on an external cold source being
supplied to
circulate coolant at closely controlled temperatures through the conduit and
heat
exchanger to cool the beer to the sub zero temperature.
These systems have high maintenance costs associated with the external cold
source and a high initial installation costs involving extensive site
alterations to the beer
system.
The present invention seeks to provide a lower cost and preferably more
efficient beverage cooling system.
Any discussion of documents, acts, materials, devices, articles or the like
which
has been included in the present specification is solely for the purpose of
providing a
context for the present invention. It is not to be taken as an admission that
any or all of
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these matters form part of the prior art base or were common general knowledge
in the
field relevant to the present invention as it existed before the priority date
of each claim
of this application.
Summary of the Invention
According to a first aspect of the present invention there is provided a heat
exchanger comprising a coolant line and a beverage (typically beer) line
embedded in a
solid block of a material having a high thermal conductivity (most preferably
aluminium, although other materials having high conductivity could be used)
with the
coolant line in the form of a first coil defining a plurality of turns located
in the block
and the beer line in the form of a second coil defining a plurality of coils
extending
around the first coil.
The location of the coolant line typically in the centre of the aluminium
block
and the physical arrangement of the coolant line in the form of a coil
provides a cold
core or central cold zone in the solid block.
The resultant outer area provides a designated beverage cooling zone in which
the beer/beverage line is located.
In a second related aspect, the invention provides a heat exchanger comprising
a
coolant line and a beverage line embedded in a solid block of a material
having a high
thermal conductivity with the beverage line in the form of a first coil having
a plurality
of turns being located in the centre of the block and defining a designated
beverage
cooling zone and the coolant line in the form of a second coil defining a
plurality of
turns and extending around the first coil and defining a cold zone.
The ratio of the volumes of these two distinct zones within the solid is an
important relationship when dispensing beer at critical temperatures, often as
low as -2
degrees C. In a preferred embodiment the volume ratio of the designated zone
to the
cold zone is about 150:100.
The cold zone acts as a thermal storage of energy. This thermal storage is
used
to maintain controlled beverage outlet temperatures and avoid the fluctuations
that are
typical with existing heat exchangers.
The coil is typically in the form of a helical coil. As used herein "helical"
is not
to be taken as inferring that the coils of each turn of the helical coil need
be circular.
The coils may be any shape and will typically comprise semi-circular curved
ends
separated by straight lengths of tubing.
The coolant used is typically a Freon refrigerant, however the invention can
easily be adapted for use with recirculating glycol.
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The coolant tubes are arranged in a helical pattern through the cold zone. The
distance between the tubes is varied to control the rate of heat transfer from
the coolant
into the solid material of the cold zone. In the preferred embodiment the
distance
between adjacent tubes is between 3 and 10 mm.
The diameter of the coolant tubes used in the cold zone for transfer of cold
from
the coolant to the cold zone is selected based on the energy requirement of
the system.
Typically the range of tube diameters would be from 6 to 13 mm.
The distance between the tubes/coils in the beverage line is varied to control
the
rate of heat transfer from the designated zone into the beverage. In the
preferred
embodiment the distance between adjacent tubes is from 3 to 8 mm.
The diameter of the beverage tubes used in the designated zone for transfer of
heat from the beverage to the solid material is also selected based on the
energy
requirements of the system. Typically, the diameter may be between 7 to 11 mm.
The distance between the coolant tubes located in the cold zone and the
beverage tubes located in the designated zone affects the heat flow between
the two
defined solid areas. The preferred distance is from 2 to 6 mm.
This allows for predetermined heat transfer effects with in the solid to
facilitate
the heat transfer from the coolant to the solid and then across the solid and
into the
beverage.
The relationship between the plane of the beverage tube coils and the coolant
tube coils ("the angle between the tubes") is important in maximising the heat
transfer
rate across the solid.
Adjusting the angle controls the heat transfer rate across the solid. In a
preferred
embodiment this angle is between 80 and 110 degrees, however the angle is
adjustable
between 15 and 120 degrees.
The angle provides three dimensional heat flux within the solid areas and acts
as
a means of inducing turbulence to the heat flow through the solid areas and
maximising
the available transfer of cold through the system.
The efficiency control that is available through the present invention allows
for
cooling of beer to precise temperatures and even temperatures close to
freezing point,
using direct expanded Freon refrigeration methods.
The present invention allows for a complete system including the refrigeration
equipment to be packaged into a small area, such as is available under bars
and
dispensing counters etc., which removes the need for large installations and
the
associated costs and maintenance of the same.
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The present invention may also eliminate or ameliorate the problems associated
with freezing of subzero beverages which has limited the dispensing of low
alcohol
beverages at temperatures less that 0 degrees C using existing heat exchanger
systems.
There may be a plurality of beverage lines in the designated zone. There may
also be a plurality of coolant lines in the cold zone. The cold zone may
include more
than one coolant line, for example two coolant lines in parallel, or two
coolant lines in
series.
In one embodiment one or more additional lines may pass through the first
coil.
The additional lines may include one or more lines for cooling glycol.
Alternatively
the additional lines may include one or more lines for pre-chilling soft
drinks, soda or
the like.
The additional lines are generally located in a central zone inside the inner
cold
zone. The ratio of the central zone to the inner cold zone to the outer zone
is typically
about 150: 100: 150.
Brief Description of the Drawings
A specific embodiment of the present invention will now be described, by way
of example only, and with reference to the accompanying drawings, in which:-
Figure 1 is a schematic view of an embodiment of a solid block heat exchanger
embodying the invention;
Figure 2 is a schematic view of part of the heat exchanger illustrating the
gaps
between the tubes in the beverage lines;
Figure 3 is a schematic view of part of the heat exchanger illustrating the
gaps
between the tubes in the coolant lines;
Figure 4 is a schematic view illustrating the concepts of the inner cold zone
and
the designated zone;
Figure 5 is a schematic view illustrating a variant of the heat exchanger of
Figures 1 to 4 in which there are two parallel beverage lines;
Figure 6 is a schematic view illustrating a yet further embodiment of a heat
exchanger in which there are two coolant lines in series;
Figure 7 is a schematic view of a variant of the solid block heat exchanger of
Figures 1 to 4 in which the locations of the cold zone and cooling zones are
reversed.
Figure 8 is a schematic view illustrating a variant of the heat exchanger of
Figures 1 to 4 in which there is and additional cooling zone; and
Figure 9 is a schematic view of part of the heat exchanger of Figure 8.
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Detailed Description of a Preferred Embodiment
Referring to the drawings Figure 1 shows a solid block heat exchanger 10
comprising a first coolant line or tube (typically formed from stainless
steel) in the
form of a "helical" coil arrangement 11 having a plurality of turns/coils. As
shown the
5 coils are generally rectangular in plan view having semi-circular curved
ends separated
by straight lengths of tubing. However other coil shapes could be used.
This coil arrangement locates generally within an cold zone 12 of the heat
exchanger 10 within a rectangular box shaped volume also shown in Figure 4. In
this
embodiment, the coil 11 is an inner coil as, extending around the outside of
the coil
arrangement 11 is a second "helical" coil arrangement 13 (also typically
formed from
stainless steel tubes) which in use carries beverage, typically beer, or other
carbonated
alcoholic drink of a similar alcohol content to beer.
As shown, the coils are generally rectangular in plan view having semi-
circular
curved ends separated by straight lengths of tubing. Again, other coil shapes
could be
used.
This "outer" coil arrangement locates in a zone 14 (the designated cooling
zone)
outside of the cold zone 12 of the heat exchanger and between that cold zone
12 and the
exterior of the heat exchanger.
The heat exchanger 10 is formed by locating the coils 11 and 13 in a
rectangular
mould in the arrangement shown and pouring molten aluminium over the coils to
form
a solid block 15. Such casting techniques are well known for forming solid
block heat
exchangers and accordingly will not be described in detail herein. When cast,
the open
ends of the coils 11 and 13 form coolant inlets Ila and coolant outlets llb,
and
beverage inlets 13a and beverage outlets 13b, respectively.
The ratio of the volume of the two zones 12, 14 within the solid block is an
important relationship when dispensing beer at critical temperatures, often as
low as -
2 C. In a preferred embodiment the volume ratio of the designated beverage
cooling
zone 14 to the cold zone 12 is about 150:100.
In use, the cold zone 12 or core acts as a thermal storage of energy. This
thermal
storage is used to maintain controlled beverage outlet temperatures to avoid
the
fluctuations that are typical with the heat exchangers described in the prior
art.
The distance between the coils of the coolant coil arrangement may be varied
to
control the rate of heat transfer from the coolant into the solid core. With
reference to
Figure 3, in the preferred embodiment the distance "b" between the exteriors
of the
tubes is between 3 and 10 mm.
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The diameter of the tubes used in the coolant coil for transfer of cold from
the
coolant to the cold zone is selected based on the energy requirement of the
system.
Typically, the diameter range would range between 6 and 13 mm.
With reference to Figure 2, the distance "a" between the tubes in the beverage
coil arrangement 13 is varied to control the rate of heat transfer from the
beverage into
the defined cold zone 12. Typically the distance between the tubes is from 3
to 8 mm.
The diameter of the tubes used in the designated cooling zone for transfer of
cold from the solid to the beverage is also selected based on the energy
requirement of
the system. Typically the diameter range for the beverage line tubes would be
between
7 and l l mm.
The distance between the coolant tubes located in the cold zone and the
beverage tubes located in the designated zone is a significant factor in
determining the
heat flow between the two defined solid areas. With reference to Figure 3, the
preferred distance "c" is between 2 and 6 mm.
This allows for predetermined heat transfer effects within the solid to
facilitate
the heat transfer from the cold zone 12 to the coolant and also from the
beverage into
the solid.
The relationship between the plane of the beverage tube coils and the coolant
tube coils ("the angle between the tubes") is important in maximising the heat
transfer
rate across the solid.
Adjusting the angle controls the heat transfer rate across the solid. As shown
in
the described embodiment the angle between the plane of the coils in the
coolant coil
and the beverage coil is 90 . It is preferred that the angle is between 80 and
110
degrees, however the angle may be anywhere between 15 and 120 degrees.
The angle provides three dimensional heat flux within the solid areas and acts
as
a means of inducing turbulence to the heat flow through the solid areas and
maximising
the available transfer of cold through the system.
Although the foregoing describes the beverage being dispensed as being
alcoholic, it will be appreciated that the system may also be used to dispense
other
beverages, particularly soft drinks, such as sodas and the like.
Although the above describes a heat exchanger having a single beverage line,
and single coolant line, it will be appreciated that more than one beverage
line may be
provided in the designated cooling zone 14 and more than one coolant line in
the cold
zone 12.
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For example, Figure 5 shows a variant 110 of the heat exchanger of Figures 1
to
4 in which there is a second beverage line 113 running parallel to the first
beverage line
13.
Figure 6 shows a further variant 210 in which there are two coolant lines "in
series" defining the (inner) cold zone 12. A first coolant line 213 comprises
a helical
coil and a coolant inlet 213a and a coolant outlet 213b and defines one part
12a of the
inner cold zone 12. A second coolant line 223 following on in series from the
first
coolant line, comprises a helical coil and a coolant inlet 223a and a coolant
outlet 223b
and defines the other part 12b of the inner cold zone 12. The coolant inlet
223a is on
the opposite side of the block 210 to the coolant outlet 213b of the first
coolant line.
Although in the preferred embodiment, as described above, the cold zone 12 is
inside the designated beverage cooling zone 14 which has the beverage lines
passing
though it, it is possible to manufacture a heat exchanger in which the
location of the
coolant tube coils 311 and beverage line 313 coils are reversed, so that the
cold zone
312 lies outside the beverage coils 313. In this embodiment, the ratio of the
volume of
the cold zone 312 to the beverage line zone 314 remains 100::150, and the
coolant and
beverage pipe dimensions and spacings remain in the ranges described above as
does
the relationship between the plane of the beverage tube coils and the coolant
tube coils.
In a typical embodiment the angle is 90 as shown in Figure 7, although this
angle can
be varied between 80 and 110 degrees, even between 15 and 120 degrees.
It is also possible for additional lines to be present in the centre of the
cold core
block forming a third or central zone. This is illustrated in Figures 8 and 9,
where the
central zone is referenced 20 and shown as rectangular parallelepiped in
broken lines.
With reference to Figure 6 also, the central zone is used for cooling as is
the outer
designated zone. It may have one or more lines 22 passing through it - see
Figure 6. In
one embodiment the line 22 may be a glycol line for cooling glycol, used to
cool a beer
transfer conduit, and/or beer font or the like. In an alternative application
there may be
up to twenty additional lines 22 for pre-chilling e.g. soda or soft drinks.
As shown in Figures 8 and 9, where the central zone is present and used for
cooling, the volume ratio of the central zone 20 to the inner cold zone 12 to
the outer
zone 14 is typically about 150: 100: 150.
It will be appreciated by persons skilled in the art that numerous variations
and/or modifications may be made to the invention as shown in the specific
embodiments without departing from the scope of the invention as broadly
described.
The present embodiments are, therefore, to be considered in all respects as
illustrative
and not restrictive.
