U.S. patent application number 15/513468 was filed with the patent office on 2017-10-26 for heat transfer apparatus.
This patent application is currently assigned to 42 TECHNOLOGY LIMITED. The applicant listed for this patent is 42 TECHNOLOGY LIMITED. Invention is credited to Stuart Mark BANISTER, Andrew David CHAPMAN, Simon Philip JELLEY.
Application Number | 20170307282 15/513468 |
Document ID | / |
Family ID | 51869246 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170307282 |
Kind Code |
A1 |
JELLEY; Simon Philip ; et
al. |
October 26, 2017 |
HEAT TRANSFER APPARATUS
Abstract
Disclosed herein is a heat transfer device (2), the heat
transfer device comprising a heat exchanger (10) driven by movement
of a fluid, a heat transfer cavity (6) and a fan (12) for creating
a circulating gas flow between the heat exchanger and the heat
transfer cavity. The heat transfer device (2) includes: a housing
having an opening (14) for allowing an object to be inserted into
the heat transfer cavity (6); an outlet valve (52) for exhausting
gas and/or liquid from the heat transfer cavity (6); and a
controller arranged to operate the outlet valve (52). The heat
transfer device (2) may, for example, take the form of a cooling
device for rapidly cooling a drinking vessel such as a beer
glass.
Inventors: |
JELLEY; Simon Philip;
(Cambridge, Cambridgeshire, GB) ; BANISTER; Stuart
Mark; (Peterborough, Cambridgeshire, GB) ; CHAPMAN;
Andrew David; (Peterborough, Cambridgeshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
42 TECHNOLOGY LIMITED |
CAMBRIDGESHIRE |
|
GB |
|
|
Assignee: |
42 TECHNOLOGY LIMITED
CAMBRIDGESHIRE
GB
|
Family ID: |
51869246 |
Appl. No.: |
15/513468 |
Filed: |
September 22, 2015 |
PCT Filed: |
September 22, 2015 |
PCT NO: |
PCT/GB2015/052720 |
371 Date: |
March 22, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25D 2500/02 20130101;
F25D 17/06 20130101; F25D 21/004 20130101; F25D 31/008 20130101;
F25D 21/08 20130101; F25D 21/14 20130101 |
International
Class: |
F25D 21/14 20060101
F25D021/14; F25D 21/00 20060101 F25D021/00; F25D 17/06 20060101
F25D017/06; F25D 21/08 20060101 F25D021/08; F25D 31/00 20060101
F25D031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2014 |
GB |
1416666.4 |
Claims
1. A heat transfer device comprising: a heat exchanger driven by
movement of a fluid therein, a heat transfer cavity and a fan for
creating a circulating gas flow between the heat exchanger and the
heat transfer cavity; a housing having an opening for allowing an
object to be inserted into the heat transfer cavity; an outlet
valve for exhausting gas and/or liquid from the heat transfer
cavity; and a controller arranged to operate the outlet valve.
2. A heat transfer device according to claim 1, wherein the heat
transfer cavity comprises an outlet flow path arranged to direct
liquid towards the outlet valve.
3. A heat transfer device comprising: a heat exchanger, a heat
transfer cavity and means for creating a circulating gas flow
between the heat exchanger and the heat transfer cavity; a housing
having an opening for allowing an object to be inserted into the
heat transfer cavity; and an outlet valve for exhausting gas and/or
liquid from the heat transfer cavity; wherein the heat transfer
cavity comprises an outlet flow path arranged to direct liquid
towards the outlet valve.
4. A heat transfer device according to claim 2, wherein the outlet
flow path is inclined downwardly in a radial and/or circumferential
direction so as to direct liquid towards the outlet valve.
5. A heat transfer device according to claim 2, wherein the outlet
flow path provides a helical incline towards the outlet valve.
6. A heat transfer device according to claim 1, wherein the outlet
valve comprises an outlet opening that is directed substantially
tangential to the direction of the circulating gas flow.
7. A heat transfer device according to claim 6, wherein the outlet
opening is substantially positioned at a periphery of the fan.
8. A heat transfer device according to claim 1, wherein the outlet
valve comprises an outlet opening having a cross-sectional area of
at least about 50 mm.sup.2.
9. A heat transfer device according to claim 1, further comprising
a funnel arranged adjacent to the outlet valve to collect
liquid.
10. A heat transfer device according to claim 1, wherein the heat
transfer device is a cooling device and the heat exchanger is a
thermal sink arranged to cool the circulating gas flow.
11. A heat transfer device according to claim 1, wherein the
controller is further arranged to control the fan.
12. A heat transfer device according to claim 1, wherein in a
("defrost") mode of operation the heat exchanger is no longer
driven and the controller opens the outlet valve.
13. A heat transfer device according to claim 12, wherein in the
("defrost") mode of operation the controller operates the fan at an
increased speed so as to circulate the gas flow more rapidly.
14. A heat transfer device according to claim 12, further
comprising a heater operating in the ("defrost") mode of operation,
and optionally wherein the heat exchanger acts as the heater.
15. (canceled)
16. A heat transfer device according to claim 1, wherein the outlet
valve is arranged to automatically drain liquid from the heat
transfer cavity upon loss of electrical power to the heat
exchanger, or the controller operates to open the outlet valve in
response to a power cut detection signal.
17. (canceled)
18. A heat transfer device according to claim 1, wherein the outlet
valve is biased open but held closed by an electromechanical
actuator.
19. A heat transfer device according to claim 1, wherein the outlet
valve is actively opened upon loss of electrical power.
20. (canceled)
21. A heat transfer device according to claim 1, comprising means
for storing electrical power and/or means for generating electrical
power so that the outlet valve can be opened in response to a power
cut.
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68. A method of drying a heat transfer device comprising a heat
transfer cavity that can receive an object, the method comprising:
creating a circulating gas flow in the heat transfer cavity;
ceasing to cool or heat the circulating gas flow; and opening an
outlet valve to exhaust gas and/or liquid from the heat transfer
cavity.
69. A method according to claim 68, further comprising: increasing
the rate of the circulating gas flow.
70. (canceled)
71. (canceled)
Description
[0001] The present invention relates to heat transfer devices that
may be used to cool or heat an object to a desired temperature, and
corresponding methods of cooling or heating an object. The
invention also relates to cooling apparatus and methods of drying a
heat transfer device, for example after use.
[0002] WO 2011/042698 describes a heat transfer device for hygienic
cooling of objects such as drinking vessels. A rapid cooling effect
is achieved using turbulence to generate a frosted effect. However
this method of rapid heat transfer requires high rates of air
circulation e.g. high fan speeds. It may be inefficient to have the
fan running at high speed all the time and, in addition, there may
be potential problems with frost build-up. It would be desirable
for a rapid frosting mode to be turned on/off as required. However
the very cold temperatures in such a cooling device, and the
internal build-up of frost, add to the complexity of achieving
reliable means of control. The present invention seeks to improve
known heat transfer devices and corresponding methods.
[0003] According to a first aspect of the present invention there
is provided a heat transfer device comprising: a heat exchanger, a
heat transfer cavity and means for creating a circulating gas flow
between the heat exchanger and the heat transfer cavity; a housing
having an opening for allowing an object to be inserted into the
heat transfer cavity; a sensor arranged to provide a detection
signal when an object is inserted into the heat transfer cavity;
and a controller for adjusting the rate of circulating gas flow in
response to a detection signal from the sensor. It will be
appreciated that such a device is able to intelligently control the
rate of circulating gas flow by using the sensor to detect when an
object is inserted into the heat transfer cavity. For example, upon
receiving a detection signal from the sensor, the controller may
increase the rate of circulating gas flow between the heat
exchanger and the heat transfer cavity so as to enter a rapid heat
transfer mode. This may be particularly efficient where the heat
transfer cavity is arranged to create turbulence in the circulating
gas flow. As is discussed in WO 2011/042698, a highly turbulent gas
flow has been found to generate a high heat transfer coefficient
and thereby accelerate heat exchange with the object. Thus, in
preferred embodiments the circulating gas flow may be constrained
to pass through a gap adjacent the object that is defined by the
heat transfer cavity so as to promote turbulence in the circulating
gas flow. This aspect of the invention also includes a method of
cooling or heating an object, comprising: creating a circulating
gas flow in a heat transfer cavity that can receive an object;
cooling or heating the circulating gas flow; sensing when an object
is inserted into the heat transfer cavity; and adjusting the rate
of circulating gas flow in response to said sensing.
[0004] Some of the ways in which the rate of circulating gas flow
can be adjusted are discussed further below.
[0005] It is important that the sensor can reliably detect when an
object is inserted into the heat transfer cavity. While a manual
switch could be used to control adjustment of the rate of
circulating gas flow, for example activated by a user when/after
inserting an object, this requires additional interaction. It is
advantageous for the device to automatically detect an object and
trigger the rapid heat transfer mode without intervention being
required. In some embodiments the sensor comprises at least one
contact sensor, for example a mechanical contact sensor such as a
microswitch, that may be activated directly or indirectly when an
object is inserted into the heat transfer cavity. For example, a
contact sensor may be activated directly by the passage of the
object through the opening or by the seating of the object in the
heat transfer cavity. A pressure pad could be used to detect when
an object is present in the heat transfer cavity. Or, in another
example, a contact sensor may be activated indirectly by movement
of another part that takes place when an object is inserted into
the heat transfer cavity, e.g. movement of a seal that closes the
opening when an object is not present.
[0006] The Applicant has found that the reliability of a contact
sensor can be readily degraded by environmental factors. Especially
when the heat transfer device is a cooling device, a tendency for
ice to build up can interfere with proper operation of a contact
sensor. It is therefore preferable for the sensor to comprise at
least one non-contact sensor. Appropriate non-contact sensors may
include sensors for electromagnetic radiation (e.g. optical,
near-infrared, far-infrared, ultraviolet), ultrasound transducers,
and capacitive sensors. Some example of contactless sensor
arrangements will now be discussed in more detail, however, it is
envisaged that other non-contact sensor technologies may also be
employed.
[0007] In a set of embodiments the non-contact sensor may comprise
an active or passive sensor arrangement for electromagnetic
radiation or ultrasound. In a passive sensor arrangement, for
example, the non-contact sensor may simply comprise a sensor that
detects ambient conditions and/or a change due to electromagnetic
radiation being emitted, scattered, lensed, obstructed, absorbed or
reflected by an object that is inserted in the heat transfer
cavity. A passive receiver such as a photocell or photodiode may
simply detect changes in light level when an object is inserted,
e.g. increased brightness as an object opens a seal that closes the
opening or reduced brightness when an object prevents ambient light
from reaching the sensor. In other examples the sensor may comprise
a vision camera that provides an optical image of the opening
and/or heat transfer cavity and uses appropriate software to
determine when an object is inserted or present. However such
passive optical sensors are sensitive to ambient lighting
conditions, which may be highly variable e.g. at different times of
day. A heat transfer device used to cool glasses may be located in
a bar or nightclub with flashing lights.
[0008] In yet other examples, the sensor may comprise an infrared
(IR) sensor that detects changes in thermal emission when an object
is inserted into the heat transfer cavity, preferably a
far-infrared (FIR) sensor. The sensor may comprise a simple IR
thermopile or an IR camera that images the infrared radiation
emitted by the object and its surroundings. As the object will
likely be at a different temperature to the heat transfer cavity
when it is first inserted (e.g. a warm object entering a cool
cavity), the infrared sensor or camera can use the change in signal
or contrast in a thermal image to generate a detection signal. A
passive infrared sensor using thermal emission can provide reliable
results even if there are changing ambient light conditions. In
some embodiments the IR sensor or camera may be positioned above
the opening and, optionally, angled to look down on the opening.
This may ensure that the sensor has a good view of the normally
cold interior environment of the heat transfer cavity and is
therefore sensitive to temperature change when an object is
inserted into the cavity. In an active sensor arrangement, the
non-contact sensor may comprise a radiation emitter and a radiation
receiver that detects reflection and/or transmission of the emitted
electromagnetic radiation. This can reduce the arrangement's
sensitivity to background illumination. For example, the sensor can
detect a background radiation reading when the emitter is off and
compare this value to the reading when the emitter is on. In
addition, or alternatively, the radiation emitter may emit
frequencies of the electromagnetic spectrum that are not visible to
the human eye, e.g. near-IR or ultraviolet light, so as to avoid
light beams that could potentially annoy or distract a user.
Ultraviolet may be more readily reflected or scattered by an object
being detected, but there may be risks associated with the use of
ultraviolet radiation in close proximity to a user who is inserting
the object. An infrared sensor arrangement may be preferred for
user safety. In particular, a sensor arrangement comprising an
infrared emitter operating in a narrow band, e.g. the wavelength
range of 800-1000 nm, has the advantage of the receiver being able
to readily filter out broadband sources such as artificial
lighting. Such arrangement can conveniently be achieved using
low-cost emitters (e.g. infrared LEDs) and receivers (e.g. infrared
photodiodes) that are readily available.
[0009] In various embodiments it can be desirable for a radiation
sensor (e.g. operating at visible or infrared wavelengths) to
detect an object, such as a drinking vessel, that is made of
transparent material e.g. glass or clear plastic. This can make it
difficult for the non-contact sensor to operate in a transmission
mode as radiation may shine straight through the object. One
possibility is for such objects to include opaque markings (for
example printed or etched on the transparent material) that can
obstruct the transmitted radiation to increase detection. However
this may not be feasible or desirable to implement in practice.
[0010] Even a reflectance sensor can be hindered by the shiny
nature of such materials, making it difficult to differentiate
between reflection of the emitted radiation from the object and
background reflections from the ambient illumination. A non-contact
sensor comprising a radiation emitter and a radiation receiver,
operating in a reflection mode, may be angled so as to better pick
out reflections from an expected object. However the angle of such
reflectance measurements may need to be adjusted for different
objects and this can reduce the reliability of the sensor when the
device is used with more than one size or type of object, e.g.
different glass shapes.
[0011] In another example, a non-contact reflectance sensor may use
binocular range sensing to determine the distance to an object from
a correlation of the radiation reflected and/or scattered by the
object. Such a sensor arrangement may be able to differentiate
between the weak reflections from a transparent object (such as a
glass) and background light reflections. An infrared proximity
sensor such as the Sharp GP2Y0A21YK may be suitable.
[0012] The Applicant has devised a novel kind of active sensor
arrangement, comprising an electromagnetic radiation emitter and
receiver, that can detect an object from transmission of the
emitted radiation. This arrangement can be particularly suitable
for transparent objects that may have a lensing effect on a
transmitted beam. In such preferred embodiments the non-contact
sensor comprises an electromagnetic radiation emitter and a
corresponding electromagnetic radiation receiver arranged on
opposite sides of the opening to define a transmission path passing
through an object that is inserted through the opening. In the
absence of an object the transmission path may be straight. When a
transparent object, such as glass drinking vessel, is present in
the opening it can have a beam bending effect so that the emitted
radiation does not follow the transmission path to reach the
receiver. This effect may be optimised by arranging the radiation
emitter and receiver at a height (e.g. at, above or below the
opening) corresponding to the expected height of a detectable
feature on an object when inserted through the opening, for example
a height corresponding to the thickened base of a glass or some
other feature e.g. etched onto the glass. It can be advantageous
for the sensor to be sensitive to objects of a particular height as
this can ensure that the device only operates with certain objects,
for example intended glassware.
[0013] The radiation emitter and receiver may be arranged
diametrically on opposite sides of the opening, so as to define a
transmission path passing through a region central to the opening.
However, the Applicant has surprisingly found that the beam bending
effect may be greater for an off-centre transmission path. It is
therefore preferable that the radiation emitter and receiver are
arranged non-diametrically on opposite sides of the opening, so as
to define an off-centre transmission path. This makes it more
likely for an intervening object to deflect the emitted radiation
from the transmission path so that it does not reach the receiver.
The sensor may compare an output from the receiver with a preset
threshold to determine when an object is present in the
transmission path. Preferably the emitter is a pulsed source of
radiation. This enables the sensor to compare the radiation
received when the emitter is on and off. In addition, or
alternatively, the sensor may filter the output from the receiver
so as to be sensitive to a wavelength of the emitted radiation.
[0014] Another example of an active sensor arrangement uses
ultrasound. The non-contact sensor may comprise an ultrasound
transducer or transceiver e.g. arranged to emit an ultrasound pulse
and detect reflection of the pulse when an object is inserted
through the opening and/or present in the heat transfer cavity. The
ultrasound transducer may be continually pulsed and the
time-of-flight measured for reflections. A longer time-of-flight
for reflections crossing the opening and/or the heat transfer
cavity may indicate the absence of an object while a shorter
time-of-flight may indicate the presence of an object. A suitable
type of ultrasound sensor is the SRF series available from
Devantech Ltd. An advantage of such an ultrasonic range sensor is
that it may be able to detect the presence of wide range of
different objects, regardless of their optical properties. A
detection signal provided by an ultrasound transducer may be less
sensitive to the build-up of frost on an object being cooled, which
could interfere with electromagnetic sensing techniques. Such an
ultrasound transduce is preferably waterproof, so as not to be
affected by condensation or ice.
[0015] In another set of embodiments the non-contact sensor may
comprise a capacitive sensor arrangement. Many objects are made of
insulating materials, such as ceramic or glass, which have a
relatively high permittivity. For example, glass has a relative
permittivity of between around 4 and 10, which gives good
detectability in air using capacitive sensing. The capacitive
sensor arrangement may operate by exciting electrodes to different
voltages (e.g. using a high frequency signal) and monitoring
current, e.g. the charge transferred for a given voltage change or
the lead time between current and voltage. In various examples the
capacitive sensor arrangement may comprise at least one electrode
arranged to sense a capacitance change indicating proximity of an
object inserted through the opening and/or into the heat transfer
cavity. Such a capacitive sensor arrangement may comprise a pair of
electrodes arranged to generate a fringe field that will be
interrupted when an object is inserted into the heat transfer
cavity. However, the Applicant has found that off-the-shelf fringe
field capacitive sensors may not provide sufficient sensitivity as
they typically require an object to approach within a few
millimetres for detection. This can cause a problem if objects of
different size or dimensions are inserted into the heat transfer
cavity. Furthermore, in a cooling device a typical capacitive
sensor may be sensitive to frost build-up and provide false
readings. For example, the Applicant has found that a thin layer of
ice in close proximity to a capacitive sensor can give a reading
that is very similar to that of a glass-walled object such as a
drinking vessel. The Applicant has devised a novel capacitive
sensor arrangement that may be particularly suitable for a heat
transfer device in which the heat transfer cavity is shaped to
receive a hollow object such as a drinking vessel. The capacitive
sensor arrangement preferably comprises a pair of electrodes
arranged in the heat transfer device to receive an object
therebetween. The electrodes may be at least partially annular and
preferably arranged concentrically so that an object, such as a
drinking vessel, can be received between inner and outer
electrodes. The electrodes may not be fully annular, so as to save
on material, but the Applicant has found that a higher surface area
is beneficial to help eliminate sensitivity to local ice build-up
and improve reliability of object detection. The electrodes may
therefore be substantially cylindrical or frustoconical.
[0016] In a preferred set of embodiments the heat transfer cavity
may be formed, at least in part, by a separable and/or removable
ducting member. For example, the ducting member may comprise a
generally cylindrical sheath that is shaped to receive an inverted
drinking vessel such as a beer glass. It is advantageous for the
ducting member to be a separable insert so that it can be removed
from the device to be cleaned. A further advantage is that
different ducting members may be fitted to match different drinking
vessels in use, without needing to change the rest of the device.
This can be particularly beneficial when the ducting member defines
a gap adjacent the object that is chosen to promote turbulence in
the circulating gas flow. In embodiments where the sensor comprises
a capacitive sensor arrangement, the ducting member may
conveniently position or carry one or more of the electrodes.
Although the ducting member may be formed of plastics material(s),
it can carry a conductive e.g. metallic layer or conductive coating
to form the electrode(s). Where the electrode(s) are carried by the
ducting member then a separable electrical connection may be
provided. Otherwise the electrode(s) may be positioned inside or
outside the ducting member with a permanent electrical connection.
In a further set of embodiments the circulating gas flow may be
created by a fan positioned inside or below the heat transfer
cavity, for example beneath the ducting member. The gas flow may be
circulated by the fan through a generally cylindrical exhaust tube
that is arranged concentrically inside the ducting member. The
exhaust tube can conveniently position or carry one of the
electrodes of a capacitive sensor arrangement, e.g. without the
need for a separable electrical connection.
[0017] Of course it will be appreciated that the heat transfer
device may include more than one sensor, in particular one or more
of the different sensor arrangements discussed above, in any
combination. The use of multiple sensors may provide for increased
reliability, with a detection signal being required from more than
one sensor before the controller operates. In addition, or
alternatively, the use of multiple sensors may provide a failsafe
in the event that one of the sensors becomes inoperative e.g. due
to frost build-up in a cooling device. In a preferred set of
embodiments the sensor(s) are chosen so as to detect when a
drinking vessel is inserted into the heat transfer cavity. The
sensor(s) may be integrated with an opening and/or heat transfer
cavity that are sized or shaped to receive a given type of drinking
vessel, for example a particular kind of beer glass. As is
mentioned above, the sensor(s) may be arranged so as to provide a
detection signal only when a certain type of drinking vessel is
inserted, e.g. to prevent the device from being used with certain
beer glasses.
[0018] There will now be described some further features of the
heat transfer device that apply irrespective of the type of
sensor.
[0019] In some examples the device may not operate when an object
is not present, and the rate of circulating gas flow may therefore
be increased from zero upon detecting that an object is inserted
into the heat transfer cavity. However, in many examples it is
preferable for the device to operate at least in a standby mode,
with a certain minimum rate of circulating gas flow, so as to help
maintain the heat transfer cavity within a certain temperature
range even when an object is not present. In a particularly
preferred set of embodiments, the heat transfer device is a cooling
device and the heat exchanger is a thermal sink arranged to cool
the circulating gas flow. For example, the minimum rate of
circulating gas flow may be chosen to maintain the heat transfer
cavity at a temperature in the range of about -35.degree. C. to
-45.degree. C. When the sensor detects that an object has been
inserted into the heat transfer cavity, the controller may increase
the rate of circulating gas flow so as to enter a rapid heat
transfer mode, e.g. a rapid cooling mode that can create a frosted
effect on the outer surfaces of the object.
[0020] It is preferable that the rapid heat transfer mode continues
only for as long as necessary to bring the object to a desired
temperature, as the high rate of circulating gas flow might have a
high energy demand. Where the heat transfer device is a cooling
device, it may not be desirable to prolong the rapid cooling mode
as this could result in an unwanted build-up of ice on the object
or in the heat transfer cavity. During rapid circulation, any
ambient (typically damp) air that leaks into the heat transfer
cavity will be mixed in more, and for a cooling device this can
cause excess frost as well as requiring extra energy input. In
addition, the means for creating the circulating gas flow (e.g. a
fan) may dissipate significant energy during operation, both
demanding energy and requiring further cooling of the heat transfer
cavity, thereby lowering the efficiency of the device. In various
examples the rapid cooling mode is terminated once a desired
frosting effect has been achieved for the object. Preferably the
controller reduces the rate of circulating gas flow after an object
has undergone a desired heat transfer treatment.
[0021] In a set of embodiments the sensor may further be arranged
to detect when an object is removed from the heat transfer cavity.
The controller may then adjust the rate of circulating gas flow in
response to a further detection signal from the sensor indicating
removal of the cooled/heated object. Preferably the controller
decreases the rate of circulating gas flow so as to enter a standby
mode. As is mentioned above, the standby mode could be one in which
the circulating gas flow is turned off completely, or a "keep
cold/warm" mode where the gas flow is circulated at a lower rate to
maintain the heat transfer cavity within a particular temperature
range. However there may be times when an object is inserted into
the device and not removed for immediate use but instead left
inside the heat transfer cavity. A user may forget to remove the
object or may choose to leave the object in a cooled/heated state
until it is required. It would be inefficient for the device to
maintain the rapid heat transfer mode indefinitely. The device may
provide a user alert when the controller determines that an object
is ready to be removed, but it may be desirable to switch out of
the rapid heat transfer mode without needing to remove the
object.
[0022] In another set of embodiments, alternatively or in addition,
the controller may be further arranged to adjust the rate of
circulating gas flow so as to exit the rapid heat transfer mode,
e.g. in response to a manual input, a timer signal or a temperature
signal. In a first set of examples a user may provide a manual
input when it is judged that the object has been heated/cooled to a
desired degree. This allows a user to dictate the result that is
achieved and makes the device more flexible. However it may instead
be desirable to avoid a perception of variability and ensure that a
repeatable heat transfer treatment is achieved by the device
automatically ending the rapid heat transfer mode.
[0023] In a second set of examples, alternatively or in addition,
the controller may respond to a temperature signal indicating that
the object has reached a desired temperature. The temperature
signal may be provided by the same sensor that detects when an
object is inserted, or a further sensor, for example a passive
infrared sensor. In a third set of examples, alternatively or in
addition, the controller may respond to a timer signal. For
example, the controller may set a simple time limit triggered by
the detection signal when an object is first inserted into the heat
transfer cavity. The controller may be programmed with different
time limits for different objects, which could be set manually or
informed by the detection signal (e.g. based on the type of object
that is detected). In at least some examples, the controller may
monitor a temperature signal or a timer signal during the rapid
heat transfer mode and determine the length of time left in that
mode. An audible and/or visible countdown may be provided to inform
a user of how long the object needs to stay in the heat transfer
device. Of course one or more of these techniques may be provided
in the same device, for example a default timer in case a user does
not remove the object from the heat transfer cavity or its removal
is not detected for some reason. When the controller operates to
adjust the rate of circulating gas flow so as to exit the rapid
heat transfer mode, a communication signal may be output by the
device. The communication signal may comprise an audible and/or
visible alert to a user that the rapid heat transfer mode has ended
and e.g. the object is ready to be removed. As is mentioned above,
as a default the device may operate in a standby mode with a
certain minimum rate of circulating gas flow, so as to help
maintain the heat transfer cavity within a certain temperature
range even when an object is not being rapidly cooled/heated. Where
the device is a cooling device, it has been found beneficial to
maintain relatively cold temperatures throughout the internal gas
flow path by recirculating the cold gas, e.g. so that temperatures
remain cold even further away from the heat exchanger. In
embodiments where the circulating gas flow is generated by a fan or
other mechanical device, such a standby mode can prevent ice
build-up from locking the moving parts, as might occur if there was
zero circulation in between rapid cooling modes.
[0024] In a set of embodiments the device operates in a standby
mode where the heat exchanger is operating (e.g. circulating
refrigerant through heat exchange coils) and there is a gas flow
circulating between the heat exchanger and the heat transfer
cavity. The gas flow may be circulated at a lower rate than in the
rapid heat transfer mode. Preferably the heat exchanger is driven
to provide substantially the same heat transfer rate in the standby
mode as in the rapid heat transfer mode (for a given rate of
circulating gas flow). For example, refrigerant may be circulated
through the heat exchanger at the same rate and temperature. Of
course the rate of circulating gas flow does not need to stay
constant in the standby mode but could be adjusted, e.g. based on a
temperature measurement for the heat transfer cavity. In such a
standby mode the heat transfer cavity of a cooling device may, for
example, be maintained in a range of about -35.degree. C. to
-45.degree. C. This may be considered a "peak" standby mode as the
heat transfer cavity is kept at temperature range quite far from
ambient and is ready to move into a rapid heat transfer mode at any
time. Such a "peak" standby mode would be ideal for a device that
is in regular use, for example to frost glasses in a bar during
evening service.
[0025] The Applicant has recognised that there may be "off-peak"
times when it is desirable to keep the device running, but with a
lower energy demand, e.g. when objects may still need to be
cooled/heated but less frequently than at peak times of use. One
option could be to further adjust e.g. reduce the rate of
circulating gas flow. However, without a certain rate of
recirculation it has been found that ambient air can more readily
leak into the heat transfer cavity and quickly change its
temperature. Where the heat exchanger is passive, e.g. fins simply
arranged to exchange heat with the atmosphere, there may be little
scope to change its effect on the circulating gas flow. On the
other hand, it has been recognised that an active heat exchanger
can provide for control of the cooling/heating effect without
necessarily adjusting the rate of circulating gas flow. Thus, in
preferred embodiments, the heat exchanger is driven to provide a
first heat transfer rate for a given rate of circulating gas flow
in a first ("peak") mode of operation, and a second, lower heat
transfer rate for the same given rate of circulating gas flow in a
second ("off-peak") mode of operation. A controller may be arranged
to switch between the first and second modes of operation. This is
considered novel and inventive in its own right. According to a
second aspect of the present invention there is provided a heat
transfer device comprising: a heat exchanger, a heat transfer
cavity and means for creating a circulating gas flow between the
heat exchanger and the heat transfer cavity, wherein, in a first
("peak") mode of operation, the heat exchanger is driven to provide
a first heat transfer rate for a given rate of circulating gas flow
and, in a second ("off-peak") mode of operation, the heat exchanger
is driven to provide a second, lower heat transfer rate for the
same given rate of circulating gas flow; and a controller arranged
to switch between the first and second modes of operation. It will
be appreciated that such a device can be controlled so as to switch
between "peak" and "off-peak" modes of operation without
necessarily adjusting the rate of circulating gas flow. By actively
driving the heat exchanger to provide different average heat
transfer rates, the temperature of the heat transfer cavity may be
allowed to change but the circulating gas flow can ensure that
there is an even temperature distribution. This can keep the device
primed so that a desired cooling/heating effect is achieved when an
object is inserted into the heat transfer cavity and the controller
then adjusts the rate of circulating gas flow e.g. so as to enter a
third, rapid heat transfer mode. In the context of
vapour-compression refrigeration, it will be understood that what
is meant by the heat exchanger being "driven" is the heat transfer
rate achieved as a result of movement of a coolant fluid therein,
for example movement of a refrigerant in the coils of a heat
exchanger. This may depend on factors including (but not limited
to) the choice of fluid driving the heat exchanger, the fluid flow
rate, and the temperature of the fluid before it undergoes heat
exchange. In the context of thermoelectric heat transfer using the
Peltier effect, the heat exchanger may be "driven" at different
heat transfer rates by varying the voltage applied across (or
current through) the solid state device. Other types of heat
exchanger may also be envisaged that allow for the heat transfer
rate to be adjusted e.g. depending on the power supplied to the
heat exchanger.
[0026] This aspect of the invention also includes a method of
cooling or heating an object, comprising: creating a circulating
gas flow in a heat transfer cavity that can receive an object;
cooling or heating the circulating gas flow; in a first ("peak")
mode of operation, cooling or heating the circulating gas flow at a
first heat transfer rate for a given rate of circulating gas flow;
in a second ("off-peak") mode of operation, cooling or heating the
circulating gas flow at a second, lower heat transfer rate for the
same given rate of circulating gas flow; and switching between the
first and second modes of operation.
[0027] In preferred embodiments, the controller is arranged to
switch to a third mode of operation wherein the given rate of
circulating gas flow is adjusted when an object is inserted into
the heat transfer cavity. For example, the given rate of
circulating gas flow may be increased to provide a rapid heat
transfer mode. In the third mode of operation the heat exchanger
may also be driven to provide the first, higher, heat transfer
rate. Where the device is starting in the second ("off-peak") mode,
the heat exchanger may therefore be adjusted at substantially the
same time as adjusting the rate of circulating gas flow. Such a
rapid heat transfer mode may be triggered manually or
automatically. In examples of the latter, the heat transfer device
may comprise a sensor arranged to detect when an object is inserted
into the heat transfer cavity. Any of the sensor features described
hereinabove may equally apply to such embodiments.
[0028] It will be appreciated that the starting temperature of the
heat transfer cavity in the third mode of operation may be
different, depending on whether the controller has switched from
the first ("peak") mode or the second ("off-peak") mode to the
third mode. Where the heat transfer device is a cooling device, for
example, the heat transfer cavity may be warmer starting from the
second ("off-peak") mode. It may therefore take longer to achieve a
desired cooling effect, for example to frost a drinking vessel. The
time spent in the third mode of operation, for example to achieve
rapid cooling of an object inserted into the heat transfer cavity,
can be adjusted to take this into account. Thus in a preferred set
of embodiments the controller is arranged to switch to the third
mode of operation for a time period that is adjusted, preferably
lengthened, depending on the preceding mode of operation, e.g. peak
or off-peak. During a generally off-peak period of usage, an
increased frosting time may be acceptable and can advantageously
compensate for the warmer starting temperature of the heat transfer
cavity. Accordingly the controller is preferably arranged to switch
to the third mode of operation for a time period that is longer
when the preceding mode of operation is off-peak rather than peak.
This may also be more energy efficient, as it has been found that
when the device is used less frequently the heat transfer cavity
only warms due to heat gain through its insulation as there is
little mixing with ambient air from objects being inserted.
However, if the controller were to detect an increase in usage
indicating that the off-peak mode is no longer appropriate, then it
may act to re-adjust the time period for rapid heat transfer
despite the preceding off-peak mode. For example, the controller
may react to increased load (e.g. multiple glass frostings
requiring a higher throughput) in the third mode of operation to
provide a faster cooling period than the lengthened one, despite
the preceding off-peak mode, thereby maximising performance and
efficiency.
[0029] As is mentioned above, the controller may switch from either
the first ("peak") mode or the second ("off-peak") mode to the
third mode of operation, e.g. in response to a detection signal
that an object has been inserted into the heat transfer cavity. If
the device has been operating in the off-peak mode for some time
then it may be desirable to control the heat exchanger so as to
move back to the first, higher, heat transfer rate in the third
mode. However, if the device has only recently switched to the
off-peak mode then there may have been little or no change in the
temperature of the heat transfer cavity and no instant need to
increase the heat transfer rate. The device may be switched back to
the off-peak mode after the third mode has provided for rapid
cooling/heating of the object. So as to avoid cycling the heat
exchanger unnecessarily, the controller may use a timer to
determine whether to change the heat transfer rate at the same time
as adjusting the rate of circulating gas flow when entering the
third mode. For example, the controller may only switch the heat
exchanger to the first, higher, heat transfer rate in the third
mode when the timer determines that the device was operating in the
second ("off-peak") mode for a minimum preceding delay, e.g. at
least two minutes.
[0030] Where the heat transfer rate of the heat exchanger is also
dependent on the temperature of the heat transfer cavity, this is
assumed to be constant for the purpose of comparing the (average)
first and second heat transfer rates. It will be appreciated that
the heat transfer rate of the heat exchanger may be actively
adjusted in any suitable way. In various embodiments the heat
exchanger may form part of a heat exchange circuit driven by
movement of a fluid therein to provide the first or second heat
transfer rate. For example, the heat transfer rate may be adjusted
by controlling the temperature and/or speed of the fluid. Where the
heat transfer device is a cooling device, for example, the heat
exchanger may form part of a refrigerant circuit driven by a moving
coolant fluid e.g. a refrigerant. In the second ("off-peak") mode
of operation the heat transfer rate may be lowered by reducing or
stopping movement of the coolant fluid through the heat exchanger,
or by reducing the degree of cooling of the coolant fluid before it
reaches the heat exchanger. For instance, in a typical refrigerant
circuit the coolant fluid is circulated through a compressor (and
optionally a condenser) e.g. a condensing unit before being passed
to the heat exchanger and this may be controlled. A variable speed
compressor may be used. The heat exchange circuit may be controlled
in response to a temperature signal from a sensor located in the
heat transfer cavity.
[0031] In the second ("off-peak") mode of operation the entire heat
exchanger could be pulsed on and off to provide a second heat
transfer rate that is, on average, lower than the first heat
transfer rate. Even when the heat exchanger is not being actively
driven, its thermal mass (for example, the copper coils that carry
the coolant fluid) can continue to provide a cooling effect e.g.
even when the condensing unit (in particular the compressor) is
turned off. This may continue to cool (or heat) the circulating gas
flow in the heat transfer cavity. However constant cycling of all
the components in a heat exchange circuit, such as a refrigerant
circuit, may cause excessive wear or other damage. In some
embodiments the heat exchanger may be driven to provide a lower
heat transfer rate that is not zero i.e. the heat exchanger keeps
running but with a lower heat transfer effect. As is mentioned
above, in embodiments where the heat transfer device is a cooling
device and the heat exchanger is driven by movement of a coolant
fluid provided by a refrigerant device, a lower heat transfer rate
may be achieved by circulating the coolant fluid at a reduced rate.
This may be beneficial in that it keeps the refrigerant device
loaded. In other embodiments the heat exchanger may be turned on
and off, but using a timer control to ensure that such cyclic
operation is not too frequent, e.g. a minimum time delay of two
minutes between switching of the first and second modes.
[0032] Where the heat transfer device is a cooling device, in the
second ("off-peak") mode of operation the heat transfer cavity may
be maintained at a higher temperature than in the first ("peak")
mode of operation e.g. an off-peak temperature range of about
-25.degree. C. to -35.degree. C. compared to a peak temperature
range of about -35.degree. C. to -45.degree. C.
[0033] In some embodiments the controller may be arranged to switch
between the first and second modes of operation in response to a
manual input. For example, a user may decide when an off-peak mode
is appropriate. Alternatively, or in addition, in some embodiments
the controller may be arranged to automatically switch between the
first and second modes of operation. For example, the controller
may be programmed to intelligently switch between peak and off-peak
modes e.g. based on historical or learned usage information. Usage
information might include the frequency of use (e.g. how often an
object is inserted to be cooled/heated), the time of day, different
days of the week, the time of year, and even environmental factors
such as the ambient temperature.
[0034] In a set of embodiments the controller may switch between
the first and second modes of operation in response to a
temperature signal from a sensor located in the heat transfer
cavity. For example, a cooling device may be switched (back) into
the peak mode when warming of the cavity indicates a higher
frequency of use. Alternatively, or in addition, in a set of
embodiments the controller may switch between the first and second
modes of operation in response to a detection signal from a sensor
arranged to detect when, and how frequently, an object is inserted
into the heat transfer cavity. This may provide for a faster
reaction to increased usage than waiting for a temperature
indication. As is mentioned above, repeated switching of the heat
exchanger may be detrimental and the controller may therefore
include a timer to determine when the heat transfer rate was last
changed. For example, the controller may only switch back and forth
between the first and second modes of operation after a
predetermined delay, e.g. at least two minutes.
[0035] While the heat transfer device may be operated in various
different modes as described above, from time to time the device
may be switched off completely and the heat transfer cavity allowed
to return to ambient temperature. Especially in embodiments were
the heat transfer device is a cooling device, the low internal
temperatures of the heat transfer cavity can cause frost i.e. ice
crystals to build up. When an object is inserted through the
opening, ambient air may be drawn into the heat transfer cavity
and, as it cools below its dew point, any water vapour carried by
the ambient air will condense and freeze. Much of the resulting
frost may be deposited on the outer surfaces of the object,
contributing to a frosted effect, but after prolonged periods of
use some frost may also start to build up in the heat transfer
cavity and path of the circulating gas flow. This can have a
detrimental effect on components such as the heat exchanger and a
fan (or other means) that create the circulating gas flow. The
device may therefore be turned off from time to time so that it can
be defrosted.
[0036] When a cooling device is turned off and allowed to warm up,
any residual ice will melt and water is likely to collect in the
heat transfer cavity. Similarly, if a warming/heating device is
turned off and allowed to cool down, condensation is likely to form
in the heat transfer cavity. The melt water or condensate could be
left to evaporate naturally, but this may take some time,
especially in more humid climates. The Applicant has recognised
that it may cause potential hygiene issues for water to be left
stagnating in the device, especially if objects such as drinking
vessels are to come into contact with the heat transfer cavity when
the device is next used. It is therefore preferable that the device
can be operated in a further "defrost" or "warm-up" mode that helps
the heat transfer cavity to dry out when the device is no longer in
use. Preferably the device includes an outlet valve for exhausting
gas and/or liquid from the heat transfer cavity. A controller may
be arranged to operate the outlet valve.
[0037] According to a third aspect of the present invention there
is provided a heat transfer device comprising: a heat exchanger
driven by movement of a fluid therein, a heat transfer cavity and a
fan for creating a circulating gas flow between the heat exchanger
and the heat transfer cavity;
a housing having an opening for allowing an object to be inserted
into the heat transfer cavity; an outlet valve for exhausting gas
and/or liquid from the heat transfer cavity; and a controller
arranged to operate the fan and/or outlet valve.
[0038] Such a heat transfer device is therefore provided both with
a main opening for the heat transfer cavity and an additional
outlet valve that can be used to drain liquid from the cavity e.g.
when it is defrosting. It will be appreciated that an outlet valve,
rather than merely an outlet or exit opening, can be opened and
closed so as to selectively exhaust fluid from the heat transfer
cavity.
[0039] This aspect of the invention includes a method of drying a
heat transfer device comprising a heat transfer cavity that can
receive an object, the method comprising: creating a circulating
gas flow in the heat transfer cavity; ceasing to cool or heat the
circulating gas flow; and opening an outlet valve to exhaust gas
and/or liquid from the heat transfer cavity. The method optionally
further comprises: increasing the rate of the circulating gas
flow.
[0040] In a drying or "defrost" mode of operation the heat
exchanger is no longer driven and the controller may open the
outlet valve. In addition, the controller may optionally operate
the fan so as to create or maintain the circulating gas flow. In
preferred embodiments the controller may operate the fan at an
increased speed so as to circulate the gas flow more rapidly. The
fan may, for example, be operated to create an increased rate of
circulating gas flow e.g. corresponding to a rapid cooling mode as
described above. The circulating gas flow has been found to help
exchange heat and moisture with the external environment through
the outlet valve. An increased rate of circulating gas flow can
quickly act to clear droplets of water resulting from condensation
and/or melted frost. Furthermore, the increased workload on the fan
will tend to result in heat dissipation into the heat transfer
cavity that can also contribute to the efficiency of the defrost
mode, helping to dry out the heat transfer cavity. The fan is
preferably in fluid communication with the heat transfer cavity.
Further preferably the fan is waterproof e.g. comprising potted or
coated electronic components so as to be unaffected by moisture
ingest.
[0041] The Applicant has recognised that the design and position of
the outlet valve can be optimised so as to increase the efficiency
of the drying or defrost mode.
[0042] In a preferred set of embodiments the outlet valve comprises
an outlet opening and the heat transfer cavity comprises an outlet
flow path arranged to direct liquid towards the outlet opening.
This can assist in draining larger liquid droplets under gravity.
The outlet flow path may be inclined (e.g. angled or curved) in one
or more directions to ensure that liquid is drained from throughout
the cavity. For example, the outlet flow path may be inclined
downwardly in a radial direction so as to direct liquid towards the
outlet opening. For example, alternatively or additionally, the
outlet flow path may be inclined downwardly in a circumferential
direction so as to direct liquid towards the outlet opening. In a
preferred set of examples, the outlet flow path may provide a
helical incline towards the outlet opening. In other words, the
surface(s) in the heat transfer cavity may be inclined so as to
provide a spiral flow path that directs liquid towards the outlet
opening. This is considered novel and inventive in its own
right.
[0043] According to a fourth aspect of the present invention there
is provided a heat transfer device comprising: a heat exchanger, a
heat transfer cavity and means for creating a circulating gas flow
between the heat exchanger and the heat transfer cavity; a housing
having an opening for allowing an object to be inserted into the
heat transfer cavity; and an outlet valve for exhausting gas and/or
liquid from the heat transfer cavity; wherein the heat transfer
cavity comprises an outlet flow path arranged to direct liquid
towards the outlet valve.
[0044] As is described above, the outlet flow path may be inclined
downwardly in a radial and/or circumferential direction so as to
direct liquid towards the outlet valve under gravity. The outlet
flow path may provide a helical incline towards the outlet valve
e.g. a spiral flow path that directs liquid towards the outlet
valve.
[0045] In addition, or alternatively, in a preferred set of
embodiments the outlet valve comprises an outlet opening that is
directed substantially tangential to the direction of the
circulating gas flow e.g. the outlet opening is directed in the
direction of rotation of the fan. This makes it easier for the
outlet opening to entrain water droplets that are carried by the
circulating gas flow. Any spray that is flung out tangentially by
the fan can be collected effectively to drain through the outlet
opening. The outlet opening may be substantially positioned at a
periphery of the fan. The outlet opening is therefore positioned at
a point of high gas pressure relative to the opening of the heat
transfer cavity, such that, with the outlet valve open and without
a perfect seal at the opening of the heat transfer cavity, the two
internal pressures equilibrate each side of the ambient external
pressure. In other words, the opening to the heat transfer cavity
is at a low pressure part of the air circulation path while the
outlet opening is at a high pressure part. As such, the pressure of
the gas just inside of the opening of the heat transfer cavity is
lower than the ambient pressure so gas is readily drawn into the
heat transfer cavity, and the pressure of the gas just inside the
outlet opening is higher than the ambient external pressure,
causing gas to be readily expelled. A good throughflow of air is
therefore created to assist in driving out moisture and drying out
the cavity. Smaller liquid droplets will readily evaporate in the
circulating gas flow, especially as it is replenished by drier
ambient air.
[0046] The Applicant has found that the outlet opening, and
optionally the outlet flow path, should be unrestrictive to the
throughflow of air. If they are sized too small then boundary
effects can hinder the flow. Preferably the outlet opening has a
cross-sectional area of at least about 50 mm.sup.2. Where provided,
the outlet flow path preferably has a cross-sectional area of at
least about 50 mm.sup.2 along its length. The cross-sectional area
of either, or both, of these is further preferably at least about
100 mm.sup.2, 150 mm.sup.2, 200 mm.sup.2, 250 mm.sup.2, or 300
mm.sup.2. In a preferred set of embodiments the outlet opening has
a cross-sectional area of at least 250 mm.sup.2, and preferably
more than 300 mm.sup.2, so as to dry out a typical heat transfer
cavity for a beer glass in a relatively short period of time e.g.
about 20 minutes (depending on ambient conditions). It will be
appreciated that such an outlet opening is larger than a standard
liquid outlet e.g. provided for drainage purposes without enabling
an air flow. In at least some embodiments, the outlet opening may
have a maximum cross-sectional area of about 0.25 m.sup.2. This
ensures that the heat transfer cavity is not overly open to the
external environment.
[0047] While it is beneficial that the outlet opening does not
unduly restrict air flow, it has been found that liquid droplets
can tend to form around a larger opening and be blown out in all
directions. It is desirable to be able to collect any liquid
droplets that drain through the outlet opening. Thus in a set of
embodiments the device further comprises a funnel arranged adjacent
to the outlet valve to collect liquid. The outlet opening may
extend orthogonally to the funnel, for example, a generally
horizontal outlet opening that directs liquid droplets into a
generally vertical funnel. The outlet opening of the valve may
include a protrusion, e.g. an angled protrusion, that tends to
collect liquid into coalesced droplets. Such a protrusion may be
positioned above the funnel so that liquid droplets are directed
into the funnel. The funnel may have a smaller cross-sectional area
than the outlet opening, especially if the cross-sectional area of
the funnel decreases to a minimum along its length. However, it has
been found that the proximity of the funnel to the outlet opening
means that it can also act to restrict air flow through the outlet
valve if the funnel is too narrow. Preferably the funnel has a
minimum cross-sectional area of at least about 30 mm.sup.2, and
preferably at least about 50 mm.sup.2, so that it does not
negatively affect the time taken to defrost the device. The device
may further comprise a drip tray positioned beneath the funnel,
preferably a removable drip tray. Melt water collected in the drip
tray can be left to evaporate or the drip tray may be emptied by a
user.
[0048] The controller may open the outlet valve in the drying or
"defrost" mode of operation by any suitable means. So as to ensure
that the valve opens reliably regardless of the air pressure in the
heat transfer cavity, the outlet valve may be mechanically opened.
For example, the controller may operate a servo motor or
electromechanical actuator (e.g. solenoid) that moves a cover from
the outlet opening. The cover may be a sealing cover, for example
an elastomeric e.g. silicone flap. The controller may further
operate to close the outlet valve at the end of the defrost mode.
This can help to maintain hygiene by ensuring that the heat
transfer cavity is not left open to the atmosphere after it has
been defrosted. In some examples the end of the defrost mode may be
triggered by a timer. Alternatively, or in addition, in some
examples the end of the defrost mode may be triggered by a
detection signal from a sensor in the heat transfer cavity e.g. a
temperature and/or humidity sensor.
[0049] In various embodiments the heat transfer device is a cooling
device and the heat exchanger is a thermal sink arranged to cool
the circulating gas flow. The heat exchanger may be driven by
movement of a coolant or refrigerant fluid therein.
[0050] There may be times when it is desirable to accelerate the
drying or defrost mode. For example, when operating a cooling
device in a humid climate there may be times during the day when
frost has built up and a quick defrost would be beneficial to
prevent the ice from interfering with performance. In a set of
embodiments the device may further comprise a heater for the heat
transfer cavity. The heater may be operated in the defrost mode so
that any frost is melted more quickly. The heat exchanger may
itself act as a heater, for example by driving the heat exchanger
with a heated fluid rather than a coolant fluid. This may be done
in a standard refrigeration circuit by bypassing hot refrigerant
from the compressor past the condenser. In many parts of the world,
mains power is not available or is subject to unexpected power
cuts. If the power supply to a cooling device is suddenly
interrupted then the heat transfer cavity will be left to warm up
(or cool down) and an unhygienic pool of water is likely to collect
inside. While a user may be alerted to manually open the outlet
valve in such situations, this may not be acted upon. The Applicant
has recognised that the outlet valve may instead be arranged to
automatically drain liquid from the heat transfer cavity e.g. upon
loss of electrical power to the heat exchanger. This is considered
novel and inventive in its own right.
[0051] According to a fifth aspect of the present invention there
is provided a heat transfer device comprising an
electrically-powered heat exchange circuit, comprising a heat
exchanger, a heat transfer cavity and a fan for creating a
circulating gas flow between the heat exchanger and the heat
transfer cavity, wherein the heat transfer cavity includes an
outlet valve for exhausting gas and/or liquid, and wherein the
outlet valve is automatically opened upon loss of electrical power
to the heat exchange circuit.
[0052] Thus in the event that the heat exchanger and/or fan can no
longer operate due to a loss of electrical power, the outlet valve
is automatically opened so that liquid can drain from the heat
transfer cavity as it warms up (or cools down). This means that
user intervention is not required to ensure that the heat transfer
cavity is kept dry and hygienic while the device is out of use.
This aspect of the invention includes a method of drying a heat
transfer device comprising a heat transfer cavity that can receive
an object, the method comprising: creating a circulating gas flow
in a heat transfer cavity that can receive an object; cooling or
heating the circulating gas flow using an electrically-powered heat
exchange circuit; opening an outlet valve to exhaust gas and/or
liquid from the heat transfer cavity upon loss of electrical power
to the heat exchange circuit. The method optionally further
comprises: sensing loss of electrical power to the heat exchange
circuit and actively opening the outlet valve.
[0053] In a set of embodiments the outlet valve may be biased open
but held closed by an electromechanical actuator, for example an
electromagnet or solenoid actuator. The electromechanical actuator
may be connected to the heat exchange circuit so that, when
electrical power is supplied to the circuit, the outlet valve is
held closed. Upon loss of power the circuit is broken and the
electromechanical actuator automatically released so that the valve
is biased open. For example, the outlet valve may comprise an
outlet opening and a spring-biased cover.
[0054] In another set of embodiments the outlet valve may be
actively opened upon loss of electrical power. The device may
include means for monitoring the power supply to the heat exchange
circuit so as to detect when a power cut is happening, e.g. by
detecting a drop in the power supply voltage. The device may
comprise a controller that operates to open the outlet valve in
response to a power cut detection signal. However, active opening
of the outlet valve is likely to require electrical power, e.g. to
drive an electromechanical actuator to uncover the outlet opening
of the valve. In some examples the device may further comprise
means for storing electrical power, such as a capacitor connected
to the outlet valve. In some examples the device may further
comprise means for generating electrical power, such as an electric
brake arranged to convert the kinetic energy of a fan as it slows
down upon power failure. In these embodiments the device can
provide sufficient power to open the outlet valve when a power cut
occurs.
[0055] In various embodiments of a heat transfer device as
described above, the circulating gas flow between the heat
exchanger and the heat transfer cavity is created by a fan,
preferably an electric fan. The Applicant has found that the
performance of an electric fan can be affected by electrostatic
charge separation resulting from the phase changes occurring inside
the heat transfer cavity. Especially where the heat transfer device
is a cooling device, ice crystals that form in the cavity can be
ingested by the fan. It is believed that electrostatic charge
separation may be caused by dry ice crystals having piezoelectric
properties. The circulating gas flow means that ice crystals can
impact the fan at high velocity (e.g. 30-50 mph) and cause a
build-up of charge that may result in arcing to the electrical
components of the fan, for example causing a malfunction of the
electric motor and/or control electronics. In order to mitigate
this risk, charge build-up may be avoided by providing the fan with
rotating components that are electrically insulated, e.g. formed of
plastics material or metallic components having an insulating
surface coating. A preferred solution is for the rotating
components of the electric fan to be grounded. This is considered
novel and inventive in its own right.
[0056] According to a sixth aspect of the present invention there
is provided a heat transfer device comprising: a heat exchanger, a
heat transfer cavity and an electric fan for creating a circulating
gas flow between the heat exchanger and the heat transfer cavity;
the electric fan comprising a rotating arrangement of vanes or
blades mounted on a hub, and an electric motor driving the hub,
wherein the rotating arrangement has an electrical connection to
ground.
[0057] It will be appreciated that providing the rotating
arrangement itself with an electrical connection to ground, in
addition to any earthing of the drive motor, can ensure that static
charge is not allowed to build up on the vanes/blades or hub. This
can be particularly beneficial in examples where the rotating
arrangement is mainly formed of metallic components, as is common.
Such a rotating arrangement may be referred to as an impeller or
rotor.
[0058] Preferably the heat transfer device is a cooling device. The
earthing of the electric fan has been found effective in preventing
charge build-up caused by ice crystals impacting on the rotating
arrangement. In one set of examples the hub is mounted to the motor
by bearings that establish the electrical connection to ground.
Alternatively, a separate electrical connection may be provided. In
various embodiments it is preferable for the electrical connection
to ground to include an impedance, for example a resistor. This has
been found to prevent or reduce EMC emission issues, if electrical
noise is present, by reducing the ability of the fan (especially
the motor hub) to act as an antenna.
[0059] Embodiments of this aspect of the invention may include any
of the aforementioned features. For example, the device may
comprise a controller arranged to operate the electric fan. The
controller may adjust the rate of circulating gas flow created by
the fan in response to one or more signals, e.g. a detection signal
from a sensor when an object is inserted into the heat transfer
cavity (rapid cooling/heating mode), or a defrost signal when the
heat exchanger is turned off (defrost mode).
[0060] There will now be described some further features of a heat
transfer device or cooling device in accordance with embodiments of
any aspect of the invention.
[0061] While the device may be filled with a particular heat
transfer gas, where the housing has an opening to allow an object
to be inserted into the heat transfer cavity there is likely to be
ingress of ambient air. Thus in preferred embodiments the
circulating gas flow may be a circulating air flow. So as to help
maintain the heat transfer cavity in a desired temperature range,
and to avoid changes in moisture content, the opening is preferably
arranged to minimise the entry of ambient air. It is preferable
that there is only one opening into the heat transfer cavity while
the heat exchanger is running. In addition, the opening may be
partially or fully closed by a flexible membrane that is only
pushed aside when an object is inserted through the opening.
Keeping the opening closed when not in use helps pressures to
equilibrate and prevents ambient air from being drawn into the
cavity. In a set of embodiments the flexible membrane comprises a
plurality of flaps extending inwardly from the housing and being
deformable so as to define an aperture through the opening. For
example, the flaps may be formed of a flexible polymeric or
elastomeric material such as silicone. For a circular opening the
flaps may extend radially inwardly. An advantage of such flap
arrangements is that air may be encouraged to flow downwards
through the aperture and down the sides of the object being
inserted, so that any moisture carried by the air is deposited on
surfaces of the object to create a frosted effect. Preferably the
outer surface of the flaps provides a low coefficient of friction,
especially in contact with glass, so that an object can be pushed
through the aperture without gripping. For example, the flaps may
be given a low friction coating e.g. of PTFE, or other low friction
surface finish.
[0062] In the foregoing description it will be appreciated that
what is meant by a circulating gas flow is a mass of gas that is
entrained to flow continuously in a loop between the heat exchanger
and the heat transfer cavity. During use of the device, and
especially when an object is present in the cavity, the circulating
gas flow may comprise a substantially constant mass of gas e.g. air
trapped inside the heat transfer cavity. Of course, the volume of
any mass of gas depends on its temperature. As mentioned above, air
may enter and/or exit through the opening when an object is
inserted therethrough, but preferably the opening is substantially
closed at other times. The housing may also be designed to assist
in keeping the heat transfer cavity cold and dry. In a set of
embodiments the housing comprises a flange extending upwardly
around the opening. This flange can trap a volume of drier air,
which is denser than ambient air, directly above the opening. The
height of such a flange is preferably at least 45 mm.
[0063] A heat transfer device according to any of the aspects or
embodiments of the invention described above may comprise a heat
exchanger comprising a Peltier element, for example providing a
heating or cooling effect dependent on electrical current.
[0064] Additionally or alternatively, the heat transfer device may
comprise a heat exchanger driven by movement of a coolant fluid
therein, i.e. the heat transfer device may be a cooling device. The
coolant fluid may be provided by an on-board refrigerant circuit.
In addition, the heat exchanger may be part of an
electrically-powered heat exchange circuit, and electrical power
may be provided as part of the device. In other words, the cooling
device may be a standalone unit. However, in various embodiments it
is preferable for the cooling device to be compact so that it can
easily be mounted on a bar, table or counter for use. In such
embodiments there may be provided a two-part unit comprising the
cooling device connected to a separate refrigerant device. The
refrigerant device may provide the coolant fluid and/or electrical
power. For example, the refrigerant device may comprise one or more
of: an electrical power supply; a refrigerant circuit; and a
controller for the refrigerant circuit. The refrigerant circuit may
include a condenser and a pump for the coolant fluid.
[0065] A typical refrigerant circuit may comprise a compressor to
pressurise the coolant fluid returning from the cooling device, a
condenser to remove heat from the fluid, and an expansion device to
rapidly cool the fluid before it is supplied to the cooling device.
The expansion device may comprise a thermostatic expansion valve or
a capillary tube. When the expansion device is located in the
refrigerant device, cold fluid travels to the cooling device and
warm fluid returns to the refrigerant device. It is not ideal for
such two-way fluid communication to be carried by the same fluid
line as the returning warm fluid then tends to raise the
temperature of the cold fluid before it reaches the cooling device
and/or because relatively thick insulation may be required. The
Applicant has recognised that cooling efficiency can be improved by
separating the expansion device from the rest of the refrigerant
circuit and locating the expansion device in the cooling device
instead of the refrigerant device. This is considered novel and
inventive in its own right.
[0066] Thus according to a further aspect of the present invention
there is provided a two-part cooling apparatus comprising a cooling
device connected to a separate refrigerant device, wherein the
refrigerant device includes a compressor and a condenser for
coolant fluid supplied to/from the cooling device, and wherein the
cooling device includes an expansion valve. This means that the
coolant fluid is still warm when it is transferred from the
refrigerant device to the cooling device. The connection preferably
provides for two-way transfer of coolant fluid between the
refrigerant device and the cooling device. The coolant fluid
travelling to the cooling device can advantageously transfer some
of its heat to the returning fluid as they pass through the shared
connection. This can improve the efficiency of the overall
refrigerant circuit by lowering the temperature of the coolant
fluid before it reaches the expansion valve. Furthermore,
pre-heating the coolant fluid before it reaches the refrigerant
device can ensure that liquid is not returned to the compressor,
e.g. due to very cold temperatures in the cooling device due to
non-use, protecting the compressor from damage. For example, the
cooling device may be connected to the separate refrigerant device
by an umbilical cord or flexible line that carries the coolant
fluid. A higher average temperature in the umbilical cord can
reduce its insulation requirements, especially when the apparatus
is in a relatively warm ambient environment. As is discussed above,
the refrigerant circuit may be controlled to adjust the speed
and/or temperature of the coolant fluid that is provided to the
cooling device e.g. to drive the heat exchanger at a different heat
transfer rate and switch between peak/off-peak modes of operation.
It is therefore preferable that the controller for the refrigerant
circuit is in communication with any controller in the cooling
device. Detection signals from sensors in the cooling device, for
example an object detection sensor and/or temperature sensor, can
then be passed from the controller for the cooling device to the
controller for the refrigerant circuit as necessary. Such
communication of control signals may be combined with electrical
power being supplied from the refrigerant device to the cooling
device. A two-way electrical cable may be connected between the
refrigerant device and the cooling device. The electrical
connection(s) between the refrigerant device and the cooling device
may be separate from refrigerant lines supplying the coolant fluid
to/from the two devices. However, in a preferred set of embodiments
the two-part unit comprises a cooling device connected to a
separate refrigerant device by an umbilical cord or flexible line
that also provides an electrical connection e.g. both electrical
connection and transfer of a coolant fluid.
[0067] The umbilical cord provides a tidy way to connect the
cooling device to a separate refrigerant device. The two devices
may be permanently connected by the umbilical cord. However, in at
least some embodiment, the umbilical cord includes a separable
connection. This means that the cooling device can be installed
separately from the refrigerant device, and different devices may
be connected together. For example, in a bar environment, a
refrigerant device may be installed more permanently out of view of
customers while one or more bar-top cooling device may be
temporarily installed and connected to the refrigerant device when
required. The separable connection may include a seal for the
coolant fluid, to allow for separation without leakage. So-called
"quick disconnect" couplings may be used. In at least some
embodiments, the separable connection may be poka-yoke i.e.
designed so that it can only be connected the right way round.
[0068] To improve flexibility in the positioning of the cooling
device relative to the refrigerant device, and in routing of the
umbilical, the umbilical cord is preferably connected to the
refrigerant device at an angle of around 45.degree.. This means
that it can readily be bent to extend either horizontally or
vertically towards the cooling device. In various examples, the
umbilical cord may be at least 50 cm, 60 cm, 70 cm, 80 cm, 90 cm or
1 m long. Preferably the umbilical cord is at least 2 m, 3 m, 4 m,
or 5 m long. The umbilical cord may be up to about 10 m long.
[0069] Some embodiments of the present invention will now be
described, by way of example only, and with reference to the
accompanying figures, in which:
[0070] FIG. 1a is a cross-sectional view of a cooling device and
FIG. 1b is a schematic illustration of the circulating airflow in
such a device;
[0071] FIG. 2a is a top view of a sensor arrangement across the
opening of such a cooling device and
[0072] FIG. 2b is a side cross-sectional view of the opening;
[0073] FIG. 3a and FIG. 3b show an infrared sensor arrangement to
detect when a glass is inserted through the opening;
[0074] FIG. 4 shows a black and white image of passive thermal
emission in the far infrared spectrum for a glass inserted through
the opening;
[0075] FIG. 5a and FIG. 5b provide a side sectional view and a
perspective sectional view of a capacitive sensor arrangement;
[0076] FIG. 6 is a side sectional view of a cooling device
including an electrical connection to earth;
[0077] FIG. 7 is a schematic side sectional view of a cooling
device including an outlet valve;
[0078] FIG. 8 is a top view of an outlet flow path in the base of
the heat transfer cavity of a cooling device;
[0079] FIGS. 9a-9c provide perspective and side sectional views of
the outlet valve in the base of a heat transfer cavity;
[0080] FIG. 10 is a side sectional view of a counter-top cooling
device;
[0081] FIGS. 11a and 11b provide schematic side views of a
counter-top cooling device connected to a refrigerant device by an
umbilical cord; and
[0082] FIG. 12 provides a schematic overview of the components in a
cooling device connected to a separate refrigerant device.
[0083] There is seen in FIG. 1a an exemplary cooling device 2 that
may be used to chill and frost a beer glass 4 inserted into a heat
transfer cavity 6 of the device 2. The heat transfer cavity 6 is
defined by a double-walled, cylindrical ducting member 8 that is
shaped to receive an inverted beer glass 4. The ducting member 8
may be removable and optionally interchangeable, for example to
allow for different sizes and shapes of beer glass 4 to be
positioned in the heat transfer cavity 6. Surrounding the ducting
member 8 is a heat exchanger 10 in the form of a set of coils. In
this example, the heat exchanger 10 is a heat sink comprising
multiple copper coils that are cooled by a refrigerant fluid pumped
there through. A fan 12 is positioned below the ducting member 8
and heat exchanger 10 so as to create a circulating airflow in the
heat transfer cavity 6. The schematic inset of FIG. 1b illustrates
how air, or any other gas inside heat transfer cavity 6, is
circulated by the fan 12. As is described in WO 2011/042698, the
ducting member 8 is shaped as a pseudo-negative of the glass 4 to
be cooled such that there is a specified gap between the ducting 8
and the glass 4 that promotes turbulence in the airflow. When the
fan 12 is operated at high speed, the circulating airflow is highly
turbulent and this generates a high heat transfer coefficient so as
to achieve rapid cooling. As seen in FIG. 1b, the airflow is drawn
out of the heat transfer cavity 6 by the fan 12 at (1), driven
across the coils of the heat exchanger 10 at (2) and circulated
around the ducting member 8 at (3), with a restricted region
between the glass 4 and the ducting member 8 acting to accelerate
the airflow and create turbulence for optimal heat transfer with
the glass at (4).
[0084] The cooling device 2 includes an outer housing defining an
opening 14 that allows the glass 4 or other object to be inserted
into the heat transfer cavity 6. The opening 14 may be closed by a
flexible membrane 16 or other seal so as to help retain the cold
air inside the heat transfer cavity 6. The housing provides a
flange 17 extending circumferentially around the opening 14 and
extending for a height above the opening. It has been found
beneficial to make the flange at least 45 mm high. This helps to
trap a static volume of air above the opening 14, which may be
cooler than ambient and hence denser. The flange 17 surrounds the
protruding base of a glass 4 while it is being frosted.
[0085] Various embodiments of such a cooling device will now be
described with reference to the subsequent figures. Although the
object inserted into the heat transfer cavity is described as a
glass, it will be appreciated that other objects may of course be
cooled instead. Furthermore, the heat exchanger may take the form
of a thermal sink or thermal source and, in the latter case, the
heat transfer cavity may be arranged to warm rather than cool an
object inserted therein.
[0086] There is seen in FIGS. 2-5 some non-contact sensor
arrangements for detecting when a glass is inserted into the heat
transfer cavity of a cooling device. In the example of FIGS. 2a and
2b, an active radiation sensor arrangement is used to detect when a
glass 4 is inserted through an opening 14 in the upper part of the
heat transfer cavity 6. It may be seen with reference to FIG. 1a
that the opening 14 is generally closed by a flexible membrane 16
that can be deformed so as to allow a glass 4 to be pushed through
the opening 14 and down into the heat transfer cavity 6. The top
view of FIG. 2a shows a flexible membrane 16 that is split into
radial flaps providing a flexible seal around the glass 4. The
flaps bend against the glass 4 when it is inserted, to provide an
intimate seal and encouraging any air that is pulled into the heat
transfer cavity 6 to curve down the sides of the glass 4. Once
positioned in the heat transfer cavity 6, an upper end of the glass
4 protrudes above the opening 14 so as to enable the user to grip
the glass when it is ready to be removed. The protruding base of
the glass 4 is detected by a light gate arrangement indicated
generally by 18 in FIGS. 2a and 2b. The light gate 18 is defined
between an infrared light emitting diode (LED) 20 and a photodiode
22 arranged non-diametrically opposite the LED 20. The LED emitter
20 and photodiode receiver 22 may be filtered so as to be sensitive
to the same wavelength range.
[0087] It can be seen from FIGS. 2a and 2b that the emitter/ray
receiver pair 20, 22 and light gate 18 therebetween is offset by a
distance 24 to one side of the centre of the glass 4, e.g. offset
by 10 mm. The emitter/receiver pair 20, 22 is positioned so that
the light gate 18 is at the same height as the thickened base of
the glass 4. Lenses 26 that are clear to infrared light can be used
to hide the emitter 20 and receiver 22 and protect them from frost
growth. For each sensor reading, a controller turns the LED emitter
20 on and off 50 times and converts a detection signal from the
receiver 22 at each step by a 10-bit ADC to eliminate ambient
infrared from the reading. The on and off values are summed
separately, and the off total is subtracted from the on total. It
has been found that such an infrared sensor arrangement works best
with a narrow beam LED with a half angle of 20.degree. or less. For
example, the emitter 20 may be an 8.degree. half angle LED, for
which typical sensor reading values are 3,000-4,000 without a glass
present and 200-300 with a glass present, giving at least a 10:1
ratio, which allows a simple threshold for the detection signal to
determine whether a glass 4 is present or not.
[0088] Another non-contact sensor arrangement is seen in FIGS. 3
and 4. This arrangement uses passive thermal emission in the far
infrared spectrum to detect an ambient temperature glass 4 that is
inserted through an aperture defined by the flexible membrane 16.
As seen in FIGS. 3a and 3b, a far-infrared (FIR) thermopile sensor
28 is positioned to point down at an angle through the opening to
the cold heat transfer cavity inside the device. The field of view
30 of the sensor 28 includes the less cold aperture seal 16 as well
as the aperture itself. When a glass 4 is inserted (FIG. 3b), much
of the field of view 30 is filled by the base of the glass 4, which
is at ambient temperature. The thermal emission image shown in FIG.
4 shows that the ambient temperature glass 4 is clearly visible
against the cold aperture and aperture seal 16. While typical
temperatures sensed for the aperture may be -15.degree. to
-35.degree., the ambient temperature glass 4 gives about 40.degree.
C. swing in reading.
[0089] Another non-contact sensor arrangement is seen in FIGS. 5a
and 5b. In this example the presence of a glass 4 in the heat
transfer cavity 6 is detected by measuring changes in capacitance.
Glass in particular provides for good detectability in air because
it has a relative permittivity of between around 4 and 10. In this
capacitive sensor arrangement, electrodes 32, 34 are arranged in
the heat transfer cavity 6 on either side of the ducting member 8,
so that an inner electrode 32 is positioned inside the inserted
glass 4 and an outer electrode 34 is positioned outside the glass
4. To eliminate sensitivity to local ice build-up and improve glass
protection capability, concentric annular (e.g.
cylindrical/frustoconical) electrodes 32, 34 are used to increase
surface area. Such an arrangement is less proximity-dependent so
that the build-up of a thin ice or frost layer on the surfaces of
the glass 4 does not affect sensor readings. It has been found that
good glass detection sensitivity can be achieved with an electrode
separation of several centimetres, even with two layers of plastic
ducting member 8 in series. The electrodes 32, 34 may be provided
as annular plates, or may take the form of conductive coatings
applied to the plastic ducting member 8 or other suitable surfaces
inside the housing of the device 2. Conductive paint (such as that
used for EMC shielding), printed conductive tracks and chromed
finishes are all appropriate methods of achieving sufficiently
effective electrodes 32, 34. If the ducting member 8 carried the
electrodes 32, 34 and it is removable, then a separable electrical
connection may be required. As is seen most clearly from FIG. 5b,
the ducting member 8 may be removably positioned over an inner
moulding 36 that carries the capacitive sensing electrodes 32, 34.
The inner moulding 36 may be permanently positioned inside the
device housing. The inner moulding 36 includes an inner tube 38
that runs up the inside of the ducting member 8 to prevent fingers
from reaching the fan (not shown) when the ducting member 8 is
removed. The inner tube 38 is an ideal part to apply a coating for
the inner electrode 32 so that it penetrates deep inside the glass
4 without any need for an electrical connection to the ducting
member 8. The outer electrode 34 may be fitted inside the moulding
36, or alternatively a coating can be applied to an inner surface
of the cylindrical moulding 36.
[0090] FIG. 6 provides a side sectional view similar to that seen
in FIG. 1a, except that details of the fan 12 are visible. It can
be seen that the electric fan 12 comprises a rotating arrangement
of vanes or blades mounted on a hub 40. The hub 40 is driven by a
rotating drive shaft 42 with bearings 44 arranged therebetween. The
shaft 42 extends from a fan base 46 that has an electrical
connection to ground 48. An impedance 50 may optionally be added to
the grounding line so as to prevent any EMC emissions if electrical
noise is present, by reducing the ability of the hub 40 to act as
an antenna. It has been found that there may be sufficient
electrical conduction through the bearings 44 that connect the fan
base 46 to the hub 40, but other connection methods are also
possible. Earthing of the fan hub 40 means that a metallic hub can
be used instead of a plastic hub. It has been found that when ice
crystals are ingested into the fan 12 it can cause a malfunction.
This is often only momentary, but occasionally terminal for the fan
motor and its control board. The cause of this malfunction is
believed to be electrostatic charge separation seemingly caused by
the high velocity (e.g. 30-50 mph) impact of ice crystals onto the
fan hub 40, as generally indicated by the arrows in FIG. 6. It
seems that sufficient charge may build up on the hub 40 to cause an
electrical arc to the fan motor or drive electronics below,
affecting operation of the fan controller.
[0091] Any of the non-contact sensor arrangements described above
may be used, alone or in combination, to detect when an object such
as a glass is inserted into the heat transfer cavity of a cooling
device. A controller connected to the fan may then adjust the rate
of circulating airflow in response to a detection signal from the
sensor arrangement. Insertion of a glass or other object may
trigger a rapid cooling mode in which the fan speed is increased.
Readings from the sensor arrangement may also be used by the
controller to decide when to switch the cooling device between peak
and off-peak modes of operation, for example when it is determined
that the cooling device has not been used for a certain period of
time.
[0092] In addition to the modes of operation mentioned above, the
cooling device may be operated in a defrost mode where the heat
exchanger 10 is turned off and the heat transfer cavity 6 is
allowed to defrost. As in seen in the schematic of FIG. 7, the heat
transfer cavity 6 may be provided with an outlet valve 52 that
enables fluid to leave the heat transfer cavity 6, for example to
drain water produced during defrost. During a defrost mode of
operation, the flow of refrigerant through the heat exchanger 10
may be stopped so that the coils begin to warm up under the thermal
load. The fan 12 may be turned on to full power so as to circulate
the air as it warms up and assist in drying out the heat transfer
cavity 6. When the defrost mode is activated, the outlet valve 52
may be opened so that air is pulled through the heat exchange
cavity 6 and liquid can drain out. As indicated by arrow 54,
ambient air may be drawn in through the upper opening 14 and the
circulating air movement helps to exchange heat and moisture with
the outside world through the venting flow 55 provided by the
outlet valve 52. The high air speed created by the fan 12 can act
to quickly clear droplets of water created from condensation and
melted frost. In addition, the increase in power dissipated by the
fan 12 can help to warm up the inside of the cooling device 2,
helping to melt and evaporate frost and increasing the capacity of
the airflow to carry water vapour. The fan 12 may include potted or
coated electronics so as to be unaffected by moisture ingress.
[0093] The flow path to the outlet vent 52 and its position will
now be described in more detail with reference to FIGS. 8 and 9. As
seen from the top view of FIG. 8, the heat transfer cavity includes
an exit 56 to the outlet valve 52 is at a point near the periphery
of the fan 12. The flow path indicated by the arrows 60 is arranged
to run towards the exit 56 tangential to the direction of rotation
58 of the fan 12. This point in the air circuit is at relatively
high pressure, whereas the opening 14 is at relatively low
pressure, and so ambient air is drawn in through the top of the
heat transfer cavity 6 and ejected through the outlet vent 52. The
position of the exit 56, outside the fan 12 and angled
tangentially, not only benefits the air pressure
recovery--encouraging good flow--but also allows spray that is
flung tangentially from the fan 12 to be collected effectively.
Furthermore, the floor of the heat transfer cavity 6 around the fan
12 may slope downwards towards the exit 56 in the general direction
of air flow, allowing water collected in the bottom of the cavity 6
to drain out through the vent 52. The arrows 60 in FIG. 8 indicate
how the floor of the heat transfer cavity 6 slopes continually
downwards towards the exit 56. Furthermore, the arrows 62 and 64
indicate how the floor of the heat transfer cavity 6 may be
inclined in a radial direction, on both sides, so that liquid runs
down onto the outlet flow path 60, which is then sloped downwardly
in a circumferential direction towards the exit 56. In other words,
the base of the heat transfer cavity 6 may be designed to provide a
helical flow path that collects and drains liquid towards the exit
56.
[0094] The outlet valve 52 is seen in more detail in FIGS. 9a-9c.
The outlet valve 52 comprises an outlet opening 66 leading out
horizontally from the exit 56. A movable cover 68 is operated by a
servo motor 70. The opening 66 is positioned above a funnel 72
designed to catch droplets of liquid as they drip out of the
opening 66, which is provided with a pointed protrusion 74 that
encourages any droplets remaining attached to collect directly into
the funnel 72. The funnel 72 narrows to an exit tube 76 which is
designed not to restrict airflow out of the valve 52 by having
internal dimensions of 12.5 mm by 9 mm (95.1 mm.sup.2). The tube 76
passes through the bottom of the housing of the cooling device 2 so
as to direct liquid into an external drip tray 78. As is seen in
the cross-sectional view of FIG. 9b, the exit tube 76 has a pointed
end 80 to clear drips more effectively. Melt water collected in the
drip tray 78 can be left to evaporate or may be emptied out. The
drip tray 78 may be removable for this purpose. It has been found
that the exit opening 66 should ideally provide an unrestricted
airflow path to promote circulation and dry out the heat transfer
cavity quickly. For acceptable defrosting times, e.g. about 20
minutes (depending on ambient conditions), the exit 56 and flow
path to the opening 66 may be made larger than 50 mm.sup.2 in
cross-section along its length. The entire exit path may be more
than 300 mm.sup.2 to provide for effective drying in a relatively
short time period. The opening 66 may be a tube having an internal
diameter of about 18.5 mm. From the cross-sectional view of FIG. 9c
it can be seen how the opening 66 is at the end of a tube that
extends generally horizontally through the housing from a periphery
of the fan 12. Furthermore, comparing the left and right sides in
FIG. 9c, it can be seen that the base 7 of the heat transfer cavity
starts higher on the left side and then spirals downwardly, around
the outside of the fan 12, to reach a low point at the exit 56 to
the outlet opening 66.
[0095] The servo motor 7 operates to open the outlet valve 52
whenever the cooling device 2 enters a defrost mode. In addition,
the device 2 may be designed to automatically enter a defrost mode
in the event of a power cut. It is important that the glass froster
i.e. cooling device 2 is able to drain if affected by a power cut,
to avoid an unhygienic pool of water being trapped in the bottom of
the device as it warms up. While it is not possible to operate the
fan 12 to assist in defrosting without power, sufficient energy can
be stored to open the outlet vent 52 just as the power is cut off,
at least enabling the unit to drain. The controller may include an
extra capacitance to store energy powering the logic and servo
motor 70, as well as means of detecting a drop in the supply
voltage. In an alternative system, the motor of the fan 12 may be
turned into a generator by electric braking, thereby converting the
remaining kinetic energy of the spinning fan into power to operate
the motor 70 and open the vent 52. In some examples, the servo
motor 70 may be replaced by a solenoid actuator with the cover 68
being sprung open but held closed by an electromagnet, such that
when necessary, or when the power supply is cut, the electromagnet
releases the spring and the cover 68 is opened.
[0096] FIG. 10 shows the cooling device 2 in the form of a
countertop or bar top unit including an on-board controller 82 and
a clamp 84 to mount the unit to a counter surface. An umbilical
cord 86 is used to transfer refrigerant fluid and power to the
cooling device 2. FIGS. 11a and 11b illustrate how the umbilical
cord 86 may be connected to a separate refrigerant device 88 at 45
degrees, such that it can be bent either to lead vertically upwards
or horizontally. A reversible cover plate 90 can then be attached
in one of two orientations, depending on the direction of umbilical
cord 86 that is required to fit different countertop
arrangements.
[0097] Finally, it is seen with reference to FIG. 12 how the
umbilical cord 86 may transfer coolant fluid e.g. refrigerant
between the refrigerant device 88 and the bar top cooling device 2,
as well as relaying control signals 92 and providing an electrical
power supply 94. The cooler device 2 includes heat exchanger coils
10, fan 12, defrost valve 56, controller (e.g. PCB) 82, temperature
sensor 96, glass detection sensor 98, display 100 and control
interface 102. The refrigerant device 88 includes a mains power
cable 104, a DC power supply 106 for the cooling device 2, a fridge
control relay 108 and a condensing unit 110. Signals from the
controller 82 in the cooling device 2 may be transmitted to the
fridge control relay 108 so as to determine when the apparatus is
operating in peak or off-peak mode. Any suitable coolant fluid may
be used, for example a refrigerant such as R404A.
[0098] In peak mode, the condensing unit 110 may be constantly
running and the sensor 96 used to monitor the temperature inside
the cooling device 2 so as to maintain the heat transfer cavity in
a desired temperature range e.g. -35.degree. C. to -45.degree. C.
In off-peak mode, the heat transfer cavity may be maintained at a
higher temperature by turning off the condensing unit 110 for some
of the time, e.g. maintaining the cooling device in the temperature
range of -25.degree. C. to -35.degree. C. Periodically turning off
the condensing unit 110 results in a lower average heat transfer
rate in the off-peak mode. The compressor in a typical condensing
unit 110 cannot be turned back on for one minute (or more) after
being turned off due to the back pressure, meaning there could be a
significant rise in internal temperature of the cooling device 2.
This would affect peak throughput, as the extra load of cooling
glasses would worsen the rise while the compressor needs to stay
off. In the off-peak mode, however, by not needing to frost a glass
as quickly, such a temperature rise would be acceptable, so cycling
the fridge compressor on and off is an effective way of lowering
the power consumption significantly.
[0099] The higher internal temperature in the off-peak mode may be
compensated by an increase in the time spent frosting a glass,
which would be less significant to performance during off-peak
times of use. The controllers 82, 108 may respond to glass
detection signals from the sensor 98 to provide a faster cool down
reaction to increased loads, e.g. frosting of multiple glasses in a
series. This may be in addition to the controller 82 increasing the
speed of the fan 12 when the glass sensor 98 provides a detection
signal that causes the cooling device 2 to switch into rapid
cooling mode. The system may include a time delay before switching
into off-peak mode, to avoid cycling the condensing unit 110
(especially the compressor) too often, to prevent damage or
excessive wear. If the condensing unit 110 was turned off more than
e.g. two minutes ago, then inserting a glass may make it turn back
on automatically. When responding to an inserted glass in off-peak
mode, the rate at which the internal thermal mass warms will
increase under the load of frosting a glass, but there will be a
delay before this is detected by temperature measurement. Therefore
turning on the condensing unit 110 when the glass is inserted can
improve performance.
[0100] The fridge condensing unit 110 in the refrigerant device 88
may include, as is conventional, a compressor to pressurise the
coolant fluid e.g. refrigerant returning from the cooling device 2,
a condenser to remove heat from the fluid, and an expansion device
to rapidly cool the fluid before it is supplied back to the cooling
device 2. However, there is envisaged an embodiment in which the
expansion valve is instead provided within the cooling device 2, so
that warmer refrigerant is transferred from the refrigerant device
88 to the cooling device 2 via the umbilical cord 86. The umbilical
cord 86 may then allow for energy regeneration, hot refrigerant
flowing out transferring heat to the cold refrigerant returning.
Additionally, the higher average temperature in the umbilical cord
86 may mean reduced heat gain through its insulation or even a
reduced thickness of insulation required. The umbilical cord 86 may
be a flexible tube containing cables to transfer power and control,
and hoses to transfer refrigerant fluid between the refrigerant
device 88 and the bar top glass froster 2. The umbilical cord 86
may have a quick disconnect on the hoses, as well as a separable
electrical connector. This may make installation considerably
easier, as the two parts of the system can be installed separately.
To ensure correct connection, these connectors may be designed
poka-yoke by having one female and one male connector on the
umbilical and one of each to match on the refrigerant device 88,
such that they cannot be connected the wrong way round.
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