GB2569131A

GB2569131A - Heat transfer apparatus

Info

Publication number: GB2569131A
Application number: GB1720308.4A
Authority: GB
Inventors: Christopher Bertram-Gregory Robin; Andrew Powell Stephen
Original assignee: E Chill Ltd
Current assignee: E-CHILL LIMITED
Priority date: 2017-12-05
Filing date: 2017-12-05
Publication date: 2019-06-12
Anticipated expiration: 2037-12-05
Also published as: GB201720308D0; GB2569131A8; GB2569131B

Abstract

A heat transfer apparatus 10, possibly for use with a device for heating/cooling a beverage or for cooling mains water, comprises a primary and at least one secondary heat exchanger 11, 12a, 12b having respective primary and secondary circuits 14,15 for conducting fluid on a circulatory path therethrough, each circuit having a thermal transfer zone in which heat can be taken up by or discharged from fluid in the circuit after departure from and prior to entry into the corresponding heat exchanger. The apparatus further comprises at least one thermoelectric cooler 13a, 13b, which may comprise a Peltier element, arranged between the heat exchangers to cool one while heating the other. The primary circuit thermal transfer zone is formed by a reservoir 16 for a body of primary circuit fluid and a conduit 17 conducting a use fluid such as water or a beverage, the conduit being substantially immersed in the body of fluid so that the use fluid takes heat from or delivers heat to the body of fluid. Separation of the use fluid cooling zone 16 from the heat exchangers may result in a more compact device than the prior art.

Description

HEAT TRANSFER APPARATUS

The present invention relates to heat transfer apparatus for fluids, particularly apparatus of a kind suitable for cooling or heating liquids such as beverages.

Known heat transfer apparatus for fluids include air conditioning installations, refrigerating equipment and other heating and/or cooling systems for various purposes. Such apparatus generally employ heat exchangers of one kind or another and sometimes, in addition, thermoelectric heat transfer devices or coolers operating on the basis of Peltier effect. As is well-known, a thermoelectric device or cooler (called cooler for convenience, but also intended as a heater in some applications) is responsive to an applied voltage to produce a thermal gradient between two opposite sides, commonly termed a hot side and a cold side. Thermoelectric coolers can be small in size, but have a relatively limited heat transfer capability by themselves, for which reason it is often appropriate to combine them with one or more heat exchangers.

Heat transfer apparatus employing such a combination of one or more thermoelectric coolers and one or more heat exchangers have been devised for a variety of uses in the prior art, such as cooling or heating water or beverages or conditioning air. Examples of prior art heat transfer apparatus employing such a combination are disclosed in GB 2 322 732, EP 1 684 031, EP 2 505 393, WO 2016/012521, US 2008/0209913 and US 2012/004911. Common to these prior art apparatus is a relatively bulky construction of the apparatus, particularly as a consequence of the feed of a liquid or gaseous fluid - to or from which heat is to be transferred - directly through a heat exchanger thermally interacting with a thermoelectric cooler. In order to achieve cooling or heating of a useful volume of fluid on the basis of a sufficient dwell time in the region of heat transfer the heat exchanger has to be relatively large or at least larger than might be desirable in certain applications (cf. GB 2 322 732). In some cases a very small volume of fluid to be heated or cooled may be acceptable, but in other applications, for example in the cooling of drinking water or beverages, a reasonable volume of fluid has to be cooled or heated and this then brings the penalty of larger, more costly and potentially less thermally efficient heat transfer apparatus.

It is therefore the principal object of the present invention to create heat transfer apparatus which by virtue of its design can offer good thermal efficiency in conjunction with a compact size.

A subsidiary object is provision of such apparatus in a form particularly suitable, in terms of size and operating cost, for processing relatively small volumes of fluid, for example 20 to 40 litres per day.

Other objects and advantages will be apparent from the following description.

According to the present invention there is provided heat transfer apparatus for fluids, comprising a heat exchange unit which comprises a primary heat exchanger, a secondary heat exchanger and a thermoelectric cooler arranged therebetween and operable to heat one of the exchangers while cooling the other one of the exchangers, a primary circuit for conducting fluid on a circulatory path through the primary heat exchanger and a secondary circuit for conducting fluid on a circulatory path through the secondary heat exchanger, each circuit having a thermal transfer zone in which heat can be taken up by or discharged from fluid in that circuit after departure from and prior to entry into the respective heat exchanger, wherein the thermal transfer zone of the primary circuit is formed by a reservoir for a body of fluid in the primary circuit and a conduit arranged in the reservoir to, in use, be substantially immersed in such body of fluid and to conduct a volume of a use fluid for taking up heat from or delivering heat to the body of fluid.

Such heat transfer apparatus has the advantage, by virtue of its configuration, of a high level of thermal transfer efficiency allied with a compact size and economic construction. In departure from prior art systems in which a primary heat exchanger conducts a use fluid and thus has to be of a substantial size in order to hold a meaningful volume of that fluid, in the apparatus of the present invention thermal efficiency is achieved by use of a heat exchange unit incorporating primary and secondary heat exchangers and a thermoelectric cooler and a third heat exchanger utilising the thermal output of the primary heat exchangers to heat or cool the use fluid. The heat exchange unit of the primary and second heat exchangers and thermoelectric cooler can then be a relatively small module composed of economic proprietary components, but offering high thermal efficiency by virtue of the Peltier principle employed by the thermoelectric cooler in conjunction with two heat exchangers exploiting the heat gradient of the cooler. The thermal transfer zone of the primary circuit is provided by a suitably larger size reservoir accommodating a conduit for conducting a volume of the use fluid. The volume of the use fluid, for example half a litre, able to be held in the conduit and the flow rate, whether provided by gravity or by forced propulsion, in the conduit can be selected by design, adjustment and/or control so that there is sufficient dwell time of the use fluid in the body of primary circuit fluid for the purpose of appropriate heat exchange between the two fluids. This heat exchange takes place separately from the heat exchange taking place in the heat exchange unit of the primary and secondary heat exchangers and thermoelectric cooler. The size of the reservoir and capacity of the conduit on the one hand and the size of the heat exchanger unit on the other hand can be separate design considerations without the interdependency characterising the prior art systems. Consequently, the thermal efficiency, size and cost of the heat exchanger unit do not have to be compromised by considerations relating to the actual heat exchange, which is now performed by a further heat exchanger employing a reservoir, with the use fluid.

In the present invention the fluids concerned can be liquids, gases or a combination of the two. Typically the primary and secondary circuits will carry the same fluid, for example water with an inhibitor, and the use fluid can be, for example, a beverage or mains water.

For preference, operation of the thermoelectric cooler is reversible to reverse the sense of heating and cooling of the heat exchangers. Reversal of operation can be achieved simply by reversal of the polarity of operating current, which is generally direct current, applied to the cooler. Consequently, in the heat transfer zone of the primary circuit the use fluid can be heated or cooled depending on the mode of operation of the cooler. In the case of a beverage such as beer, cooling is generally desired before dispensing, but with certain beers it is necessary to store the product at temperature lower than desirable for consumption and in those circumstances the beer may be heated rather than cooled in the transfer zone.

In a more developed form of the apparatus the heat exchange unit comprises a further such secondary heat exchanger and a further such thermoelectric cooler arranged between the primary heat exchanger and the further secondary heat exchanger, the thermoelectric coolers being operable in the same sense so as to both heat or both cool the primary heat exchanger. This configuration can be created with little increase in size of the heat exchange unit in relation to the overall size of the apparatus, of which the reservoir may be the largest individual component. The further secondary heat exchanger and further thermoelectric cooler can be readily integrated in the heat exchange unit and the secondary circuit with little more than, for example, a small amount of additional pipework and electrical feeds, in return for a significantly increased thermal transfer capability between the primary and secondary circuits.

With respect to thermal efficiency within the heat exchange unit it is of particular advantage if the or each thermoelectric cooler is in pressurable contact with the heat exchangers between which it is arranged. This optimises heat transfer between the cooler or coolers and the exchangers and is important in the context of compact apparatus in order to minimise or substantially eliminate transfer loss. The pressurable contact can in that case be provided by a plurality of spring clips resiliently deformable to accommodate expansion and contraction of the thermoelectric cooler or coolers, which avoids or helps avoid generation of stress in the module formed by the cooler/exchanger composite subjected to a clamping pressure.

The or each thermoelectric cooler preferably comprises at least one Peltier element, which can be readily procured as an off-the-shelf proprietary component and thus contributes to cost minimisation. However, in order to improve thermal efficiency, particularly in relation to proprietary elements, the or each element is preferably sealed against ingress of external moisture, i.e. humidity. The sealing can be provided by a sealing compound, which can be applied to penetrate into any gaps in the external faces of the element and provide a seal relative to the environment.

With advantage, the thermal transfer zone of the secondary circuit comprises a radiator for delivery of heat to or taking heat from the ambient atmosphere. This represents a simple, but effective means of cooling or heating the fluid of the secondary circuit at a location away from the secondary heat exchanger or exchangers. In that case it is advantageous to provide an impeller, such as a fan, for impelling air towards or away from the radiator so that the transfer performance of the radiator is enhanced.

The apparatus preferably includes controllable propulsion means for propelling fluid around either or each of the primary and secondary circuits so that the fluid can be moved at a defined or definable, particularly variable, rate around the primary circuit, the secondary circuit or both. Control of the propulsion means can be in the form of activating and deactivating the propulsion means, i.e. switching on and off, and/or varying the speed of operation, thus providing a variable flow rate. For preference the propulsion means is activatable to propel fluid whenever the or each thermoelectric cooler is in operation, so that overheating or chilling of the cooler or coolers is avoided. The propulsion means preferably comprises a respective pump in each of the circuits, which enables fluid propulsion in the two circuits to be achieved in simple manner by separate components. It is then particularly advantageous if the pump in the primary circuit is located in the reservoir thereof, in which case the pump intake can be positioned near the base of the reservoir to induct fluid at a point where motion may be advantageous in order to agitate the fluid. In fact, it is advantageous to provide agitating means, for example several small pumps, in the reservoir so as to agitate the body of fluid to achieve a substantially uniform temperature. This ensures a more consistent heat transfer between the body of fluid of the primary circuit and the use fluid in the conduit.

For preference, the conduit defines a coil with multiple turns, which means that a significant volume of the use fluid can be retained in the conduit for the purpose of heating or cooling. Advantageously, the conduit has connection means for connection of the conduit at one end with storage means for a use fluid to be heated or cooled and at the other end with a dispenser for dispensing a use fluid after heating or cooling thereof. The heat transfer apparatus can in that case be installed in simple manner between a storage vessel or cask and a dispenser such as a tap.

With respect to use of the heat transfer apparatus it is particularly advantageous if the circuits are interconnected by way of openable and closable valve means. Although the two circuits are intended to function, in terms of fluid flow, independently of one another the provision of a valve-controlled connection between the circuits offers various possibilities for enhanced operation of the apparatus. Thus, in one such case the valve means can be selectably openable to place the primary circuit and secondary circuit in flow communication for at least one of the purposes of filling the secondary circuit with fluid from the primary circuit and deaeration of the secondary circuit by way of the primary circuit. This provides a particularly simple method of filling the secondary circuit, thus via the primary circuit, and/or of deaerating the secondary circuit, in the latter instance via, for example, a further connection of the two circuits which is inactive except for deaeration purposes. In another such case, the valve means can be selectably openable to place the primary circuit and secondary circuit in flow communication for transfer of fluid therebetween to influence the temperature of fluid in the secondary circuit and thereby the temperature of the or each thermoelectric cooler. This provides a simple, but effective measure for temperature control of the thermoelectric cooler or coolers, especially to avoid overheating in operation. In that respect the apparatus can comprise detecting means for detecting at least one of the temperature at the primary heat exchanger and the temperature at the or at least one secondary heat exchanger and means for controlling the opening and closing of the valve means in dependence on that detected temperature or those detected temperatures. Thus, the temperature of the thermoelectric cooler or cooler can be indirectly monitored and action taken, if an excessive temperature is reached or approached, to divert cooling water from the primary circuit into the secondary circuit to reduce that temperature. The same action can be taken in a reverse sense, i.e. if the cooler or coolers is or are at risk of chilling.

In a wider control sense the apparatus can comprise detecting means for detecting the temperature of the body of the primary circuit fluid and means for controlling operation of the thermoelectric cooler or coolers in dependence on that detected temperature. A temperature-based control of the operation of the heat transfer apparatus offers a substantial degree of flexibility in the heating or cooling of the use fluid. In an extension of that control, the means for controlling the thermoelectric cooler operation can be arranged to compare the detected temperature of the body of fluid with a target temperature and to vary at least one of the thermal output of the cooler or coolers and a rate of movement of fluid in either or each of the primary circuit and secondary circuit so as to substantially maintain the temperature of the fluid body at the target temperature. This ensures a consistent transfer of heat between the fluid body and the use fluid.

The invention further relates to a device for heating or cooling a beverage, comprising apparatus as disclosed in the foregoing, beverage storage means connected with one end of the conduit and a dispenser connected with the other end of the conduit. Such a device has the advantage that since the heat transfer apparatus can be of relatively small size the device as a whole does not have to be much larger than the size of the storage means. The heat transfer apparatus can, for example, be accommodated on a shelf or under a counter and linked by a pipe to remotely positioned storage means.

Alternatively, the device can comprise, instead of such storage means, a water mains pipe connected with one of the conduits so that a supply of cooled drinking water can be provided.

A preferred embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic circuit diagram of a beverage cooling and/or heating device incorporating heat transfer apparatus embodying the present invention;

Fig. 2 is a diagrammatic side view of the heat transfer apparatus; and

Fig. 3 is a diagrammatic front view of the heat transfer apparatus.

Referring now to the drawings there is shown a beverage cooling and/or heating device used primarily for cooling a stored beverage such as a fruit juice or beer. However, the same device can be used for heating, particularly warming, a beverage or also - subject to use of appropriate connections - cooling or warming mains water. The specific use of the device is therefore adaptable to different requirements and use as a beverage cooling device, as described in the following, is merely exemplifying.

The significant functional part of the beverage cooling and/or heating device is heat transfer apparatus 10 for fluids, of which the core component is a heat exchange unit composed of a primary heat exchanger 11, two secondary heat exchangers 12a and 12b respectively arranged on either one of the two opposite sides of the primary heat exchanger 11 and a respective thermoelectric cooler 13a or 13b arranged between the primary heat exchanger 11 and each of the secondary heat exchangers 12a and 12b. The heat exchangers 11, 12a and 12b are proprietary components of compact size each with an internal labyrinthine flow passage for a fluid - possibly gas such as carbon dioxide, but in this embodiment a liquid, preferably water with a corrosion inhibiting additive - and each having an inlet and an outlet, for example in the form of stub pipes. Although the inlet and outlet of each heat exchanger are shown, for ease of understanding, in Fig. 1 at opposite ends of the heat exchanger both are preferably at the same end, which simplifies the making of connections.

Each thermoelectric cooler 13a, 13b consists of at least one Peltier element, in the illustrated embodiment two such elements. These are again proprietary components of compact size. The function of each thermoelectric cooler is as described in the introduction, namely to generate, under applied voltage, a thermal gradient between two opposite sides of the cooler. The sense of the gradient is reversible by change in the polarity of the applied voltage. In the illustrated embodiment, each cooler is intended to be operated so that the gradient has the sense of a colder side at the primary heat exchanger 11 and a hotter side at the respectively associated secondary heat exchanger 12a or 12b. However, as indicated, this can be reversed. Thus, in the illustrated embodiment the primary heat exchanger 11 is cooled and the secondary heat exchangers 12a and 12b are heated by the thermoelectric coolers 13a and 13b.

Each thermoelectric cooler 13a, 13b, i.e. the Peltier elements of the cooler, is in pressurable contact with the relevant heat exchanger either directly or via, for example, a thin layer of a thermally transmissive compound. Such pressurable contact maximises the thermal transmission capability, which is additionally promoted by sealing each Peltier element at its exposed faces by a sealing compound (not shown) excluding ingress of humidity. The pressurable contact is achieved by clamping the assembly of heat exchangers 11, 12a, 12b and thermoelectric coolers 13a, 13b together by means of relatively heavy-duty spring clips (not shown) to form a module of overall compact dimensions. The spring clips resiliently flex to accommodate thermally induced expansion and contraction of the components of the module and thus maintain clamping pressure, but dissipate potentially damaging stresses.

The heat transfer apparatus 10 further comprises a primary circuit 14 for conducting the mentioned liquid on a circulatory path through the primary heat exchanger 11 and a secondary circuit 15 for conducting preferably, but not necessarily, the identical liquid on a circulatory path through each of the secondary heat exchangers 12a and 12b. The two circuits are principally formed by pipes, preferably flexible tubes of plastic, connected to the heat exchanger inlets and outlets. The figure shows slightly larger bore pipework for the primary circuit 14 than for the secondary circuit 15, but any suitable bore relationship, including parity, is possible.

Each circuit 14, 15 has a thermal transfer zone in which heat can be taken up by or discharged from the liquid in the circuit after departure from and prior to return to the respective heat exchanger. In the case of the primary circuit 14, the thermal transfer zone is formed by a sealed or encased reservoir 16 which, in use, contains a body of the liquid of the primary circuit. The pipework of the primary circuit communicates with the interior of the reservoir 16 and its continuity is interrupted in that interior, so that the reservoir effectively has the form of an expansion vessel integrated in the pipework, in which case the primary circuit 14 is effectively a closed circuit. The thus-formed ends of the pipework are located at opposite ends of and near the base of the reservoir casing.

The primary circuit 14 can be filled and, if required, drained at any suitable point, conveniently by way of an inlet/outlet (not shown) at the reservoir casing. The secondary circuit 15 can be filled and, if required, drained at a separate valve-controlled point 15a.

Also forming part of the thermal transfer zone of the primary circuit 15 is a conduit 17 for a volume of a use fluid, here the beverage to be cooled. The conduit 17 is arranged in the reservoir 16 to be submerged in the body of primary circuit liquid when present in the reservoir. In this embodiment the conduit 17 has for the major part the form of coil with multiple turns creating a volumetric capacity of, for example, half a litre for the beverage. The conduit 17 has, externally of the reservoir 16, an inlet end connection to a pipe leading to a storage vessel 18 for the beverage and an outlet end connection to a pipe leading to a beverage dispenser 19, for example a tap or cock. It will be selfevident that by virtue of immersion of the conduit 17, which is intended to hold a volume of the beverage, in the body of primary circuit liquid the reservoir heat exchange between that liquid and the beverage takes place in the sense - since the primary heat exchanger is cooled by the thermoelectric coolers - of cooling of the beverage. It can also be seen that the zone of thermal transfer where heat exchange between the beverage and primary circuit liquid takes place is separate from and isolated relative to the heat exchange unit where heat exchange between the primary and secondary circuit liquids takes place. To that extent, the size and construction of the module forming the heat exchange unit is uninfluenced by the size, construction and disposition of the reservoir 16.

The beverage conduit 17 in the reservoir 16 can be of any suitable form and does not, for example, have to be a pipe. It can be a tank, a heat exchange body of layered construction or any other structure realising the function of a conduit in the widest sense of conducting a flowable substance, here the beverage, from one point to another, in this instance the inlet end connection and the outlet end connection of the conduit.

The thermal transfer zone of the secondary circuit 15 is formed, by way of example, by a radiator 20 integrated in the circuit 15 in a branch line parallel to and connected with the inlet and outlet feeds of the secondary heat exchangers 12a and 12b. The radiator 20 provides thermal exchange with, in this instance gives off heat to, the ambient atmosphere so that liquid heated in the secondary heat exchangers 12a and 12b by virtue of the thermal gradient across the thermoelectric coolers 13a and 13b is cooled prior to return to the secondary heat exchangers. Discharge of heat to the atmosphere can be promoted by a fan (not shown).

Although the secondary circuit 14 functions similarly to the primary circuit 15 as a closed circuit it is connected with the primary circuit by way of an openable and closable valve 21 and also by a further, open connection 22, the latter at a coupling pipe which, however, is passive or inactive in terms of flow unless the valve 21 is open. The purpose of the valve-controlled interconnection of the primary and secondary circuits 14, 15 is three-fold. Firstly, if the valve 21 is opened during filling of the secondary circuit 15 it permits deaeration of the secondary circuit by way of the mentioned otherwise inactive open connection 22 of the two circuits. In these circumstances the valve 21 will generally be maintained in an open state for sufficient time for complete bleeding of the secondary circuit 15, during which the primary circuit 14 can be topped up with liquid to the extent necessary. Deaeration can also be performed at any time after filling of the secondary circuit 15. The valve-controlled interconnection of the circuits also provides an alternative method of filling one circuit by way of the other if this should be desired for any reason. Secondly, if inhibitor is added to one circuit, for example the primary circuit 14, interconnection of the circuits by way of the valve 21 allows distribution of the inhibitor through both circuits. Thirdly, and as described further below, opening and closing of the valve 21 for temporary interconnection of the two circuits permits transfer of colder liquid from the primary circuit 14 to the secondary circuit 15, under displacement of warmer liquid from the latter to the former, to allow cooling of the secondary circuit liquid to a greater extent than achieved by the radiator 20, which provides a means of controlling the temperature at the hot sides of the thermoelectric coolers 13a and 13b by way of the secondary heat exchangers 12a and 12b to prevent potentially damaging overheating of the coolers. In reverse operation of the coolers, with the heat gradient in opposite sense, heating of the cold sides of the coolers reduces the risk of chilling of the coolers.

Circulation of liquid through the heat exchangers 11, 12a and 12b and the primary and secondary circuits 14, 15 is provided by way of a pump 23 or 24 individual to each circuit, the pump 23 for the primary circuit 14 being located in the reservoir 16 near the base thereof and serving to pump fluid into the inlet end - in terms of the selected flow direction, which is clockwise in the flow circuit diagram of Fig. 1 - of the interrupted primary circuit pipework in the reservoir. The pump 24 for the secondary circuit 15 is provided upstream of the radiator 20 in the same branch line as the radiator. Other locations for the pumps 23 and 24 are feasible. Positioning the primary circuit pump 23 in the reservoir 16 near its base offers the advantage of inducting fluid in an area where colder liquid tends to gather. Apart from the two circulating pumps 23 and 24, which can be small-size and low-cost proprietary units, a number of agitating pumps (not shown) can be provided in the reservoir 16 in suitable locations to be immersed in the body of liquid and operated independently of the primary circuit pump 23 so as to agitate the liquid for the purpose of maintaining a substantially uniform temperature of the body of liquid.

The circulating pumps 23 and 24 should preferably always be placed in operation when the thermoelectric coolers 13a and 13b are active so that there is constant circulation through the primary and secondary heat exchangers 11, 12a and 12b and thus a constant heat exchange to counteract any tendency of the coolers to overheat.

Finally, the heat transfer apparatus 10 incorporates a control system which is shown merely in broad outline in the circuit diagram of Fig. 1, which depicts both a fluid flow circuit and elements of an electrical circuit. The latter comprises a control unit 25 which incorporates a microprocessor (not shown) with a memory and which has inputs for inter alia switching on and off and manual temperature selection as well as inputs for supplying temperature-indicative output signal values from temperature sensors 26, 27, 28, 29 and 30 respectively located at the primary heat exchanger 11, at one 12a of the secondary heat exchangers, at or in the vicinity of the reservoir 16 (primary circuit thermal transfer zone), at or in the vicinity of the radiator 20 (secondary circuit thermal transfer zone) and at or in the vicinity of the beverage dispenser 19. Other temperature sensors can be provided at other appropriate locations. The microprocessor is programmed to process the input values and, in dependence on its programming, to issue control or drive signals on outputs thereof to the primary circuit pump 23, the secondary circuit pump 24, a drive unit 31 for the thermoelectric coolers and the valve 21 governing interconnection of the primary and secondary circuits 14, 15. Further outputs are also directed to a status display 32 of, by way of example, four differently coloured light-emitting diodes (LEDs) individually activatable to indicate a respectively associated operating status or mode of the heat transfer apparatus, and to a display bar 33 of sequentially activatable light-emitting diodes (LEDs) positioned in association with the beverage dispenser. The LEDs in the status display are, for example, orange, green blue and red with differing significations as indicated further below and those in the display bar can be blue.

Figs. 2 and 3 are schematic views of an exemplifying constructional layout of the heat transfer apparatus, which can be contained in a single housing 34. The lower part of the housing is occupied by the reservoir 16 and the upper part by the heat exchange unit 11-13b and control unit 25. Provided at a face of the housing 34 are stub pipes 35 of the apparatus pipework for connection to external lines and a control/indicating field 36 with on/off switching means, temperature selection means and the status display of light-emitting diodes. The display can, however, be a separate unit. Figs. 2 and 3 are merely representative of the compact form possible with apparatus embodying the present invention and various specific dispositions of the components of the apparatus are possible.

The operation of the beverage cooling and/or heating device incorporating the heat transfer apparatus is largely self-evident from the description and illustration of the layout and functions of the apparatus components. The apparatus is placed in a readyfor-use state by filling the two circuits 14 and 15, including the reservoir 16, as described above, including bleeding of the secondary circuit 15. The storage vessel 18 is filled with the beverage to be cooled and the dispenser 19 operated to allow beverage to fill the conduit 17 connected with the storage vessel. The device is now ready for operation to cool the beverage in its path from the storage vessel 18 to the dispenser 19.

Power can now be supplied to the thermoelectric coolers 13a and 13b and also to the pumps 23 and 24 so that the liquid in the primary and secondary circuits 14 and 15 is placed in circulation through the primary and secondary heat exchangers 11, 12a and 12b. Heat exchange then takes place between the liquids in the primary heat exchanger 11 and the two secondary heat exchangers 12a and 12b, between the body of liquid in the reservoir 16 and the beverage in the conduit 17 and between the liquid in the radiator 20 and the ambient atmosphere, so that in the end result beverage passing through the conduit 17 is cooled during its dwell time in the conduit. The radiator cooling of the secondary circuit liquid after heating in and before return to the secondary heat exchangers 12a and 12b ensures that the thermoelectric coolers 13a and 13b, which are exposed at their hot sides to that liquid, should not overheat, but if operating conditions and ambient temperatures are such that the coolers are at risk of overheating the valve 21 in the interconnection of the two circuits 14 and 15 can be temporarily opened, in particular in dependence on the temperatures sensed by the sensors 26 and 27 at the heat exchangers 11 and 12a and reported to the control unit 25, so as to introduce colder liquid from the primary circuit 14 into the secondary circuit

15.

In the control system the orange LED of the status display 32 is lit when the heat transfer apparatus 10 is switched on and the green LED is lit when the beverage cooling and/or heating device is ready to dispense a beverage at the required temperature. This may be the case when the temperature sensor 30 located at the dispenser indicates that the measured temperature equals a target temperature input by the user and stored in the memory of the microprocessor. Alternatively, it may be the case when the temperature sensor 28 at the reservoir indicates that the temperature of the body of liquid has equalled a target temperature or has been at a target temperature for a sufficient period of time to ensure the beverage in the conduit 17 is at the correct temperature.

The blue LED is constantly lit when the thermoelectric coolers 13a and 13b are operating to cool the primary heat exchanger 11 and thus the temperature of the body of liquid in the reservoir 16 is being reduced to cool the beverage in the conduit 17. The blue LED can repeatedly flash when that temperature approaches a stored target temperature or equals a boundary temperature slightly above the target temperature. The temperature difference between the boundary temperature and the target temperature can be set by a user. Once the boundary temperature has been reached and the blue LED flashes, the power to the pumps 23 and 24 and the thermoelectric coolers 13a and 13b is gradually reduced until it reaches zero or a low power value capable of maintaining the target temperature the target temperature.

If the heat transfer apparatus is operated in a reverse sense, thus with reverse polarity of the applied voltage at the thermoelectric coolers 13a and 13b, so that the beverage cooling and/or heating device serves to heat the beverage to be dispensed the red LED is constantly lit when the thermoelectric coolers are operating to heat the primary heat exchanger 11 and thus the temperature of the body of liquid is being increased to heat the beverage in the conduit 17. The red LED can repeatedly flash when that temperature approaches a stored target temperature or equals a boundary temperature slightly below the target temperature. This may be determined in the same manner as for the blue LED.

Once the boundary temperature has been reached and the red LED flashes, the power to the pumps 23 and 24 and the thermoelectric coolers 13a and 13b is gradually reduced until reaching zero or a low power value capable of maintaining the target temperature.

As already stated, the control system includes a user input able to be used for, for example, inputting desired settings. For example, the user can set the target temperature, which might automatically determine the boundary temperature. Alternatively, the user might also use the input to set the boundary temperature.

In the case of the LED display bar 33 at the dispenser 19, for example an array of ten blue LEDs, these can be used to monitor the dispensing temperature, typically in degrees. It is possible that these LEDs can indicate a temperature over a wide range, but in the present embodiment the range is ten degrees Celsius, so each LED indicates a single degree; in other embodiments a single LED may be set to represent more than one degree Celsius. The lowest indicatable temperature is set at one degree and the highest temperature at ten degrees.

From a set temperature, the temperature of the beverage to be dispensed may ascend or descend. As the measured temperature increases or decreases, the number of blue LEDs which are lit will increase or decrease respectively. If the measured temperature exceeds the maximum displayed range of ten degrees Celsius, at least one of the

LEDs, such as the top LED in the bar 33, will flash until the measured temperature again re-enters the measured range. One or several of the blue LEDs may flash before turning off or turning on to indicate that the temperature has changed by, for example, one degree.

When, as already mentioned, a user switches on the device and sets a target temperature the orange LED of the status display 32 will light up to indicate that the apparatus is on. The array of blue LEDs of the display bar 33 may then flash in a certain arrangement in order to indicate that the device has been activated. Power will be supplied to the thermoelectric coolers 13a and 13b, which will instantly establish a temperature gradient. If, for example, the target temperature requires the beverage to be cooled, the primary heat exchanger 11 will be exposed to the cold sides and the two secondary heat exchangers 12a and 12b to the hot sides of the two thermoelectric coolers 13a and 13b, in which case the green LED will be constantly lit to indicate that the apparatus is cooling. At the same time the pumps 23 and 24 are activated and circulation in the primary and secondary circuits 14 and 15 takes place. As the primary heat exchanger 11 gradually reduces the temperature of the liquid in the primary circuit the temperature of the body of liquid in the reservoir 16 decreases, which therefore reduces the temperature of the beverage in the conduit 17 and causes the number of activated blue LEDs to gradually decrease.

Once the temperature of the beverage in the conduit 17 reaches the target or boundary temperature, the power supplied to the pumps 23 and 24 and the thermoelectric coolers 13a and 13b will begin to gradually decrease until it reaches zero or a low power value capable of maintaining the target temperature, at which point the blue LED array will indicate the beverage temperature has reached the desired value.

The blue LEDs can be activated in analogous manner if the heat transfer apparatus 10 is utilised to heat rather than cool the beverage. Thus, as the primary heat exchanger 11 gradually increases the temperature of the liquid in the primary circuit 14 the temperature of the liquid body in the reservoir 16 increases and leads to increase in the temperature of the beverage, in which case the number of activated blue LEDs gradually increases. Once the temperature of the beverage reaches the desired temperature, the power to the pumps 23 and 24 and the thermoelectric coolers 13a and 13b is reduced to zero or a low power value capable of maintaining the target temperature and the blue LEDs indicate that the system is ready to dispense the beverage at the desired temperature.

Heat transfer apparatus embodying the present invention offers the advantage of relatively simple and economic construction, particularly through the possibility of use of proprietary heat exchange components and Peltier elements, in conjunction with a comparatively high level of thermal efficiency and a compact size, achieved by, in particular, separation of the region of heat exchange with the use liquid from the region of heat exchange between the primary and secondary circuits.

Claims

1. Heat transfer apparatus for fluids, comprising a heat exchange unit which comprises a primary heat exchanger, a secondary heat exchanger and a thermoelectric cooler arranged therebetween and operable to heat one of the exchangers while cooling the other one of the exchangers, a primary circuit for conducting fluid on a circulatory path through the primary heat exchanger and a secondary circuit for conducting fluid on a circulatory path through the secondary heat exchanger, each circuit having a thermal transfer zone in which heat can be taken up by or discharged from fluid in that circuit after departure from and prior to entry into the respective heat exchanger, wherein the thermal transfer zone of the primary circuit is formed by a reservoir for a body of fluid in the primary circuit and a conduit arranged in the reservoir to, in use, be substantially immersed in such body of fluid and to conduct a volume of a use fluid for taking up heat from or delivering heat to the body of fluid.

2. Apparatus according to claim 1, wherein operation of the thermoelectric cooler is reversible to reverse the sense of heating and cooling of the heat exchangers.

3. Apparatus according to claim 1 or claim 2, wherein the heat exchange unit comprises a further such secondary heat exchanger and a further such thermoelectric cooler arranged between the primary heat exchanger and the further secondary heat exchanger, the thermoelectric coolers being operable in the same sense so as to both heat or both cool the primary heat exchanger.

4. Apparatus according to any one of the preceding claims, wherein the or each thermoelectric cooler is in pressurable contact with the heat exchangers between which it is arranged.

5. Apparatus according to claim 4, wherein the pressurable contact is provided by a plurality of spring clips resiliently deformable to accommodate expansion and contraction of the thermoelectric cooler or coolers.

6. Apparatus according to any one of the preceding claims, wherein the or each thermoelectric cooler comprises at least one Peltier element.

7. Apparatus according to claim 6, wherein the or each Peltier element is sealed against ingress of external moisture.

8. Apparatus according to claim 7, wherein the sealing is provided by a sealing compound.

9. Apparatus according to any one of the preceding claims, wherein the thermal transfer zone of the secondary circuit comprises a radiator for delivery of heat to or taking heat from the ambient atmosphere.

10. Apparatus according to claim 9, comprising an impeller for impelling air towards or away from the radiator.

11. Apparatus according to any one of the preceding claims, comprising controllable propulsion means for propelling fluid around either or each of the primary and secondary circuits.

12. Apparatus according to claim 11, the propulsion means being actuable to propel fluid whenever the or each thermoelectric cooler is in operation.

13. Apparatus according to claim 11 or claim 12, the propulsion means comprising a respective pump in each of the circuits.

14. Apparatus according to claim 13, wherein the pump in the primary circuit is located in the reservoir thereof.

15. Apparatus according to any one of the preceding claims, comprising agitating means in the reservoir for agitating the body of fluid to provide a substantially uniform temperature thereof.

16. Apparatus according to any one of the preceding claims, wherein the conduit defines a coil with multiple turns.

17. Apparatus according to any one of the preceding claims, wherein the conduit has connection means for connection of the conduit at one end with storage means for a use fluid to be heated or cooled and at the other end with a dispenser for dispensing the use fluid after heating or cooling thereof.

18. Apparatus according to any one of the preceding claims, wherein the circuits are interconnected by way of openable and closable valve means.

19. Apparatus according to claim 18, wherein the valve means is selectably openable to place the primary circuit and secondary circuit in flow communication for at least one of the purposes of filling the secondary circuit with fluid from the primary circuit and deaeration of the secondary circuit by way of the primary circuit.

20. Apparatus according to claim 18 or claim 19, wherein the valve means is selectably openable to place the primary circuit and secondary circuit in flow communication for transfer of fluid therebetween to influence the temperature of fluid in the secondary circuit and thereby the temperature of the or each thermoelectric cooler.

21. Apparatus according to claim 20, comprising detecting means for detecting at least one of the temperature at the primary heat exchanger and the temperature at the or at least one secondary heat exchanger and means for controlling the opening and closing of the valve means in dependence on that detected temperature or those detected temperatures.

22. Apparatus according to any one of the preceding claims, comprising detecting means for detecting the temperature of the body of fluid and means for controlling operation of the thermoelectric cooler or coolers in dependence on that detected temperature.

23. Apparatus according to claim 22, wherein the means for controlling the thermoelectric cooler operation is arranged to compare the detected temperature of the body of fluid with a target temperature and to vary at least one of the thermal output of the cooler or coolers and a rate of movement of fluid in either or each of the primary and secondary circuits so as to substantially maintain the temperature of the fluid body at the target temperature.

24. A device for heating or cooling a beverage, comprising apparatus as claimed in any one of the preceding claims, beverage storage means connected with one end of the conduit and a dispenser connected with the other end of the conduit.

25. A device for cooling water, comprising apparatus as claimed in any one of claims 1 to 23, a water mains pipe connected with one end of the conduit and a dispenser connected with the other end of the conduit.

25. A device for cooling water, comprising apparatus as claimed in any one of the preceding claims, a water mains pipe connected with one end of the conduit and a dispenser connected with the other end of the conduit.

Amendments to claims have been filed as follows: