GB2380603A

GB2380603A - Liquid cooling device

Info

Publication number: GB2380603A
Application number: GB0112355A
Authority: GB
Inventors: Roger Barry Moore
Original assignee: ACROKOOL Ltd
Current assignee: ACROKOOL Ltd
Priority date: 2001-05-21
Filing date: 2001-05-21
Publication date: 2003-04-09
Anticipated expiration: 2021-05-21
Also published as: GB2380603B; GB0112355D0

Abstract

A liquid cooling device, in particular a water cooler for cooling drinking water, has a reservoir (2), which is cooled by a permanently operating cooling unit (12) which operates to build up an ice pack (26) within the reservoir. The cooling unit may be a Peltier effect cooling device. Water is dispensed from a melt pool (28) which is surrounded by the ice pack, and therefore cooled. The melt pool is prevented from freezing by a hot finger heater (18) which extends into the reservoir in the region of the outlet (24), and which is controlled by a temperature sensor (20), to maintain an equilibrium between the ice pack and the melt pool.

Description

Liquid Cooling Device The invention relates to a liquid cooling device capable of cooling a supply of liquid to a desired temperature prior to dispensing said liquid. The invention is especially intended for cooling drinking water, often from a mains water supply, in relatively small quantities.

A chilled water fountain is commonly found in many offices in Europe and America. These devices are usually based on a refrigerant cycle with the associated requirement for compressors, pumps, heat exchangers and in most cases, a mains power supply to satisfy the power requirements of the compressor and pump.

It is knows 10 use Peltier effect heat pumps to cool liquids as disclosed in patent document GB 2 338 544 A, but such Pettier heat pumps are difficult to control accurately and the temperature control circuit for a Peltier effect cooler is therefore necessarily complex and expensive. It is for these reasons that Pelt er effect heat pumps for liquid cooling have never fully succeeded in practice. Also for mains water pressure there have been problems in seaing'01 rings to plastic vessels.

The present invention seeks to provide an improved apparatusforliquidcooling.

According te the invention there is provided a liquid cooling de-.'ce comprising a reservoir, a permanently

operating cooling unit arranged to cool liquid to below the freezing point of the liquid, an inlet to and an outlet from the reservoir, a heating unit arranged to raise the temperature of the liquid in the reservoir in the vicinity of the output, and means for controlling the output of the heating unit.

This arrangement simplifies the control circuit of the cooling unit, because a simple on/off control of a heating unit is all that is required. The control of heading units is simple and well understood.

The frozen liquid will form an ice pack within the reservoir, which will act as a large negative thermal reservoir to cool incoming and outgoing liquid. The heater will maintain a liquid melt pool in the vicinity of the reservoir cutlet. Liquid will be drawn from and introduced to the melt pool. The ice pack will aid in stabilising the temperature the cooling unit the melt pool in instances when the majority of the melt pool liquid has been drawn off and is replaced with liquid introduced at an ambient temperature which is substantially above the temperature at which liquid is to be dispensed.

The term"ice''as used herein refers not on2. r frozen water, but also to any frozen liquid within the reservoir.

Preferably of has no moving parts. The

advantage no moving parts is that the reliability of the coolinc un-t is improved, as wear and tear is unlikely

to cause a problem. A Peltier effect heat pump may be used as the cooling unit. Such devices have no moving parts and draw little power. When a Peltier effect beat pump is run continuously a a set level, its lifetime increases above that normally expected when the output is varied continuously.

The low power draw from these solid state devices mean that it is possible to run the cooling unit from a low voltage (for example a 12V power supply) rather than from a mains power supply. A cooling unit that will run from a 12V supply can be run from (rechargeable) bakeries and can be fully independent of the power supply of a given country and may be used anywhere in the world with a suitable adapter. An added benefit of a 12V power source is that it allows the cooling devices to be used in vehicles, such as cars, planes, trains and coaches and also in third world countries in areas reliant upon alternative energy sources, such as wind or solar power.

Thermostatic control of the heating unit may be achieved by the addition of a temperature sensor within the reservoir. The temperature sensor, when connectez ce the means for controlling the heating unit output, can be used for feedback control of the heating unit oucpuc so that the temperature within the reservoir may be stabilised.

Preferably temperature sensor and heating unit are housed in a unitary structure. This arrangement ensures

that the te-. peraure sensor is always within he'e pool

and since she support for the temperature sensor is incorporated into the heating unit housing, there will be a lower component count and hence a lower cost.

Preferably the heating unit includes an electric heater.

Electric heaters have no moving parts and therefore have reliability advantages. The output of an electric heater is also simple to control accurately. An electric heater can be operated so that its power draw is small and this will facilitate the use of a 12V power supply for the liquid cooling device.

The heating unit could be in the form of a"hot finger" within the reservoir. This will create an approximately cylindrical shaped melt pool within the ice pack. This melt pool within the ice pack helps to reduce the need to compensate for the mechanical expansion of ice if water or an aqueous liquid is being cooled.

Preferably the reservoir has an external flat surface against which the cooling unit is mounted. This ensures good thermal contact between the cold side of the cooling unit and the wall of the reservoir. The reservoir walls are preferably of a heat conducting material, and the reservoir may be provided externally with insulation.

The top wall cf the reservoir may be domed, tc ensure that any air which accumulates within the reservoir collects at a single from which it can be evacuated if necessary. The domed shape also has a greater strength in

a pressurised environment, such as being connected to mains water pressure.

The liquid outlet is preferably a pipe extending into the reservoir at an angle to the vertical. This helps to reduce the risk of air being trapped in the liquid outlet.

Heat energy from the hot side of the cooling unit may be supplied to the heater to provide at least some of the energy for the heater. This would further reduce the energy requirements of the liquid cooler, as the heating unit would draw less energy. The hot side of the cooling unit must be cooled to avoid overheating and possible damage and this arrangement reduces energy wastage.

The liquid being cooled may be a beverage, and in particular may be water as would be the case for water coolers in offices.

The desired temperature of the melt pool for a beverage is in the range of approximately 5 C to 8 C. This temperature range provides an acceptably chilled drinking temperature for most beverages. It is possible that for a particular liquid it may be desirable to serve at a temperature outside this range.

Cooled wacer may optionally be dispensed through an activated charcoal filter and/or an ultra-viole filter.

Both these fillers enable impure water to be purified to provide potable drinking water. The exact nature, size and

lifetime of such filters will depend upon local water conditions. The use of filters to provide potable water from impure local supplies has many health advantages, particularly-n the third world.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross section view of a water cooler according to the invention ; Figure 2 shows a schematic cross section view of a second embodiment of a water cooler according to the invention having the hot side of the Pelcier heat pump supplying heat to the heater ; Figure 3 shows a detail of part of a third embodiment of the invention ; and Figure-shows a cross section through another embodiment of the invention.

Figure 1 shows a water cooler 1 comprising a reservoir 2.

The reservoir 2 has a substantially cylindrical wall 4 formed from copper metal. The reservoir 2 is closed at the bottom by a base 6 and at the top by a : 8p plate 8 both made from copper metal. Copper metal is used as it has a good ihermal conductivity and will ensure rapid heat distribution around the walls of the reservoir. The

cylindrical wall 4 has a raised flat surface portion 10. The wall 4 is safe for use with potable liquids and thus the vessel carL act as both a container for a potable liquid and the means of cooling a potable liquid.

A control unit 30 provides electrical power at 32 to a Peltier hear pump 12. The pump will be permanently ON.

The control unit 30 is also electrically connected at 34 to a thermistor temperature sensor 20. The control unit 30 receives a signal from the temperature sensor 20 indicative or the temperature of the sensor. A"hot finger" heater 18 is electrically connected ai 36 to the control unit 30. The control unit 30 thermostatically controls the"hot finger"heater 18 in response to the signal received from the temprature sensor 20 to maintain the temperature of the sensor 20, and thus the melt pool 28, within a predetermined temperature range.

A Peltier heat pump 12, having a hot surface 14 and a cold surface 16 is located on the raised flat surface portion 10 of the reservoir. The Peltier heat pump is arranged with the chid surface 16 adjacent to the flat portion 10 so as to n due good thermal coupling between the cold surface 16 c- the Peltier heat pump 12 and the reservoir 2. The thermal coupling of the cold surface 2. 6 of the Peltier heat pump 12 mith the reservoir 2 will result in cooling of the reservoir 2 and any contents.

The elonca-e ~, : indrica"not finger"heaXe--8 passes through the : =rre of the top plate 8 of the reservoir 2.

The"hot finger"heater 18 carries the temperature sensor 20 at an end 13 within the reservoir 2.

On initial switching on of the water cooler 1, water is filled into the reservoir. The water freezes to form an ice pack 26 within the reservoir 2 due to cooling from the Peltier heat pump 12 on the wall of the reservoir 2. This ice pack 26 is prevented from entirely occupying the interior of the reservoir 2 by heating from the"hot finger"18. Since ice is prevented from entirely occupying the vessel, problems with ice expansion within the vessel are avoided. This heating maintains a melt pool 28 at a predetermined temperature within the reservoir 2.

An inlet pipe 22 and an outlet pipe 24 pass through the top plate 8 of the reservoir 2. These pipes are located near to the finger"18 and the water in and around the pipes is prevented from freezing by heating from the "hot finger"18. The inlet pipe 22 supplies water at an ambient temperature to the melt pool 28 to replace chilled water drawn from the melt pool 28 through the cutlet pipe 24, and the incoming water is chilled by its exposure to the ice pack.

The hot surface 14 of the Peltier heat pur : p 12 will dissipate heat energy as part of the operation of the pump. A heat sink will normally be thermally coupled with the hot surface 14 of the Peltier heat pump 12. The heat sink increases the surface area from which heat is dissipated and hence increases the rate ci cooling

obtainable from the Peltier heat pump 12.

Figure 2 shows a second embodiment of a water cooler 101 according to the invention. Features of the invention that are the same as in the previous embodiment are labelled with similar reference numerals incremented by 100.

In this embodiment some of the energy supplied to the"hot finger"heater 118 comes from the hot surface 114 of the Peltier heat pump 112.

The means to supply the heat energy from the hoc surface 114 of the Peltier heat pump 112 to the ringeril heater 118 includes a pump 50 which is electrically

connected at 52 to the control means 130. The pump 50 is controlled in a similar manner to the Peltier heat pump 112 such that when the Peltier heat pump 112 is on, the pump 50 is also on. A heat carrier fluid 56 flows in a circuit 54,55 between a heat exchanger 58, where it receives heat energy, and a"hot finger"heater 118 where the fluid gives up heat to the melt pool. The pump 50 circulates the fluid around this circuit.

This provides means for dissipating heat from uhe hoc end of the Pelcier heat pump 112 while at the same time providing heat to the"hot finger"heater. This will reduce power wastage and hence reduce power consumption of the water cooler 101.

Also shown-n this embodiment, although.- :-. ; culd be

equally applicable to the embodiment of Figure', is that the outlet pipe 70 has an end 72 into which chilled water passes from the melt pool 128 which is located at a high point within the reservoir 102. This location of the end 72 of the outlet pipe 70 allows any gas entrained with the inlet water to be drawn off with the chilled water from the melt pool 128 each time the water cooler 101 is used.

Figure 3 shows an embodiment where the top of the reservoir is domed at 308, so that any air which accumulates in the reservoir can be collected at one point 311. Small air holes 325 are provided in this area so that air which collects in this part of the reservoir will be entrained in the water being drawn off and removed from the system.

The hot finger function can be provided by an electrical winding or the like wound around the outlet 324. Using the outlet to support the hot finger heater results in a smaller number of openings through the reservoir wall.

For a domestic water fountain, or indeed for a water fountain used in commercial premises, the reservoir may have a nominal volume of 1 litre. This volume s chosen due to observations that a water cooler is rarely used continuously. Jsually the volume of water drawn of at any one time does not exceed 0.4 litres. For this reason the melt pool would have a volume of around 0. 4 litres. These volumes could be increased if a higher demand was anticipated, for instance in a commercial environment.

Although the invention has been described in relation to a water cooler, it is equally applicable to any liquid that may be frozen.

The invention is also provides a method for controlling an ice bank. Once equilibrium is reached between heat added (by liquid or heat input) and heat taken out through the ice bank by che cooler, the size of the ice bank may be varied by maintaining a constant rate of heac removal (cooling) and altering the rate of heat addition. This methodology is applicable to any ice bank situation, for instance a beer cooling device.

Claims

Claims 1. A liquid cooling device comprising a reservoir, a permanently operating cooling unit arranged to cool liquid to below the freezing point of the liquid, an inlet to and an outlet from the reservoir, a heating unit arranged to raise the temperature of the liquid in the reservoir in the vicinity of the outlet, and means for controlling the output of the heating unit.
2. A liquid cooling device as claimed in Claim 1, in which, during use, a frozen liquid pack and melt pool are formed within the reservoir.
3. A liquid cooling device as claimed in Claim 1 or Claim 2, in which the cooling unit is a Peltier effect heat pump.
4. A liquid cooling device as claimed in Claim 3, in which the Peltier effect heat pump is run substantially continuously at a substantially set level during operation.
S. A liquid cooling device as claimed in any preceding claim, in which a temperature sensor is located within the reservoir and is connected to the means for controlling the output of the heating unit such that thermostatic control of the heating unit may be achieved.
6. A liquid cooling device as claimed in Claim 5, in

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which the temperature sensor and heating unit are housed in a unitary structure.
7. A liquid cooling device as claimed in any preceding Claim, in which the heating unit is at least partially electrically powered.
8. A liquid cooling device as claimed in any preceding claim, in which the heater unit forms a"hot finger" within the reservoir.
9. A liquid cooling device as claimed in any preceding claim, in which the reservoir has a flat area of thermally conductive material against which the Peltier heat pump is mounted.
10. A liquid cooling device as claimed in any preceding Claim, in which heat energy generated at a hot side of the cooling unit is supplied to the heating unit to provide at least some of the energy for the heating unit.
11. A liquid cooling device as claimed in any preceding Claim, in which the liquid to be cooled is drinking water.
12. A liquid cooling device as claimed in Claim 11, in which the desired temperature of the water is within the range of approximately 5 C to 8C.
13. A liquid cooling device as claimed in Claim 11 or Claim 12, including an activated charcoal filter through

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which the cooled drinking water is dispensed.
14. A liquid cooling device as claimed in any of Claims 11 to 13, including an ultra violet filter through which the cooled drinking water is dispensed.
15. A liquid cooling device as claimed in any previous claim in which the liquid cooling device is powered by a 12V electrical power supply.
16. A liquid cooling device substantially as herein described with reference to any one embodiment shown in the accompanying drawings.