WO1999067004A1

WO1999067004A1 - Apparatus and process for purifying and chilling a liquid

Info

Publication number: WO1999067004A1
Application number: PCT/CA1999/000575
Authority: WO
Inventors: Youssef Hanna Dableh
Original assignee: Youssef Hanna Dableh
Priority date: 1998-06-19
Filing date: 1999-06-18
Publication date: 1999-12-29
Also published as: CA2241168A1; AU4354999A

Abstract

A liquid, particularly water, purifier and refrigerator (10) comprising a housing (12) having a first chamber (14) and a second chamber (16); divider means (18) separating the first and second chamber one from the other; the divider means (18) comprising a thermoelectric module (32) having a first heat sink (34) received within the first chamber and a second cold sink (36) within the second chamber means (26) for feeding water to the first heat sink within the first chamber (14) to produce water vapour; transfer means (58) for transferring the water vapour to the second cold sink to effect condensation of the water vapour to produce purified water; and means (54) for removing the purified water from the second chamber. The purifier and associated method provides a means for producing purified liquid in a safe, reliable, convenient, relatively cheap manner, having low energy requirements, and which either eliminates or reduces the disadvantages of prior art purifiers.

Description

APPARATUS AND PROCESS FOR PURIFYING AND CHILLING A LIQUID

FIELD OF THE INVENTION

This invention relates to a process of purifying and to cooling a liquid, particularly water, using a thermoelectric module and apparatus of use in said processes.

BACKGROUND TO THE INVENTION

Thermoelectric modules are small, solid state, heat pumps that cool, heat and generate power. In function, they are similar to conventional refrigerators in that they move heat from one area to another and, thus, create a temperature differential. A thermoelectric module is comprised of an array of semiconductor couples (P and N pellets) connected electrically in series and thermally in parallel, sandwiched between metallized ceramic substrates. In essence, if a thermoelectric module is connected to a DC power source, heat is absorbed at one end of the device to cool that end, while heat is rejected at the other end, where the temperature rises. This is known as the Peltier Effect. By reversing the current flow, the direction of the heat flow is reversed.

It is known that a thermoelectric element (TEE) or module may function as a heat pump that performs the same cooling function as Freon-based vapor compression or absoφtion refrigerators. The main difference between a TEE device and the conventional vapor-cycle device is that thermoelectric elements are totally solid state, while vapor-cycle devices include moving mechanical parts and require a working fluid. Also, unlike conventional vapor compressor systems, thermoelectric modules are, most generally, miniature devices. A module typical measures 2.5 cm x 2.5 cm x 4 mm, while the smallest sub-miniature modules may measure 3 mm x 3 mm x 2 mm. These small units are capable of reducing the temperature to well-below water-freezing temperatures. Thermoelectric devices are very effective when system design criteria requires specific factors, such as high reliability, small size or capacity, low cost, low weight, intrinsic safety for hazardous electrical environments, and precise temperature control. Further, these devices are capable of refrigerating a solid or fluid object. A bismuth telluride thermoelectric element consists of a quaternary alloy of bismuth, tellurium, selenium and antimony - doped and processed to yield oriented polycrystalline semiconductors with anisotropic thermoelectric properties. The bismuth telluride is primarily used as a semiconductor material, heavily doped to create either an excess (n-type) or a deficiency (p-type) of electrons. A plurality of these couples are connected in series electrically and in parallel thermally, and integrated into modules. The modules are packaged between metallized ceramic plates to afford optimum electrical insulation and thermal conduction with high mechanical compression strength. Typical modules contain from 3 to 127 thermocouples. Modules can also be mounted in parallel to increase the heat transfer effect or stacked in multistage cascades to achieve high differential temperatures.

These TEE devices became of practical importance only recently with the new developments of semiconductor thermocouple materials. The practical application of such modules required the development of semiconductors that are good conductors of electricity, but poor conductors of heat to provide the perfect balance for TEE performance. During operation, when an applied DC current flows through the couple, this causes heat to be transferred from one side of the TEE to the other; and, thus, creating a cold heat sink side and hot heat sink side. If the current is reversed, the heat is moved in the opposite direction. A single-stage TEE can achieve temperature differences of up to 70°C, or can transfer heat at a rate of 125 W. To achieve greater temperature differences, i.e up to 131°C, a multistage, cascaded TEE may be utilized.

A typical application exposes the cold side of the TEE to the object or substance to be cooled and the hot side to a heat sink, which dissipates the heat to the environment. A heat exchanger with forced air or liquid may be required.

Water in bulk may be purified by a number of commercial methods, for example by reverse osmosis and by distillation processes. Reverse osmosis (R.O.) technology relies on a membrane filtration system that is operated under high pressure. While this technology is one of the two leading technologies of water purification, it suffers from the following main disadvantages :-

(a) the infrastructure of the system is complex because of the operating pressure, typically 8 atmospheres, required to cause the reverse osmosis process in the membrane;

(b) the membrane is an expensive component that needs to be replaced, frequently, depending on the salinity and the purity of the source water, generally, every 4 to 6 months. Also, there is a problem of membrane fouling, if the quality of the source water is not within certain bounds. The restriction on the water quality that is inputted into the system precludes many sources of water or would necessitate the utilization of pretreatment systems;

(c) the amount of purified water is very low when compared to the amount of water that has to be pumped into the system. Therefore, the cost of pumping and discharging the rejected water (capital cost to install the required facility and the energy cost to operate and maintain it) makes this system very costly;

(d) the quality of purified water obtained by the reverse osmosis process is inferior to that of distilled water, in the sense that it leaves small microorganisms and any impurities that are small enough to go through the membrane. Also, as the membrane ages, the water quality does not remain consistent;

(e) the system is feasible from a physical and economical point of view, for only large commercial installations. The system is not amenable for use in household units or even in small commercial units; and

(f) energy, operating and maintenance costs are high for the R.O. system. The main disadvantages of distillation technologies, such as the multistage flashback evaporation systems, are:-

(i) relatively large capital cost needed to assemble and install the system;

(ii) high energy costs to perform the evaporation, provide energy and equipment for the vacuum system and the condensation in, literally, three independent subsystems; (iii) significant corrosion problems that necessitate significant pretreatment of input water and complete replacement of plant equipment as frequently as every three to four years;

(iv) the system, generally, needs to be installed only near large power plants and large bodies of water; and

(v) the disadvantages listed in item (e) and (f) hereinabove.

There is, therefore, a need to provide a means for producing a purified liquid, particularly water, in a safe, reliable, convenient, relatively cheap manner, having low energy requirements, and which either eliminates or reduces the aforesaid disadvantages.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for producing a purified liquid, particularly water in a safe, convenient, reliable and relatively cheap manner by means of thermoelectric modules to generate hot and cold heat sinks.

Accordingly, in one aspect the invention provides a process for treating an impure liquid to produce purified liquid, said process comprising -

(i) electrically activating a thermoelectric module to provide a heated surface and a cooled surface; (ii) feeding said impure liquid to said heated surface to produce vapour of said liquid; (iii) transferring said vapour to said cooled surface to effect condensation of said vapour to produce said purified liquid; and (iv) collecting said purified liquid.

In this specification and claims the term "heatable or heated surface" means a surface of said module which is heated when said module receives an electric current or a surface in thermal communication with said module as to be heated thereby. The term

"coolable or cooled surface" means a surface of said module which is cooled when said module receives an electric current or a surface in thermal communication with said module as to be cooled thereby.

In a particularly valuable aspect, the liquid is water, and by the term "impure water" is herein meant water containing impurities such as, for example, dissolved salts and other matter, and/or suspended particulate matter which impure water may be evaporated and concentrated without unwanted carry-over of such impurities. The term "vapour" includes "steam".

Preferably, the invention provides process for treating an impure liquid to produce purified liquid, said process comprising - (i) electrically activating a thermoelectric module to provide a heated surface in a first chamber and a cooled surface in a second chamber; (ii) feeding said impure liquid to said heated surface to produce liquid vapour; (iii) transferring said liquid vapour from said first chamber to said second chamber;

(iv) contacting said liquid vapour on said cooled surface to effect condensation to provide said purified liquid; and (v) collecting said purified liquid.

In a further aspect, the invention provides a liquid purifier comprising an apparatus for purifying an impure liquid comprising thermoelectric module means having a heatable surface and a coolable surface; means for feeding said impure liquid to said heatable surface to produce vapour of said liquid; and means for transferring said vapour to said coolable surface to effect condensation of said vapour to produce said purified liquid. The means for transferring vapour to the coolable surface may, include, for example, merely, conduit, passage or the like which allows the vapour to pass to the cold sink.

Preferably, the apparatus has a vacuum extraction means, forced-air fan or other suitable means for enhancing the transfer of the vapour from the first chamber to the second chamber. Most preferably, the apparatus has a plurality of the thermoelectric modules aligned coplanar within a divider between the chambers and/or within one or more walls of the chamber.

In preferred embodiments, a pair of thermoelectric modules are linked in cascade i.e. connected in series thermally, herein termed a double module. Thus, preferably, a plurality of double modules are arrayed in coplanar fashion in a planar member to provide, for example, a plurality of heatable surfaces on one i.e. front face of the member and a plurality of coolable surfaces on its rear face. The aforesaid front face may constitute an inner face of a chamber and the aforesaid rear face constitute the corresponding outer face of the chamber. In the case of a cylindrical or a cubic, rectangular or other polysurfaced chamber, each of the inner surfaces may comprise a plurality of heatable (or coolable) module surfaces, to provide enhances heat transfer surface to chamber volume ratios. The distance between a pair of such opposing heatable (or coolable) module surfaces may be so minimized as to provide a bank of interleafed fins, vanes and the like.

Thus, the present invention provides in one aspect a water purification system which provides the advantages of:- (a) providing both water evaporation and cooling simultaneously within the same unit; (b) being significantly energy efficient because the same amount of electrical energy is used to perform evaporation, condensation and chilling; which energy utilization does not exist in any of the water purification technologies known at this time;

(c) recovering all of the water inputted into the system as pure water, without having to discharge water with high concentrations of impurities and salt as is the case in reverse osmosis technology;

(d) portability of the system and its ability to be scale up over a very wide range of dimensions and capacities; and wherein the capacity of the system can be increased in a modular fashion; (e) having the ability to energize the system from a very wide variety of power sources, such as, for example, operable throughout in the world, including remote areas that are not even connected to an energy generation grid; and

(f) having the ability of the system to handle any type of water regardless of its salinity and impurities, while still producing pure water that has the same quality as distilled water, which is free from all organic, non-organic and microbial elements.

I have discovered that although condensation of liquid on the cold/heat sink surface is efficaciously obtained, preferably an enhanced temperature gradient across the module units by use of a double module, in cascade enhances efficiency by reducing the effect of the thermal capacity of the vapour when it is condensed on the cooler surface. For example, under steady state conditions, a simple module may provide a temperature of 80-90°C on its "hot" surface and a temperature of 20 - 30°C on its colder surface to provide a temperature gradient of about 60°C. However, a double module can generate a temperature of about 105°C on its hot side and about 15°C on its colder side for a temperature differential of about 90°C.

To further reduce the unbalance rise in temperature of the cold side surface by condensation, the heat sink mass/cold sink mass ratio is preferably selected from 1:1 - 1 :5, preferably about 1:3. This ratio may be achieved by judicious selection of relative weights, thermal characteristics, materials and the like.

I have found that non-insulated surfaces of vapour receiving chambers, conduits and the like enhance condensation of the vapour to reduce the load on the module cold surface.

This advantageous arrangement can be enhanced by passing the feed liquid through or around the cold chamber to enhance condensation and also pre-heat the feed water.

It is a further aspect of the present invention to provide a plurality of multimodule units in the form of an assembly, which may be so designed to be of modular construction as to be built-up to any desired operating size. The apparatus according to the invention may be operated over significant periods of time when the feed liquid is fully evaporated. However, this may cause a build-up of impurities on the hot side surface of the module which may require downtime cleaning of the fins, vanes and the like. In an alternative process, sufficient feed liquid may be sprayed, poured, trickled, dropped and the like at a rate to provide "runoff' and continuous removal of the impurities. I have found that as little as a 10% run- off, coupled with a 90% recycle and 10% removal from the recycle loop is sufficient to enable continuous operation.

The invention in a further aspect provides a method of cooling or chilling a liquid or mamtaining a liquid at a desired low temperature by contacting the cold sink of a thermoelectric module means with the liquid. Preferably, the module means forms part of a wall of a liquid containing chamber and wherein the hot side sink protrudes external of the liquid reservoir.

Accordingly, in a further aspect, the invention provides a method of refrigerating a fluid comprising electrically activating a thermoelectric module to provide a cooled surface and contacting the fluid with the surface. In a yet further aspect, the invention provides a refrigeration unit for refrigerating a fluid comprising a housing defining a chamber for containing the fluid; a thermoelectric module means having a coolable sink means within the chamber and being adapted to receive an electric current to activate the module means to cool the coolable sink means. The refrigeration unit may comprise electric power supply means such as a battery, solar power generator, AC generator/transformer unit and the like as a "standalone" unit.

The aforesaid method and refrigeration apparatus may be used when the fluid is a liquid, air or other gas.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be better understood, preferred embodiments will now be described by way of example only, with reference to the accompanying drawings wherein Fig. 1 is a block diagram of a water purifier according to the invention;

Fig. 2 is an exploded, isometric view, in part, of a hot end sink of a divider plate of use in the present invention;

Fig. 3 is an isometric view of a divider plate, in part, of use in the present invention;

Fig. 4 shows an exploded diagrammatic section of a double module arrangement within a divider or wall of use in the present invention;

Figs. 5 - 7 represent diagrammatic vertical sectional views of alternative embodiments of liquid purifiers according to the invention; and wherein the same numerals denote like parts.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Fig. 1 this shows generally as 10 a water purifying apparatus having a rectangularly-shaped container 12 partitioned into a "hot-end" chamber 14 and a

"cold-end" chamber 16 by a planar divider member shown generally as 18, as hereinafter further described. Container 12 has walls 20, base 22 and top 24, thermally insulated by a layer of polystyrene 25. Top 24 has a water inlet sprinkler head 26 which receives a supply of impure water through a conduit 28.

With reference now also to Fig. 2 divider plate member 18 has a thermally insulating polystyrene frame 30, within which is retained a plurality of thermoelectric modules 32 (PolarTEC™ model PT2-12-30; Melcor Corporation, Trenton, N.J., U.S.A.), each of which is connected to a hot end sink 34 protruding within chamber 14 and a cold end sink 36 within chamber 16. The modules 32 are essentially in coplanar arrangement one adjacent another separated by the intervening patchwork of polystyrene. Each hot end sink 34 and cold end sink 36 consists of a rectangularly shaped copper block spacer 38, which at its "hot" face 40 is abutted to thermoelectric element 32 in a satisfactory, thermally conductive manner. Copper spacer 38 at its coplanar face 42, opposite its face 40 is bonded to a multi-finned member 44, formed of aluminum having a plurality of fins 47 extending perpendicularly to divider plate 18. Cold end sink 36 consists of an analogous copper spacer and aluminum multi-finned member arrangement bonded to the appropriate face of module 32, i.e. its' "cold" face. Sprinkler head 26 is so arranged as to operatively direct an appropriate water flow onto finned member 44 as to effect vapourization of the water. Within chamber 16 is suitably located a water level sensor 48 and a thermal sensor 50, both electrically connected to a microprocessor control unit 52. Chamber 16 has a water outlet 54 within a wall 20. Within chamber 14 is a water heater 46 for optionally boiling off any excess water which drips to the bottom of chamber 14. A drain plug 15 is provided in base 22, for chamber cleaning purposes. Divider member 18 has an upper portion defining an aperture 56 within which is an extraction fan 58 for transferring steam from chamber 14 to chamber 16.

DC power is supplied to the thermoelectric element array in divider member 18 from a solar panel 60 and/or 12 volt DC power supply 62 through control unit 52. Water is fed through conduit 28 and solar panel 60 under the control of valve 64 and control unit 52 from water source 66.

In the embodiment shown in Fig. 1, container 12 has dimensions of 50 cm length, 35 cm wide and 30 cm high. Chamber 14 for water evaporation is 15 cm long, while chamber 16 for steam condensation is 25 cm long. Divider member 18 is 10 cm wide and in the embodiment described has six thermoelectric modules having dimensions of 2.5 cm wide x 2.5 cm long x 0.5 cm thick and 12 V - 2 amp rating, sandwiched between the hot and cold heat sinks. The distance between the two heat sinks is increased by copper spacers 38 to a suitable distance, because the 0.5 cm thickness of the modules offers low thermal resistance between the hot and cold sides of the elements. Use of the copper spacers enhances the thermal resistance and minimized the effect between the hot side on the sold side.

I have found that the use of pump extraction fan 58 or a vacuum pump within divider member 18 enhances water evaporation and transfer to chamber 16 without the need for a boiling temperature of about 100°C. Very satisfactory evaporation can be achieved at 70 - 80°C, to result in significant savings in energy. During a steady state operation the temperature on the hot side of the heat sink was between 50 - 60°C while the temperature on the cold side was 10 - 15°C, to provide a gradient in temperature of 35 - 50°C, which is less then the designed rate of these elements (70°C), and consequently, the efficiency of the thermal electric elements increases. Under intermediate operations the temperature of the hot side reached 85°C and 25°C at the cold side. Water level sensor 48 on the cold side monitors the water level and sends a signal when the water level is above or below the desired range. The thermal sensor 50 monitors and maintains the temperature of the cold water within desired limits. When the temperatures rises above the desired limited, sensor 50 sends a signal to processor 52 to turn on thermal modules 32 and cool the water. Water has been purified at a steady-state rate of 400 ml/hour in the relatively small embodiment of Fig. 1.

With reference to Fig. 4, this shows a basic double module block generally as 100 having two pairs of modules 32 in cascade and sandwiched to a pair of outer copper block spacers 38 and 38' and an inner block spacer 138 of different sizes. Outer spacer 38 abuts finned, aluminum hot heat sink member 44, while outer spacer 38' abuts finned, aluminum cold sink member 36 which is of greater size by volume than member 44, in the embodiments shown. Metal spacers 38, 38' and 138 are provided to build the necessary thermal barrier between the hot and cold heat sinks, to control the edge effects of thermal conduction between the cold and hot sides of each module, and to facilitate assembly into the larger hot and cold heat sinks 44 and 36, respectively.

Fig. 5 shows an embodiment wherein a pair of adjacent module blocks shown generally as 200 within a chamber 201 have their hot heat sinks 202 adjacent and facing each other such that fins 204 interleaf with opposing fins as to rninimize the inter sink distance and, thus, the volume available between the sinks for liquid to evaporate and the assembly as a whole. Liquid may be trickled down, around or through the fins, if the latter are perforated, at such a rate as to provide efficient evaporation and run-off if desired.

This modular two-block assembly may contain one or more thermoelectric double modules 206 per block, (two in each block as shown in Fig. 5) and be of a length, width and height as desired, extendable in either of these directions by the addition of or modification of blocks. In an analogous manner, the cold side fins may be interleafed for optimum condensation, as demonstrated by the ghost lines.

It can be readily seen that this interfin arrangement may be suitably utilized as a fractionating column to effect fractionation of two or more liquids having different boiling points. Cycling of the upper and lower fraction to their adjacent suitable two- block units through the desired number of plates effects fractionation to the desired degree. Such an arrangement is of value, for example, in the fractional distillation of aqueous organic liquid mixtures, such as solvents, alcoholic spirits and the like, and petroleum products, such as, gasoline distillates. The term "purified" in this specification includes, when used in the context of purifying two or more liquids by the aforesaid fractional distillation method and apparatus, enhancement of the amount of one of the liquids relative to another in the fractionated products over the relative amounts in the feed liquid mixture.

Fig. 6 represents a water purifying apparatus shown generally as 300 incoφorating the modular two-block unit of Fig. 5. A water inlet 302 is disposed above hot interleafed fins 304 and water provided by gravity feed and/or at a rate as to provide a 10% run-off of impure water for a 90% run-off return to unit 300. The associated pair of fins 304 may be interleafed in whole or in part. Condensed water from cold fins 306 is collected in reservoir 308. An auxiliary module 312 has its cold sink fins 314 protruding into reservoir 308 and acts as a refrigeration unit or a chiller to maintain the liquid at a desired temperature. Hot sink fins 316 protrude external of reservoir 308.

Assembly 300 may be extended horizontally, lengthwise and width, and vertically.

In the aforesaid embodiments, it will be recognized that volatile materials may be vented off to some degree if their boiling points are less than 100°C. The specific temperature gradients within a unit is controlled by adjustment of the electric currents fed to the modules.

Enhanced chilling of the condensed liquid may be readily attained if desired, for example, by chiller module 312. Fig. 7 shows generally as 400, a multi-sided unit in the form of a cube having walls defining a chamber 401, wherein each of the four vertical sides 402 comprise a plurality of multi-block, preferably of double module unite 404 having their hot heat sinks 406 facing inwardly and their cold sinks 408 facing outwardly. The top and bottom of the chamber may, optionally, comprise a similar arrangement. Chamber 401 is provided with a liquid feed inlet 408, a vapour outlet and an impure liquid run-off outlet 410. Unit 400 is contained within a larger cubic container 412 which defines with unit 400 an inner condensing passage 414. The respective cold sinks of the modules face outside of the chamber walls within surrounding passage 414, and receive vapour to effect condensation.

The chamber walls of the aforesaid embodiments may be in the form of a right- vertical cylinder to provide a single vertical surface. The chambers may be fully or partially open-ended or closed at the top if provided with a vapour conduit, vent or like passageway for vapour to escape to the cold sink.

Several cleaning methods can be implemented for this system. These methods include, but are not limited to: 1. Jet cleaning.

2. Sonic technology.

3. Chemical cleaning.

4. Manually cleaning (opening a re-sealed lid and scrubbing the tank).

5. Continuous water feed to prevent build-up, with recycle of run-off and about 10% of run-off sent to sewer or treatment.

The selection of a particular cleaning method will depend on the size of the system and the economic considerations for a particular unit.

Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to those particular embodiments. Rather, the invention includes all embodiments which are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated.

Claims

1. A process for treating an impure liquid to produce purified liquid, said process comprising -

(i) electrically activating a thermoelectric module to provide a heated surface and a cooled surface;

(ii) feeding said impure liquid to said heated surface to produce vapour of said liquid; (iii) transferring said vapour to said cooled surface to effect condensation of said vapour to produce said purified liquid; and (iv) collecting said purified liquid.

2. A process for treating an impure liquid to produce purified liquid, said process comprising -

(i) electrically activating a thermoelectric module to provide a heated surface in a first chamber and a cooled surface in a second chamber; (ii) feeding said impure liquid to said heated surface to produce liquid vapour; (iii) transferring said liquid vapour from said first chamber to said second chamber; (iv) contacting said liquid vapour on said cooled surface to effect condensation to provide said purified liquid; and

(v) collecting said purified liquid.

3. A process as defined in claim 1 or claim 2 wherein said transfer of said vapour comprises subjecting said vapour to vacuum extraction or forced air propulsion.

4. A process as defined in any one of claims 1 - 3 comprising spraying said liquid onto said heated surface.

5. A process as defined in any one of claims 1 - 4 wherein said liquid is water.

6. A liquid purifier for purifying an impure liquid comprising thermoelectric module means having a heatable surface and a coolable surface; means for feeding said impure liquid to said heatable surface to produce vapour of said liquid; means for transferring said vapour to said coolable surface to effect condensation of said vapour to produce said purified liquid.

7. A liquid purifier comprising a housing having a first chamber and a second chamber; divider means separating said first and said second chamber one from the other; said divider means comprising a thermoelectric module having a heatable surface received within the first chamber and a coolable surface within the second chamber; means for feeding impure liquid to said heatable surface within said first chamber to produce liquid vapour; transfer means for transferring said liquid vapour to said coolable surface to effect condensation of said liquid vapour to produce purified liquid; and means for removing said purified liquid from second chamber.

8. A purifier as defined in claim 6 or claim 7 further comprising power means to activate said thermoelectric module.

9. A purifier for providing purified liquid from an impure liquid comprising - a thermoelectric module means comprising a heatable sink means and a coolable sink means; a first chamber which receives said heatable sink means; a second chamber which receives said coolable sink means; passage means between said first and second chambers to allow transfer of vapour from said first chamber to said second chamber for contact with said coolable sink means to effect condensation of said vapour; means for feeding said impure liquid to said heatable sink to produce vapour to produce said purified liquid; said thermoelectric module being adapted to receive an electric current to activate said module to heat said heatable sink means and cool said coolable sink means.

10. A purifier as defined in claim 9 wherein said module means comprises a pair of individual thermoelectric elements in a cascade arrangement to be thermally in series.

11. A purifier as defined in claim 9 or claim 10 comprising a wall member between said first and second chambers which retains thermoelectric module means.

12. A purifier as defined in any one of claims 9 - 11 wherein said thermoelectric module means comprises a plurality of single or double thermoelectric elements.

13. A purifier as defined in any one of claims 9 - 12 comprising a first thermoelectric module means having a first heatable sink means comprising a first plurality of planar sink members and a second thermoelectric module means having a second heatable sink means comprising a second plurality of planar sink members interleafed with said first plurality of planar sink members.

14. A purifier as defined in any one of claims 9 - 13 comprising one or more walls which defined said first chamber and one or more surfaces, wherein one or more of said walls comprise said thermoelectric module means to provide said heatable sink means on said one or more inner surfaces within said first chamber.

15. A purifier as defined in claim 14 wherein said walls define a rectangular chamber and having inner surfaces from each of said surfaces protrude a plurality of thermoelectric module means .

16. A purifier as defined in any one of claims 9 - 15 wherein said module means comprises liquid and vapour receiving members formed of a thermally conductive material.

17. A purifier as defined in claim 16 wherein said thermally conductive member comprises a plurality of planar members.

18. A purifier as defined in claim 16 or claim 17 wherein said thermally conductive material is selected from aluminum, copper, stainless steel and alloys thereof.

19. A purifier as defined in claim 11 wherein said wall member comprises a planar frame member which retains a plurality of said thermoelectric modules in coplanar arrangement one adjacent to another.

20. A purifier as defined in any one of claims 6 - 19 wherein said modules are thermally insulated one from another.

21. A method of cooling a fluid or mamtaining a fluid at a desired temperature below ambient comprising electrically activating a thermoelectric module to provide a cooled surface and contacting said fluid with said surface.

22. A method as defined in claim 21 wherein said fluid is a liquid.