EP1797374A1

EP1797374A1 - Apparatus for control of fluid temperature

Info

Publication number: EP1797374A1
Application number: EP05782841A
Authority: EP
Inventors: Paul Burns
Original assignee: World of Comforts Ltd
Current assignee: World of Comforts Ltd
Priority date: 2004-09-11
Filing date: 2005-09-12
Publication date: 2007-06-20
Also published as: CN101036027A; GB2433313B; US20080196861A1; GB0420200D0; JP2008512636A; GB2433313A; WO2006027619A1; GB0706693D0

Abstract

The present invention relates to a device for controlling the temperature of a fluid by heating and/or cooling. It has a reciprocating, displacement type pumping arrangement (12, 14) which propels fluid from an outlet (34) to an outlet (36) via a conditioning chamber (40, 40') in which fluid temperature control is carried out by means of a thermo-electric heat pump (50, 50') which is preferably of Peltier type.

Description

DESCRIPTION

APPARATUS FOR CONTROL OF FLUID TEMPERATURE

The present invention relates to devices for controlling the temperature of a

fluid by heating and/or cooling.

As used herein, the word "fluid" refers to both gases and liquids. There are

very many devices in which fluid temperature needs to be raised and/or lowered.

Examples include "white goods" such as freezers and washing machines; air-

conditioners in buildings or vehicles; and any number of industrial processes.

Conventional cooling units - in air-conditioners, refrigerators and freezers, for

example - rely upon compression followed by adiabatic expansion of a working

fluid. Freon is a suitable working fluid. This conventional technology is of course

enormously widely used and undeniably effective, but is subject to important

problems. The working fluids conventionally chosen for their effectiveness in the

compression/expansion cycle (often CFCs) are recognized as important greenhouse

gases. To dispense with their use would be ecologically desirable. It would also be

desirable to dispense with the pumping machinery required to pressurise the working

fluid.

While the present invention has potential applications in many fields, a

potentially important application relates to regulation of air temperature in air

conditioners. As used herein the term "air conditioner" refers to a device which

delivers a flow of air and has means for cooling and/or heating the air delivered.

Conventional air conditioning units typically work by adiabatic expansion of a working fluid, with the cooled working fluid being supplied to a heat exchanger over

which air is passed by a fan. Such conditioners are of course very widely used for

conditioning the air in buildings, vehicles etc, typically under thermostatic control

and with the additional facility for heating of the air when necessary.

However, conventional air conditioners are not ideally suited to certain

applications. They require both a fan for circulation of air and a pump acting upon

the working fluid. They can as a result create levels of noise and vibration which are

unacceptable in some applications, particularly those requiring a relatively small

throughput of air. In particular, there are applications in which it is desired to supply

a small flow of air to the immediate vicinity of a person, as in the case of climate

controlled bedding or seating. Such applications may involve circulation of

temperature conditioned air within a closed system. US 4853992 (YU) provides the

example of a seat cushion which is cooled/heated by means of air circulated through

an enclosed envelope forming the cushion itself. Alternatively the conditioned air

may be released into the person's environment providing conditioned air in his/her

immediate vicinity. In both cases the air-conditioning unit is typically mounted close

to the user, making it important to keep noise and vibration to a minimum.

As an alternative to cooling devices reliant upon adiabatic fluid expansion,

it is known to use solid state thermoelectric devices. The type of device of most

relevance for present purposes is also referred to as a "Peltier" device, and functions

as a heat pump. Widely available commercial examples of such devices are formed as a sandwich with two outer ceramic plates arranged around an array of small

Bismuth Telluride elements. When a DC current is applied to an arrangement of

these "heat pump pads", the device serves to pump heat from one plate to the other.

By arranging for sinking of heat from the plate to which heat is pumped, such devices

can be used to exert a cooling effect at the other plate. Solid state devices have

important advantages. They are compact and have no moving parts to create noise or

vibration. The direction in which heat is pumped between the devices' plates can be

reversed simply by reversing the DC current applied to them, and so the same device

can potentially be used in both heating and cooling.

French prior patent FR 2594668, (Chareire) discloses an air-conditioning

system for use when sleeping which uses a "Peltier - effect fresh air generator" to

supply air to an enclosure placed over the head of a sleeper. It appears to be reliant

upon a fan for circulation of air. GB990668 (Malaker Laboratories Inc.) concerns a

cryogenic system in which Peltier devices are used in a "cascade" to achieve very low

temperatures. Gas being cooled is circulated between compression and expander

cylinders, past the Peltier devices. JP4265482 (Kinoshita Masahiko et al) discloses

provision of Peltier elements with radiating fins in an air passage to cool air entering

a cylinder. EP0672831 (Isco) relates to an apparatus for supercritical fluid extraction

which uses a thermoelectric element to cool a pumping arrangement. US 5242403

discloses a metering pump for dispensing volatile anaesthetic liquid. The arrangement

has a piston/cylinder arrangement which is cooled by a Peltier device, and also has a separate reservoir cooled by a further Peltier device.

There are examples in this prior art of devices which use reciprocating pumps

to provide throughput of fluid. In these, the Peltier device cools the pump cylinder

in order to cool the fluid being pumped. The interior wall of the cylinder is

necessarily smooth and does not provide an ideal means for heat exchange with the

fluid.

In accordance with a first aspect of the present invention there is a device for

controlling fluid temperature, comprising a fluid inlet, a fluid outlet, and a

reciprocating, displacement type pumping arrangement which is arranged to draw the

fluid in through the inlet and to exhaust it through the outlet, wherein the pumping

arrangement communicates with one of the inlet and the outlet via a conditioning

chamber through which the fluid passes on its way from the inlet to the outlet and in

which fluid temperature control is carried out, the device further comprising at least

one solid state thermo-electric heat pump having a first side which is thermally

coupled to fluid within the conditioning chamber and a second side which is arranged

to transmit heat to a sink or to receive heat from a source, so that by means of the

thermo-electric heat pump the temperature of the conditioning chamber wall, and of

the fluid within the conditioning chamber, is controllable.

Using the pumping arrangement to propel fluid through a separate

conditioning chamber makes it possible to form the interior of this chamber in a

manner which promotes exchange of heat with the fluid. The interior of the conditioning chamber may be shaped to provide a high surface area for heat

exchange.

A preferred embodiment comprises shaped heat exchange features within the

conditioning chamber having surfaces exposed to fluid within the conditioning

chamber to exchange heat with it the fluid, the heat exchange features also being

thermally coupled to the conditioning chamber wall to exchange heat with that. The

features in question promote heat exchange between the fluid and the thermo-electric

heat pump. They may comprise fins. It is preferred that they are integrally formed

with the conditioning chamber wall.

The pumping arrangement preferably has a cylinder and a reciprocating

piston.

In a constructionally convenient embodiment, the cylinder is circular and the

conditioning chamber is a substantially annular or semi-annular space around and

concentric with the cylinder.

The conditioning chamber wall may be disposed around at least part of the

cylinder, the conditioning chamber being defined between an outer surface of the

cylinder and an inner surface of the conditioning chamber wall.

Where the device is to be used for cooling, it preferably comprises a heat sink

arranged to receive heat from the second side of the thermo-electric heat pump. In

one such embodiment the heat sink forms a shell surrounding the conditioning

chamber wall. In a particularly preferred embodiment of the present invention, the cylinder

is divided by the piston into first and second working chambers so that piston motion

in one direction causes fluid to be drawn into the first working chamber and to be

exhausted from the second working chamber, and piston motion in the opposite

direction causes fluid to be exhausted from the first working chamber and to be

drawn into the second working chamber, the unit further comprising a valve

arrangement which selectively connects whichever working chamber is at any

moment exhausting fluid to the pump outlet, thereby providing mono-directional

flow through the outlet.

Preferably each working chamber communicates with a respective one-way

valve which is arranged to exhaust fluid from the chamber and is connected to the

outlet. Still more preferably, each chamber additionally communicates with a

respective one-way valve which is arranged to let fluid into the chamber.

In principle both working chambers could feed a single conditioning chamber.

Preferably, however, the device comprises first and second conditioning chambers

which are communicable respectively with the first and second working chambers

within the cylinder.

Conveniently, the first and second conditioning chambers may together form

an annulus surrounding the cylinder. This can be achieved through a construction in

which the first and second conditioning chambers are both defined between the

cylinder and the conditioning chamber wall. A reciprocating pump might be expected to cause a high level of vibration,

but in fact for applications in which fluid throughput requirements are relatively

small, and given sufficient working volume within the pump, the velocity of the

reciprocating components of the pump and the frequency of their motion can be small

enough to create a low level of vibration and noise.

In accordance with a second aspect of the present invention there is a fluid

cooling device comprising a reciprocating, displacement type pump which is arranged

to circulate fluid mono-directionally from an inlet to an outlet via at least one cooling

chamber, and at least one solid state thremo-electric heat pump associated with the

cooling chamber to cool the fluid as it passes through the cooling chamber.

Specific embodiments of the present invention will now be described, by way

of example only, with reference to the accompanying drawings, in which :-

Figure 1 is an axial, and somewhat schematic, section through a fluid

temperature control device constructed in accordance with the present invention;

Figure Ia is a radial, and again somewhat schematic, section through the

device shown in Figure 1 ;

Figure 2 is an exploded view of the major components of a further fluid

Figure 3 shows a section through the device seen in Figure 2, taken in an axial

plane;

Figure 4 shows a section through the same device, taken in a radial plane; Figure 5 is a perspective view of the exterior of the same device;

Figure 6 shows an end plate of the same device in plan; and

Figure 7 shows a section through a ball valve used in the device, taken in an

axial plane.

Figure 1 is a somewhat simplified view of a device embodying the present

invention which will serve to illustrate some of the relevant principles. The device

10 is self-contained, incorporating both a pump to circulate the fluid and heat

exchange devices used to condition it.

The pump is of reciprocating displacement type, having a piston 12 which is

received in a cylinder 14 with which it forms a sealed but sliding fit. The piston is

reciprocally driven at low speed by means of a lead screw 16 which extends through

the cylinder and is journalled at opposite ends of it in respective end caps 18, 20. An

electric motor 22 drives the lead screw 16 through gearing. In the present

embodiment the direction of movement of the piston 12 is reversed, when the piston

reaches the end of its travel, by reversing the direction of rotation of the motor 22.

Suitable means for achieving this, eg by provision of a pair of micro switches

arranged to be actuated by the piston when it reaches respective ends of its travel and

connected to motor control electronics, will be apparent to the skilled person. The

lead screw is received in an axial, through-going, threaded bore in the piston 12 by

virtue of which its rotational motion is converted to linear piston motion. Of course

the piston 12 must be prevented from rotating along with the lead screw but friction between the piston and cylinders is typically sufficient to ensure this. It will be

apparent to the skilled person that other means of reciprocally driving the piston, e.g.

using a crank or eccentric drive, could be adopted in other embodiments.

The pump is required to provide a flow of air which is mono-directional,

despite reversal of the direction of piston movement. The piston divides its cylinder

14 into a pair of working chambers 26, 26'. Communicating with each working

chamber is a pair of one-way valves 30, 32 and 30' 32'. The two valves

communicating with a given working chamber are oppositely orientated. That is, one

valve of the pair is arranged to let air into the relevant working chamber and the other

is arranged to exhaust air from it. The two inlet valves 30, 30' are connected to a

common air input of the air conditioning unit, schematically represented at 34. The

two exhaust valves 32, 32' are connected to a common air exhaust of the device,

schematically indicated at 36. Regardless of the direction of piston motion, there is

always one working chamber 26 or 26' exhausting air through the common exhaust

36 and its exhaust valve 32 or 32' while the other chamber 26' or 26 receives air

through the common inlet 34 and its valve 30', 30. In this way the valves ensure a

mono-directional and (save for the brief times in its reciprocating motion when the

piston is stationary) continuous throughput of fluid. However in other embodiments

the two inlets and the two outlets need not be connected together. They could instead

lead to different fluid sources and/or points of usage. Fluid recirculation from outlet

to inlet could be provided, particularly to allow the fluid to go through multiple cooling phases to reach especially low temperatures.

Note that the cylinder 14 is contained within a cylindrical outer housing 38,

and that the path for inlet of fluid through the inlet valve 30 to the working chamber

26 is via a semi-annular chamber 40 defined between the cylinder 14 and the housing

38. Likewise the path for inlet of fluid through the inlet valve 30' to the working

chamber 26' is via a semi-annular chamber 40'. The two semi-annular chambers 40,

40' extend along the cylinder's length and are separated by longitudinal dividing

walls 42, 44 which are seen in Figure 2 to lie in a common plane containing the

cylinder axis. As a result of this arrangement the inlet valve 30 which supplies

working chamber 26 is at the far end of the cylinder from that chamber, and likewise

inlet valve 30' is at the far end of the cylinder from the working chamber 26' which

it supplies.

The semi-annular chambers 40, 40' may be referred to as "conditioning

chambers" because it is within them that conditioning of the fluid by cooling and/or

heating is carried out, by means of solid state thermoelectric devices 50, 50'. Within

both of the chambers 40, 40' is a respective set of such devices, the devices within a

given chamber being connected to a common electrical supply/control. The devices

are arranged in semi-circular fashion within the conditioning chambers. Residence

time of air in the vicinity of the thermoelectric devices is high due to the chambers'

length and the relatively low air throughput Thermostatic control, based for example

on the temperature of output air, may be exercised over the thermoelectric devices' electrical supply. By reversing the DC supply applied to the devices, the unit can be

caused to warm the air rather than cooling it. A thermistor in a pump working

chamber or in its outlet may be used to sense output air temperature.

Figures 2 to 7 show a second physical embodiment of the present invention

in greater constructional detail. Many of the major components of this embodiment

have counterparts in the device of Figures 1 and Ia, and the same reference numerals

are used for these components throughout. In the second embodiment piston 12 is

once more driven through lead screw 16 by electric motor 22. It is also prevented

from rotating due to friction with the screw by a guide rod 100 which passes through

the piston, forming a sealing fit with it. Cylinder 14 carries dividing walls 42, 44,

which lie on opposite sides of the piston and in a common axial plane. In the present

embodiment the conditioning chambers 40, 40' are formed by means of a pair of

semi-annular shells 102, 102' positioned around the cylinder. These shells are

formed of thermally conductive material, metal being favoured. They each have a

conditioning chamber wall portion 104, 104" carrying on its radially outer face a

respective bank of solid state thermo-electric heat pump devices 50, 50' of Peltier

type. Radially inner faces of each wall portion 104, 104' are provided with features

serving to promote exchange of heat with the fluid in the respective conditioning

chamber. Such features serve to increase the surface area available for heat

exchange, as compared with the case of a smooth cylindrical face. In the present

embodiment they take the form of fins 106,106' which are integrally formed with the chamber walls 104, 104' and which extend along the axial direction, the effect is to

create, within each conditioning chamber, a set of narrow passages for throughput of

fluid, within which heat exchange is promoted.

Where the device is used for cooling, heat passes from the fluid to the

conditioning chamber walls 104, 104 \ whence it is pumped by the heat pump devices

50, 50\ which are mounted upon, and thermally coupled to, the chamber walls. To

dissipate this heat, the device's outer casing is formed as a heat sink. This casing is

constructed in two casing halves 108, 108" and assembled around the semi-annular

shells 102, 102" forming the conditioning chamber. Its innermost face 110 is

cylindrical and its outer surface is formed by a set of fins 112, 112' which provide

surface area for exchange of heat with the atmosphere. If necessary a fin may be used

to provide air flow over the fins.

A route is required for conduction of heat from the outermost pads of the heat

pump devices 50, 50" to the external heat sink, and this is provided in the present

embodiment by means of semi-annular conduction shells 114, 114" whose radially

inner faces are thermally coupled to the outermost faces of the heat pump devices.

The conduction shells carry on their radially outer faces integral conduction vanes

116, 116", formed in the present embodiment as circumferentially extending rings,

which serve to conduct heat to the casing halves 108, 108' forming the heat sink.

The flow of air into, out of, and between chambers of the device is provided

for by means of recesses in end plates 18, 20, one of which is shown on its own in Figure 6. Through-going, axially directed bores 120, 120" provide for inlet of fluid

to the respective cylinder working chambers (see Figure 3) and receive one-way

valves (which are omitted from Figure 3, but will be described below. A conduit

connecting each working chamber 26, 26^Λ in the cylinder to its associated

conditioning chamber is needed, and this is provided by virtue of a semi-circular

recess 124 formed in the end plate and positioned to communicate with the respective

chambers. Fluid outlet from the conditioning chambers is through "C" shaped recess

130 which is positioned to communicate only with the relevant conditioning

chamber, and a radial bore 132 leading from it, which threadedly receives a one-way

outlet valve (not shown in Figure 6 but seen in Figure 7). The end plates 18, 20 are

formed from thermally insulating material, specifically plastics, to minimise heat

transfer from the outer heat sink 108, 108' to the inner components.

For the sake of completeness, Figure 7 shows a suitable one-way valve

although its construction is conventional and of course the skilled person is aware of

numerous other suitable valving arrangements. The valve 140 has a ball 142

captively housed in a hollow circular valve housing 144 providing a valve inlet 146

and outlet 148. The ball is able to move back and forth between a valve seat 150,

against which it forms a seal when necessary to prevent back-flow of fluid, and a stop

shoulder 152, against which the ball can rest without preventing forward fluid flow.

The illustrated device is well suited to serving as an air conditioning unit, in which case the conditional air it emits may be supplied to a climate controlled bed

or seat. The input air may come from the general environment or alternatively air

may be recirculated from the bed or seat. The invention is also applicable to the field

of refrigeration. The cooled air output from the conditioning unit described above

may be fed to a cabinet of a refrigerator, freezer, cooler, and chiller cabinet etc. to

provide the necessary cooling effect. Alternatively the same general construction

described above and depicted herein could be used for a device used in cooling a

liquid or gaseous working fluid to be supplied to the heat exchanger of a refrigerated

cabinet. The device's inlet and outlet would be connected to the heat exchanger and

circulate working fluid through it.

In fact devices embodying the present invention have a wide range of possible

applications. Water cooling is one such. A filter maybe placed in the fluid flow path

to remove foreign bodies such as water contaminants. Electrolysis could be carried

out upon the fluid within the device, at controlled temperature. In re-processing of

Uranium there is a requirement for fluid temperature regulation and the device is

potentially applicable in this context.

Claims

1. A device ft* controlling fluid temperature, comprising a fluid inlet, a fluid outlet,

and a reciprocating, displacement type pumping arrangement which is arranged to

draw the fluid in through the inlet and to exhaust it through the outlet, wherein the

pumping arrangement communicates with one of the inlet and the outlet via a

conditioning chamber through which the fluid passes on its way from the inlet to the

outlet and in which fluid temperature control is carried out, the device further

comprising at least one solid state thermo-electric heat pump having a first side which

is thermally coupled to fluid within the conditioning chamber and a second side

which is arranged to transmit heat to a sink or to receive heat from a source, so that

by means of the thermo-electric heat pump the temperature of the conditioning

chamber wall, and of the fluid within the conditioning chamber, is controllable.

2. A device as claimed in claim 1, comprising shaped heat exchange features within

the conditioning chamber having surfaces exposed to fluid within the conditioning

thermally coupled to the thermo-electric heat pump to exchange heat with that.

3. A device as claimed in claim 1 or claim 2 wherein the conditioning chamber has

a thermally conductive wall whose interior is exposed to the fluid, the thermo-electric

heat pump being mounted to and thermally coupled to the exterior of said conditioning chamber wall.

4. A device as claimed in claim 2 wherein the heat exchange features comprise fins.

5. A device as claimed in claim 4 wherein the heat exchange features are integrally

formed with the conditioning chamber wall.

6. A device as claimed in claim 4 or claim 5 wherein the fins extend along a fluid

flow direction within the conditioning chamber.

7. A device as claimed in any preceding claim wherein the pump comprises a piston

and a cylinder.

8. A device as claimed in claim 7 wherein the cylinder is circular and the

conditioning chamber is a substantially annular or semi-annular cavity around and

concentric with the cylinder.

9. A device as claimed in claim 7 or claim 8 wherein the aforementioned thermally

conductive conditioning chamber wall is disposed around at least part of the cylinder,

the conditioning chamber being defined between an outer surface of the cylinder and

an inner surface of the conditioning chamber wall.

10. A device as claimed in any preceding claim, further comprising a heat sink

arranged to receive heat from the second side of the thermo-electric heat pump.

11. A device as claimed in any of claims 7, 8 or 9 further comprising a heat sink

which is arranged to receive heat from the second side of the thermo-electric pump

and which forms a shell surrounding the conditioning chamber wall.

12. A device as claimed in any of claims 7, 8, 9 or 11 wherein the cylinder is divided

by the piston into first and second working chambers so that piston motion in one

direction causes fluid to be drawn into the first working chamber and to be exhausted

from the second working chamber, and piston motion in the opposite direction causes

fluid to be exhausted from the first working chamber and to be drawn into the second

working chamber, the unit further comprising a valve arrangement which selectively

connects whichever working chamber is at any moment exhausting fluid to the pump

outlet, thereby providing mono-directional flow through the outlet.

13. A device as claimed in claim 12, wherein each working chamber communicates

with a respective one-way valve which is arranged to exhaust fluid from the chamber

and is connected to the outlet.

14. A device as claimed in claim 13 wherein each chamber additionally communicates with a respective one-way valve which is arranged to let fluid into the

chamber.

15. A device as claimed in any of claims 12 to 14, comprising first and second

conditioning chambers which are communicable respectively with the first and

second working chambers within the cylinder.

16. A device as claimed in claim 15 wherein the first and second conditioning

chambers together form an annulus surrounding the cylinder.

17. A device as claimed in claim 16 wherein the first and second conditioning

chambers are both defined between the cylinder and the conditioning chamber wall.

18 A device as claimed in claim 17 wherein the first and second conditioning

chambers are separated from each other by a dividing wall in a plane containing the

cylinder axis.

19. A device as claimed in any preceding claim, wherein the pumping arrangement

comprises a lead screw which threadedly engages with the piston in order to

reciprocally drive it.

20. A device as claimed in any preceding claim which is an air conditioning device.

21. A bed or a seat comprising an air conditioning device as claimed in claim 20.

22. A refrigeration unit provided with a device according to any of claims 1 to 19.

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