This invention relates to energy transfer apparatus. More particularly, this invention relates to heat pipes.

Air-conditioning, refrigeration carried out using vapour compression systems which are powered by mains electricity generated by large plants. Current technology limits these power stations to a maximum efficiency of about 40%. The electricity is then transported via the national grid and eventually arrives at the point of use. There is only about 35% of the original energy left at this point. This means that vast quantities of fossil fuels have been burnt with unwanted pollutants (e.g., CO,, NO _^ ) entering the atmosphere. The coefficient of performance of vapour-compression systems is low when the inefficiencies of electrical power generation are taken into account.

In order to minimise emissions of pollutants, it is possible to use renewable energy sources such as solar energy to drive air-conditioning and refrigeration plants. This reduces the environmental impact and offers savings in running cost to users, there will be increasing pressure to use renewable energy sources and it is in the immediate interest of the UK to identify and develop technologies which can harness these sources to reduce our independence on fossil fuel combustion. However, the problems with photovoltaic technology are low efficiency and high capital cost and also solar energy is not always available some means must be incorporated to store surplus electricity and release- it again when it is needed.

According to one aspect of this invention there is provided energy transfer apparatus comprising a pipe having first and second regions, a heat transfer fluid adapted to circulate about said pipe to transfer heat from the first region to the second region, and energy transfer means arranged between the first and second regions, said energy transfer means being operable by or on said fluid to transfer energy to or from said apparatus.

The energy transfer means may comprise refrigeration means adapted to extract heat from an area external to the pipe, thereby causing a refrigerating effect to said area.

The first region may be a first end region, and the second region may be a second end region of the heat pipe. Preferably, the fluid is a refrigerant. The first end region may be in the form of a generator to which heat can be supplied to evaporate the heat transfer fluid. The second end region may be in the form of a condenser from which heat can be extracted on condensation of the heat transfer fluid.

The refrigeration means may comprise an evaporator mounted externally of the pipe, and may include vapour expansion means communicating with the evaporator. The vapour expansion means may be adapted to expand vapour from the first region to the second region of the pipe. In one embodiment, the vapour expansion means comprises an ejector conveniently having an inlet or primary nozzle, a central region and an outlet, or diffusers wherein the inlet nozzle is adapted to receive vapour from the first region, the central region is in communication with the evaporator, whereby vapour passing from the first region to the central region entrains vapour from the evaporator, and combined vapour from the first region and from the evaporator is exhausted from the outlet of the ejector into the second region of the pipe.

In another embodiment, the refrigeration means comprises a first ejector provided in the pipe, and a second ejector in communication with the first ejector. Each ejector may have an inlet or primary nozzle, an outlet or diffuser and a central region. Preferably, the outlet of the second ejector is in communication with the central region of the first ejector. Preferably, the evaporator is in communication with the central region of the second ejector. A diversion line may extend from the first region of the pipe to the inlet region of the second ejector whereby vapour from the first region can be diverted to the second ejector. Thus, vapour from the first region is passed through the diversion line to the second ejector which entrains vapour from the evaporator as the diverted vapour passes through the second ejector. In this embodiment,

the vapour passing through the first ejector entrains vapour from the second ejector, wherein the combination of vapour from the inlets to the first and second ejectors, and the evaporator is passed out of the first ejector into the second region of the pipe.

Condensate transport means may be provided to transport condensed fluid from the second region to the first region. The transport means may comprise a wicking means provided around the inner circumference of the pipe.

Alternatively, the transport means may comprise a conduit, which may be of annular cross-section, provided around the inner circumference of said pipe. In this embodiment, the pipe is arranged to slope downwardly from said second region to said first region to enable the condensed fluid to return by gravity along said conduit to the first region.

In another embodiment, the pipe may be rotatable about a longitudinal axis thereof, and may be substantially frusto-conical, being of a larger diameter at the first region, and a lesser diameter at the second region, whereby rotation of the pipe causes condensed fluid to return to the first region along the conduit by centrifugal force.

In an another embodiment, the pipe may be substantially cylindrical and the transport means may be in the form of a tube, wherein the pipe is rotatable about a longitudinal axis, and holding means may be provided to hold the transport means stationary during rotation of the pipe. In this embodiment, the second region may comprise a reservoir into which condensed fluid can be retained, and the transport means may include a pick-up means, which may be in the form of a pipe, extending from the tube to collect condensed fluid from the reservoir. The holding means may comprise a weight mounted on the pick¬ up means.

In an another embodiment, the transport means may comprise an external wick fed by a line, preferably an external line, from the second region. In this embodiment, the wick may comprise a metal tube housing a sintered

powder which may be a metal. Preferably, the metal is copper. Alternatively, the wick may be of a composite structure comprising an outer region of a powder, preferably copper or phosphor bronze, which may have a particle size of 50 to 250 microns, preferably 150 to 200 microns. The wick may further include an inner region which may have a particle size of 5 to 75 microns preferably 50 to 60 microns.

In an another embodiment, the heat pipe may be of a stepped construction, with the first region being in the form of a cylinder having a first diameter, and the second region being in the form of a cylinder having a second diameter, wherein the first diameter is greater than the second diameter. The return means may be in the form of feed lines, for example, tubes extending from the second region to an outer portion of the first region. The pipe of this embodiment may be rotatable about a longitudinal axis whereby condensed heat transfer fluid is returned from the second region to the first region by a centrifugal force. One way valves may be provided in the heat transfer fluid feed lines to prevent heat transfer fluid returning along said lines from the first region to the second region.

In each of the above embodiments, evaporator feed means is provided to extract some of the condensed heat transfer fluid from the transport means or from the second region to feed heat transfer fluid to the evaporator. Preferably, the evaporator feed means comprises a capillary line. Expansion means may be provided in said evaporator feed means to feed the heat transfer fluid to the evaporator at relatively low pressure.

In an another embodiment, the refrigeration means includes an evaporator and an absorber or adsorber, wherein heat transfer fluid from the second region of the pipe is passed to the evaporator for evaporation. Means for feeding the absorber or adsorber may be provided to feed heat transfer fluid vapour from the evaporator to the absorber or adsorber, wherein vapour from the absorber or adsorber is entrained by the ejector, and a concentrated solution of the heat transfer fluid and absorbent or adsorbent is passed to the first region of the pipe wherein the heat transfer fluid is evaporated and a

dilute solution of the fluid and absorbent or adsorbent is passed back to the absorber or adsorber.

Compression means may be provided at the second region of the pipe to compress the heat transfer fluid passing thereto from the refrigeration means. The compression means may include recycling means to recycle refrigerant compressed thereby to the evaporator. The recycling means may include heat exchange means, preferably in the form of a condensor coil, to heat the heat transfer fluid at the first region. Preferably, the compression means is adapted to be driven by an external power source.

A further evaporator may be provided in the pipe between the first end region and the ejector. Preferably, a condensor is also provided, whereby fluid evaporated at the first end region is passed to the further evaporator. Preferably, the condensor is provided via the condensor.

The recycling means may be in communication with the further evaporator to pass fluid to the further evaporator downstream of the condensor coil.

Heating means may be provided at the first region to supply heat thereto. In one embodiment, the first region may be provided with first heat exchange means, which may be in the form of fins, in order to extract heat from a heating fluid passing across the first region externally of the piping. Alternatively, the first heat exchange means may be in the form of fibres or filaments extending outwardly therefrom to extract heat from the surroundings. In the case of rotating heat pipe, the fibres or wires may be rotated with the heat pipe to act as a fan, thereby increasing the efficiency of heat transfer to the first region, the fibres or filaments are preferably formed of a suitable high heat conducting material such as a metal, for example copper.

The heating fluid may, for example, be hot water, air or steam. Alternatively, the heating means may be in the form of a solar collector applied ro the first region. The heating means may also, or alternatively, include a

burner to apply heat to the first region. The burner may be a gas or oil burner, or may be a burner of any other suitable fuel. The solar collector is preferably applied to one side of the first region, extending substantially 50% around the circumference of the first end region. The apparatus may comprise an array of said pipes. Each pipe being provided with a concentrator to concentrate the solar energy onto the solar collecting means. Each concentrator may be in the form of a lens or mirror.

The refrigeration means may comprise heat extraction means in order to extract heat from the surroundings thereof. The heat extraction means may comprise fins. Fluid from which heat is to be extracted may be passed over the refrigeration means, the fluid being suitable liquid, such as water, or a gas, for example, air.

Second heat exchange means may be provided at the second region of the conduit, to facilitate removal of heat from the second end region. The second heat exchange means may be in the form of fins. Alternatively, the second heat exchange means may be in the form of fibres or filaments, extending outwardly from the second region. In the case of a rotating heat pipe, the fibres or wires may be rotated with the heat pipe to act as a fan, thereby increasing the efficiency of heat transfer from the second region. The fibres or filaments are preferably formed of a suitable high heat conducting material such as a metal, for example copper. Cooling fluid may be passed over the second region to extract heat therefrom, and to cool the heat transfer fluid vapour in the second region. The cooling fluid may be in the form of a suitable liquid, such as cold water, or a gas, such as air.

In another embodiment, the refrigeration means comprises compression means and an evaporator, wherein heat transfer fluid in the evaporator is evaporated and passed to a compressor to compress the refrigerant. Preferably, the compression means comprises drive means to drive the compressor. Preferably, the drive means is adapted to be driven by the vapour from the first region. Preferably, the drive means comprises a turbine fixedly connected to the compressor. In one embodiment, the compressor is a rotary compressor

whereby rotation of the turbine by heat transfer fluid passing therethrough from the first end region causes rotation of the rotary compressor.

In a further embodiment, the energy transfer means comprises work extraction means adapted to extract work from the pipe. The work extraction means may comprise a turbine adapted to be driven by heat transfer fluid passing therethrough from the first end region to the second end region. The work extraction means may be fixedly connected to an electricity generator, suitably an alternator, for generating electric power. The work extracrion means may be an alternator. Preferably, a shaft extends from the work extraction means to the electricity generator, whereby evaporation of the work extraction means operates the generator to produce electric current.

An absorber or adsorber may be arranged at the second region of the pipe. The work extraction means may be in the form of a turbine adapted to drive a shaft connected to an alternator to generate electricity. Transport means may be provided to return to the first region a combination of absorbent or adsorbent and heat transfer fluid. The transport means may be in the form of wicking means.

Feed means may be provided to feed to the absorber or adsorber the absorbent or adsorbent from which heat transfer fluid has been evaporated at said region.

In another embodiment, the first end region may constitute the evaporator to extract heat from the surroundings, and create a refrigerating effect at said first end region, preferably via heat exchange means which may be in the form of fibres or filaments.

A generator may be provided around a central region of the pipe to which heat can be supphed via an external source to evaporate the heat transfer fluid therein.

The first end region may be provided with said first heat exchange

means whereby evaporation of heat transfer fluid at said first end region causes heat to be extracted from said first end region, via said first heat exchange means. The first heat exchange means may be in the form of fibres or filaments.

Said second heat exchange means may be provided at the second end region. The second heat exchange means may be in the form of fibres or filaments.

The heat pipe may be a rotating heat pipe, whereby on rotation the fibres or filaments of the first and second heat exchange means cause a fanning effect to enhance heat transfer.

In another embodiment, compression means may be provided in the central region of the heat pipe, operable on the fluid circulating therein, whereby the first end region may constitute an evaporator such that compression of the fluid by the compression mans causes fluid at the first end region to evaporate to create a refrigerating effect at said first end region.

Preferably, the first and second regions are provided with first and second heat exchange means which may be in the form of said plurality of fibres or filaments.

The compression means may be accompanied by an ejector means and a further evaporator whereby the ejector is arranged in the heat pipe between the compression means and the first region thereof. The ejector and the further evaporator are preferably so arranged that said heat transfer fluid from said first end region is passed through the ejector to entrain said fluid from said further evaporator, whereby heat may be extracted from the surroundings to said first end region by evaporation at said first end region and at said further evaporator.

According to another aspect of the invention, there is provided heat transfer apparatus comprising a pipe having first, second and third regions, the

first region being arranged intermediate the second and third regions, the heat transfer fluid adapted to circulate about said pipe to transfer heat from the first region to the second and third regions, refrigeration means arranged between the first and second regions, operable by the circulation of said fluid to extract heat from a region external of said pipe, and work extraction means arranged between the first region and the third region operable by the circulation of said fluid to transfer energy from said pipe.

The heat pipe may comprise the features of any of the heat pipes described in the above paragraphs. For example the heat pipe may comprise the features of the cylindrical or the conical or stepped heat pipes described above and may be rotatable or non-rotatable.

The refrigeration means may comprise the features of any of the refrigeration means described in the above paragraphs.

The work extraction means may comprise the features of any of the work extraction means described in the above paragraphs.

According to another aspect of this invention, there is provided heat transfer apparatus comprising a heat pipe having first and second regions and a plurality of fibres or filaments extending from the first and second end regions.

Preferably, the first and second regions are respective first and second end regions of the heat pipe. The fibres or wires are preferably flexible metal fibres or wires.

In an embodiment , the heat pipe is rotatable and the fibres or wires are preferably rotatable therewith.

Fluid supply conduit arrangements may be provided to supply fluid to the first and second regions. Preferably, a first fluid supply conduit arrangement is provided ro supply relatively hot fluid to the first region for heat to be extracted therefrom to heat said first region. A second fluid supply

conduit arrangement is preferably provided to supply relatively cold fluid to the second region thereby to remove heat therefrom.

The heat transfer apparatus described in the above four paragraphs may include any of the features of the energy transfer apparatus in the above description commencing at paragraph 5.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figs. 1 to 7, 11, 12, 13, 13A, 14, 14a, 15 to 22 and 24 to 30 show schematic sectional views of different embodiments of energy transfer apparatus;

Fig. 8 shows a wick for use in the embodiment shown in Fig. 7;

Fig. 8A shows an example of a wick structure suitable for use in the wick shown in Fig. 8;

Fig. 9 shows a further wick structure;

Fig. 10 is a schematic sectional view of an array of heat pipes;

Fig. 23 shows an arrangement incorporating the embodiment shown in Fig. 22;

Fig. 2 shows an arrangement incorporating the embodiment shown in Fig. 24.;

Fig. 26 shows an end view of the arrangement shown in Fig. 25;

Fig. 27 shows a further embodiment of heat transfer apparatus;

Fig. 28 shows a heat pipe suitable for use in the embodiment shown in Fig. 27;

Fig. 29 shows an application of the apparatus shown in Fig. 27.

Referring to Fig. 1 there is shown energy transfer apparatus 10 which comprises a heat pipe 12 in the form of a hollow tube which may have a circular cross-section, but it will be appreciated that the tube can have any appropriate cross-sectional shape. The heat pipe 12 comprises a wall 14 defining an inner space 16.

The heat pipe 12 is sealed at opposite ends 18,20 and a wick 22 is

disposed adjacent to the wall 14, the purpose of which will be explained below.

A heat transfer fluid in the form of a refrigerant 15 is introduced into the heat pipe 12. Any suitable refrigerant known to persons skilled in the art can be used.

The heat pipe 12 is divided into a first region 24 at one end, the first region comprising a generator for generating refrigerant vapour by evaporation of liquid refrigerant in the wick 22, a second region 26 at the opposite end, comprising a condenser for condensing the refrigerant vapour, and an intermediate region 28 in which an ejector 30 is disposed as will be explained below.

In operation, heat (Qg) is applied to the first end region 24 to evaporate the refrigerant at the first end region 24. The vapourised refrigerant travels in the direction of the arrows A through the space 16 along the inside of the pipe 12 through the central region 28 to the second end region 26. The vapourised refrigerant condenses at the second end region 26. The refrigerant condenses onto the wick 22 and is then transported by capillary action through the wick 22 to the first end region 24 in the direction of the arrows B to be evaporated and then begins the sequence again.

The evaporation of the refrigerant at the first end region 24 causes heat to be absorbed by the refrigerant (Qg), and the condensation of the refrigerant at the second end region 26 causes heat to be given up by the refrigerant (Qc). Thus, heat is transferred from the first end region 24 to the second end region 26.

A first and second set of fins 52,54 can be provided at the first and second end regions 24,26 to assist the transfer of heat.

The ejector 30 disposed in the intermediate region 28 comprises a primary nozzle 32 having a narrow inlet bore 34 through which high pressure refrigerant vapour 1 can pass into a central region 36, which communicates with an evaporator 57 comprising a reservoir 58 containing low pressure

refrigerant 15 via an inlet aperture 38. A third set of fins 56 is provided at the reservoir 58 to assist heat transfer at the reservoir 58.

A mixing tube 40 extends from the central region 36 to a diffuser 42. A funnel means 44 is provided on the mixing tube 40 at its end inside the central region 36. The diffuser 42 tapers outwardly from the mixing tube 40.

High pressure refrigerant vapour 15 passing through the narrow bore 34 from the first end region 24 exits therefrom in the central region 36 at high velocity to cause the low pressure refrigerant in the evaporator 57 to be evaporated and drawn in the direction indicated by the arrow C towards the funnel means 44.

The vapour and the evaporated fluid are mixed in the mixing tube 40 and ejected via the diffuser 42 to the second end region 26.

The evaporation of the refrigerant 15 from the evaporator 57 extracts heat of evaporation (Qe) from the surrounding atmosphere via the fins 56 thus creating a refrigerating effect, which can be used for example for air conditioning, in a refrigerator or in a freezer.

The mixed vapour ejected from the diffuser 42 condenses at the second end region 26 giving up heat of condensation (Qc) which is passed to the surroundings via the fins 54, for example by passing a cooling fluid over the fins. Some of the condensed refrigerant is transported by the wick 22 to the first end region 24 where it is evaporated to begin the cycle again.

A capillary tube 62 is connected between the reservoir 58 and the wick 22 at the second end region 26 so that some of the condensed refrigerant can be passed to the reservoir 58 for re-evaporation by the passage of high velocity vapour through the ejector 30.

Fig. 2 shows another embodiment. In Fig. 2, the features which are the same as those shown in Fig. 1 are designated with the same reference numeral.

The energy transfer apparatus shown in Fig. 2 is generally the same as that shown in Fig. 1, with the exception that the apparatus includes a second ejector

30A in addition to the first ejector 30 shown in Fig. 1. The evaporator 57 is connected to the second ejector 30A.

The second ejector 30A is generally the same as the first ejector 30, and comprises a nozzle 32A having a narrow inlet bore 34 through which high pressure refrigerant vapour is fed via the line 35A in the direction of the arrow Al, from the conduit 12. The refrigerant vapour 15 passes out of the nozzle 34A to mix with refrigerant evaporated from the evaporator 57. The mixture of refrigerant then passes via funnel means 44A to a mixing tube 40A, and a diffuser 42 A in the direction of the arrow Cl to an intermediate region of the ejector 30 between the nozzle 32 and the mixing tube 40.

Thus, refrigerant from the second ejector 30A is mixed with refrigerant passing through the first ejector 30 to be passed into the second end region 26 of the conduit 12, whereupon the refrigerant condenses giving up heat (Qc) to the atmosphere via the fins 54. The condensed refrigerant 15 passes via the wick 22 towards the first end region 24 of the conduit 12. Some of the refrigerant 15 is diverted from the wick 22 via a line 60A through an expansion valve 62 A to the evaporator 58 A. The refrigerant in the evaporator 57 is under low pressure and, upon entering the evaporator 57, the refrigerant 15 evaporates extracting heat (Qe) from the surroundings thereby causing a refrigerating effect. The evaporated refrigerant passes out of the evaporator 57 in the direction of the arrow Dl to a region of the ejector 30A between the nozzle 32A and the mixing tube 40A to be mixed with refrigerant passing through the bore 34A from the first end region 24 of the conduit 12.

The pressure in the second ejector 30A will be lower than the pressure in the first ejector 30. Hence, the evaporator temperature of the embodiment shown in Fig. 2 will be much lower than for the apparatus shown in Fig. 1.

Fig. 3 shows a further embodiment to the embodiment shown in Fig. 1. The embodiment shown in Fig. 3 comprises many of the features of those

shown in Fig. 1, and these have been designated with the same reference numeral.

The embodiment shown in Fig. 3 comprises a generally cylindrical heat pipe 12. Refrigerant 15 is evaporated from a reservoir 66 at the first end region 24 by the input of heat (Qg) via the ribs 52. The evaporated refrigerant passes via the ejector 30 to the second end region 26 where the evaporator refrigerant condenses, thereby giving up heat (Qc) to the surroundings via the ribs 54. The condensed refrigerant collects in a reservoir 68.

Refrigerant 15 passing through the ejector 30 causes the refrigerant in the reservoir 58 of the evaporator 57 to evaporate thereby extracting heat (Qe) from the surroundings, to create the refrigerating effect.

In order to transport condensed refrigeration from the second end region 26, a conduit 69 in the form of a tube is provided extending from the second end region 76 to the first end region 24. The conduit 69 is journalled in bearings 70 A, and remains substantially motionless while the heat pipe 12 is rotated about its axis 72. Pick-up means in the form of a scoop pipe 69A extends from the subsidiary conduit 69 and is in communication therewith. A weight 73 A is provided on the scoop pipe 69A to prevent rotation of the conduit 69.

As the pipe 12 is rotated, refrigerant 15 in the reservoir 66 is collected by the scoop pipe 69A and transported by capillary action in the direction of the arrows B to the first end region 24 for further evaporation.

Some of the condensed refrigerant travelling along the conduit 69 passes into a line 74A and passes via an expansion valve 73A to the evaporator 57.

Referring to Fig. 4, there is shown another embodiment which is the same as the embodiment shown in Fig. 1, with the exception that secondary heating means is provided at said first end region 24. Secondary heating means may comprise a gas burner 64. The features in Fig. 2 which are the same as

those in Fig. 1 are designated with the same reference numeral.

Fig. 5 shows a third embodiment, which is similar to that shown in Fig. 1, with the exception that a secondary reservoir 66 is provided at the first end region 24 to hold surplus refrigerant 15. Those features of the embodiment shown in Fig. 3 which are the same as in Fig. 1 are designated with the same reference numeral.

The embodiment shown in Fig. 6 is, again, similar to that shown in Fig. 1, and the same features have been designated with the same reference numeral, but in Fig. 6, the wick 22 is replaced by a conduit 169 extending in an annular formation around the wall 14 through which the condensed refrigerant travels from the second end region 26 to the first end region 22. The conduit 12 is tilted so that the second end region 26 is higher than the first end region 24 so that the condensed refrigerant 15 travels under the influence of gravity to the first end region 24. A one-way valve 169A is provided in the conduit 169 through which the condensed refrigerant 15 passes. As can be seen, the condensed refrigerant 15 at the second end region 26 is collected by a barrier 70 to enable the condensed refrigerant to pass into the subsidiary conduit 169. Some of the refrigerant 15 collects at the housing 36 of the ejector 30 and is removed therefrom by the capillary tube 62 to the evaporator 57.

When the condensed refrigerant 15 reaches the first end region 24, it passes into the inner space 16 and collects against sealed first end 18.

Referring to Fig. 7, there is shown a further embodiment of the invention which comprises many of the features of the embodiment shown in Figs. 1 to 6, and these have been designated with the same reference numeral.

The embodiment shown in Fig. 7 differs from the embodiment shown in Figs. 1 to 6 in that it is intended to be arranged vertically with the end 18 as the lower end, and the end 20 as the upper end. The apparatus 10 shown in Figs. 7 comprises cooling means in the form of a water jacket 82 into which cooling water can be passed via the inlet 84, and heated water can leave the water jacket

82 via outlet 86. The cooling water passing through the jacket 82 cools the refrigerant at the second end region 26 thereby causing the refrigerant to condense on the wall 14 of the heat pipe 12.

The ejector 30 defines a collecting recess 88 extending around the inside of the wall 14 to collect condensed refrigerant therein. A line 90 extends from the recess 88 to the reservoir 58 of the evaporator 57. An expansion valve 90A is provided in the line 90 to expand the condensed refrigerant into the reservoir 58.

The transport means for returning the condensed fluid to the first end region 24 comprises a line 92 extending from the recess 88 to the first end region, via a one way valve 92A. The transport means also includes a wick 94 extending from the line 92 to the inside of the heat pipe 12 at the first end region 24. The condensed refrigerant 15 passing from the wick 94 into the heat pipe 12 is condensed at the bottom thereof, as shown.

In operation, heat is applied to the condensed refrigerant 15 at the bottom of the first end 24 of the heat pipe 12 to evaporate the refrigerant. The evaporated refrigerant passes through the ejector 30 thereby entraining low pressure refrigerant vapour from the evaporator 57 via a feed pipe 59. The refrigerant from the first end region 24 and the evaporator 57 is combined in the central region 36 and passed out of the ejector via the diffuser 42 into the second end region 26 of the pipe 12 where it is condensed by the cooling water passing through the jacket 82 onto the wall 14 of the pipe 12 to be collected in the recess 88 defined by the ejector 30. Some of the condensed refrigerant is fed by line 90 via expansion valve 90A to the evaporator 57, and the remainder is fed via line 92 and the wick 94 to the first end region 24.

Referring to Figs. 8, 8A and 9, there is shown examples of the wick 94 which can be used in the embodiment shown in Fig. 7.

Referring to Fig. 8, the wick 94 shown therein comprises a tube 96 housing at one end a wick structure 98. The wick structure 98 comprises

sintered copper powder having a particle size of 50 to 60 microns. A plurality of channels of a diameter of substantially 0.1 to 0.3 mm extend the length of the wick structure 98. In the embodiment shown in Fig. 8, condensed refrigerant passes in the direction of the arrows shown therein. The diameter of the channels are dependent upon the cooling capacity of the unit and could be any suitable size as would be appreciated by the skilled person.

Fig. 8A shows one example of the wick structure 98 shown in Fig. 8. In the specific example shown, the wick structure 98 is substantially cylindrical in configuration having a length of substantially 35mm and a diameter of substantially 25 mm. The evaporator operating temperature is substantially 75 ^* C and has a mass flow rate of substantially 0.5g/sec. The capillary pressure is 0.15 bar and the power capacity is 1KW. The wick structure 98 shown in Fig. 8A is a compressed sintered wick structure.

Referring to Fig. 9, the wick 94 comprises a tube 96 housing in a central region thereof an alternative wick structure 98. The wick structure 98 is formed of two concentric layers of wicking material. The inner layer 98A is formed of particles have a diameter of 50 to 60 microns, and the outer layer 98B is formed of particles having a diameter of 150 to 200 microns. The material used in the wick can be copper or phosphor bronze powder. Condensed refrigerant passing through the wick 94 passes in the direction of the arrows shown.

Fig. 10 shows a plurality of energy transfer apparatus 10 arranged next to each other in parallel to from an energy transfer arrangement 80 which can be used, for example, for an air conditioning unit in a building. Each of the energy transfer apparatus 10 can be the same as those shown in any of Figs. 1 to 7 and each comprises an ejector 30 (not shown in Fig. 10). A first set of fins 152 extend between the first end region 24 of each apparatus 50, as second set of fins 154 extend between the second end regions 26 of each apparatus 10, and a third set of fins 156 extend between the central region 28 of each apparatus 10. Each apparatus is also provided with a reservoir 58 (not shown in Fig. 10).

A pipeline 160 extends around the fins 156 and heat can be pumped therein as indicated by the arrow D. Heat is removed from the pumped air by evaporation of the refrigerant in each of the reservoirs and cold air pumped out as indicated by arrow E.

Referring to Fig. 11, there is shown an embodiment of the apparatus 10 in which the heat pipe 12 has a concentric internal wick 22 between an outer wall 14 and an inner cover 23, the wick 22 and the cover 23 extending only over part of the length of the pipe 12, substantially a location spaced from one end, the lower end 28 as viewed in the drawing, to midway up the pipe 12. An upper end of the cover 23 terminates at an ejector 30 as described previously.

At the first end region 24 of the pipe 12 there is, below the wick 22 and cover 23, a reservoir of a liquid refrigerant/absorbent combination 62 such as water/lithium bromide (H ₂ O/LiBr) or potassium formate (or refrigerant/adsorbent combination). At this location, the combination 62 is heated Qi by an external source, for example natural gas or solar energy, and this expels, from the combination 62, refrigerant vapour which has been absorbed by the combination as will hereinafter be described. The chemical absorption results in the expelled vapour being under high pressure. The vapour flows through the ejector 30 where it entrains vapour from an absorber 320 as will be explained below.

Surrounding the heat pipe 10 substantially centrally along the length thereof is an evaporator 57 and absorber 320. Condensed liquid refrigerant can be passed from an annular collector 322 at the second end region 26 located at the upper end of the heat pipe 12 along a tube 323 through an expansion valve 324 to enter the evaporator 57 at low temperature and pressure. Due to capillary pressure difference, the liquid refrigerant is passed through a distribution wick 326 in the evaporator 57. By way of fins 56, heat Qe is absorbed from the ambient air to cause the liquid refrigerant to evaporate. The refrigerant vapour from the evaporator 57 is passed through a vapour transfer tube 328 the absorber 320, the lower end of the transfer rube 328 being immersed in a supply of the liquid refrigerant/absorbent combination therein.

The refrigerant vapour bubbles through the refrigerant/absorbent combination, thereby improving mixing and enhancing the absorption process. The heat Qa generated by the process is removed using a heat sink such as air or water by way of fins 56A. The wick 22 of the heat pipe 12 is in communication with the liquid refrigerant/absorbent combination in the absorber 320 and, above the level of the liquid combination, the internal space of the absorber 74 is in communication with the ejector 30 through an opening 77 in the cover 23 of the pipe 12.

When refrigerant vapour from the generator at the lower end 18 of the heat pipe 12 expands through the ejector 30 the high velocity vapour entrains low pressure refrigerant vapour from the absorber 320. The mixed vapours pass through the diffuser 42 to be discharged into the condenser section at the second end region 26 of the heat pipe 12 where heat Qc is removed using a htat sink such as air or water by way of fins 78 to condense the refrigerant vapour. The refrigerant/absorbent (or adsorbent) combination which is passed to the first end region 24 by way of the wick 22 is a concentrated solution of refrigerant in absorbent. When the refrigerant is evaporated a dilute solution of refrigerant in absorbent is returned to the absorber 320 via line 330 after passing through an expansion valve 332 to reduce its pressure.

Referring to Fig. 11 A there is shown a modification to the embodiment shown in Fig. 11 and all the features in Fig. 11A which are the same as those in Fig. 11 have been designated with the same reference numeral.

Fig. 11A differs from Fig. 11 in that the wick 22 of Fig. 11 have been replaced by a wick 94 connected by a Une 92 and one way valve 92 A to the absorber 320 whereby the concentrated solution of refrigerant in absorbent is supplied to the first end region 24. The wick 94 can be the same as the wick 94 shown in Figs. 7 to 9.

Another difference is that the embodiment shown in Fig. 11A includes a compressor 360 whereby refrigerant vapour is compressed and passed via a line 362 a condensor coil 364 in the first end region 29 to heat the refrigerant in the

first end region 24, thereby condensing the refrigerant in the coil 364. The condensed refrigerant is then passed via an expansion valve 366 to the evaporator 57.

Referring to Fig. 11B there is shown a modification to the apparatus as shown in Fig. 11A. The apparatus shown in Fig. 11B comprises all the features of Fig. 11B and those have been designated with the same reference numeral. The apparatus shown in Fig. 11B differs from that shown in Fig. 11A in that it includes a further evaporator 368 whereby the ejector 30 receives refrigerant vapour from the further evaporator 368 rather than the first end region 24.

The apparatus shown in Fig. 11B also includes a condensor 370 which is in communication with the first end region 24 via a Une 372. The condensor 370 is also in communication with the further evaporator 368 via a line 374 and an expansion valve 376.

Heat Qi is supplied to the first end region 24 evaporates to refrigerant therein which passes via the line 372 to the condensor 370 at which the refrigerant is condensed. The condensed refrigerant is then passed via the line 374 and the expansion valve 376 to the further evaporator 368.

The line 362 from the compressor is also in communication with the further evaporator 368 via a line 378 and an expansion valve 380, to also feed condensed refrigerant to the further evaporator.

A further vapour transfer tube 382 connects the further evaporator 368 to the absorber 320 whereby evaporated refrigerant is bubbled through the absorbent to be absorbed thereby. The refrigerant not absorbed is mixed with unabsorbed refrigerant from the vapour transfer tube 328.

Referring to Fig. 12, there is shown an embodiment of the invention comprising energy transfer apparatus 110 which is adapted to enable work to be extracted therefrom. The apparatus 110 comprises many of the same features as those shown in Fig. 1 and these have been designated with the same

reference numeral. The heat pipe 12 has an internal wick 22 extending over a substantial part of the length thereof to provide a supply of refrigerant/ absorbent (or adsorbent) combination to a reservoir 340 thereof at the first lower end region 24 of the heat pipe 12, adjacent the end 18 i.e. to the generator. The refrigerant/absorbent combination at the generator is heated Qi by any suitable heat source to expel the refrigerant vapour previously absorbed by the refrigerant/absorbent combination as hereinafter described.

In this embodiment, the high pressure refrigerant vapour passes into a turbine 352 which is mounted substantially centrally within the heat pipe 12 for rotation therein. The passage of the refrigerant vapour operates the turbine 352 which is connected by a drive shaft 354 to extract work Wo from the heat pipe 12 via an alternator 356.

As the refrigerant vapour exits from the turbine 352 it is condensed at the second upper end region 26 of the heat pipe 12 and the liquid refrigerant is collected by an annular collector 342 which contains a supply of the refrigerant/absorbent combination whereby the condensed refrigerant is absorbed. The collector 342 is in communication with the wick 22, whereby a supply of the absorbent/refrigerant is continually passed to the first end region 24 of the heat pipe 12. As in the previous embodiment, the refrigerant is evaporated and the absorbent i.e. a dilute solution of refrigerant in the absorbent or adsorbent is returned from the lower end of the heat pipe 12 through the line 344 and an expansion valve 346 to the annular collector 342.

In the embodiment shown in Fig. 13, the heat pipe 12 is substantially frusto-conical in configuration, and tapers inwardly from the first end region 24 to the second end region 26. The heat pipe 12 is mounted on a shaft 72 which is rotated by a suitable motor (not shown) in the direction of the arrow X. The energy transfer apparatus shown in Fig. 13 operates in the same way as those shown in Figs. 1 to 7 in that refrigerant is evaporated at the first region 24 and is condensed at the second region 26 to be passed back along the subsidiary conduits 69 by virtue of the centrifugal force created by the rotation of the heat pipe 12 about the shaft 72. One way valves 69A prevent condensate flow in the

opposite direction. Between the first and second regions 24,26, the refrigerant vapour passes through the ejector 30 to entrain refrigerant from the evaporator

57 to create a refrigerating effect as explained above. In the embodiment shown in Fig. 13, the reservoir 58 of the evaporator 5 and the secondary reservoir 66 are of a torus configuration extending around the outside of the heat pipe 12.

Fig. 14 shows an embodiment of the heat transfer apparatus similar to that shown in Fig. 13 in which the ejector 30 has been replaced by a turbine 352. The embodiment shown in Fig. 14 operates in a similar manner to the apparatus in shown in Fig. 13, in that the frusto-conical conduit 12 is rotated about its axis 72, and refrigerant 15 is evaporated from the first end region 24 and passes towards the turbine 352, to drive a turbine 352 thereby causing work (Wo) to be done by the work output means 356 by the shaft 354. After passing through the turbine 352, the refrigerant 15 condenses at the second end region 26 giving out heat (Qo) via the fins 54. The condensed refrigerant 15 can flow back via subsidiary conduits 368 provided around inside of the wall 14. The subsidiary conduits 368 are provided with stop valves 369. The centripetal force caused by the rotation of the conduit 12 causes the condensed refrigerant to move in the direction of the arrows B.

Referring to Fig. 13 A, there is shown a modification to the apparatus shown in Fig. 13 in which the fins 52, 54 at the first and second end regions 24,26 respectively are replaced by flexible metal fibres 52A, 54A. On rotation the heat pipe 10 as shown in Fig. 13 A, the fibres 52 A, 54 A act as fans to increase the efficiency of heat transfer. Thus, the metal fibres 52A, 54A act on an impeller and a heat exchange.

Similarly, in Fig. 14A, there is shown a modification to the apparatus shown in Fig. 14, in which the fins 52,54 have been replaced by flexible metal fibres 52 A, 54A which act in the same manner as described above with reference to Fig. 13 A.

Referring to Fig. 15, there is shown heat transfer apparatus 210 which

comprises a combination of the apparatus shown in Figs. 13 and 14. The apparatus 10 as shown in Fig. 15 comprises many of the features of the apparatus shown in Figs. 13 and 14, and these have been designated with the same reference numeral.

The apparatus 210 comprises a heat pipe 212 mounted on a spindle 72, and rotated in the direction of the arrow Y. The spindle 72 is journalled in a bearing 73.

Heat Qi is supplied to a first region 224 to evaporate liquid refrigerant therein. The liquid refrigerant passes to the opposite second and third end regions, 226A, 226B of the heat pipe 610. The refrigerant passing towards the second end region 226A passes through the ejector 30 and entrains low pressure refrigerant vapour from the evaporator 57 to mix with the refrigerant from the first region 224 in the central region 36 of the ejector 30. The mixture of refrigerant then passes out of the ejector 30 at the diffuser 42 into the second end region 226A where the refrigerant is condensed. Heat Qo is extracted from the refrigerant at the second region 226A by cooling fluid passing over the fins 254A. The condensed refrigerant is then returned to the first region 224 by centrifugal force through the subsidiary conduits 69 via one way valves 69A. Some of the refrigerant passing through the subsidiary conduit 69 is collected by lines 62 to pass some of the refrigerant to the evaporator 57 via an expansion valve 62A.

Refrigerant in the first region 224 passing towards the end 20B passes through the turbine 352, thereby causing the turbine 352 to rotate which in turn rotates the shaft 354. This enables work Wo to be extracted from the heat pipe for example, by an alternator 356 to generate electricity. The refrigerant at the third end region 226B is condensed by the extraction of heat Qo therefrom by a cooling medium passing over the fins 254B. The condensed refrigerant is returned to the first region 224 by a subsidiary conduit 69 via one way valves 69A.

Thus, the apparatus 210 acts as a combined rotary refrigeration and

power generation system.

It will be appreciated that the heat transfer apparatus 610 which consists of a centrally arranged generator, and condenses at the two opposite end regions, could alternatively incorporate absorber or adsorber arrangements such as that shown in Fig. 16 (see below).

Referring to Fig. 16, there is shown further heat transfer apparatus 310 comprising a rotary heat pipe 312 mounted on a spindle 72 journalled in bearings 73. The heat pipe 312 comprises a first region 24 and a second region 26. The first and second regions 24,26 are respectively first and second end regions. A turbine 352 is mounted intermediately first and second regions 24,26, whereby refrigerant evaporated from the first region 24, by the supply of heat Qi thereto passes through the turbine 352 to cause the turbine 352 to rotate which, in turn, rotates the shaft 354 thereby enabling for example, in the form of electricity via an alternator 356.

The apparatus 310 also comprises an absorbent 314 (or adsorbent) in the second region 26 to absorb (or adsorb) refrigerant passing from the turbine into the second region 26. The heat of absorption is removed from the apparatus 310 by an appropriate cooling medium via fins 54. The concentrated solution of refrigerant and absorbent is then passed via subsidiary conduits 69 and one way valves 69A by centrifugal force to the first region 24 whereupon the refrigerant is evaporated and the dilute solution of refrigerant and absorbent is passed back via line 316 and expansion valve 316A to the second region 26.

Referring to Fig. 17, there is shown a further embodiment of the heat transfer apparatus 10 comprising many of the features of the embodiment shown in Fig. 13, and these have been designated with the same reference numeral, which is with the exception that the heat pipe 12 is of a stepped design, rather than a frusto-conical design. The embodiment shown in Fig. 17 comprises transport means for returning the refrigerant to the first end region 24 in the form of external tubes 469, which deliver the condensed refrigerant into the first end region 24 via one way valves 469A. The evaporator 57 is

supplied with refrigerant from the lines 469 via tubes 462 and expansion valves

462A. At the second end region 26, there is provided a condensate receiver 27 for receiving condensed refrigerant therein, to enable the lines 469 to return the refrigerant to the first end region 24. The first end region 24 is of a first diameter, and the second end region 26 is of a second diameter, where the diameter of the first end region is greater than the diameter of a second end region 26. The lines 169 deliver the condensed refrigerant to the first end region 24 adjacent the periphery thereof.

Referring to Fig. 18, there is shown a further embodiment of the invention comprising apparatus 510 which is similar to that shown in Fig. 16, and comprising a heat pipe 512 which is of stepped design, rather than a frusto-conical design. In this embodiment, the refrigerant/absorbent (or adsorbent) solution 514 is passed to the first end region 24, by means of a line 569 and a one way valve 569A. The solution fed to the first end region 24 from the line 569 is a concentrated solution 514 of refrigerant in absorbent. The line 569 extends externally of the heat pipe 512. A line 516 returns a dilute solution of refrigerant in absorbent to the second end region 26 via an expansion valve 516 A. The line 716 extends externally of the heat pipe 712.

Referring to Fig. 19, there is shown energy transfer apparatus 610 similar to the embodiment shown in Fig. 1 and similar features have been designated with the same reference numeral. The apparatus 610 differs from the apparatus 10 shown in Fig. 1 in that the ejector 30 has been replaced by a turbine 652 and a compressor 654 connected by a shaft 656. Also, the wick 22 has been replaced by the subsidiary conduit 69 and the expansions valve 69A.

The circulating refrigerant passes into the turbine as indicated by arrow F to drive the turbine 652. The refrigerant is exhausted from the turbine 652 via the line G. The rotation of the turbine 652 rotates the shaft 656 which, in turn drives the compressor 654. Evaporated refrigerant from the reservoir 58 is drawn into the compressor 654 via the line H to be compressed therein. The evaporation of the refrigerant 15 in the reservoir 58 extracts heat from the surrounding fins 56 to create the refrigerating effect. The compressed

refrigerant condenses and exits from the compressor 254 via the line I where it is mixed with the refrigerant exhausted from the turbine 252 via the line G in the second end region 26 at condensor reservoir 658.

The condensed refrigerant is then passed back to the first end region 24 via the subsidiary conduits 69 and to the reservoir 58 via the capillary tube 62.

Fig. 20 shows a further heat transfer apparatus 710 which the apparatus 710 comprises a heat pipe 712 and includes many of the features of the previous drawings, such features have been designated with the same reference numeral as in the earlier drawings. In the embodiment shown in Fig. 20 a turbine 752 is disposed in the central region 28 to be driven by the flow of refrigerant vapour therethrough as indicated by the arrows J. The turbine 752 is connected by a shaft 754 to a suitable work output means 756, whereby rotation of the turbine 752 rotates the shaft 754 causing work (Wo) to be done by the work output means 756. In the preferred construction of this embodiment, the work output means comprises an alternator, whereby the rotation of the turbine by the passage of refrigerant therethrough generates electricity.

Referring to Fig. 21, there is shown a further heat transfer apparatus 810 which is a combination of the apparatus shown in Fig. 1 and the apparatus shown in Fig. 20. Many of the features described with reference to Figs. 1 and 20 are incorporated in Fig. 1, and have been designated with the same reference numeral. In this embodiment, the apparatus comprises a heat pipe 812 having a first region 824 arranged centrally of the heat pipe 812. The first region 824 corresponds to the first end regions 24 of the embodiments shown in Figs. 1 and 20. In operation heat is applied to the first region 824, which causes refrigerant in the wick 22 to evaporate. This refrigerant is passed in opposite directions down the heat pipe 812 towards a second region 826A and a third region 826B.

When the evaporated refrigerant passes through the ejector 30 at the second region 826A, it entrains low pressure refrigerant vapour in the

evaporator 57 and the mixture of refrigerant from the first region 24 and the evaporator 57 is passed via the diffuser 42 to the second region 826A where the refrigerant is condensed and heat of condensation is extracted, for example by passing a cooling medium over the fins 824A. The condensed refrigerant is returned along the wick 22 to the first region 824. Thus, this section of the heat pipe 812 acts to refrigerant surroundings to the evaporator 57.

Refrigerant passing from the first region 824 towards the third region 826B passes through the turbine 752 thereby causing it to rotate. This rotation of the turbine 752 is transmitted via the shaft 754 to drive suitable work output means 756, for example an alternator. The third end region 826B is provided with fins 854B from which heat of condensation can be extracted by passing a suitable cooling medium over the fins 854B. This condensed the refrigerant at the third end 826B which is collected by the wick 22 to be passed back to the first region 824.

It will be appreciated that the heat transfer apparatus 810 which consists of a centrally arranged generator, and condenses at the two opposite end regions, could alternatively incorporate absorber or adsorber arrangements such as those shown in Fig. 11 or 12.

In Fig. 22 another embodiment is shown, comprising apparatus 910 in which some of the features are the same as those in Fig. 1 and are designated with the same reference numeral and operate in the same way. The embodiment shown in Fig. 22 differs from that shown in Fig. 1 in that it includes means for collecting solar radiation in the form of an array of photovoltaic cells 912 arranged at the first end region 24 to replace the fins 52 shown in Fig. 1. Solar energy impinging on the photovoltaic cells 912 causes heat to be generated which evaporates the refrigerant at the first end region 24. The apparatus 910 shown in Fig. 22 then operate in the same way as the heat pipe 10 shown in Fig. 1.

The arrangement shown in Fig. 22 shows a water jacket 92 formed around the second end region 26 to extract the heat produced at the second end

region 26. Thus cold water entering the inlet 94 of the water jacket 92 is warmed by the heat produced at the second end region 26 and hot water exits the water jacket 92 at the outlet 96.

The hot water which exits from the outlet 96 could be used as a hot water supply in a building or in a central heating arrangement. Of course, it will be appreciated that the water jacket 92 could be replaced by fins which would operate in the same way as the fins 54 in Fig. 1.

Fig. 23 shows an arrangement consisting of the embodiment shown in Fig. 22 and a solar concentrator for concentrating solar energy 98 onto the photovoltaic cells 90. The solar contractor may include a concave mirror to focus solar rays onto the photovoltaic cells 90. It will be appreciated that the solar concentrator could be in the form of a lens.

Referring to Fig. 24, there is shown an embodiment of the invention similar to that shown in Fig. 11, with the exception that the heat supphed to the first end region 24 is provided by solar collector means in the form of a photovoltaic panels 902. Other than this, the heat pipe 12 shown in Fig. 24 comprises the same features and operates in the same manner as the heat pipe 12 as shown in Fig. 11.

The photovoltaic 902 extends substantially half way round the external circumference of the heat pipe 900 shown in Fig. 24.

It will be appreciated that the end 26 could comprise an absorber or adsorber similar to that described with reference to Fig. 12.

Referring to Fig. 25, there is shown an arrangement of heat pipes 900, each being provided with a photovoltaic panels 902 and a concentrator 904. A manifold 906 of cooling water extends across the second end region 26 of each of the heat pipes 900 to extract heat and condensation therefrom.

The arrangement shown in Fig. 25 could be an arrangement of apparatus

910 as shown in Fig. 22 or a combination of the apparatus 810 and the apparatus 910.

Referring to Fig. 26, which shows an end view of the arrangement shown in Fig. 25, it can be seen that the concentrators 904 act to concentrate solar energy onto the photovoltaic panels 902 of each heat pipe 900.

The harmful effect of chlorofluorocarbon (CFC) refrigerants on the ozone layer and global warming has brought about interest in the use of efficient and environmentally friendly systems. Hydrofluorocarbons (HFC) and hydrocarbon refrigerants (e.g. R32 CARE 30) have recently been employed in vapour compression systems. These refrigerants have no potential to deplete the ozone layer and are safe to use in terms of toxicity and flammability. These refrigerants can be used in the embodiments of the invention described above. Also, it is possible to use natural refrigerants such as water, methanol or ethanol.

Referring to Figs. 27, 28 and 29 there is shown heat recovery apparatus 1010 comprising a heat pipe 1012 rotatable about its axis 1013 in the direction shown by the arrow X in which some of the features are the same as those of earlier embodiments and have been designated with the same reference numerals.

The heat pipe 1012 comprises a wall 1014 which as shown tapers on the inside thereof outwardly from the second end region 26 to the first end region 24. When the heat pipe 1012 is rotated in the direction of the arrow X, refrigerant condensing on the side wall 1014 at the second end region 26 is transported by centrifugal force and the taper of the wall 1014 back to the first end region 24 to be deposited in a reservoir 1015. Thus, refrigerant vapour flows along the inside of the heat pipe 1012 as shown by the arrows A and condensed refrigerant flows back along the wall of the pipe as shown by the arrows B.

The first end region 24 is provided with outward by extending flexible

metal fibres 52A formed of a suitable heat conducting material e.g. copper. The second end region 26 is also provided with outwardly extending flexible metal fibres 54A formed of a suitable heat conducting material e.g. copper.

Rotation of the heat pipe 1012 rotates the fibres 52 A, 54 A. This creates a fanning effect of the fluid, e.g. air, about the fibres 52 A, 54A thereby enhancing heat transfer to or from the fibres and, consequently, to or from the respective first and second end regions 24,26.

Also, the fibres 52 A, 54 A provide a large surface area which further enhances the heat transfer.

Referring particularly to Fig. 27, the heat recovery apparatus 1010 further includes fluid supply conduit arrangements in the form of duct 1018. the duct 1016A passes hot air in the direction of the arrow E towards the fibre 52A at the first end region 24. Heat is transferred from the air to the first end region via the fibres 52 A. Cooled air is then exhausted from the apparatus 1010 via the conduct 1016B in the direction of the arrow F.

Similarly, cool air is passed to the fibres 54A at the second end region 26 in the direction of the arrow C, whereby heat from the second end region is transferred via the fibres 54A to the air. Warmed air is then exhausted from the apparatus 1010 via the duct 1018B in the direction of the arrow H.

Insulation 1020 is provided around the central region 28 to prevent heat loss therefrom. A motor 1022 is connected via a belt 1024 to a pulley 1026 on the heat pipe 1012 to rotate the heat pipe 1012.

Referring to Fig. 28 in particular, the heat pipe 1012 shown therein is suitable heat pipe for use in the apparatus 1010 shown in Fig. 27, but the heat pipe shown in Fig. 28 differs from that shown in Fig. 27 in that it possesses an integrated motor 1028 (shown schematically in Fig. 28) to replace the motor 1022, belt 1024 and pulley 1026 arrangement shown in Fig. 27.

It has been realised that the use of flexible metal fibres 52 A, 54A which have been described above with reference to rotating heat pipes, is not limited to such use. Flexible metal fibres have been found to provide an enhanced heat transfer effect when use on non-rotating heat pipes.

Referring to Fig. 29, there is shown a dwelling 1030 in which the apparatus 1010 is installed in order to ventilate the dwelling 1030.

An advantage of the embodiment shown in Fig. 1 is that there are no moving parts and so are simple and reliable. It has the potential of long life and produce no noise or vibration. Furthermore, they have the advantage that they can be heated by natural gas, waste heat or solar energy, or a combination of more than one of these (e.g. solar energy and natural gas). A further advantage of the embodiments shown in Figs. IB and 1C is that they can be used as a cooling/heating devices as well as solar collectors. Also, the anticipated cost of production is low because inexpensive construction materials (for example copper or aluminium) can be used.

Modifications can be made to the invention without departing from the scope thereof. For example, the fins 52,54,56 could be replaced by a jacket or jackets in which fluid circulates. Also, the fins 52, 54 and 56 could be replaced in each of the embodiments showing such fins with flexible metal fibres or wires of the type discussed with reference to Figs. 13A, 14A 27 and 28.

Referring to Fig. 30 there is shown heat transfer apparatus 1110 comprising a heat pipe 1112 having a first end region 24 and a second end region 26. The heat pipe 1112 operates in a similar manner to the previously described heat pipes.

The heat pipe 1112 is rotatable about a shaft 72 journalled in bearings 72 A, as indicated by the arrow X in Fig. 30.

The apparatus 1110 further includes an ejector 30 comprising the features of the ejector 30 described previously. The apparatus 1110 also

comprises a generator 1114 to which heat Qg is supplied to evaporate a heat transfer fluid therein.

The apparatus 1110 has first heat exchange means in the form of a plurality of fibres or filaments 52A provided at the first end region 24, and second heat exchange means in the form of a plurality of fibres or filaments 54A provided at the second end region 26 on rotation of the heat pipe 1112 about the shaft 72 the fibres 52A and 54A enhance heat transfer to and from the respective first and second end regions 24, 26.

In operation, the heat pipe 112 is rotated and heat Qg is supplied to the generator 114. Liquid refrigerant in the generator 1114 is evaporated and passed via line 1116 to the evaporator 30. The passage of the refrigerant vapour from line 1116 through the ejector 30 entrains low pressure refrigerant vapour at the first end region 24 which, in this embodiment constitutes the evaporator. The low pressure refrigerant vapour from the first end region passes via line 1118, to be mixed in the ejector 30 with the vapour from the line 1116 and the mixture is ejected into the second end region 26.

The evaporation of the refrigerant in the first end region extracts heat Qe from the surroundings via the fibres or filaments 52A thereby creating a refrigerating effect at the first end region 24.

Refrigerant vapour passing from the ejector 30 is condensed in the second end region 26, by virtue of the extraction of heat Qc therefrom to the surroundings via the fibres or filaments 54A. Some of the condensed refrigerant is then returned to the generator 11154 via Une 1120 and one way valve 1122, and the remainder of the condensed refrigerant is returned to the first end regions via the Une 1124 and the expansion valve 1126.

Referring to Figs. 31 and 32, there is shown yet another embodiment in the form of heat transfer apparatus 1210 comprising a heat pipe 1212 having a first end region 24 and a second end region 26. First and second heat exchange means are provided respectively at the first and second end regions 24,26. the

first heat exchange means comprises a first plurality of metal fibres or filaments 52A and the second heat exchange means comprises a second plurality of fibres or filaments 54A. The heat pipe 1212 is rotatable about a shaft 72 journaUed on bearings 72A in the direction of the arrow X.

A compressor 1214 is provided in the heat pipe between the first and second end regions 24,26. The compressor 1214 is driven by a motor (not shown) via a rod 1216.

In operation , the heat pipe 1212 is rotated and the compressor 1214 is operated to compress refrigerant vapour from the first end region 24 and pass the compressed vapour to the second end region 26. Heat Qc is extracted from the compressed refrigerant via the fibres or filaments 54A to cause the refrigerant to condense on the walls of the heat pipe 1212 at the second end region 26.

The condensed refrigerant is passed back from the second end region 26 via a Une 1218 and an expansion valve 1220 to the first end region 24 where at the low pressure refrigerant extracts heat from the surroundings via the first pluraUty of fibres 52A thereby creating a refrigerating effect. The evaporated refrigerant is then compressed by the compressor 1214 to continue the cycle.

Referring to Fig. 32 there is shown a modification to the apparatus 1210 shown in Fig. 31 and the features which are the same as those shown in Fig. 31 are given the same reference numeral. The modified apparatus 1210 shown in Fig. 32 includes all the features of Fig. 31 and an ejector 30 and further evaporator 57. The ejector 30 operates in the same manner as ejectors described earUer in this specification.

On operating the compressor 1214 and rotating the heat pipe 1210 as described above, refrigerant vapour is passed via line 1222 to the ejector 30 to entrain refrigerant vapour from the further evaporator 57 via the line 1224. The vapour from the further generator 57 mixes with the vapour from the first end region 24 (constituting the main evaporator) and the mixture is ejected

from the ejector 309 into a region 1226 if the heat pipe 1212 between the ejector 30 and the compressor 1214.

The compressor 1214 compresses refrigerant from the region 1216 and passes the compressed refrigerant to the second end region 26 to be condensed as described above. Some of the condensed refrigerant is passed via the Une 1218 and the expansion valve 1220 to the first end region 24. The remainder of the condensed refrigerant is passed via a line 1218A and an expansion valve 1220A to the further evaporator 57.

Evaporation of refrigerant from the first end region 24 and from the further generator 57 extracts heat QE1 from the surroundings to the first end region via the first pluraUty of fibres or filaments 52 A.

It will be appreciated that while the present specification may describe different apparatus each of which include several different features, many of these features can be used in any of the apparatus described.

Whilst endeavouring in the oregoing specification to draw attention to those features of the invention beUeved to be of particular importance it should be understood that the AppUcant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.