Patent Description:
The atmosphere is a low temperature heat reservoir, with considerable atmospheric thermal energy. Atmospheric thermal energy mainly comes from solar energy, followed by geothermal energy and the dissipation of waste heat into the atmosphere from various human energy consumption activities (such as use of coal, oil, gas, electricity etc).

In this specification, unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned. <CIT> discloses a power generation system driven by a heat pump which produces a heat source by heating and a cold source by cooling for the driving of a heat engine to produce mechanical energy to drive a generator generating electrical power.

It is an object of the prevent invention to provide an apparatus and method that overcomes or substantially ameliorates some of the disadvantages and limitations of the known art or at least provides the public with a useful choice. It is an alternative object of the prevent invention to provide an apparatus and method that can be applied to any of a variety of functional needs.

According to a first aspect of the invention there is provided an apparatus for use with cryogenic working fluid as a working substance according to claim <NUM>. Preferred embodiments are provided in the dependent claims.

The invention provides or includes the following advantages and components:.

The invention will now be described, by way of example only, with reference to the accompanying drawings:.

Referring first to <FIG> and <FIG>, the present invention comprises a "Cryogenic Working Fluid Thermodynamic - Refrigeration Cycle" hereinafter "a first cycle" and "Frost-Free Two Stage Heat Exchange Cycle" hereinafter "a second cycle". The first cycle and the second cycle are coupled together to form a "Frost-Free Two Stage Cycle Thermodynamic - Refrigeration System", hereinafter called an "Apparatus".

As can be seen in <FIG> & <FIG>, the first cycle includes three main sections, namely a vaporiser (<NUM>), a high pressure expander (<NUM>) and at least one high pressure working fluid pump (<NUM>). These three sections are operatively connected by piping (<NUM>) as shown in <FIG>. Also, as can be seen in <FIG>, there are other accessories such as at least one valve (<NUM>), storage tank (<NUM>), thermometer (<NUM>), pressure meter (<NUM>), safety valve (<NUM>), release valve (<NUM>), one way valves (<NUM>), and generator (<NUM>) that are provided. The surfaces of the expander (<NUM>), the working fluid pump (<NUM>) and the piping in between are coated by an insulation layer (<NUM>).

The second cycle mainly includes a circulation pump (<NUM>), an ambient heat exchanger (<NUM>) and the vaporiser (<NUM>) that are connected operatively together by piping (<NUM>) as shown in <FIG>. The primary purpose of this second cycle is to overcome the challenge of frost forming on the ambient heat exchanger. The secondary purpose of the second cycle includes refrigeration, dehumidification and water-making capability.

The two cycles, namely the first cycle and the second cycle are coupled together through the vaporiser (<NUM>) to form the Apparatus. The vaporiser (<NUM>) contains the cryogenic working fluids or the first fluid such as liquid nitrogen, liquid air or liquid carbon dioxide (CO<NUM>) etc. Liquid state the first fluid or high pressure gas is manually filled into the first cycle from port (<NUM>) of the vaporiser (<NUM>) to act as a working fluid and starting power. At the same time, a heat-transfer liquid or the second liquid is also manually filled into the second cycle.

The first cycle process is comprised of the following three connected thermodynamic processes (see <FIG>):.

This converts ambient thermal energy into high pressure vapour, within the vaporiser. The first fluid in the vaporiser carries out heat exchange with the second cycle's the second liquid, which absorbs the heat energy in the second liquid. (This is the first cycle's heat input. It spontaneously occurs due to the difference temperature. The heat transfer therefore does not consume work. ) Then the first fluid vaporises into vapour and its temperature rises to near ambient temperature (e.g.T<NUM>=<NUM>) and its pressure rises to the set maximum working pressure (e.g. P<NUM>=12Mpa). This high pressure vapour also fills the storage tank and the piping up to the valve (<NUM>).

This converts high pressure vapour in the expander into mechanical work and/or cryogenic liquid. The high pressure vapour inside the vaporiser and the storage tank (primary state parameters; T<NUM>=<NUM>, P<NUM>=12Mpa) flows into the high pressure expander through piping to propel a piston wheel to turn, which outputs mechanical work and cryogenic liquid. An adiabatic enthalpy drop occurs here, its temperature drop is directly proportional to its pressure drop. When the temperature falls to the vapour's liquefaction range (e.g. N2, P<NUM> = <NUM>. 1Mpa, T2 = <NUM> to <NUM>), a gas/liquid phase change occurs. Because the liquid state working fluid exiting the expander has a cryogenic liquid, the expander also outputs excellent refrigeration capacity whilst outputting its mechanical work.

This process occurs within the high pressure working fluid pump and consumes work. It raises the pressure of the first fluid and pumps it into the vaporiser. The first fluid enters the high pressure working fluid pump through piping. The first fluid is then pumped into the vaporiser and again carries the isobaric absorbing heat process and vaporise into high pressure vapour. The high pressure working fluid pump consumes energy to work. The whole process repeats, thereby forming "a cryogenic working fluid thermodynamic - refrigeration cycle" (the "a first cycle" of this invention).

As seen in the left hand side of <FIG> & <FIG>, the second cycle is a frost-free two stage heat exchange cycle. In this second cycle, a heat-transfer liquid (the second liquid), preferably water or, even better, a antifreeze having a lower freezing point (e.g. -<NUM>), is circulated by the circulation pump. The second liquid gives up heat to the first fluid. The second liquid's temperature drops to the determined temperature (e.g., -<NUM>). The cold second liquid flows to the air heat exchanger and exchanges heat with external heat source (e.g. air or water). After this exchange, the air temperature drops to about -<NUM>. Now the cold air released by the air heat exchanger output provides excellent refrigeration capacity and can be used for various refrigeration fields. When the air temperature falls to dew point, condensation occurs and the condensate can be collected and purified as fresh water. When the second liquid absorbs ambient air heat, its temperature rises to the ambient temperature (e.g. <NUM>), It will flow to the vaporiser to carry out heat exchange again, and the heat energy transfers to the first fluid in first cycle (as heat input of the first cycle). The second liquid then becomes cold liquid once more. This process repeats, to comprise the second cycle.

As explained above, the two cycles, namely the first cycle and the second cycle, are coupled together through the vaporiser (<NUM>) to form the "Frost- Free Two Stage Cycle Thermodynamic - Refrigeration System or "Apparatus". Liquid state cryogenic working fluid (the first fluid) or high pressure gas is manually filled into the first cycle (<NUM>) from port (<NUM>) of the vaporiser (<NUM>) to act as working fluid and starting power. At the same time, heat-transfer fluid (the second liquid) is also manually filled into the second cycle. For operational safety, the amount of the first fluid used should be determined by the total vaporising volume comprising of vaporiser (<NUM>), storage tank (<NUM>) and piping (<NUM>) up to the valve (<NUM>); and vaporising temperature (the temperature of the heat source), so that when the first fluid is completely vaporised and expanded, it can only reach the first cycle system's maximum working pressure. Even when the high pressure gas is filled into the first cycle system through the vaporiser (<NUM>), it can still only reach the first cycle system's maximum working pressure. Provided that there is no leak in the first cycle system, the initial first fluid (filled cryogenic working fluid or high pressure gas) will always remain in the first cycle system (similar to the way refrigerant remains in a refrigeration machine for a long time) which can be used to open valves (<NUM>) and start operation, and to close the valve (<NUM>) and turn off the apparatus. The degree of opening of the valve (<NUM>) directly controls the flow of the first fluid, thereby directly controlling the rotational speed and shaft torque of the expander (<NUM>). As such, it is a continuous variable transmission and there is no need for a gearbox.

In the second cycle, the second liquid is water or, preferably, a antifreeze having a lower freezing point (e.g.; -<NUM>). The working temperature of the ambient heat exchanger (<NUM>) is adjusted by using a controlling device (not shown) to adjust the speed of the circulation pump (<NUM>), which in turn controls the flow of the second liquid in circulation.

To enhance the efficiency of the heat exchange process, the circulation pump (<NUM>) and fan (<NUM>) of the second cycle also consume energy.

In the present invention, the mechanical work output from the expander (<NUM>) is high quality energy, which can be directly used to power vehicles, ships, aircrafts and other powered machineries, and it can be converted into electrical energy, thermal energy or other forms of energy for use. Because of a dissipation effect, the different types of energy such as mechanical energy, electrical energy, thermal energy etc., will all be dissipated into the atmosphere as "waste heat" after being used.

After adiabatic expansion the liquid state working fluid created by the expander (<NUM>) will be cryogenic , so that corresponding heat exchange technology and devices can then be applied to obtain "Refrigeration Capacity's Use in Separate Stages" (For example: air conditioning <NUM> to <NUM>, storage <NUM>, refrigerating <NUM>, freezing -<NUM> to -<NUM>, cryogenic uses -<NUM> to -<NUM>, liquefying air -<NUM> to -<NUM> etc.).

Since naturally occurring gases (such as nitrogen and air) are selected as the working fluid, any leaks that occur during usage will not cause any pollution. Therefore the harmful effects that current refrigerants pose to the environment are eliminated.

All air contains water vapour but with different levels of moisture. When air exchanges heat through the heat exchanger and its temperature falls to the dew point, the water vapour in the air will condense. After collection and purification, it will be high quality fresh water. This pioneers a method of using air to make fresh water and can solve fresh water shortage problems. It also gives a reliable technology facilitating the creation of habitats in deserts and other water-scarce locales. Once the water vapour in the air condenses and is removed, the air will have become dry air. Therefore the invention also has a dehumidifying capability.

All air contains moisture. When air directly exchanges heat with cryogenic working fluid, it is easy for frost to form on the surface of the heat exchanger (<NUM>). Frost will obstruct heat conductibility and causes heat exchanging efficiency to fall. As more and more frost forms, the heat exchanger will eventually completely cease to function. The "Frost-Free Two Stage Heat Exchange Cycle" is designed to solve this problem. Water has a large specific heat and flows easily. Cryogenic working fluid is used to exchange heat with water, then water is used to exchange heat with air, thus constituting the "cryogenic working fluid - water -air" two stage heat exchange method. Water temperature is directly proportional to the amount of heat exchanged but is inversely proportional to the flow volume. The amount of heat exchanged is directly proportional to the size of work output. When determining the size of work output, the amount of heat exchanged cannot be adjusted, but the flow of the water circulation can be. The flow can be adjusted to reach the required water temperature to ensure that the circulating water does not freeze and also that no frost forms on the surface of the heat exchanger. In order to minimise the power used by the circulation pump (<NUM>), to output excellent refrigeration capacity, and that the invention can be effectively operated in colder regions, it would be better to use a low freeze point (such as -<NUM>) antifreeze as heat transfer liquid.

Nitrogen can be used as a working fluid (see <FIG>, <FIG> & <FIG>). According to nitrogen's thermodynamic table of properties:.

The heat-transfer liquid (the second liquid ) is manually filled into the second cycle system. At the same time after the calculated amount of liquid nitrogen has been filled into the first cycle system from the vaporiser (<NUM>) at port (<NUM>). Liquid nitrogen absorbs heat in the vaporiser (<NUM>) approximately at ambient temperature, T1=<NUM>, and then vaporises and expands into a high pressure vapour at P1=12Mpa. This high pressure vapour also fills the storage tank (<NUM>) and piping (<NUM>) up to valve (<NUM>). The high pressure vapour then flows along piping (<NUM>) and through the valve (<NUM>) into the high pressure expander (<NUM>), where it undergoes adiabatic expansion and propels the piston wheel to turn, which outputs shaft work. After that, the pressure of the high pressure vapour falls to <NUM>. 1Mp (P2) and the temperature of the vapour proportionally falls to <NUM> (T2), which is within the liquefying temperature range of nitrogen (<NUM> to <NUM>). The nitrogen vapour liquefies to form cryogenic liquid nitrogen.

For example: nitrogen gas can be seen as an ideal gas, calculated according to the ideal gas adiabatic expansion state equation; When T<NUM>=<NUM>, P<NUM>=12Mpa, P<NUM>=<NUM>. 1Mpa, κ (specific heat ratio) =<NUM>, final state temperature T<NUM> can be calculated as below; <MAT> <MAT>.

The cryogenic liquid nitrogen's pressure is then raised and pumped by high pressure working fluid pump (<NUM>) back into the vaporiser (<NUM>) at a pressure of 12Mpa, where it undergoes an isobaric absorbing heat process and vaporise into a high pressure nitrogen vapour at <NUM> times the initial liquid nitrogen volume, and the pressure at 12Mpa. This process repeats to form the "cryogenic working fluid thermodynamic - refrigeration cycle" or "the first cycle". In this first cycle, the high pressure expander (<NUM>) outputs mechanical work and cryogenic liquid. The high pressure working fluid pump (<NUM>) consumes work.

In most areas that are inhabited by humans, the ambient temperature usually ranges between -<NUM>° C to +<NUM><NUM>C. Even in colder regions (for examples where the temperature is -<NUM><NUM>C), there is still a large temperature difference between liquid nitrogen (at -<NUM>) and air, therefore the liquid nitrogen can still absorb air heat energy, vaporise and expand into high pressure vapour and do work. If used in summer and in tropical and temperate regions, not only will energy be generated but at the same time the refrigeration and air conditioning functions are also easily obtained.

The extreme pressure of liquid nitrogen (at temperature range between -<NUM> to -<NUM><NUM>C) absorbing heat, vaporising and expanding under room temperature (of <NUM>) is very high and can reach 75MPa. This provides the basis for applying "Working Fluid's Gas/Liquid Phase Change Cycle".

According to ideal gas adiabatic expansion equation of state; T2/T1= (P2/P1) κ- <NUM>/κ, after high pressure nitrogen vapour has expanded adiabatically, the temperature drop is directly proportional to the pressure drop. Therefore, the criteria for setting the apparatus's first cycle's primary pressure (P1) should be such that the final temperature (T2) of working fluid after it has expanded adiabatically should fall within its liquefaction temperature range. If not the, primary pressure (P1) will be too high, the final temperature (T2) drop will be too low and T2 will surpass the liquefaction temperature range (for example, N2, <NUM> to <NUM>) and enter the solidifying temperature range (<<NUM>), in which case liquid nitrogen will solidify and block the piping (<NUM>), thereby disrupting the first cycle.

In the same way, if P1 is too low, T2 will not fall to the liquefaction temperature range and the working fluid will not be able to liquefy and will remain in a gaseous state. Because the working fluid pump (<NUM>) can only pump a liquid and cannot pump a gas, the first cycle will also be disrupted. In such a case, one may replace the working fluid pump (<NUM>) with a compressor and the first cycle could theoretically continue. However, the first cycle efficiency and net work output will be greatly reduced.

The invention is able to use natural gas (for example Nitrogen, Helium, Air, CO2 etc) as working fluid. This is because, firstly, they have excellent cryogenic properties in their liquid state well below ambient temperature and hence can absorb a lot of ambient heat energy in order to vaporise into high pressure vapour. Secondly, the heat absorption properties and specific heat of such a substance are excellent and energy density is large (can reach 300Kj/Kg). Thirdly, such substances are natural, harmless and are easily obtained.

The invention as described above can be used in many different ways according to different requirements. Some of the uses are described below:
Using refrigeration capacity: In the second cycle, the heat exchange system can use antifreeze (having a lower freezing point of -<NUM><NUM>C) as a heat-transfer liquid, and the temperature of cold air that leaves the heat exchanger (<NUM>) able to be adjusted for the following functions: for cooling electronic equipment such as a CPU, for air conditioning (at approximately <NUM> to <NUM>), for cool storage (at approximately <NUM> to <NUM><NUM>C), for refrigeration (at approximately <NUM>), for freezing (at approximately -<NUM> to -<NUM>) etc..

Similarly, the first cycle uses the dry air used for heat exchange in the vaporiser (the vaporiser needs to be especially designed for this working condition). The resultant cold air after the temperature adjustment can be used for freezing (at approximately -<NUM> to -<NUM>), materials treatment, cooling of machining, freeze grinding (at approximately -<NUM> to - <NUM>), etc. It can also be used to directly liquefy air (at approximately -<NUM> to -<NUM>) to make air products.

Utilisation of Power: The mechanical work output by the high pressure expander (<NUM>) is high quality energy and can be used as the power source for all mechanically powered machinery or machineries such as but not limited to vehicles, ships and aircraft. Alternatively, the mechanical work output by the high pressure expander (<NUM>) can be further converted into electricity, thermal energy and other types of energy for other uses. For example, the invention can provide a 20KW model per household or business which can be used to provide power, refrigeration, air condition and fresh water making needs. The size of the components and the overall apparatus can be designed according to use. The apparatus of the invention can be designed as a micro-generator device for powering electronic devices (for example computers, cell phone etc), robots, outdoor equipment etc..

Air water production: The invention can be used to make fresh water from the air. In such cases, the air heat exchanger (<NUM>) should be specifically designed with the requirements of good air flow, highly efficient heat exchange and convenient collection of condensate. The reaching of the dew point temperature and maximum condensation of the air moisture can be obtained by adjusting the working temperature of the heat exchanger according to the air humidity. High quality fresh water can be obtained by purifying and/or mineralising the condensate collected. For example, a domestic model of the invention (20KW model), working at a room temperature of <NUM>, relative humidity of <NUM>% (Humidity of air: <NUM>/Kg), heat exchange temperature difference of +/- <NUM><NUM>C, can produce fresh water at the rate of <NUM> per hour. After the fresh water has been used for drinking, cooking, cleaning, irrigating, etc., the waste water will be released into the environment again because of evaporation, and will rejoin the natural water cycle. The air moisture will be harnessed again by the present invention, thereby providing a method of directly producing fresh water from the air.

Dehumidifying Use: When the air goes through the heat exchanger (<NUM>), the water vapour condenses and the air will be dehumidified. The apparatus of the present invention can be used to cycle the air to reach the required humidity, thus obtaining the dehumidifying function.

Utilisation of thermal energy in bodies of water: Bodies of water such as rivers, lakes, oceans, underground water, etc., contain a large amount of thermal energy. However, since this water cannot be as conveniently used as air, the invention focuses on the atmosphere as the main heat source. In order to utilise the thermal energy of water, the second cycle which is a closed system can be changed into an open system. That is to say, the entry port of the circulation pump (<NUM>) can be connected directly to the water source and that water can be circulated to the vaporiser (<NUM>) for heat exchange. Such designs can be suitable for ship or other maritime use.

The expander (<NUM>) used in the above first cycle will now be described in detail.

The piston wheel expander shown in <FIG> is one embodiment of the aforementioned high pressure expander (<NUM>).

<FIG> show various components of the expander. The expander (<NUM>) consists of an outer cylindrical casing (<NUM>), ends (<NUM>), gasket ring (<NUM>) having U-shaped cross-section, piston wheel (<NUM>), band shaped sealing ring (<NUM>, <NUM>'), shaft (<NUM>) etc. The expander includes at least one working fluid inlet (<NUM>) and outlet (<NUM>) on the casing (<NUM>), connection tubes (<NUM>) and support (<NUM>). Working fluid inlet (<NUM>) and outlet (<NUM>) that connect to the casing (<NUM>) at a tangent and the cross-section areas of a base (<NUM>) of the inlet (<NUM>) and the outlet (<NUM>) are equal to the thrust surface (<NUM>) area. Having such a larger cross-section area at the base (<NUM>) allows the working fluid to enter and exit more effectively as well as "enhances a starting thrust". As shown in <FIG> and <FIG>, each end (<NUM>) of the expander (<NUM>) has a bearing (<NUM>) and bolt holes (<NUM>) and the convex base structure (<NUM>) on the ends (<NUM>). The convex base structure (<NUM>) of ends (<NUM>) can be seen more clearly in <FIG>. During assembly, the convex base structure (<NUM>) is to be embedded into the ends of the casing (<NUM>) for "stable placement and sealed to ensure highly accurate concentricity". During assembly, a gap between the each end of the casing (<NUM>) and the each ends (<NUM>) is sealed by a gasket ring (<NUM>) having a U shaped cross section. The structure of the gasket ring (<NUM>) can be seen clearly in <FIG>.

The piston wheel (<FIG>) will now be described in detail. The outer circumference of the piston wheel (<NUM>) has three circles of piston chambers (<NUM>), as seen in <FIG> & <FIG>. However, such circles can be designed according to the criteria of machine body compactness and sufficient working displacement. Connection tubes (<NUM>) connect the three circles of piston chambers (<NUM>) in series to "obtain sufficient working displacement for the high pressure expander's isometric working process". The piston chamber's (<NUM>) outer circumference has sealing ring grooves (<NUM>) as seen in <FIG> & <FIG> for at least one band shaped sealing ring (<NUM>, <NUM>'), as shown in <FIG> & <FIG>.

To ensure overall structural strength, each single piston chamber's (<NUM>) volume (V) should be as small as possible. That is to say, the quantity of piston chambers can be as many as possible and, as the quantity increases, the volume of each chamber proportionally decreases). The thrust surface's (<NUM>) area needs to be as large as possible and the length (L) of the side needs to be as long as possible.

This is due to: H (enthalpy) =U+PV, W (Work) =FS, F (Force) = PA. To ensure that the enthalpy (H) of the high pressure gas can be completely converted into work within sufficient working displacement (S), (given that H=W, U+PV=FS, U (internal energy) and P (pressure) are the high pressure working fluid's primary state parameters (H1, P1)), once maximum working pressure has been determined, it cannot be adjusted, but V(volume), F(force), A(area) and other parameters can be selected accordingly when designing the model of the invention. Through minimising V, increasing L (length) → A (area) → F (force) to achieve the shortest possible sufficient working displacement (S) so that the machine body is compact and practical.

<FIG> show a first example of a band shaped sealing ring (type <NUM>, <NUM>) of the first type that is formed by a number of substantially square shaped seal links (<NUM>), each having square shaped slots or apertures. The seal links (<NUM>) are connected in a jigsaw-like way. The outer circumference of the piston chamber (<NUM>) has sealing ring grooves (<NUM>) as shown in <FIG> & <FIG>. The links (<NUM>) should be fitted one by one into the groove (<NUM>) to form a circle. Each circle of the piston chamber (<NUM>) is matched with the circle of the band shaped sealing ring (<NUM>) formed by a number of shaped links (<NUM>). The outer diameter (R1) of the band shaped sealing ring (<NUM>) shown in <FIG> is substantially the same as the inner diameter (R2) of the casing (<NUM>), as shown in <FIG>. The exterior of the band shaped sealing ring (<NUM>) tightly abuts the interior of the casing (<NUM>) as shown in <FIG>. Similarly, the inner diameter (R3) of the band shaped sealing ring (<NUM>) shown in <FIG> and the diameter (R4) of the circumference surface of the piston chamber's (<NUM>) sealing ring groove (<NUM>) shown in <FIG> are substantially the same.

The two ends of the seal links (<NUM>) have a stabilising tenon (<NUM>) that is adapted to be fitted into the mortise (<NUM>) (see <FIG>) thereby ensuring that the seal links (<NUM>) in the band shaped sealing ring (<NUM>) do not dislocate during operation. The inside of the seal links (<NUM>) has a perimeter self sealing gap (<NUM>) as seen in <FIG>.

As seen in <FIG>, the inside wall of the self sealing gap (<NUM>) of the seal links (<NUM>) has a slightly protruding spring leaf or thin wall (<NUM>, <NUM>). When the seal links are installed through hoop stress, the thin wall (<NUM>, <NUM>) of each seal link (<NUM>) will lie flat and tightly against the circumferential surface of the piston chamber's (<NUM>) sealing ring groove (<NUM>).

During operation, the high pressure gas will fill up the piston chamber (<NUM>) and the self sealing gap (<NUM>) of each of the seal links (<NUM>) of the band shaped ring (<NUM>). Under the fluid pressure, the top, bottom and outside of the self sealing gap (<NUM>) of the seal links (<NUM>) will be pushed to lie against each other, thereby achieving excellent flexible self sealing.

The outer circumference (<NUM>) of the seal links (<NUM>) is a friction surface. If, after the long term running of the apparatus, there is wear on the friction surface (<NUM>) of the seal links (<NUM>), this will lead to deviations in the high precision measurement of components. In such cases, the circle of seal links (<NUM>) or the band shaped sealing ring (<NUM>) under the double effects of the elasticity of the self sealing gap's (<NUM>) thin wall (<NUM>, <NUM>) and working fluid pressure, will radial expand tightly against the inner wall of the cylindrical casing (<NUM>) and the circumferential surface of the piston chamber's (<NUM>) sealing ring groove (<NUM>), thereby creating an excellent elastic/flexible seal and automatically compensating for the wear.

As shown in <FIG>, the two ends of the seal links (<NUM>) are connected by mortise (<NUM>) and tenon (<NUM>) to form the band shaped sealing ring and there is a flexible spring (<NUM>) located on each of the two sides of the interior of the mortise (<NUM>), which after the installation pushes tightly against the tenon (<NUM>). This will have excellent self sealing under the fluid pressure and can eliminate any leaks from the gap between the mortise (<NUM>) and tenon (<NUM>).

<FIG> show a different type of band shaped sealing ring (type <NUM>, <NUM>'). Unlike the band shaped sealing ring (type <NUM>, <NUM>) of <FIG>, this band shaped sealing ring (type <NUM>, <NUM>') of <FIG> is a single piece of processed metal. The outer diameter (R5) of the band shaped sealing ring (<NUM>') and the inner diameter (R2) of the casing are substantially the same. The exterior of the band shaped sealing ring (<NUM>) tightly abuts the interior of the casing (<NUM>). The inner diameter (R6) of the band shaped sealing ring (<NUM>') shown in <FIG> and the diameter (R4) of the circumference surface of the piston chamber's (<NUM>) sealing ring groove (<NUM>) shown in <FIG> are substantially the same. The structure of the band shaped sealing ring (type <NUM>, <NUM>') is similar to the structure of the band shaped sealing ring (type <NUM>, <NUM>) of <FIG>. Similar to square shaped apertures in the seal links (<NUM>) forming square shaped apertures uniformly in the band shaped sealing ring (<NUM>) of <FIG>, there are square shaped apertures that are uniformly formed on the circumferential surface of the band shaped sealing ring (<NUM>) as shown in <FIG>.

As shown in <FIG>, the band shaped sealing ring (<NUM>') is a split ring having two ends connected by joints or connectors. The joints or connectors are in the form of a mortise (<NUM>) in one end and a tenon (<NUM>) in the other end. Similar to the band shaped sealing ring (<NUM>) of <FIG>, each of the two sides of the interior of the mortise (<NUM>) of the band shaped sealing ring (<NUM>') also has a flexible spring (<NUM>) fitted which, after the installation, pushes tightly against the tenon (<NUM>). This will have create a seal under the fluid pressure and can eliminate any leaks from the gap between the mortise (<NUM>) and tenon (<NUM>).

As can be seen in <FIG>, the band shaped sealing ring (type <NUM>, <NUM>') has many half-circle shaped stabilising keyholes (<NUM>) at two sides of one end. The wall surface of the piston chamber's (<NUM>) sealing ring groove (<NUM>) can also have half-circle keyholes (so that after the installation of band shaped sealing ring (<NUM>'), the half circle shaped stabilising keyholes (<NUM>) will form a perfect circle (<NUM>)with the corresponding half-circle key holes on the wall surface of the groove (<NUM>). Once stabilising keys (not shown) are inserted there will be no dislocation of the band shaped sealing rings (<NUM>') when they turn.

The piston wheel shaft (<NUM>) has two ends (<NUM>, <NUM>) that extend outwards, with one end (<NUM>) being used to drive the high pressure working fluid pump and the other end (<NUM>) used to output work. This design of the expander (<NUM>) is convenient and compact.

As shown in <FIG>, the vaporiser (<NUM>) uses finned tubes (<NUM>) located inside a high pressure shell structure (<NUM>). Because the vaporiser (<NUM>) in the context of the present invention is used under cryogenic and high pressure conditions, all the components of the vaporiser (<NUM>) should be made out of a material that is able to withstand cryogenic temperatures and high strength. The examples of such materials are cryogenic steel, stainless steel, high strength aluminium alloy etc. The finned tubes (<NUM>) can include high heat conductible material, such as cooper, aluminium alloy, etc., having high pressure ends (<NUM>) and a high pressure shell (<NUM>) that are assembled in a cluster structure (<NUM>) by welding. The ports for entry (<NUM>) and exit (<NUM>) on the top and bottom of the two sides of the vaporiser (<NUM>) are for the second liquid used or to be used in the second cycle described before.

The ports for entry (<NUM>) and exit (<NUM>) on the top and bottom of the other side of the vaporiser (<NUM>) are for the first fluid used or to be used in the first cycle described above. When the high pressure first fluid such as liquid nitrogen (at <NUM> - <NUM>, 12MPa) flows inside shell (<NUM>) side, the exterior of finned tubes (<NUM>) will need to bear pressure, akin to the working stress bearing arches. This way the finned tubes (<NUM>) function well in pressure-bearing with a larger heat-exchange surface area. Low pressure second liquid such as water or antifreeze at <<NUM>. 1Mpa flows through the inside of the finned tubes (<NUM>). The interior walls of the finned tubes (<NUM>) have small heat-exchange surface areas, but because the specific heat of the heat-transfer liquid, such as water, is large, it will flow easily and the amount of heat-exchanged will be large. Thus the gas - liquid heat exchange method constructed in this way is relatively harmonious. As a result, there is excellent heat exchange.

Air and the second liquid exchange heat through the air heat exchanger, in which air heat is absorbed by the second liquid. The air temperature drops and the second liquid temperature rises. As the air temperature drops, it produces refrigeration capacity. When the air temperature falls to the dew point, the moisture in air condenses. This produces fresh water. Since moisture in the air has turned into condensation, the air is now dry. This is the dehumidifying function. As the second liquid becomes warm, it is circulated to the vaporiser, where it exchanges heat with the first fluid of the first cycle, thereby transferring heat energy to the first fluid.

As shown in <FIG>, at various positions in each stage examples of typical phase, temperature and pressure are described and shown:.

In between the vaporiser and expander, V can be approximately equal to I, and in between the working pump and vaporiser, IV can be approximately equal to III.

Throughout the description of this specification the word "Apparatus" refers to a "Frost - Free Two Stage Cycle Thermodynamic - Refrigeration System" comprising the "Cryogenic Working Fluid Thermodynamic -Refrigeration Cycle" or "the First Cycle" and "Frost free Heat Exchange Cycle" or "the Second Cycle". Furthermore, the words "cryogenic working fluid" and "first fluid" are used interchangeably, and "heat-transfer liquid" and "second liquid" are used interchangeably.

Claim 1:
An apparatus for use with cryogenic working fluid as a working substance, the apparatus comprising at least a vaporiser (<NUM>), a high pressure expander (<NUM>), a high pressure working fluid pump (<NUM>), an ambient heat exchanger (<NUM>), a circulation pump (<NUM>), a generator (<NUM>), pipes (<NUM>), valves (<NUM>), and sensors, which are fluidly and operatively interconnected together, the at least one vaporiser (<NUM>) is configured to produce high pressure vapour the apparatus being characterized in that the at least one vaporizer (<NUM>) is installed between the high pressure working fluid pump (<NUM>) and the high pressure expander (<NUM>), a shell side of the vaporiser (<NUM>) is configured to receive the working substance, and a tube side is configured to receive low pressure heat transfer liquid, so that in use the working substance absorbs thermal energy from ambient air, vaporises into high pressure gas which then propels the high pressure expander (<NUM>) to turn and output mechanical work and refrigeration capacity, and the ambient heat exchanger (<NUM>) outputs refrigeration, condensation and dry air.