WO2008155543A2 - Pompe à chaleur - Google Patents

Pompe à chaleur Download PDF

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Publication number
WO2008155543A2
WO2008155543A2 PCT/GB2008/002080 GB2008002080W WO2008155543A2 WO 2008155543 A2 WO2008155543 A2 WO 2008155543A2 GB 2008002080 W GB2008002080 W GB 2008002080W WO 2008155543 A2 WO2008155543 A2 WO 2008155543A2
Authority
WO
WIPO (PCT)
Prior art keywords
heat
heat pump
bed
heat transfer
beds
Prior art date
Application number
PCT/GB2008/002080
Other languages
English (en)
Other versions
WO2008155543A3 (fr
Inventor
Richard Powell
Derek William Edwards
Andrew Wilson
Simon James Redford
Original Assignee
Thermal Energy Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB0711829A external-priority patent/GB0711829D0/en
Priority claimed from GB0715774A external-priority patent/GB0715774D0/en
Application filed by Thermal Energy Systems Ltd filed Critical Thermal Energy Systems Ltd
Publication of WO2008155543A2 publication Critical patent/WO2008155543A2/fr
Publication of WO2008155543A3 publication Critical patent/WO2008155543A3/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B25/00—Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
    • F25B25/02—Compression-sorption machines, plants, or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B17/00—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B17/00—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type
    • F25B17/08—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type the absorbent or adsorbent being a solid, e.g. salt
    • F25B17/083—Sorption machines, plants or systems, operating intermittently, e.g. absorption or adsorption type the absorbent or adsorbent being a solid, e.g. salt with two or more boiler-sorbers operating alternately
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00—Adapting or protecting infrastructure or their operation
    • Y02A30/27—Relating to heating, ventilation or air conditioning [HVAC] technologies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]

Definitions

  • This invention relates to a heat pump device particularly for air conditioning, refrigeration and heat pumping systems.
  • the device relates especially to systems that contain no fluids known to have adverse effects on the stratospheric ozone layer or to have high global warming potentials relative to carbon dioxide.
  • the device may provide a direct replacement for any application that currently employs a mechanical vapour recompression or fluid/solvent pair absorption cooling or heat pumping system.
  • the term 'heat pump' describes any powered device which moves heat from a source to a sink against a thermal gradient.
  • a refrigerator is a particular type of heat pump where the lower temperature is required for the intended application.
  • the term 'heat pump' is also used in a more limited sense than in this specification to describe a powered device which moves heat from a source to a sink against a thermal gradient where the higher temperature is required.
  • the distinction between a refrigerator and a narrowly-defined heat pump is merely one of intended purpose, not operating principle. Indeed, many air conditioning systems are designed to supply either heating or cooling depending upon the user's need at a specific time.
  • Chlorofluorocarbons CFCs e.g. CFC 11, CFC 12
  • hydrochlorofluorocarbons HCFCs eg HCFC 22, HCFC 123
  • CFCs Chlorofluorocarbons
  • HCFCs hydrochlorofluorocarbons
  • HCFCs hydrochlorofluorocarbons
  • the Montreal Protocol an international environmental agreement signed by over 160 countries, mandates the phase-out of CFCs and HCFCs according to an agreed timetable.
  • HFCs hydrofluorocarbons
  • HFCs hydrofluorocarbons
  • HFCs do not deplete stratospheric ozone they are known to contribute to global warming.
  • governments have undertaken to limit or cease the manufacture and release of these compounds.
  • the fluids in devices intended to replace HFC-containing units must have very low or preferably zero global warming potential.
  • they should be compounds that are found naturally and whose properties are well understood so that damage to the environment from anthropogenic releases can be avoided.
  • devices should be at least as energy efficient as the HFC containing units they are replacing to ensure that their contributions to global warming due to fossil fuel power station emissions are no greater.
  • the devices should have better energy efficiencies.
  • WO-2006/111773 disclosed a heat pump in which a temperature difference is established between two heat exchangers by inducing cyclical expansion and compression pulses in a coupling fluid which passes through an adsorbent porous solid located between the heat exchangers.
  • a heat pump including first and second adsorption beds, each bed including a porous solid, the first bed having a first heat exchanger and the second bed having a second heat exchanger; a circuit for working fluid communicating between the beds; valve means for switching flows of heat transfer fluid through the first and second heat exchangers; a compressor connected between the valve means adapted to cause working fluid to flow within the circuit between the beds; the working fluid comprising a reactive gas capable of adsorption and desorption by the porous solid; the first heat exchanger including a first conduit for a heat transfer fluid; the second heat exchanger including a second conduit for a heat transfer fluid; and a bypass valve connected between the valve means in parallel to the compressor and adapted when opened to allow flow between the beds bypassing the compressor.
  • a heat pump including first and second adsorption beds, each bed including a porous solid, the first bed having a first heat exchanger and the second bed having a second heat exchanger; a circuit for working fluid communicating between the beds; a compressor adapted to cause working fluid to flow within the circuit between the beds; the working fluid comprising a reactive gas capable of adsorption and desorption by the porous solid; the first heat exchanger including a first conduit for a heat transfer fluid; the second heat exchanger including a second conduit for a heat transfer fluid; valve means for switching flows of heat transfer fluid through the first and second heat exchangers; and a number of adsorption beds, the number being 2N wherein N is a positive integer and wherein each bed has an inlet and an outlet; the heat exchangers being arranged in a plurality of arrays, each array comprising an input for heat from a flow of the heat transfer fluid or an output for heat to the heat transfer fluid; wherein the heat exchangers of each array
  • reactive gas used in this specification is intended to refer to a gas which may be reversibly adsorbed onto the porous solid, i.e. by physisorption.
  • the device comprises a further heat exchanger located between the compressor and the compressor beds, preferably immediately after the compressor between the valve means and adapted to remove heat of compression from the working fluid gas before the latter comes into contact with an adsorption bed.
  • the bypass valve allows pressure equalisation without a need to stop the compressor. Stopping and restarting a compressor is energy inefficient and will accelerate compressor wear. Furthermore, it may enable a pressure or temperature gradient to be established along the beds. This gradient may advantageously increase the temperature difference between the heat transfer fluid inlet and outlets, maximising the utilisation of the compressor in contrast to the disclosure of WO-2006/111773.
  • the working fluid may comprise a gas or mixture of gases, including the reactive gas in combination with a porous solid that is capable of adsorbing the gas.
  • a porous solid that is capable of adsorbing the gas.
  • carbon dioxide and a micro-porous/nano-porous solid such as activated carbon.
  • the operation of the device provided below uses CO 2 and coconut carbon as an example but is not intended to be limitative.
  • the reactive gas may be selected from the group consisting of: hydrocarbons, ammonia, hydrogen, HFCs, fluoro-iodides, unsaturated fluorinated compounds containing 2 to 6 carbon atoms, fluoro-olefins containing trifluorovinyl groups, CO 2 , nitrogen and mixtures thereof.
  • the porous solid may be selected from the group consisting of:
  • Polymers of intrinsic porosity are polymers which derive their porosity by having much larger free volumes than conventional polymers. These polymers may be generated during polymerisation by using monomers with rigid 3-dimensional structures which cannot pack closely together, as reported in Angewcmdte Chemie International Edition (Vol. 45, Issue 11, DOI: 10.1002/anie.200504241; p. 1804), McKeown et al. In previous microporous solids, solids pores have been generated in the processing of polymers subsequent to their syntheses.
  • the working fluid may comprise a reactive gas and an additional gas which may have a • higher thermal conductivity than the reactive gas.
  • the additional gas may be selected from the He 5 Ne 5 H 2 D 2 DH and mixtures thereof. Use of He is preferred when the reactive gas is CO 2 .
  • a temperature difference is established between the two beds by desorbing the reactive gas from one bed, which cools down, and adsorbing the reactive gas on a second bed, which is caused to heat up.
  • the adsorbent beds are constructed to facilitate heat exchange with their surroundings.
  • the device thus also comprises a first gas or liquid stream as a heat transfer fluid, which removes heat from the hot heat exchanger and rejects it into a suitable heat sink, and a second stream which supplies heat from a heat source to the cold adsorption bed.
  • the adsorption bed heat exchangers may be designed to have an elongate or labrynthine flow path, for example with at least one dimension which is significantly longer than at least one other dimension.
  • the working fluid enters an adsorbent bed heat exchanger at one end of the long dimension and leaves at either the same end or the opposite end.
  • the quantity of working fluid that a bed can adsorb may be limited by the mass of the adsorbent, its adsorbent properties, the applied pressure and temperature. When this limit has been reached appropriate valves in the circuit are operated so the roles of beds are reversed in order to ensure that heat pumping continues. This is commonly called a "swing" process.
  • FIGS. 1 and 2 diagrammatically illustrate a heat pump
  • Figure 3 illustrates a regenerative heat pump
  • Figure 4 illustrates a regenerative heat pump wherein two beds are connected
  • Figure 5 illustrates regenerating heat exchange with heat pumping
  • Figure 6 is a diagram showing a regenerative heat pumping cycle
  • FIGS 7 and 10 illustrate a first heat pump in accordance with this invention.
  • FIGS 11 and 12 illustrate further embodiments of this invention
  • FIG. 13 illustrates an air conditioner in accordance with this invention
  • Figure 14 illustrates a 4 bed embodiment of this invention
  • Figure 15 illustrates a 6 bed embodiment of this invention
  • FIGS. 16 to 18 illustrate the construction and performance of a heat pump in accordance with this invention
  • FIG. 19(a) to (c) illustrate an alternative bed configuration
  • Figure 20 illustrates a 4-bed, 2 array heat pump using the bed shown in Figure 19;
  • FIG 21 (a) and (b) illustrates operation of the heat pump shown in Figure 20.
  • Figure 1 illustrates a CO 2 circuit which comprises: a compressor 1.1; adsorption beds 1.2 and 1.3; a heat exchanger 1.4 to remove the heat of compression; three- way, powered valves 1.5 and 1.6 which allow the beds 1.2 and 1.3 to be placed alternatively under compression or suction; and a compressor powered by-pass valve 1.7.
  • Figure 2 shows a heat pump arrangement and indicates the air flow configured to provide cold air to a room with the simultaneous removal of stale air.
  • the circuit comprises; adsorption beds 1.1 and 1.2; a powered air valve or damper 2.3; a pusher fan 2.4 and a suction fan 2.5; a negative heat (commonly referred to as "coolth”) sink is shown at 2.6.
  • the arrows represent the following flows: 2.7 external fresh entering device; 2.8 room stale air entering device; 2.9 stale being exhausted from device after heating to a temperature higher than the external temperature by bed 1.3; 2.10 fresh air entering after being cooled to the desired low temperature by bed 1.1.
  • Figures 1 and 2 show the system at one stage of its swing cycle. When the various valves are actuated the cooling and heating functions of beds 1.2 and bed 1.3 are interchanged.
  • the system also comprises pressure and temperature sensors, pneumatic or electric valve actuators and control circuitry which enables the flows of CO 2 and air to be swung between the beds.
  • a feature of the device claimed in this invention is the integration of three fundamental heat transfer processes in a single unit: a compressor driven adsorption cooling device, a regenerative/recuperative heat exchanger (RHX) and passive (i.e. not driven) adsorption/desorption.
  • recuperative heat exchange has taken the form of a heat wheel.
  • the two or more adsorption beds perform this duty.
  • the simple regenerative or heat exchange aspect of the present device is explained in relation to Figure 3 which represents fresh air flowing into a room 3.1 from outside a building 3.4 without heat pumping across two air streams 3.5 and 3.6, and without the beds being connected so that no refrigerant gas can pass between them.
  • Bed 3.2 heats exhaust air while bed 3.3 cools incoming fresh air. This process will continue until bed 3.2 is substantially cooled along the whole of its length while bed 3.3 is correspondingly heated to the temperature of the external air.
  • Figure 5 shows a system in which there is pumping of CO 2 , represented by arrow 5.7, from bed 5.3 to bed 5.2 using compressor 5.8. For clarity only the beds and the compressor are shown. The other components shown in Figure 1 are omitted.
  • the temperature of bed 5.3 is lowered by CO 2 desorption while that of bed 5.2 is simultaneously raised by CO 2 adsorption.
  • the exhaust air 5.5 from room 5.1 is heated to a temperature above the external air 5.4 and the in-coming air 5.6 is cooled below the room exhaust air temperature.
  • This arrangement augments the two recuperative heat transfer effects described in the previous paragraphs. In other words the system is operating both as a recuperator and a heat pump.
  • An important advantage of this invention is the provision of circuit designs that allow this combined heat recuperation/heat pumping cycle to be realised in practice.
  • thermodynamic cycle on which the device operates are summarised in Figure 6. They are: CO 2 pressure equalisation; CO 2 pumping from one bed to the other using the compressor; and recuperative heat transfer.
  • the device operates in a cycle where the each stage is distinct and separate from each other, with one stage essentially complete before the next stage commences.
  • the stages overlap so that one stage commences before the previous stage has been completed.
  • FIG. 7 One method of operating the device shown in Figures 1 and 2 is explained in more detail by considering a cycle in Figure 7, where the adsorption beds correspond to the similarly numbered beds in Figures 1 and 2.
  • a convenient starting point in the cycle is shown in Figures 7a and 7c with bed 1.2 at the temperature of the external air (35 0 C) and at low internal CO 2 pressure , while bed 1.3 is at the temperature of the exhaust air (20 0 C) and high internal pressure.
  • the pressure and temperature values shown in Figures 7 to 10 are taken from a cycle calculation.
  • Stage 1 Valve 1.7 is opened to allow CO 2 to flow through directly from bed 1.2 to bed 1.3.
  • the pressure difference between the two beds decreases so the temperature of bed 1.2 decreases due to gas desorption. The temperature ultimately drops to the temperature required for entry of air into the room.
  • the temperature of bed 1.3 rises because of gas adsorption to a value greater than the temperature of external air.
  • the air valve 2.3 is switched to its alternative position as indicated in Figure 7d and CO 2 circuit valves are switched to their alternative positions shown in Figure 7b.
  • Stage 2 ( Figure 8): External fresh air 2.7 is sucked by fan 2.5 via valve 2.3 over bed 1.2 which is thus progressively heated along its length as indicated by Figures 8a and 8b, while the air stream is cooled, entering the room at 13.5 0 C .
  • the low temperature of the bed 1.2 is maintained by CO 2 desorption under the suction of the compressor 1.1.
  • the cooling of the air stream can be attributed to a combination of this desorption and the coolth associated with the heat capacity of the bed derived from previously being cooled by outgoing stale air. This is a combination of heat pumping and regenerative heat transfer, in other words the two processes overlap.
  • Stale cool air from the room 2.8 is forced by fan 2.4 over bed 1.3 exiting the bed at 41.5 0 C.
  • the bed is progressively cooled as indicated in Figures 8a and 8b.
  • the high temperature of bed 1.3 is maintained by CO 2 adsorption driven by the compressor.
  • Pumping CO 2 from bed 1.2 to 1.3 with heat transfer to and from the air streams described will ultimately result in bed 1.2 being at a low pressure and at the temperature essentially that of the external air, with bed 1.3 being at high pressure and at essentially the temperature of the exhaust stale air exiting the room. This position is shown in Figure 9a.
  • Stage 3 ( Figure 9): At this point in the cycle further heat transfer between the beds and the air streams is no longer possible because the maximum acceptable pressure difference has been established between the beds and temperature gradient along the beds has is no longer adequate to provide the required cold and hot air streams.
  • the roles of the beds are reversed by equalising the pressure between the two beds by opening the compressor bypass valve 1.7. Bed 1.3 becomes cold as CO 2 desorbs from the porous solid and bed 1.2 becomes hot as CO 2 adsorbs.
  • the pressure and temperature conditions of the two beds when the pressure equalisation is essentially complete are shown in Figure 9b.
  • Valve 1.7 is closed; the air valve 2.3 set to the position shown in Figure 9d and valves 1.5 and 1.6 to the positions shown in Figure 9b. It will be recognised that Figures 9b and 9d are similar to Figures 7a and 7b but with the roles of beds 1.2 and 1.3 reversed.
  • Stage 4 ( Figure 10): External fresh air 2.7 is sucked by fan 2.5 via valve 2.3 over bed
  • bed 1.2 is maintained by CO 2 adsorption driven by the compressor. Pumping CO 2 from bed 1.3 to 1.2 with heat transfer to and from the air streams described will ultimately result in bed 1.3 being at a low pressure and at the temperature essentially that of the external air, with bed 1.2 being at high pressure and at essentially the temperature of the exhaust stale air exiting the room. This position is shown in Figure 7a. The device has completed a full cycle and returned to the original starting point.
  • the energy efficiency of a system can be represented by its Coefficient of Performance
  • the COP for an air conditioner or refrigerator is the ratio of the cooling duty provided by the evaporator to the power supplied to electric motor to achieve that duty.
  • the COP of a system operating in heat pumping mode to supply heat is heat provided by the condenser divided by the electric power input to the motor.
  • the COP calculated for the adsorption-based unit, which is the subject of this invention, was 6.6 compared to 4.0 for the conventional unit, i.e. the TESL unit was 65% more efficient.
  • the temperature swing obtained is determined by the combined heat capacity of the carbon or other adsorbent and the metal. Good heat transfer from the bed to the air stream requires the incorporation of high thermal conductivity material into the carbon granules; but this reduces the temperature swing.
  • the approach of this invention can provide a workable compromise between having both an adequate temperature swing and adequate heat transfer.
  • the hot and cold temperatures generated may depend upon the specific applications for which embodiments of this invention are employed, in particular whether refrigeration or air conditioning is required.
  • air conditioning is taken to include both room cooling and heating.
  • Devices that can provide both heating and cooling depending upon the requirements of the user are sometimes called reversible air conditioners.
  • the heat transfer fluid will be generally be air.
  • cooling mode the cold temperature with generally be in the range 5 to 15 0 C while hot temperature will generally be in the range 35 to 60 0 C.
  • Cooling powers will typically range from 1 kW to 30 kW.
  • heating mode the output temperature to the room will be typically be 15 to 35 0 C, preferably 20 to 30 0 C and input temperatures from the outside air typically in the range from about 2 to 15 0 C.
  • Heating powers will typically be in the range from about 2 to about 50 IcW.
  • Alternative devices are adapted simply to provide heating and may generally be described as heat pumps. This is more a restricted meaning of the term than its scope in this specification.
  • the transfer fluid can be water which will be piped through each room where air will be blown over the cold water pipe to provide the required cooling.
  • This system is analogous to conventional chiller installations.
  • the temperature of the water fed into the system is typically in the range from about 5 to about 10 0 C and the water returning to the device is typically in the range from about 10 to about 15 0 C.
  • In heating mode the temperature of the water leaving the device is in the range from about 25 to about 40 0 C, while the return water is typically in the range from about 15 to about 30 0 C.
  • the device is used to provide refrigeration typically at temperatures down to -30 0 C.
  • equipment performance is optimised two or more stages. This approach is especially advantageous for temperatures below -20 0 C.
  • carbon dioxide is a good refrigerant for Rankine cycle heat pumps with condenser temperatures lower than O 0 C
  • the critical temperature of 31 0 C and high critical pressure of 72 bar means that it is unattractive for heat pumps where the output temperatures above O 0 C.
  • An especially preferred design comprises a device using a conventional heat Rankine cycle stage using carbon dioxide as the working fluid to pump heat from a temperature in the range generally -55 to -10 0 C and reject at a temperature generally in the range -20 to O 0 C to the low temperature side of a second stage device in accordance with the present invention.
  • This second stage may reject heat at temperatures of 35 to 70 0 C while operating at maximum pressures in the range 2 to 30 bar, typical of CFC, HCFC or HFC-based refrigeration equipment.
  • N 2 is preferred as a working fluid with a carbon adsorbent.
  • the preferred heat transfer fluid is atmosphere within refrigerated enclosure, which in many cases will be air. This design will provide cooling in the range -130° to -40 0 C and will reject heat in the range -55 to-25 0 C to higher temperature stage.
  • the temperature difference between each heat exchanger and an external, single phase heat transfer liquid is near-constant throughout the heat transfer process.
  • the difference does not change by more than 12°C, more preferably not more than 7°C and most preferably not more than 5 0 C.
  • any fluid which is chemically stable in the gaseous state and which can be reversibly adsorbed onto and desorbed from a suitable porous solid is technically acceptable for use in devices of this invention.
  • Preferred fluids include those that are already used in equipment based on other cycles, such as Rankine cycle and gas cycle heat pumps.
  • the working fluid may be a fiuorocarbon or a mixture of fluorocarbons boiling between -14O 0 C and 4O 0 C, preferably between -90 0 C and 0 0 C, more preferably between -9O 0 C and -20 0 C.
  • CFCs, HCFCs and HFCs are acceptable in those territories where their use is permitted but these are not preferred because of their adverse environmental effects.
  • Preferred fluids are those that occur naturally.
  • Hydrocarbons and hydrogen can be used in applications where flammability is not an issue. Ammonia may be used for applications where exposure to humans and animals can be prevented.
  • HFCs perfluoro-iodides and unsaturated fluorinated compounds containing 2 to 6 carbon atoms can be used. These preferably have global warming potentials relative to CO 2, preferably less than 150, more preferably less than 100, and most preferably less than 10.
  • Particularly preferred compounds are fluorinated olefins. More preferred are fluoroolefins containing a trifluorovinyl group. Even more preferred are fiuoro-olefms containing at least one hydrogen atom. Especially preferred are fluoro-propenes and their blends.
  • especially preferred working fluids comprise CO 2 , noble gases and N 2 and mixtures thereof. These combine low environmental impact with low toxicity and non-flammability.
  • the carbon dioxide can be mixed with an additional gas having a substantially higher thermal conductivity than CO 2 .
  • the ratio of the thermal conductivity of the gas to that of CO 2 is greater than about 1.5, more preferably greater than about 5 and most preferably greater than about 8.
  • Preferred additional gases include N 2 , Ne, D 2 , and DH. Dihydrogen (H 2 ) and helium (He) are especially preferred.
  • 'porous solid' may be used for materials with a wide range of properties. Many solids have a very limited porosity including the protective oxide layers found on metals.
  • the term, 'porous solid' is used to describe a material with a particular combination of properties.
  • the internal surface area of the porous solid is greater than about 10 m 2 g "1 , more preferably greater than about 100 m 2 g "1 , most preferably greater than about 1000 m 2 g "1 .
  • the void space in the porous solid may be distributed between a combination of macro-, meso- and micro- pores.
  • the porous solid may have at least 10% of its void volume in the form of micropores with diameters less than 2 nm.
  • the porous solid has at least 5% of its void volume in the form of mesopores with diameters less than 50 nm.
  • the porous solid is selected to be capable of reducing the pressure of the working fluid vapour or gas in contact with it, i.e. it adsorbs the working fluid.
  • the adsorption process must be reversible, e.g. it must be possible to desorb the working fluid by reducing its pressure or by raising the temperature of the porous solid.
  • the porous solid must be capable of adsorbing the working fluid gas above its critical temperature.
  • a wide range of porous materials may be employed.
  • Silica may be used, for example fumed silica, granular silica or aerogel silica, including granular, monolith and flexible blanket aerogels.
  • Natural or artificial glasses, ceramics or molecular sieves may be used.
  • Carbons which may be used include activated granules or monoliths, aerogels or membranes. Examples of porous carbons suitable for this invention are described in PCT/GB 01/04222.
  • a range of organic materials including resorcinol-formaldehyde foams or aerogels, polyurethane, polystyrene or other polymers including foamed or aerogel polymers may be used.
  • Polymers of intrinsic porosity in which the tailored pore sizes are created by the three-dimensional linking of appropriate pre-cursor molecules with constrained geometries are also suitable for this invention.
  • a range of composites, including silica-carbon composites may be employed.
  • Mixtures of porous materials may be employed.
  • Porous materials which can be used can be manufactured by a variety of known processes. These include, but are not limited to, polymeric foam blowing, sol-gel polymerisation, pyrolysis, thermolysis and direct chemical synthesis. Porous adsorbents which may be used include silica gel, molecular sieves, and aerogels, both organic and inorganic. Organic materials may be pyrolysed in the presence of controlled amounts of oxygen to generate micro-porous adsorbents. Coconut and coal, for example, may be pyrolysed to produce activated carbons. Polymer aerogels may be pyrolysed to produce carbon aerogels. Hydrocarbons may be pyrolysed to produce carbon membranes. Carbon black may be pyrolysed by plasma processes.
  • Carbon based materials such as activated carbons derived from biomass precursors, e.g. coconut shell or cellulose, are especially preferred since they are obtained from sustainable resources, require minimal energy input in their manufacture and effectively sequester atmospheric carbon dioxide as carbon within heat pump devices.
  • biomass precursors e.g. coconut shell or cellulose
  • carbon adsorbents can be removed recovered and burnt recovering their energy content, originally captured when the biomass was formed, returning the carbon dioxide to the atmosphere. Since the gas originated from this source the combustion is CO 2 -neutral.
  • the carbon adsorbent would be buried in landfill, in the subduction zones at boundaries of tectonic plates, or recycled to new equipment thus ensuring that the carbon is permanently removed from the atmosphere.
  • Inorganic microporous solids which may be used can be generated by thermolysis.
  • fumed silica can be produced from silicon tetrachloride using an oxy-hydrogen flame or by a plasma process.
  • Organic-inorganic precursors may be processed by thermolysis to produce molecular sieves.
  • Natural mineral hydrates may be thermalised, for example vermiculite and perlite.
  • a particular gas or mixture is used with a selected porous solid such as: carbon (e.g. graphite, activated carbon, charcoal, aerogel), silica (fumed, aerogel, alkylated aerogel), alumina, alumino-silicates (molecular sieves), and organic polymers (e.g. polystyrene, polyurethane, polyacrylate, polymethacrylate, polyamines, polyamides, polyimides, and celluloses).
  • CFCs and the HCFCs continue to be manufactured and used in the developing world their phase-out under the Montreal Protocol is already taking place. In territories when continued use of these chlorinated fluids is permitted then they might be used in combination with activated carbon, silica, or an organic polymer.
  • SO 2 and HFCs can be used with carbon, silica, alumina or an organic polymer, especially those with basic atoms such as O and N or acidic H atoms.
  • SO 2 may not be preferred because of its toxicity.
  • Hydrocarbons can be coupled with carbon, alkylated silica or an organic polymer, especially a hydrocarbon polymer such as polystyrene. Hydrocarbons are more preferred than halogenated fluids and SO 2 .
  • hydrocarbons are restricted to applications where the appropriate precautions can be taken against the flammability hazard, for example in large industrial applications or low-inventory, hermetically-sealed systems such as domestic refrigerators.
  • a further disadvantage is that the enthalpy changes associated with the sorption/desorption of hydrocarbons is less than for more polar gases, including CO 2 , SO 2 and NH 3 . In some territories hydrocarbons are not preferred because any leak to the atmosphere and exposure to sunlight may generate photo-chemical smog.
  • Hydrogen is readily adsorbed on and desorbed from various metal alloys, notably those containing nickel. Hydrogen is preferred to hydrocarbons because it will interact more strongly with metals than hydrocarbons with the sorbents listed above. Hydrogen can also be used with micro-porous organic materials such as carbon nanotubes, designed to store the gas for power generating applications such as fuel cells. Like hydrocarbons hydrogen reacts with atmospheric hydroxy 1 radicals that play a key role in removing naturally-emitted hydrocarbons as well as man-made pollutants such as HFCs. Increased hydrogen emissions can thus indirectly increase global warming.
  • Ammonia can be used with carbon, silica or with an organic polymer. It is suitable for applications where toxicity and flammability can be controlled, for example in large commercial and industrial applications or low inventory, hermetically sealed domestic applications.
  • the most preferred fluid is carbon dioxide.
  • carbon dioxide derived from fossil fuel is the single largest contributor to global warming the quantities required for this invention are small.
  • a natural source such as biomass fermentation
  • any gas emitted from the device has a zero contribution to global warming.
  • Carbon dioxide has low toxicity, is non-flammable and is readily adsorbed by a variety of porous solids including carbon, silica and organic polymers, especially those containing basic atoms such as O and particularly N.
  • the ability of porous solids to adsorb CO 2 can be enhanced by impregnating the solids with compounds containing groups capable interacting with the fluid. Nitrogen and oxygen containing substances can be employed. Amines, amides alcohols, esters and ketones are preferred.
  • amines More preferred are amines, amides, and urethanes with high boiling points, preferably above 100 0 C.
  • a particularly preferred substance is poly-ethyleneimine.
  • the temperature changes generated when the fluid reversibly adsorbs and desorbs should be greater than 5 0 C and more preferably greater than 10 0 C.
  • IHA integrated heat of adsorption
  • HCA heat capacity of the adsorbent
  • the integrated heat of adsorption is a function the interaction of the fluid with the porous solid and is defined as the total heat generated when the fluid adsorbs onto the solid as its pressure is raised from a lower pressure to a higher pressure.
  • IHA should be at least 50 kJ/kg and more preferably greater than 100 kJ/kg. Most preferably the IHA should be comparable with the latent heats of condensation of existing refrigerants.
  • a maximum working pressure below approximately 2 bar range at the heat rejection temperature is preferred. This keeps the pressure at any point in the device below the pressure at which pressure regulations apply. This allows the device to be manufactured more cheaply.
  • Use of a high volume throughput compressor such as a centrifugal compressor is preferred. Such a compressor is especially suitable for large water chillers for example as employed for air conditioning public buildings.
  • An IHA which reduces the fluid pressure over the adsorbent significantly below 2 bar is not preferred since it increases the size of the components, notably the compressor, without any economic advantage.
  • the IHA is preferably chosen so that the pressure of the adsorbent at the lowest working pressure of the device is not less than approximately 1 bar. This serves to prevent the ingress of atmospheric gases which are not significantly adsorbed by the porous solid. In applications where water ingress is not a concern or equipment is designed to prevent it and where the IHA increases disproportionately as the gas pressure falls then pressures below 1 bar can be advantageously used.
  • a special advantage of the present invention is that it allows even relatively small temperature changes below 5 0 C induced by fluid adsorption and desorption to generate the required substantial temperature differences between the ends of the adsorbent tubes, for example typically 10 0 C to 45 0 C in air conditioning applications. Despite this advantage larger temperature changes facilitate heat exchange between the bed and the external heat transfer fluid.
  • changes on adsorption and desorption are greater than 5 0 C and more preferably greater than 10 0 C.
  • HCA adsorbent heat capacities
  • a group of adsorbents may have similar IHA their adsorption capacities (CA) for a working fluid will depend upon the numbers of active sites available per unit mass.
  • the number of active sites tends to be related to the internal surface area (ISA) of the porous solid accessible to the fluid molecules, thus the higher ISA the greater the capacity of the solid per unit mass to adsorb the fluid at a given pressure.
  • ISAs of at least 1000 m 3 /g are most preferred.
  • the temperature changes will be essentially independent of their densities (DA).
  • the temperature changes also depend upon the heat capacities of the materials from which the adsorbent tube is manufactured. The quantities of these materials can be minimised by selecting materials with high densities provided this does not affect the other physical properties indicated.
  • the quantity of the heat exchange fluid which removes heat from and adds heat to the adsorbent tube can also determine the temperature changes. Low inventories and high flow rates of the heat exchange fluid are preferred.
  • the thermal conductivity of the adsorbent is the thermal conductivity of the adsorbent.
  • the device can be constructed to overcome this constraint.
  • the device includes adsorbent tubes long in comparison to their width or diameter and progressively removing/adding heat starting at one end.
  • the ratio of tube length to diameter is greater than about 4:1, more preferably greater than about 10:1 and most preferably greater than about 20:1.
  • bodies of the adsorbents can advantageously be constructed incorporating heat conducting materials to provide adsorbent composites.
  • These materials may include graphite, preferably as flakes, fibres or foams; metal mesh, powder, wire or fibres, preferably comprising a high thermal conductivity metal such as copper and aluminium; organic polymers with high thermal conductivities, such as polyaniline and poly- pyrrolidine.
  • Such polymers generally have good electrical conductivities.
  • the thermally conducting polymers containing basic nitrogen atoms and comprising at least a proportion of the porous solid also contribute to the adsorption of carbon dioxide. Compressing the porous solids into monoliths also improves thermal conductivity.
  • Table 1 lists examples of various adsorbents and their thermal conductivities which demonstrates that the addition of a heat conducting additive substantially improves the thermal conductivity of an adsorbent.
  • Monolithic carbon + aluminium laminate 20 Preferred adsorbents or adsorbent composites have thermal conductivities greater than about 0.5 W/(m.K), more preferably greater than about 5 W/(m.K) and most preferably greater than about 50 W/(m.K).
  • the configuration of the adsorbent heat exchanger is selected to determine the ease with which heat is transferred to and from the porous solid. An important requirement is to maximise heat exchange without unacceptably increasing the thermal capacity of the heat exchanger to such an extent that temperature changes fall below the preferred value of 5 0 C.
  • the adsorption heat exchanger bed may have a cylindrical or tubular configuration and is arranged with a long axis either parallel to or perpendicular to the flow of the external heat transfer fluid.
  • the bed includes one or more ducts and wherein the heat transfer fluid flows through the ducts.
  • the bed has an outside wall and heat transfer fluid passes over the outside wall of the bed.
  • the bed has both internal ducts and outside walls and the heat transfer fluid passes both through the internal ducts and over the outside walls.
  • the adsorbent may be contained in a multiplicity of absorber tubes within a single duct, the duct having a circular, square, hexagonal or any other cross-section that is appropriate for a specific application.
  • a flat plate adsorbent bed heat exchanger is used, the adsorbent material being held between two flat metal plates. Heat is removed from or supplied to the adsorbent by circulating heat transfer fluid on the external surfaces of the plates.
  • the heat exchangers can be constructed from multiple parallel or series adsorbent beds.
  • a bed may comprise a conduit containing an array of tubes wherein the heat transfer fluid passes in contact with the tubes heat being transferred between the working fluid, adsorbent and heat transfer fluid through the outer surface of the tubes.
  • the tubes may be arranged in parallel spaced relation.
  • the tubes are preferably connected in parallel to the working fluid circuit.
  • the pressure at each point in a single tube is preferably substantially the same at each instant of the cycle. Small pressure differences are required to produce a flow of CO 2 but these differences are small in comparison to the actual pressure of CO 2 over the adsorbent.
  • the pressure drop along a single bed is low.
  • This may be achieved by use of a granular adsorbent or more preferably a monolithic adsorbent with one or more channels therein, the absorbent contacting the inner wall of the tube to ensure good heat transfer to and from the wall.
  • a thermally conducting medium eg a thermally conducting paste may be used between the wall and adsorbent monolith.
  • a tube may contain several monoliths.
  • the multi tube array usually has a temperature gradient from the transfer medium inlet to outlet.
  • the multi tube adsorbent bed has a permanent temperature profile in use.
  • the external surfaces of the adsorbent heat exchangers which are in contact with the heat transfer fluid in use are preferably fitted with fins to enhance heat transfer.
  • the fins can be held mechanically in contact with the heat exchanger surface.
  • the fins are soldered, glued, braised or welded to the surface of the heat exchanger to maximise heat transfer.
  • the fin design adopted may depend upon the direction of the flow of the heat transfer fluid relative to the long axis, or axes, of the adsorbent bed. Where this flow is parallel to a long axis longitudinal fins are preferred either in the form of simple strips or as spirals. Where the flow is perpendicular to a long axis then the transverse fins are preferred for example in the form of discs, strips or plates.
  • An especially preferred form of fin is a wire loop, which can be used with both longitudinal and transverse heat transfer fluid flows.
  • Heat transfer from the adsorbent to the walls of the internal wall of the adsorbent containing tube may include perforated metal plates or discs of metal mesh or fibre preferably arranged perpendicular to the tube axis. For optimum heat transfer these may be in tight contact with the walls of the containing tube.
  • the adsorption bed heat exchanger contains an internal folded wire heat exchanger. This serves to enhance heat conduction from the adsorbent bed to walls of the bed.
  • the wire is located in contact with the walls of the bed at a large number of points. More preferably the wire is soldered, brazed or welded to the walls at the contact points.
  • the wire is preferably a high conductivity metal such as copper or aluminium.
  • one or more tubes are provided with the adsorbent tube, arranged so that the heat transfer liquid flows through the one or more tubes within the absorption tube.
  • Heat transfer between the adsorbent and the tube containing the heat transfer fluid may be enhanced by fins which are perpendicular to the axis of the tube.
  • the fins fit tightly or are attached to the outer surface of the heat transfer fluid tube but are not in contact with the inner surface of the adsorbent tube to prevent adventitious heat loss or gain by the adsorbent.
  • the adsorbent tube is also internally or externally thermally insulated with a layer of insulating material, for example by a polymer foam.
  • a preferred form of insulation is a closed-cell foam disposed around the adsorption tube.
  • a vacuum jacket may be provided in which molecular mean free path is less than the distance across the jacket. Aerogel containing insulation is especially preferred.
  • the inner wall of the adsorbent tube or other container may be provided with a low thermal conductivity liner or sleeve or coating which inhibits the flow of heat from the adsorbent to the wall of the adsorbent tube or container.
  • a low thermal conductivity liner can also serve as container for the adsorbent and any heat transfer liquid tubing allowing them to be assembled prior to insertion in the adsorbent tube.
  • a further advantage of this design is that adsorbent tube, which is not required for heat transfer, can be fabricated from materials such as mild or stainless steels which are inherently stronger than copper or aluminium.
  • the tube wall thickness selected which can thus be chosen to resist high pressure. This is especially advantageous when a multiplicity of heat transfer liquid pipes is employed.
  • the liner is preferably fabricated from a low thermal conductivity organic polymer, e.g. polyolefin. More preferred is an open cell organic foam, such as polyurethane foam. Especially preferred is an organic foam reinforced externally with a solid polymer tube to provide mechanical strength.
  • the tube carrying the heat transfer liquid is preferably fabricated from a metal to facilitate heat transfer.
  • the tube is made from a high thermal conductivity metal such as copper of aluminium.
  • a further advantage is that the tube is exposed to an external pressure of gas rather than an internal pressure. In this mode copper and aluminium, which are less mechanically strong than steel, are acceptable.
  • the adsorption tube is fabricated in the form of a spiral and contained within the annulus of two concentric tubes that form the liquid duct.
  • This configuration has the special advantage than it allows a long effective length of adsorption bed to be contained within much shorter actual length.
  • the duct walls fit closely to the adsorption tube so that heat transfer liquid is constrained to flow through the spiral passageways formed between the outer and inner duct walls. This configuration minimises the quantity of heat transfer liquid in the heat exchanger and thus assists in keeping the temperature changes as large as possible.
  • the water duct can be advantageously insulated, for example with a layer of polystyrene, polyurethane foam or glass fibre.
  • the heat transfer fluid is a gas, especially air.
  • Such devices are especially advantageous for heat pumping in microgravity locations because they do not contain any liquid, such as the refrigerant and oil found in conventional units, which requires gravity to ensure it flows properly between components.
  • the heat transfer fluid is a liquid.
  • a suitable heat transfer liquid requires a combination of properties which are determined by its intended application. Liquids should have low viscosities so that pumping energy is minimised. Preferably liquids should have dynamic viscosities less than 0.025 Pa-s, preferably less than 0.01 Pa-s, and most preferably less than 0.001 Pa-s.
  • the liquid circulation system is suitably pressurized liquids with a range of boiling points can be used. Preferably for operating convenience the liquid should have a normal boiling point greater than highest temperature reached by the adsorbent. The liquid must not freeze below the lowest temperature generated within the device.
  • the liquid has a flash point greater than 100 0 C, more preferably greater than 130 0 C and even more preferably greater than 200 0 C.
  • the liquid should be non-flammable.
  • Preferred liquids include those already known to the industry as secondary refrigerants. These materials include water, brine, glycols, alcohols, hydrocarbon oils, silicone oils, and halogenated compounds including partially fluorinated ethers, perfluorinated ethers and chlorinated liquids. Where they are mutually compatible these liquids may also be used in mixtures.
  • compositions with a wide liquid range are required, while retaining the desirable properties of flash points greater than 100 0 C and normal boiling points greater than the highest operating temperature.
  • Preferred substances include esters and ethers containing 3 or more carbon atoms. These can be acyclic or cyclic.
  • Preferred substances include, but are not limited to, glycol- or polyol- cyclic carbonates and cyclic ethers. Especially preferred are propylene carbonate, ethylene carbonate and dimethylisosorbide. Blends comprising esters, ethers, glycols with each other and with water can also be used.
  • the liquids may optionally contain additives which enhance one or more desirable composition properties such lower freezing points, higher boiling point, lower viscosity or higher flash point. Such additives preferably constitute less than 50% of composition by mass.
  • compositions containing fluorine or chlorinated substances should preferably have very low vapour pressures or incorporate reactive groups such as double or triple bonds that facilitate their rapid destruction by reactive species in troposphere.
  • the heat is removed from the adsorption bed heat exchanger by a heat transfer fluid which undergoes a change of state from liquid to vapour.
  • heat is supplied to the adsorption bed by a heat transfer fluid which undergoes condensation.
  • heat is transferred to or from the adsorption bed heat exchanger by a combination of a gaseous heat transfer fluid and a liquid heat transfer fluid.
  • Metal adsorbents which can be used with hydrogen are especially advantageous because they have much higher thermal conductivities than non-metallic materials such as carbon, zeolites and silica gel.
  • a fluid/adsorbent combination depends upon a number of factors whose values may be selected to provide an optimum performance for a given application and the design of the adsorbent heat exchangers.
  • An important aspect of this invention is that the adsorption/desorption process is driven by a compressor.
  • Any compressor may be used including a reciprocating piston, rotary, sliding vane, diaphragm type, screw, scroll, Periflow (trade mark) or centrifugal.
  • many compressor designs have sliding surfaces in the displacement volume are lubricated by a liquid lubricant and generate oil droplets which are discharged with the compressed gas.
  • Such compressors whose will require oil separators between the compressor and the adsorption bed to prevent oil in fine droplet form fouling the bed. Oil-free compressors are therefore preferred, i.e. compressors whose sliding surfaces are not lubricated in the displacement volume by a liquid lubricant.
  • diaphragm compressors which operate nearer to isothermal than isentropic conditions because of the effective cooling of the working fluid through the large surface area of the diaphragm and the compressor head augmented in some units by the cooling of the circulating hydraulic oil that drives the diaphragm.
  • Diaphragm compressor energy efficiencies can be superior to those of reciprocating compressors. Refrigerant leakage rate is much lower because an excellent seal can be established between the diaphragm and compressor case, while an oil-free reciprocating compressor lacks the excellent sealing properties of the oil film of a conventional reciprocating unit.
  • diaphragm compressors For low duty applications, such as domestic refrigerators and room air conditioning units, diaphragm compressors have the advantage over conventional oil-filled hermetic reciprocating and rotary units in the providing a combination of an excellent gas seal with an external electrical motor.
  • the heat generated by the latter can be dissipated by a simple cooling fan.
  • motor cooling is partly provided by the oil, which transfers heat to the casing, and the refrigerant, which transfers heat to the condenser.
  • linear compressors such as those developed by Sunpower and LG Industries in which a piston containing a permanent magnet is driven fixed electromagnet.
  • Suitable LG models are the DFL and FA linear compressor ranges.
  • Adsorption heat pumping requires the refrigerant and heat transfer fluid flows to be periodically swung between beds.
  • the switching of the flows can be actuated by a timer, pressure sensors which generate a signal when the pressure difference between the beds has reached a selected value, or by temperature sensors located either in the beds or in contact with the heat transfer fluid streams exiting the adsorption bed heat exchangers.
  • the switching can be initiated by a combination of these inputs.
  • Cooling is produced by desorption of working fluid from the adsorbent by reducing the pressure of the gas in contact with the adsorbent. Pressure induced adsorption of the working fluid produces heating.
  • Preferred working fluid/adsorbent solid combinations are selected such that the heats of adsorption and desorption are substantially greater than the heat of compression.
  • the heats of adsorption and desorption are similar or equal to the latent heats of vaporisation of CFC, HCFC, HFC, hydrocarbon and ammonia working fluids presently used for any conventional Rankine Cycle based devices which they may be intended to replace.
  • Filters can advantageously be positioned in the pipes carrying gas to and from the beds to prevent adsorbent powder fouling other components in the system.
  • Suitable valves for this invention include solenoid activated valves which are well- known to air conditioning and refrigeration engineers.
  • Rotary valves driven for example by electric motors, can also be used.
  • Pneumatically actuated valves can be used. These can be operated by a compressed air supply.
  • solenoid valves responding to pressure or temperature sensors or to a timer, send pulses, of gas to the pneumatic actuators thus causing them to change the positions of valves.
  • the device operates as an air-to- air air conditioning unit in which any water condensate formed by the air passing through the cold adsorption bed heat exchanger being cooled below its dew point is retained within the heat exchanger.
  • any water condensate formed by the air passing through the cold adsorption bed heat exchanger being cooled below its dew point is retained within the heat exchanger.
  • the cycle swings so that this bed becomes hot the condensate is evaporated and leaves the heat exchanger as water vapour in the air stream.
  • Current air-to-air a/c units where the hot and cold heat exchangers do not interchange their functions during the cycle condense water on the outer surface the cold evaporator. This has significant disadvantages. Since water has a very high latent heat of evaporation water condensation takes up a significant fraction of the cooling power of a conventional a/c unit since the condensate rejected to a suitable drain.
  • condensate water generated the cooling is re-evaporated when the bed is hot. This allows the bed to operate at a lower temperature during the evaporation period and improves energy efficiency.
  • the need to drain the condensate places limitations on the citing of the evaporator and may also require the installation of a condensate collection tank and pump.
  • the adsorption heat pump comprises the upper stage of a two stage refrigeration unit where the lower temperature stage may be a conventional Rankine cycle unit using any condensable refrigerant.
  • This can be a fluorine containing fluid such as a hydrofluorocarbon, unsaturated fluorocarbon or a hydrocarbon.
  • the refrigerant is CO 2 which has low toxicity, low flammability and low environmental impact in this application.
  • the adsorption beds in directly cool the condenser of the lower stage.
  • the adsorption beds cool a heat transfer liquid, for example water, brine or glycol, which in turn cools the condenser.
  • a device comprises two adsorption beds which allow carbon dioxide to be liquified and subsequently evaporated in a separate heat exchanger at low temperature to produce refrigeration.
  • the refrigerant gas can enter and exit the adsorption bed at same end depending upon whether the adsorption or desorption is occurring.
  • the working fluid enters at one end and exits at the other. This ensures that the adsorbent is always pushed by the gas pressure in the same direction and this helps to minimise attrition of the adsorbent granules generating fine powder which could escape from the bed and damage other components.
  • Figure 1 are heated and cooled by water flowing in a closed circuit.
  • Figure 11 comprising: two 4-way, powered valves 11.1 and 11.2; two heat exchangers 11.3 and 11.4; a pump 11.5; optionally two water storage buffer tanks 11.6 and 11.7; two fans to drive, or suck, air over 11.3 and 11.4; and two adsorption beds 1.2 and 1.3 corresponding to the beds in Figure 1.
  • Each valve may be switched between two positions so that the water flows through 11.3 and 11.4 are always in the same direction, but water flows through the adsorption beds 1 and 2 reverse direction depending whether they are hot or cold, as determined by the CO 2 circuit.
  • the water and CO 2 circuits are essentially operated in phase with each other.
  • the water flow is driven by a pump 11.5.
  • the pump can be positioned at a convenient location in the circuit where the water flow is uni-directional.
  • the pump is placed just before the hot heat exchanger 11.4 or just after the cold heat exchanger 11.3 (as shown) to minimize the effect of any heat from the pump motor adversely affecting the energy efficiency and the capacity of the device.
  • the pump is placed just before the hot heat exchanger 11.4.
  • Either or both of the buffer tanks for cold and hot water 11.6 and 11.7 may be placed in the circuit immediately before the heat exchangers as shown. If the device is used to provide cool air to a room the buffer tank 11.6 smoothes any temperature fluctuations during the CO 2 pressure equalization. Tank 11.7 plays an analogous role if the device is being used to heat a room.
  • the buffer tank 11.6 is sufficiently large in capacity to provide cooling during daytime for at least one hour or longer without the device operating. This is advantageous because it allows the device to cool the water in 11.6 overnight, rejecting heat to the environment when the external temperature is lower, thus providing better energy efficiency.
  • This embodiment also allows air conditioning during peak demand without consuming power apart from the modest amount required for the pump and the fans. This embodiment therefore reduces power during peak air conditioning times, such as summer afternoons when the electricity supply grid can be overload causing "brown-outs".
  • valves 11.1 and 11.2 are operated simultaneously by actuators so that their positions change from those shown in Figure
  • Figures 9e and 9f indicate the changes in the valve settings associated with the second pressure equalization in the cycle which again swaps the direction of the water flows through the adsorption beds.
  • Figures 1Oe and 1Of indicate the positions of during the stage of the cycle where CO 2 is being pumped from 1.3 to 1.2.
  • FIG. 12 Another embodiment is shown in Figure 12. This comprises a compressor 12.1, two adsorption bed heat exchangers, 12.2 and 12.3, a heat exchanger 12.4 to remove the heat of compression from the refrigerant, and six 2-way valves, 12.5 to 12.10.
  • This system operates on a similar cycle to that described for the system shown in Figure 1 but employs a different valve system, and can be used with an air system such as that shown in Figure 2 or a water circuit such as that shown in Figure 11.
  • the adsorption beds 12.2 and 12.3 are charged with carbon adsorbent and the unit is charged with the maximum amount of CO 2 without exceeding the maximum pressure rating of the equipment.
  • the copper wire fins (not shown) are soldered to both outside and inside walls of the ducts.
  • Figure 12 shows the valve settings during the various stages of the cycle. A black valve indicates that it is closed while a white valve indicates that it is open.
  • Figure 12a shows the valve settings for equalisation the pressure between the two beds and is the same whichever bed is at a high pressure with the other at a low pressure and with CO 2 gas passing either way through valve 12.9. During pressure equalisation the compressor is in bypass mode with compressed gas being allowed to pass immediately back to suction.
  • Figure 12b shows gas being sucked from bed 12.3, which is cold due to adsorption, and compressed onto bed 12.2, which is hot due to adsorption.
  • Figure 12c is analogous to Figure 12b showing gas being sucked from bed 12.3 and compressed onto bed 12.3.
  • the compressor should be operated in bypass mode for as short a time as possible when it is not contributing to the cycle.
  • To achieve this valve 12.9 is preferably of greater bore than others in the circuit to ensure that it does not inhibit the gas flow. After the initial pressure drop, gas flow between the beds is determined by the rate of flow between the granules and by the rate of desorption/adsorption from/to the granules.
  • the compressor can be switched back into the circuit significantly before the equilibrium concentrations of CO 2 on the two beds is achieved. In this way the compressor is usefully contributing to cycle.
  • the pressure equalisation stage overlaps with the gas pumping stage.
  • a further advantage of re-starting gas pumping before equilibrium has been reached is that the cooling can be essentially continuous. However some temperature variations may be observed in the heat transfer fluid, air or liquid. In a further embodiment of this invention these fluctuations may be smoothed fitting a "coolth" sink.
  • a "coolth" sink An example is shown in Figure 2, situated where coolth sink 2.6 is situated in the cold air flow 2.10.
  • suitable heat sinks are metal grids and metal tubes containing water.
  • the heat sink is preferably with fitted with fins to enhance heat transfer.
  • the coolth sink in a unit with a water circuit may be a cold water tank such as 11.7 as shown in Figure 11.
  • a second gas which is essentially not adsorbed, is mixed the CO 2 which assists in sweeping the CO 2 from one bed to the other.
  • the gas is selected so that amount adsorbed onto the beds is much less than the CO 2 .
  • Gases with boiling points significantly lower than CO 2 are preferred, for example N 2 , H 2 and the noble gases, such as He, Ne, and Ar.
  • the device, shown in Figure 13 contains He which both helps to sweep the CO 2 from one bed to the other and because of its high thermal conductivity improves the heat transfer to and from the beds.
  • the application of this embodiment to a room air conditioner shown in Figure 13 comprises: a compressor 13.1; adsorbent beds 13.2 and 13.3 containing activated carbon adsorbent and fitted with internal wire fins to enhance heat transfer; heat exchanger 13.4 to remove heat of compression; 4-way valves 13.5 and 13.6 to enable CO 2 to be alternately sucked from one bed and compressed onto the other; expansion valve or capillary 13.7; valve 13.8 to allow the pressure over the beds to be essentially equalised at the appropriate part of the cycle; expansion valve 6 which allows mainly He gas to pass either way between the beds; and an air or liquid transfer system to add or remove heat from the adsorbent beds, for example as shown in Figures 2 and 11.
  • the operation of the device is based on the method described in relation to Figure 6 and is similar to other adsorption devices described previously in this specification but with the additional feature that the inert gas He gas moves the CO 2 along the beds.
  • the device operates according the following sequence of operations starting at the point in the thermodynamic cycle where bed 13.3 is essentially at its temperature of the external air (35 0 C) and bed 13.2 is essentially at the temperature of the stale air being vented from the air conditioned room (22 0 C). The major part of the CO 2 charge in the unit is adsorbed on 13.2 and the remainder on 13.2.
  • Second Pressure Equalisation Once the temperature of the air leaving bed 13.2 starts rising and the temperature of the air leaving bed 13.3 starts falling the pressure difference between the bed is equalised by opening valve 13.8 as shown in Figure 13c. With the valves set in the positions shown in Figure 13a gas flows from 13.3 to 13.2, bypassing the compressor 13.1. CO 2 desorbing from 13.3 cools the bed to 10 0 C, while 13.2 is heated by CO 2 adsorption to 40 0 C.
  • Second Gas Pumping When temperature difference has been achieved between 13.3 and 13.2 has dropped to an appropriate level valve 13.8 is closed as shown in Figure 13d so the compressor starts pumping a mixture of He and CO 2 from 13.3 to 13.2. In this mode the CO 2 is preferentially stripped by adsorption from the mixture as it enters 13.2. He gas, depleted of CO 2 flows through bed 13.2 and passes via valve 13.6 to the expansion device 13.7 where its pressure drops to that of bed 13.3. The low pressure He sweeps through bed 13.2 where it mixes with desorbing CO 2 which it carries, via valve 13.6, to the compressor.
  • Figure 14 shows an example of the gas circuit for a four-bed design using a CO 2 and activated carbon gas/adsorbent combination.
  • the unit also comprises a compressor (14.1), heat exchanger (14.10) to remove the heat of compression, four three-way valves (14.6 to 14.9) and connecting pipe 14.11.
  • the four three-way valves are connected such that the compressor 14.1 sucks gas from Bed 14.2, and compresses it onto Bed 14.4. Simultaneously, gas flows from Bed 14.3, which is initially at high pressure, to Bed 14.5, which is initially at low pressure, via connecting pipe 14.11.
  • Beds 14.2 to 14.5 are alternately heated and cooled by water flowing in the circuit shown in Figure 15.
  • the circuit comprises a pump 14.16; two heat exchangers 14.12 and 14.13; and two valves for periodically reversing the water flow in phase with the switching of CO 2 flow.
  • the valves 14.6 to 14.9 and 14.14 to 14.15 can be solenoid-, motor- or pneumatically- driven and are controlled by a micro-processor or electro-mechanical system with similar functionality. Other methods of reversing the water flow may be employed in place of 14.14 and 14.15; for example a pump capable of pumping in either direction. Alternatively they might be replaced by a single 4-way valve.
  • the operating cycle can be described starting from the initial condition summarised in the Table 2. This represents the unit condition just after the valves have switched at the end of the previous stage.
  • the temperatures and the relative pressures are indicative and may vary according to the conditions and the design details of the equipment.
  • the valves are set to the positions as shown in Figure 14a and 14b.
  • the compressor sucks CO 2 from bed 14.2 which cools as a result of gas desorption cooling the water to 5 0 C.
  • the cold water enters heat exchanger 14.12 where it cools room and its temperature rises to 15 0 C.
  • the block arrow associated with 14.12 indicates the flow of heat from the room air into the heat exchanger.
  • the gas is compressed it onto the bed 14.4 where it is adsorbed raising the temperature of the water to 45 0 C. 4.
  • the water enters heat exchanger 14. 13 where it rejects heat to the atmosphere and is cooled to 35 0 C.
  • valves When this condition is reached as detected by sensors monitoring pressure and temperature, or after set time interval the valves are switched to the positions shown in Figures 14c and 14d.
  • the compressor sucks CO 2 from bed 14.5 which cools as a result of gas desorption and thus cooling the water to 5 0 C.
  • the cold water enters heat exchanger 14.12 where it cools the room and its temperature rises to 15 0 C.
  • the gas is compressed it onto the bed 14.3 where it is adsorbed raising the temperature of the water to 45 0 C. 4.
  • the hot water enters heat exchanger 14.13 where it is cooled to 35 0 C.
  • the pressure equalisation stage of the cycle operates simultaneously with the suction/compression stage with the system arranged so that beds undergoing also equalisation contribute to the heat/cooling of the water stream.
  • the compressor is either idling on "open" circuit or is temporally switched off and then back on when compression is required. In either case energy is consumed without delivering a useful heat pumping effect.
  • the arrangement indicated in Figure 14 allows the compressor to operate continuously providing heat pumping throughout the cycle.
  • the four bed system has described above uses water as an intermediary heat transfer fluid and in air conditioning industry terminology can be described as a chiller.
  • the system can be readily designed with air as the heat transfer fluid. If the primary use of the system is heat, rather than cool, a room then it can be described as a heat pump.
  • a bypass valve may be provided in parallel with the compressor, e.g. between the valves 14.6 and 14.8, allowing for dual modes of operation in accordance with the first and second aspects of this invention.
  • the valves 14.9 and 14.7 may be arranged so that direct flow between the valves 14.9 and 14.7 is prevented.
  • a controllable flow rate valve e.g. a needle valve, may be located between the valves 14.9 and 14.7. In this way flow between the valves 14.9 and 14.7 may be turned on and off or may be regulated.
  • a further embodiment of this invention incorporates six adsorption beds as shown in Figure 15.
  • the system comprises a compressor 15.1; a heat exchanger 15.2 to remove the heat of compression; six adsorption beds 15.3 to 15.8; and six three-way valves 15.9 to 15.14 controlling the gas flow direction between the beds.
  • the system further comprises an air or water circuit for transferring heat to and from the adsorption beds.
  • Figure 15 shows a water circuit comprising heat exchangers 15.16 to 15.18 and 15.20 to 15.22 in contact with the adsorption beds.
  • Heat exchanger 15.15 removes heat from the room or space being air conditioned.
  • Heat exchanger 15.19 rejects heat the environment.
  • Pump 15.25 serves to circulate the water (or other heat transfer liquid such as a glycol).
  • Two three-way valves 15.23 and 15.24 enable the direction of the water flow through the water circuit to be reversed as required.
  • the device operates in a similar fashion to the 4-bed system shown in Figure 14 with the addition of a third pair of beds.
  • the advantage of this design is that enables smoother temperature profiles ("glides") along the sets of warm and cold beds thus improving energy efficiency.
  • the invention is further described by means of examples, but not in any limitative sense.
  • a diaphragm compressor 5 two 3 -way valves 6 and 7, which allow the two beds to be switched between adsorption and desorption; air flow inlets 16 and 19; air flow outlets 18 and 20; 4-way air switching valve 17; gas buffer vessel 21 to prevent over-pressurization; pressure gauge PIl to read the maximum pressure system pressure; pressure gauge PI2 to read compressor suction pressure; connecting lines 9, 10, 11, 12, 13, 14, and 15.
  • Each adsorbent bed comprised a central copper heat exchanger tube (internal diameter (OD) 16.7 mm, external diameter 19, and length 250 mm) fixed concentrically with a brass outer tube ( OD 57mm; ID 54 mm; length 220 mm) by two brass end caps soldered to the outer tube. Each bed was also fitted with pipes at each end to allow the CO 2 to enter and leave.
  • the heat exchanger area of the inner tube was extended by a spiral of 31 copper wire loops soldered to the outer-surface of the tube. The wire diameter was the 0.6 mm, and the diameter of the spiral winding was 44 mm. A further looped spiral copper wire was soldered inside the tube. This configuration provided an effective method for transferring heat to and from the air streams and the carbon adsorbent
  • the adsorbent was a standard, commercial 30-70 mesh activated carbon designed for CO 2 adsorption and supplied by Chemviron Carbon.
  • the two adsorbent beds 1, 2 were charged with carbon adsorbent, and purged with carbon dioxide to remove air.
  • valves 6 and 7 were Swagelok 0.25 inch 3-way stainless valves.
  • Compressor 5 was an oil-free KNF Neuberger N 035.2 ANE twin headed diaphragm compressor with the heads connected in series and capable of pumping gas at 30 standard litre/minute with a maximum operating pressure of 1 barg. Connecting lines mainly nylon tubing of diameter 0.25 inch. Short lengths of 0.25 inch stainless steel tubing were either side of the 20 micron filter 24 incorporated to prevent any dust from the adsorption beds entering the compressor.
  • Figure 16a shows Bed 1 in adsorptive mode (hot) while Figure 16b shows Bed 2 in adsorptive mode (hot).
  • the different positions of the air valve 17 position allows warm and cool air to always leave via exit 18 and exit 20 respectively, whichever bed was hot or cold thus providing the continuous supply of warmed air and cooled air.
  • the compressor 5 was switched on, with the three-way valves 6, 7 in the positions shown in Figure 16a. Carbon dioxide was drawn from bed 2 through line 8, valve 6, lines 9 and 10 into the compressor 5, and then through lines 11, 12, valve 7 and line 13 into bed 1. The carbon dioxide could not return into the system through line 14 which was closed by valve 6. Bed 2 was closed by valve 7 on line 15. Carbon dioxide was thus removed from bed 2, and pressurized onto bed 1. The heat generated by the exothermic adsorption of the gas in bed 1 was removed by the air flow 16, with the airflow valve 17 in the position shown, to exit 18. Similarly, the endothermic desorption of gas lowered the temperature of bed 2 cooling air flow 19 which left the rig by exit 20. The temperatures of the warm air stream at 18 and 20 were measured periodically with thermocouples.
  • Bed 1 was initially at higher pressure than bed 2 so that gas spontaneously flowed rapidly from 1 to 2 through the compressor.
  • the compressor started to suck gas from bed 1 and compressed it onto bed 2.
  • the temperature of bed 1 dropped as the result of CO 2 desorption, while the temperature of bed 2 increased because of gas adsorption.
  • test rig described in Example 1 was operated with the supply air temperature at
  • test rig described in Example 1 was operated with the supply air temperature at
  • test rig described in Example 1 was operated with the supply air temperature at
  • FIG. 19(a) shows a face view of the bed
  • Figure 19(b) shows a side view
  • Figure 19(c) shows a detail of the adsorbent in the bed.
  • Each absorption bed comprises two or more rows of tubes (19.1), with each row containing at least three tubes.
  • External fins (19.2) enhance the heat transfer to and from the external heat transfer fluid (eg water or air) flow (19.3).
  • a header pipe (19.4) connects all the pipes in a row allowing carbon dioxide to be fed simultaneously to each tube in a row.
  • a footer pipe (19.5) allows carbon dioxide to be removed simultaneously from each tube in a row.
  • Compression line (19.6) allows gas to be fed simultaneously to each header pipe.
  • Suction line (19.7) allows gas to be exhausted simultaneously from each footer pipe.
  • a valve (19.8) controls the entry of gas into the bed.
  • a valve (19.9) controls the removal of gas from the bed.
  • a micro- porous carbon adsorbent (19.13) is in thermal contact with the inner walls of the tubes. For clarity only a representative number of fins are shown.
  • valve (19.8) is open and (19.9) is closed so that CO 2 , represented by solid block arrow, is being compressed on to the bed.
  • the water flow represented by the solid block arrow (19.3) is removing heat from the bed generated by CO 2 adsorption on the microporous carbon. If valve (19.8) is closed and valve (19.9) is open then CO 2 will be sucked from the bed.
  • the dotted block arrow (19.11) represents the CO 2 direction and the dotted block arrow (19.12) represents the water flow which has been reversed.
  • FIG. 19(c) A preferred design for the adsorbent is shown in Figure 19(c).
  • This comprises a monolith (19.13) with one of more channels (19.14) parallel to the long axis of a tube to facilitate CO 2 flow (19.15) along the tube.
  • the tube containing the adsorbent (19.17) is selected to withstand a maximum working pressure of 20 bar gauge and is preferably a good conductor of heat. Aluminium and copper are especially preferred as the materials for (19.17).
  • the CO 2 flowing down these channels enters the adsorbent radially through pores.
  • a tube may contain several monoliths.
  • the especial advantage of this embodiment is that it allows the bed to operate with substantially the same pressure over the adsorbent at each point in the cycle, since the combination of the compression, suction, header footer and channels will ensure the pressure drop across the bed is low preferably less than about 0.25 bar.
  • the multi-tube adsorption bed shown in Figure 19 is incorporated in a heat pump having the 4-bed/2 array design shown in Figure 20. This provides an essentially continuous heat pumping effect.
  • the heat pump device shown in Figure 20 is a circulating water chiller which is cooling a room.
  • the device comprises four adsorption beds (20.1, 20.2, 20.3 and 20.4).
  • a water pump (20.9) circulates water through adsorption beds, (20.6) and (20.7) 3-way valves (20.10) and (20.11) allow the water flow through the adsorption beds to be periodically reversed; Valves (20.12, 20.13, 20.14, 20.15) control the direction of flow of CO 2 in the device.
  • Adjustable needle valve (20.16) controls the CO 2 flow rate between pairs of beds. Associated pipe work in the water and gas circuits are also shown.
  • the block arrow (20.17) represents the removal of heat from (20.7) by (20.6); Block arrow (20.18) represents the rejection of heat to the external atmosphere by (20.8).
  • the pipes shown as solid lines represent the CO 2 circuit; the pipes shown as dotted lines represent the water circuit.
  • each multi- tube absorption bed will have a permanent temperature profile imposed on it which will always be in the same direction.
  • the operation of the device is shown in Figure 21 in which the beds are represented by simple rectangles on which hare superimposed the temperature profiles during various stages in the cycle.
  • the numbering of the components in Figure 21 correspond to their equivalents in Figure 20.
  • the full stepped line within the adsorption bed rectangles represent the temperature profile at the beginning and end of each stage.
  • the dotted stepped line represents the extreme change in the temperature profile during the stage.
  • the doubled headed arrows indicate that the temperature moves between the two sets of stepped lines during each stage of the cycle.
  • valves controlling the water and CO 2 flows are set in the positions shown.
  • the direction of the water flow is indicated by the dotted arrows while the CO 2 flow direction is shown by the simple line arrows.
  • Compressor (21.5) pumps CO 2 from bed (21.1) to bed (21.4). Initially the two beds are at the same pressure Pl .
  • Beds (21.2) and (21.3) are initially at pressures P3 and P2 respectively causing CO 2 to flow through the control valve (21.16) desorbing from (21.2) and adsorbing on (21.3) valve (21.16) is set so that the time taken for the gas pressures in the two beds to equalise is essentially the same time taken to pump gas from (21.1) to (21.4).
  • Bed (21.2) cools as gas desorbs so its temperature profile drops from T3 and cools water returning from heat exchanger (21.8).
  • rate of heat transferred to the bed from the water exceeds the rate of heat generated by gas desorption the temperature profile having reached T5 starts to drop and returns to its original position T3. This represents the end of this stage of the cycle.
  • the gas pressure over the bed is Pl.
  • T6 until the rate of heat transferred to the water is greater than the rate of heat generation from gas adsorption.
  • the temperature profile having reached T6 then starts to drop and returns to its original position Tl. This represents the end of this stage of the cycle.
  • the pressure over the bed is Pl.
  • the overall effect of operation of the device is the transfer of heat via the water circuit from the heat exchanger (21.6) to heat exchanger (21.8).
  • At the end of the stage bed (21.3) is in the same state of temperature and pressure as (21.1) was at the beginning and bed (21.4) is in the same state of temperature and pressure as (21.2).
  • the positions of the valves controlling the water and CO 2 flows are now set to the positions shown in Figure 21(b).
  • the second stage of the cycle is essentially the same as the first described above but with beds (21.1) and (21.4) interchanged and beds (21.2) and (21.3) interchanged; the direction of the water flow is reversed.
  • the device is in the same stage as at beginning of the first stage.
  • Operating conditions will vary depending upon the desired temperature in the room and the external temperature. Typically water will enter (20.6) at 3 0 C to 1O 0 C and leave 7 0 C to 12 0 C.
  • the external temperature will be typically 25 0 C to 35 0 C.
  • the heat transfer fluid is air.
  • FIG. 22 shows a device based on multi-tube absorption beds. The operation of the device is anlogous to that shown in Figures 20 and 21.
  • a continuous adsorption heat pump device a 4-bed/2 array system was constructed as shown in Figure 22.
  • the system comprised an oil-free KNF diaphragm compressor model N 145 1.2AN18, 22.5 ; eight 2-way gas valves EP13PV40/30E from Beta Ltd (UK), 22.9 to 22.19; water pump KAG M42X30/1 from Fluid-o-Tech Ltd.
  • Each adsorption bed comprised an outer copper tube 105 mm long, outer diameter 56.09 mm, wall thickness 1.626 mm.
  • An inner copper heat exchange tube carried a water flow along the axis of the outer tube, outer diameter 12 mm, wall thickness 2 mm, to which was soldered a continuous spiral of copper wire loops which reached to ⁇ 2 mm of the containing tube.
  • a rod wrapped with copper wire was located within the inner tube to promote water turbulence.
  • Brass end caps were used to hold the inner and outer tubes together.
  • Inlet tubes at either end of the outer tube curved to allow the entry and exit of CO 2 980 g of 30/40 mesh granulated carbon absorbent obtained from Chemviron Carbon Ltd (UK) formulated for CO 2 adsorption occupied the volume between the inner and outer tubes and between the copper wire loops.
  • a filling port in brass end cap to allowed the introduction of the carbon.
  • Wire gauze filters at the CO 2 were used at the entry and exit points to prevent the carbon granules entering the connecting pipe work.
  • the dotted connecting lines represent the water circuit while the solid connecting lines represent the CO 2 circuit.
  • the device was operated with the 2-way valves set as shown in Figure 22(a) for the first part of the cycle.
  • the white circles represent open valves and the black circles closed valves.
  • For the second half of the cycle valves were set as shown in Figure 22(b).
  • When the CO 2 valves were operated the water flow was also reversed by operating valves (22.18 to 22.21) as shown in Figure 22(a) and (b).
  • the time between switching operations was set to 6 minutes.
  • the water flow rate through the beds and the ducts (22.6a and 22.8a) was set to 1 L/m and 0.97 L/m through ducts (22.8b and 22.6b).
  • CO 2 was pumped from bed (22.1) to bed (22.4) by the compressor.
  • the initial pressures of the two beds were 1.9 bara.
  • the maximum pressure reached in (22.4) when it reached its maximum pressure after pumping for 6 minutes was 4.05 bara.
  • the minimum pressure reached in (22.1) after suction for 6 minutes was 0.56 bara.
  • the average cooling Coefficient of Performance was calculated by dividing the heat removed from the water flowing through heat exchanger (22.6a) during one complete cycle by the difference between the heat transferred to the water in heat exchanger (22.8a) minus the heat removed from the water flowing through heat exchanger (22.6a). The value obtained was
  • the average heating COP was calculated by dividing the heat transferred to the water flowing through heat exchanger (22.8a) during one complete cycle by the difference between the heat transferred to the water in heat exchanger (22.8a) minus the heat removed from the water flowing through heat exchanger (22.6a). The value was 4.3.

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  • Engineering & Computer Science (AREA)
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  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Sorption Type Refrigeration Machines (AREA)

Abstract

L'invention concerne une pompe à chaleur comprenant des premier et second lits d'adsorption, chaque lit comprenant un solide poreux, le premier lit ayant un premier échangeur de chaleur et le second lit ayant un second échangeur de chaleur; un circuit pour un fluide de travail communiquant entre les lits; des moyens à vanne pour commuter des circulations de fluide de transfert de chaleur entre les premier et second échangeurs de chaleur; un compresseur connecté entre les moyens à vanne apte à amener un fluide de travail à circuler à l'intérieur du circuit entre les lits; le fluide de travail comprenant un gaz réactif capable d'adsorption et de désorption par le solide poreux; le premier échangeur de chaleur comprenant un premier conduit pour un fluide de transfert de chaleur; le second échangeur de chaleur comprenant un second conduit pour un fluide de transfert de chaleur; et une vanne de dérivation connectée entre les moyens à vanne en parallèle au compresseur et apte lorsqu'elle est ouverte à permettre un écoulement entre les lits évitant le compresseur.
PCT/GB2008/002080 2007-06-18 2008-01-18 Pompe à chaleur WO2008155543A2 (fr)

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GB0711829A GB0711829D0 (en) 2007-06-18 2007-06-18 Heat pump
GB0711829.2 2007-06-18
GB0715774A GB0715774D0 (en) 2007-08-14 2007-08-14 Heat pump
GB0715774.6 2007-08-14

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