CRITOPH, Robert Edward (4 Burberry Grove, Balsall Common, Coventry CV7 7RB, GB)
| CLAIMS: 1. A sorption device comprising a heat exchanger, the heat exchanger comprising: a cylindrical shell portion having at least one fluid sorbate port in a cylindrical face of the cylindrical shell portion arranged to allow a gaseous fluid sorbate to pass into and out from the shell portion, respectively; a plurality of tubes within an interior volume of the shell portion and substantially parallel to a longitudinal axis of the cylindrical shell portion, each tube having a side wall, each tube being arranged to allow thermal fluid to pass therethrough; and solid porous sorbent material at least partially filling the interior volume of the shell portion between the plurality of tubes arranged for fluid communication in use with fluid sorbate in the shell portion and for fluid isolation from thermal fluid in the tubes, and arranged such that in use thermal fluid flowing through the tubes is in thermal communication with the sorbent material through the side walls of the tubes. 2. A device as claimed in claim 1 , wherein an outer diameter of the tubes is 2.5 mm or less and a distance between longitudinal axes of respective adjacent tubes is substantially 3 mm or less. 3. A device as claimed in claim 2, wherein an outer diameter of the tubes is substantially 1.0 mm and the distance between longitudinal axes of respective adjacent tubes is substantially 3 mm. 4. A device as claimed in any preceding claim wherein the tubes are arranged in a substantially hexagonal array as viewed parallel to a longitudinal axis of a tube. 5. A device as claimed in any one of claims 1 to 3, wherein the tubes are arranged in a substantially square array as viewed parallel to a longitudinal axis of a tube. 6. A device as claimed in any preceding claim wherein a thickness of a wall of a tube is in the range from substantially 0.1 mm to substantially 0.5 mm. 7. A device as claimed in any preceding claim comprising a first manifold portion at a first end of the shell portion arranged to direct the thermal fluid into the tubes from a thermal fluid inlet of the device such that a rate of flow of fluid through respective tubes is substantially the same. 8. A device as claimed in claim 7, comprising a second manifold portion at a second end of the shell portion opposite the first end arranged to direct the thermal fluid from the tubes to a thermal fluid outlet of the device. 9. A device as claimed in any preceding claim, wherein the sorbate fluid inlet and sorbate fluid outlet of the shell portion are provided by respective different apertures. 10. A device as claimed in claim 9, wherein the sorbate fluid inlet aperture and sorbate fluid outlet aperture are provided at substantially opposite ends of the shell portion. 1 1. A device as claimed in any one of claims 1 to 8, wherein the sorbate fluid inlet and sorbate fluid outlet of the shell portion are provided by a single aperture. 12. A device as claimed in claim 1 1 , wherein the sorbate fluid inlet and outlet aperture is provided at a location substantially midway between opposed ends of the shell portion. 13. A device as claimed in any preceding claim, wherein the shell portion has a longitudinal portion and an end cap provided at at least one end of the longitudinal portion, the end cap being arranged to form a fluid-tight seal between the tubes and the longitudinal portion. 14. A device as claimed in claim 13, wherein the shell portion has an end cap provided at each end of the longitudinal portion thereby to form a fluid-tight shell portion. 15. A device as claimed in any preceding claim, wherein at least a portion of a plunger member is provided within the shell portion, the plunger member being a member arranged to allow compression of solid sorbent during a process of fabrication of the device. 16. A device as claimed in claim 1 to 7, wherein the plurality of tubes are coaxial tubes in which thermal fluid may be passed in opposite directions in an inner tube and an outer tube and wherein at a first end of the heat exchanger the inner tubes are in fluid communication with a first thermal fluid port and the outer tubes are in fluid communication with a second thermal fluid port and at a second end of the heat exchanger, opposed to the first end, the inner tubes are in fluid communication with the outer tubes to allow flow reversal of the thermal fluid. 17. A device as claimed in any of claims 1 to 7, wherein the plurality of tubes are U- shaped tubes with a first leg of the U-shaped tubes longer than a second leg wherein legs of the tube members of a first length are in fluid communication with a first thermal fluid inlet port and legs of the tube members of a second length are in fluid communication with a second thermal fluid port. 18. A method of manufacturing a sorption device comprising a heat exchanger, the method comprising: providing a cylindrical shell portion having at least one fluid sorbate port arranged to allow a gaseous fluid sorbate to pass into and out from the shell portion, respectively; providing a plurality of tubes within an interior volume of the cylindrical shell portion substantially parallel to a longitudinal axis of the shell portion, each tube having a side wall, each tube being arranged to allow a thermal fluid to pass therethrough; and providing a solid porous sorbent material at least partially filling the interior volume of the shell portion between the plurality of tubes arranged for fluid communication with the fluid sorbate and for fluid isolation from the thermal fluid, such that in use thermal fluid flowing through the pipes is in thermal communication with the sorbent material through the side walls of the tubes. 19. A method as claimed in claim 18, wherein the step of providing the solid sorbent material in the shell portion comprises the steps of: placing a quantity of solid sorbent material in the shell portion; and subsequently compressing the solid sorbent material. 20. A method as claimed in claim 19, wherein the step of compressing the solid sorbent comprises the step of compressing the solid sorbent by means of a plunger member. 21. A method as claimed in claim 20, further comprising the step of inserting the plunger member into the shell portion and translating the plunger member axially along a portion of a length of the shell portion parallel to a longitudinal axis of the shell portion. 22. A method as claimed in claim 21 , further comprising the step of removing the plunger member from the shell portion. 23. A method as claimed in claim 21 , comprising the step of leaving the plunger member within the shell portion whereby the plunger member is incorporated in the device. 24. A method as claimed in any one of claims 18 to 23, wherein the step of providing the shell portion further comprises the step of providing an end cap at at least one end of a longitudinal portion of the shell portion, the end cap being arranged to form a fluid-tight seal between the tubes and the longitudinal portion. 25. A method as claimed in claim 24, wherein the step of providing the shell portion further comprises the step of providing an end cap at each end of the longitudinal portion thereby to form a fluid-tight longitudinal portion. 26. A method as claimed in claim 24 or 25 depending through claim 21 , wherein the step of inserting the plunger member into the shell portion is performed after the step of providing an end cap at at least one end of the longitudinal portion of the shell portion. 27. A method as claimed in claim 24 or 25 depending through claim 21 , wherein the step of inserting the plunger member into the shell portion is performed after the step of providing an end cap at each end of the longitudinal portion of the shell portion. 28. A method as claimed in claim 24 or 25 depending through claim 21 , wherein the step of inserting the plunger member into the shell portion is performed before the step of providing an end cap at at least one end of the longitudinal portion of the shell portion. 29. A method of exchanging heat using a sorption device comprising a heat exchanger, the method comprising: passing a gaseous fluid sorbate from an evaporator through one of at least one fluid sorbate port in a cylindrical face of cylindrical shell portion of the heat exchanger to be adsorbed by a solid porous sorbent material partially filling an interior volume of the cylindrical shell portion between a plurality of tubes within the interior volume of the shell portion and substantially parallel to a longitudinal axis of the cylindrical shell portion; cyclically passing a thermal fluid at a higher temperature than the sorbate through the plurality of tubes, to heat the sorbent material, de-adsorb gaseous fluid sorbate from the sorbent material and drive the de-adsorbed sorbate through one of the at least one fluid sorbate port to a condenser; and cyclically passing thermal fluid at a lower temperature than the sorbent material through the plurality of tubes to cool the sorbent material and to draw gaseous fluid sorbent from the evaporator through the at least one fluid sorbent port to be adsorbed on the sorbent material. 30. A method as claimed in claim 29 for heating a first body in thermal communication with the condenser. 31. A method as claimed in claims 29 or 30 for cooling a second body in thermal communication with the evaporator. |
FIELD OF THE INVENTION The present invention relates to heat exchange apparatus and to a method of exchanging heat between fluids. In particular but not exclusively the invention relates to heat exchange apparatus for use in a heat pump.
BACKGROUND
In solid sorption refrigeration, heat pumping, air conditioning or thermal heat transformer systems there is a need alternately to heat and cool solid adsorbents. The heating and cooling processes must be as rapid as possible in order to minimise equipment size and cost. Solid adsorbent materials generally have low conductivity (typically 0.1 to 1.0 W/mK) and in order to maintain high energy efficiency the temperature differences between the heating or cooling fluid and the adsorbent must be low. Furthermore, the thermal mass of the containing vessel and heat exchange surfaces must be low compared to that of the adsorbent. US 4,581 ,049 discloses a solid absorber apparatus for a cyclic absorption process including a ribbed heat exchanger. The heat exchanger has a central plate with laminar ribs protruding from either side. On one side the ribs protrude into a volume filled with solid absorber material. On the other side the ribs protrude into a volume through which heat exchange fluid is passed. Heat transfer between the thermal fluid and solid absorber is effected through the central plate between ribs on opposite sides of the plate.
WO 2008/029185 discloses a heat exchanger in the form of a plurality of stacked plate assemblies. Each plate assembly comprises three plates; a first plate being a U- shaped spacer plate; a second plate having channels etched across a face thereof; and a third plate being a substantially flat, planar element. Abutment of a pair of plate assemblies defines a volume partially bounded by the U-shaped spacer plate in which solid sorbent is placed. Channels defined by abutment of the second and third plates allow a fluid heat exchange medium to flow in fluid isolation from the solid sorbent. The second and third plates are formed to have thin walls to allow heat conduction therethrough between thermal fluid and the solid sorbent. STATEMENT OF THE INVENTION In a first aspect of the invention there is provided a sorption device comprising a heat exchanger, the heat exchanger comprising: a cylindrical shell portion having at least one fluid sorbate port in a cylindrical face of the cylindrical shell portion arranged to allow a gaseous fluid sorbate to pass into and out from the shell portion; a plurality of tubes within an interior volume of the shell portion and substantially parallel to a longitudinal axis of the cylindrical shell portion, each tube having a side wall, each tube being arranged to allow thermal fluid to pass therethrough; and solid porous sorbent material at least partially filling the interior volume of the shell portion between the plurality of tubes arranged for fluid communication with fluid sorbate in the shell portion and for fluid isolation from thermal fluid in the tubes, and arranged such that in use thermal fluid flowing through the tubes is in thermal communication with the sorbent material through the side walls of the tubes.
A sorption device having a heat exchanger according to embodiments of the present invention has the advantage that heat may be rapidly and efficiently transferred between the thermal fluid and the sorbent material. This allows an enhancement of the performance of sorption devices to be attained.
It is known to provide a 'shell and tube' heat exchanger for exchanging heat between first and second fluids. FIG. 1 shows an example of a known shell and tube heat exchanger device. The device has a substantially cylindrical pressure vessel 10 having a plurality of tubes 20 passing therethrough parallel to a cylinder axis of the vessel 10.
Opposed ends of the vessel 10 are coupled to manifold portions 23, 25. The manifold portion 23 at one end of the vessel 10 is coupled to a fluid inlet 22 whilst a manifold portion 25 at an opposite end of the vessel 10 is coupled to a fluid outlet 24. A first fluid passing into manifold 23 is arranged to pass through the vessel 10 via the tubes 20 and out from the vessel via manifold 25.
The vessel 10 is provided with an inlet 12 in a wall of the vessel proximate one end of the vessel 10 and a corresponding outlet 14 in a wall of the vessel proximate an opposite end of the vessel 10. The inlet and outlet 12, 14 are arranged to allow a second fluid to be passed through the vessel such that the second fluid flows over an outer surface of each of the tubes 20. This allows heat to be exchanged between the first and second fluids whilst not allowing mixing of the first and second fluids. The present invention differs from the known shell and tube heat exchanger in that a heat exchanger according to embodiments of the present invention is employed in a sorption cooling system for exchanging heat between a solid sorbent material and a thermal fluid. Furthermore, in some embodiments the diameter and pitch of tubes of the heat exchanger is smaller than that of known shell and tube heat exchangers and optimised to obtain a compromise between high heat transfer rate between the solid sorbent and thermal fluid and low thermal mass. Preferably an outer diameter of the tubes is 2.5 mm or less and a distance between longitudinal axes of respective adjacent tubes is substantially 3 mm or less.
An outer diameter of the tubes may be substantially 1.0 mm and the distance between longitudinal axes of respective adjacent tubes may be substantially 3 mm.
The tubes may be arranged in a substantially hexagonal array as viewed parallel to a longitudinal axis of a tube.
Alternatively the tubes may be arranged in a substantially square array as viewed parallel to a longitudinal axis of a tube.
A thickness of a wall of a tube may be in the range from substantially 0.1 mm to substantially 0.5 mm. The device may comprise a first manifold portion at a first end of the shell portion arranged to direct the thermal fluid into the tubes from a thermal fluid inlet of the device such that a rate of flow of fluid through respective tubes is substantially the same.
The device may comprise a second manifold portion at a second end of the shell portion opposite the first end arranged to direct the thermal fluid from the tubes to a thermal fluid outlet of the device. The sorbate fluid inlet and sorbate fluid outlet of the shell portion may be provided by respective different apertures. The sorbate fluid inlet aperture and sorbate fluid outlet aperture may be provided at substantially opposite ends of the shell portion.
The sorbate fluid inlet and sorbate fluid outlet of the shell portion may be provided by a single aperture.
The sorbate fluid inlet and outlet aperture may be provided at a location substantially midway between opposed ends of the shell portion.
Preferably the shell portion has a longitudinal portion and an end cap provided at at least one end of the longitudinal portion, the end cap being arranged to form a fluid- tight seal between the tubes and the longitudinal portion.
More preferably the shell portion has a respective end cap provided at each end of the longitudinal portion of the shell portion thereby to form a fluid-tight longitudinal portion.
Optionally at least a portion of a plunger member may be provided within the shell portion, the plunger member being a member arranged to allow compression of the solid sorbent during a process of fabrication of the device. A ratio of an outer diameter of each tube to a spacing between longitudinal axes of respective adjacent tubes may be in the range of from around 1 :6 to around 2:3.
The ratio of the outer diameter of each tube to the spacing between longitudinal axes of respective adjacent tubes may be a function of the thermal conductivity of the sorbent material.
In a second aspect of the invention there is provided a method of manufacturing a sorption device comprising a heat exchanger, the method comprising: providing a cylindrical shell portion having at least one fluid sorbate port arranged to allow a gaseous fluid sorbate to pass into and out from the shell portion, respectively; providing a plurality of tubes within an interior volume of the cylindrical shell portion substantially parallel to a longitudinal axis of the shell portion, each tube having a side wall, each tube being arranged to allow a thermal fluid to pass therethrough; and providing a solid porous sorbent material at least partially filling the interior volume of the shell portion between the plurality of tubes, arranged for fluid communication with the sorbate fluid and for fluid isolation from the heat transfer fluid, such that in use thermal transfer fluid flowing through the pipes is in thermal communication with the sorbent material through the side walls of the tubes.
The step of providing the solid sorbent material in the shell portion may comprise the steps of: placing a quantity of solid sorbent material in the shell portion; and subsequently compressing the solid sorbent material.
The step of compressing the solid sorbent may comprise the step of compressing the solid sorbent by means of a plunger member.
The method may further comprise the step of inserting the plunger member into the shell portion and translating the plunger member axially along a portion of a length of the shell portion parallel to a longitudinal axis of the shell portion. Optionally the method further comprises the step of removing the plunger member from the shell portion.
Alternatively the method comprises the step of leaving the plunger member within the shell portion whereby the plunger member is incorporated in the device.
The step of providing the shell portion may comprise the step of providing an end cap at at least one end of a longitudinal portion of the shell portion, the end cap being arranged to form a fluid-tight seal between the tubes and the longitudinal portion. The step of providing the shell portion may comprise the step of providing an end cap at each end of the longitudinal portion thereby to form a fluid-tight longitudinal portion.
The step of inserting the plunger member into the shell portion may be performed after the step of providing an end cap at at least one end of the longitudinal portion of the shell portion. The step of inserting the plunger member into the shell portion may be performed after the step of providing an end cap at each end of the longitudinal portion of the shell portion. The step of inserting the plunger member into the shell portion may be performed before the step of providing an end cap at at least one end of the longitudinal portion of the shell portion.
According to a third aspect of the invention, there is provided a method of exchanging heat using a sorption device comprising a heat exchanger, the method comprising: passing a gaseous fluid sorbate from an evaporator through one of at least one fluid sorbate ports in a cylindrical face of cylindrical shell portion of the heat exchanger to be adsorbed by a solid porous sorbent material partially filling an interior volume of the cylindrical shell portion between a plurality of tubes within the interior volume of the shell portion and substantially parallel to a longitudinal axis of the cylindrical shell portion; cyclically passing a thermal fluid at a higher temperature than the sorbate through the plurality of tubes, to heat the sorbent material, de-adsorb gaseous fluid sorbate from the sorbent material and drive the de-adsorbed sorbate through one of the at least one fluid sorbate port to a condenser; and cyclically passing thermal fluid at a lower temperature than the sorbent material through the plurality of tubes to cool the sorbent material and to draw gaseous fluid sorbent from the evaporator through the at least one fluid sorbent port to be adsorbed on the sorbent material.
In embodiments of the invention the method may include heating a first body in thermal communication with the condenser by condensation of sorbate in the condenser and/or cooling a second body in thermal communication with the evaporator by evaporating sorbate in the evaporator.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying figures in which:
FIGURE 1 shows a known shell and tube heat exchanger for exchanging thermal energy between first and second fluids; FIGURE 2 shows a heat exchanger according to a first embodiment of a first aspect of the present invention;
FIGURE 3 shows stages in a process of fabricating a heat exchanger according to embodiment second aspect of the invention;
FIGURE 4 shows a vertical cross-section of a heat exchanger according to a second embodiment of the first aspect of the invention; and FIGURE 5 shows a vertical cross-section of a heat exchanger according to a third embodiment of the first aspect of the invention.
DETAILED DESCRIPTION In one embodiment of the invention a sorption device is provided having a heat exchanger 100 as shown in FIG. 2 for exchanging heat between a sorbent material 131 and a thermal fluid.
The heat exchanger 100 of the embodiment of FIG. 2 has a shell portion in the form of a substantially cylindrical pressure vessel 1 10. The pressure vessel 1 10 is sealed at opposed ends by end caps 1 1 1. Tube members 120 are arranged within the pressure vessel 1 10 along a length thereof parallel to a longitudinal axis of the pressure vessel 1 10. The tube members are supported at least in part by end caps 1 1 1. Manifold portions 123, 125 are provided at respective opposed ends of the pressure vessel 1 10.
The manifold portions 123, 125 are arranged to promote flow of fluid at substantially a same rate through each of the tubes of the heat exchanger 100.
The pressure vessel 1 10 is filled with solid sorbent material and arranged whereby a thermal fluid flowing through the tube members 120 is in thermal communication with the sorbent material 131.
In the embodiment of FIG. 2 a single sorbate inlet/outlet 1 12 is provided to the pressure vessel 1 10 to allow a sorbate to pass into and out from the pressure vessel 1 10. In some alternative embodiments a separate sorbate inlet and a separate sorbate outlet are provided. In some embodiments, the tube members 120 have a diameter (D tU be) of less than around 2 mm, preferably around 1 mm. A distance between cylindrical axes (L P | tCh ) of respective adjacent tube members 120 may be around 3 mm. Tube members 120 may be arranged in a square array (see FIG. 2 (b)) or a hexagonal array (see FIG. 2 (c)). Other arrangements are also useful.
Referring to FIG. 4, in some embodiments of a cylindrical heat exchanger 410 the tube members are coaxial tubes 421 , 422 in which thermal fluid may be passed in opposite directions in an inner tube 421 and an outer tube 422. At a first end of the heat exchanger 410 the inner tubes 421 are in fluid communication via a first manifold 423 with, for example, a thermal fluid inlet 412 and the outer tubes 422 are in fluid communication via a second manifold 425 with a thermal fluid outlet 413. At a second end of the heat exchanger 410, opposed to the first end, the inner tubes 421 are in fluid communication with the outer tubes 422 to allow flow reversal of the thermal fluid. A sorbate inlet 441 is provided in a cylindrical wall of the heat exchanger for passing a fluid sorbate into an inner volume of the heat exchanger 410 to be adsorbed by a sorbent 431 therein. De-adsorbed sorbent passes out of the heat exchanger through a similar sorbate outlet 442. Although only a single coaxial tube has been shown in FIG. 4 in the interests of clarity, it will be understood that an array of coaxial tubes is provided.
Referring to FIG. 5, in other embodiments of a cylindrical heat exchanger 510 the tube members are U-shaped tubes 521 , 522, preferably with a first leg 521 of the U-shaped tube longer than a second leg 522. Legs of the tube members of a first length are in fluid communication via a first manifold 523 with a thermal fluid inlet 512 and legs of the tube members of a second length are in fluid communication via a second manifold 525 with the thermal fluid outlet 513. A sorbate inlet 541 is provided in a cylindrical wall of the heat exchanger for passing a fluid sorbate into an inner volume of the heat exchanger 510 to be adsorbed by a sorbent 531 therein. De-adsorbed sorbent passes out of the heat exchanger through a similar sorbate outlet 542. Although only a single U-shaped tube has been shown in FIG. 5 in the interests of clarity, it will be understood that an array of U-shaped tubes is provided.
It will be understood that in the embodiments of FIG. 4 and FIG. 5 that there will be some undesirable heat transfer between incoming and outgoing streams of thermal fluid. In that respect U-shaped tubes are preferable to coaxial tubes. However, a flow rate of the thermal fluid tends to be sufficiently high, that a temperature drop between incoming and outgoing thermal fluid is quite small and a temperature difference between the thermal fluid and the adsorbent is much higher. A possible advantage of coaxial tubes is that the adsorbent is easier to pack but more heat transfer per kilogram of tube would be obtained with the U-shaped tube embodiment.
It will be understood that the fluid sorbate inlet may be in fluid communication with an evaporator in thermal communication with a first body for cooling the first body and/or the fluid sorbate outlet may be in fluid communication with a condenser in thermal communication with a second body for heating the second body.
The heat exchanger 100 of FIG. 2 may be fabricated according to a method in which a sorbent compression process is performed in order to enhance the thermal conductivity as illustrated in FIG. 3.
FIG. 3(a) shows a heat exchanger 100 under construction. The pressure vessel 1 10 can be seen having a single end cap 1 1 1 installed, the end cap 1 1 1 supporting tube members 120. A quantity of sorbent material 131 has been placed in the pressure vessel 110.
FIG. 3(b) shows a ram member 160 inserted into the pressure vessel 1 10, the tube members 120 being arranged to pass through the ram member 160 whereby the ram member 160 may be used to compress the sorbent material without damaging the tube members 120.
Once compression of the sorbent material 131 has been effected, further sorbent may be added to the pressure vessel 1 10 before repeating the compression process.
Alternatively, both end caps 1 1 1 can be installed before compression of sorbent is effected and the ram member 160 arranged to be of sufficiently low axial thickness that it can be left inside the pressure vessel 1 10 after the sorbent has been compressed.
In a further alternative embodiment, the end caps 1 1 1 may be installed before compression of sorbent is effected and the ram member 160 shaped whereby it can be inserted between rows of tubes, used to compress the adsorbent and then removed. In some embodiments the ram member 160 comprises a plurality of components to allow insertion and removal in this manner.
It is to be understood that other methods of fabricating a heat exchanger 100 according to embodiments of the invention are also useful.
The end caps 1 1 1 , may be attached to the shell portion of the pressure vessel 1 10 by a variety of joining methods including brazing (e.g. nickel brazing or copper brazing), welding, soldering, diffusion bonding, metal spraying, adhesive bonding or any other suitable joining technique.
Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.
Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith.