Patent Application
20080023181
a is a perspective view of an adsorption heat exchanger according to one embodiment of the present invention;
b is a close-up view of a portion of
c is a close-up view of another portion of
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
Broadly, the present invention provides adsorption heat exchangers for adsorption heat pumps and adsorption applications. Embodiments of these exchangers are not in themselves intended to promote heat transfer in a general sense, rather they are intended to enhance the transport of sensible heat from a heat transfer fluid into the adsorbent coating applied to the plurality of adsorbent layers, these exchangers are thus efficient at adsorbing and desorbing a working fluid such as water, and methods for using the same. Embodiments of the present invention may find beneficial use in industries such as the automotive, electricity generation and aerospace industries. Embodiments of the present invention may be useful in applications including adsorption refrigeration systems, adsorption based air conditioning systems and environmental control systems. Embodiments of the present invention may be useful in any heat transport application where in it is desired to efficiently heat or cool an adsorbent mass to promote adsorption or desorption of a working fluid. Such adsorbent heat exchangers may find use in applications including, but not limited to, heat transport for automobile air conditioning systems.
In one embodiment, the present invention provides an adsorption heat exchanger having a stack of alternating adsorption layers and heat transfer layers. The adsorption heat exchanger can comprise a stack of alternating corrugated sheets and separator plates. The corrugated sheets can be oriented in an alternating manner to provide an adsorption flow path in one direction and a heat transfer flow path in another direction (about 90° to the adsorption flow path). The surfaces defining the adsorption flow path can be coated with an adsorptive material. Unlike the prior art tube-lamellas design, the present invention can comprise a plate-corrugated sheet-plate design. For some embodiments, the plate-corrugated sheet-plate design allows for enhanced primary surface area and more efficient heat and mass transfer.
Unlike the prior art that includes adsorptive paper laminates, the adsorptive material of the present invention can be applied directly to a brazed heat exchanger assembly, reducing production time. Additionally, the adsorptive material coating of the present invention can provide a reduction in coating thickness and attendant enhancement of both heat and mass transfer. Also unlike the prior art paper laminate designs, the outside surface of the heat transfer fluid flow path of the present invention can be coated with adsorptive material, which may further increase adsorptive material surface area.
Moreover, unlike the prior art wherein the heat transfer fluid flow path comprises a tube, the heat transfer fluid flow path of the present invention can include a corrugated sheet that extends between and in contact with two separator plates. The corrugated sheet can form a plurality of fins running parallel to the flow of heat transfer fluid. The fins can increase heat transfer to the adsorption layer without adversely affecting the flow of the heat transfer fluid.
Embodiments of the present invention may include an adsorption heat exchanger 40 designed to thermally connect with a sorptive cooling system 41, as depicted in
During operation of the sorptive cooling system 41, heat from a flow of heat transfer fluid 69 (see
When further heating of the adsorptive material coating 46 no longer produces desorbed adsorbate from the adsorptive material coating 46, the adsorption heat exchanger 40 can be isolated and allowed to return to the adsorption conditions. When the adsorption conditions are established in the adsorptive material coating 46, the adsorbate vapor from the evaporator 43 can be reintroduced to the adsorption heat exchanger 40 to complete the cycle. Generally two or more adsorption heat exchangers 40 may be employed in a typical cycle wherein one adsorption heat exchanger 40 is heated during the desorption stroke and a second adsorption heat exchanger 40b is cooled during the adsorption stroke. The time for the completion of a full cycle of adsorption and desorption is known as the “cycle time.”
The adsorption heat exchanger 40, according to an embodiment of the present invention is shown in
The adsorption layer 50 may provide an adsorption flow passage 53 through the adsorption heat exchanger 40. The adsorption flow passage 53 may be in a direction parallel to an adsorption flow line 54. The heat transfer layer 51 may define a heat transfer flow passage 55 through the adsorption heat exchanger 40. The heat transfer flow passage 55 may be in a direction parallel to a heat transfer flow line 56. The adsorption flow line 54 may be about 90° from the heat transfer flow line 56.
The adsorption layer 50, as depicted in
The adsorption zone fins 58 may be positioned about perpendicular to the separator plates 52 and may extend about parallel to the adsorption flow line 54. The adsorption zone fins 58 may direct the flow of adsorbate 60 (see
The density of adsorption zone fins (fins/inch) may vary with application and may depend on factors including the thickness of the adsorptive material coating 46 and the desired volume of the adsorption flow passage 53. The density of the adsorption zone fins 58 may be defined as the number of fins per inch of adsorption layer width as measured perpendicular to the adsorption flow line 54 and parallel to the separator plate 52. For some applications, the density of the adsorption zone fins 58 may be between about 7 fins/inch and about 28 fins/inch.
The adsorption zone contact portions 59 may be positioned about parallel to and in contact with the separator plates 52. The adsorption zone contact portions 59 may be brazed to an adsorption zone facing side 62 of the separator plates 52. The adsorption zone contact portions 59 may provide a support for at least a portion of the adsorptive material coating 46, as depicted in
For some applications, in lieu of the adsorption zone corrugated sheet 57, the adsorption layer 50 may comprise a plurality of adsorption zone fins 58 brazed directly to the separator plates 52. The adsorption zone fins 58 of the adsorption layer 50 may increase the surface area available for adsorptive material coating 46, thereby enhancing the adsorption/desorption efficiency of the adsorption heat exchanger 40.
The adsorption layer 50 may include two adsorption zone header bars 65, as depicted in
The adsorption zone corrugated sheet 57, the adsorption zone fin 58, the adsorption zone contact portion 59 and adsorption zone header bar 65 each may comprise a material, such as but not limited to, aluminized mylar, a polymer composite, or a metal. Useful metals may include aluminum, copper, titanium, brass, stainless steel, other light metals and alloys with high conductivity, and graphite fiber composite materials. Components of the adsorption layer 50 may provide support for the adsorptive material coating 46.
The adsorptive material coating 46 of the adsorption layer 50 may define the adsorption flow passage 53, as depicted in
For some embodiments of the present invention, the adsorptive material coating 46 may include a zeolite. Zeolites may comprise microporous aluminosilicate compounds and may be commonly referred to as molecular sieves. Molecular sieves may have the ability to selectively adsorb molecules based primarily on a size exclusion process. This may be due their very uniform pore structure and molecular dimensions. The maximum size of the molecular or ionic species that can enter the pores of a zeolite may be controlled by the diameter of the pores. Zeolites have been widely used in industrial processes due to their structural stability and inherent exothermic reaction during adsorb/desorb cycles.
Useful adsorptive material coating compositions and methods for application may include the compositions and methods described in U.S. Pat. Nos. 5,120,694 and 5,518,977, both of which are incorporated herein by reference. Useful adsorptive coating application methods may comprise a step of heating a component to be coated, a step of contacting the surface of the component with a slurry comprising an adsorbent and a binder to form an adsorptive material coating 46, and a step of hardening the adsorptive material coating 46. For some applications, the step of contacting may comprise dipping the surface into the slurry or spraying the surface with the slurry.
The adsorptive material coating 46 may have an adsorptive coating thickness 77 (see
The adsorptive material coating surface area (external or face area of the coating) may not affect the adsorptive surface area (surface area available for adsorption). Due to the micro-porous structure of the adsorptive material coating 46 the adsorptive surface area may be a function of the mass of adsorptive material coating applied as opposed to the external or face area of the coating. For a given mass of adsorptive material coating 46, increasing the external or face area of the coating may increase heat transfer efficiency because an increased face area may allow for a reduction in adsorptive coating thickness 77. The coating surface area (both the face area and the adsorptive surface area) may be increased further by the application of adsorptive material coating 46 to the adsorption zone facing side 62 of the separator plates 52 and to the adsorption zone contact portions 59.
The heat transfer layer 51 may include a heat transfer zone corrugated sheet 66, as depicted in
The heat transfer zone fins 67 may be positioned about perpendicular to the separator plates 52 and may extend about parallel to the heat transfer flow line 56. The heat transfer zone fins 67 may direct the flow of heat transfer fluid 69 (see
The density of heat transfer zone fins (fins/inch) may vary with application and may depend on factors including the composition of the heat transfer fluid 69 and the desired volume of the heat transfer flow passage 55. The density of the heat transfer zone fins 67 may be defined as the number of fins per inch of the heat transfer layer width as measured perpendicular to the heat transfer flow line 56 and parallel to the separator plate 52. For some applications, the density of the heat transfer zone fins 67 may be between about 10 fins/inch and about 30 fins/inch.
The heat transfer zone contact portions 68 may be positioned about parallel to and in contact with the separator plates 52. The heat transfer zone contact portions 68 may be brazed to a heat transfer zone facing side 72 of the separator plates 52. For some applications the heat transfer zone contact portions 68 may have a heat transfer contact portion width 73 of between about 0.03 inches and about 0.1 inches. The heat transfer contact portion width 73 may vary and may depend on the desired density of the heat transfer zone fins 67. The heat transfer contact portion width 73 may be inversely proportion to the density of the heat transfer zone fins 67.
For some applications, in lieu of the heat transfer zone corrugated sheet 66, the heat transfer layer 51 may comprise a plurality of heat transfer zone fins 67 brazed directly to the separator plates 52.
The heat transfer layer 51 may include two heat transfer zone header bars 74, as depicted in
The heat transfer zone corrugated sheet 66, the heat transfer zone fin 67, the heat transfer zone contact portion 68 and heat transfer zone header bar 74 each may comprise a material, such as but not limited to, aluminized mylar, a polymer composite, or a metal. Useful metals may include aluminum, copper, titanium, brass, stainless steel, other light metals and alloys with high conductivity, and graphite fiber composite materials.
The separator plate 52 of the adsorption heat exchanger 40 may comprise a sheet material structure, as depicted in
The adsorption heat exchanger 40 further may comprise two side plates 76, as depicted in
A method 200 of generating a flow of adsorbate 60 is depicted in
The step 210 may comprise passing the flow of heat transfer fluid 69 such that the flow of heat transfer fluid 69 is in contact with at least one heat transfer zone fin 67 of the absorption heat exchanger 40 and in contact with at least a portion of a heat transfer zone facing side 72 of the separator sheet 52. For some applications, the flow of heat transfer fluid 69 may comprise a liquid, such as but limited to, water, alcohols, ammonia, hydrocarbons, chloroflorocarbons, and mixtures thereof.
For some applications, the method 200 can use the adsorptive material coating 46 to reduce the partial pressure of the flow of adsorbate 60 (e.g. water or other working compound) in an adsorption loop 45 and thereby cause the adsorbate 60 to be evaporated from an evaporator 43. The liquid adsorbate 60 inside the evaporator 43 becomes cooler as it loses the corresponding heat of vaporization, while the adsorptive material coating 46 becomes hotter from the heat of adsorption. For some applications, the regeneration cycle may use a supply of hot water or air heated by waste heat from an engine exhaust to remove adsorbate 60 and regenerate the adsorptive material coating 46. Two adsorption heat exchangers 40 may be used in alternating cycles for some applications.
A plot of specific power (kW/kg) as a function of cycle time (sec.) is shown in
The design parameters for one embodiment of the present invention are shown
The sensitivity results on adsorption material coating thickness variations are shown in
The design and performance parameters for an adsorption heat exchanger according to nine embodiments of the present invention are shown in
For the prior art tube-plate AHE, heat transfer to adsorptive material occurs mainly by conductance in a chain of tube-tube/plate contact-plate-adsorptive material. The quality of tube-plate and adsorbent-plate contacts is extremely important in achieving high heat and mass transfer efficiency during adsorption/desorption cycles and, consequently, for their duration. Heat and mass transfer efficiency affect the specific power of heat exchanger.
The fin-plate design of the present invention can provide high surface area and enhance heat and mass transfer from the heat transfer fluid to the adsorbent material. This along with a thinner adsorbent layer (adsorptive material coating 46) can significantly reduce adsorption/desorption cycle time and increase the specific power of the adsorption heat exchanger 40 for some applications.
As can be appreciated by those skilled in the art, the present invention provides improved adsorption heat exchangers. Embodiments of the present invention provide heat exchangers having enhanced adsorption/desorption efficiency and high heat transfer efficiency. The increased adsorptive material surface area and improved heat transfer efficiency of the present invention can provide heat exchangers with reduced cycle time.
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
