Abstract:
To cool heat-emitting electronic components, a compact, non-moving-parts compressor, an evaporator in juxtaposition to the electronic components and a condenser are mounted as a unit, preferably within a vacuum can. A heat exchanger is mounted external to the can but in proximity to the condenser. The foregoing comprise a unit which may be detachably connected to a host pump and heat exchanger. The unit may be removed from the system of which it is a part for upgrade and maintenance. All its components are thermally isolated from the ambient atmosphere to prevent water vapor condensation corrosion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application is a continuation of U.S. patent application Ser. No. 09/693,344 filed on Oct. 19, 2000, now U.S. Pat. No. 6,279,337, which is a divisional of U.S. patent application Ser. No. 09/160,636 filed on Sep. 24, 1998, now U.S. Pat. No. 6,138,469, which is a continuation-in-part of U.S. patent application Ser. No. 08/821,258 filed on Mar. 20, 1997, now U.S. Pat. No. 5,855,119, which is a continuation-in-part of U.S. patent application Ser. No. 08/811,759 filed on Mar. 6, 1997, now U.S. Pat. No. 5,855,121, which is a continuation of U.S. patent application Ser. No. 08/533,153 filed on Sep. 20, 1995, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the invention. 
     The present invention relates to sorption systems wherein a sorbate is alternately adsorbed onto and desorbed from a sorbent. More particularly, the invention relates to a refrigeration sorption system for cooling electrical components wherein the sorbate is desorbed from the sorbent using electromagnetic waves. 
     2. Related Art. 
     Certain electrical components, such as the microprocessors in conventional computers, generate a substantial amount of heat during operation. It has been determined that the performance of a microprocessor can be enhanced significantly by effectively removing this heat. In addition, in accordance with conventional semiconductor practice, it is known that the operating speed of a microprocessor can be greatly increased if the microprocessor is operated at low temperatures. 
     In adsorption and desorption systems, which will be referred to herein as “sorption systems”, a first substance called a sorbate is alternately adsorbed onto and then desorbed from a second substance called a sorbent. Specific sorbates and sorbents will usually be selected for a particular sorption system to produce a desired effect, which is dependent on the affinity of the two substances. During an adsorption reaction, which is also referred to as the adsorb cycle or the adsorb portion of the sorption cycle, the sorbate is drawn .onto and combines with the sorbate to produce a sorbate/sorbent compound. During the desorption reaction, which is also called the desorb cycle or the desorb portion of the sorption cycle, energy is supplied to the sorbate/sorbent compound to break the bonds between the sorbate and sorbent molecules and thereby desorb, or in other words separate or drive off, the sorbate from the sorbent. Substantial energy is imparted to the sorbate during the desorption reaction, and this energy can be harnessed for various uses. 
     An exemplary refrigeration sorption system may use a polar refrigerant, such as ammonia, as the sorbate and a metal halide salt, such as strontium bromide, as the sorbent. During the desorption reaction, which occurs in an enclosure called a sorber, the refrigerant molecules are driven off of the salt and, into a relatively high pressure, high energy gaseous state. The refrigerant gas is subsequently condensed and then. evaporated to produce a cooling effect. The evaporated refrigerant gas is then channeled back to the sorber, where it is once again adsorbed onto the salt in an adsorption reaction. The sorption cycle is repeated numerous times depending on the cooling requirements of the refrigeration system. 
     In certain prior art sorption systems, the desorption energy is supplied by a conventional heater. In such a system, a great deal of thermal energy is required to stochastically heat the sorbate/sorbent compound to the degree sufficient to break the bonds between the sorbate and sorbent molecules. As a result, the sorbate, sorbent and sorber are significantly heated, and substantial time and/or energy are required to remove this sensible heat and cool the sorbers and sorbent before the next adsorption reaction can proceed. 
     In the refrigeration system of this invention, the desorption energy is supplied in the form of electromagnetic waves, such as radio frequency waves or microwaves, generated by, for example, a magnetron. Instead of heating the sorbate/sorbent compound, the electromagnetic waves selectively pump electrical energy into each sorbate-sorbent bond until the bond is broken and the sorbate molecule is separated from the sorbent molecule. Therefore, the sorbate, sorbent and sorber are not heated during the desorption reaction and consequently do not need to be cooled before the next adsorption reaction can proceed. As the desorption reaction is essentially isothermal, the overall performance of the refrigeration system is greatly improved. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a refrigeration system for cooling an electrical component is provided which comprises a sorber having a housing defining an enclosure, a sorbate/sorbent compound located within the enclosure, the sorber including a port through which a sorbate may be communicated into and out of the enclosure, and means for electrically coupling the sorber to an electromagnetic wave generator, wherein electromagnetic waves transmitted by the electromagnetic wave generator are propagated through the enclosure to desorb the sorbate from the sorbate/sorbent compound. The refrigeration system of the present invention also includes a condenser connected to the port downstream of the sorber, an evaporator connected between the condenser and the port and positioned in close proximity to the electrical component, and a controllable expansion valve interposed between the condenser and the evaporator. In this manner sorbate which is desorbed in the sorber is condensed in the condenser and then controllably released into the evaporator to create a cooling effect and thereby cool the electrical component, after which the sorbate is drawn back into the sorber. 
     The absorbent bed must be able to provide sufficient heat and mass transport capabilities to allow for rapid adsorption of the refrigerant vapor. Without sufficient heat removal, the mass flow would have to be reduced, or alternately cooling power would be lost as the adsorption pressure would rise with sorbent bed temperature. Consequently, the goal is to maintain the adsorbent bed as close to the hot side heat rejection temperature as possible. The electromagnetic nature of the desorption phenomena places further restrictions on the architecture of the reactors as it cannot interfere with the propagation of microwave plane waves (TEM). 
     A microchannel reactor design is provided to satisfy the foregoing requirements. Although microchannels are often envisioned as being rectangular parallel channels, the exact geometry of the channels has very little effect on heat and mass transfer characteristics. Rather, the performance of the channels is largely dictated by channel depth and flow rate parameters. Flexibility and channel geometry accommodate the electromagnetic compatibility requirements of the reactor. 
     Microchannel reactors operate on the principle that within a microchannel, the thermal boundary layer is structurally constrained to less than half of the width of the fluid channel. Heat transfer and laminar and transition flow regimes vary significantly from macroscale channels. Heat transfer in flow regimes is coupled to liquid temperature, velocity and channel size. 
     One feature of the invention is that the refrigerator and component cooled thereby may be conveniently removed from the system for upgrade or maintenance. 
     In accordance with the present invention, it is important that all chilled components of the system must be isolated from the ambient atmosphere to prevent condensation from forming on the cooled parts or on the external surfaces of paths to the cooled parts which are exposed to the atmosphere. Isolation prevents corrosion and other problems which are caused by the presence of condensed water. 
     One of the features of an embodiment of the system is that the desorption compressor is physically compact. This permits the compressor to be placed inside the removable module which includes the electronic components. The removable interface is associated with the hot end condenser of the refrigeration system. The hot end condenser is either a part of a countercurrent liquid-to-liquid heat exchanger or is cooled by evaporating a liquid from the hot surface. The demountable interface is the low pressure liquid loop to the heat exchanger. Detaching the module from the low pressure liquid loop is preferably accomplished using conventional double ended shut off fluid disconnects. 
     The isolation of the system from the atmosphere is obtained by enclosing the unit in a vacuum can. The hot end condenser may be used as one surface of the vacuum can (or a portion thereof) or be in close heat transferring proximity thereto. The compressor, evaporator, and cooled electronic components are supported away from the surface of the vacuum can so that there is no direct connection between an external surface of the vacuum can and the evaporator. This arrangement makes water vapor condensation unlikely and prevents corrosion of parts. 
     The high speed electrical signal connections to the electronic components may be made by means of optical coupling, utilizing fiber optics or by free space transmission through a window, in all situations providing for best thermal performance. It is also possible to provide such connections using a thin film on a polymer or glass flex circuit, although such a connection has potential difficulties in balancing the conflicting requirements of high thermal impedance with low electrical losses. 
     DC Power for the electronic components may be brought into the vacuum can through power feed-throughs which are thermally lagged to the hot end condenser before connecting to the cooled components. 
     It will be understood that the functions of the apparatus herein described include the following: 
     1. Providing a high insulation environment for low temperature cooling. 
     2. Providing an optical coupling into and out of this environment. 
     3. Providing a single high side heat removal path for both the cooling shell (heat load) and the solid state chemical reactor (sorber assembly) by using a single high side heat exchanger. 
     4. The device benefits from compactness, ease of fabrication, serviceability and modularity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description serve to explain the principles of the invention. 
     FIG. 1 is a schematic view of an embodiment of a cooling system for electronic components. 
     FIG. 2 is a schematic view of another embodiment of a cooling system for electronic components. 
     FIG. 3 is a schematic view of another embodiment of a cooling system for electronic components. 
     FIG. 4 is a schematic exploded perspective view of the modification of FIG. 1, partially broken away in section to reveal internal construction. 
     FIG. 5 is a view similar to FIG. 4 taken from a different angle. 
     FIG. 6 is a perspective view showing the structure of FIG. 1 with parts broken away to reveal internal construction. 
     FIG. 7 is a perspective view, partly broken away in section to reveal internal construction, of an embodiment of a compressor. 
     FIG. 8 is an enlarged view of a portion of FIG.  7 . 
     FIG. 9 is a perspective view of an alternate embodiment of a compressor that may be used in the cooling system embodiment shown in FIG.  2 . 
     FIG. 10 is an enlarged perspective view of a portion of FIG. 9 with parts broken away to reveal internal construction. 
     FIG. 11 is a perspective view of the bottom of the structure of FIG.  9 . 
     FIG. 12 is a perspective view, with parts broken away to reveal internal construction, of still another modification. 
     FIG. 13 is an enlarged view of a portion of FIG.  12 . 
     FIG. 14 is a perspective view of the compressor of FIGS. 12 and 13, viewed from a different angle. 
     FIG. 15 is an exploded perspective view of a further modification. 
     FIG. 16 is a perspective view of the structure of FIG. 15 assembled with a portion thereof broken away to reveal internal construction. 
     FIG. 17 is a perspective view of a portion of the structure of FIG. 16, viewed from a different angle. 
     FIG. 18 is an enlarged view of a portion of the structure of FIGS.  15 - 17 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     FIG. 1 illustrates schematically the interrelationship of the components of the present invention. The particular electronic components  21  mounted on board  22  are subject to wide variation. In general they are chips or the like which emit heat and which operate at optimum efficiency at reduced temperatures. In close relationship to the components  21  is the evaporator  26  which emits cold gaseous fluid through emission apertures in a porous ceramic blocks  27  inset into the metal evaporator  26 . Porous metal or glass frit plugs are likewise suitable. The number and the location of blocks  27  is subject of wide variation but, as shown in FIG. 1, are located immediately opposite a corresponding component  21 . Channels  28  within the evaporator  26  interconnect blocks  27 . The blocks  27  may function as valves to control emission of gas or a separate expansion valve  25  may also be used. Board  22  and evaporator  26  are isolated within a cell  23  which collects the gas emitted through apertures  27 . Preferably standoffs  24  which may be of any of a variety of shapes separate the components  21  and evaporator  26  from the walls of cell  23 . 
     Cell  23  is connected by conduit  34  to compressor  33  and thence by conduit  32  to condenser  31 . The compressed, condensed gases are then recirculated by means of conduit  29  to evaporator  26  preferably through expansion valve  25 . Compressor  33  is hereinafter discussed in detail. 
     Preferably board  22 , evaporator  26 , compressor  3  and refrigerator hot end condenser are isolated from the atmosphere by means of a vacuum can  36 . In a preferred construction condenser  31  comprises at least a portion of one wall of vacuum can  36  or is in close proximity thereto so that heat transfer through the vacuum can occur. 
     Immediately outside can  36  is a host heat exchanger  37  which absorbs heat from condenser  31 . The liquid-to-liquid exchange of heat between condenser  36  and heat exchanger may be of any suitable type. Located apart from vacuum can  36  and heat exchanger  37  (it being understood that the latter is physically attached to condenser  31  and to can  36 ) is a host pump and heat exchanger  38 . Heat exchanger  38  may be of widely different types, well understood in the art, preferably of a liquid-to-air type. One such device is LYTRON 5000 Series, by Lytron, Inc. of Woburn, Mass. The connections between exchanger  37  and exchanger  38  are such that decoupling may be readily accomplished as by means of quick disconnect elements  39 . Snap Tite Series 28-1, by Snap-Tite of Union City, Pa. or other quick disconnects are suitable. 
     A port  41  may pass into vacuum can  36 . The port  41  may also pass into cell  23 . The port  41  allows optical or electrical input/output conduits from an electronic system to be attached to the electronic components  21  and/or the board  22 . Connectors attached to the conduits may allow a cooling system for electrical components  21  to be removed as a unit from the electronic system. The unit include the host heat exchanger  37 , the can  36 , members of the cooling system within the can, the components  21 , and the board  22 . 
     An optical I/O  41  which passes through the can  36  and cell  23  may control the electronic components  21  or other means as heretofore discussed may be substituted, such as electrical I/OS. 
     Some additional structural details of the components may be observed in FIGS. 4-6. Thus, the vacuum can  36  may be fabricated in two parts namely an upper half  56  having a peripheral external flange  57  and a lower half  58  having a flange  59  which mates with flange  57 . Similarly, cell  23  may comprise an upper half  61  and a lower half  62  which are suitably sealed together. 
     FIG. 2 illustrates a modification of FIG. 1 wherein compressor  33   a  is located adjacent a wall of vacuum can  36   a , the wall being pervious through a window and wave guide  47  to emissions from magnetron  46 . A magnetron similar to those used in microwave ovens is satisfactory. For such purpose, compressor  33   a  is provided with probes  48  which serve as antennas for e field emissions from the magnetron  46 . 
     FIG. 3 is a further modification resembling FIG. 2 wherein the loop antennae  51  are of a different style than the elements  48  of FIG.  2 . 
     In other respects, the modifications of FIGS. 2 and 3 resemble those of FIG.  1  and the same reference numerals followed by subscripts a and b respectively represent corresponding parts. 
     A series of representative compressors are illustrated and described herein. It will be understood that these are merely representative of compressors which may be used in accordance with the present invention. Turning to the form shown in FIGS. 7 and 8, a plurality of parallel tubes  66  each lined with a sorbent as hereinabove defined is provided. Although the compressor shown in FIGS. 7-8 is round in cross-section, other shapes may be used. At one end thereof is a manifold  67  into which the output of cell  23  is conveyed so that the gas flows through the tubes  66  and interacts with the sorbent thereon. Also, entering the compressor  33   a  through manifold  67  is RF connector  68  which leads to a splitter  69  having a plurality of applicators  70  leading down through the tubes  66 . At such time as it is necessary to desorb the material in the tubes  66 , microwave or other waves are applied in the insides of the tubes  66  causing the gas to be released into manifold  71  at the opposite end of the compressor  33   a , from which the gases may be conducted to condenser  31  by means of conduit  34   a . The tubes  66  may be enclosed in a jacket  72 . Optionally, a coolant liquid may be introduced into the jacket  72  through inlet port  73  and conducted out through outlet port  74 . 
     FIGS. 9-11 also shows a coaxial seal applicator array, but differs in the excitation mechanism and size of the applicators. In this embodiment, the compressor  33   b  is rectangular in shape. It will be understood that the shape is subject to variation. As here shown, compressor  33   b  is formed with a body  81  into which are recessed pockets  82  each lines with a sorbent. Applicators  83  are introduced through seals  84  in the top of body  81  and extend down through the pockets  82 . Applicators  83  may resemble the probe antennas  48  shown in FIG. 2 or may be otherwise constructed. 
     Bottom plate  86  is sealed to body  81  and is formed with passageways  87  connected to conduits  32  and  34  (not shown). Ducts  88  interconnect pockets  82  with passageways  87  as best shown in FIG.  10 . Optionally, cooling passageways  89  may be formed in body  81  for cooling purposes. 
     FIGS. 12-14 illustrate another compressor  33   c  having a flat coaxial applicator array. Block  91  is formed with parallel longitudinal bores  92 , each lined with sorbent. At one end of block  91  is manifold  93  having an RF connector  94  leading to a splitter  96  within the manifold  93 . From splitter  96  lead waveguide applicators  97 , one of which extends down through the longitudinal axis of each bore  92 . At the end of block  91  opposite manifold  93  is a manifold  98  having connector  32   c  at one end and connector  34   c  at the opposite end. For cooling purposes, optional longitudinal grooves  99  may be formed on the exterior of block  91  and a cover (not shown) over block  91  provides for circulation of cooling fluid through the grooves  99 . 
     Still another compressor  33 d is shown in FIGS. 15-18. The applicator may be fabricated using lithographic techniques. In this modification, block  101  is provided with a cover  102  on one side and a bottom  103  on the opposite side. Longitudinal channels  104  are etched into block  101  as are transverse panels  106  at either end, providing dividers  107  between the channels  104 . The sides of dividers  107  and the bottoms of longitudinal channels  104  are lined with sorbent, as in the previous modifications. At one end, a shelf  108  is formed. Applicator  111  comprises longitudinal members  112  and an end connector  113  or feed. The longitudinal members  112  fit into the spaces between the dividers  107 . Feed  113  rests on shelf  108  and exits block  101  through insulator  114 . Gas from evaporator  26  enters the channels  104  and  106  through opening  32   d  in block  101  and interacts with a sorbent. RF power is applied to grid  111  at the end of the absorbing portion of the cycle, causing the gas to split from the sorbent and exit block  101  through conduit  34   d  leading to condenser  31 . 
     In other respects, the modifications of FIGS. 7-8;  9 - 11 ;  12 - 14 ; and  15 - 19  resemble those shown in FIG.  1  and the same reference numerals followed by subscripts a, b, c and d, respectively, indicate corresponding parts. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.