Abstract:
A modular cooling system includes a positive displacement compressor and a microchannel heat exchanger for cooling a heat generating device such as a semiconductor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cooling system incorporating a gas compressor and a heat exchanger. In particular, heat absorbed by a gas provides a cooling effect. 
     2. Discussion of the Related Art 
     Heat transfer components and in particular heat exchangers have largely been designed for cooling large and/or mechanical items. Such systems have in recent years been adapted to other uses including cooling electronics devices. These adaptations generally have only specialized uses and fail to deliver the performance of systems designed from the start to solve a particular class of cooling problems. The present invention is directed to solving these and other problems associated with cooling items including small and/or non-mechanical items. 
     SUMMARY OF THE INVENTION 
     A modular cooling system comprises a compressor and a heat exchanger interconnected by conduits capable of transporting a compressed gas. An embodiment includes a positive displacement compressor for pressurizing a gas to a pressure of about 0.5 to 14 pounds-force per square inch gauge pressure (psig) where the compressor has a hub and the hub has an axis of rotation arranged eccentrically with respect to a compressor circumferential wall. Near its periphery, the hub is coupled to a plurality of blades, a plurality of which have substantially stationery blade roots and oscillating blade tips. A cooler incorporating a plurality of closed channels and physically coupled to an electronics device and a manifold and a plurality of inlets of closed channels are provided wherein the manifold supplies compressed gas from the compressor to the closed channel inlets. 
     Various embodiments include one or more of the following: a collector for collecting gas exhausted from the closed channels; a conduit for removing at least a portion of the connected gas from a conditioned building space enclosing the electronics device; a thermally conductive cooler path including fins forming a plurality of slots; a cover over the slots forms a plurality of closed channels; the manifold affixed to the thermally conductive path; the collector affixed to the thermally conductive path; a chamber bounded by a circumferential wall and first and second substantially parallel side walls; a hub at least partially within the chamber; a plurality of blades extending between the hub and an inner surface of the circumferential wall; the hub having an axis of rotation substantially normal to a side wall and eccentrically arranged with respect to the circumferential wall; a plurality of cavities, formed by opposed faces of adjacent blades, an outer hub surface between the roots of the adjacent wipers and an inner surface of the circumferential wall between seals the adjacent blades make with said inner surface; the volume of a cavity increasing during a first angular displacement of the hub for ingesting a fluid into the cavity via a first aperture in a side wall; the volume of the cavity decreasing during a second angular displacement of the hub for pressurizing said fluid; the fluid being exhausted from the cavity via a second aperture in a side wall during a third angular displacement of the hub; a plurality of channels having a dimension between opposed surfaces of between about 5 and 20 one-thousandths of an inch; blades that are root flexing blades; and, blades that are articulating action blades. For example, in an embodiment the shaft rotation is divided into two 180 degree segments, where the first segment is generally a segment in which the cavity volumes expand while the second segment is generally a segment in which cavity volumes contract. 
     Another embodiment includes a microprocessor in contact with a finned heat exchanger cooled by gas supplied by a positive displacement compressor having three or more variable volume chambers, each one of a plurality of the chambers bounded in part by adjacent compressor blades and each of said plurality of chambers defining a variable volume responsive to an angular position of a shaft coupled to the blades and eccentrically located within a compressor chamber wherein an outlet pressure of the compressor is responsive to the magnitude of a centrifugal force tending to move distal blade tips away from the shaft. 
     Various embodiments include one or more of the following: an air conditioned space enclosing the microprocessor; a conduit transferring substantially all of the gas heated by the heat exchanger to a space other than the air conditioned space; the gas compressor supplying gas to the heat exchanger at a pressure in the range of about 0.5 to 14 pounds force per square inch gauge pressure (psig); blades that are root flexing blades; and, blades that are articulating action blades. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described with reference to the accompanying figures. These figures, incorporated herein and forming part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art to make and use the invention. 
         FIG. 1A  is a schematic of a cooling system in accordance with the present invention. 
         FIG. 1B  is a schematic of an embodiment of the cooling system of  FIG. 1A . 
         FIG. 1C  is a schematic of an embodiment of the cooling system of  FIG. 1A . 
         FIG. 2A  is an exploded diagram of a first compressor for use with the cooling system of  FIG. 1A . 
         FIG. 2B  is a diagram of a first bladed hub of a compressor of the cooling system of  FIG. 1A . 
         FIG. 2C  is a diagram of a first bladed hub inserted in a circumferential wall of a compressor of the cooling system of  FIG. 1A . 
         FIG. 3A  is an exploded diagram of a second compressor for use with the cooling system of  FIG. 1A . 
         FIG. 3B  is a diagram of a second bladed hub of a compressor of the cooling system of  FIG. 1A . 
         FIG. 3C  is a diagram of a second bladed hub inserted in a circumferential wall of a compressor of the cooling system of  FIG. 1A . 
         FIGS. 3D-E  are diagrams of a bladed hub inserted in a circumferential wall of a compressor of the cooling system of  FIG. 1A . 
         FIGS. 4A-C  are diagrams of a first heat exchanger for use with the cooling system of  FIG. 1A . 
         FIGS. 5A-B  are diagrams of a second heat-exchanger for use with the cooling system of  FIG. 1A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The disclosure provided in the following pages describes examples of some embodiments of the invention. The designs, figures, and description are non-limiting examples of certain embodiments of the invention. For example, other embodiments of the disclosed systems and methods may or may not include the features described herein. Moreover, disclosed advantages and benefits may apply to only certain embodiments of the invention and should be not used to limit the disclosed inventions. 
       FIG. 1A  shows a cooling system in accordance with the present invention  100 A. A heat exchanger or cooler  118  has a heat exchanger surface  117  and an item to be cooled  116  has a surface  119 . Heat transfer from the item surface to the heat exchanger surface cools the item. In an embodiment, a path for conduction heat transfer exists between the item and heat exchanger surfaces. And, in an embodiment, the heat exchanger surface touches the item surface. In these and similar embodiments, heat transfer between the surfaces is primarily via conduction and the item to be cooled is cooled when heat is transferred from the item surface to the heat exchanger surface. 
     Heat is removed from the heat exchanger  118  primarily via convective heat transfer to a gas passing through the heat exchanger. The gas is supplied to the heat exchanger from a pressurized gas source  101  via a first tube, pipe, conduit or passage (“conduit”)  110 . A second conduit  120  contains gas leaving the heat exchanger. In some embodiments at least some of the gas leaving the heat exchanger is exhausted  122  to the surroundings  123  and in some of these cooling systems the surroundings are physically separated from a conditioned space enclosing the item to be cooled  112 . In some embodiments, all or portions of the pressurized gas source are remote from the item to be cooled. 
     In some embodiments, the gas mentioned above is air. However, in various embodiments other gasses with physical properties suited to the application, including thermal conductivity and vapor pressure, are used. As indicated by the application, other gasses to be considered include nitrogen, argon, carbon dioxide, helium and mixtures of two or more of these gasses. As such, references to gas herein should be understood to include air and other suitable gasses known to persons of ordinary skill in the art. 
       FIG. 1B  shows an embodiment  100 B of the cooling system of  FIG. 1A  including, among other things, gas flow control components. A chamber or manifold  132  receives gas  108  via a third conduit  124  from a gas pressurizing device  106 , such as a positive displacement compressor or a non-positive displacement compressor, for example a centrifugal compressor. The gas pressurizing device takes suction  104  from a gas supply  102 , such as the atmosphere in an open system and a gas return conduit in a closed system. 
     In various embodiments, selected gas flows from the manifold are controlled by valve(s)  130 . In an embodiment, a flow to a heat exchanger  139  is controlled by a valve  130  supplied by a fourth conduit  134  leading from the manifold and exhausting to a fifth conduit  135  leading to the heat exchanger  118 . Suitable valves include manual valves and valves capable of being automatically operated such as solenoid, servo-operated valves and piezoelectric valves. In some embodiments a second flow supplied from the manifold  141  is controlled by a valve  130  interposed between a sixth conduit  138  leading from the manifold and a seventh conduit  140  leading to a second device to be cooled  142  which has a second device gas exhaust  145 . And, in some embodiments, a third flow supplied from the manifold  143  via a seventh conduit  144  interconnecting the manifold and a third device to be cooled  146  has a third device gas exhaust  147 . 
       FIG. 1C  shows an embodiment  100 C of the cooling system of  FIG. 1B  including, among other things, a controller for automating flow control. Here, a controller such as a digital controller, analog controller or analog and digital hybrid controller  148  receives one or more temperature signals  160 . In various embodiments, the controller transmits one or more signals to control valves  130  via valve signal lines  156 ,  158  and to the gas compressor via compressor signal line(s)  154 . Temperatures sensed provide control feedback such as feedback to control cooling gas flowrate  108  and to indicate unsafe operating conditions. In various embodiments, temperature sensors used include a heat exchanger exhaust temperature sensor  163  and an item temperature sensor  161 . Among other things, such sensors and controllers enable response to near instantaneous, past and/or predicted temperature measurements to vary item cooling rates. For example, gas flow to the manifold  108  may be controlled by controlling shaft speed of a gas supply compressor  106 . And, for example, gas flow through control valves  130  may be controlled by controlling respective valve actuators. 
     For controlling gas flow to limit temperature excursions of the device to be cooled, temperature measurements for feedback controls should be made at suitable locations and in particular at locations indicating the temperature of the device to be cooled. These may be direct measurements of the temperature of the device itself, such as measurements made with an embedded thermocouple or thermistor  161 . Also suited to this purpose are indirect measurements, for example a measurement made of the temperature of the gas leaving the heat exchanger  163 . 
     In an embodiment, first signal line  162  interconnects a temperature measuring device contacting or embedded in the device to be cooled  161  with the controller  148  via an optional signal conditioning module  152  such as that used in the temperature measuring circuit of fan speed controls associated with a modern microprocessor application. And in some embodiments a second signal line  164  interconnects a temperature measuring device indicating the temperature of gas leaving the heat exchanger with the controller  148  via the optional signal conditioning module  152 . 
     In an embodiment, the gas pressurization device  106  is a compressor utilizing blades coupled to a rotatable shaft, the centerline of the shaft being in eccentric relationship with a circumferential boundary of a compressor chamber enclosing the blades. In some embodiments, the blades interact with a blade hub driven by the rotatable shaft and the blade-hub interaction is substantially characterized by resilient blade flexure near a blade-hub interface (“root flexing blades”). In other embodiments, the blades interact with a blade hub driven by the rotatable shaft and the blade-hub interaction is more substantially characterized by an articulating action near a blade-hub interface (“root articulating blades”). For some root flexing embodiments and for some articulating action embodiments, a plurality of blades have substantially stationery blade roots and blade tips that oscillate, cyclically moving toward and away from respective blade roots. 
     In an embodiment, the gas pressurization device  106  is a positive displacement compressor utilizing root flexing blades that are integral with and/or in resilient relationship with a hub.  FIG. 2A  shows such a flexing blade compressor  200 A. 
     In the flexing blade compressor, a hub  201  with three or more fixed blades  212 , such as a bladed hub formed by adhering multiple parts, extrusion, casting or machining a monolithic piece of stock material, is substantially enclosed by compressor chamber walls including a circumferential wall  210  interposed between first  206  and second  208  side walls. A prime mover such as an electric motor  202  powered by an electricity source  204  is mechanically coupled to the hub  201  such that rotation of a shaft  203  of the motor causes the hub to rotate, operating the compressor. Some embodiments incorporate a gas or air filter  209  such as a filter including a filter frame  211  holding a filter media  213 , the frame for insertion in a filter rack  215  of a sidewall such as the second sidewall and the frame extending over an inlet aperture  216 . 
       FIG. 2B  shows an embodiment of a flexible blade compressor&#39;s bladed hub  200 B.  FIG. 2C  shows a bladed hub inserted in a flexible blade compressor circumferential wall  200 C. 
     The blades extend from the hub at respective blade roots  214  and each blade forms a root angle Θ 1  between a radial root line  247  projected from the hub&#39;s axis of rotation  220  through the root  214  and a line tangent to the blade near the blade root  251 . Similarly, radial seal and tip lines  253 ,  255  are formed by radial lines projected from the hub&#39;s axis of rotation through blade seals  248  and tips  249  respectively defining an angle φ. 
     In various embodiments, installation of the bladed hub  200 B into the compressor chamber causes further bending of a plurality of blades  212  increasing the related angles Θ 1 . Here, the blade tip  249  trails, with respect to the hub&#39;s  201  direction of rotation  213 , the projection of the root line on the inner surface of the circumferential wall  245 . And, in some embodiments, small clearances discussed further below result in the end of the tip line  249  trailing, with respect to the direction of hub rotation, the end of the seal line  248 . In particular, smaller clearances correspond in these embodiments to increases in the magnitude of the angle φ. 
     The hub&#39;s rotational axis  220  is substantially normal to a side wall and eccentrically arranged with respect to an inner surface of the circumferential wall  240  such that 1) the shortest distance or clearance  244  between a point on the periphery of the hub  242  and the circumferential wall inner surface  243  varies as the hub rotates and 2) during a complete revolution of the hub the shortest distance establishes both minimum and maximum clearances. 
     The blades have a length l 1  that is greater than the maximum clearance mentioned above and extend between the hub  201  and an inner surface of the circumferential wall  240  forming a plurality of cavities  250 . Each cavity is defined by 1) opposed faces of adjacent blades  252 , 2) a hub surface extending between the roots of the adjacent blades  256  and 3) an inner surface of the circumferential wall extending between seals the adjacent blades make with the circumferential wall inner surface  254 . Cavity volumes are substantially equal to their cross-sectional area multiplied by a depth substantially equal to the width or an average width w 1  of a blade. 
     For a particular cavity, rotation of the hub varies cavity volume from a maximum value  250  to a minimum value  246  and so the volume of the gas within the cavity. As indicated here, a blade flexes (i.e., θ 1  increases) as it encounters smaller clearances. And, in some embodiments, the region of a blade contacting the inner surface eventually moves away from the blade tip  249  toward the blade root  214  due to curling of the blade(s) forming the smallest cavity(s). For example, during a one angular displacement of the hub  201 , a particular cavity&#39;s volume expands; during another angular displacement of the hub the cavity&#39;s volume contracts. And, as described more fully below, during different and/or overlapping angular displacements gas is drawn into and expelled from the cavity. 
     Gas inlet and outlet structures are formed in parts of the compressor chamber. In one embodiment at least one such structure is formed in the circumferential wall. (See for example the description of FIGS.  3 D,E). In another embodiment, at least one such structure is formed in a side wall. In the embodiment of  FIG. 2A , an inlet structure  217  formed in a side wall  208  defines a aperture  216  allowing expanding chambers in fluid communication with the inlet structure to ingest a gas. In some embodiments, the aperture is slot-like in shape. Similarly, an outlet structure  214  formed in a side wall  208  includes an outlet nozzle  218  such that contracting chambers in fluid communication with the outlet structure expel a gas through the outlet nozzle. 
     In various embodiments, the compressor chamber parts and bladed hub are made of polymers, metals and combinations of the two. In some embodiments, the integral bladed hub is made of HDPE or a similar polymer. And, in some embodiments, the bladed hub is made of a material resistant to flexural fatigue such as a fatigue resistant polymer; for example, a thermoplastic polyester elastomer (TPE-E), Arnitel® offers resistance to flexural fatigue over a wide range of temperature conditions. 
     In an embodiment, the gas pressurization device  106  is a positive displacement compressor utilizing root articulating blades that are not integral with a hub and that do not substantially flex at respective blade roots during compressor operation.  FIG. 3A  shows such an articulating blade compressor  300 A. 
     In the pivoting blade compressor, a hub  301  is fitted with three or more articulated blades  312  to form a bladed hub. The bladed hub is substantially enclosed by compressor chamber walls including a circumferential wall  310  interposed between first  306  and second  308  side walls. A prime mover such as an electric motor  302  powered by an electricity source  304  is mechanically coupled to the hub such that rotation of a shaft of the motor  303  causes the hub to rotate, operating the compressor. 
       FIG. 3B  shows an embodiment of a pivoting blade hub  300 B. The blades extend from the hub at respective blade roots  314 . In various embodiments, a point of articulation moves along the length of the blade. In the embodiment shown, the point of articulation is at the blade root. In some embodiments, the point of articulation functions as a pinned connection such as a hinge. In particular, a semicircular setting  341  receives a matching circular insert that is at the proximate end of a blade  343 . In various embodiments, ball-socket, hinge, pinned and other suitable joints including combinations of any of these couple blades to the hub are used. 
       FIG. 3C  shows a pivoting blade hub inserted in a compressor circumferential wall  300 C. When a blade&#39;s tip  349  contacts the inner surface of the circumferential wall  354 , the blade  312  extends from a respective blade root forming an angle Θ 2  between a line tangent to the blade near the blade root  351  and a radial root line passing through the root and the hub axis  361 . Similarly, coincident radial seal and tip lines  365  are formed by radial lines projected from the hub&#39;s axis of rotation  320  through blade seals and tips  349  respectively. In an embodiment of the articulating blade compressor, the tip and seal lines are not substantially collocated. 
     In various embodiments, when the bladed hub  301  is inserted in a compressor circumferential wall  300 C and the blade tips  349  contact the inner surface of the circumferential wall  354 , the blade tips  349  trail, with respect to the hub&#39;s  301  direction of rotation  339 , the projection of the root lines on the inner surface of the circumferential wall  363 . 
     The hub&#39;s rotational axis  320  is substantially normal to a side wall and eccentrically arranged with respect to an inner surface of the circumferential wall  340  such that 1) the shortest distance or clearance  344  between a blade root  314  and the circumferential wall inner surface  354  varies as the hub  301  rotates and 2) during a complete revolution of the hub the shortest distance establishes both minimum and maximum clearances. 
     The blades have a length l 2  that is greater than the maximum clearance mentioned above and extend between the hub and an inner surface of the circumferential wall forming a plurality of cavities, for example  346 ,  350 . Each cavity is defined by 1) opposed faces of adjacent blades  352 , 2) a hub surface extending between the roots of the adjacent blades  356  and 3) an inner surface of the circumferential wall extending between seals the adjacent blades make with the circumferential wall inner surface  354 . Cavity volumes are substantially equal to their cross-sectional area multiplied by a depth equal to the width or an average width w 2  of a blade. 
     For a particular cavity, rotation of the hub varies cavity volume from a maximum value  350  to a minimum value  346  and so the volume of the gas within the cavity. As indicated here, a blade articulates (i.e., Θ 2  increases) as it encounters smaller clearances. For example, during one angular displacement of the hub, a particular cavity&#39;s volume expands; and, during another angular displacement of the hub that cavity&#39;s volume contracts. And, during different and/or overlapping angular displacements gas is drawn into and expelled from the cavity. 
     Gas inlet and outlet structures are formed in parts of the compressor chamber. In one embodiment at least one such structure is formed in the circumferential wall. See for example, the embodiment  300 D,  300 E of  FIGS. 3D-E  showing a circumferential wall  210  having a circumferential inlet  378  with inlet flows  374  and a circumferential outlet  380  having outlet flows  376  exhausting from an outlet nozzle  372 . In another embodiment, at least one such structure is formed in a side wall. For example, in  FIG. 3A  an inlet structure  317  formed in a side wall  308  defies an aperture  316  allowing expanding chambers in fluid communication with the inlet structure to ingest a gas. In some embodiments, the aperture is slot-like in shape. Similarly, an outlet structure  314  formed in a side wall  308  includes an outlet nozzle  318  such that contracting chambers in fluid communication with the outlet structure expel a gas exiting through the outlet nozzle. 
     In various embodiments, the compressor chamber parts, blades and hub are made of polymers, metals and/or combinations of the two. In some embodiments, the hub and blades are made of HDPE or a similar polymer. And, in some embodiments, the blades are made from a metal such as stainless steel while the blade&#39;s proximate and distal (connecting and sealing) ends are polymers attached to the blade ends. 
     Various types of heat exchangers may be cooled by gas supplied by the compressor  106 . Such heat exchangers include single and multi-flow heat exchangers, primary surface heat exchangers, finned heat exchangers and other heat exchangers suitable for use with the present invention as are know to persons of ordinary skill in the art. 
     In an embodiment, an opposed flow heat exchanger  400 A shown in  FIG. 4A  cools the item to be cooled  116 . In some embodiments, the item to be cooled is a semiconductor device such as a microprocessor. The heat exchanger includes a gas inlet tube  402 , a finned base  406 ,  408  and at least one sealing wall  404 . 
       FIG. 4B  shows the finned base  400 B including fins  408  extending from an interface structure  406  in a heat conduction path between the item to be cooled  116  and the fins  408 . In some embodiments, a block of material suitable for conducting heat, such as a block of aluminum, is worked by sawing, wire EDM, laser cutting, grinding or another suitable method to form the fins. In other embodiments, a finned interface structure may be formed in a molding process. And, in still other embodiments, a plurality of separate fins are joined to the base using one or more methods known in the art such as glues, adhesives and molten materials such as molten metal including new metal and no new metal processes such as soldering and spot welding respectively. 
     As shown in  FIG. 4C  the inlet tube  402  abuts two sealing wall portions  424 ,  426  to form a cover plate  400 C. When placed over the fins  408 , the cover plate closes the otherwise open channels  417  between the fins such that multiple gas paths are formed between the fins  419 . 
     An inlet channel cutting across the fins  412  provides an entry point for gas  405  leaving a region of the inlet tube  402  where a portion of the tube wall is cut-away to form a gas outlet slot  423 . This slot is bounded by opposed inlet tube rim portions  422  arranged for sealing with peripheral portions of the inlet channel  421 . One or two gas flows  405 ,  407  supply gas to the heat exchanger and opposed gas flows exiting the heat exchanger  411 ,  413  through fin channels to either side of the inlet tube  414 ,  416 . In various embodiments, a cap  409  is used to block either end of the inlet tube where a single gas flow will be used. 
     To enhance convective heat transfer, a gap “z” between adjacent fins is chosen to disturb the boundary layer commonly found in fluid systems and to thereby improve the convective heat transfer coefficient. The inventor has performed experiments and found that gaps less than about 50/1000&#39;s of an inch are preferred and that gaps between about 5 and 20/1000&#39;s of an inch are more preferred. 
     In an embodiment, a unidirectional flow heat exchanger  500 A shown in  FIG. 5A  cools the item to be cooled  116 . The heat exchanger includes a gas inlet tube  502   a , a gas outlet tube  502   b , a finned base  506 ,  508  and a sealing wall  504 . 
       FIG. 5B  shows the finned base  500 B including fins  508  extending from an interface structure  506  in a heat conduction path between the item to be cooled  116  and the fins  508 . In some embodiments, a block of material suitable for conducting heat, such as a block of aluminum, is worked by sawing, wire EDM, laser cutting, grinding or another suitable method to form the fins. In other embodiments, a finned interface structure may be formed in a molding process. And, in still other embodiments, a plurality of separate fins are joined to the base using one or more methods known in the art such as glues, adhesives and molten materials such as molten metal including new metal and no new metal processes such as soldering and spot welding respectively. 
     Inlet tube  502   a  and outlet tube  502   b  abut opposed edges of the sealing wall  504  such that the tube and wall assembly, when placed over the fins  508  closes the otherwise open channels  517  between the fins. Multiple gas paths are thereby formed between the fins  519 . 
     Opposed edges of the heat exchanger are an inlet and outlet respectively of the gas paths  540 ,  542 . The inlet  540  provides an entry for gas  511  leaving a region of the inlet tube  502   a  where a portion of the tube wall is cut-away to form a gas outlet slot  523   a . This slot is bounded by opposed inlet tube rim portions  522   a  arranged for sealing with peripheral portions of the heat exchanger  521   a.    
     The outlet  542  provides an outlet for gas  513  leaving a region of the outlet tube  502   b  where a portion of the tube wall is cut-away to form a gas outlet slot  523   b . This slot is bounded by opposed outlet tube rim portions  522   b  arranged for sealing with peripheral portions of the heat exchanger  521   b.    
     One or two gas flows supply gas to the heat exchanger via the inlet tube  550 ,  552  and one or two gas flows carry gas away from the heat exchanger via the outlet tube  554 ,  556 . In various embodiments, one or more caps  409  are used to block either end inlet and/or outlet tubes where a single gas flow will be used. 
     To enhance convective heat transfer, a gap “z” between adjacent fins is chosen to disturb the boundary layer commonly found in fluid systems and to thereby improve the convective heat transfer coefficient. The inventor has performed experiments and found that gaps less than 50/1000&#39;s of an inch are preferred and that gaps between 5 and 20/1000&#39;s of an inch are more preferred. 
     During cooling system operation, a gas compressor  106  pressurizes a gas  108  and a gas conveying system  110  delivers the compressed gas to a heat exchanger  118  thermally coupled to an item to be cooled  116 . The gas absorbs heat as it passes through the heat exchanger. In some embodiments, heated gas is reused after it is cooled. In other embodiments, the heated gas is discharged to one or more of a) the environment as it leaves the heat exchanger, b) a location outside an enclosure housing the item to be cooled, c) a location outside a conditioned space containing the item to be cooled, or d) to another suitable location. 
     During compressor operation, blades  212 ,  312  are rotated inside a compressor chamber  206 - 210 - 208 ,  306 - 310 - 308  when a rotatable shaft coupled to the blades is turned  203 ,  303 . Because the centerline of the shaft  220 ,  320  is eccentrically mounted with respect to a compressor chamber circumferential wall  210 ,  310  the blade tips  212 ,  312  seal against, rotation of the shaft causes the orientation of the blades with respect to the hub to change. In various embodiments of the flexible blade compressor, the blades flex near the blade root  214  and in various embodiments of the articulating blade compressor the blades pivot, largely without flexure, near the blade root  314 . 
     Cavities  250 ,  350  formed between adjacent blades expand and contract during compressor operation, the expansion of a cavity indicating a time during which gas is drawn into the compressor and contraction of a cavity indicating a time during which gas is expelled from the compressor. In some embodiments, apertures in the sidewalls serve as compressor inlet and exhaust ports  216 - 218 ,  316 - 318 . In other embodiments apertures in the compressor chamber circumferential wall  378 ,  380  serve as compressor inlet and exhaust. In yet other embodiments, both side wall and circumferential wall ports are used. 
     In various compressor embodiments, the blade tip seal with a mating portion of a circumferential wall  248 ,  349  is enhanced by centrifugal force which “throws” the blade  212 ,  312  against the wall with increasing force as the shaft speed increases. In some embodiments, the blade is weighted to increase this effect and thereby increase the compressor&#39;s output pressure capabilities. For example, a blade may be preferentially weighted toward its tip and relatively lightweight elsewhere to manage the centrifugal forces the blades exert on the hub and hub coupling while maintaining an adequate tip seal for the compressor&#39;s design outlet pressure. 
     During heat exchanger  118  operation, compressed gas  110  enters the heat exchanger and flows through a plurality of passages or channels. In some embodiments a plurality of channels each have small gaps z between opposed surfaces for the purpose of disturbing a boundary layer and enhancing convective heat transfer. Heat exchangers of the present invention are useful in various embodiments for cooling items to be cooled  116  including microprocessors and other electronic devices. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to those skilled in the art that various changes in the form and details can be made without departing from the spirit and scope of the invention. As such, the breadth and scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and equivalents thereof.