JP6078054B2 - Heat transfer device with reduced height - Google Patents

Description

1. FIELD OF THE INVENTION The present invention relates to at least one evaporator, at least one condenser, and one or more fluids that connect the evaporator and the condenser for use in indirectly cooling an object with a cooling fluid. Heat transfer device, such as a closed loop fluid cooling system, having a conduit, and more particularly reduced heat transfer that directs the cooling fluid into indirect thermal contact with an object to be cooled in a compact environment Relating to the device.

2. Description of Related Art A passive closed-loop two-phase fluid cooling system is a well-known heat transfer device used to cool objects that generate excessive heat, such as, without limitation, computer chips. The term passive is intended to mean a system that does not use any mechanized pump to circulate the cooling fluid. The purpose of circulating the fluid in the passive system stems from fluid buoyancy changes and phase changes when heat is applied. The evaporator is usually placed in thermal contact with the object to be cooled, and the liquid form of the cooling fluid passes through a surface that separates the liquid from the actual object to be cooled. In this way, heat can be transferred between the fluid and the object without the fluid being in direct contact with the object. By applying heat to the fluid, at least a portion of the fluid is vaporized. The gas is then carried to the condenser. Heat is released as the gas recondenses to a liquid state. The condensed liquid is returned to the evaporator and this vaporization-condensation cycle is repeated. FIG. 1a shows such a prior art condenser 100, and FIG. 1b shows its details. Prior art condensers typically provide a condensing surface using a circular cross-section tube 102 or a flat tube approximating an elliptical or rectangular cross section. These tubes are usually arranged with their longitudinal axes perpendicular. A plurality of cooling fins 104 with openings sized to fit the outer peripheries of these tubes are arranged horizontally. In the prior art condenser 100 of FIG. 1, the condenser tubes are interspersed between the air cooling fins 104 so that the air cooling fins and condenser tubes are above the liquid header tank 106 and below the gas header tank 108. Occupies the same vertical area. A gas conduit 110 directs the heated gas to the gas header tank 108 and a condensate return line 112 returns the condensate 114 to the reservoir 116.

  Thus, this prior art configuration requires that all of the air cooling fins 104 be located above the collection point for the condensed fluid (condensate 114), particularly above the liquid header tank 106. This is the only maximum limitation of prior art condensers. This limitation of prior art condensers can best be illustrated by comparing FIG. 1 to FIG. 2, which illustrates the present invention. In FIG. 2, it can be seen that the air cooling fins 118 are located above and below the region of the condenser chamber. FIG. 2 shows both air cooling fins 118 above and below the region of the condenser chamber 120, but it is understood that the air cooling fins 118 can be located either above or below the condenser chamber 120. It should be. There are no interspersed condenser fins (inside the condenser 120, not shown in FIG. 2) between the air cooling fins 118. This means that the condenser fins do not have to be spaced apart horizontally from each other as in the prior art design because the condenser fins do not need to pass cooling air between them. This further means that the condenser fins of the present invention are shorter along their vertical axis than prior art designs, but they can use more fins due to their closer horizontal spacing. This means that a total condensate surface area substantially equal to the prior art design is possible. The present invention can be similarly configured to provide a total air cooling fin area that is substantially equal to prior art designs. An important advantage of the present invention is that the collection point for the condensed fluid (condensate 114) is substantially higher than that of the prior art design. This important advantage of the present invention, namely that the condensate surface area and the collection point for condensate can be positioned higher in the available space and well above the height of the evaporator component, is the embodiment of FIG. Is the most obvious. Referring again to FIG. 1, the difference between the liquid height (RH) in the reservoir and the fluid height (CH) in the condenser is the gravity height (GH), sometimes called gravity head. . As shown, GH-2 in FIG. 2 is substantially larger than GH-1 in FIG. The ability of each design to return condensate from the condenser to the reservoir is directly linked to their respective gravity heights GH-1 and GH-2. For a given available height (AH), if both the prior art design and the present invention can be configured such that the air cooling fin area and the internal condenser surface area are substantially equal, The invention can operate at higher heat loads because its GH is higher. This is because the mass transport rate of condensate return is directly related to the maximum amount of heat transfer that can be achieved.

  To further illustrate the advantages of the present invention compared to the prior art design, reference is again made to FIG. FIG. 3 shows a prior art type design configured to provide the same weight height (GH-2) as the present invention. As shown in FIG. 3, this configuration substantially reduces the vertical space for the air cooling fins and the condenser tube because there is an area 122 that cannot be used below the condenser. This configuration is inferior to the present invention due to the reduced air cooling fin area and condenser tube area.

  For the reasons described above, the present invention provides a higher heat load in applications that require a relatively low available height (AH), i.e., a "thin" design, compared to condensers of prior art designs. Can be transmitted.

  There are examples of prior art condensers that have been redirected to achieve low thickness, but these typically achieve low thickness at the expense of another significant design consideration.

  For example, US Pat. No. 7,422,052 discloses a thin cooling system with condenser components arranged substantially horizontally. The condenser is generally similar to a vertical or upright condenser according to the prior art, except that it is angled to be closer to the horizontal plane while still being shallowly inclined. This provides the benefit of decreasing height at the expense of substantially increasing width.

US Pat. No. 7,231,961 also discloses a thin cooling system. This reference specifies the condenser as “a long chamber with a narrow internal channel”. The chamber is oriented so that its “long” dimension is oriented substantially parallel to the horizontal plane, the horizontal plane being the surface on which the device to be cooled is mounted, eg, the circuit board that supports the cooled chip / processor Is taken to mean One side of the chamber (substantially vertical outer surface) is filled with air cooling fins. Based on the listed dimension ranges that define the length, width and height of this chamber, the chamber is simply a single, very similar to many of the condenser tubes described above with respect to prior art condensers. It can be described as a condenser tube. In this case, the single condenser tube is arranged with its longitudinal axis horizontal rather than vertical. Therefore, this design achieves vertical thinness simply by placing the condenser tubes in a horizontal configuration. This is obviously done at the expense of gravity. This limit is explicitly listed in the fifth row, lines 12-19.
“Typically, the thermosyphon condenser is placed on top of or above the evaporator to force the liquid from the condenser to the evaporator using gravity. This is not possible in spaces where the available height is severely limited, part of the condenser can be higher than the evaporator or vice versa, but the condenser and evaporator are They are approximately horizontal to each other. "

  It should also be suggested that in this prior art design, a significant portion of the internal volume of the condenser needs to be occupied by non-flowing liquid.

  This represents a well-known limit to condenser performance in that condensation cannot occur on a condenser surface embedded in a non-flowing liquid, a situation often referred to as “condenser flooding” .

  Thus, although condensers are generally well known and widely used, there continues to be a need to make condensers more efficient, and therefore more competitive, cost effective and useful. . In particular, it provides a condenser that can be used to cool an object in a very compact environment while providing a suitable internal condenser surface area combined with a suitable gravity height for condensate transfer. It is useful.

  Accordingly, it is an object of the present invention to provide a heat transfer device that enables efficient and effective cooling of objects that may tend to overheat, such as computer chips.

  It is a further object of the present invention to provide an improved heat transfer device with reduced height for use in applications where vertical clearance or top margin is limited.

  In accordance with these and other objects of the present invention, a heat transfer device is provided comprising a chamber having substantially vertical condenser fins that condense heated heat transfer fluid from gas to liquid. The chamber has an inlet for receiving gas and an outlet for returning condensed fluid in its liquid state to the reservoir. Both the inlet and outlet are located at a height higher than the height of the liquid heat transfer fluid in the reservoir. Vertical condenser fins that provide a condensing surface are substantially disposed in the vertical space between the inlet and the outlet. The advantage of this arrangement is that the condensate returns to the evaporator by gravity, leaving a wider portion of the available vertical height. This arrangement also applies the liquid in the liquid return line without the negative consequence of pushing liquid into the condenser component (if it occurs, any part of the condenser becomes inoperable). A significant change in height is possible. With this structure, the device can achieve excellent condensation performance and have an overall reduced height. Furthermore, this structure allows the device to have an overall reduced height where the chamber depth is greater than the interior height of the chamber.

  In a preferred embodiment of the present invention, the condenser fins in the chamber can have grooves in their surface to increase the effective cooling surface in the chamber. The grooves can be arranged in matched opposing pairs on either side of the fin as a design choice, or can be alternately staggered on both sides. A plurality of air cooling fins in thermal communication with the chamber are attached to one or more of the outer surfaces of the chamber, as typically applied to the cooling of electrical or electronic equipment. The surface employed is most typically the top surface or the bottom surface. Most commonly, multiple fins (sometimes referred to as an array of fins) are employed, although single fins can be used as well. Air passes through one or more air cooling fins by natural convection means or by forced convection means. The design, manufacture and adoption of air cooling fins used for natural or forced convection cooling is well known in the art of cooling system design. Instead of using one or more air cooling fins, a liquid cooling plate can be placed on either or both the top or bottom of the chamber. When used in this manner, the cold plate is secured to the chamber so as to be in thermal communication with the chamber. A cooling fluid circulates in the cold plate. The cooling provided by the cooling fluid condenses the gas inside the chamber. The term “liquid cooling plate” is synonymous with “liquid cooling heat sink” and both terms are well known in the art. An example of a liquid cooled heat sink is disclosed in US Pat. No. 5,829,516, which is incorporated herein by reference.

  Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. However, the drawings are designed for illustrative purposes only and are not designed to define the scope of the present invention, and the scope of the present invention should be referred to the appended claims. Should be understood. It should be further understood that the drawings are not necessarily drawn to scale and unless otherwise indicated, the drawings are merely intended to conceptually illustrate the structures and procedures described herein. It is.

  In order to further illustrate the present invention, reference is made to the exemplary embodiments shown in the drawings in which like numerals refer to like parts.

It is the schematic of the heat transfer apparatus by a prior art. It is the schematic of the heat transfer apparatus by a prior art. 1 is a schematic view of a heat transfer device according to the present invention. 1 is a schematic view of a heat transfer device according to the present invention. 1 is a schematic diagram of a prior art heat transfer device, wherein the condenser is configured to be higher than the surface on which the evaporator is located. 1 is a schematic diagram of a prior art heat transfer device, wherein the condenser is configured to be higher than the surface on which the evaporator is located. 1 is a schematic diagram of a preferred embodiment of a heat transfer device according to the present invention configured to operate in a vertical thin application. FIG. 1 is a schematic diagram of a preferred embodiment of a heat transfer device according to the present invention configured to operate in a vertical thin application. FIG. 1 is a schematic view of a chamber used in a first embodiment of a heat transfer device according to the present invention. FIG. 3 is a schematic view of a second embodiment of a chamber used in the heat transfer device according to the present invention. FIG. 4 is a schematic view of a third embodiment of a chamber used in the heat transfer device according to the present invention. FIG. 5 is a perspective view of the heat transfer device of FIG. 4 showing a plurality of air-cooled fins attached to the bottom of the condenser chamber, with arrows indicating cooling air across the air-cooled fins. FIG. 5 is a perspective view of the condenser component of the heat transfer device of FIG. 4 with a cutaway view at the top of the chamber so that the internal structure can be seen. FIG. 3 is a cross-sectional view of different embodiments of fins and grooves used in a heat transfer device according to the present invention. FIG. 3 is a cross-sectional view of different embodiments of fins and grooves used in a heat transfer device according to the present invention. 1 is a schematic cross section of a single tube embodiment of a heat transfer device according to the present invention. FIG. 6 is a perspective view of a further embodiment of a heat transfer device according to the present invention in which a liquid cooling heat sink, also known as a liquid cooling plate, is placed in thermal communication with the lower outer surface of the condenser chamber, with arrows pointing to the liquid cooling plate. Shows cooling fluid entering and exiting. FIG. 3 is a schematic view of a preferred embodiment of the present invention further comprising a septum attached to the circuit board and separating the area of the circuit board from the area of the condenser component. FIG. 3 is a schematic view of a preferred embodiment of the present invention further comprising a septum attached to the circuit board and separating the area of the circuit board from the area of the condenser component. FIG. 3 is a schematic view of a preferred embodiment of the present invention further comprising a septum attached to the circuit board and separating the area of the circuit board from the area of the condenser component. The condenser of the heat transfer device according to the invention, in which the condenser chamber is shown in cross-section, and the condenser chamber is located in the vertical region B completely above the vertical region A in which one array of air cooling fins is located It is the schematic of a component. Condensation of the heat transfer device according to the invention in which the condenser chamber is shown in cross-section and the condenser chamber is located in a vertical region B substantially above the vertical region A in which one array of air cooling fins is located It is the schematic of a vessel component.

  According to a preferred embodiment of the present invention, generally indicated at 10 in FIG. 4, a heat transfer device or “closed loop fluid cooling system” according to the present invention is shown. The heat transfer device 10 includes a reservoir 12 acting as an evaporator that holds the heat transfer fluid 14 and a first conduit that directs the heat transfer fluid 14 out of the reservoir 12 when the heat transfer fluid is in a gaseous state. 16 and a second conduit 18 that directs the heat transfer fluid 14 back to the reservoir 12 when the heat transfer fluid 14 is condensed from its gaseous state to a liquid state. The maximum height at which the liquid portion of the heat transfer fluid can rise before overflowing the condensing surface is denoted as h in FIG.

  In a preferred embodiment, the heat transfer fluid 14 is water or deionized water. If the design imposes certain requirements on the cooling fluid, such as freeze resistance, corrosion resistance or non-conductive cooling fluid, an organic cooling fluid such as alcohol, a refrigerant such as R134A, or 3M Fluorinert or Novec Liquids, etc. Any engineered fluid can be used.

  The heat transfer device 10 also includes a chamber 20 that acts as a condenser, which has an inlet 22 (FIG. 7) coupled to the first conduit 16 and an outlet 24 coupled to the second conduit 18. doing. In a preferred embodiment, the chamber 20 is hermetic and is made of a metal such as aluminum or copper.

  FIGS. 5 and 8 illustrate one of a plurality of substantially vertical condenser fins 26 that are disposed within the chamber 20 and the heat transfer fluid 14 is introduced into the chamber 20. A cooling surface is provided to condense from its gaseous state at the time to its liquid state for return to the reservoir 12. The fins 26 are spaced from each other to form a passage therebetween, through which the heat transfer fluid 14 flows and can contact a greater portion of the surface of the cooling fin 26. A first open header space 32 (FIGS. 5 and 6a) is provided at the top of the chamber 20 to facilitate dispersion along all passages of the gas. The first open header space 32 extends substantially across the entire width of the chamber 20 so that the gaseous heat transfer fluid 14 flows uninterrupted along the passageway to the full depth of the chamber 20 along the entire width of the chamber 20. (Depth, width and height orientations are shown in FIG. 8). By allowing the gas to disperse smoothly to a total depth and width of 20, the maximum cooling surface area of the cooling fins 26 is most efficiently exposed.

  A second open header space 34 is provided to facilitate the return flow of heat transfer fluid 14 to the reservoir 12. The second open header space extends substantially across the entire width of the chamber 20 and leads to the outlet 24. In the preferred embodiment of the present invention, two open header spaces are provided, but as a design choice, a single continuous header space (shown as 33 in FIG. 6b) can be used, This is because the high concentration of condensate (compared to gas) causes the condensate to naturally collect in the lower part, leaving the upper part of the single header space available for gas.

  The inlet 22 can be located at the top of the chamber 20 as shown in FIGS. 5 and 6b or at the side of the chamber 20 as shown in FIG. 6a. In any configuration, the gas of the heat transfer fluid 14 enters the first header space 32 and condenses in the fins 26 as described above. The choice of configuration is merely a design choice and depends on the requirements of the application, and the selection of the appropriate position with respect to the inlet 22 is well within the skill of a person skilled in the art.

  The structural arrangement of the present invention allows all of the condensing surfaces to be placed gravitationally above the liquid level in both the reservoir and the liquid return conduit. This structure provides the further advantage that the condensing surfaces, together with the chambers that house them, occupy a relatively small part of the vertical height available for the entire heat transfer device.

  FIG. 7 shows an embodiment of the invention in which air-cooled fins 30 'are attached to the bottom outer surface of the condenser chamber. Alternatively, instead of air-cooled fins, a liquid-cooled cold plate 30 as shown in FIG. 11 or any other known method for providing cooling to a condenser can be used.

  A further possibility to improve the performance of the heat transfer device 10 is to provide a groove 40 in the fin 26, as shown in FIGS. 9a and 9b. The grooves 40 can be arranged as matched pairs on either side of the fin 26 (FIG. 9a) or in a staggered arrangement as shown in FIG. 9b as a design choice.

  As a design choice, it is possible to embody the benefits provided by the present invention by using a single port 36 as both an inlet and outlet as shown in FIG. In the single port 36, the gas 42 can flow upward, while the liquid 44 can flow downward.

  In another embodiment of the invention shown in FIG. 12, the heat transfer device 40 is attached to a circuit board along with a cooled microprocessor. A circuit board having an electrical connector 42 disposed near one of the peripheries can be inserted into another structure, such as a slot in the computer chassis. The heat transfer device 40 supports an electrical connector 46 sized to mate with the electrical connector 42 on the circuit board, along with a liquid cooling plate 44 that provides cooling means for the condenser 20. When so arranged, when the circuit board is inserted into the chassis, the electrical connectors 42, 46 fit together and the condenser 20 fits with the liquid cooling plate 44. The fit between the condenser 20 and the liquid cooling plate 44 must provide good thermal communication between the two components in order to efficiently transfer heat, for this reason thermal grease or An interface material 48 or thermal interface pad that facilitates heat transfer, such as a gel, is disposed between the mating surfaces. In a typical implementation, a solid / non-grease interface material, such as a graphite-based pad, is permanently secured to the face of one component by an adhesive. The adhesive free surface is in contact with the other component. This allows the two components to be repeatedly assembled or “fitted” and disassembled without damaging the interface material. The cooling fluid circulating in the liquid cooling plate 44 can be provided by a number of means well known in the art of cooling servers, mainframe computers and telecommunications equipment. Two specific examples are as follows. (1) A dedicated stand-alone cooler can provide a cooling fluid, usually deionized water, at a predetermined temperature and a predetermined volume flow rate. The temperature of the liquid entering the cold plate is set according to the desired maximum operating temperature of the microprocessor being cooled. The volumetric flow rate of the cooling fluid is set according to the total wattage that needs to be transferred and by the desired maximum temperature rise of the cooling fluid in the liquid cooling plate. Determining set values for both these parameters, namely the cooling fluid temperature entering the cold plate and the volumetric flow rate of the cooling fluid, can be accomplished by well-known and years of engineering methods, This experiment is unnecessary. Alternatively, (2) a building facility that houses the equipment that is being cooled, such as a data center that houses and supports many servers, can provide cooling water with sufficient volumetric flow at a given temperature and pressure. . This is sometimes called “utility water”. Designing a liquid cold plate based on these values to achieve the required heat transfer can be accomplished in a well-known and long-standing engineering manner, as in the previous example.

  An advantage of this embodiment is that the fluid cooled electronic component, such as a chip or microprocessor, along with the circuit board on which it is mounted, provides cooling fluid to the liquid cooling plate component or removes the cooling fluid therefrom. It can be removed for repair or replacement without interfering with the plumbing. This reduces the risk of using water to indirectly cool electronic components because it reduces the risk of cooling water leaking and damaging electronic components during normal operation, including inspection and maintenance. is there. This benefit can be further enhanced by providing a physical barrier, such as a septum or wall 50 that separates the circuit board region from the liquid cooling plate region. In extreme terms, the physical barrier can be in the form of a housing (as suggested by dotted line 52) that houses the circuit board, where the condenser components and electrical connectors are one of the housings. Protrudes through the wall. As shown in FIG. 12c, the structure can even completely enclose the condenser 20, leaving the interface material 48 outside the housing 52 '.

  In FIG. 12, the liquid cooling plate is fitted to the inclined bottom surface of the condenser 20. The liquid cooling plate 44 is provided with a correspondingly angled upper surface. The circuit board moves horizontally and engages both the electrical connector 46 and the liquid cooling plate 44. A spring 54 urges the upper surface of the liquid cooling plate toward the lower surface of the condenser component to provide excellent thermal communication at the interface. As with air-cooled fins, liquid cooling plates can be used on the bottom, top, or both of the condenser. In FIG. 12, the liquid cooling plate has an inclined surface, which merely represents a design choice. A cooling plate with the top and bottom surfaces parallel (as is most common) can be used by tilting the entire cooling plate as needed to mate with the inclined surface of the condenser component.

  In any embodiment or configuration, the heat transfer device according to the present invention is high when compared to known prior art devices, especially for applications where vertical space is limited due to the configuration of the present invention. Reduced, allowing improved and efficient heat transfer.

  Thus, while the basic novel features of the present invention have been illustrated and described and applied as applicable to its preferred embodiments, the forms and details of the illustrated apparatus and various omissions and substitutions of their operation and Changes can be made by those skilled in the art without departing from the spirit of the invention. For example, all combinations of those elements that perform substantially the same function substantially similarly to achieve the same result are expressly intended to be within the scope of the invention. Furthermore, the structures and / or elements shown and / or described in connection with any disclosed form of embodiment of the invention may be used as a general design choice for any other disclosed or It can be incorporated into the form or embodiment described or suggested. Accordingly, the invention should be limited only as indicated by the scope of the claims appended hereto.

Claims (17)

A condenser used in a heat transfer device and adapted to be coupled to a reservoir holding a heat transfer fluid in at least one of a liquid state and a gas state;
A chamber having a top wall and a bottom wall;
An inlet for receiving the heat transfer fluid in a gaseous state from the reservoir;
An outlet for returning the heat transfer fluid in a liquid state to the reservoir;
A first header space and a second header space in the chamber ;
Including
The inlet is disposed at a height greater than the outlet height with respect to the reservoir and is configured to introduce the heat transfer fluid into the first header space in the gaseous state;
The outlet is configured to guide the heat transfer fluid to the second header space in the liquid state;
Each of the inlet and the outlet is disposed in the reservoir at a height that exceeds a height of the heat transfer fluid in its liquid state;
The bottom wall includes a substantially vertical array of fins disposed within the chamber so as to extend from the top wall to the bottom wall, the array being mounted with means for providing cooling to the condenser Is thermally connected to the
The fin defines a passage therethrough, the passage leading to the first header space and the second header space and allowing the flow of heat transfer fluid through the passage; A condenser providing a cooling surface for condensing the gaseous heat transfer fluid to a liquid state within the chamber .   The bottom surface of claim 1, wherein the bottom surface is disposed to be inclined in the direction of the outlet so as to facilitate the flow of the heat transfer fluid to the outlet when the heat transfer fluid is in its liquid state. Condenser. Each of the fins has a plurality of grooves,
The condenser of claim 1, wherein the plurality of grooves are substantially aligned with a direction of gravity of the heat transfer fluid .   The condenser according to claim 3, wherein the grooves are arranged in matched pairs on both sides of the fin.   The condenser according to claim 3, wherein the grooves are arranged in a staggered relationship on both sides of the fin. The condenser of claim 1, wherein a depth of the condenser is greater than a height of the condenser , whereby the heat transfer device can have a reduced height.   The condensation according to claim 1, further comprising a plurality of second fins outside the condenser, wherein the plurality of second fins are not in contact with the heat transfer fluid in any of its liquid state or gas state. vessel. The condenser of claim 1, further comprising a liquid cooling plate in thermal communication with the chamber above and / or below the chamber. A heat transfer device used in an environment where the vertical clearance is small,
The condenser according to any one of claims 1 to 8,
A reservoir for holding the heat transfer fluid in a liquid state;
Including
The heat transfer fluid in its gaseous state can enter the first header space of the condenser through the inlet, and then the heat transfer fluid flows through the top of the passage and contacts the fins. Where the gas condenses, and then the heat transfer flow flows through the bottom of the passage to the second header space and then back to the outlet and back to the reservoir.   The heat transfer device of claim 9, further comprising a first conduit for directing the heat transfer fluid from the reservoir to the inlet.   The heat transfer device of claim 10, further comprising a second conduit for directing the condensed heat transfer fluid in its liquid state from the outlet to the reservoir.   The heat transfer of claim 9, further comprising means for attaching an external heat transfer device to the heat transfer device to provide thermal contact with the condenser and to provide additional heat transfer capability to the heat transfer device. apparatus.   The heat transfer device according to claim 12, further comprising a heat transfer medium applied to the outside of the condenser to provide heat conduction between the heat transfer device and the condenser.   The heat transfer device of claim 12, wherein the means for attaching includes a spring that causes the external heat transfer device to contact the condenser.   The heat transfer device of claim 12 further comprising a barrier component.   The heat transfer device of claim 15, wherein the barrier component is a wall of a housing.   The heat transfer device of claim 16, wherein the housing substantially surrounds the heat transfer device.

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