Patent Publication Number: US-2022221231-A1

Title: Two-phase immersion-cooling micro-grooved boiler

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to an earlier Taiwan patent application Ser. No. 110200244, filed Jan. 8, 2021, which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of Invention 
     The present invention relates to a boiler. More specifically, this present invention relates to a two-phase immersion-cooling micro-grooved boiler. 
     Description of the Related Art 
     In recent years, electronic technology has developed rapidly, especially high-power electronic equipments. With the increase in the power of electronic equipments, bigger heat dissipation capacity is required. Therefore, the cooling of electronic equipments is one of the major issues to be addressed. 
     Regarding the cooling method of electronic equipments, the immersion-cooling boiler or heat exchanger has been widely used in the fields of electronics, chemical engineering and the like. The immersion-cooling boiler employs a two-phase fluid boiling heat exchange method to achieve the effect of heat dissipation. Practically applied, the boiler is in thermal contact with heat generating objects and submerged within a non-conductive insulating working liquid. When heat generating objects are in operation, a great deal of heat is generated, and then transferred to the boiler through a copper heat transfer member. As a result, the working fluid is boiled due to absorbing the heat of the boiler. The boiling-triggered bubbles flow out from the outer surface of the boiler; in the meantime the working fluid must continue to flow into the outer surface of the boiler, ensuring the consistent efficient heat dissipation. 
     However, in the event that the outflow pressure of the bubbles is equal to or greater than the inflow pressure of the working liquid, the copper heat transfer member cannot have access to the working liquid due to the entire outer surface of the boiler being covered by the boiling-triggered bubbles, resulting in the failure of heat transfer. Such failure of heat transfer, generally called dry-out, causes the boiler to malfunction. 
     In view of this, in order to ensure high heat exchange efficiency and sufficient working fluid flowback during the immersion-cooling boiler operates, it is necessary to develop a novel immersion-cooling boiler that can solve the aforementioned problem. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a two-phase immersion-cooling micro-grooved boiler, which is mainly applied to solve the heat transfer inefficiency of the immersion-cooling boiler. 
     In order to attain the aforesaid object, according to one embodiment, provided is a two-phase immersion-cooling micro-grooved boiler, which comprises a heat transfer member for thermal contact with a heat generating object to be cooled, and a capillary layer positioned in tight contact with a surface of the heat transfer member. The capillary layer has an array of micro-grooves, which divides the capillary layer into a plurality of heat dissipating units. A bottom surface of the micro-grooves is coated with a thermal resistance layer. 
     In one or more embodiments, the micro-grooves are arranged in a spaced, parallel relationship on the heat transfer member. 
     In one or more embodiments, the micro-grooves are arranged on the heat transfer member in a symmetrical, inclined direction toward a longitudinal center line of the heat transfer member. 
     In one or more embodiments, the micro-grooves have a cross-sectional width of between 300 μm and 800 μm. 
     In one or more embodiments, the heat dissipating units have a plurality of capillary pores which has a cross-sectional diameter of between 5 μm and 50 μm. 
     As aforementioned, according to the two-phase immersion-cooling micro-grooved boiler disclosed in the present invention, while the boiler absorbs the heat generated by the heat generating object, the working liquid can flow into the capillary pores of the heat dissipating units from the sidewall of the micro-grooves without being blocked from contact with the heat transfer member by boiling-triggered bubbles. As a result, dry-out of the boiler can be avoided, thereby improving the heat exchange efficiency of the boiler and the flow-back rate of the working fluid. 
     The above summary contains simplifications, generalizations and omissions of detail and is not intended as a comprehensive description of the claimed subject matter but, rather, is intended to provide a brief overview of some of the functionality associated therewith. Other systems, methods, functionality, features and advantages of the claimed subject matter will be or will become apparent to one with skill in the art upon examination of the following figures and detailed written description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description of the illustrative embodiments can be read in conjunction with the accompanying figures. It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to other elements. Embodiments incorporating teachings of the present disclosure are shown and described with respect to the figures presented herein, in which: 
         FIG. 1  is a perspective view of an example conventional immersion-cooling boiler, according to prior art; 
         FIG. 2  is a schematic perspective view illustrating how an example conventional immersion-cooling boiler is applied to cool a heat generating object, according to prior art; 
         FIG. 3  is a perspective view of an example two-phase immersion-cooling micro-grooved boiler, according to one or more embodiments; 
         FIG. 4  is a perspective view of an another example two-phase immersion-cooling micro-grooved boiler, according to one or more embodiments; and 
         FIG. 5  is a schematic perspective view illustrating how an example two-phase immersion-cooling micro-grooved boiler is applied to cool a heat generating object, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of exemplary embodiments of the disclosure, specific exemplary embodiments in which the disclosure may be practiced are described in sufficient detail to enable those skilled in the art to practice the disclosed embodiments. For example, specific details such as specific method orders, structures, elements, and connections have been presented herein. However, it is to be understood that the specific details presented need not be utilized to practice embodiments of the present disclosure. It is also to be understood that other embodiments may be utilized and that logical, architectural, programmatic, mechanical, electrical and other changes may be made without departing from general scope of the disclosure. 
     The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and equivalents thereof. 
     References within the specification to “one embodiment,” “an embodiment,” “embodiments”, or “one or more embodiments” are intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The appearance of such phrases in various places within the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Further, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. 
     It is understood that the use of specific component, device and/or parameter names and/or corresponding acronyms thereof, such as those of the executing utility, logic, and/or firmware described herein, are for example only and not meant to imply any limitations on the described embodiments. The embodiments may thus be described with different nomenclature and/or terminology utilized to describe the components, devices, parameters, methods and/or functions herein, without limitation. References to any specific protocol or proprietary name in describing one or more elements, features or concepts of the embodiments are provided solely as examples of one implementation, and such references do not limit the extension of the claimed embodiments to embodiments in which different element, feature, protocol, or concept names are utilized. Thus, each term utilized herein is to be given its broadest interpretation given the context in which that term is utilized. 
     Within the descriptions of the different views of the figures, the use of the same reference numerals and/or symbols in different drawings indicates similar or identical items, and similar elements can be provided similar names and reference numerals throughout the figure(s). The specific identifiers/names and reference numerals assigned to the elements are provided solely to aid in the description and are not meant to imply any limitations (structural or functional or otherwise) on the described embodiments. In the illustration of the various embodiments, two different figures can be provided that have overlaps and/or similarities in the components within the two figures (e.g.,  FIGS. 3 and 4 ). In such instances, the descriptions of these figures can be presented together with associated similar reference numerals separated by commas and/or a slash. Some components that are not expected to be different from one implementation to the other are provided the same reference numerals within the figures, to simplify the descriptions of the figures. 
     Those of ordinary skill in the art will appreciate that the hardware components and basic configuration depicted in any of the figures illustrated by the drawings and described herein may vary. For example, the illustrative components within a boiler ( FIG. 3 ) and other devices and systems are not intended to be exhaustive, but rather be representative of and highlight components that can be utilized to implement aspects of the present disclosure. For example, other devices/components may be used in addition to or in place of the hardware depicted. The depicted examples do not convey or imply any architectural or other limitations with respect to the presently described embodiments and/or the general disclosure. 
     The object of the present invention is to provide a two-phase immersion-cooling micro-grooved boiler, which is mainly applied to solve the heat transfer inefficiency of the immersion-cooling boiler. 
     Turning now to the figures,  FIG. 1  illustrates a perspective view of an example conventional immersion-cooling boiler. According to prior art, the conventional immersion-cooling boiler structurally includes a heat transfer member  10  for thermal contact with a heat generating object to be cooled, and a capillary layer  20 . The capillary layer  20  is positioned in tight contact with a surface of the heat transfer member  10 . It should be noted that the capillary layer  20  does not have any micro-grooves. 
     Next, with reference to  FIG. 2 , there is presented a schematic perspective view illustrating how an example conventional immersion-cooling boiler is applied to cool a heat generating object, according to prior art. As shown in  FIG. 2 , practically applied, the conventional immersion-cooling boiler is in thermal contact with a heat generating object  500  to be cooled. Specifically, it&#39;s the heat transfer member  10  of the immersion-cooling boiler that is in thermal contact with the heat generating object  500 , which is submerged within a non-conductive insulating working fluid  400  in a cabinet  300 . When the heat generating object  500  operates, a great amount of heat is generated, and then transferred to the boiler by way of the heat transfer member  10 . Subsequently, the working fluid  400  is boiled due to absorbing the heat of the boiler. The boiling-triggered bubbles flow out from the surface of the capillary layer  20 , and then the working fluid  400  continuously flows into the capillary layer  20  to achieve the effect of consistent heat transfer. 
     However, given the conventional immersion-cooling boiler, the capillary layer  20  does not have any micro-grooves. In the event that the outflow pressure of the bubbles is equal to or greater than the inflow pressure of the working liquid, the working liquid  400  is blocked from flowing into the capillary layer  20  due to the entire outer surface of the capillary layer  20  being covered by the boiling-triggered bubbles. Therefore, the heat transfer member  10  cannot have access to the working liquid  400 , resulting in the failure of heat transfer. Such failure of heat transfer, so called dry-out, causes the boiler to malfunction. 
     In view of this, in order to solve the above-mentioned defect in the conventional immersion-cooling boiler, a two-phase immersion-cooling micro-grooved boiler is provided. With reference now to  FIG. 3 , there is presented a perspective view of an example two-phase immersion-cooling micro-grooved boiler. According to one embodiment of the present invention, the present immersion-cooling boiler includes a heat transfer member  10  for thermal contact with a heat generating object to be cooled, and a capillary layer  20 . The capillary layer  20  is positioned in tight contact with a surface of the heat transfer member  10 . It is worth noting that the capillary layer  20  has an array of micro-grooves  202 , which divides the capillary layer  20  into a plurality of heat dissipating units  201 . The micro-grooves  202  are arranged in a spaced, parallel relationship on the heat transfer member  10 . According to a preferred embodiment, as shown in  FIG. 4 , the micro-grooves  202  are arranged on the heat transfer member  10  in a symmetrical, inclined direction toward a longitudinal center line of the heat transfer member  10 . 
     According to a preferred embodiment, the micro-grooves  202  have a cross-sectional width of between 300 μm and 800 μm. In addition, the total cross-sectional area of all the micro-grooves  202  represents no more than 5% of the total surface area of the heat transfer member  10 . 
     Next, in order to describe in detail how the immersion-cooling boiler of the present invention operates in terms of practical application, with reference now to  FIG. 5 , there is presented a schematic perspective view illustrating how an example two-phase immersion-cooling micro-grooved boiler is applied to cool a heat generating object. 
     According to one embodiment, the present immersion-cooling boiler is in thermal contact with a heat generating object  500  to be cooled. Specifically, it&#39;s the heat transfer member  10  of the immersion-cooling boiler that is in thermal contact with the heat generating object  500 , which is submerged within a non-conductive insulating working fluid  400  in a cabinet  300 . Preferably, the heat transfer member  10  is mainly made of copper. When the heat generating object  500  operates, a great amount of heat is generated, and then transferred to the boiler by way of the heat transfer member  10 . Subsequently, the working fluid  400  is boiled due to absorbing the heat of the boiler. The boiling-triggered bubbles flow out from the surface of the capillary layer  20 . 
     Furthermore, the capillary structure of the heat dissipating units  201  can be a mesh type or powder-sintered type. Taking the mesh type for example, the heat dissipating units  201  have a mesh structure made from a plurality of wires whose outer surface is attached with many small protrusions. The mesh has numerous capillary pores, which have a cross-sectional diameter of between 5 μm and 50 μm. The wires are made of such materials with toughness and good thermal conductivity as copper, aluminum, stainless steel, etc. It is worth noting that the capillary structure can be a wire mesh made from either such a single material or a combination of different materials. In addition, the protrusions attached onto the outer surface of the wires are fine powders whose particle size is about one-third to about one-fifth the diameter of the wires. The fine powders are made of materials such as copper, aluminum, stainless steel, etc. 
     In practical applications, when the heat generating object  500  operates, a great amount of heat is generated, and then transferred to the capillary layer  20  by way of the heat transfer member  10 . Absorbing the heat, the working fluid  400  within the heat dissipating units  201  starts being boiled to form bubbles. The boiling-triggered bubbles move within the capillary structure of the heat dissipating units  201 , and then flow out from the surface of the capillary layer  20 . Subsequently, the working fluid  400  continuously flows into the capillary layer  20  to achieve the effect of consistent heat transfer. 
     Besides, in order to prevent the entire outer surface of the capillary layer  20  from being covered by the boiling-triggered bubbles so that the working liquid  400  can flow into the capillary layer  20  for contact with the heat transfer member  10 , according to one embodiment, the capillary layer  20  has an array of micro-grooves  202 , which divides the capillary layer  20  into a plurality of heat dissipating units  201 . A bottom surface of the micro-grooves  202  is coated with a thermal resistance layer. The thermal resistance layer is adapted to reduce the heat transfer capacity of the heat transfer member  10  such that the working liquid  400  on the bottom surface of the micro-grooves  202  can remain unboiled. Therefore, by way of the micro-grooves, the capillary pores of the immersion-cooling boiler can be replenished in time with sufficient working fluid to improve the heat transfer efficiency. 
     Notably, when the immersion-cooling boiler absorbs the heat generated by the heat generating object, the working liquid  400  can also flow from the sidewall of the micro-grooves  202  into the capillary pores of the heat dissipating units  201  without being blocked from contact with the heat transfer member  10  by boiling-triggered bubbles. As a result, by way of the micro-grooves, dry-out of the immersion-cooling boiler can be avoided, thereby improving the heat exchange efficiency of the boiler and the flow-back rate of the working fluid. 
     Based on the foregoing disclosure of technical features, the present invention has the following advantages compared with the prior art:
         1. Improving the cooling efficiency of the boiler: By way of the micro-grooves, dry-out of the immersion-cooling boiler can be avoided, thereby improving the heat exchange efficiency.   2. Meeting the need for high flow-back rate of the working fluid: The bottom surface of the micro-grooves is coated with a thermal resistance layer, which is adapted to reduce the heat transfer capacity of the heat transfer member such that the working liquid can remain unboiled, and flow freely on the bottom surface of the micro-grooves.       

      The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the disclosure. The described embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. 
     While the disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular system, device or component thereof to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.