Patent Publication Number: US-2020284523-A1

Title: Gravity-driven gas-liquid circulation device

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a gas-liquid circulation device and more particularly to a miniaturized gravity-driven gas-liquid circulation device for use in an electronic product. 
     2. Description of Related Art 
     Electronic equipment is generally provided with a central processing unit (CPU) for processing commands and software data. The computation speed and data transfer rate of a piece of electronic equipment hinge on the performance of its CPU. 
     A CPU can maintain its performance or capacity at a reasonable level in most cases. If, however, the heat generated by a CPU cannot be dissipated effectively, the CPU may be overheated, and the electronic equipment using the CPU may eventually slow down or even stop working as a result. The high temperature of the overheated CPU may also damage the neighboring electronic components such that the service life of the electronic equipment is cut short. It is therefore imperative to use a suitable method or technique to cool a CPU sufficiently and thereby maintain its normal operation. 
     One typical technique for cooling the CPU of a piece of electronic equipment is to provide the electronic equipment with a built-in fan, the objective being to generate an air flow that helps bring down the temperature of the CPU. However, the cooling effect of the fan will be compromised when ambient temperature is high. Another cooling technique involves the use of a cooling agent or refrigerant such as water. 
     According to the above, the conventional methods for cooling a CPU still leave room for improvement. The inventor of the present invention thought it necessary to devise a novel method for cooling a CPU. 
     BRIEF SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a miniaturized gas-liquid circulation device that is suitable for use in electronic equipment. 
     In order to achieve the above objective, the present invention provides a gravity-driven gas-liquid circulation device, comprising a condensation unit and an evaporation unit. The condensation unit has an end connected to a gaseous phase input tube and another end connected to a liquid phase output tube. The evaporation unit comprises a thermally conductive base for contact with an external high-temperature device, a plurality of fins integrally formed on the thermally conductive base, and an integrally formed scaling housing provided on the thermally conductive base and enclosing the fins, wherein the integrally formed sealing housing is provided with a gas outlet hole and a liquid inlet hole, the gas outlet hole is lower than the gaseous phase input tube and is connected to an end of the gaseous phase input tube in order to guide a high-temperature gaseous-state working fluid through the gaseous phase input tube to the condensation unit, and the liquid inlet hole is level with or lower than the liquid phase output tube and is connected to an end of the liquid phase output tube in order to receive a liquid-state working fluid, allowing a force of gravity acting on the liquid-state working fluid to provide a siphoning force and thereby cause circulation of the liquid-state working fluid and the gaseous-state working fluid. 
     Furthermore, the thermally conductive base is provided thereon with a reinforcement member, wherein the reinforcement member is clamped vertically between the integrally formed sealing housing and the thermally conductive base and serves to increase the compressive strength. 
     Furthermore, the reinforcement member is provided with at least one through hole and/or at least one aperture to enable passage of the liquid-state working fluid. 
     Furthermore, the integrally formed sealing housing includes a first housing portion and a second housing portion. The first housing portion is provided on the thermally conductive base and encloses the fins. The second housing portion is integrally formed with, and lies on top of, the first housing portion. 
     Furthermore, the top sides of the tins are higher than the bottom edge, and lower than the top edge, of the liquid inlet hole or are higher than the top edge of the liquid inlet hole. 
     Furthermore, the gas outlet hole has a larger hole diameter than the liquid inlet hole. 
     Furthermore, the spacing between each two adjacent fins forms a flow channel, and the spacing ranges from 0.2 mm to 1 mm. 
     Furthermore, the liquid inlet hole is in alignment with the flow channels. 
     Furthermore, the fins are integrally formed on the thermally conductive base by a relieving means. 
     Furthermore, each fin has a thickness ranging from 0.2 mm to 1 mm. 
     Furthermore, the condensation unit comprises a front condensation assembly, a rear condensation assembly, and a plurality of heat dissipation fins. The front condensation assembly comprises a front left flow tube, a front right flow tube, and a plurality of front heat dissipation tubes. The front left flow tube and the front right flow tube are provided on two opposite lateral sides of the front condensation assembly respectively and are connected to the gaseous phase input tube and the liquid phase output tube respectively. The front heat dissipation tubes are in communication with the front left flow tube and the front right flow tube and are vertically spaced apart. The rear condensation assembly comprises a rear left flow tube, a rear right flow tube, and a plurality of rear heat dissipation tubes. The rear left flow tube and the rear right flow tube are provided on two opposite lateral sides of the rear condensation assembly respectively. The rear heat dissipation tubes are in communication with the rear left flow tube and the rear right flow tube and are vertically spaced apart. Gaps between the rear heat dissipation tubes and gaps between the front heat dissipation tubes correspond to each other and jointly form a plurality of through grooves. The heat dissipation fins are in contact with surfaces of the front heat dissipation tubes and surfaces of the rear heat dissipation tubes to enable heat exchange between the heat dissipation fins and the heat dissipation tubes. The front left flow tube and the rear left flow tube are separately formed. The front right flow tube and the rear right flow tube are separately formed. 
     Furthermore, the condensation unit comprises a front condensation assembly, a rear condensation assembly, and a plurality of heat dissipation fins. The front condensation assembly comprises a front left flow tube, a front right flow tube, and a plurality of front heat dissipation tubes. The front left flow tube and the front right flow tube are provided on two opposite lateral sides of the front condensation assembly respectively and are connected to the gaseous phase input tube and the liquid phase output tube respectively. The front heat dissipation tubes are in communication with the front left flow tube and the front right flow tube and are vertically spaced apart. The rear condensation assembly comprises a rear left flow tube, a rear right flow tube, and a plurality of rear heat dissipation tubes. The rear left flow tube and the rear right flow tube are provided on two opposite lateral sides of the rear condensation assembly respectively. The rear heat dissipation tubes are in communication with the rear left flow tube and the rear right flow tube and are vertically spaced apart. Gaps between the rear heat dissipation tubes and gaps between the front heat dissipation tubes correspond to each other and jointly form a plurality of through grooves. The heat dissipation fins are in contact with surfaces of the front heat dissipation tubes and surfaces of the rear heat dissipation tubes to enable heat exchange between the heat dissipation fins and the heat dissipation tubes. The front left flow tube and the rear left flow tube are jointly formed by two stamped plates. The front right flow tube and the rear right flow tube are jointly formed by two stamped plates. 
     Furthermore, at least one left opening is provided between the front left flow tube and the rear left flow tube. At least one right opening is provided between the front right flow tube and the rear right flow tube. The left opening and the right opening are diagonally arranged with respect to each other, wherein the bottom side of the left opening is higher than the top side of the right opening. 
     Furthermore, both the front heat dissipation tube and the rear heat dissipation tube have a flattened configuration. 
     Furthermore, the front heat dissipation tube is provided therein with a plurality of supporting ribs, which extend through the front heat dissipation tube. The rear heat dissipation tube is provided therein with a plurality of supporting ribs, which extend through the rear heat dissipation tube. 
     Furthermore, a plurality of microstructures are provided on the surface of each heat dissipation fin to increase the area of contact between each heat dissipation fin and air. 
     Furthermore, the heat dissipation fins have a corrugated configuration or a serrated configuration. 
     Furthermore, the condensation unit includes a plurality of condensation plate assemblies and a plurality of heat dissipation fins. The condensation plate assemblies are vertically spaced apart. The heat dissipation fins are inserted between the condensation plate assemblies and are therefore also spaced apart from one another. Each condensation plate assembly is provided with a left flow tube on the left side, a right flow tube on the right side, and a flow passage in communication with the left flow tube and the right flow tube, wherein the left flow tube and the right flow tube are connected to the gaseous phase input tube and the liquid phase output tube respectively. 
     Furthermore, each condensation plate assembly is formed by two metal plates, wherein each metal plate is provided with a plurality of protruding structures on the side facing the flow passage in order to increase the strength of the condensation plate assembly. 
     Comparing to the conventional techniques, the present invention has the following advantages: 
     The gas-liquid circulation device disclosed herein is provided with a condensation unit and an evaporation unit that utilize not only the phase change of a working fluid to cool an electronic product (i.e. the phase change taking place while the working fluid is changed between a heat-absorbing state and a heat-releasing state), but also the force of gravity acting on the working fluid to enable continuous operation of the gas-liquid circulation device, thereby saving the cost and space otherwise required for installing an electromechanical driving device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of the gravity-driven gas-liquid circulation device of the present invention. 
         FIG. 2  is a sectional view of the front condensation assembly according to the first embodiment of the condensation unit of the present invention. 
         FIG. 3  is a sectional view of the rear condensation assembly according to the first embodiment of the condensation unit of the present invention. 
         FIG. 4  is a perspective view of the heat dissipation fin according to the first embodiment of the condensation unit of the present invention. 
         FIG. 5  is a perspective view of the front heat dissipation tube according to the first embodiment of the condensation unit of the present invention. 
         FIG. 6  is a perspective view of the evaporation unit of the present invention. 
         FIG. 7  is the sectional view (I) of the evaporation unit of the present invention. 
         FIG. 8  is the sectional view (II) of the evaporation unit of the present invention. 
         FIG. 9  is a schematic circulation diagram of the gravity-driven gas-liquid circulation device of the present invention. 
         FIG. 10  is a perspective view of the second embodiment of the condensation unit of the present invention. 
         FIG. 11  is a sectional view of the front condensation assembly according to the second embodiment of the condensation unit of the present invention. 
         FIG. 12  is a sectional view of the rear condensation assembly according to the second embodiment of the condensation unit of the present invention. 
         FIG. 13  is an assembled perspective view according to the third embodiment of the condensation unit of the present invention. 
         FIG. 14  is an exploded perspective view according to the third embodiment of the condensation unit of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The details and technical solution of the present invention are hereunder described with reference to accompanying drawings. For illustrative sake, the accompanying drawings are not drawn to scale. The accompanying drawings and the scale thereof are not restrictive of the present invention. 
     Please refer to  FIG. 1  for a perspective view of the gravity-driven gas-liquid circulation device of the present invention. 
     The gravity-driven gas-liquid circulation device  100  shown in  FIG. 1  is configured for use mainly in the fields of optics, communications, data processing, servers, and so on where high-heat laminated circuits are typically required. The present invention can be applied to such electronic products as servers, data displays, remote radio units (RRUs) for communication purposes, artificial intelligence (AI) devices, display chips, and laser chips to provide a cooling/heat dissipation effect through conduction-, convection-, or material-based heat exchange. The gas-liquid circulation device of the present invention is intended to dissipate heat from an electronic product via a continuously circulated working fluid that is driven by the force of gravity acting on the working fluid itself, thereby saving the cost and space otherwise required to drive the circulation electromechanically. 
     The gravity-driven gas-liquid circulation device  100  includes a condensation unit  10 A and an evaporation unit  20 A. A working fluid is circulated through the two units while undergoing a cyclic change of phase, which occurs when the working fluid is changed between a heat-absorbing state and a heat-releasing state. The phase change helps cool down the electronic product to which the gravity-driven gas-liquid circulation device  100  is applied, lest the electronic components of the product be damaged, or the performance of the product be lowered, due to prolonged exposure to high heat. 
     Please refer to  FIG. 2  and  FIG. 3  for sectional views respectively of the front and rear condensation assemblies of the condensation unit of the present invention. 
     In this embodiment, the condensation unit  10 A is connected to a gaseous phase input tube AT at one end and a liquid phase output tube WT at another end. The condensation unit  10 A includes a front condensation assembly  11 A, a rear condensation assembly  12 A, and a plurality of heat dissipation fins  13 A. The front condensation assembly  11 A includes a front left flow tube  111 A, a front right flow tube  112 A, and a plurality of front heat dissipation tubes  113 A in communication with the front left flow tube  111 A and the front right flow tube  112 A. The front left flow tube  111 A and the front right flow tube  112 A are provided on the two opposite lateral sides of the front condensation assembly  11 A respectively and are connected to the gaseous phase input tube AT and the liquid phase output tube WT respectively. The front heat dissipation tubes  113 A are vertically spaced apart. The rear condensation assembly  12 A is parallel to the front condensation assembly  11 A and includes a rear left flow tube  121 A, a rear right flow tube  122 A, and a plurality of rear heat dissipation tubes  123 A in communication with the rear left flow tube  121 A and the rear right flow tube  122 A. The rear left flow tube  121 A and the rear right flow tube  122 A are provided on the two opposite lateral sides of the rear condensation assembly  12 A respectively. The rear heat dissipation tubes  123 A are vertically spaced apart. The gaps between the rear heat dissipation tubes  123 A and those between the front heat dissipation tubes  113 A correspond to each other and jointly form a plurality of through grooves GA. 
     The front left flow tube  11 A and the rear left flow tube  121 A are separately formed, and so are the front right flow tube  112 A and the rear right flow tube  122 A. The two flow tubes on either lateral side of the condensation unit  10 A are fixedly coupled to each other by a pair of sealing covers  114 A (one on top and the other at the bottom) to increase the compressive strength of the flow tubes. The front left flow tube  111 A, the front right flow tube  112 A, the rear left flow tube  121 A, and the rear right flow tube  122 A are generally square tubes, with the sides facing diametrically away from the front heat dissipation tubes  113 A (or the rear heat dissipation tubes  123 A) having an outwardly protruding, (circularly) curved shape to allow more efficient use of the space inside the flow tubes. 
     To enable communication between the front condensation assembly  11 A and the rear condensation assembly  12 A, at least one left opening LO is provided between the front left flow tube  111 A and the rear left flow tube  121 A, and at least one right opening RO is provided between the front right flow tube  112 A and the rear right flow tube  122 A. In the preferred embodiment shown in  FIG. 1 , a linking element  115 A is provided between the front left flow tube  111 A and the rear left flow tube  121 A and is aligned, and in communication, with the left opening LO so as to connect, and allow communication between, the flow tubes. Similarly, a linking element (not shown) is provided between the front right flow tube  112 A and the rear right flow tube  122 A and is aligned, and in communication, with the right opening RO. As shown in  FIG. 2 , there is one left opening LO and one right opening RO, and the two openings are rectangular openings diagonally arranged with respect to each other, wherein the bottom side of the left opening LO is higher than the top side of the right opening RO. The area of the left opening LO is larger than that of the right opening RO to enable rapid input and slow output of the working fluid. It should be pointed out, however, that the openings described above serve only as an example; the present invention imposes no limitation on the number or shapes of those openings. 
     Please refer to  FIG. 4  for a perspective view of a heat dissipation fin in the condensation unit of the present invention. 
     The heat dissipation fins  13 A are inserted in the through grooves GA respectively and extend through the front condensation assembly  11 A and the rear condensation assembly  12 A. The heat dissipation fins  13 A are in contact with the surfaces of the front heat dissipation tubes  113 A and of the rear heat dissipation tubes  123 A so that heat exchange can take place between the heat dissipation fins  13 A and the heat dissipation tubes  113 A and  123 A. The heat dissipation fins  13 A may have a corrugated configuration, a serrated configuration, or any other configuration achievable by bending a metal plate. Each heat dissipation fin  13 A has a height D 1  ranging from 4 mm to 8 mm and a length D 2  ranging from 12 mm to 60 mm. The distance D 3  between each two adjacent bends of each heat dissipation fin  13 A ranges from 2 mm to 4 mm. There are a plurality of microstructures  131 A on the surface of each heat dissipation fin  13 A. The microstructures  131 A may extend outward or inward with respect to the heat dissipation fins  13 A to increase the area of contact between each heat dissipation fin  13 A and air, thereby enhancing the efficiency of heat dissipation.  10052   j  Please refer to  FIG. 5  for a perspective view of a front heat dissipation tube in the condensation unit of the present invention. 
     As shown in  FIG. 5 , the front heat dissipation tube  113 A has a flattened configuration. The two ends of the front heat dissipation tube  113 A are inserted in the front left flow tube  111 A and the front right flow tube  112 A respectively to connect the two flow tubes together. The front heat dissipation tube  113 A has a height D 4  ranging from 1 mm to 2 mm to facilitate passage of, and allow sufficient heat absorption by, the working fluid. The front heat dissipation tube  113 A has a width D 5  ranging from 12 mm to 40 mm so as to provide a relatively large heat dissipation area that enhances contact, and hence heat exchange, with air and the adjacent heat dissipation fins  13 A. The front heat dissipation tube  113 A is provided therein with a plurality of supporting ribs R, which extend through the front heat dissipation tube  113 A. The number of the supporting ribs R may range from the value of one half of the width (in millimeter) of the front heat dissipation tube  113 A to the value of the full width (in millimeter) of the front heat dissipation tube  113 A. For example, when the width of the front heat dissipation tube  113 A is 12 mm, there may be 6 to 12 supporting ribs R for reinforcing, and thereby preventing deformation of, the front heat dissipation tube  113 A. The rear heat dissipation tubes  123 A in the present invention are structurally identical to the front heat dissipation tubes  113 A and therefore will not be described or shown repeatedly. 
     Please refer to  FIG. 6  to  FIG. 8  in conjunction with  FIG. 1 , wherein  FIG. 6  to  FIG. 8  respectively show a perspective view and two different sectional views of the evaporation unit of the present invention. 
     The evaporation unit  20 A includes a thermally conductive base  21 A for contact with a high-temperature device, a plurality of fins  22 A integrally formed on the thermally conductive base  21 A, and an integrally formed sealing housing  23 A provided on the thermally conductive base  21 A to enclose the fins  22 A. In this preferred embodiment, the thermally conductive base  21 A, the fins  22 A, and the integrally formed sealing housing  23 A are made of aluminum or copper. The integrally formed sealing housing  23 A includes a first housing portion  231 A and a second housing portion  232 A. The first housing portion  231 A is provided on the thermally conductive base  21 A and encloses the fins  22 A. The second housing portion  232 A is integrally formed with, and lies on top of, the first housing portion  231 A. The interior space of the second housing portion  232 A is smaller than that of the first housing portion  231 A to accelerate the working fluid. The thermally conductive base  21 A is provided with a plurality of locking holes  211 A for securing the evaporation unit  20 A to a high-temperature device. 
     The integrally formed sealing housing  23 A is provided with a gas outlet hole  233 A, which is lower than the gaseous phase input tube AT and is connected to one end of the gaseous phase input tube AT in order to guide the high-temperature gaseous-state working fluid through the gaseous phase input tube AT to the condensation unit  10 A. The integrally formed scaling housing  23 A is also provided with a liquid inlet hole  234 A, which is level with or lower than the liquid phase output tube WT and is connected to one end of the liquid phase output tube WT in order to receive the liquid-state working fluid. The force of gravity acting on the liquid-state working fluid will provide a siphoning force that causes circulation of the working fluid, thereby enabling the gravity-driven gas-liquid circulation device  100  to operate continuously without being driven by an electromechanical means. In this preferred embodiment, the gas outlet hole  233 A has a larger hole diameter than the liquid inlet hole  234 A to make it easier for the force of gravity acting on the liquid-state working fluid to serve as a driving force of the gravity-driven gas-liquid circulation device  100 . 
     The fins  22 A are integrally formed on the thermally conductive base  21 A by a relieving means. Each fin  22 A has a thickness ranging from 0.2 mm to 1 mm to facilitate rapid heat exchange with the liquid-state working fluid. The spacing S between each two adjacent fins  22 A forms a flow channel  221 A. The spacing S ranges from 0.2 mm to 1 mm so that the liquid-state working fluid can flow through the flow channels  221 A with ease to carry out heat exchange with the fins  22 A sufficiently. 
     The liquid inlet hole  234 A is in alignment with the flow channels  221 A. The top sides H of the fins  22 A may be higher than the bottom edge, and lower than the top edge, of the liquid inlet hole  234 A or be higher than the top edge of the liquid inlet hole  234 A, the objective being to allow as much liquid-state working fluid as possible to flow through the flow channels  221 A and thereby increase the heat absorption efficiency of the evaporation unit  20 A. 
     The thermally conductive base  21 A is provided thereon with a reinforcement member  24 A. The reinforcement member  24 A is clamped vertically between the integrally formed sealing housing  23 A and the thermally conductive base  21 A and serves to increase the compressive strength, and thereby prevent deformation of, the evaporation unit  20 A. The reinforcement member  24 A is provided with at least one through hole  241 A and at least one aperture  242 A to enable passage of the liquid-state working fluid. Or, the reinforcement member  24 A may have only the through hole(s)  241 A or the aperture(s)  242 A; the present invention has no limitation in this regard. 
     Please refer to  FIG. 9  for a schematic circulation diagram of the gravity-driven gas-liquid circulation device of the present invention. 
     The liquid-state working fluid in the condensation unit  10 A is guided into the evaporation unit  20 A through the liquid phase output tube WT. Meanwhile, the force of gravity acting on the liquid-state working fluid provides a siphoning force such that the gaseous-state working fluid in the evaporation unit  20 A is driven into the condensation unit  10 A through the gaseous phase input tube AT. Thus, the gravity-driven gas-liquid circulation device  100  forms a continuous heat exchange cycle without having to be driven by an electromechanical means. 
     The following paragraphs describe the second preferred embodiment of the condensation unit of the disclosed gravity-driven gas-liquid circulation device. The second embodiment is different from the foregoing embodiment only in the structure of the flow tubes, so the remaining structures of the condensation unit, as well as the evaporation unit, will not be described repeatedly. 
     Please refer to  FIG. 10  to  FIG. 12  respectively for a perspective view of the second embodiment of the condensation unit of the present invention, a sectional view of the front condensation assembly of the condensation unit, and a sectional view of the rear condensation assembly of the condensation unit. 
     As shown in  FIG. 10  to  FIG. 12 , the condensation unit  10 B includes a front condensation assembly  11 B, a rear condensation assembly  12 B, and a plurality of heat dissipation fins  13 B. The front condensation assembly  11 B includes a front left flow tube  111 B, a front right flow tube  112 B, and a plurality of front heat dissipation tubes  113 B in communication with the front left flow tube  111 B and the front right flow tube  112 B. The front left flow tube  111 B and the front right flow tube  112 B are provided on the two opposite lateral sides of the front condensation assembly  11 B respectively and are connected to the gaseous phase input tube and the liquid phase output tube respectively. The front heat dissipation tubes  113 B are vertically spaced apart. The rear condensation assembly  12 B is parallel to the front condensation assembly  11 B and includes a rear left flow tube  121 B, a rear right flow tube  122 B, and a plurality of rear heat dissipation tubes  123 B in communication with the rear left flow tube  121 B and the rear right flow tube  122 B. The rear left flow tube  121 B and the rear right flow tube  122 B are provided on the two opposite lateral sides of the rear condensation assembly  12 B respectively. The rear heat dissipation tubes  123 B are vertically spaced apart. The gaps between the rear heat dissipation tubes  123 B and those between the front heat dissipation tubes  113 B correspond to each other and jointly form a plurality of through grooves GB. 
     The front left flow tube  111 B and the rear left flow tube  121 B are jointly formed by two stamped plates, including an M-shaped stamped plate and a square U-shaped stamped plate. The front right flow tube  112 B and the rear right flow tube  122 B are also jointly formed by an M-shaped stamped plate and a square U-shaped stamped plate. The stamped plates are intended to increase the compressive strength of the flow tubes. The two flow tubes on either lateral side of the condensation unit  10 B are provided with a pair of scaling covers  114 B (one on top and the other at the bottom). The front left flow tube  111 B, the front right flow tube  112 B, the rear left flow tube  121 B, and the rear right flow tube  122 B have an outwardly protruding, (circularly) curved shape on the sides facing diametrically away from the front heat dissipation tubes  113 B or the rear heat dissipation tubes  123 B, in order to allow more efficient use of the space inside the flow tubes. 
     The heat dissipation fins  13 B are inserted in the through grooves GB respectively and extend through the front condensation assembly  11 B and the rear condensation assembly  12 B. The heat dissipation fins  13 B are in contact with the surfaces of the front heat dissipation tubes  113 B and of the rear heat dissipation tubes  123 B so that heat exchange can take place between the heat dissipation fins  13 B and the heat dissipation tubes  113 B and  123 B. The heat dissipation fins  13 B may have a corrugated configuration, a serrated configuration, or any other configuration achievable by bending a metal plate. There are a plurality of microstructures on the surface of each heat dissipation fin  13 B. The microstructures may extend outward or inward with respect to the heat dissipation fins  13 B to increase the area of contact between each heat dissipation fin  13 B and air, thereby enhancing the efficiency of heat dissipation. 
     To enable communication between the front condensation assembly  11 B and the rear condensation assembly  12 B, at least one left opening LO 1  is provided between the front left flow tube  111 B and the rear left flow tube  121 B, and at least one right opening RO 1  is provided between the front right flow tube  112 B and the rear right flow tube  122 B. In this embodiment, there is one left opening LO 1  and one right opening RO 1 , and the two openings are diagonally arranged with respect to each other, wherein the bottom side of the left opening LO 1  is higher than the top side of the right opening RO 1 . It should be pointed out, however, that the openings described above serve only as an example; the present invention imposes no limitation on the number or shapes of those openings. 
     The following paragraphs describe the third preferred embodiment of the condensation unit of the disclosed gravity-driven gas-liquid circulation device. The third embodiment is structurally different from the previous two embodiments, and yet the corresponding evaporation unit is the same as those for use with the foregoing two embodiments (and hence will not be described repeatedly). 
     Please refer to  FIG. 13  and  FIG. 14  respectively for an assembled perspective view and an exploded perspective view of the third embodiment of the condensation unit of the present invention. 
     As shown in  FIG. 13  and  FIG. 14 , the condensation unit  10 C includes a plurality of condensation plate assemblies  11 C and a plurality of heat dissipation fins  12 C. The condensation plate assemblies  11 C are vertically spaced apart. The heat dissipation fins  12 C are inserted between the condensation plate assemblies  11 C and are therefore also spaced apart from one another. Each condensation plate assembly  11 C is provided with a left flow tube  111 C on the left side, a right flow tube  112 C on the right side, and a flow passage  113 C in communication with the left flow tube  111 C and the right flow tube  112 C to allow passage of the gaseous-state working fluid, wherein the left flow tube  111 C and the right flow tube  112 C are connected to the gaseous phase input tube and the liquid phase output tube respectively. 
     Each heat dissipation fin  12 C is inserted between, and in contact with the surfaces of, two adjacent condensation plate assemblies  11 C to enable heat exchange between the heat dissipation fin  12 C and the two condensation plate assemblies  11 C. The heat dissipation fins  12 C may have a corrugated configuration, a serrated configuration, or any other configuration achievable by bending a metal plate. There are a plurality of microstructures on the surface of each heat dissipation fin  12 C. The microstructures may extend outward or inward with respect to the heat dissipation fins  12 C to increase the area of contact between each heat dissipation fin  12 C and air, thereby enhancing the efficiency of heat dissipation. 
     Each condensation plate assembly  11 C is formed by two metal plates P, wherein each metal plate P is provided with a plurality of protruding structures P on the side facing the flow passage  113 C in order to increase the strength of the condensation plate assembly  11 C. The protruding structures P 1  of each metal plate P are formed by stamping the metal plate P and are preferably cylindrical or dome-shaped so that each pair of metal plates P can be soldered together with ease. 
     According to the above, the gas-liquid circulation device disclosed herein uses the force of gravity acting on the liquid-state working fluid to drive the gaseous-state working fluid as well as the liquid-state working fluid to circulate continuously in the device, thereby eliminating the need for an additional electromechanical driving device. 
     The above is the detailed description of the present invention. However, the above is merely the preferred embodiment of the present invention and cannot be the limitation to the implement scope of the present invention, which means the variation and modification according to the present invention may still fall into the scope of the invention.