A thermosyphon heat exchanger

Abstract

The present invention provides a thermosyphon heat exchanger, comprising: an evaporator, a riser, a condenser, and a return pipe; the outlet of the evaporator is connected to the inlet of the riser, the outlet of the riser is connected to the inlet of the condenser, the outlet of the condenser is connected to the top of the return pipe, and the liquid of the return pipe is transported downward to the inlet of the condenser; the riser and the return pipe are rectangular tubes; the evaporator is a microchannel evaporator, and fins are arranged on the bottom plate of the microchannel evaporator; the condenser includes at least one flat microchannel tube. Reduce power consumption; maximize the effective area of ​​the condenser, reduce wind resistance, and improve heat dissipation efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of thermosyphon, and in particular to a thermosyphon heat exchanger. Background Art

[0002] Existing cooling elements for microprocessor CPUs in data center servers are essentially (i) air-cooled units or (ii) air-cooled with assistance from heat pipe units. Both types of cooling units can only handle low to medium heat flux loads from the CPU and cannot handle high heat fluxes. They are limited by the extremely high pressure drops and high air flow rates required for operation, both of which cause them to consume a lot of fan power and generate a lot of noise at high fan speeds. Existing thermosyphon heat exchangers are prone to poor thermohydraulic design of the thermosyphon heat exchanger fluid circuit, which creates a large flow resistance, leads to low flow rates, and creates unnecessary flow instabilities; this means that they cannot withstand high heat fluxes and are prone to premature dry-out, causing electronic devices to overheat and start-up erratic.

[0003] In addition, the common use of circular pipes in the riser, return and distributor pipes of existing thermosyphon heat exchangers results in a larger front cross-section, which blocks much of the available surface area for air circulation, resulting in a larger pressure drop, less heat transfer and a larger condenser area, thus limiting lower heat loads. Under the same heat load conditions, the required fan power consumption is also greater. Summary of the invention

[0004] In order to solve the existing problems, the present invention provides a novel thermosyphon heat exchanger.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A thermal syphon heat exchanger comprises: an evaporator, a riser, a condenser and a reflux pipe; the outlet of the evaporator is connected to the inlet of the riser, the outlet of the riser is connected to the inlet of the condenser, the outlet of the condenser is connected to the top of the reflux pipe, and the liquid in the reflux pipe is transported downward to the inlet of the condenser; the riser and the reflux pipe are rectangular tubes; the evaporator is a microchannel evaporator, and fins are arranged on the bottom plate of the microchannel evaporator; the condenser comprises at least one flat microchannel tube.

[0007] Preferably, it includes two thermal siphon circuits: the two thermal siphon circuits share one return pipe, the evaporator and the riser are connected via a microchannel flat tube; the other end of the riser is connected to the flat microchannel tube of the condenser; or, the two thermal siphon circuits share one riser, the evaporator and the return pipe are connected via a microchannel flat tube; the other end of the return pipe is connected to the flat microchannel tube of the condenser.

[0008] Preferably, the microchannel flat tube includes at least two channels and at least one rib is arranged inside the microchannel flat tube.

[0009] Preferably, the condensers of the two thermosyphon circuits are of the same or different sizes.

[0010] Preferably, reinforcing ribs are provided on the side walls and / or the rear wall of the return pipe, or on the inner surface or the outer surface of the side walls and / or the rear wall of the return pipe.

[0011] Preferably, the base plate and the cover plate of the microchannel evaporator form an inlet slit; the geometric shape of the inlet slit is formed by arranging micro-ridges on both sides of the bottom plate of the riser or the return pipe.

[0012] Preferably, a microchannel is formed between the substrate and the cover plate of the evaporator, and support ribs are provided on the substrate and the cover plate; and the ratio of the height to the width of the microchannel is at least 5:1.

[0013] Preferably, the condenser and the evaporator are arranged parallel to each other, perpendicular to each other, or at an angle.

[0014] Preferably, the top plates of the riser and return tubes are flat and in line with the top of the fin area of ​​the condenser.

[0015] Preferably, it also includes at least two microchannel evaporators in horizontal flow mode connected together by microchannel flat tubes, at least two microchannel evaporators in series flow mode, at least four microchannel evaporator arrays in parallel and series combination, or at least two microchannel evaporators in split flow mode.

[0016] The beneficial effects of the present invention are as follows: a thermal siphon heat exchanger is provided, which has a smaller front area than a traditional circular tube by arranging a rectangular riser and return tube, fins on the bottom plate of the microchannel evaporator and a flat microchannel tube in the condenser, so that the surface area of ​​the airflow is larger, and the condenser only needs a lower air flow and a lower pressure drop to exchange heat, thereby reducing the power consumption of the fan; maximizing the effective area of ​​the condenser, reducing wind resistance and improving heat dissipation efficiency.

[0017] Furthermore, the thermosyphon heat exchanger can greatly reduce the flow resistance inside the thermosyphon heat exchanger and greatly increase the flow rate of the working fluid, thereby greatly increasing the heat load and heat flux that the thermosyphon heat exchanger can remove from the electronic equipment.

[0018] Furthermore, an inlet slit with low flow resistance is used to stabilize the flow of the working fluid at the evaporator inlet to prevent flow instability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a loop thermosiphon in the prior art in an embodiment of the present invention.

[0020] FIG. 2( a ) is a partial structural schematic diagram of a thermosyphon heat exchanger according to an embodiment of the present invention.

[0021] FIG. 2( b ) is a schematic diagram of the structure of a microchannel flat tube in an embodiment of the present invention.

[0022] Figure 3(a)-Figure 3(i) Schematic diagram of the structure of the rectangular riser tube in the embodiment of the present invention.

[0023] FIG. 4( a ) is a schematic structural diagram of a dual-circuit thermosyphon heat exchanger having two riser pipes and one return pipe according to an embodiment of the present invention.

[0024] FIG. 4( b ) is a dual-circuit thermosyphon heat exchanger having two return pipes and one riser pipe according to an embodiment of the present invention.

[0025] FIG. 4( c ) is a schematic diagram of the structure of a slit opening in an embodiment of the present invention.

[0026] FIG. 4( d ) is a schematic structural diagram of another slit opening in an embodiment of the present invention.

[0027] FIG. 4( e ) is a schematic diagram of the structure of a single-loop thermosyphon heat exchanger in an embodiment of the present invention.

[0028] Figure 5 It is a structural schematic diagram of a thermosyphon heat exchanger in an embodiment of the present invention.

[0029] FIG. 6( a ) is a partial structural schematic diagram of another thermosyphon heat exchanger according to an embodiment of the present invention.

[0030] FIG6( b ) is a partially enlarged schematic diagram of another thermosyphon heat exchanger according to an embodiment of the present invention.

[0031] FIG6( c ) is a schematic diagram of the structure of another microchannel flat tube in an embodiment of the present invention.

[0032] Figure 7It is a schematic diagram of a side of a double-circuit thermosyphon heat exchanger in an embodiment of the present invention.

[0033] Figure 8(a)-Figure 8(c) Schematic diagram of the structure of the fin in the embodiment of the present invention.

[0034] FIG. 9( a ) is a partial structural schematic diagram of another thermosyphon heat exchanger according to an embodiment of the present invention.

[0035] FIG9( b ) is a schematic structural diagram of another thermosyphon heat exchanger in an embodiment of the present invention.

[0036] Fig.10 Schematic diagram of the structure of the microchannel in the embodiment of the present invention.

[0037] Figure 11(a)-Figure 11(b) It is a structural schematic diagram of another thermosiphon heat exchanger in an embodiment of the present invention.

[0038] Figure 12(a)-Figure 12(f) Schematic diagram of an electronic component to be cooled and a corresponding microchannel evaporator in an embodiment of the present invention.

[0039] Among them, 1-rectangular riser, 2-condenser, 3-rectangular return pipe, 4-microchannel evaporator, 5-horizontal microchannel flat tube riser section, 6-horizontal microchannel flat tube return pipe section, 7-inlet slit of microchannel in evaporator, 8-microchannel flat tube, 9-flat microchannel tube of condenser, 10-bottom plate of riser or return pipe, 11-top plate of riser or return pipe, 12-rear wall of riser, 13-side wall of riser, 14-side wall of return pipe, 15-outlet at the bottom of return pipe, 16-rear wall of return pipe, 17-internal reinforcement rib of riser or return pipe, 18-external reinforcement rib of riser or return pipe, 19-evaporator cover plate, 20-evaporator base plate, 21 - micro ridges, 22 - inlet or outlet area of ​​the evaporator, 23 - micro channels in the evaporator base plate, 24 - fins on the evaporator base plate, 25 - stop cover of the evaporator cover plate, 26 - flat fins, 27 - fins of the shutters, 28 - strip fins,

[0040] 29-gap barrier material, 30-top straight line, 31-support ribs of the evaporator base plate, 32-support ribs of the evaporator cover plate for fixing the fins of the evaporator, 33-rectangular inlet header of the condenser, 34-rectangular outlet header of the condenser, 35-vertical microchannel flat tube riser, 36. Vertical microchannel flat tube return pipe, 37-shorter condenser, 38-longer condenser, 39-short horizontal flat tube riser section with microchannel, 40-long horizontal flat tube riser section with microchannel, 41-evaporator cooling surface, 42-electrical components to be cooled, 43-microchannel evaporator in parallel flow mode, 44-series flow microchannel evaporator, 45-an array of 4 microchannel evaporators in parallel and series combination, 46-two microchannel evaporators in split mode, 47-two microchannel evaporators in split mode. DETAILED DESCRIPTION

[0041] In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit connection.

[0043] It should be understood that the terms "length", "width", "upper", "lower", "front",

[0044] "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inside",

[0045] The orientation or positional relationship indicated by “outside” and the like is based on the orientation or positional relationship shown in the drawings and is only for the convenience of describing the embodiments of the present invention and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0047] like Figure 1 As shown, a schematic diagram of a loop thermosyphon heat exchanger in the prior art. The thermosyphon heat exchanger consists of an evaporator, a riser, a condenser, a return pipe, etc. The liquid working fluid inside is partially evaporated into steam after being heated in the evaporator to take away the heat from the electronic device. The outlet of the evaporator is connected to the riser, which is a microchannel pipe, and the vapor flows upward to the inlet of the condenser. The condenser releases heat from the two-phase flow by condensing the vapor back to the liquid phase. The outlet of the condenser is connected to the top of the return pipe, which is a pipe that transports the liquid downward back to the inlet of the condenser. The flow circulation in the figure is counterclockwise, and the gravity direction is downward. Compared with the liquid flow in the return pipe, the density of the liquid and vapor two-phase flow in the riser is lower, which leads to pressure imbalance, causing the two-phase working fluid to passively flow upward. In addition, due to the influence of gravity in the heat exchanger, the liquid flows downward, thereby forming a continuous flow cycle inside the thermosyphon heat exchanger.

[0048] like Figure 2(a)-Figure 2(b) As shown, the present invention provides a partial schematic diagram of a thermosyphon heat exchanger, including an upflow pipe 1, a condenser 2, a return pipe 3, and the left part of the double-cycle thermosyphon heat exchanger of the evaporator, wherein the split flows to the left and right loops of the separator; and also includes a cross-sectional view of a microchannel evaporator 4, a horizontal microchannel flat tube upflow pipe section 5, and a microchannel flat tube 8. Compared with the circular tube in the prior art, the horizontal microchannel flat tube upflow pipe section 5 reduces the front area, and under the same space conditions, the front area of ​​the condenser 2 is allowed to be increased. The microchannel flat tube 8 is made as large as possible to reduce the flow resistance and thus increase the thermosyphon circulation flow. The internal ribs of the microchannel in the horizontal microchannel flat tube upflow pipe section 5 are used to reinforce the microchannel flat tube 8 to prevent the microchannel flat tube 8 from being deformed by the working fluid. If the internal pressure is higher or lower than the external atmospheric pressure, if there are no ribs, the microchannel flat tube 8 will be deformed.

[0049] like Figure 3(a)-Figure 3(i) 3(a) and 3(b) are respectively the top view and the side view of the rectangular riser. One end of the rectangular riser 1 is connected to one or more flat microchannel tubes 9 of the condenser 2, and the other end is connected to the horizontal microchannel flat tube riser section 5. The rectangular riser 1 includes a bottom plate 10, a top plate 11, a rear wall 12 and a side wall 13. Figure 3(c)-Figure 3(f)3(c) and 3(e) are respectively a top view and a side view of a rectangular return pipe, one end of the rectangular return pipe 3 is connected to one or more flat microchannel pipes 9 of the condenser 9, and the other end is connected to the horizontal flat pipe return pipe section 6. The rectangular return pipe 3 is composed of a bottom plate 10, a top plate 11, a rear wall 16 and a side wall 14, and has an opening 15 for fluid inlet and outlet at the bottom or lower part. FIG. 3(c) and FIG. 3(e) are double-loop thermosyphon heat exchangers, and FIG. 3(d) and FIG. 3(f) are single-loop thermosyphon heat exchanger flows. As shown in FIG. 3(g) and FIG. 3(h), internal reinforcing ribs 17 and external reinforcing ribs 18 can be provided on the inner surface or outer surface of one or more pipe walls, such as the rear wall 12 of the riser, the side wall 13 of the riser, the side wall 14 of the return pipe, and the rear wall 16 of the return pipe. The height of the internal reinforcing ribs 17 and the external reinforcing ribs 18 is less than 1 mm to enhance their strength and resist the internal pressure of the medium and high pressure working fluid or vacuum.

[0050] As shown in Figures 4(a) and 4(b), there are a dual-circuit thermosyphon heat exchanger with two risers and one return pipe, and a dual-circuit thermosyphon heat exchanger with two return pipes and one riser pipe, respectively. The rectangular shape of the riser 1 and the return pipe 3 allows the fluid to enter the tube wall through the horizontal microchannel flat tube riser section 5 and the horizontal microchannel flat tube return pipe 6 without pouring into the interior thereof. There are no protrusions in the riser and return pipes, which would interfere with the fluid flow in the riser and return pipes and disrupt the smooth flow of the fluid in and out of the condenser flat microchannel tubes. The circulation flow rate of the working fluid in the thermosyphon heat exchanger will increase by 25% or more. The front area of ​​the rectangular riser 1 and return pipe 3 in the air flow direction is more than 25% smaller than that of the circular riser. Therefore, Figures 2 and Figure 4(a)-Figure 4(b) The front width of the middle condenser 2 is greater, which increases the available heat transfer surface area, reduces wind speed to reduce pressure drop of the air flow, thereby reducing fan power consumption by 25% or more and making the device very compact.

[0051] As shown in FIG4(b), in a dual-circuit thermosyphon heat exchanger with two return pipes and one riser pipe, the fluid enters the microchannel evaporator 4 from the top or side through the inlet slit 7 formed by the evaporator base plate 20 and the evaporator cover plate 19.

[0052] As shown in FIG4(c), there is a single circulation flow from one end to the other end of the microchannel evaporator 4, or there is a double circulation flow; wherein the fluid from the return pipe 3 enters the middle of the top cover plate 19 and is split through the riser pipes 1 at both ends, or the fluid from the two return pipes 3 enters the microchannel evaporator 4 from both ends and stays at the bottom of the riser pipe 1 from the middle of the top cover plate 19. The inlet flow into the evaporator is stabilized by the inlet slit 7, which can also realize the flow distribution to multiple microchannel tubes and prevent the steam from flowing back into the return pipe 3.

[0053] As shown in FIG. 4( d ), the geometry of the inlet slit 7 may provide micro-ridges 21 on both sides of the bottom plate 10 to prevent the brazing or soldering material from flowing into the slit and blocking the narrow slit during the manufacturing process.

[0054] As shown in FIG. 4( e ), for a single-loop thermosyphon heat exchanger, the length of the horizontal microchannel flat tube riser section and the horizontal microchannel flat tube return tube section 6 is shortened or lengthened depending on the location and size of the electronic equipment to be cooled.

[0055] like Figure 5 As shown, although the return pipe 3 or the riser pipe 1 is usually located in the center, it can be moved to an eccentric position, which is determined by the position of the electronic components to be cooled in the electronic package. In this case, the position of the evaporator is moved to be consistent with the electronic equipment to be cooled, and the condenser 37 with a shorter width corresponds to the short horizontal flat tube riser section 39 with microchannels, and the condenser 38 with a longer width corresponds to the long horizontal flat tube riser section 40 with microchannels.

[0056] Figure 6(a)-Figure 6(c) As shown, the horizontal microchannel flat tube riser section 5 and the horizontal microchannel flat tube return tube section 6 are connected to the outlet and inlet area 22 of the microchannel evaporator 4, and a microchannel flat tube 8 is arranged inside. The microchannel evaporator 4 includes a microchannel 23, a fin 24 is arranged on the bottom plate of the evaporator, and a cut-off cover 25 is arranged on the evaporator cover. Compared with the traditional circular tube section, the horizontal microchannel flat tube riser section 5 and the horizontal microchannel flat tube return tube section 6 are used to improve the transmission of the working fluid from the outlet of the microchannel evaporator 4 to the bottom inlet of the riser 1. By setting cross sections with the same shape, width and height at the outlets of multiple microchannels in the microchannel evaporator 4 and at the inlet of the riser 1, the pressure drop is reduced and the thermal siphon circulation flow rate is increased. Similarly, the same arrangement can be applied between the outlet of the return tube shown in Figure 2 and the inlet of the microchannel evaporator 4. This arrangement reduces the flow resistance by at least 20%, increases the thermal efficiency of the flow circulation thermal siphon heat exchanger, and can dissipate at least 20% of the heat flux.

[0057] like Figure 7 As shown, it is a side of a dual-loop thermosyphon heat exchanger, showing a condenser 2, a microchannel evaporator 4, a riser 1, a return pipe 3 and a horizontal microchannel flat tube riser section 5. The height, width and depth of the condenser 2 are variable (not shown), so its size can be changed to suit the needs of different electronic products to be cooled. The height, width and length of the microchannel evaporator 4 are variable (not shown) to adapt to the size of the electronic components to be cooled. In order to adapt to the size changes of the condenser 2 and the microchannel evaporator 4, the size of the horizontal microchannel flat tube riser section 5 is also variable, and the size of the horizontal microchannel flat tube return pipe section 6 can also be adaptively changed.

[0058] like Figure 8(a)-Figure 8(c) As shown, three different types of fins are used in the condenser 2: flat plate fins 26 with or without serrations, louvered fins 27 and strip fins 28. One of these three types of fins or a combination of any two or all three can go into the same condenser 2. The fin type is that the fins are brazed between the flat microchannel tubes 9 in the condenser. The fins and their combination in the condenser are selected to provide the most appropriate solution to meet the requirements of volumetric air flow, air pressure drop and fan energy consumption.

[0059] The width of the flat microchannel tubes 9 in the condenser and the width of the strip fins 26, the louvered fins 27, and the flat fins 28 can be changed from 25 mm to more than 100 mm to provide additional heat transfer surface area for cooling the condenser 2. The design of the present invention can use condensers of various sizes and microchannel evaporators 4 adapted to the size of the condenser without size restrictions. The thermosyphon heat exchanger of the present invention has a very versatile basic shape that can be easily modified to adapt to many applications and reduce manufacturing costs.

[0060] like Figure 9(a)-Figure 9(b) As shown, the top plates of the riser 1 and return 3 are flat and in line 30 with the top of the fin area of ​​the condenser 2, thereby blocking any bypass air. If necessary, air blocking material is placed on the top of the condenser 2 to establish the duct boundary. Air blocking material 29 is placed below the condenser 2, above and below the horizontal microchannel flat tube riser section 5, above and below the horizontal microchannel flat tube return section 6 (not shown), and beside the microchannel evaporator 4 to prevent air from entering.

[0061] like Fig.10As shown, a microchannel 23 is formed between the evaporator cover plate 19 and the evaporator substrate 20. In order to use the microchannel evaporator 4 for high-pressure working fluid and prevent the evaporator cover plate 19 and the evaporator substrate 20 from being adversely deformed when the evaporator cover plate 19 and the evaporator substrate 20 are subjected to a large internal pressure of the working fluid in the fin area, a support rib 31 fixed on the evaporator cover plate 19 and a support rib 32 of the evaporator cover plate fixed on the evaporator substrate 20 are provided, and the support ribs 31 and the support ribs 32 are formed by brazing. The fins 24 on the evaporator bottom plate are used to form the microchannel 23, and the evaporator cover plate 19 is the top of the microchannel. The ratio of the height to the width of the microchannel is at least 5:1, so that the ratio of the heat transfer surface area on the bottom surface of the evaporator substrate 20 to the heating bottom area is at least 5:1, and compared with a square channel or a low aspect ratio channel of the same channel width, the flow resistance is greatly reduced by more than 50%, and the thermosyphon heat exchanger is allowed to achieve a higher thermosyphon circulation flow rate, so that at least 25% of the heat flux is cooled. In one embodiment of the present invention, the number and size of the internal heat sinks are variable to accommodate application requirements and the selection of different working fluids.

[0062] As shown in FIG11( a ), a schematic diagram when the electronic device to be cooled is perpendicular to the thermosyphon heat exchanger. In this case, the condenser 2 is placed above the microchannel evaporator 4 and oriented vertically as shown in FIG11 , the condenser rectangular inlet header 33 is at the top, the condenser rectangular outlet header 34 is at the bottom and in a horizontal direction, the vertical microchannel flat tube riser 35 connects the outlet of the microchannel evaporator 4 to the rectangular inlet header 33, and the vertical microchannel flat tube return pipe 36 connects the outlet header 34 to the inlet of the microchannel evaporator 4. The flat microchannel tube 9 is oriented vertically in the condenser 2. Depending on the available space, the rectangular outlet header 34 can be above or below the top of the microchannel evaporator 4.

[0063] As shown in FIG. 11( b ), the condenser 2 is placed horizontally, with a rectangular inlet header 33 of the condenser disposed on one side and a rectangular outlet header 34 of the condenser disposed on the other side, and both are placed vertically. The vertical microchannel flat tube riser 35 connects the outlet of the microchannel evaporator 4 to the rectangular inlet header 33, and the vertical microchannel flat tube return pipe 36 connects the rectangular outlet header 34 to the inlet of the microchannel evaporator 4. In this case, the flat microchannel tube 9 is oriented horizontally in the condenser 2.

[0064] Optionally, the condenser 2 is oriented at an angle between vertical and horizontal, and the condenser rectangular outlet header 34 is below the condenser rectangular inlet header 33. The dual-loop thermosyphon heat exchanger in FIG. 4(b) or FIG. 4(d) can be used to cool the vertical electronic surface in FIG. 11(a) by simply adjusting the positions of the riser 1, the return pipe 3, the vertical microchannel flat tube riser 35 and the vertical microchannel flat tube return pipe 36, the condenser rectangular inlet header 33 and the rectangular outlet header 34.

[0065] like Figure 12(a)-Figure 12(f) As shown, two or more electronic components 42 are cooled side by side, front and back, and adjacent to each other on the evaporator cooling surface 41. The electronic components 42 can have the same size or different sizes. Fig.10 As shown, the thermosyphon heat exchanger cools these components through an evaporator cooling surface 41 with microchannels 23, wherein the thermosyphon heat exchanger can be Figure 4(a)-Figure 4(d) Single-loop or dual-loop configuration as shown. In FIG12, in order to cool multiple electronic components, the thermosyphon heat exchanger can also utilize two or more microchannel evaporators 43 in parallel flow mode connected together by circular tubes or microchannel flat tubes 8, two (or more) series flow microchannel evaporators 44, 4 (or more) microchannel evaporator arrays 45 in parallel and series combination, two microchannel evaporators 46 in split mode, and two microchannel evaporators 47 in split mode. Each one or more of these microchannel evaporators is used to cool the electronic component 42 to be cooled. Multiple evaporators can be connected to the thermosyphon flow loop with a series flow microchannel evaporator 44, or they can be connected to the thermosyphon flow loop with a microchannel evaporator 43 in parallel flow mode.

[0066] The present invention proposes a new and more compact thermosyphon heat exchanger, which significantly reduces the flow resistance of the fluid flow loop inside the thermosyphon heat exchanger and increases the effective heat exchange fin area at the front of the air flowing into the condenser, thereby greatly improving the heat load and heat flux that can be removed when a given limited height between the condenser and the evaporator is given (usually less than 90mm). In particular, the front rectangular riser and return tube are only about half the front area of ​​the traditional circular riser, which makes the surface area of ​​the airflow larger (increased by 20-40%), and the larger condenser surface area can exchange heat with lower air flow and lower pressure drop, thereby significantly reducing fan power consumption (reduced by 20-90%). The distribution pipe from the evaporator outlet to the bottom of the riser is also changed from a circular tube (with a larger front surface area) to a flat tube with internal microchannels (with higher mechanical strength) and a larger front area. In addition, the novel thermosyphon heat exchanger can be changed from a single circulation flow loop to two circulation loops running in parallel with a common central return pipe, or having a common central riser and two parallel return pipes; the use of two parallel flow loops can greatly reduce the flow resistance inside the thermosyphon heat exchanger and greatly increase the flow rate of the working fluid, thereby greatly increasing the heat load and heat flux that the thermosyphon heat exchanger can remove from the electronic equipment. In addition, a narrow slit with low flow resistance is used to stabilize the flow of the working fluid at the evaporator inlet to prevent flow instability.

[0067] The thermosyphon heat exchanger proposed in the present invention has improved performance to handle higher heat fluxes and reduce the energy consumption for cooling its condenser. First, rectangular riser and return tubes have been developed to reduce their front area relative to the circular front tubes in the prior art, thereby increasing the front area of ​​the condenser used to cool the air flow; second, a microchannel flat tube with internal ribs is proposed for connecting the evaporator to the riser and return tubes; third, a new type of evaporator is proposed in which the inlet slit of the microchannel is located at the inlet of each microchannel in the microchannel evaporator to stabilize the flow and prevent vapor bubble backflow; fourth, a dual-circuit thermosyphon heat exchanger is proposed, in which two thermosyphon circuits are connected together to form a fluid system by sharing a return tube or a riser. All of these have two common goals:

[0068] (i) increasing the flow rate in the thermosyphon heat exchanger to increase the level of heat flux that can be dissipated by the evaporator;

[0069] (ii) Increasing the cooling capacity of the condenser so that cooling can be accomplished with a lower fluid volume, thereby reducing the power consumption of the fan.

[0070] The thermosyphon heat exchanger for cooling electronic products provided by the present invention is composed of a microchannel evaporator, the microchannel evaporator is connected to one or more rectangular riser tubes, the riser tubes are connected to one or more condensers, the condensers are connected to one or more rectangular return tubes and connected to the inlet of the microchannel evaporator. The rectangular cross-sectional shape of the riser tube and the return tube replaces the conventional circular shape, and the internal volume is small, so that the mass of the working fluid required for the operation of the thermosyphon cooling system is reduced by 25% or more; relative to the circular riser tube and the return tube, the rectangular shape can also reduce its front end area by 25% or more, which allows the width of the condenser to be much larger to increase the air flow, increase the surface area (s) of the condenser or reduce the flow resistance of the air through the condenser, thereby reducing the air consumption power of the fan. The vertical riser (or return pipe) may also include an inlet (or outlet) microchannel flat tube between the outlet (or inlet) of the evaporator. The shape of the microchannel flat tube is narrow in the front area compared with the circular tube, which can increase the front area of ​​the condenser, but is wider in the airflow direction, so as not to increase the flow resistance of the internal working fluid, while the horizontal microchannel flat tube may have one or more channels inside, and may also be provided with multiple internal reinforcing ribs to withstand the internal pressure of the working fluid. The microchannel flat tubes constituting the condenser are welded to the rectangular riser and return pipes, and because of the setting of the limit step, they will not protrude inside them like the traditional condenser, which makes the flow resistance inside the riser and return pipes smaller. Therefore, the flow rate of the working fluid of the thermosyphon heat exchanger is increased by more than 25%. There is a very low flow resistance and low pressure drop resistance in the evaporator, condenser, riser and return pipes and at the connection between these components to achieve thermosyphon flow, thereby increasing the thermosyphon flow rate by 25% or more. The increase in the thermosyphon flow rate reduces the outlet vapor ratio leaving the evaporator, thereby avoiding the burn-out condition. Furthermore, higher thermosyphon circulation flow rates increase the heat load and heat flux removed between the condenser and evaporator at a given height for gravity driven flow by more than 25%. In addition, the single circulation flow loop in a thermosyphon heat exchanger can be altered to operate two circulation loops in parallel with a common return leg or a common riser leg.

[0071] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art of the present invention, several equivalent substitutions or obvious variations can be made without departing from the concept of the present invention, and the performance or use is the same, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A thermosyphon heat exchanger, characterized in that: include: Evaporator, riser, condenser, reflux pipe; The outlet of the evaporator is connected to the inlet of the riser, the outlet of the riser is connected to the inlet of the condenser, the outlet of the condenser is connected to the top of the reflux pipe, and the liquid in the reflux pipe is transported downward to the inlet of the condenser; The rising pipe and the return pipe are rectangular pipes; the evaporator is a microchannel evaporator, and fins are arranged on the bottom plate of the microchannel evaporator; the condenser includes at least one flat microchannel pipe.

2. The thermosyphon heat exchanger according to claim 1, characterized in that: It comprises two thermosiphon circuits: the two thermosiphon circuits share one return pipe, the evaporator and the riser are connected via a microchannel flat tube; the other end of the riser is connected to the flat microchannel tube of the condenser; Alternatively, the two thermosiphon circuits share one riser pipe, the evaporator is connected to the return pipe via a microchannel flat tube; the other end of the return pipe is connected to the flat microchannel tube of the condenser.

3. The thermosyphon heat exchanger according to claim 2, characterized in that: The microchannel flat tube includes at least two channels and at least one rib is arranged inside the microchannel flat tube.

4. The thermosyphon heat exchanger according to claim 2, characterized in that: The condensers of the two thermosyphon circuits may be of the same or different sizes.

5. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: Reinforcing ribs are provided on the inner surface or outer surface of the side wall and / or rear wall of the return pipe and the side wall and / or rear wall of the riser pipe.

6. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: The base plate and the cover plate of the microchannel evaporator form an inlet slit; the geometric shape of the inlet slit is formed by arranging micro-ridges on both sides of the bottom plate of the riser or the return pipe.

7. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: A microchannel is formed between the substrate and the cover plate of the evaporator, and support ribs are arranged on the substrate and the cover plate; the ratio of the height to the width of the microchannel is at least 5:

1.

8. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: The condenser and the evaporator are arranged parallel to each other, perpendicular to each other or at an angle.

9. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: The top plates of the riser and return tubes are flat and in line with the top of the fin area of ​​the condenser.

10. The thermosyphon heat exchanger according to any one of claims 1 to 4, characterized in that: It also includes at least two microchannel evaporators in horizontal flow mode connected together by microchannel flat tubes, at least two series flow microchannel evaporators, at least four microchannel evaporator arrays in parallel and series combination, or at least two microchannel evaporators in split flow mode.

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