A two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface

Abstract

The present invention belongs to the technical field of two-phase flow evaporation heat dissipation devices, and particularly relates to a two-phase flow evaporation heat dissipation device based on the impact of a micro-jet gas array on the liquid surface, which includes a housing. A heat dissipation chamber is provided inside the housing, and a thin liquid layer is arranged inside the heat dissipation chamber. A plurality of jet holes located at the upper end of the heat dissipation chamber are provided on the housing, and the lower ends of the jet holes are communicated with the heat dissipation chamber. A ventilation groove communicated with the heat dissipation chamber is provided on the peripheral side of the housing. A retention chamber located at the upper end of the heat dissipation chamber is also provided inside the housing, and the upper ends of the jet holes are communicated with the retention chamber. An air inlet communicated with the retention chamber is provided at the upper end of the housing. The present invention can combine jet cooling and thin liquid film evaporation cooling for two-phase flow cooling, and at the same time give full play to the advantages of the two cooling methods, enabling the liquid to achieve efficient phase change heat transfer at a temperature below the boiling point, creating a high-intensity evaporation heat dissipation environment, and achieving a better heat dissipation effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-phase flow evaporation heat dissipation devices, and particularly relates to a two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on a liquid surface. Background Art

[0002] With the development of microelectronics technology, electronic devices show a development trend of high performance and miniaturization. At the same time, the requirement of electronic devices for heat dissipation capacity is further improved. If the heat generated during operation is not taken away in time, this heat will pose a hazard to the life and stability of the system. At present, the heat flux density on the surface of high-performance chips can already exceed 100 W / cm 2 and will even reach and exceed 1000 W / cm 2 in the future. Traditional air forced convection and single-phase liquid cooling technologies are already difficult to meet such high heat dissipation requirements, and the development of new and efficient heat dissipation technologies has become an important bottleneck restricting the development of microelectronics technology and industry.

[0003] Two-phase flow heat dissipation technology can utilize the latent heat of phase change to achieve a high heat transfer rate at a low temperature difference, and it is an important technology for future high heat flux density heat dissipation. Currently, the mainstream two-phase flow heat dissipation technology is based on the boiling phase change process, which requires the heating surface to reach a temperature above the boiling point. If water is used as the working medium, the chip temperature needs to reach 100 °C, exceeding its normal operating range; if a low-boiling refrigerant is used as the working medium, its latent heat of phase change is usually one order of magnitude lower than that of water, and it is difficult to achieve a heat dissipation density of 100 W / cm 2 . Solving this problem requires creating a high-intensity evaporation heat dissipation environment so that water can achieve efficient phase change heat transfer at a temperature below the boiling point.

[0004] Combined with the existing heat dissipation technologies, the present invention proposes a two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on a liquid surface, that is, using the principle of a microjet array, the air input by the air intake device is divided into multiple tiny airflows through a porous array, and the tiny airflows will vertically impact a thin liquid layer about 1 mm thick below. The thin liquid layer will continuously form a concave liquid surface due to the impact. On the one hand, a continuous evaporation thin liquid film is formed, increasing the phase change heat dissipation capacity; on the other hand, the jet airflow forms a wall jet on the concave surface, enhancing the heat transfer capacity of the impacted area. Summary of the Invention

[0005] The purpose of the present invention is to provide a two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on a liquid surface, which can combine jet cooling and evaporation cooling for two-phase flow cooling, and at the same time give full play to the advantages of the two cooling methods, enabling the liquid to achieve efficient phase change heat transfer at a temperature below the boiling point, creating a high-intensity evaporation heat dissipation environment, and achieving a better heat dissipation effect.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A two-phase flow evaporation heat dissipation device based on the impact of a micro-jet gas array on the liquid surface, comprising a housing. A heat dissipation chamber is provided inside the housing. A thin liquid layer is arranged inside the heat dissipation chamber. A plurality of jet holes located at the upper end of the heat dissipation chamber are provided on the housing. The lower ends of the jet holes are communicated with the heat dissipation chamber. An air exchange groove communicated with the heat dissipation chamber is provided on the peripheral side of the housing.

[0008] Furthermore, a retention chamber located at the upper end of the heat dissipation chamber is also provided inside the housing. The upper ends of the jet holes are communicated with the retention chamber. An air inlet communicated with the retention chamber is provided at the upper end of the housing. The air inlet is provided at a position on the housing above the axis center of the retention chamber.

[0009] Furthermore, a liquid replenishing port communicated with the heat dissipation chamber is provided on the housing.

[0010] Furthermore, the housing includes a bottom plate, an observation window, a jet plate, a hollow cushion layer, and an air inlet plate fixedly connected in sequence from bottom to top. The lower surface of the bottom plate is a heat dissipation surface. The heat dissipation chamber is provided on the observation window. The jet holes are provided on the jet plate. The air exchange groove is provided on the lower side of the jet plate and at a position around the plurality of jet holes. The retention chamber is provided on the hollow cushion layer. The air inlet is provided on the air inlet plate.

[0011] Furthermore, the material of the bottom plate is copper.

[0012] Furthermore, through holes are provided on the observation window, the jet plate, the hollow cushion layer, and the air inlet plate. The through holes opposite to each other on the observation window, the jet plate, the hollow cushion layer, and the air inlet plate form a group. A bolt is threadedly connected inside the through holes of the same group. The observation window can be adhesively bonded to the upper side of the bottom plate through silica gel.

[0013] The technical effect achieved by the present invention is:

[0014] The two-phase flow evaporation heat dissipation device based on the impact of a micro-jet gas array on the liquid surface of the present invention utilizes the micro-jet array principle to divide the incident air flow into multiple tiny air flows through a porous plate and vertically incident on the thin liquid layer. Due to the relatively high air flow velocity, a concave liquid surface array will be formed at the gas-liquid interface. At the same time, the jet fluctuation improves the evaporation cooling effect. Thus, the jet cooling and evaporation cooling can be combined for two-phase flow cooling, and the advantages of both cooling methods can be exerted simultaneously, enabling the liquid to achieve efficient phase change heat transfer at a temperature lower than the boiling point, creating a high-intensity evaporation heat dissipation environment, and achieving a better heat dissipation effect. Description of the Drawings

[0015] Figure 1 is the structural schematic diagram in Embodiment 1 of the present invention;

[0016] Figure 2 It is a schematic cross-sectional structure diagram in Embodiment 1 of the present invention;

[0017] Figure 3 It is an exploded structure diagram in Embodiment 1 of the present invention;

[0018] Figure 4 It is a schematic structure diagram when the jet plate is inverted in Embodiment 1 of the present invention;

[0019] Figure 5 It is a schematic structure diagram in Embodiment 1 of the present invention;

[0020] Figure 6 It is a schematic structure diagram in Embodiment 2 of the present invention;

[0021] Figure 7 It is a schematic principle diagram of the present invention;

[0022] Figure 8 It is an experimental test data diagram in Embodiment 2 of the present invention.

[0023] In the drawings, the list of components represented by each reference numeral is as follows:

[0024] 1. Bottom plate; 2. Observation window; 3. Jet plate; 4. Hollow cushion layer; 5. Air inlet plate; 6. Heat dissipation chamber; 7. Ventilation groove; 8. Jet hole; 9. Retention chamber; 10. Air inlet; 11. Liquid replenishment port; 12. Plate body; 13. Spacer block; 14. Lower bracket; 15. Upper bracket; 16. Bolt body; 17. Platform body; 18. Air compressor; 19. Flow control valve; 20. Flow display; 21. Quick connector; 22. Observation device; 23. Temperature measurement host; 24. Thermocouple temperature measurement wire; 25. Heating tube; 26. Heating copper block; 27. Through hole. Detailed implementation manners

[0025] In order to make the purpose and advantages of the present invention clearer, the present invention will be specifically described below in conjunction with embodiments. It should be understood that the following text only describes one or several specific implementation manners of the present invention, and does not strictly limit the protection scope of the specific claims of the present invention.

[0026] The present invention discloses a two-phase flow evaporation heat dissipation device based on the impact of a micro-jet gas array on the liquid surface. The device uses the principle of the micro-jet array to divide the incident gas flow into multiple tiny gas flows through a porous plate and vertically incident on a thin liquid layer. Due to the relatively high gas flow velocity, a concave liquid surface array will be formed at the gas-liquid interface. At the same time, the jet fluctuation improves the evaporation cooling effect; the two-phase flow cooling by combining jet cooling and evaporation cooling can largely exert the advantages of the two cooling methods and achieve a heat dissipation effect of 1 + 1 > 2. For details, please refer to the following embodiments.

[0027] Embodiment 1:

[0028] As shown in Figures 1-7 , a two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface includes a housing. The lower surface of the housing is a heat dissipation surface in contact with the device to be cooled. A heat dissipation chamber 6 and a retention chamber 9 located at the upper end of the heat dissipation chamber 6 are provided inside the housing. A plurality of jet holes 8 are provided on the housing between the heat dissipation chamber 6 and the retention chamber 9. The plurality of jet holes 8 are preferably arranged in a rectangular array. The upper end of the jet hole 8 is communicated with the retention chamber 9, and the lower end of the jet hole 8 is communicated with the heat dissipation chamber 6, so that the heat dissipation chamber 6 and the retention chamber 9 are communicated through the jet holes 8. When the gas enters the retention chamber 9, the gas inside the retention chamber 9 will enter the inside of the plurality of jet holes 8, and the airflow entering the retention chamber 9 is divided into multiple tiny airflows through the plurality of jet holes 8 and vertically enters the inside of the heat dissipation chamber 6.

[0029] As shown in Figures 1-3 , in order to achieve the purpose of introducing gas into the heat dissipation chamber 6, an air inlet 10 communicated with the retention chamber 9 is provided at the upper end of the housing. The diameter of the air inlet 10 is preferably 5 mm. The air inlet 10 can be communicated with an air delivery device, and the gas output by the air delivery device can directly enter the inside of the retention chamber 9 through the air inlet 10. Moreover, the air inlet 10 can be provided at a position on the housing above the retention chamber 9, and preferably at the upper side of the axis of the retention chamber 9, so that the gas at the air inlet 10 can flow more uniformly to each position inside the retention chamber 9.

[0030] Among them, as shown in Figures 2-3 and Figure 7 , a thin liquid layer is provided inside the heat dissipation chamber 6. The material of the thin liquid layer is a liquid such as water, fluorinated liquid or oil-based coolant, preferably water, and the thickness of the thin liquid layer is preferably 1 mm. Through the setting of the thin liquid layer, evaporative cooling can be carried out on the heat dissipation surface of the housing. In order to achieve the purpose of replenishing liquid into the heat dissipation chamber 6, a liquid replenishing port 11 communicated with the heat dissipation chamber 6 is provided on the housing. The height of the connection between the liquid replenishing port 11 and the heat dissipation chamber 6 is preferably higher than the liquid level height of the thin liquid layer, and liquid can be input into the heat dissipation chamber 6 through the liquid replenishing port 11.

[0031] When the gas at the jet holes 8 enters the heat dissipation chamber 6 at an air flow speed of 5 - 10 m / s, multiple tiny airflows will vertically enter the thin liquid layer. Due to the relatively high air flow speed, a concave liquid surface array will be formed at the gas-liquid interface between the thin liquid layer and the air flow, thus accelerating the evaporation process and significantly improving the effect of evaporative cooling.

[0032] Here, the air flow speed when the gas enters the heat dissipation chamber 6 is preferably 7 m / s.

[0033] Furthermore, the liquid replenishing port 11 is communicated with a pump, and the liquid is pumped into the liquid replenishing port 11 through the pump to reduce the phenomenon of liquid leakage from the liquid replenishing port 11.

[0034] Jet fluctuation is a phenomenon of forming unstable fluctuations by injecting airflows, and it enhances the evaporation cooling effect through jet fluctuation as follows:

[0035] Jet fluctuation enhances the disturbance and flow of the liquid, continuously refreshes the liquid surface, keeps the temperature gradient relatively large, thereby accelerating heat transfer and improving the heat transfer efficiency between the liquid and the air;

[0036] Jet fluctuation can also break the liquid surface to form a large number of small liquid droplets or thin liquid films. The surface area of these tiny liquid droplets or thin liquid films is larger relative to their volume, and the equivalent thermal resistance is lower, thereby increasing the evaporation area and promoting evaporation;

[0037] Jet fluctuation can increase the flow velocity of the liquid, enabling the liquid to be continuously updated during evaporation, which helps to quickly carry away the heat on the liquid surface and improve the cooling efficiency.

[0038] Jet fluctuation can enhance the disturbance of the surrounding air, make the convective heat transfer between the air and the liquid more sufficient, and enable the steam to be transported from the gas-liquid interface to the atmospheric environment more quickly, thereby accelerating the evaporation process.

[0039] As Figures 1-3 shown, a ventilation slot 7 communicating with the heat dissipation chamber 6 is formed on the circumferential side of the housing. Through the ventilation slot 7, the gas inside the heat dissipation chamber 6 can be discharged, reducing the phenomenon of air retention. Moreover, the height of the connection between the ventilation slot 7 and the heat dissipation chamber 6 is higher than the liquid level of the thin liquid layer, and preferably, the upper part of the ventilation slot 7 is connected to the heat dissipation chamber 6.

[0040] The housing can be an integral structure, or it can be as Figure 1 and Figures 3-4As shown in the figure, it is composed of a bottom plate 1, an observation window 2, a jet plate 3, a hollow cushion layer 4, and an air inlet plate 5. Specifically, the housing includes a bottom plate 1, an observation window 2, a jet plate 3, a hollow cushion layer 4, and an air inlet plate 5 that are fixedly connected in sequence from bottom to top. The lower surface of the bottom plate 1 is a heat dissipation surface that contacts the device to be cooled. To improve the heat conduction efficiency, the material of the bottom plate 1 is preferably copper. A heat dissipation chamber 6 is opened on the observation window 2, preferably in the middle area of the observation window 2. Jet holes 8 are opened on the jet plate 3, preferably in the middle area of the jet plate 3. And a ventilation groove 7 is opened in the edge area on the lower side of the jet plate 3, that is, at the position on the lower side of the jet plate 3 and around the periphery of multiple jet holes 8. The height difference between the ventilation groove 7 and the bottom plate 1 is more than 1 cm to reduce the phenomenon of thin liquid layer splashing. A retention chamber 9 is opened on the hollow cushion layer 4, preferably in the middle area of the hollow cushion layer 4. An air inlet 10 is opened on the air inlet plate 5, preferably at the position overlapping the axis of the retention chamber 9 on the air inlet plate 5. At this time, by splitting the housing into multiple plate-like structures such as the bottom plate 1, the observation window 2, the jet plate 3, the hollow cushion layer 4, and the air inlet plate 5, the production difficulty can be effectively reduced.

[0041] The connection methods between the bottom plate 1, the observation window 2, the jet plate 3, the hollow cushion layer 4, and the air inlet plate 5 can be welding, bolt connection, or bonding. This technical solution preferably uses a combination of bolt connection and bonding. Specifically, through holes 27 are opened on the observation window 2, the jet plate 3, the hollow cushion layer 4, and the air inlet plate 5. The through holes 27 on the observation window 2, the jet plate 3, the hollow cushion layer 4, and the air inlet plate 5 that are opposite to each other form a group. Threaded holes are provided on the inner wall of the through holes 27. The through holes 27 in the same group are combined into a threaded hole, so that a bolt can be threadedly connected inside the through holes 27 in the same group, making the observation window 2, the jet plate 3, the hollow cushion layer 4, and the air inlet plate 5 threadedly connected together. The observation window 2 can be adhesively bonded to the upper side of the bottom plate 1 by silicone, and the combination method is relatively simple.

[0042] Among them, as Figure 5 shown, Figure 5 is a schematic structural diagram when the jet plate 3 is inverted. The jet plate 3 includes a plate body 12. The plate body 12 is a square plate. Multiple jet holes 8 are opened on the plate body 12. Blocks 13 are fixedly connected to the lower sides of the four end corners of the plate body 12. The space between adjacent two blocks 13 forms the ventilation groove 7. Through the structural settings of the plate body 12 and the blocks 13, the processing difficulty of the jet plate 3 can be further reduced.

[0043] The working principle of the present invention is as follows: When in use, the incident air flow is transported through the air inlet 10 into the interior of the retention chamber 9. The gas inside the retention chamber 9 will enter into the interior of multiple jet holes 8. The air flow entering the interior of the retention chamber 9 is divided into multiple tiny air flows by the multiple jet holes 8 and vertically enters the interior of the heat dissipation chamber 6;

[0044] When the gas at the jet hole 8 enters the interior of the heat dissipation chamber 6 at a relatively large air flow velocity, multiple tiny air flows will vertically impinge on the thin liquid layer. Due to the relatively large air flow velocity, concave liquid surface arrays will be formed at the gas-liquid interface between the thin liquid layer and the air flow, accelerating the evaporation process and significantly improving the effect of evaporation cooling. Thus, two-phase flow cooling can be carried out by combining jet cooling and evaporation cooling, giving full play to the advantages of both cooling methods, enabling the liquid to achieve efficient phase change heat transfer below the boiling point, creating a high-intensity evaporation heat dissipation environment, and achieving a heat dissipation density of 100 W / cm 2 to achieve a better heat dissipation effect.

[0045] Embodiment 2:

[0046] As Figure 6 shown, on the basis of Embodiment 1, this embodiment further discloses a two-phase flow evaporation heat dissipation device based on the impingement of a micro-jet gas array on the liquid surface. Specifically, the device further includes a heating and measuring device, a fixing device, a gas transmission device, and an observation device 22;

[0047] Among them, the heating and measuring device includes a temperature measuring mainframe 23, a thermocouple temperature measuring wire 24, a heating tube 25, a heating copper block 26, and a platform body 17. The thickness of the platform body 17 is 5 mm. Five grooves with different shapes are provided on the platform body 17, and the groove depth is 5 mm. The heating copper block 26 is fixedly connected inside the groove, and the heating tube 25 is fixedly connected at the axis of the heating copper block 26. The heating tube 25 selects 4 high-purity magnesium tubes with a power of 150 W, an outer diameter of 10 mm, and an L-tube length of 50 mm, which can be connected to a 220V adjustable power supply for heating.

[0048] The temperature measuring mainframe 23 and the heating tube 25 are electrically connected through the thermocouple temperature measuring wire 24. The thermocouple temperature measuring wire 24 adopts an extremely thin TT-K-30-SLE, the thermocouple wire is made of nickel-chromium material, wrapped with a Teflon PFA outer skin, the inner diameter of the thermocouple wire is 0.254 mm, the diameter of the temperature measuring solder joint is less than 0.5 mm, and the temperature resistance range is -40 to 260 °C. Due to the extremely thin diameter of the thermocouple, thermal conductive glue is needed for fixation, and the temperature measuring data can be exported to the computer through the NI board. In this example, disk storage is adopted.

[0049] The fixing device includes a lower bracket 14 and an upper bracket 15. The lower bracket 14 and the upper bracket 15 are connected by multiple bolt bodies 16. At this time, the platform body 17 and the housing are placed between the lower bracket 14 and the upper bracket 15, and the heat dissipation surface of the housing is in close contact with the platform body 17. The parts of the lower bracket 14 and the upper bracket 15 in contact with the heating copper block 26 are covered with heat insulation cotton.

[0050] The gas transmission device includes an air compressor 18, a flow control valve 19, a flow display 20, and a quick connector 21. The air compressor 18, the flow control valve 19, the flow display 20, and the quick connector 21 are sequentially connected through pipelines. The quick connector 21 is connected to the air inlet 10, and the optimal cooling effect can be determined by adjusting the flow control valve 19.

[0051] Specifically, the capacity of the air compressor 18 is 50L. The air compressor 18 uses a dual solenoid valve and has an accurate display of a large pressure gauge. The maximum pressure of the machine is 0.8 Mpa. The flow control valve 19 is made of 304 stainless steel material, with an operating temperature of -20°C to 180°C and an operating pressure below 16 Mpa. It can be adjusted with multiple scales. The flow display 20 adopts a Roots lobe structure and is equipped with a filter screen. The flow range is 0.5 to 16 m 3 / h, and the maximum working pressure is 1 Mpa.

[0052] The observation device 22 includes a microscopic tube lens group, a camera, a fixed tripod, and a recording computer. The observation window 2 is made of a colorless transparent material, and the change of the liquid level can be observed and recorded through the observation device 22 on the side of the observation window 2.

[0053] The gas transmission device inputs compressed air into the air inlet 10 through the quick connector 21. First, it passes through the retention chamber 9, and then is dispersed into multiple small airflows through a plurality of jet holes 8 and vertically incident on the thin liquid layer inside the heat dissipation chamber 6. The change of the liquid level can be observed and recorded through the observation device 22 on the side of the observation window 2. Figure 8 These are the experimental test data of this technical solution.

[0054] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. The structures, devices, and operation methods not specifically described and explained in the present invention, unless otherwise specifically stated and limited, are implemented according to the conventional means in the art.

Claims

1. A two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface, comprising a housing, characterized in that: A heat dissipation chamber (6) is provided inside the housing. A thin liquid layer is arranged inside the heat dissipation chamber (6). The material of the thin liquid layer is a liquid. The thickness of the thin liquid layer is 1 mm. A plurality of jet holes (8) are provided on the housing at the upper end of the heat dissipation chamber (6). The lower ends of the jet holes (8) communicate with the heat dissipation chamber (6). The plurality of jet holes (8) divide the air flow into multiple tiny air flows that vertically impinge on the thin liquid layer, so as to enable the thin liquid layer to transfer heat through phase change at a temperature below the boiling point. A liquid replenishing port (11) communicating with the heat dissipation chamber (6) is provided on the housing, for replenishing liquid inside the heat dissipation chamber (6). Ventilation grooves (7) communicating with the heat dissipation chamber (6) are provided on the peripheral side of the housing, for discharging the gas inside the heat dissipation chamber (6).

2. The two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface according to claim 1, wherein: A retention chamber (9) is further provided inside the housing at the upper end of the heat dissipation chamber (6). The upper ends of the jet holes (8) communicate with the retention chamber (9). An air inlet (10) communicating with the retention chamber (9) is provided at the upper end of the housing.

3. The two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface according to claim 2, wherein: The air inlet (10) is provided on the housing at a position above the axis center of the retention chamber (9).

4. The two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface according to claim 2, wherein: The housing includes a bottom plate (1), an observation window (2), a jet plate (3), a hollow cushion layer (4), and an air inlet plate (5) fixedly connected in sequence from bottom to top. The lower surface of the bottom plate (1) is a heat dissipation surface. The heat dissipation chamber (6) is provided on the observation window (2). The jet holes (8) are provided on the jet plate (3). The ventilation grooves (7) are provided on the lower side of the jet plate (3) and at the position around the plurality of jet holes (8). The retention chamber (9) is provided on the hollow cushion layer (4). The air inlet (10) is provided on the air inlet plate (5).

5. A two-phase flow evaporation heat dissipation device based on a microjet gas array impinging on a liquid surface according to claim 4, characterized in that: The material of the bottom plate (1) is copper.

6. The two-phase flow evaporation heat dissipation device based on the impact of a microjet gas array on the liquid surface according to claim 4, characterized in that: Through holes (27) are provided on the observation window (2), the jet plate (3), the hollow cushion layer (4), and the air inlet plate (5). The through holes (27) opposite to each other on the observation window (2), the jet plate (3), the hollow cushion layer (4), and the air inlet plate (5) form a group. A bolt is threadedly connected inside the through holes (27) of the same group. The observation window (2) can be adhesively bonded to the upper side of the bottom plate (1) through silicone.

7. A two-phase flow evaporation heat dissipation device based on a microjet gas array impinging on a liquid surface according to claim 6, characterized in that: The jet plate (3) includes a plate body (12). The plate body (12) is a square plate. A plurality of jet holes (8) are provided on the plate body (12). Blocks (13) are fixedly connected to the lower sides of the four end corners of the plate body (12).

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