Chassis structure based on phase change heat dissipation and heat transfer resistance calculation method

Abstract

The invention discloses a case structure based on phase change heat dissipation and a heat transfer resistance calculation method, and the method comprises the steps: forming a complete gas-liquid two-phase flow channel through the design of a liquid inlet flow channel, a cooling channel in an upper cold plate, and a gas return flow channel in a lower cold plate; the heat-conducting fins arranged on the upper cold plate and the lower cold plate are in contact with the board card to realize heat exchange; the problems that an air-cooled case highly depends on air duct layout and is high in noise during heat dissipation of the cabinet, and a liquid-cooled case has liquid leakage risk and is easy to burn down equipment are solved. The special-shaped fins of the cold plate form an open channel, so that two-phase medium gas-liquid flows in a layered manner, the flow resistance is reduced, local evaporation drying is avoided, the flow distribution in the channel is more uniform, and the flow stability is enhanced; a bionic channel formed by the special-shaped fins enhances gas-liquid disturbance, destroys a gas-liquid boundary layer, lowers a boiling starting point and strengthens boiling heat exchange. According to the method for calculating the heat transfer resistance of the case, the size parameters under different working conditions can be rapidly determined, so that the heat transfer performance of the subrack is optimized, and rapid iterative optimization design is formed.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology for electronic devices, specifically relating to a chassis structure based on phase change heat dissipation and a method for calculating thermal resistance. Background Technology

[0002] In rack-level heat dissipation, air cooling is highly dependent on airflow layout and generates significant noise, while liquid cooling uses conductive working fluids that can easily burn out equipment in case of leakage. To address the heat dissipation requirements of VPX rack enclosures, a two-phase heat exchanger is designed using phase change heat transfer technology to achieve efficient heat dissipation for VPX enclosures. This avoids the problems of air cooling being highly dependent on airflow layout and generating significant noise, as well as the problem of liquid cooling easily burning out equipment in case of leakage. At the same time, it can reduce power consumption, save space, and further improve the integration of the rack.

[0003] Invention patent CN201610586414.6 discloses a high-efficiency heat dissipation device and method for a liquid-cooled VPX chassis based on a heat spreader. The heat spreader is used to conduct the heat of the VPX board to the liquid cooling plate, which effectively solves the heat dissipation requirements of high heat flux density boards. However, this invention proposes a liquid-cooled chassis and does not design for two-phase flow, so it cannot enhance the phase change heat transfer capacity and reduce flow resistance. Furthermore, this invention does not explain the calculation method for the height of the heat-conducting fins, one of the key parameters of chassis design. Utility model patent CN202221887400.5 discloses an improved chassis structure based on VPX heat conduction. By setting a heat dissipation surface, the width of the VPX module is widened, increasing the contact area between the heat pipe and the heat sink, thereby increasing the heat transfer area, shortening the heat conduction path from the heat-generating element to the chassis airflow, greatly reducing the thermal resistance from the device to the heat sink, improving heat conduction efficiency, and improving the heat dissipation effect of the chassis. However, this invention focuses on reducing the thermal resistance from the heat-generating element to the chassis airflow. The chassis is still an air-cooled chassis and is not designed for two-phase flow. Furthermore, this invention does not explain the calculation method for contact thermal resistance, one of the key parameters of chassis design. Summary of the Invention

[0004] This invention provides a chassis structure and a method for calculating thermal resistance based on phase change cooling. By designing a liquid inlet channel, cooling channels within the upper and lower cooling plates, and a return airflow channel, a complete gas-liquid two-phase flow channel is formed. Heat-conducting fins on the upper and lower cooling plates contact the circuit boards to achieve heat exchange. This addresses the problems of air-cooled chassis being highly dependent on airflow layout and generating significant noise, and liquid-cooled chassis posing a risk of leakage and equipment burnout. The trapezoidal fins (irregular fins) inside the chassis cooling plates form open microchannels, enabling stratified gas-liquid flow, reducing flow resistance, preventing localized drying, and providing more uniform flow distribution within the channels, thus enhancing flow stability. Symmetrically distributed fins form biomimetic microchannels, enhancing disturbance, disrupting the gas-liquid boundary layer, lowering the boiling initiation point, and strengthening boiling heat transfer. The combination of open microchannels and biomimetic microchannels achieves efficient heat exchange within the two-phase chassis. The chassis thermal resistance calculation method provided by this invention can quickly determine dimensional parameters under different operating conditions, thereby optimizing the heat transfer performance of the chassis and enabling rapid iterative optimization design.

[0005] To achieve the above-mentioned technical objectives, the present invention is implemented through the following technical solution:

[0006] A chassis structure based on phase change heat dissipation includes an upper cooling plate, a left side plate, a right side plate, a lower cooling plate, heat-conducting fins, a liquid inlet channel, a return channel, and a circuit board. The upper, left, right, and lower cooling plates are fixedly connected to form the chassis shell. Heat-conducting fins are arranged on the opposite surfaces of the upper and lower cooling plates. The upper and lower ends of the circuit board are mounted in the heat-conducting fins, and heat exchange occurs between the circuit board and the heat-conducting fins. Electronic components to be cooled are mounted on the circuit board. The liquid inlet channel and return channel are located on the left side plate and communicate with the cooling channels inside the upper and lower cooling plates. The coolant enters from the liquid inlet channel on the left side plate, flows into the cooling channels inside the upper and lower cooling plates, traverses the entire cooling channel, exchanges heat with the circuit board through the heat-conducting fins, and then flows out from the return channel.

[0007] A method for calculating the thermal resistance of a chassis structure based on phase change heat dissipation, comprising the following steps:

[0008] Step 1: Calculate the internal thermal resistance of the circuit board based on its height, width, thickness, and thermal conductivity.

[0009] Step 2: Determine the economic ratio of the contact thermal resistance between the heating plate and the heat-conducting fins to the internal heat transfer thermal resistance of the heating plate based on design requirements.

[0010] Step 3: Calculate the height of the thermal fins based on the internal thermal resistance, thermal resistance ratio, length of the thermal fins, thermal conductivity of the thermal grease, and thickness of the thermal grease.

[0011] Step 4: Calculate the internal thermal resistance of the heat-conducting fins based on their height, length, and thickness.

[0012] Step 5: Calculate the internal thermal resistance of the cold plate substrate based on the thermal conductivity of the cold plate, the spacing between the thermally conductive fins, and the fin length.

[0013] Step 6: Calculate the phase change convection heat transfer resistance based on the phase change heat transfer coefficient inside the cold plate and the contact area between the phase change fluid and the wall of the cold plate channel.

[0014] Step 7: Based on the calculation results of Steps 1-6, obtain the heat transfer resistance from the circuit board to the phase change fluid inside the chassis.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) The present invention forms a complete gas-liquid two-phase flow channel through the design of the liquid inlet channel, the cooling channel inside the upper and lower cold plates and the return flow channel; the heat-conducting fins set on the upper and lower cold plates contact the circuit board to achieve heat exchange; it solves the problems that air-cooled chassis are highly dependent on the air duct layout and have large noise when the cabinet is dissipating heat, and liquid-cooled chassis have the risk of leakage and easy to burn out equipment.

[0017] (2) In the chassis structure based on phase change heat dissipation of the present invention, the internal cooling channel of the cold plate is formed by combining trapezoidal ribs and symmetrically distributed ribs to form irregular ribs. The open channel formed allows the two-phase medium gas and liquid to flow in layers, reducing flow resistance, avoiding local evaporation, and the flow distribution inside the channel is more uniform, enhancing flow stability. At the same time, the biomimetic channel formed by the irregular ribs can enhance gas-liquid disturbance, destroy the gas-liquid boundary layer, reduce the boiling initiation point, and enhance boiling heat transfer.

[0018] (3) The chassis structure and thermal resistance calculation method based on phase change heat dissipation of the present invention can quickly determine the chassis size parameters under different working conditions, thereby optimizing the heat transfer performance of the chassis and forming a rapid iterative optimization design.

[0019] Instruction manual illustrations

[0020] Figure 1 This is a schematic diagram of the phase change heat dissipation chassis structure of the present invention.

[0021] Figure 2 This is a front view of the phase change heat dissipation chassis of the present invention, wherein (a) is a schematic diagram of the overall structure and (b) is an enlarged structural view.

[0022] Figure 3 This is a left view of the phase change heat dissipation chassis of the present invention.

[0023] Figure 4 This is a cross-sectional view of the upper cold plate of the phase change heat dissipation chassis of the present invention.

[0024] Figure 5 This is a cross-sectional view of the lower cooling plate of the phase change heat dissipation chassis of the present invention.

[0025] Figure 6 This is a longitudinal sectional view of the phase change heat dissipation chassis of the present invention. (a) is an overall schematic diagram, and (b) is an enlarged schematic diagram.

[0026] Figure 7 This is a longitudinal sectional view of the liquid inlet and return flow channels of the phase change heat dissipation chassis of the present invention.

[0027] Figure 8 This is a flowchart of the phase change heat dissipation chassis fin height calculation method of the present invention.

[0028] Figure 9 This is a diagram showing the relationship between the thickness of the thermal grease and the tightening torque according to the present invention.

[0029] Among them, 1. Upper cooling plate; 2. Left side plate; 3. Right side plate; 4. Lower cooling plate; 5. Thermal fins; 6. Liquid inlet channel; 7. Return channel; 8. Plate; 9. Locking strip; 10. Thermal grease; 101. Shaped ribs; 102. Microchannels; 103. Reinforcing ribs; 104. Capillary layer; 401. Shaped ribs; 402. Microchannels; 403. Reinforcing ribs; 404. Capillary layer. Detailed Implementation

[0030] To illustrate the technical solution and objectives of this invention, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] Combination Figures 1-9 A chassis structure based on phase change heat dissipation includes an upper cooling plate 1, a left side plate 2, a right side plate 3, a lower cooling plate 4, heat-conducting fins 5, a liquid inlet channel 6, a return channel 7, a circuit board 8, a locking strip 9, and thermal grease 10.

[0032] The upper cold plate 1, left side plate 2, right side plate 3, and lower cold plate 4 are fixedly connected to each other to form the outer shell of the chassis.

[0033] Heat-conducting fins 5 are provided on the upper cooling plate 1 and the lower cooling plate 4. Both the upper and lower ends of the board 8 are set in the heat-conducting fins 5. Electronic components to be dissipated are installed on the board 8. The liquid inlet channel 6 and the return channel 7 are set on the left side plate 2 and are connected to the cooling channels inside the upper cooling plate 1 and the lower cooling plate 4. The cooling medium enters from the liquid inlet channel 6 on the left side plate 2, flows into the cooling channels inside the upper cooling plate 1 and the lower cooling plate 4, traverses the entire cooling channels inside the upper cooling plate 1 and the lower cooling plate 4, and flows out from the return channel 7.

[0034] Preferably, thermal grease 10 is applied between the board 8 and the thermal fins 5 and fixed in place by locking strips 9.

[0035] Preferably, the locking bar 9 consists of a base, a push rod, a wedge block, and a screw. When locking, rotating the screw pushes the push rod to move, and the wedge block moves upward along the inclined surface of the wedge protrusion, pressing the plate 8 and the heat-conducting fins 5 together by the change in height.

[0036] The cooling channels inside the upper cold plate 1 include a first irregular rib 101, a first microchannel 102, a first reinforcing rib 103, and a first capillary layer 104; the lower cold plate 4 and the upper cold plate 1 are axially symmetrical structures; the cooling channels inside the lower cold plate 4 include a second irregular rib 401, a second microchannel 402, a second reinforcing rib 403, and a second capillary layer 404.

[0037] Preferably, the first irregular rib 101 and the second irregular rib 401 are arranged in a parallelogram array with symmetrical distribution in the transverse cross-sectional direction.

[0038] Preferably, the first irregular rib 101 and the second irregular rib 401 have a trapezoidal structure in the longitudinal cross-sectional direction.

[0039] Preferably, the first microchannel 102 and the second microchannel 402 have a biomimetic leaf vein-shaped channel structure in the transverse cross-section direction, forming a biomimetic microchannel, which enhances disturbance, destroys the gas-liquid boundary layer, lowers the boiling initiation point, and strengthens boiling heat transfer; the combination of open microchannel and biomimetic microchannel achieves efficient heat transfer inside the two camera boxes.

[0040] Preferably, the first microchannel 102 and the second microchannel 402 have an open channel structure in the longitudinal cross-sectional direction. The open microchannel allows gas and liquid to flow in layers, reduces flow resistance, avoids local evaporation, and makes the flow distribution inside the channel more uniform, thus enhancing flow stability.

[0041] Preferably, the first capillary layer 104 and the second capillary layer 404 are located at the roots of the first irregular rib 101 and the second irregular rib 401, respectively, which can quickly and directionally replenish the liquid working fluid to the heat source area.

[0042] The chassis structure based on phase change heat dissipation disclosed in this invention allows the cooling medium to enter through the inlet channel 6 on the left side plate 2, flow into the cooling channels inside the upper and lower cooling plates 1 and 4, traverse the entire cooling channels inside the upper and lower cooling plates 1 and 4, and exit through the return channel 7. The heat-conducting fins 5 on the upper and lower cooling plates 1 and 4 exchange heat with the circuit board 8, thereby dissipating heat from the circuit board 8 and the electronic components on it.

[0043] The method for calculating the thermal resistance from the hot end to the cold end of the chassis structure based on phase change heat dissipation includes the following steps:

[0044] Step 1: Calculate the internal thermal resistance of the board based on its height, width, thickness, and thermal conductivity.

[0045] The internal thermal resistance R of the circuit board in step 1 c for:

[0046] ;

[0047] In the formula h c k represents the board height. c For the thermal conductivity of the circuit board, L c d represents the width of the circuit board. c For the thickness of the circuit board, in this embodiment, h c =0.135m, k c =237W / (m·K), L c =0.145m, d c =0.0144m.

[0048] Step 2: Determine the economic ratio of the contact thermal resistance between the heating plate 8 and the heat-conducting fins 5 to the internal heat transfer thermal resistance of the heating plate according to the design requirements.

[0049] In step 2, the economical ratio α between the contact thermal resistance between the board and the heat-conducting fins and the internal heat transfer thermal resistance of the board is taken as 1 / 5 to 1 / 3. In this embodiment, α = 1 / 5.

[0050] Step 3: Calculate the height of the heat-conducting fins based on the internal thermal resistance of the board 8, the thermal resistance ratio, the length of the heat-conducting fins 5, the thermal conductivity of the thermal grease 10, and the thickness of the thermal grease 10.

[0051] Step 3: Thermal grease thickness d t Related to the locking torque T of the locking bar, according to Figure 9 The corresponding relationship obtained from the experimental data shown; in this embodiment, T=2.35 (N·m), d t =0.25mm.

[0052] Step 3, the height h of the heat-conducting fins fin for:

[0053]

[0054] In the formula, k t For the thermal conductivity of thermal grease, L fin d is the length of the heat-conducting fin. t The thickness of the thermal grease; in this embodiment, k t =3W / (m·K)L t =0.147m.

[0055] The fin height h obtained in this embodiment t It is 10.5mm.

[0056] Step 4: Calculate the internal thermal resistance of the heat-conducting fins based on their height, length, and thickness.

[0057] In step 4, the internal thermal resistance R of the heat-conducting fins is... fin for:

[0058]

[0059] In the formula k fin For the thermal conductivity of the heat-conducting fins, d fin In this embodiment, k represents the thickness of the thermally conductive fins. fin =237W / (m·K), d t =0.005m.

[0060] Step 5: Calculate the internal thermal resistance of the substrate of the upper cold plate 1 and the lower cold plate 4 based on the thermal conductivity, thermal fin spacing and fin length of the upper cold plate 1 and the lower cold plate 4.

[0061] The internal thermal resistance R of the substrates of the upper cold plate 1 and the lower cold plate 4 in step 5 is described. s for:

[0062]

[0063] In the formula k s d represents the thermal conductivity of the cold plate substrate. s The thickness of the cold-rolled steel plate substrate. In this embodiment, k represents the spacing between adjacent heat-conducting fins. s =237W / (m·K), d s =0.005m, p fin =0.025m.

[0064] Step 6: Calculate the phase change convection heat transfer resistance based on the phase change heat transfer coefficient inside the cold plate and the contact area between the phase change fluid and the wall of the cold plate channel.

[0065] The phase change convection heat transfer thermal resistance R in step 6 is... p for:

[0066]

[0067] In the formula, h p Let A be the phase change convective heat transfer coefficient. p In this embodiment, h represents the phase change convection heat transfer area. p =2000W / (m 2 ·K), A p =0.003625m 2 .

[0068] Step 7: Based on the calculation results of Steps 1-6, obtain the heat transfer resistance from the circuit board to the phase change fluid inside the chassis.

[0069] The total thermal resistance R of heat transfer from the circuit board to the phase change fluid in step 7 is... t for:

[0070] .

[0071] In the formula, α is the economic ratio of the contact thermal resistance between the board and the heat-conducting fins to the internal heat transfer thermal resistance of the board, and R c R is the internal thermal resistance of the circuit board. fin R is the internal thermal resistance of the fins. s R is the internal thermal resistance of the cold plate substrate. p This is the thermal resistance for phase change convection heat transfer.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A chassis structure based on phase change heat dissipation, characterized in that, It includes an upper cooling plate (1), a left side plate (2), a right side plate (3), a lower cooling plate (4), heat-conducting fins (5), an inlet flow channel (6), a return flow channel (7), and a plate (8); the upper cooling plate (1), the left side plate (2), the right side plate (3), and the lower cooling plate (4) are fixedly connected to each other to form the outer shell of the chassis. Heat-conducting fins (5) are provided on the opposite surfaces of the upper cooling plate (1) and the lower cooling plate (4). The upper and lower ends of the plate (8) are installed in the heat-conducting fins (5), and heat exchange occurs between the plate (8) and the heat-conducting fins (5). Electronic components to be cooled are installed on the board (8); the liquid inlet channel (6) and the return channel (7) are set on the left side plate (2) and are connected to the cooling channels inside the upper cold plate (1) and the lower cold plate (4); the cooling medium enters from the liquid inlet channel (6) on the left side plate (2), flows into the cooling channels inside the upper cold plate (1) and the lower cold plate (4), passes through the entire cooling channels inside the upper cold plate (1) and the lower cold plate (4), exchanges heat with the board (8) through the heat-conducting fins (5), and then flows out from the return channel (7).

2. The chassis structure based on phase change heat dissipation according to claim 1, characterized in that, Apply thermal grease (10) between the board (8) and the thermal fins (5) and fix them together with locking strips (9).

3. The chassis structure based on phase change heat dissipation according to claim 1, characterized in that, The lower cold plate (4) and the upper cold plate (1) are axially symmetrical structures. Cooling channels are provided inside both the upper and lower cold plates. The cooling channels include irregular ribs, microchannels, reinforcing ribs, and capillary layers. The irregular ribs are arranged in an array, and microchannels are formed between the irregular ribs. Reinforcing ribs are provided in the middle of the irregular ribs to enhance the structural strength of the cold plate. The capillary layer is located at the root of the irregular ribs and is used for rapid liquid return in the hot zone.

4. The chassis structure based on phase change heat dissipation according to claim 3, characterized in that, The irregularly shaped ribs are arranged in a parallelogram structure with symmetrical distribution in the transverse cross-section.

5. The chassis structure based on phase change heat dissipation according to claim 1, characterized in that, The irregular ribs have a trapezoidal structure in the longitudinal section direction.

6. The chassis structure based on phase change heat dissipation according to claim 1, characterized in that, The microchannels have a biomimetic leaf vein-shaped channel structure in the transverse cross-section.

7. The chassis structure based on phase change heat dissipation according to claim 1, characterized in that, The microchannels have an open channel structure in the longitudinal cross-section.

8. A method for calculating the thermal resistance of a chassis structure based on phase change heat dissipation, characterized in that, The specific steps are as follows: Step 1: Calculate the internal thermal resistance of the circuit board based on its height, width, thickness, and thermal conductivity. Step 2: Determine the economic ratio of the contact thermal resistance between the heating plate and the heat-conducting fins to the internal heat transfer thermal resistance of the heating plate based on design requirements. Step 3: Calculate the height of the thermal fins based on the internal thermal resistance, thermal resistance ratio, length of the thermal fins, thermal conductivity of the thermal grease, and thickness of the thermal grease. Step 4: Calculate the internal thermal resistance of the heat-conducting fins based on their height, length, and thickness. Step 5: Calculate the internal thermal resistance of the cold plate substrate based on the thermal conductivity of the cold plate, the spacing between the thermally conductive fins, and the fin length. Step 6: Calculate the phase change convection heat transfer resistance based on the phase change heat transfer coefficient inside the cold plate and the contact area between the phase change fluid and the wall of the cold plate channel. Step 7: Based on the calculation results of Steps 1-6, obtain the heat transfer resistance from the circuit board to the phase change fluid inside the chassis.

9. The method for calculating the thermal resistance of a chassis structure based on phase change heat dissipation according to claim 8, characterized in that, In step 7, the thermal resistance of heat transfer from the circuit board to the phase change fluid is... The calculation formula is: ； In the formula, α is the economic ratio of the contact thermal resistance between the board and the heat-conducting fins to the internal heat transfer thermal resistance of the board, and R c R is the internal thermal resistance of the circuit board. fin R is the internal thermal resistance of the fins. s R is the internal thermal resistance of the cold plate substrate. p This is the thermal resistance for phase change convection heat transfer.

10. The method for calculating the thermal resistance of a chassis structure based on phase change heat dissipation according to claim 9, characterized in that, In step 1, the internal thermal resistance R of the circuit board c for: ； In the formula, h c k represents the board height. c For the thermal conductivity of the circuit board, L c d represents the width of the circuit board. c For the thickness of the circuit board; In step 3, the height h of the heat-conducting fins fin for: ； In the formula, k t For the thermal conductivity of thermal grease, L fin α is the length of the heat-conducting fin, and α is the economic ratio of the contact thermal resistance between the board and the heat-conducting fin to the internal heat transfer thermal resistance of the board. In step 4, the internal thermal resistance R of the fins is... fin for: ； In the formula, k fin For the thermal conductivity of the heat-conducting fins, d fin For the thickness of the heat-conducting fins; In step 5, the internal thermal resistance R of the cold plate substrate is... s for: ； In the formula, k s d represents the thermal conductivity of the cold plate substrate. s p is the wall thickness of the cold plate substrate. fin The distance between adjacent heat-conducting fins; The phase change convection heat transfer thermal resistance Rp in step 6 is: ； In the formula h p Let A be the phase change convective heat transfer coefficient. p This represents the phase change convection heat transfer area.

Images