A jet impingement wall surface flow truncation enhanced heat exchange method based on flow ratio active regulation

Abstract

A jet impingement wall surface flow truncation enhanced heat transfer method based on flow ratio active regulation belongs to the technical field of heat transfer enhancement and fluid control. A main jet is provided to vertically impact a target surface, so that a main stagnation point and an outwardly expanding wall surface flow are formed on the target surface; a reverse jet is applied to the propagation direction of the wall surface flow, the reverse jet is 20-70 degrees with the target surface, the horizontal component is opposite to the direction of the wall surface flow, and the application position is located in the middle of the adjacent main jet; the flow ratio R is adjusted to be 0.15-0.45, the wall surface flow and the reverse jet are momentum balanced on the target surface to form an artificial stagnation point, and the active regulation of the target surface heat transfer distribution is realized by adjusting R. The cross-flow effect is changed from passive management to active utilization for the first time, the target surface heat transfer coefficient distribution is changed from single-peak to double-peak, the area average convective heat transfer coefficient is improved by not less than 20%, and the heat transfer distribution is real-time regulated; the method is suitable for various high heat flux cooling scenes such as disc laser, high-power electronic device, power semiconductor, laser radar detector, motor controller and the like.

Description

Technical Field

[0001] This invention belongs to the field of heat transfer enhancement and fluid control technology, and relates to a jet impact wall flow interception heat transfer enhancement method based on active flow ratio regulation. It can be widely used in disk laser gain medium cooling, high-power electronic device cooling, power semiconductor cooling, lidar detector cooling, electric vehicle motor controller cooling, and other industrial scenarios that require high heat flux density and efficient cooling. Background Technology

[0002] Jet impingement heat transfer is an enhanced heat transfer method that utilizes a high-speed fluid jet to directly impact a heat transfer surface to achieve efficient convective heat transfer. It is widely used in high heat flux density heat dissipation scenarios. The core physical characteristics of jet impingement heat transfer are: at the impact point, the fluid's kinetic energy is converted into pressure energy, the boundary layer thickness approaches zero, and the local convective heat transfer coefficient reaches its peak; after the fluid impacts the target surface, it expands laterally along the target surface to form a wall jet, the flow direction of which is parallel to the target surface, and the velocity decreases with radial distance.

[0003] In array jet impact applications, the wall flows formed by multiple jet holes converge between adjacent jet holes, generating a crossflow effect. The presence of crossflow reduces the effective impact intensity of the downstream jet. At the same time, the area between the holes is covered by low-velocity, high-temperature wall flows, and the convective heat transfer coefficient is only 20% to 35% of that in the stagnation zone. This results in an extremely uneven distribution of the overall heat transfer coefficient on the target surface, with the area-average heat transfer coefficient significantly lower than the theoretical upper limit.

[0004] To address the crossflow problem, existing technologies mainly employ the following passive management methods: The first type reduces mutual interference of wall flows through geometric optimization, including increasing the jet hole spacing, using fractal branched jet networks, and designing variable spacing arrays; the second type guides the wall flow out by setting up lateral drainage channels or return channels to prevent its accumulation; and the third type adjusts the outlet direction to direct and converge the wall flow before discharge.

[0005] The aforementioned passive management methods have the following fundamental limitations: First, all methods can only mitigate the interference of the wall flow and cannot eliminate the low heat transfer zone in the inter-hole area; second, the heat transfer performance of passive management methods is determined by the fixed geometry and cannot be adjusted in real time according to changes in heat load during device operation; third, passive management methods fail to utilize the kinetic energy carried by the wall flow itself, and the momentum of the wall flow is wasted during the discharge process.

[0006] From the perspective of heat transfer physics, wall flow is not purely a heat transfer attenuator; it carries considerable kinetic energy. If the kinetic energy of the wall flow can be utilized to induce momentum conversion at an appropriate location, forming a second heat transfer enhancement mechanism, the average heat transfer coefficient of the target surface can be significantly improved without increasing the total flow rate. However, current technologies have not yet proposed a jet impingement-enhanced heat transfer method that actively utilizes the kinetic energy of the wall flow and can control the heat transfer intensity in real time.

[0007] Furthermore, in non-uniform heat flow scenarios such as Gaussian heat sources, the required cooling intensity varies significantly across different regions of the target surface. Existing passive management methods cannot achieve precise spatial matching between cooling capacity and heat flow distribution, further exacerbating the non-uniformity of target surface temperature.

[0008] Therefore, there is an urgent need in this field for a jet impact-enhanced heat transfer method that can actively cut off the wall flow, utilize the wall flow energy to form a second heat transfer mechanism, and has real-time control capability. Summary of the Invention

[0009] This invention addresses the technical problems in existing array jet impingement heat transfer systems, such as weakened inter-hole heat transfer due to the convergence of wall flows, the difficulty in real-time control using passive management methods, and the ineffective utilization of wall kinetic energy. It proposes a jet impingement wall flow interception and enhanced heat transfer method based on active flow ratio control. This invention creates an artificial stagnation point by having a counter-pressure jet, directed against the wall flow, oppose it in the inter-hole region. This converts the momentum of the wall flow into a localized high-pressure, low-velocity heat transfer enhancement zone near the target surface, thereby improving the heat transfer capacity in the inter-hole region and the temperature uniformity of the target surface.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for enhanced heat transfer by intercepting wall flow through jet impact based on active flow ratio control is disclosed. The method provides a target surface to be cooled and at least one main jet. The main jet impacts the target surface in a direction perpendicular to the target surface, forming a main stagnation point. A wall jet propagating along the target surface direction is formed around the main stagnation point. At least one counter-jet is applied in the propagation direction of the wall jet. The velocity vector of the counter-jet has an angle of 20 to 70 degrees with the target surface, and the horizontal component of the counter-jet velocity vector is opposite to the propagation direction of the wall jet. The flow rates Q_main of the main jet and Q_counter of the counter-jet are adjusted so that the flow ratio R equals Q_counter divided by Q_main and is maintained within a predetermined range. This causes the wall jet and the counter-jet to achieve momentum equilibrium near the target surface, forming an artificial stagnation point at the equilibrium position, thus achieving enhanced heat transfer by intercepting wall flow through jet impact based on active flow ratio control. Specifically:

[0012] The jet impact wall flow interception enhanced heat transfer method is implemented using a jet impact heat exchanger with independent main jet supply channels and reverse pressure jet supply channels. The jet impact heat exchanger includes a mutually isolated main jet cavity and reverse pressure jet cavity, a jet distribution plate, a target surface to be cooled disposed on one side of the jet distribution plate, and an impact cavity located between the two. The main jet cavity and reverse pressure jet cavity each have independent inlets to adjust the pressure or flow rate of the main jet and reverse pressure jet respectively. The jet distribution plate is provided with a main jet orifice communicating with the main jet cavity and a reverse pressure secondary jet groove communicating with the reverse pressure jet cavity. The main jet orifice is arranged along the normal direction of the target surface, and the reverse pressure secondary jet groove is inclined relative to the normal direction of the target surface. Its outlet is located between adjacent main jet orifices and faces the direction of wall flow propagation formed after the main jet impacts the target surface. The reverse pressure jet ejected from the reverse pressure secondary jet groove has a velocity component along the target surface opposite to the direction of wall flow propagation. The main jet, the reverse pressure jet, and their mixed coolant flow after impact are discharged through the impact chamber to the outlet channel. The heat exchange method includes the following steps:

[0013] S1. Coolant is supplied to the main jet cavity, so that the coolant is sprayed out along the normal direction of the target surface through the main jet holes and impacts the target surface being cooled, forming a main stagnation point at the impact center of each main jet; after the main jet impacts the target surface, it expands along the target surface into the inter-hole region between adjacent main jet holes, forming a wall flow.

[0014] S2. Monitor or set the total flow rate Q_main of the main jet flowing into the impact chamber through all main jet orifices as the benchmark for flow ratio control.

[0015] S3. Coolant is supplied to the reverse pressure jet cavity, so that the coolant is obliquely sprayed out through the reverse pressure auxiliary jet groove set between adjacent main jet holes to form a reverse pressure jet; the angle between the center line of the reverse pressure auxiliary jet groove and the normal direction of the target surface is 20° to 70°, preferably 20° to 60°, and the velocity component of the reverse pressure jet along the target surface is opposite to the propagation direction of the wall flow.

[0016] S4. Monitor or set the total flow rate Q_counter of the reverse pressure jet flowing into the impact chamber through all the reverse pressure secondary jet channels, and control the flow ratio R=Q_counter / Q_main by adjusting the pressure regulating component or flow regulating component in the corresponding liquid supply pipeline of the reverse pressure jet chamber.

[0017] S5. Control the flow ratio R between 0.15 and 0.45 so that the reverse pressure jet and the wall flow meet and collide in the inter-hole region, forming a local low-speed, high-pressure artificial stagnation point near the target surface; the artificial stagnation point and the main stagnation point work together to change the heat exchange capacity of the target surface from a single-peak distribution mainly concentrated at the main stagnation point to a double-peak distribution jointly enhanced by the main stagnation point and the artificial stagnation point.

[0018] S6. Adjust the liquid supply parameters of the main jet cavity and / or the reverse pressure jet cavity according to the heat load change, temperature distribution or heat exchange requirements of the target surface being cooled, so as to change the flow ratio R, thereby adjusting the formation intensity of artificial stagnation points and the flow state of the inter-hole region, and realizing the active control of the heat exchange distribution of the target surface.

[0019] Furthermore, the main jet orifices are arranged in an array, and the counter-pressure auxiliary jet grooves are correspondingly arranged between adjacent main jet orifices; the outlet cross-sectional width of the counter-pressure auxiliary jet grooves can be 0.3 to 0.6 times the diameter of the main jet orifice, and the axial height of the impact chamber can be 0.5 to 2.0 mm. The main jets are provided in an array, and the main jets are arranged in a concentric circle array or a square array, with the ratio S / d of the center distance S between adjacent main jets to the main jet orifice diameter d being 4 to 6.

[0020] Furthermore, the reverse jet is applied at the middle region between two adjacent main jets, and the horizontal component of each reverse jet is directed towards the wall flow generated by the adjacent main jets on both sides; the reverse jet branches into two outlets, which respectively cut off the wall flow generated by the main jets on both sides.

[0021] Furthermore, the flow ratio R is dynamically adjusted according to changes in heat load or heat exchange demand, so that the position and intensity of the artificial stagnation point change in a predetermined manner, thereby realizing real-time active control of the heat exchange distribution on the target surface. The steps of dynamically adjusting the flow ratio R include: setting a temperature sensor on the target surface or the object being cooled, and the controller automatically calculating the optimal flow ratio based on the temperature signal fed back by the temperature sensor through a PID algorithm and driving the flow regulating valve to perform the adjustment.

[0022] Furthermore, in S5, the predetermined range of the flow ratio R is 0.20 to 0.35, within which the artificial anchorage is stably formed at a distance of 0.6 to 0.9 times the distance between adjacent main jets.

[0023] Furthermore, the main jet cavity and the reverse pressure jet cavity are separated from each other in terms of fluid by an isolation sealing layer to prevent the two types of jets from flowing across each other before entering the impact cavity; the main jet and the reverse pressure jet are discharged together after impacting, counter-impacting and mixing in the impact cavity.

[0024] Furthermore, the working media of the main jet and the reverse jet can be the same or different. When different working media are used, water is used for the main jet to obtain high specific heat and strong cooling capacity, while low-viscosity fluorinated liquid is used for the reverse jet to reduce driving energy consumption.

[0025] Furthermore, the method:

[0026] It is suitable for heat transfer scenarios with uneven target surface heat load; by increasing the intensity of reverse pressure jet control in the high heat load area, the heat transfer capacity and temperature uniformity of the area and the adjacent hole area are improved.

[0027] It is used for cooling the gain medium of disk lasers. The target surface to be cooled is the cooling surface of a copper / diamond composite heat sink, which is bonded to the back of a Yb:YAG disk with a thickness of 0.05mm to 0.3mm.

[0028] It can be applied to any of the following applications: cooling of high-power electronic devices, cooling of power semiconductors, cooling of lidar detectors, or cooling of electric vehicle motor controllers.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention actively cuts off the wall flow formed after the main jet impact by the independent liquid supply reverse pressure jet, and forms artificial stagnation points in the hole area, so that the hole area with weak heat exchange can obtain enhanced heat exchange, and improve the area average heat exchange capacity and temperature uniformity of the target surface.

[0031] (2) The present invention uses the flow ratio R as the coordinated control parameter of the main jet and the reverse pressure jet. The formation intensity of the artificial stagnation point can be changed by independently adjusting the pressure or flow of the two liquid supply pipelines, so as to realize the active control of heat exchange capacity with the change of heat load.

[0032] (3) The present invention forms a main stagnation point by the main jet and an artificial stagnation point by the counter-pressure jet and the wall flow, so that the target surface forms a multi-position synergistic heat transfer enhancement; under the same total cooling flow distribution conditions, it is beneficial to improve the insufficient inter-hole heat transfer caused by the wall flow in the traditional jet impact heat transfer.

[0033] (4) The method of the present invention can be applied to scenarios that require high heat flux density cooling, such as disk laser gain medium, high-power electronic devices, power semiconductors, lidar detectors and motor controllers. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the working principle of the method of the present invention, showing that the main jet A impacts the cooled target surface F along the normal direction of the target surface to form the main stagnation point D. After the main jet impacts the target surface, it forms a wall flow B that expands in opposite directions along the target surface. The counter-pressure jet C is sprayed into the inter-hole region at an angle θ with the normal direction of the target surface and opposes the wall flow B to form an artificial stagnation point E in the inter-hole region. Figure 1 The example also shows an angle of 30° between adjacent reverse pressure jet channels.

[0035] Figure 2 The flowchart of the method of the present invention shows the execution sequence of S1 to S6 and the closed-loop control relationship of adjusting the flow ratio R by heat load feedback: first, the main stagnation point and wall flow are formed, then the main jet flow rate is monitored, the reverse pressure jet is applied, the flow ratio is adjusted, a bimodal heat transfer distribution is formed, and the flow ratio is adjusted according to the heat load change feedback.

[0036] Figure 3 This is a distribution diagram of the radial convection heat transfer coefficient of the target surface when the flow ratio R is equal to 0. At this time, only the main jet impacts the target surface, and the heat transfer coefficient at the main stagnation point is relatively high. However, the inter-hole region between the two main jets forms a low heat transfer zone due to the convergence of wall flow and velocity attenuation. Overall, it shows a single-peak or multi-peak distribution with the main stagnation point as the peak value and the inter-hole region as the valley value.

[0037] Figure 4 This is a distribution diagram of the radial convection heat transfer coefficient of the target surface when the flow ratio R is equal to 0.25. The momentum of the reverse pressure jet matches that of the wall flow, forming a stable artificial stagnation point between the two main jets. The heat transfer coefficient in the inter-hole region is significantly improved, and the main stagnation point and the artificial stagnation point together form a bimodal structure. This figure corresponds to the preferred control range of the method of this invention, illustrating that an appropriate flow ratio can take into account both the heat transfer at the main stagnation point and the enhancement of the inter-hole region.

[0038] Figure 5 This is a distribution diagram of the radial convective heat transfer coefficient on the target surface when the flow ratio R is equal to 0.5. When the flow rate of the reverse pressure jet is too large, although the heat transfer enhancement near the artificial stagnation point is more significant, the reverse pressure jet generates back pressure and disturbance in the main stagnation point region, thus suppressing the peak value at the main stagnation point. Therefore, Figure 5 This indicates that a higher flow ratio is not necessarily better; it should be controlled within a predetermined range to avoid excessive reverse pressure jets that could reduce the heat exchange at the main stagnation point.

[0039] Figure 6 A comparison of the target surface heat transfer coefficient distribution under different flow ratio control conditions is presented, illustrating the differences in the target surface heat transfer coefficient distribution under the two flow control conditions. As the flow ratio R of the reverse pressure jet changes, the momentum balance state between the reverse pressure jet and the wall flow changes accordingly, the formation location and intensity of the artificial stagnation point change, and the corresponding local heat transfer enhancement region also shifts or changes; therefore... Figure 6 This is used to illustrate how the location and intensity of artificial anchorages can be designed and actively controlled by adjusting the flow ratio.

[0040] Figure 7 This is a contour plot of the target surface heat transfer coefficient after applying a reverse pressure jet and adjusting the flow ratio. (Compared to...) Figure 6 In comparison, the low heat transfer zone between the holes was filled, a new heat transfer enhancement zone was formed near the artificial stagnation point, and the distribution of the high heat transfer zone on the target surface was more continuous, indicating that the reverse pressure jet can cut off the wall flow and improve the heat transfer uniformity of the target surface.

[0041] Figure 8This is a cross-sectional schematic diagram and a partial enlarged view of the dual-cavity independent liquid supply jet impact heat exchange device used in the method of the present invention. It shows the main jet cavity, the reverse pressure jet cavity, the isolation sealing layer, the jet distribution plate, the main jet hole, the reverse pressure secondary jet groove, the impact cavity, the heat sink, the outer shell, the liquid outlet cavity, and the relative positional relationship between the liquid inlet of the main cavity, the liquid inlet of the secondary cavity, and the liquid outlet. It also shows the oblique flow channel of the reverse pressure secondary jet groove and the liquid supply path isolated from the main jet cavity.

[0042] In the figure: A is the main jet, B is the wall flow, C is the reverse pressure jet, D is the main stagnation point, E is the artificial stagnation point, F is the target surface being cooled, and θ is the angle between the reverse pressure jet and the normal direction of the target surface.

[0043] 1 Outer shell, 2 Main jet cavity, 3 Counterpressure jet cavity, 4 Isolation sealing layer, 5 Jet distribution plate, 6 Main jet hole, 7 Counterpressure secondary jet groove, 8 Impact cavity, 9 Heat sink, 10 Yb:YAG disc, 11 Main cavity inlet, 12 Secondary cavity inlet, 13 Outlet, 14 Outlet cavity. Detailed Implementation

[0044] The specific embodiments of the method of the present invention will be described in detail below with reference to the accompanying drawings. The method of the present invention can be applied to various high heat flux density cooling scenarios. The embodiments of the present invention are described below through three specific examples, but the scope of protection of the present invention is not limited thereto.

[0045] The jet impingement wall flow interception enhanced heat transfer method is implemented using a jet impingement heat exchanger with independent main jet supply channels and reverse pressure jet supply channels. The jet impingement heat exchanger is as follows: Figure 7 and Figure 8 As shown, the system includes an outer shell 1, a main jet cavity 2, a reverse pressure jet cavity 3, an isolation sealing layer 4, a jet distribution plate 5, an impact cavity 8, a heat sink 9, and a liquid outlet cavity 14. The main jet cavity 2 is the primary cavity, and the reverse pressure jet cavity 3 is the secondary cavity. The outer shell 1 is a manifold housing, a closed shell that houses and positions the aforementioned components. The heat sink 9 is installed at one end of the outer shell 1 and has a heated surface and a cooled surface arranged opposite each other. The Yb:YAG disk 10 of the disk laser is fixed to the heated surface, and the cooled surface constitutes a target surface for heat exchange by the impact of the coolant. In this invention, the target surface normal direction refers to the direction perpendicular to the cooled surface; the axial direction refers to the direction parallel to the target surface normal direction; and the radial direction refers to the direction located in the plane of the target surface and extending outward from the center of the heat sink 9. Specifically:

[0046] The jet distribution plate 5 is disposed on the cooling surface side of the heat sink 9 and is axially spaced from the heat sink 9; the gap between the two forms an impact chamber 8. The impact chamber 8 is a flow space where the main jet impacts the target surface, the secondary jet counteracts the wall flow, and the coolant mixes. The side of the jet distribution plate 5 away from the heat sink 9, together with the outer shell 1, forms a main jet cavity 2 and a reverse pressure jet cavity 3; the main jet cavity 2 and the reverse pressure jet cavity 3 are not connected to each other, and are respectively provided with a main cavity inlet 11 and a secondary cavity inlet 12 connected to an external liquid supply pipeline. The main cavity inlet 11 supplies liquid only to the main jet cavity 2, and the secondary cavity inlet 12 supplies liquid only to the reverse pressure jet cavity 3, and the pressure or flow rate of the coolant entering the main jet cavity 2 and the reverse pressure jet cavity 3 can be adjusted respectively.

[0047] The isolation sealing layer 4 is disposed between the main jet cavity 2 and the reverse pressure jet cavity 3, and its periphery is sealed to the outer casing 1 to separate the two cavities in terms of fluid. The isolation sealing layer 4 can be a thin metal sheet, and a sealing ring can be provided between it and adjacent components. The main jet channel passes through the isolation sealing layer 4 and communicates with the main jet cavity 2; the secondary jet channel does not communicate with the main jet cavity 2, but communicates with the reverse pressure jet cavity 3 through a bypass disposed in the outer casing 1 or the jet distribution plate 5. Therefore, when the main jet cavity 2 and the reverse pressure jet cavity 3 have different liquid supply pressures, the coolant in the two cavities can still remain isolated from each other.

[0048] The jet distribution plate 5 is provided with a main jet hole 6 and a counter-pressure auxiliary jet groove 7. The main jet hole 6 penetrates the jet distribution plate 5 axially, with one end connected to the main jet cavity 2 and the other end facing the target surface of the heat sink 9; the coolant flowing out of the main jet hole 6 is sprayed onto the target surface along the normal direction of the target surface, forming the main stagnation point heat exchange zone. In this invention, the main stagnation point heat exchange zone refers to the region near the impact center of the main jet when the main jet impacts the target surface perpendicularly, where the flow velocity decreases, the pressure increases, and the heat exchange is stronger. Multiple main jet holes 6 can be arranged in a concentric circle array around the center of the jet distribution plate 5, with a predetermined inter-hole region between adjacent main jet holes 6.

[0049] The reverse pressure auxiliary jet channel 7 is an oblique flow channel that penetrates or partially penetrates the jet distribution plate 5. Its inlet is connected to the reverse pressure jet cavity 3 via a bypass, and its outlet is located on the side near the target surface of the heat sink 9 and leads to the impact cavity 8. The centerline of the reverse pressure auxiliary jet channel 7 is inclined relative to the normal direction of the target surface, so that the ejected auxiliary jet has a velocity component along the target surface direction. The outlet of each reverse pressure auxiliary jet channel 7 is located between adjacent main jet holes 6, and its spray direction is towards the wall flow that expands outward after the adjacent main jet impacts the target surface. In this invention, the wall flow refers to the coolant flow that expands laterally along the target surface after the main jet impacts the target surface; the reverse pressure jet refers to the auxiliary jet supplied by the reverse pressure jet cavity 3 and ejected in a direction opposite to or opposite to the wall flow. The auxiliary jet ejected from the reverse pressure auxiliary jet channel 7 meets and collide with the wall flow in the inter-hole region, forming an artificial stagnation point with a localized reduction in flow velocity in this region. In this invention, an artificial stagnation point refers to a localized low-speed, high-pressure region formed by the opposing flow of two opposing fluids, which is different from the main stagnation point formed by the direct impact of a single main jet on the target surface.

[0050] The outlet chamber 14 is located radially outside the impact chamber 8 and surrounds the impact chamber 8 circumferentially along the heat sink 9. The impact chamber 8 is connected to the outlet chamber 14, which is provided with an outlet 13. The wall flow formed after the main jet impacts the target surface, the secondary jet ejected from the counter-pressure secondary jet groove 7, and the coolant mixed with the main jet all flow from the impact chamber 8 into the outlet chamber 14 and are discharged through the outlet 13. The outlet 13 is not directly connected to the main jet chamber 2 or the counter-pressure jet chamber 3, thereby preventing the discharged coolant from directly entering either of the supply chambers.

[0051] Furthermore, the diameter of the main jet orifice 6 is 0.3–2.0 mm; the spacing between the main jet orifices 6 is 4–15 times the orifice diameter, preferably 8–15 times. The main jet orifice 6 includes a central hole located at the center of the jet distribution plate 5 and at least two concentric rings of annular holes arranged around the central hole; in the case of two concentric rings of annular holes, the number of the central hole, the first ring of annular holes, and the second ring of annular holes is preferably 1:6:12.

[0052] Furthermore, the angle between the reverse pressure auxiliary jet groove 7 and the normal direction of the target surface is 20° to 60°, preferably 30° ± 10°; the outlet cross-sectional width of the reverse pressure auxiliary jet groove 7 is 0.3 to 0.6 times the diameter of the main jet hole 6. The axial height of the impact chamber 8 is 0.5 to 2.0 mm.

[0053] Furthermore, the isolation sealing layer 4 has a thickness of 0.2 to 0.5 mm, is made of stainless steel, and is sealed with adjacent components by sealing rings, and sealed with upper and lower layers by O-rings; the isolation sealing layer 4 can withstand a pressure difference of not less than 0.5 MPa between the main jet cavity 2 and the reverse pressure jet cavity 3.

[0054] Furthermore, the heat sink 9 is a disc-shaped component made of Cu / Diamond composite material, with a thickness of 2 to 5 mm, a thermal conductivity of not less than 400 W / (m·K), and a surface roughness Ra of its target surface of not more than 0.4 μm.

[0055] Furthermore, the Yb:YAG disc 10 is bonded to the surface of the heat sink 9 away from the impact cavity 8 by an indium sheet with a thickness of 45μm~55μm.

[0056] Furthermore, the pressure in the secondary chamber can be independently adjusted. Specifically, by adjusting the pressure regulating components or flow regulating components in the corresponding supply pipelines of the main chamber inlet 11 and the secondary chamber inlet 12, the ratio of the secondary jet flow rate to the main jet flow rate, Q_counter / Q_main, can be set to 0.15–0.45, preferably 0.20–0.35. Here, Q_counter is the total flow rate of the secondary jet flowing into the impact chamber 8 through all the reverse-pressure secondary jet channels 7, and Q_main is the total flow rate of the main jet flowing into the impact chamber 8 through all the main jet holes 6. By changing the flow rate ratio, the formation intensity of the artificial stagnation point and the flow state within the inter-hole region can be adjusted.

[0057] Example 1: Cooling of Yb:YAG Gain Medium in Disk Laser

[0058] This embodiment applies the method of the present invention to the cooling of a Yb:YAG disk in a disk laser. The object to be cooled is a copper / diamond composite heat sink with a diameter of 35 mm and a thickness of 3.5 mm. The front side of the heat sink is bonded to the back side of the Yb:YAG disk with a thickness of approximately 0.1 mm via an indium foil bonding layer with a thickness of approximately 50 μm. The Yb:YAG disk is irradiated by a Gaussian pump spot with a diameter of approximately 17 mm, and the peak power density of the heat source is approximately 400 W / cm². The side of the heat sink away from the Yb:YAG disk serves as the target surface to be cooled. A jet distribution plate with a main jet hole and a reverse pressure secondary jet groove is disposed above the target surface, and an impact cavity is formed between the jet distribution plate and the target surface.

[0059] This embodiment adopts Figure 8 The diagram shows a dual-chamber independent liquid supply structure. The main jet chamber and the reverse pressure jet chamber are separated by an isolation sealing layer and are connected to the main chamber inlet and the secondary chamber inlet, respectively. The main jet chamber supplies liquid only to the main jet orifice, and the reverse pressure jet chamber supplies liquid only to the reverse pressure secondary jet groove. The two are isolated from each other before entering the impact chamber. An outlet chamber is provided outside the impact chamber, through which the main jet, the reverse pressure jet, and the mixed coolant are discharged.

[0060] The specific operation steps of this embodiment are as follows:

[0061] S1, such as Figure 1 and Figure 8As shown, the jet distribution plate is positioned above the heat sink target surface. The main jet holes are arranged in a concentric circle array with one hole in the center, six holes in the inner ring, and twelve holes in the outer ring, for a total of 19 main jet holes. The diameter of the main jet holes is 0.4 mm. The cooling medium is deionized water at a temperature of 28 ℃, which is supplied to the main jet cavity through the main cavity inlet. The main cavity supply pressure is set to 0.30 MPa. The coolant is ejected from the main jet holes along the normal direction of the target surface and impacts the heat sink target surface, forming main stagnation points at the corresponding positions of each main jet hole. After impact, the coolant expands along the target surface between adjacent main jet holes, forming a wall flow.

[0062] S2, such as Figure 2 As shown, a turbine flow meter is installed on the supply pipeline corresponding to the main cavity inlet to monitor the total flow rate Q_main of the main jet entering the impact cavity through all main jet orifices in real time. In this embodiment, the measured total flow rate Q_main of the main jet is 3.5 L / min, and this flow rate is used as the benchmark for reverse pressure jet control.

[0063] S3, such as Figure 1 and Figure 8 As shown, a counter-pressure auxiliary jet channel is installed between adjacent main jet orifices. The counter-pressure auxiliary jet channel is a rectangular cross-section inclined flow channel with a channel width of 0.2 mm and a channel depth of 0.3 mm. The angle between the center line of the channel and the normal direction of the target surface is 30°. The outlet of the counter-pressure auxiliary jet channel flows towards the wall along the target surface direction, so that the velocity component of the counter-pressure jet along the target surface is opposite to the propagation direction of the wall flow. The counter-pressure auxiliary jet channel is independently supplied with liquid through the counter-pressure jet cavity, which is separated from the main jet cavity by a stainless steel isolation sealing layer.

[0064] S4, such as Figure 2 As shown, a turbine flow meter is installed on the supply pipeline corresponding to the inlet of the reverse pressure jet chamber to monitor the total flow rate Q_counter of the reverse pressure jet. The supply pressure of the reverse pressure jet is adjusted by the back pressure valve on the supply pipeline to make the flow ratio R = Q_counter / Q_main 0.25. During the adjustment process, the total flow rate Q_main of the main jet is kept basically stable, and R is continuously adjusted by changing Q_counter.

[0065] Figure 4 The radial heat transfer coefficient curves show that the main stagnation point peak and the artificial stagnation point peak coexist, and the low heat transfer zone between the original holes is enhanced. Figure 6 The heat transfer coefficient distributions of the two flow control conditions are different, indicating that the formation location and intensity of the artificial stagnation point change after the flow ratio is changed. Figure 7 This further demonstrates the spatial distribution of the target surface heat transfer enhancement region after the formation of the artificial stagnation point.

[0066] Figures 3 to 5The radial heat transfer coefficient distribution under different flow ratios was compared: when R equals 0, only the main stagnation point is formed, and the heat transfer in the inter-hole region is weak; when R equals 0.25, a relatively stable bimodal heat transfer structure is formed; when R equals 0.5, the reverse pressure jet is too strong and generates back pressure on the main stagnation point, indicating that R should be controlled within the reasonable range defined by this invention. Figure 6 This further demonstrates that even when reverse pressure jet is used, the heat transfer coefficient distribution under different flow ratio control conditions is still different, and the location and intensity of artificial stagnation points can be actively designed through the flow ratio. Figure 7 This reflects the spatial distribution of the corresponding heat exchange enhancement region.

[0067] This embodiment demonstrates that by independently adjusting the liquid supply parameters of the main jet and the reverse pressure jet, the flow state and heat transfer distribution in the inter-hole region can be actively altered without changing the main jet orifice array. By using the flow ratio R as the control parameter, the position and intensity of the artificial stagnation point can be adjusted when the heat load changes, enabling the main stagnation point and the artificial stagnation point to work together, thereby improving the heat transfer uniformity on the back side of the Yb:YAG disk in the disk laser.

[0068] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.

Claims

1. A method for enhancing heat transfer by intercepting jet impact on a wall flow based on active flow ratio control, characterized in that, The method for enhancing heat transfer by intercepting the flow through the jet impact wall is as follows: A cooled target surface and at least one main jet are provided, the main jet impacting the target surface in a direction perpendicular to the target surface to form a main stagnation point, and forming a wall jet around the main stagnation point that propagates along the target surface direction; At least one reverse jet is applied in the direction of propagation of the wall jet, the velocity vector of the reverse jet having an angle of 20 to 70 degrees with the target surface, and the horizontal component of the velocity vector of the reverse jet being opposite to the direction of propagation of the wall jet. The flow rates Q_main and Q_counter of the main jet and the reverse jet are adjusted to keep the flow ratio R equal to Q_counter divided by Q_main within a predetermined range. This allows the wall jet and the reverse jet to achieve momentum equilibrium near the target surface, forming an artificial stagnation point at the equilibrium position. This achieves enhanced heat transfer by intercepting the jet impact wall flow based on active flow ratio control.

2. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 1, characterized in that, The jet impingement wall flow interception enhanced heat transfer method is implemented using a jet impingement heat exchange device with independent main jet liquid supply channels and reverse pressure jet liquid supply channels. The jet impingement heat exchange device includes a mutually isolated main jet cavity and reverse pressure jet cavity, a jet distribution plate, a cooled target surface disposed on one side of the jet distribution plate, and an impingement cavity located between the two. The main jet cavity and the reverse pressure jet cavity are each provided with independent liquid inlets to adjust the pressure or flow rate of the main jet and the reverse pressure jet respectively. The jet distribution plate is provided with a connection to the main jet cavity... The system comprises a main jet orifice and a reverse pressure secondary jet groove connected to the reverse pressure jet cavity; the main jet orifice is positioned along the normal direction of the target surface, and the reverse pressure secondary jet groove is inclined relative to the normal direction of the target surface, with its outlet located between adjacent main jet orifices and facing the direction of wall flow propagation formed after the main jet impacts the target surface; the reverse pressure jet ejected from the reverse pressure secondary jet groove has a velocity component along the target surface opposite to the direction of wall flow propagation; the main jet, reverse pressure jet, and their mixed coolant after impact flow through the impact cavity to the liquid outlet channel and are discharged; the heat exchange method includes the following steps: S1. Coolant is supplied to the main jet cavity, so that the coolant is sprayed out along the normal direction of the target surface through the main jet holes and impacts the target surface being cooled, forming a main stagnation point at the impact center of each main jet; after the main jet impacts the target surface, it expands along the target surface into the inter-hole region between adjacent main jet holes, forming a wall flow. S2. Monitor or set the total flow rate Q_main of the main jet flowing into the impact chamber through all main jet orifices as the benchmark for flow ratio control; S3. Supply coolant to the reverse pressure jet cavity, so that the coolant is obliquely sprayed out through the reverse pressure auxiliary jet groove set between adjacent main jet holes to form a reverse pressure jet; the angle between the center line of the reverse pressure auxiliary jet groove and the normal direction of the target surface is 20° to 70°, and the velocity component of the reverse pressure jet along the target surface is opposite to the propagation direction of the wall flow. S4. Monitor or set the total flow rate Q_counter of the reverse pressure jet flowing into the impact chamber through all the reverse pressure secondary jet channels, and control the flow ratio R=Q_counter / Q_main by adjusting the pressure regulating component or flow regulating component in the corresponding liquid supply pipeline of the reverse pressure jet chamber. S5. Control the flow ratio R between 0.15 and 0.45 so that the reverse pressure jet and the wall flow meet and collide in the inter-hole region, forming a local low-speed, high-pressure artificial stagnation point near the target surface; the artificial stagnation point and the main stagnation point work together to change the heat transfer capacity of the target surface from a single-peak distribution mainly concentrated at the main stagnation point to a double-peak distribution jointly enhanced by the main stagnation point and the artificial stagnation point. S6. Adjust the liquid supply parameters of the main jet cavity and / or the reverse pressure jet cavity according to the heat load change, temperature distribution or heat exchange requirements of the target surface being cooled, so as to change the flow ratio R, thereby adjusting the formation intensity of artificial stagnation points and the flow state of the inter-hole region, and realizing the active control of the heat exchange distribution of the target surface.

3. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 2, characterized in that, The main jet holes are arranged in an array, and the counter-pressure auxiliary jet grooves are correspondingly arranged between adjacent main jet holes; the outlet cross-sectional width of the counter-pressure auxiliary jet grooves can be 0.3 to 0.6 times the diameter of the main jet holes, and the axial height of the impact chamber can be 0.5 to 2.0 mm.

4. The method for enhanced heat transfer by jet impacting wall flow interception based on active flow ratio control according to claim 3, characterized in that, The main jets are provided in an array, and the main jets are arranged in a concentric circle array or a square array. The ratio of the center-to-center distance S of adjacent main jets to the main jet aperture d, S / d, is 4 to 6.

5. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 4, characterized in that, The reverse jet is applied in the middle region between two adjacent main jets, and the horizontal component of each reverse jet is directed towards the wall flow generated by the adjacent main jets on both sides. The reverse jet branches into two outlets, which respectively cut off the wall flow generated by the main jets on both sides.

6. The method for enhanced heat transfer by jet impacting wall flow interception based on active flow ratio control according to claim 5, characterized in that, The flow ratio R is dynamically adjusted according to changes in heat load or heat exchange demand, so that the position and intensity of the artificial stagnation point are changed in a predetermined manner, thereby realizing real-time active control of the heat exchange distribution on the target surface. The steps of dynamically adjusting the flow ratio R include: setting a temperature sensor on the target surface or the object being cooled, and the controller automatically calculating the optimal flow ratio based on the temperature signal fed back by the temperature sensor through a PID algorithm and driving the flow regulating valve to perform the adjustment.

7. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 6, characterized in that, The predetermined range of the flow ratio R is 0.20 to 0.35, within which artificial stagnation points are stably formed at a distance of 0.6 to 0.9 times the distance between adjacent main jets.

8. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 7, characterized in that, The main jet chamber and the reverse pressure jet chamber are separated from each other in terms of fluid by an isolation sealing layer to prevent the two types of jets from flowing across each other before entering the impact chamber; the main jet and the reverse pressure jet are discharged together after impacting, counter-impacting and mixing in the impact chamber.

9. The method for enhanced heat transfer by jet impingement on wall flow based on active flow ratio control according to claim 8, characterized in that, The working media of the main jet and the reverse jet can be the same or different. When different working media are used, water is used for the main jet to obtain high specific heat and strong cooling capacity, while low viscosity fluorinated liquid is used for the reverse jet to reduce driving energy consumption.

10. A method for enhancing heat transfer by intercepting jet impact on a wall flow based on active flow ratio control, as described in claim 9, characterized in that, The method described: It is suitable for heat transfer scenarios with uneven heat load on the target surface; by increasing the intensity of the reverse pressure jet control in the high heat load area, the heat transfer capacity and temperature uniformity are improved. It is used for cooling the gain medium of disk lasers. The target surface to be cooled is the cooling surface of a copper / diamond composite heat sink, which is bonded to the back of a Yb:YAG disk with a thickness of 0.05mm to 0.3mm. It can be applied to any of the following applications: cooling of high-power electronic devices, cooling of power semiconductors, cooling of lidar detectors, or cooling of electric vehicle motor controllers.

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