CN105658027B - Liquid cooling plate for electronic unit cooling - Google Patents

Abstract

A liquid cold plate for cooling electronic components, including a base plate and a cover plate. There are multiple parallel straight slots on the base plate, and the adjacent straight slots are connected end to end. The arc transition between the grooves; the straight grooves on the base plate, the connecting grooves and the cover plate form a flow channel for the cooling liquid to flow through, and a first groove is opened on the bottom wall of each straight groove, and the width of the first groove is It accounts for 60% to 80% of the width of the runner. The invention has the advantages of being able to take into account both the temperature rise of the liquid cold plate and the drop of cooling hydraulic pressure, and realize the simultaneous and substantial reduction of the temperature rise of the liquid cold plate and the drop of cooling hydraulic pressure.

Description

Liquid Cold Plates for Electronic Component Cooling

technical field

The invention relates to a heat exchanger device suitable for being installed on electronic equipment and a generator, in particular to a liquid cold plate.

technical background

The liquid cold plate has excellent heat dissipation performance. It is a device with medium and high power density. The liquid cold plate can effectively take away the heat dissipation in power devices, printed circuit board assemblies or extension equipment. The characteristics of the liquid cold plate cooling system are: (1) the temperature gradient on the cold plate is small, the heat distribution is uniform, and the large concentrated heat load can be taken away; (2) due to the indirect cooling method, the electronic components can not Direct contact with coolant reduces various pollution and improves work reliability; (3) Compared with direct cooling, the loss of coolant is less, and it is also convenient to use more effective coolant to improve cooling efficiency; (4) Cooling The assembly of the plate device is simple, the structure is compact, and the maintenance is convenient. Combining the above-mentioned series of advantages, the application of cold plates in heat dissipation devices has broad prospects.

The liquid cold plate solves the heat generation problem of electrical equipment by dissipating heat evenly on the entire plate surface. Commonly used liquid cold plates are flow paths designed using coiled tubes or plate fins sandwiched between at least two flat plates. The disadvantage of using coiled tubes or plate fins to make flow passages (flow channels) is that: coiled tubes need to be bent from straight tubes, and a straight tube may only be made into a part of the coiled tube, so the coiled tube has There may be leaks at the weld. The plate fins are sandwiched between two flat plates, and the plate fins are brazed with the flat plates to form a flow path (flow channel), and there may also be leaks at the brazing place. In addition, the problem of complicated process exists in the bending of coiled tubes and brazing plate fins and flat plates.

In order to overcome the above disadvantages, Chinese patent ZL200580049517.9 discloses an improved heat exchanger device, which is suitable for cooling electronic components mounted on at least one outer surface of the device, the device includes: a substrate; a cover plate; a cladding sheet a material interposed between the base plate and the cover plate, wherein the cladding sheets are rigidly joined to form a single integral plate; at least one inlet and at least one outlet at one or opposite ends of the formed plate, For cooling medium ingress and egress, the base plate is configured with a plurality of flow channels, each channel comprising several machined grooves with predetermined varying dimensions corresponding to the corresponding thermal traces of the electronic components, thereby optimizing the rate of heat transfer , and a plurality of interconnections are designed between the grooves constituting one of the continuous and parallel flow paths. In this heat exchanger, the flow channels are a plurality of grooves constructed on the base plate by a numerically controlled machine tool. The fluid channels have varying depths and varying widths. Through the design of the flow channel, the fluid velocity of the coolant in the high heat flux area is accelerated, the heat transfer amount is enhanced, and the fluid velocity is reduced in the low heat flux area, so that the fluid pressure drop is minimized.

Pressure drop and temperature rise are important indicators to measure the performance of the cold plate. The temperature rise represents the heat dissipation capacity of the cold plate. The pressure drop determines the power of the cold plate coolant to drive the pump. The performance optimization measures of the cold plate are based on these two performance indicators. The simultaneous reduction of pressure drop and temperature rise is contradictory in theory, and the existing optimization technical measures will lead to the improvement of the performance of another index while reducing one index.

By Fourier's law:

Cold plate temperature rise:

In the formula: Δt——temperature rise of cold plate

q _m ——coolant flow rate in the cold plate

C _p ——Specific heat capacity of coolant

——heat source power

Cold plate pressure drop:

In the formula: Δp——cold plate pressure drop

f'——Hagen-Boiselli friction coefficient

L——Equivalent length of cold plate pipe

d——hydraulic diameter

u——coolant flow rate in the tube

A _c - the cross-sectional area of the pipe

From (2.1), (2.2) can get:

It can be seen from formula (3) that the temperature rise Δt of the cold plate is inversely proportional to the pressure drop ΔP, and in the heat exchanger equipment disclosed in ZL200580049517.9, the faster flow rate of the coolant in the high heat flux area will lead to an increase in the pressure drop of the fluid. Its optimization measures cannot take into account both pressure drop and temperature rise.

Contents of the invention

The object of the present invention is to provide a liquid cold plate for cooling electronic components that can take into account both the temperature rise of the liquid cold plate and the cooling liquid pressure drop, and realize a significant reduction in both the temperature rise of the liquid cold plate and the cooling liquid pressure drop.

A liquid cold plate used for cooling electronic components, including a base plate and a cover plate. There are multiple parallel straight slots on the base plate, and the adjacent straight slots are connected end to end. There is a circular arc transition between the grooves; the straight grooves on the base plate, the connecting grooves and the cover plate form a flow channel for the cooling liquid to flow through. It is characterized in that: the bottom wall of each straight groove is provided with a bottom groove, and the bottom groove The width accounts for 60% to 80% of the runner width. The flow channel is topped by the cover plate and bottomed by the base plate, and the wall surface of the straight groove closed by the cover plate is the top wall of the flow channel. Through the simulation calculation of flow channels with different widths, the cooling effect is the best when the groove width is 60%-80% of the flow channel width, and the depth of the groove is not greatly affected by the size of the flow channel.

Further, there are multiple grooves in each straight groove, a bottom groove is set on the bottom wall of each groove, a top groove is set on the top wall of each groove, the width of the bottom groove and the width of the top groove They respectively account for 60% to 80% of the width of the channel where they are located.

Further, the depth of both the top groove and the bottom groove is 0.2 mm. The cooling liquid in the too deep groove is not easy to exchange heat with the cooling liquid in the flow channel, and the degree of flow around the boundary layer of the flow channel cannot reach the maximum if it is too shallow, and the heat exchange effect of the groove with a depth of 0.2mm is the best.

Further, the flow channel has two inlets and one outlet, and the outlet is located between the two inlets. The flow channel is set as two inlets, and the coolant enters into the two inlets respectively, so that the coolant only needs to flow from any inlet to the outlet, without having to completely flow through the entire flow channel, and the pressure drop of the coolant is greatly reduced.

Further, the outlet is located at 1/2 of the runner stroke. The stroke of the coolant from the inlet to the outlet is 1/2 of the length of the flow channel, so the distance traveled by the coolant in the cold plate is reduced by half, and the pressure drop of the coolant is greatly reduced.

The advantages of the present invention are:

1. After adding the groove structure, the bottom wall and top wall of the fluid channel are uneven, which intensifies the turbulent flow of the boundary layer of the coolant, thins the thickness of the boundary layer, enhances the convective heat transfer effect, and reduces the temperature rise of the liquid cooling plate. At the same time, the groove structure makes the cross-sectional area of the flow channel larger, and the pressure drop is reduced under the same inlet flow rate. Therefore, both the temperature rise of the liquid cold plate and the drop of cooling hydraulic pressure can be taken into account, and the temperature rise of the liquid cold plate and the drop of cooling hydraulic pressure can be greatly reduced at the same time.

2. By setting two inlets on the flow channel, and the outlet is located between the two inlets, the stroke of the coolant flowing through is reduced, and the pressure drop is reduced.

Description of drawings

FIG. 1 is a schematic perspective view of a substrate.

Fig. 2 is a plan view of the substrate.

Fig. 3 is a sectional view taken along line B-B of Fig. 2 .

FIG. 4 is an enlarged view of part A of FIG. 3 .

Fig. 5 is an axial cross-sectional view of a channel without grooves.

Fig. 6 is an axial cross-sectional view of a channel provided with grooves.

Figure 7 is a schematic diagram of the temperature boundary layer.

Fig. 8 is a cloud diagram of the pressure drop and temperature simulation of the channel without grooves.

Fig. 9 is a simulation cloud diagram of the pressure drop and temperature of the grooved channel.

Fig. 10 is a schematic view of the longitudinal cross-section A-A of the channel without grooves.

Fig. 11 is a temperature contour diagram of the A-A section of the flow channel without grooves.

Fig. 12 is a temperature contour diagram of the A-A section of the flow channel with grooves.

Fig. 13 is a velocity contour diagram of the A-A section of the flow channel without grooves.

Fig. 14 is a velocity contour diagram of the A-A section of the flow channel with grooves.

Fig. 15 is a contour diagram of the field coordination angle of the A-A section of the flow channel without grooves.

Fig. 16 is a contour diagram of the field synergy angle in the section A-A of the channel with grooves.

Fig. 17 is a schematic diagram of a flow channel with two inlets and one outlet.

Fig. 18 is a simulation cloud diagram of pressure drop and temperature of a single inlet and single outlet channel without grooves.

Fig. 19 is a cloud diagram of the pressure drop and temperature simulation of the two inlet channels without grooves.

Fig. 20 is a simulation cloud diagram of pressure drop and temperature of a single inlet and single outlet flow channel with grooves.

Fig. 21 is a simulation cloud diagram of the pressure drop and temperature of the two inlet channels with grooves.

Detailed ways

Example 1

As shown in Figures 1 and 2, the liquid cooling plate used for cooling electronic components includes a base plate 1 and a cover plate. The base plate 1 is provided with a plurality of parallel straight grooves 11, and the front and rear adjacent straight grooves 11 are connected end to end. The straight grooves 11 are connected through the connecting groove 12, and the arc transition between the straight grooves 11 and the connecting grooves 12; the straight grooves 11, the connecting grooves 12 and the cover plate on the base plate 1 enclose a flow channel for the cooling liquid to flow through. A bottom groove 13 is opened on the bottom wall of each straight groove 11, and the width of the bottom groove 13 accounts for 60%-80% of the flow channel width. The flow channel is topped by the cover plate and bottomed by the base plate 1 , and the wall surface of the straight groove 11 closed by the cover plate is the top wall of the flow channel. Through the simulation calculation of flow channels with different widths, the cooling effect is the best when the groove width is 60%-80% of the flow channel width, and the depth of the groove is not greatly affected by the size of the flow channel.

As shown in Figures 3 and 4, each straight groove 11 has a plurality of channels 111, the bottom wall of each channel 111 is provided with a bottom groove, and the top wall of each channel 111 is provided with a top groove, The width of the bottom groove and the width of the top groove respectively account for 60%-80% of the width of the channel 111 where they are located. As shown in FIG. 1 and FIG. 2 , the channel 111 is divided by placing ribs 112 at equal intervals in each straight channel 11 .

As shown in Figure 6, the depth of both the top groove and the bottom groove is 0.2 mm. The cooling liquid in the too deep groove is not easy to exchange heat with the cooling liquid in the flow channel, and the degree of flow around the boundary layer of the flow channel cannot reach the maximum if it is too shallow, and the heat exchange effect of the groove with a depth of 0.2mm is the best.

In this embodiment, the top groove 14 with a width of 3.9 mm and a depth of 0.2 mm is added to the top of a 5 mm wide flow channel, and the bottom wall surface is increased with a width of 3.9 mm and a bottom groove 13 with a depth of 0.2 mm as an example, as shown in Figures 5 and 6 shown.

Fig. 5 is a schematic axial cross-sectional view of a group of three channels without grooves. It can be seen from Fig. 5 that the structure of the flow channel without grooves is 15 mm deep and 5 mm wide. Fig. 6 is an axial cross-section of the channel with grooves, and a groove structure with a width of 3.9 mm and a depth of 0.2 mm is added to the upper and lower surfaces of the channel without grooves.

According to the convective enhanced heat transfer theory, when the fluid temperature is different from the wall temperature, there must be heat exchange between the tube wall and the fluid. The thin layer where the temperature of the fluid changes significantly near the wall is called the temperature boundary layer. The fluid temperature in this boundary layer reaches 99% of the temperature in the main flow zone, as shown in Figure 7.

Introducing the concept of thermal resistance, thermal resistance is defined by formula (4.1):

In the formula: θ——thermal resistance

t1 - heat source temperature

t2——End point temperature of heat conduction system

P——heat source power

From the above formula, it can be obtained that the thermal resistance of the boundary layer accounts for 99% of the entire heat transfer process, so improving the heat transfer conditions of the boundary layer is the key to improving the heat transfer performance of the cold plate.

After grooves are added to the bottom wall and top wall of the flow channel, the boundary layer turbulence is intensified, the thickness of the boundary layer is thinned, the convective heat transfer effect is enhanced, and the temperature rise of the cold plate is reduced. At the same time, the groove increases the cross-sectional area of the flow channel, and the pressure drop is reduced under the same inlet flow rate. Figure 8 and Figure 9 show the comparison of the temperature and pressure drop cloud charts of the channel without grooves and the channel with grooves under the same inlet conditions (inlet velocity: 3.15m/s, inlet temperature: 45°C).

It can be seen from Figure 8 and Figure 9 that the pressure drop of the channel with grooves is 0.03 bar lower than that of the channel without grooves, and the maximum temperature rise is 1.74 °C lower.

In order to better illustrate the superiority of the channel with grooves, take the longitudinal section A-A (Figure 10) of the channel structure without grooves and the channel structure with grooves for analysis in fluent, showing the flow channel section Figure 11, Figure 12 and Figure 13 show the temperature contour curve, velocity contour curve and field coordination angle distribution.

It can be seen from Figure 11 and Figure 12 that the temperature inlet development section of the channel with grooves becomes longer, from 0.29m to 0.34m for the channel structure without grooves. The temperature inlet development section becomes longer, and the thickness of the temperature boundary layer becomes thinner when the axial coordinate values are equal, and the convective heat transfer is strengthened.

It can be seen from Figure 13 and Figure 14 above that the center velocity of the flow channel without grooves is 2.6m/s, and the center velocity of the flow channel with grooves is 2.8m/s. The coolant speed is high, and more heat exchange can be carried out at the same time, and more heat can be taken away.

As can be seen from Figure 15 and Figure 16, the value of the field coordination angle in the central area of the grooved flow channel becomes smaller and the distribution is more uniform. Field synergy angle is an important index to measure the synergy between temperature gradient and velocity gradient, and the smaller the value, the better the synergy between the two. It can be seen that the heat dissipation of the grooved flow channel is better than that of the non-grooved flow channel.

Example 2

The difference between this embodiment and Embodiment 1 is that the flow channel has two inlets I1, I2 and one outlet E, and the outlet E is located between the two inlets I1, I2, as shown in FIG. 17 . The flow channel is set as two inlets I1 and I2, and the coolant enters into the two inlets I1 and I2 respectively, so that the coolant only needs to flow from any inlet to the outlet, without completely flowing through the entire flow channel, the cooling liquid The pressure drop is greatly reduced.

Outlet E is located at 1/2 of the runner stroke. The stroke of the coolant from the inlets I1 and I2 to the outlet E is 1/2 of the length of the flow channel, so the distance traveled by the coolant in the cold plate is reduced by half, and the pressure drop of the coolant is greatly reduced.

The simulations in Figure 18 and Figure 19 do not have grooves in the flow channel, but only the pressure drop and temperature simulation cloud diagrams with different numbers of inlets.

After the two inlets are arranged in the flow channel, the distance traveled by the coolant in the cold plate is reduced by half, and the pressure drop is reduced. As shown in Figure 18, the pressure drop of the channel without grooves is 1.2 bar, and the maximum temperature is 59.34 °C. As shown in Figure 19, the pressure drop between the two inlet channels is 1.03 bar, and the maximum temperature is 58.94°C.

From the comparison of Figure 18 and Figure 19, it can be seen that the pressure drop of the two-inlet flow channel is 0.17 bar lower than that of the single-inlet flow channel, and the maximum temperature rise is also slightly lower.

As shown in Figure 20, the pressure drop of the inlet flow path is 1.2 bar without grooves, the maximum temperature is 59.34°C, and the temperature rise is 14.34°C.

As shown in Figure 21, the pressure drop of the channel with grooves at the 2 inlets is 0.98 bar, the maximum temperature is 56.67°C, and the temperature rise is 11.67°C.

From the comparison of Figure 20 and Figure 21, it can be seen that the pressure drop of the single-inlet flow channel with two inlets with grooves is 0.22 bar lower than that of the two-inlet flow channel without grooves, and the maximum temperature rise is lower by 2.67 °C. The pressure drop is reduced by 18.3%, the temperature rise is reduced by 18.6%, and the overall performance of the cold plate is greatly improved.

The content described in the embodiments of this specification is only an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms stated in the embodiments. Equivalent technical means that a person can think of based on the concept of the present invention.

Claims (5)

1. A liquid cold plate for cooling electronic components, including a base plate and a cover plate. There are multiple parallel straight slots on the base plate, and the adjacent straight slots are connected end to end. There is a circular arc transition with the connection groove; the straight groove on the base plate, the connection groove and the cover plate form a flow channel for the cooling liquid to flow through. It is characterized in that: a bottom groove is opened on the bottom wall of each straight groove, and the bottom The width of the groove accounts for 60%-80% of the width of the flow channel. 2. The liquid cold plate for cooling electronic components as claimed in claim 1, wherein a plurality of grooves are arranged in each straight groove, and a bottom groove is provided on the bottom wall of each groove, and each groove A top groove is provided on the top wall of the channel, and the width of the bottom groove and the width of the top groove account for 60% to 80% of the width of the channel respectively. 3. The liquid cooling plate for cooling electronic components according to claim 2, wherein the depths of the top groove and the bottom groove are both 0.2 mm. 4. The liquid cold plate for cooling electronic components according to any one of claims 1-3, wherein the flow channel has two inlets and one outlet, and the outlet is located between the two inlets. 5 . The liquid cold plate for cooling electronic components according to claim 4 , wherein the outlet is located at 1/2 of the stroke of the flow channel. 6 .