The entire liquid cooling system includes components such as liquid cooling plates, liquid cooling media, pumps, water pipes, and radiators. Generally speaking, the thermophysical properties of commonly used liquid cooled working fluids are shown in the following table：
From the above table, it can be seen that the selection of liquid cooling medium has a fixed impact on the heat dissipation efficiency of the entire system. Without changing other conditions, priority should be given to media that meet environmental requirements (altitude, ambient temperature, etc.) and have low cost. However, the liquid cooling plate is also an important part of the liquid cooling heat dissipation system, which is the heat exchange component of the liquid cooling system. It has an internal heat exchange groove structure, namely the flow channel. The differences in internal flow channel design have a significant impact on the heat transfer efficiency of the entire system, and there are significant variables involved.So, we won’t discuss the medium of liquid cooling. Let’s take pure water as an example to analyze the design and optimization ideas of the flow channel of the liquid cooling plate.
In the structural design of liquid cooling plates, the following points need to be considered:,
Heat transfer performance requirements: Under the setting of flow rate and inlet and outlet water temperature difference, achieve the temperature rise target of the heat source, as well as the thermal resistance target of the radiator, and the requirements for its heat transfer performance; Strength and
Pressure requirements: Some projects may require special instructions on the surface pressure and overall stress situation of the liquid cold plate due to the usage environment and installation requirements inside the system.
Anti corrosion requirements: Long term flow of liquid cooling medium in the channel will be affected by high temperature, which will aggravate the damage of metal materials, even blockage, and affect the heat dissipation efficiency;
Leak prevention requirements: The design of the cover plate, upper and lower end faces, sealing strips, and even Friction Stir Welding or Brazing welding methods can all achieve leak prevention measures; Low cost requirements: Reduce the costs caused by pump pressure, working hours, etc. from the dimensions of production and processing feasibility, material selection, process complexity, flow resistance, thermal resistance, etc.In order to meet the above requirements, comprehensive design considerations need to be made from materials, structural design, manufacturing methods, and other aspects.
The material of the liquid cooling plate affects the heat transfer performance between the waterway and the cooling water. Using materials with high thermal conductivity to make the liquid cooling plate can effectively reduce the overall thermal resistance of the system. The common material properties represented by aluminum and copper are shown in the table below:
Aluminum alloy, as the most commonly used heat dissipation material, has advantages such as high thermal conductivity, low density, good processing performance, good corrosion resistance, and good physical and mechanical properties. The anti-corrosion process of aluminum profiles is mature, which can ensure the long-term reliable use of water-cooled plates.The materials used for aluminum heat sinks in electronic products are the 50 and 60 series, such as AL5051606016063, which have good thermal conductivity, corrosion resistance, and processing performance. They are suitable for anodizing and CNC machining of complex flow channels.
The research here focuses on the ideas and methods for designing and optimizing the flow channels of water-cooled plates under the premise of determining the water flow rate and basic pressure drop requirements. The basic styles of liquid cold plate flow channels are mainly divided into flat, W-shaped, circular, cylindrical, Archimedean spiral waterway, etc. Below are brief explanations according to the diagram.
A liquid cooling plate with A Planar Flow Channel has several key features. It offers a smooth and consistent flow path. The design allows for efficient heat transfer due to good contact with the coolant. It is often structurally simple, facilitating manufacturing, and can provide reliable cooling in various applications. As shown in the figure above, the inlet and outlet have a simple structure on both sides.
The liquid cold plate, with a W – Shaped Flow Channel, has many advantages in fluid cooling. Structurally, the W – shaped flow channel increases the contact area between the fluid and the cold plate and extends the flow path of the fluid. This allows heat to be absorbed more fully and improves the efficiency of heat exchange. In terms of fluid flow, it can make the fluid form a more complex flow state, reduce laminar flow, enhance turbulence, and make heat transfer more uniform and rapid. This design can effectively reduce the risk of local overheating and make the entire cooling system operate more stably, which is suitable for scenarios with high heat dissipation requirements.
The Annular Flow Channel of the liquid cold plate has several advantages. Firstly, the annular structure enables the coolant to circulate, forming a stable and continuous cooling circuit, ensuring that heat is evenly removed. This uniform heat transfer can prevent local overheating and protect the electronic components and other equipment in contact with it. Moreover, the annular flow channel can make the flow of the coolant more regular, reducing the unstable factors caused by turbulence and decreasing the fluid resistance, making the cooling process more efficient. At the same time, the design of the annular flow channel is relatively simple, which is convenient for processing and manufacturing and has a lower cost.
The liquid cooling plate adopts the characteristics of Archimedes spiral flow channel, which efficiently dissipates heat. The spiral shape makes the flow path of the cooling liquid in the flow channel longer and the contact area larger, which can fully absorb heat, achieve efficient heat exchange, and effectively reduce temperature. In terms of fluid mechanics, it can guide the coolant to flow smoothly, reduce flow turbulence and local velocity fluctuations, thereby reducing fluid noise and pressure loss.
Through various combinations, many unexpected effects can be achieved. Our engineers will compile the thermal analysis of these channels for our reference in the future. For the design of these channels, they are also several typical water-cooled channel designs. Let’s take a look at the optimization design ideas for them.
Adding circuits: After preliminary planning of the liquid flow channel design, numerical simulation revealed that the heat dissipation efficiency did not meet the requirements and the thermal resistance was high. In this case, adding circuits can be considered, such as changing from single cycle to double cycle, or even more, to enhance heat transfer;
Increasing heat dissipation area: If the internal structural space allows, cylindrical or square ribs can be appropriately added inside the flow channel for optimization in a staggered or sequential manner;
Optimize internal water flow velocity: When the cross-sectional area of the inlet is constant, the larger the cross-sectional area of the internal water flow channel, the lower its velocity, which is not conducive to rapid heat transfer. Of course, it is not enough to simply reduce the cross-sectional area to promote flow velocity, as this will lead to increased flow resistance;
Balanced water cooling area: Try to evenly cover the contact surface of the heat source with the flow channel. In special cases where the area and space are small, Archimedes spiral waterway is a good choice; Avoiding short circuits: When the inlet and outlet are very close, the rib structure of the waterway design is often used to extend the waterway and distribute it directly below the heat source, avoiding direct water flow from the inlet to the outlet;
Avoid excessive water flow: In situations where the distribution of heat sources is relatively special, such as vertical layering, the general design concept may be a flow channel, from bottom to top or from top to bottom, but it may cause an increase in the temperature difference between the rear and front ends. In this case, separate cooling by layering can be considered;
Try to minimize bends and have smooth transitions: bends increase head loss and enhance internal flow resistance. If unavoidable, try to have smooth transitions in bends to enhance heat dissipation and reduce pressure drop.
Of course, when conducting the above optimization design, it is necessary to simultaneously confirm whether the internal flow resistance, thermal resistance, structural strength (surface pressure, etc.) of the system meet the actual requirements and limitations of the project, while considering the feasibility of production and processing as much as possible, as well as cost. On the basis of the original project, assuming that the waterway is optimized by increasing the internal heat dissipation area, reducing the cross-sectional area, and increasing the circuit, the theoretical results are calculated separately; Based on the analysis results, establish multiple waterway design models and conduct simulation in the required environment. Compare and analyze the simulation results, establish experimental models and tests, and verify the results of hypothesis analysis and numerical simulation. Any optimization design can be contacted by our engineers at KENFA TECH.
