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Over the past 20 years, the power consumption of PC CPUs and GPUs has rapidly increased with performance improvements. Twenty years ago, the thermal design power (TDP) of mainstream PC CPUs, such as the Intel Pentium 4 and AMD Athlon XP, ranged between 50W and 90W, while GPUs like the NVIDIA GeForce 4 and ATI Radeon 9000 series consumed around 30W to 60W. Ten years ago, with the rise of multi-core processors and high-performance graphics cards, CPU power consumption increased to between 65W and 150W (e.g., Intel Core i7 and AMD FX series), and GPU power consumption reached 150W to 250W (e.g., NVIDIA GeForce GTX 600 series and AMD Radeon HD 7000 series). Today, modern high-end CPUs (such as Intel Core i9 and AMD Ryzen 9) and GPUs (such as NVIDIA GeForce RTX 3000 series and AMD Radeon RX 6000 series) have power consumption exceeding 250W and 350W, respectively.
隨著PC硬件功耗的顯著增長，對散熱效能的需求也不斷提升。傳統風冷技術，依賴風扇和散熱片通過空氣對流來帶走熱量，其散熱效率受到空氣的比熱容（約1.005 J/g·K）和熱導率（約0.026 W/m·K）的限制。根據熱傳導方程式 Q=h⋅A⋅ΔT，其中 Q 是散熱量，h 是對流換熱係數，A 是散熱面積，ΔT是溫差，要提高散熱效果，可以增加散熱片的表面積（A）或增大風扇的風量以提高對流換熱係數（h）。然而，隨著功耗的增加，風冷系統的體積和噪音也必然增大，這使得高效風冷系統越來越笨重且難以實現高效安靜的運行。
In contrast, liquid cooling technology uses coolants (such as water or glycol mixtures) with a higher specific heat capacity (approximately 4.186 J/g·K) and greater thermal conductivity (about 0.6 W/m·K), allowing for more heat absorption and transfer at the same temperature difference. According to the same heat transfer equation, liquid cooling systems can achieve higher cooling efficiency with smaller volume and lower noise. When greater cooling capacity is required, air cooling solutions often become too bulky and noisy due to the need for large heatsinks and high airflow fans. In comparison, liquid cooling systems can achieve superior cooling performance with a more compact design.
As a result, with the increasing power consumption of PC hardware, air cooling technology has gradually struggled to meet these demands, especially in high-performance and high-density applications. The rise of liquid cooling technology addresses this challenge by offering more efficient and quieter cooling solutions, making it the mainstream choice for cooling future high-performance computing devices.
The Evolution and Key Aspects of Modern Liquid Cooling Technology
Compared to other cooling technologies, such as air cooling and passive cooling, liquid cooling offers several significant advantages. Firstly, the high heat capacity and thermal conductivity of liquids enable liquid cooling systems to absorb and dissipate heat more quickly and efficiently, which is particularly important for high-power, high-heat-density devices. Secondly, liquid cooling systems typically operate more quietly, as they rely on coolant circulation rather than high-speed fans to remove heat, making them ideal for applications that require a quiet environment, such as home entertainment systems or audio workstations. Additionally, liquid cooling technology provides better long-term stability and reliability, as liquid cooling systems are less susceptible to dust and particulate interference.
The core of modern liquid cooling technology lies in its design diversity and high scalability. A typical liquid cooling system consists of key components such as a cold plate or water block, coolant, pump, and radiator. The cold plate, usually made of high thermal conductivity materials like copper or aluminum, directly contacts the heat-generating components, absorbing heat and transferring it away through the coolant flow. The pump's role is to circulate the coolant throughout the system, ensuring that heat is removed quickly and efficiently. With technological advancements, modern liquid cooling systems have also incorporated digital control technologies and sensors to precisely regulate the coolant flow rate and temperature, further optimizing cooling performance.
In addition to traditional single-phase liquid cooling systems, the rise of two-phase liquid cooling technology marks a significant development in the liquid cooling field. Two-phase liquid cooling utilizes the phase change process of the coolant (such as vaporization and condensation) to enhance heat transfer efficiency. This type of system can operate at higher heat flux densities, making it particularly suitable for devices that require sustained high-load operation, such as data center servers and supercomputing clusters.
Design and Operating Principles of Liquid Cooling Systems
The diversity of liquid cooling technology is reflected in its various design options. The main types of liquid cooling mechanisms include cold plate liquid cooling, immersion cooling, and single/dual-phase liquid cooling systems, each with its unique operating principles and design considerations.
Cold plate liquid coolingis currently the most common liquid cooling technology, typically used for cooling high-heat components such as CPUs and GPUs. Its design principle involves using a cold plate that is in close contact with electronic components. The coolant flows through channels within the cold plate, absorbing and carrying away heat. The heat is then transferred to a radiator (usually equipped with fans), where the coolant exchanges heat with the external air and dissipates it. This cooling method provides targeted cooling, making it particularly suitable for cooling localized high-heat areas. Additionally, cold plate liquid cooling systems can be designed with a modular structure, making them easy to maintain and upgrade.
Immersion coolinginvolves submerging entire electronic devices (such as servers or supercomputer racks) directly into non-conductive coolants (such as fluorinated liquids or mineral oils). This design maximizes cooling efficiency because the coolant can directly contact all heat-generating components. After absorbing heat, natural convection or a coolant circulation system transfers the heat to an external radiator or condenser, where it is released into the environment. Immersion cooling systems are particularly suited for high-density, high-performance computing environments, such as large data centers. Although the initial installation cost of immersion cooling is relatively high, its operational efficiency and lower long-term running costs make it a compelling option for the future of data centers.
Single-phase liquid coolingis a cooling method where the coolant remains in a liquid state throughout the system. Whether it's cold plate liquid cooling or immersion cooling, as long as the coolant stays in a liquid form during operation without undergoing a phase change (such as from liquid to gas), it is considered a single-phase liquid cooling system.
Two-phase liquid coolingutilizes the phase change of the coolant from liquid to gas during the heat absorption process to carry away a large amount of heat. When the coolant vaporizes, the heat is transferred along with the vapor to a condenser, where it cools and condenses back into a liquid, completing the coolant cycle. Two-phase liquid cooling can achieve efficient heat dissipation at relatively low coolant flow rates because the phase change processes (such as evaporation and condensation) absorb and release significant amounts of heat, greatly enhancing the thermal conductivity of the entire system. This technology provides extremely high cooling efficiency in environments with high heat flux density, making it ideal for computing systems that require exceptional cooling performance, such as in fields like financial modeling, weather forecasting, and genomics research.
Development Challenges and Technological Breakthroughs
Cost:
The primary issue with liquid cooling systems is cost. Liquid cooling systems are more complex than air cooling, requiring additional components such as pumps, tubing, and radiators, as well as more precise installation and maintenance, all of which increase initial installation and operating costs.
Beyond the system's intrinsic costs, peripheral costs must also be considered. In liquid cooling systems, the conductivity of the coolant may increase over time, often due to dissolved impurities, corrosion products, or ions released from materials. Higher conductivity raises the risk of electrical leakage, potentially leading to short circuits or damage to electronic components. Therefore, essential equipment for real-time monitoring of conductivity changes, chemical analysis, and pH levels is indispensable.
Coolant:
The selection and development of coolants have become a core focus for the further advancement of liquid cooling technology. Traditional coolants, such as water and glycol-based mixtures (PG25), offer good thermal performance but have issues related to conductivity, electrochemical corrosion, and environmental impact, especially when in contact with aluminum. Future research will focus on developing new types of coolants that not only provide higher thermal conductivity and lower electrical conductivity but also meet higher standards of environmental friendliness and safety.
Sealing Design:
Secondly, the long-term stability and sealing of liquid cooling systems are also significant challenges. Coolant leaks can cause corrosion of metal components, releasing iron elements, which increase the conductivity of the liquid and form "electrical bridges" that can short-circuit and damage electronic equipment, potentially causing data center outages. Therefore, improving the sealing technology of liquid cooling systems and ensuring long-term stable operation is a crucial issue in the development of liquid cooling technology. Future advancements may involve the use of new materials, such as high-strength sealing materials and self-healing materials, to enhance system reliability.
Development Direction:
The trend in liquid cooling technology will move towards miniaturization, intelligence, and modularity. With further technological advancements and cost reductions, liquid cooling is expected to become more widespread and a standard cooling solution for everything from home PCs to large data centers. Its applications will be particularly extensive in areas requiring large-scale data processing and high-performance computing, such as AI training, deep learning, and edge computing. Future liquid cooling systems may also integrate IoT and AI technologies to enable intelligent monitoring and management of the cooling process, further enhancing system energy efficiency and operational effectiveness.
