Exploring Cold Plate Liquid Cooling Technology and Its Role in Data Center Thermal Management

Introduction

The rapid evolution of technology in today's landscape has fueled the growth of data centers, propelled by advancements like 5G mobile communication, big data, and cloud computing. This expansion has led to a substantial increase in both the size and capacity of data centers. Consequently, the electronic devices housed within these centers have become highly integrated, resulting in a significant surge in heat generation power and heat flow density. While traditional data centers typically consume around 7 kW per rack, the advent of high-performance servers has pushed this figure to 50 kW per rack, with expectations of surpassing 100 kW within the next five years. This escalation in power density has brought the challenge of heat dissipation to the forefront, posing a significant obstacle to the sustainable development of data centers.

The cooling system plays a critical role in managing the heat generated by electronic devices, ensuring they operate within the required temperature range. However, it also accounts for over 40% of a data center's energy consumption, making it one of the most energy-intensive components. Therefore, the adoption of efficient cooling technology is essential not only to prevent electronics from overheating but also to reduce overall energy consumption. Traditional air-cooled technology has proven inadequate in meeting the heat dissipation demands of high-power data centers, often resulting in issues such as localized hot spots and excessive energy usage.

Liquid cooling technology emerges as a promising alternative, offering specific heat capacities 1,000–3,500 times greater than that of air, and thermal conductivities 15–25 times higher than those of air. With its superior reliability and lower energy consumption, liquid cooling technology is better equipped to address the cooling requirements of modern high-density data centers. Among various liquid cooling technologies, cold plate-based liquid refrigeration technology stands out as the earliest and most widely adopted method, delivering significantly superior cooling effects compared to air-cooled technology.

In practical applications, integrating cold plate liquid cooling technology with air cooling systems facilitates rapid heat removal from servers while effectively reducing the power usage effectiveness of the data center. This combined approach is considered the primary technical solution for tackling the challenges posed by high heat flow and power consumption in data center cooling systems.

This paper provides an overview of the development status of cold plate-based liquid refrigeration technology and discusses the potential issues and challenges in its future application, laying the groundwork for the construction of green and high-efficiency data centers.

Development Status of Cold Plate Liquid Cooling Technology

The standard cold plate-based liquid refrigeration system primarily consists of a cold plate, a cooling distribution unit, a circulating pump, and a chiller. This technology transports heat from electronic devices to the coolant in the circulating pipe via the cold plate, and the coolant then conveys the heat to the chiller, where it is dissipated to the external environment or recycled.

In the cooling system based on cold plate liquid refrigeration technology, the coolant does not directly contact the server, making it an indirect liquid cooling technology. Depending on whether the coolant undergoes evaporation in the cold plate, this technology can be categorized into single-phase and two-phase cooling plate-based liquid refrigeration technology. Water-cooled backplanes are commonly used in cold plate cooling technology, with open and closed water-cooled backplanes being the two main types. 

Open water-cooled backplanes can achieve a cooling power of 8–12 kW, while closed water-cooled backplanes circulate air inside the closed cabinet, offering high cooling utilization and a cooling power of 12–35 kW. Compared to backplanes based on traditional air-cooled methods, data center cabinets with enclosed water-cooled backplanes can save nearly 35% of annual energy consumption and enable precise cooling. The closed water-cooled backplane technology can optimize existing open cabinets, enhance the cooling system's capabilities, reduce data center power consumption, and lower the data center's Power Usage Effectiveness (PUE). 

IBM's cabinet based on the closed water-cooled backplane successfully meets the heat dissipation requirements of high heat flux servers, with its heat cooling efficiency being 80% higher than that of single-fold air-cooled technology. While these solutions enable precise cooling for specific cabinets and address the heat dissipation challenges of high-heat flux cabinets, they may come with drawbacks such as high customization costs and maintenance.