Why Liquid Cooling Instead of Air Cooling — How Liquid Cold Plates Work?

The core working principle of a liquid cooling plate is to efficiently transfer heat from solid surfaces through forced convective heat transfer, utilizing the high specific heat capacity and convective heat transfer characteristics of cooling fluids. The detailed process is as follows:

Heat-generating components are tightly attached to one or more surfaces of the liquid cooling plate (commonly known as the mounting surface or base plate) using thermal interface materials such as thermal grease, thermal pads, solder, and other thermally conductive media. Heat is transferred from the heat source to the solid wall of the liquid cooling plate through thermal conduction.

Heat travels within the metallic structure of the liquid cooling plate (typically aluminum, copper, or other high-conductivity alloys) by means of thermal conduction, moving from the high-temperature mounting surface in contact with the heat source to the low-temperature inner walls of the internal flow channels that interact with the coolant. Higher thermal conductivity of the material and thinner wall thickness reduce thermal resistance and improve heat conduction efficiency.

This is the most critical stage. The coolant, usually deionized water, aqueous glycol solution, or specialized industrial coolant, flows through the sealed internal channels of the liquid cooling plate at a controlled velocity driven by an external pump. As it passes over the high-temperature inner channel walls, the coolant absorbs heat from the wall surfaces.

Heat transfer relies primarily on forced convection: the flow of the coolant, especially in a turbulent state, disrupts the laminar boundary layer near the wall surfaces, enabling more efficient mixing and heat exchange between the core cold fluid and the hot wall. A higher convective heat transfer coefficient corresponds to stronger heat exchange performance.

The design of the flow channels, including shape, dimensions, and surface enhancements such as fins or pin fins, directly affects the flow regime (laminar or turbulent), heat exchange area, and convective heat transfer coefficient, ultimately determining the overall heat dissipation efficiency.

After absorbing heat, the temperature of the coolant increases, and it exits the liquid cooling plate through the outlet port.

The heat-carrying high-temperature coolant is pumped to an external heat exchanger within the system, such as an air-cooled radiator, water-cooled condenser, or secondary cooling plate. Inside the heat exchanger, heat from the coolant is ultimately dissipated into the ambient environment through air or water cooling. The cooled low-temperature coolant is then recirculated back to the inlet of the liquid cooling plate, completing the closed-loop cycle.

• High-Efficiency Heat Transfer Medium: Liquids possess a significantly higher specific heat capacity than air (water’s specific heat capacity is approximately four times that of air), allowing far greater heat absorption per unit volume. The convective heat transfer coefficient of liquids, especially water, is also dozens to hundreds of times higher than air, resulting in much faster heat transfer rates under the same temperature difference.

• Low Thermal Resistance Path: The liquid cooling plate provides a low-resistance thermal pathway from the heat source to the coolant, supported by high-thermal-conductivity materials and optimized structural engineering.

• Enhanced Heat Transfer via Forced Convection: Pump-driven forced flow and optimized channel designs that generate turbulence and expand heat exchange area greatly strengthen heat transfer between the fluid and solid walls.

• Improved Temperature Uniformity: Well-designed channel layouts, such as serpentine or multi-branch configurations, improve temperature uniformity across the liquid cooling plate surface and prevent localized overheating.