Liquid cooling，water cooling
I) What is liquid cooling?
Liquid cooling is a cooling method that uses a liquid with high specific heat capacity as a heat transfer mass to meet the cooling needs of various machinery and electronic equipment. It is an effective way to eliminate high thermal loads on equipment, where overheating may reduce the reliability of the equipment. Liquid cooling technology is not widely used only recently, in the 1960s, IBM's mainframe computer used water cooling technology. Currently liquid cooling technology is mainly used to cool high power electronic equipment in many industries, including medical, military and defense, laser, data center, semiconductor, transportation, printing, etc.
II) the reasons for using liquid cooling
The traditional cooling method of electronic equipment is heat transfer through the air, the technical solution is good to decouple the electronic equipment and cooling equipment, thus enabling the diversification of the form of cooling system, but due to the small specific heat capacity of air, volume flow is limited by the size of the server air inlet, heat transfer capacity is limited. Compared to air cooling, the advantages of liquid cooling are as follows.
1) Powerful heat carrying capacity, heat directional movement
2) Heat transfer through the active flow of heat-carrying medium, lower temperature difference between the heating and cooling ends
3) Quiet and environmental protection, sealed and dustproof
4) Real-time monitoring, safe to use
5) Suitable for high power density, high heat flow density, low thermal resistance
6) Separation of the heat sink and the heat sink, the temperature inhomogeneity of different locations in the system is relatively weaker and more flexible in use
(7) The volume specific heat capacity of the work material is large, which can buffer the thermal shock and reduce the temperature change rate of the heat generating element.
Naturally, in order to improve the heat transfer efficiency, the use of higher specific heat capacity of the heat transfer medium, larger contact heat transfer area, greater heat transfer volume flow of liquid cooling solution has become an inevitable choice to improve the efficiency of refrigeration. The following is a comparison of the physical properties of water and air at 50 degrees Celsius.
|Physical parameters||water||dry air|
|specific heat capacity (kJ/(kg*k))||4.174||1.005|
|Thermal Conductivity (W/M*K)||0.648||0.0283|
|Kinematic viscosity (x10^-6 m^2/s)||0.558||17.95|
III) Types of liquid cooling system
In contact liquid cooling, the coolant can be in direct contact with the heating device, the specific implementation of contact liquid cooling technology mainly includes immersion and spray liquid cooling, the typical solution of non-contact liquid cooling technology is cold plate liquid cooling.
Immersion liquid cooling is a technology that completely immerses IT equipment in cooling liquid to achieve heat dissipation. The submerged liquid cooling system has a simple structure, saves the core components of the refrigeration system such as the compressor, and saves the two processes of air and water exchange in the original water-cooled air-cooled system. Low power consumption is achieved (large heat exchange, so the required flow rate is low, and the pump power consumption is low), and the PUE of the cooling part can reach 1.04. However, immersion liquid cooling often requires customized transformation and design of IT equipment, and the transformation of the existing IT infrastructure in the computer room is relatively large and technically difficult.
The spray type liquid cooling allows the cooling liquid to spray the heating body by storing liquid at the top of the case and opening holes. The spray type liquid cooling modifies the case to a lesser extent, but during the cooling process, the cooling liquid may escape when exposed to high temperatures. and evaporation, these droplets may reduce the cleanliness of the equipment room and affect other equipment in the equipment room after the droplets are emitted to the outside of the case through the holes of the case.
The cold plate liquid cooling technology also has a relatively small transformation range on the server, and has high safety, and is very suitable for other industries including medical, military and defense, laser, data center, semiconductor, transportation, printing and other industries.
Immersion liquid cooling
Cold plate liquid cooling
Among the above three liquid cooling technology solutions, the cold plate liquid cooling technology is the earliest and most popular liquid cooling cooling method, and its operability and market maturity are relatively high. Since the temperature in Germany is below 35 degrees all year round, the supercomputing center has achieved the effect of natural cooling throughout the year, which is the industry benchmark for green HPC systems. Resources.
Ⅳ) the main types of cold plate liquid cooling system, and the main components that make up the system
The cooling plate type liquid cooling mainly transmits the heat from the heat generating devices (such as CPU, IGBT, FBGA, PA, Battery, etc.) indirectly to the coolant enclosed in the circulating pipeline through the closed cavity formed by the cooling plate (copper, aluminum and other highly thermally conductive metals), and the coolant in the pipeline (usually pure water, ethylene glycol and propylene glycol solutions are used for antifreeze requirements, deionized water or transformer oil, etc.) is driven by a pump and transported to the heat exchanger through the connected piping, where the heat is quickly transferred to the environment by forced convection from a fan, thus achieving the purpose of heat dissipation.
Cold plate liquid cooling systems can be classified as open liquid cooling systems, semi-open liquid cooling systems and closed liquid cooling systems according to their structure. Open liquid cooling systems generally use natural body of water for the coolant, and the heat exchanger is only used as an auxiliary, or no heat exchanger is used. The advantages are low system pressure, low risk of leakage and flexible composition. The disadvantage is that the volume is too large and limited by the environment. Semi-open liquid cooling system generally consists of cold plate, pump, heat exchanger, piping and water tank, where the water tank serves to supplement the small amount of coolant evaporated during the long-term operation of the system and as a discharge and storage area for the air bubbles generated during the operation of the system. Enclosed liquid cooling system has less tank parts than semi-open liquid cooling, the structure is more compact and the coolant can meet the requirements of changes (impurities, microorganisms, oxidation, insulation requirements, etc.). However, it generally requires a stagnant water area or venting tank in the cold plate area to handle and store the air bubbles. Large systems in long-term operation also require additional expansion tanks and pressure relief valves to maintain pressure, temperature and pressure sensors for monitoring, and backup pumps to prevent system operation failure.
Closed liquid cooling system
There are two main types of cold plate liquid cooling systems depending on the cooling method.
1) Single cycle liquid cooling system, typical structure is the coolant is transferred directly to the environment through the heat exchanger, the structure is relatively simple and cheap. However, the temperature of the coolant entering the cold plate will be higher than the ambient temperature.
2) Double cycle liquid cooling system, the typical structure is that the coolant flows into the chiller tank and enters the second cycle through the coil of the chiller tank. After the coil absorbs heat, the heat is transferred to the heat exchanger by driving the refrigerant through the compressor, and the heat is quickly transferred to the environment through the forced convection of the fan. Due to the phase change principle used in the heat transfer process of the refrigerant, the temperature of the coolant entering the cold plate from the tank can be lower than the ambient temperature, and can reach a low temperature of -30-40 degrees Celsius after using the correct anti-freeze coolant (ethylene glycol and propylene glycol solution).However, it is more expensive, with lower cooling efficiency and higher energy consumption.
Dual circulation liquid cooling system
No matter how the structure of the liquid cooling system changes, the main components of the system are: pump, piping, heat exchanger or chiller, water tank (optional), and liquid cooling plate. Among them, pumps, pipes, heat exchangers or chillers, water tanks are standardized, we can use the simulation design according to the needs of the product, according to the parameters derived from the simulation to choose (arbitrary choice of heat exchangers will lead to high temperature or waste of energy, coolant temperature fluctuations are too large and other problems; arbitrary choice of pumps, head and flow rate is too small, the system can not start or flow rate is too small resulting in cold plate temperature (Too high, or even cavitation phenomenon, resulting in pump damage or reduced service life.) Please see Liquid Cooling Design for details. At present, Regis Heat sink has developed a modular liquid cooling cooling module for the convenience of customers. It integrates a pump, a pipeline, a heat exchanger and a water tank. The user only needs to connect the liquid cooling plate with the pipeline and start working immediately. Customers can choose liquid cooling modules with different cooling power according to the cooling requirements, which is very convenient and fast. Only the liquid cooling plate needs customized design due to the variety of products and the influence of the use environment and installation space.
Ⅴ) What is a liquid cooling plate? Main types of liquid cooling plates
1) The liquid-cooling plate is the core component of the liquid-cooling system. The fluid channel is arranged inside the plate-shaped and strip-shaped metal with a compact and relatively thin structure, so that the convective heat exchange between the fluid and the plate wall is carried out, thereby dissipating the large surface of the liquid-cooling plate. Thermal power consumption of power electronics. Compared with the air-cooled system, under the same temperature rise and volume flow, the heat absorption capacity of water is about 3750 times that of air, so the water-cooled system has a good heat load capacity. It is mainly used to meet the installation and heat dissipation requirements of electronic devices with high power density such as IGBT, CPU, GPU, SVG, resistor, PA, FPGA, and Battery.
Regis Heat sink is one of the leading liquid cooling plate manufacturers in China, our thermal design and thermal management engineers have 15 years of rich experience in liquid cooling system research and development and liquid cooling plate process production, and can provide a full range of liquid cooling solutions solution, and provide you with the thermal design and structural design of the liquid-cooled plate/water-cooled plate for free. One-stop supporting service for water-cooled plate cooling system assembly design and water connection
2) Liquid cold plate is divided into vacuum brazing liquid cold plates, friction stir welding liquid cold plates, deep hole drilling liquid cold plate, inflatable liquid cold plate, ordinary embedded liquid cold plate, contact type liquid cold plate according to the processing technology and structure. Embedded tube type liquid-cooling plates, aluminum extrusion channel type liquid-cooling plate, die-casting liquid-cooling plate, buried pipe pouring type liquid-cooling plate, etc. For specific product introduction and technical parameters, please refer to the following product details page.