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Sunon Liquid Circulation Cooling (LCC) System

View Waturbo Liquid Circulation Video

Within the past two to three years, the personal computer market has seen the introduction and usage of liquid cooling for both desktop and notebook applications.  Some mainstream examples of this cooling technology can be found in the systems of Apple and NEC on the desktop side as well as Hitachi on the notebook side.

The need for this kind of cooling technology is being driven by the thermal challenges that are associated with ever increasing processor speeds.  As CPUs and associated electronics become faster, and hotter, the ability to dissipate this heat with conventional air cooling devices is becoming increasingly difficult.  Even when the heat can be removed with active air cooling devices, the price that must be paid with noisier acoustics (due to the high fan speeds required) is often unacceptable to both the system designer and the product end user.

With increased thermal efficiency provided by a liquid heat transfer medium, liquid circulation cooling does offer significant cooling advantages over conventional air cooling.  Presently, however, there are still several key limitations of liquid cooling that have prevented its widespread adoption by the majority of the mainstream desktop and notebook computer makers. 

Two of these limitations are as follow:

  1. Cost:  The structure of the traditional liquid cooling system is shown in Fig. 1.  Required components include a pump, heat exchanger, radiator, fan, reserve tank, and some form of conduit (typically a rubber tube) to connect all of these parts.  All of this additional equipment can result in an 8X to 10X increase in the costs of the system’s cooling system (when compared to conventional air cooling). 
  2. Leakage:  All of the above components must be connected to each other with a rubber tube, resulting in a minimum of 8 connection joints.  That means that the cooling fluid (typically water) that runs through this system has a minimum of 8 different locations where a leak is possible, not to mention the possibility of leaks occurring somewhere in the tubing itself.  The fear of water leakage in the computer is enough to prevent some users/designers from adopting this technology.

The greater cost of the system, coupled with the higher risk of a system failure due to leakage, are significant factors that can mitigate the thermal advantages of liquid cooling.

In an attempt to bring to the mainstream market the thermal advantages offered by liquid cooling, while addressing the above limitations, Sunon has developed a unique Liquid Circulation Cooling System, under the brand name Waturbo.

The structure of the Sunon Waturbo (TM) liquid circulation cooling system is demonstrated by Fig. 2.  The five key components of the traditional liquid cooling system are still represented:  a pump, heat exchanger, radiator, fan, and reserve tank.  In the Sunon Waturbo system, however, four of those components (everything but the fan) are packaged in a single, sealed liquid-holding radiator device.  This radiator device is sandwiched between the fan (the active cooler, which also drives the pump) and the CPU (the heat generating device in the system). 

What is missing is all of the rubber tubing that connects the different components in the traditional liquid cooling system.  By eliminating the rubber tubing, and all of the connection joints with the different components, the risk of leakage has been drastically reduced.   The only possible sources for leakage now are the top and bottom of the radiator device, which interface with the fan and CPU respectively.  These two junction points are more easily sealing with the use of standard O-Rings.

The Sunon Waturbo system works as follows:

The exterior fan (item 4) drives the interior pump (item 1) which circulates the cooling water inside the sealed liquid reserve tank (item 5).  This circulating water allows the heat exchanger (item 2) at the bottom of the reserve tank to efficiently remove the heat from the CPU.  The corresponding temperature increase of the cooling water is dissipated to the outside through the radiator fins (item 3).

The fact that the Sunon Waturbo system uses the fan motor to drive the liquid pump is significant.  This dual-action of the fan motor eliminates the need for a separate motor to drive the pump, as is used with the traditional liquid cooling system.  On the Sunon Waturbo, the driving torque of the fan impeller is transmitted to the liquid pump through a magnetic coupling.  This means that no pump motor or other electronic parts are required in the cooling water.  All of this results in a lower risk and lower costs of the Sunon Waturbo system, when compared to the traditional liquid cooling system. 

In a conventional air cooling system, the distance between the heat source (CPU) and the heat dissipater (radiator fin) is critical.  In practice, a fin that is located at a further distance from the CPU heat source will have a lower fin temperature, resulting in a less efficient thermal system design. 

In contrast, the Sunon Waturbo system utilizes forced liquid convection to transfer the CPU heat to the radiator fin.  Therefore, there is no significant distance effect between CPU and radiator fin and it is possible to keep the fin temperatures stable and obtain an overall increase in thermal efficiency.

Sunon has currently developed and tested the Waturbo technology in desktop computer liquid cooling systems.  Similar Waturbo applications are currently under development for both notebook and server applications. 

Figure 3 shows a comparison of test data between a desktop computer that uses a conventional air cooling system and the same computer as cooled by the Sunon Waturbo  cooling system.  The data measured in this test include CPU temperature (in deg. C) and system acoustic noise (in dBA).  Not surprisingly, the Sunon Waturbo liquid circulation cooling system results in a lower CPU temperature than was provided by the original air cooling system.  Perhaps of even greater significance, this improved cooling performance was also associated with an overall decrease in system acoustic noise.  This is due to the fact that the improved cooling efficiency and performance of the Sunon Waturbo system allows the active fan to run at a lower speed, thereby lowering the associated fan speed acoustic noise.  This has particular advantages in the consumer computer industry where acoustic noise performance has become a major problem as conventional air coolers are required to run at such high speeds. 

List of Figures:

Fig. 1:  Traditional Liquid Cooling System


Fig. 2:  Sunon Waturbo Liquid Circulation Cooling (LCC) system



Fig. 3:  Sunon Cooler vs. Original Cooler chart, temperature and acoustic comparison