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:
- 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).
- 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
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