New Product Introduction
High Performance Liquid Cooling System
“SAN ACE MC Liquid”
Tomoaki Ikeda Toshiki Ogawara Masashi Miyazawa Kouji Ueno
1. Introduction
Microprocessor units (MPU), the brains of any com-
puter, are becoming faster, with more functionality and
greater capacity. The heating value from microprocessors
is increasing rapidly as a consequence. Some
microprocessors have a heating value that exceeds 100W,
leading to growing demand for better cooling perform-
ance from cooling devices.
Another requirement that has recently become more
critical is for computer equipment to generate less noise.
This has in turn made important to reduce the noise
made by cooling devices.
In response, SANYO DENKI has developed a high
performance liquid cooling system called San Ace MC
Liquid. This is a cooling device that simultaneously
achieves both high cooling performance and low noise.
This paper describes the product and introduces its
features.
2. Background to the Development
SANYO DENKI has been releasing air-cooling MPU
coolers in the SAN ACE MC series, which integrate a
cooling fan and heat sink, as cooling devices for micro-
processors.
(1)
，
(2)
，
(3)
，
(4)
The following improvements needed to be made for air
cooling MPU coolers to achieve high cooling performance:
・ Increase the surface area of the heat sink
・ Use material with high heat conduction for the heat
sink
・ Use a high air volume fan
These improvements in turn involved issues with the
enlargement and mass increase of the heat sink as well
as the increase in noise caused by the high air volume of
the fan motor. We were testing the limits of air cooling.
We then started developing a liquid cooling system as
a new cooling device to replace the air cooling MPU
cooler.
The liquid cooling system we have developed has im-
proved cooling performance and is also designed to pro-
duce less noise compared with conventional air cooling
MPU coolers. In addition, the radiator, reserve tank,
pump, and fan were integrated to improve ease of instal-
lation, maintainability, and flexibility.
The result is a product known as San Ace MC Liquid.
3. Product Features
Fig. 1 shows San Ace MC Liquid, a liquid cooling sys-
tem.
Fig. 1 Liquid Cooling System: SAN ACE MC Liquid
The features of the product are as follows:
(1) High cooling performance
Cooling performance has been improved approximately
32% at the same sound pressure level compared with air
cooling MPU coolers.
(2) Low noise
The sound pressure level has decreased approximately
23dB(A) at the same cooling performance compared with
air cooling MPU coolers.
(3) Ease installation in information devices
The same ease of installation as that of the air cooling
system has been realized by integrating the radiator, re-
serve tank, pump, and fan.
(4) High reliability and long life
An expected life of 40,000 hours was achieved without
the need to replenish cooling liquid. This is thanks to the
reliable and durable components (radiator, pump, con-
nection tube, fan, and cold plate).
(5) Flexibility
A diverse array of microprocessors and other electronic
parts can be cooled by preparing unique installation
metal fittings for the cold plate.
SANYO DENKI Technical Report No18 Nov. 2004|18
4. Introduction to the Product
Fig. 2 is a cross-section look at the SAN ACE MC Liq-
uid.
Table 1 shows a performance overview of the product.
4.1 Structure
The features of the structure and components of this
new liquid cooling system are as follows.
This product consists of a cold plate, radiator, pump,
tube, and fan. Fig. 3 shows the parts that make up this
product.
The cooling method used by SAN ACE MC Liquid is
explained below.
The heat originating from the MPU is absorbed by a
cold plate and is transmitted to the cooling liquid which
flows around the cold plate. After depriving the cold plate
of its heat, the cooling liquid itself becomes warm. So it is
sent to the radiator and cooled using the air generated by
the fan. The cooled cooling liquid circulates around the
cold plate, and once again deprives the cold plate of its
heat. An electric pump is used to circulate the cooling
liquid.
(1) Cooling Liquid
Long life coolant (hereafter, LLC) is used for the cool-
ing liquid. For the LLC, we looked at ethylene glycol and
propylene glycol, choosing propylene glycol because it has
less toxicity and is therefore superior in environmental
terms. A corrosion control solution to protect parts from
corrosion was also added.
The freezing temperature changes depending on the
density, although the LLC is used with a solution. The
freezing temperature of the propylene glycol solution is
about -35℃ with a 50% solution and -15℃ with a 30%
solution. In addition, the cooling performance changes
depending on the density. Since the higher the density,
the lower the cooling performance, we chose a 50% solu-
tion, taking into account the actual operating environ-
ment and cooling performance.
Fig. 4 shows the relationship between the density and
cooling performance of the cooling liquid.
Fig. 2 Dimensions of Liquid Cooling System SAN ACE MC Liquid
19|SANYO DENKI Technical Report No18 Nov. 2004