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June 24, 2014

Thermal Design in Computer Cases


Thermal Design In Computer Cases

 Since the 1950s, people have turned to the computer for help in solving problems. As more organizations bring computers into workplace, more people become exposed to what computers can do and acquire more computer skills. As early as elementary school, children are using computers to write stories and do math. As a result, computers influence the way many people think about and approach problems. The average people depend on, are served by, or actually operate some type of computer several times each day.
Over the 50 years, computer hardware has changed significantly. Once hardware can fill several floors of a large office building, now it can fit in a person’s palm. Many innovations have been adopted in computer hardware; in fact computer is the most important and innovative invention of this century. The continuous innovation in the field of computer processors needs special hardware for these processors (Danielson, Krajewski and Brost). For example the new 3.2E GHz Pentium IV processor of Intel needs extra cooling because it heat up the computer case after 2 to 3 hours continuous running. This has arisen the requirement for thermally advantaged computer cases. Thermal power is not new for computer peripherals. It is already used in some computer hardware. For example thermal printer uses heated dot-matrix wires to print output on specially treated paper. 
The extra heat generated by new Intel processors is due to the extra power consumption. Thermal output of Intel Pentium IV processors is 82W with Hyper Threading, which can go up to 150W in continuous and extensive use (Saarinen). Its much more heat to be managed and controlled by conventional cooling methods. According to the guidelines provided by Intel for thermally advantaged computer cases, it must be T-ambient temperature below 38C. 

Conventional Cooling of Computer Systems

Air-cooling of computer systems is the conventional way of cooling a computer. It worked well and most effectively when processor power is limited to 1.5 to 2.0 GHz but for processors more than 3 GHz speed, this cooling technique looked pretty useless. This cooling-technique uses a metal structure, usually made up of copper to remove heat from the system.  A fan is also used in this conventional technique to provide a steady stream of air to cool it off and allows the metal structure to absorb more and more heat. High-speed processors need more cooling and sometimes more than one fan is used to provide stream of air. Sometimes for high-performance of processors, fans produce air with such force that it produces more than 60 decibels of noise. This noise increases further in case of more than one fan (Gromer). 

Benefits of Conventional Cooling Technique

Conventional air-cooling technique of computer system, although outdated, has some benefits:
·         For processor less than 2.5 GHz, it is a better technique as it is manages the heat produced by these processors efficiently
·         It is a much cheaper technique, and thus recommended for processors less than 2.5 GHz
·         It is a trusted and reliable technique
Water Cooling Technique of Computer Systems
Water-Cooling technique of computer systems is much more effective and efficient than air-cooling conventional technique. This technique produces less noise than conventional air-cooling technique but it is far more expansive than conventional technique.
To understand why water-cooling is more effective than air-cooling, let’s consider the equation, which represents the heat flow:
“Iw= G*(TD-TA ) mit G=λ* (A/l) bzw G=1/Rtherm
Where
Iw: heat flow
G: heat transfer value
λ: thermal conductivity of the heat sink material
A: surface through which the heat flows (contact surfaces between die and heat sink)
distance traveled by heat flow
TD: maximum admissible die temperature according to specs.
TA: temperature in the fan vicinity
Rtherm: thermal resistance [K/W]” (Thon)
In order to avoid heating, heat flow should be at least equal to current heat dissipation of the CPU. The equation suggests that cooling is directly proportional to the thermal conductivity of material used for cooling. Thermal conductivity of water is fifteen times greater than the thermal conductivity of air, thus water-cooling technique is far better than the conventional air-cooling technique.
Benefits of Water-Cooling Computer Systems
Although Water-Cooling technique is very expansive as compared to conventional technique, but prices will come down after some time. There are several benefits of using water-cooling computer system technique. Some of such benefits are:
·         It is far more efficient and effective cooling technique than air-cooling technique
·         It is the perfect solution for cooling in processors more than 2.5 GHz
·         It is almost noiseless as compared to conventional air-cooling technique, as it does not use fans for cooling
·         It makes the processor more efficient etc.

Pulse Tube Cooler Technique of Computer Systems

As discussed above, extra power of processor increased the heating of computer processors, which cannot be controlled by conventional air-cooling techniques. The basic purpose of thermal management of computer systems is to cool down computer hardware and ICs, so that they can work properly.
Pulse Tube Cooler (PTC) cooling technique is an innovative technique for cooling computers. The theory of cooling is similar to Refrigerators cooling.  When compressors in the computer systems compresses, it exerts the pressure and heat of the system is rejected and the cooling gas passes through the system. When the piston reaches its maximum, pressure at PTC drops due to which heat generated by the system was absorbed in PTC (Yuan and Spradley). 

Benefits of Pulse Tube Cooler Technique

This thermal management cooling system for computer systems has several benefits. Some of such benefits are:
  • It is a well established technology, which have been used in refrigerators for several years, hence it does not need extensive testing and can be used into computer systems easily
  • It is a reliable technology as it is used in space and military applications for many years
  • Design flexibility is increased due to this technology as it does not remove heat at local spot
  • Cooling can be controlled by adding or removing parallel coolers into the system
  • The low temperature and high cooling achieved from this technology will help to increase the efficiency of chips and processor
  • Interconnect delays will be reduced as it increases the conductivity of the metal etc.





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