Due to the performance increase of central processing units( CPU) and the higher packing density of chips, CPUs, motherboards as well as powerful graphics cards and memory generate increasing power losses. As the compactness of system components has increased rapidly, the problem of heat dissipation to processors in personalcomputers(PCs), especially in racks and thus in data centers, is becoming increasingly important.
In general, cooling can be active or passive, and the various cooling methods can be classified according to their efficiency. Thus, passive cooling is based on convection and conduction, while active works with fans and air-water cooling.
Since passive cooling on processors, electronic modules and in racks by means of heat sinks, heat distribution plates, cooling cassettes and air circulation is no longer sufficient for heat dissipation above a certain power loss, active cooling must be used in these cases. Heat sinks with heat conducting paste, heat conducting pads, heat distribution plates, heat pipes, fans or Peltier elements provide heat dissipation.
Cooling of racks
In rack cabinets, constructional measures ensure rapid heat dissipation. This can take place via the chimney effect or with fans, which ensure temperature equalization via appropriate air supply and removal. There is also the possibility of dissipating heat with heat pipes without fan noise. The situation is different in cabinets, where heat dissipation can no longer be achieved by air cooling alone in a rack fully equipped with servers. Air cooling reaches its limits in a 2 m rack at a power loss of 6 kW. For these cases, air-water cooling can be used instead of air cooling. In these systems, the distribution of the cooling liquid takes place in the frame profile of the rack. For data centers, cooling becomes a real challenge due to the determination of the actual cooling demand and the implementation of a cooling solution that meets the demand and is expandable. In this environment, combinations of different cooling technologies are used.
As a guideline for air cooling and thermal management, there is IEC Recommendation 62194, which specifies measures for heat removal from cabinets.
With better energy utilization and under the aspect ofGreen IT, there is an approach with Energy Harvesting with which the waste heat of the computer systems can also be converted into electrical energy for cooling by means of thermoelectrics.