Editing Computer cooling (section)

===Chip-integrated===
Conventional cooling techniques all attach their "cooling" component to the outside of the computer chip package. This "attaching" technique will always exhibit some thermal resistance, reducing its effectiveness. The heat can be more efficiently and quickly removed by directly cooling the local hot spots of the chip, within the package. At these locations, power dissipation of over 300&nbsp;W/cm<sup>2</sup> (typical CPU is less than 100&nbsp;W/cm<sup>2</sup>) can occur, although future systems are expected to exceed 1000&nbsp;W/cm<sup>2</sup>.<ref>{{cite journal |first=I. |last=Mudawar |title=Assessment of High-Heat-Flux Thermal Management Schemes |journal=IEEE Transactions on Components and Packaging Technologies |volume=24 |issue=2 |pages=122–141 |year=2001 |doi=10.1109/6144.926375 |url=https://engineering.purdue.edu/BTPFL/BTPFL%20Publications/83.pdf }}{{Dead link|date=December 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> This form of local cooling is essential to developing high power density chips. This ideology has led to the investigation of integrating cooling elements into the computer chip. Currently there are two techniques: micro-channel heatsinks, and jet impingement cooling.

In micro-channel heatsinks, channels are fabricated into the silicon chip (CPU), and coolant is pumped through them. The channels are designed with very large surface area which results in large heat transfers. Heat dissipation of 3000&nbsp;W/cm<sup>2</sup> has been reported with this technique.<ref>{{cite journal |first1=M. B. |last1=Bowers |first2=I. |last2=Mudawar |title=High Flux Boiling inLow Flow Rate, Low Pressure Drop Mini-Channel and Micro-Channel Heat Sinks |journal=[[International Journal of Heat and Mass Transfer]] |volume=37 |issue=2 |pages=321–332 |year=1994 |doi=10.1016/0017-9310(94)90103-1 |bibcode=1994IJHMT..37..321B }}</ref> The heat dissipation can be further increased if two-phase flow cooling is applied. Unfortunately, the system requires large pressure drops, due to the small channels, and the [[heat flux]] is lower with dielectric coolants used in electronic cooling.

Another local chip cooling technique is jet impingement cooling. In this technique, a coolant is flowed through a small orifice to form a jet. The jet is directed toward the surface of the CPU chip, and can effectively remove large heat fluxes. Heat dissipation of over 1000&nbsp;W/cm<sup>2</sup> has been reported.<ref>{{cite journal |first1=M. K. |last1=Sung |first2=I. |last2=Mudawar |title=Single-phase and two-phase hybrid cooling schemes for high-heat-flux thermal management of defense electronics |journal=Journal of Electronic Packaging |year=2009 |volume=131 |issue=2 |pages=021013 |doi=10.1115/1.3111253 }}</ref> The system can be operated at lower pressure in comparison to the micro-channel method. The heat transfer can be further increased using two-phase flow cooling and by integrating return flow channels (hybrid between micro-channel heatsinks and jet impingement cooling).