Laboratoire de Transfert de Chaleur et de Masse - Wikis · PDF fileLaboratoire de Transfert de Chaleur et de Masse ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE CPU Thermal Management:

Laboratoire de Transfert de Chaleur et de Masse

ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE



CPU Thermal Management: Intel IHS with Air-Cooling (Old Technology to Be Replaced or Already Being Replaced)

Existing Technology



CPU Thermal Management: Geometry for Air-Cooled System

Courtesy of IBM



CPU Thermal Assembly: Air-Cooling

Courtesy of IBM



IBM Thermal Conductive Module for Mainframes (Existing Technology to Be Replaced)

Courtesy of IBM



Possible Refrigerated Cooling System for Multiple CPU’s

Courtesy of IBM



CPU Microchannel Flow Boiling Cooling: Multiple CPU’s

Cross-section of computer chips with evaporator, Schmidt and Notohardjono [55].



CPU Microchannel Single-Phase Cooling: Colgan et al.

Figure 1 3-D rendering of assembled microchannel cooler of Colgan et al. [5].

A very low heat sink thermal resistance was obtained by Colgan et al. [5] in a single-phase silicon microchannel cooler. They used several different staggered fin configurations. The channels were 180 µm deep, either 65 µm or 75 µm wide, and the fin length was either 210 µm or 250 µm. The geometry of their assembled cooler is shown in Figure 1. Furthermore, they cooled a thermal test chip power density greater than 300 W/cm2 with a microchannel heat sink bonded to it and thus packaged in a single chip module.



Dual cold plate pumped liquid cooling system – Gernert et al (2006)

Pump

Heat Spreaders for CPU

Air-cooled compact HE

Note: System would be similar for a two-phase (boiling) heat spreader.

CPU Microchannel Single-Phase Cooling: Gernert et al.

Gernert et al [9] developed a single phase, pumped liquid cooling system (LCS) for desktop computers. The LCS has the ability to handle heat fluxes up to 250 W/cm2 and can operate below 0 oC because it uses a mixture of water and propylene glycol as the coolant.



CPU Microchannel Flow Boiling Cooling: LTCM Studies

Multi-microchannels test section used at LTCM to dissipate 350 W/cm2 with refrigerant.



Heat Conduction Simulations: Considerations for Implementation

C hip with 300 W/c m2 power density Therma l Inte rfa c e

Hea t Exc hanger

•  Specification of geometry to be simulated. •  Choice of boundary conditions for non-heated external surfaces (adiabatic b.c.’s?) •  Choice of internal channel b.c.’s for heat transfer coefficients (htc is function of q). •  2-d vs. 3-d: 1st is less expensive and faster while 3-d effects should be looked at in final or near final designs. •  Simulate just the copper (or silicon) heat spreader, the spreader plus thermal paste or the spreader, paste and silicon chip with its actual heat flux distribution (best). •  Input/interface local flow boiling heat transfer calculations and two-phase pressure drops into software package. •  Input/interface critical heat flux (critical vapor quality) calculation into software package and also diabatic flow pattern map. •  Transient effects of 3-zone model on wall temperatures, hot spots and fluctuations in heat flux should be addressed.



Example of Cooling Element Design Specifications

Power density W/cm2 300 Chip surface mm2 20×20 Chip material - Silicon Chip thickness mm 0.8 Max. chip temp. °C 85

Coolant inlet temp. °C 20

Absolute pressure bar < 5

Max. pump volume flowrate @ 1bar

l/min 4



Evaporator geometry #4

20 rectangular channels 0.5 x 3mm



3D temperature distribution 20 rectangular channels 2 x 2 x 30mm

3D simulation R-245fa, Tsat=20oC, L=20mm

Evaporator material: copper Max 65.375

Min 47.145

Documents

Laboratoire de Transfert de Chaleur et de Masse - Wikis · PDF fileLaboratoire de Transfert de Chaleur et de Masse ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE CPU Thermal Management: