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VI. NOMENCLATURE
A nm unit cell area [m 2 ]
c p specific heat capacity [J/(kg*K)]
g coefficient [L/min/cm 2 ]
h eff effective heat transfer coeff. [W/(m 2 *K)]
h nm unit cell heat transfer coefficient [W/(m 2 *K)]
HT heat transfer
k coefficient [-]
k v coefficient of flow [L/min]
n number of cold plates [-]
P cp cold plate pumping power [W]
P system total system pumping power [W]
total electrical processor power [W]
P el
Δp loop
Δp cp
Δp system
dp/dx
Q
rack cooling loop pressure drop [bar]
cold plate pressure drop [bar]
system pressure drop = Δploop + Δpcp [bar]
pressure gradient [Pa/m]
heat flow [W]
q
nm
unit cell heat flux [W/cm 2 ]
R fluid fluid resistance [kg/(s*m 4 )]
R conv convective thermal resistance [K*mm 2 /W]
R TIM thermal interface resistance [K*mm 2 /W]
T jmax maximal junction temperature [°C]
T fout fluid outlet temperature [K]
fluid inlet temperature [K]
T fin
ΔT fout-in
ΔT j
t nm
t Si
t TIM
V
fluid temp. difference from outlet to inlet [K]
T jmax - T jmin [K]
unit cell cavity height [mm]
silicon die thickness [mm]
bond-line thickness [mm]
cold plate volumetric flow rate [L/min]
V nm
unit cell volumetric flow rate [L/min]
V system
rack cooling loop vol. flow rate [L/min]
7-9 October 2009, Leuven, Belgium
Greek letters
ρ density of water [kg/m 3 ]
constants
h 0
p 0
reference heat transfer coefficient = 1 W/(m 2 *K)
reference pressure = 1bar
subscript/superscript
cp cold plate
el electrical
eff effective
j junction
fout-in fluid outlet minus inlet
fin fluid inlet
fout fluid outlet
loop server rack cooling loop
max maximal
m cell number in y-direction
n cell number in x-direction
ACKNOWLEDGMENT
We acknowledge Reto Wälchli, Urs Kloter, and Martin
Witzig for their technical contributions and John Magerlein
and Walter Riess for their continuous support.
REFERENCES
[1] J. Koomey, “Estimating Total Power Consumption by
Servers in the U.S. and the World”, A report by the Lawrence
Berkeley National Laboratory, February 2007, see http://
enterprise.amd.com/Downloads/svrpwrusecompletefinal.pdf.
[2] E. Colgan et al., “A Practical Implementation of Silicon
Microchannel Coolers for High Power Chips”, IEEE
Transactions on Components and Packaging Technologies, Vol.
30 No. 2., June 2007, pp. 218-225.
[3] T. Brunschwiler et al., “Towards Zero Emission Datacenters”,
IBM J. RES. & DEV., vol. 53 NO. 3 PAPER 11, 2009, see
http://www.research.ibm.com/journal/rd/533/brunschwiler.pdf
[4] H. Hamann et al., “Spatially-Resolved Imaging of
Microprocessor Power (SIMP): Hotspots in Microprocessors”,
Proc. 10th Intersociety Conf. on Thermal and Thermomechanical
Phenomena in Electronics Systems ITHERM 06, 30
May – 2 June, 2006, pp. 121-125.
©EDA Publishing/THERMINIC 2009 155
ISBN: 978-2-35500-010-2