dhe chassis and cooling

DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]

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DHE Chassis and Cooling

• DES Mechanical Workshop at FNAL

• November 2, 2005

• Vaidas Simaitis

• High Energy Physics Group

• University of Illinois at Urbana-Champaign


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6-SLOT + 4-SLOT CHASSIS


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FAN MANIFOLDS ADDED


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FANS ADDED


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COOLING MANIFOLDS ADDED


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HEAD EXCHANGERS ADDED


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MAIN MANIFOLDS ADDED WITH HEAT SINK FOR

THERMOELECTRIC COOLER


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POWER SUPPLIES ADDED


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POWER SUPPLY MANIFOLDS ADDED


10DELRIN MOUNTING INSULATORS


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MOUNTED TO INNER CYLINDER (1/4 SHOWN)


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CONNECTOR BULKHEAD


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WITH MODULE IN GREEN


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Z-AXIS VIEW WITH R=52” ID CLEARANCE CYLINDER


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WORST-CASE MODULE EXTRACTION


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WHOLE ASSEMBLY CAN BE TILTED AT EITHER END FOR

MODULE EXTRACTION


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Z-AXIS VIEW WITH HEAT SHIELDS ADDED


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BOTTOM PERSPECTIVE OF ENTIRE ASSEMBLY


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TOP PERSPECTIVE OF ENTIRE ASSEMBLY


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17.5”

22”

12”

HEAT SHIELD SIZE


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COOLING SYSTEM SIZE14”

12”

21.5”


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RADIATING SURFACE

• A = 2x(12”x 14”+ 12”x 22.5”+ 14”x 22.5”)= ~1500 in² = ~1 meter²

• L = Insulation thickness = .25” = 1/16 m

• l = thermal conductivity= ~ 0.03 W/mK for air

• If T-ambient= -20°C , T-electronics= 30°Cthen ΔT = 50°C

• Q = heat flow rate = lA ΔT / L= 0.03 x 1 x 50 x 16 = 24 Watts


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THERMOELECTRIC COOLER 1

• Q-hot = heat released hot side = Q-cold + P-in where Q-cold = heat absorbed at cold

side and P-in = electrical Power input

• T-hot = hot side temperature of thermoelectric = T-ambient + Q-hot x Θ

where Θ = thermal resistance of the hot side heat exchanger

• ΔT = required temperature differential = T-hot – T-cold


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• T-ambient is in fact the temperature of the electronics, which is assumed to be 30°C

• The heat sink temperature rise can be 1st approximated to be 10°C

• Then T-hot = 40°C

• If T-cold = -20°C then ΔT = 60°C

• Assume Q-cold = 10 W for each heat shield

• Assume Θ = 0.10 C/W (possibly?)


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• If P-in = 100 W (this is hopefully worst case)

• Q-hot = Q-cold + P-in = 10W+100W = 110W

• T-hot = T-ambient + Q-hot x Θ = 30°C + 110 W x 0.1 C/W = 41°C

which is close to the assumed value


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• Single stage TE’s are most efficient at aΔT = 40°C ± 10°C

• We probably need a 2-stage TE for handling ΔT of 60°C or more

• We have not yet explored the specificationsand pricing of these 2-stage TE’s

• Yes, this is still all theoretical!


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TOTAL HEAT LOAD• The estimated average DC power for a dual

backplane is ~350 Watts

• If power supply is 80% efficient, it must be producing another 70 W

• Add 2 TE’s at 110 W each

• Add 2 fans at 30 W each

• TOTAL = 700 W

• Or 350 W for each of 2 heat exchangers


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HEAT EXCHANGERS• T-electronics assumed = 30°C• If we assume T-liquid = 10°C• ΔT = 20°C• Performance required is 350 W / 20°C

= 17.5 W/C• Lytron M05-050 spec is 20W/C @ ½ gpm

with a liquid pressure drop of ~0.5 psi at an air flow of ~60 cfm with an air pressure drop of 0.2 inches of water

(at 100 cfm, the drop is 0.3”)


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ΔT OF COOLING WATER

• 1 gallon of water weighs 3784 grams

• ½ gallon/min = 1892 grams/min

• 1W = 14.33 calories/min

• 350W = 5016 cal/min

• ΔT = 5016/1892 cal/g -> 2.65°C

• Can we run the two heat exchangers in each crate assembly in series, with a dt = 5.3°C ?


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FANS

• Should be routine

• For example: a Comair/Rotron Patriot PT2B3 is rated at 150 cfm at 0.3” drop running at 115 VAC at 60 Hz at 31 W.

• PT2D3 should be 75 cfm at 16 W, running at 1700 rpm instead of 3400 rpm

dhe chassis and cooling

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