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
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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MAIN MANIFOLDS ADDED WITH HEAT SINK FOR
THERMOELECTRIC COOLER
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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MOUNTED TO INNER CYLINDER (1/4 SHOWN)
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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Z-AXIS VIEW WITH R=52” ID CLEARANCE CYLINDER
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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WHOLE ASSEMBLY CAN BE TILTED AT EITHER END FOR
MODULE EXTRACTION
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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Z-AXIS VIEW WITH HEAT SHIELDS ADDED
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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BOTTOM PERSPECTIVE OF ENTIRE ASSEMBLY
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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TOP PERSPECTIVE OF ENTIRE ASSEMBLY
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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COOLING SYSTEM SIZE14”
12”
21.5”
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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THERMOELECTRIC COOLER 2
• 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?)
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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THERMOELECTRIC COOLER 3
• 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
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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THERMOELECTRIC COOLER 4
• 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!
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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”)
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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 ?
DES DHE Electronics Chassis --- Vaidas Simaitis [email protected]
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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