Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Heatsink : black or silver ?

Status
Not open for further replies.

IanP

Advanced Member level 5
Joined
Oct 5, 2004
Messages
7,942
Helped
2,309
Reputation
4,620
Reaction score
531
Trophy points
1,393
Location
West Coast
Activity points
66,435
natural vs black heat sink

Do you think that black anodised heatsink is much more efficient than just plain silver?

Here is a quote form somewhere:
There was a debate many years ago about the colour of heatsink used in power amplifier. At that time, somebody said "silver" is more efficient than traditional black. There was the trend that people used silver or gold heatsinks, maybe they are more attractive. However, the "Black" is proven to be the winner eventually.
So Black is good for heatsink (to absorb & radiate heat faster).
And Silver is good for your car (to reflect heat energy better).
 

froggy

Member level 5
Joined
Jul 6, 2001
Messages
84
Helped
3
Reputation
6
Reaction score
1
Trophy points
1,288
Activity points
699
heatsink blackening

Hi, the thermal resistance increase with about 15% for a silver heatsink, compared to a black anodized one. If the heatsink is mounted horistontally instead of vertically the K factor decrease by another 15-20%.

/Froggy
 

    IanP

    Points: 2
    Helpful Answer Positive Rating

echo47

Advanced Member level 5
Joined
Apr 7, 2002
Messages
3,942
Helped
637
Reputation
1,272
Reaction score
88
Trophy points
1,328
Location
USA
Activity points
33,178
heatsink gold or black

If the equipment has strong forced-air cooling, then heatsink surface finish isn't very important.

If the equipment has low airflow, then radiation cooling becomes important, and black anodized aluminum radiates enormously better than bare unfinished aluminum.

Many years ago I had a 100 watt audio amp with bright shiny extruded aluminum finned heatsinks. No fan, just convection cooling. The heatsinks were always too hot to touch, probably over 80C. I replaced them with identical black anodized heatsinks, and their temperature dropped to about 45C.
 

    IanP

    Points: 2
    Helpful Answer Positive Rating

VVV

Advanced Member level 5
Joined
Nov 26, 2004
Messages
1,582
Helped
384
Reputation
768
Reaction score
87
Trophy points
1,328
Activity points
19,971
heat sink black

Black heatsink if convection-cooled. The color becomes almost irrelevant if forced-air cooling is used.
 

    IanP

    Points: 2
    Helpful Answer Positive Rating

rkodaira

Full Member level 6
Joined
Jun 8, 2004
Messages
332
Helped
68
Reputation
136
Reaction score
12
Trophy points
1,298
Location
Sao Paulo - Brasil
Activity points
4,092
emissivity of black anodized aluminum

From a Lecture Note written by William P. Robbins - University of Minessota

" Aluminum heatsinks of various shapes and sizes are widely available for cooling components.

- Often anodized with balck oxide coating to reduce thermal resistence up to 25%
....
....
Stefan-Boltzman law describes radiative heat transfer:

Prad = 5.7 * 10^-8 * E * A * [(Ts)^4 - (Ta)^4] in watts
where:

E = emissivity
black anodized aluminum E = 0.9
polished aluminum E = 0.05

A = surface area (m2) through which heat radiation emerges

Ts = surface temperature (K) of component
Ta = ambient temperature (K)"
 
  • Like
Reactions: mukeshp11

    IanP

    Points: 2
    Helpful Answer Positive Rating

    mukeshp11

    Points: 2
    Helpful Answer Positive Rating

IanP

Advanced Member level 5
Joined
Oct 5, 2004
Messages
7,942
Helped
2,309
Reputation
4,620
Reaction score
531
Trophy points
1,393
Location
West Coast
Activity points
66,435
silver or black heatsink

Thank you all for your replies ..
However, here is the puzzle:
I am testing two radio modems. They are identical (same supply voltage, very similar currents drawn from power supplies), the only difference is that one has black anodized housing (used as heatsink) the other natural anodized aluminim ..
And guess what: temperatures of their housings are almost the same ..
 

echo47

Advanced Member level 5
Joined
Apr 7, 2002
Messages
3,942
Helped
637
Reputation
1,272
Reaction score
88
Trophy points
1,328
Location
USA
Activity points
33,178
"Natural anodized" is an oxymoron. Perhaps you mean bare unfinished aluminum?

Black anodized and clear anodized are both good radiators. Unfinished aluminum, especially if polished, is a poor radiator.

Perhaps your modems have some airflow (good natural convection, or a nearby fan), so their surface finish isn't very important. Or perhaps a large object near the modem reflects the radiated heat back to the modem.
 

aji

Junior Member level 2
Joined
Mar 4, 2005
Messages
24
Helped
6
Reputation
12
Reaction score
0
Trophy points
1,281
Location
Kerala,India
Activity points
1,510
Hi,
Use finished silver or reflecting shield for reflecting heat away from a heat source
and use unfinished large surface area black heatsink for radiating maxmum, heat from a heat source to surroundings
Ajith
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top