surplus copper, aluminum, Composite heatsinks... ...?

[13elves]

Besides the up n coming mechatronix pin fin giant cylindrical heatsinks, do any of these designs look adequate to passively cool an 100w Luna100? Am really liking these black ones. They are easily 90% lighter than an equal sized aluminum heatsink. I can get some aluminum that are approx 6"w × 5"d × 6"h and shaped kind of like ll¥ll and fairly heavy. or some that're roughly 6x6x3 but i thought copper was better option. whatyya say anyone? please feel free to be critical if necessary.... thanks

 

[sanjuan]

"do any of these designs look adequate to passively cool an 100w Luna100?"
No but the Zalmans might come close.

What are the black ones made of, being lighter than aluminum?
Copper is thermally better than aluminum but it is heavy and expensive.

 

[freemanjack]

Meh, unlikely, sorry, none of those look remotely large enough to cool a 50w cob let alone 100w one.

 

[GreenMotion]

maybe for some mono's?

 

[Ganjineer]

The Zalman's will come close. I've actually used that exact cooler to cool some old Pentium 4's running at ~100W. However, acceptable temperatures were ~70C for the processor, you would want to avoid going that high full-time on LED's. I would say most of those server heat sinks that you have there could acceptably cool an LED running in the 50W range. Please note that all of those server heat sinks are designed for active cooling with a fan!

If you absolutely must run the COB at 100W you could try the following...
Mount two of the coolers to a flat aluminum or copper bar or plate 1/8" to 1/4" thick. Then, mount the led to that bar. You won't get twice the dissipation that you would using just one heat sink, but it'll be ~75% more (due to the increase in thermal resistance caused by the addition of the plate and the extra thermal interface junction).

 

[freemanjack]

The Zalman's will come close. I've actually used that exact cooler to cool some old Pentium 4's running at ~100W. However, acceptable temperatures were ~70C for the processor, you would want to avoid going that high full-time on LED's. I would say most of those server heat sinks that you have there could acceptably cool an LED running in the 50W range. Please note that all of those server heat sinks are designed for active cooling with a fan!

If you absolutely must run the COB at 100W you could try the following...
Mount two of the coolers to a flat aluminum or copper bar or plate 1/8" to 1/4" thick. Then, mount the led to that bar. You won't get twice the dissipation that you would using just one heat sink, but it'll be ~75% more (due to the increase in thermal resistance caused by the addition of the plate and the extra thermal interface junction).

Sorry to correct you, but you cannot make any direct comparison between the rated cpu wattage and its equivalent led it is comparing oranges with apples. You would be far better served fitting the biggest, heaviest one with the largest CF/M(cubic foot per minute) rated fan you can fit on it, active cooling is more dependant on amount of air moved that the effective heat capacity of the heatsink so if the cooling is inadequate, fit a larger fan, simple.
edit, take a look at these heatsink/fan/cob assemblies, these adequately cool 40w cobs but would struggle with anything above 50w;

 

[freemanjack]

From wikki;
**Most of the electricity in an LED becomes heat rather than light (about 70% heat and 30% light)
https://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs
by comparison a 90w i7 produces a maximum of 55 heat watts;
https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_figures#Intel_Core_i7_2
so as a rough back of the rizla packet calculation; leds 70% heat watts, cpu's 50% heat watts so you need half as big heatsink again for a 100w led as a 100w cpu or possibly double the cubic foot fan capacity?

 

[alesh]

From wikki;
**Most of the electricity in an LED becomes heat rather than light (about 70% heat and 30% light)
https://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs
by comparison a 90w i7 produces a maximum of 55 heat watts;
https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_figures#Intel_Core_i7_2
so as a rough back of the rizla packet calculation; leds 70% heat watts, cpu's 50% heat watts so you need half as big heatsink again for a 100w led as a 100w cpu or possibly double the cubic foot fan capacity?

Most of the latest gen COBs will run at higher efficiency than 30%. On the other hand, a CPU cooler rated at 100W is probably NOT designed to run a CPU @100W 24/7.

 

[Ganjineer]

Sorry to correct you, but you cannot make any direct comparison between the rated cpu wattage and its equivalent led it is comparing oranges with apples. You would be far better served fitting the biggest, heaviest one with the largest CF/M(cubic foot per minute) rated fan you can fit on it, active cooling is more dependant on amount of air moved that the effective heat capacity of the heatsink so if the cooling is inadequate, fit a larger fan, simple.
edit, take a look at these heatsink/fan/cob assemblies, these adequately cool 40w cobs but would struggle with anything above 50w;

https://en.wikipedia.org/wiki/Thermal_design_power

You can make comparisons between a heat sink's TDP rating and CPU wattage, you merely have to account for the variables. For a CPU, wattage draw by the processor is equal to the heat dissipation of the processor (for engineering purposes). If a heat sink is rated for 100W TDP then it is designed to cool a processor drawing 100W full time to acceptable operating temperature (what that may be depends on the maximum allowable junction temperature as specified by the processor manufacturer typically 60-70C). For an LED drawing 100W around 50W (depending on efficiency) will be converted to heat in the case and the other 50W converted to radiant energy (which will be later converted to heat after being absorbed by surfaces in the grow room). So, you will need to remove 50W of heat from the case of the COB. Therefore, if a CPU heat sink is rated for 100W TDP cooling the processor to 60-70C then you can very safely assume that it could cool 50W of heat from the COB. However, it is good practice to build in a factor of safety to your design. A rule of thumb that I have followed is to decide what wattage you want to run the COB, multiply that by 2, and then find a CPU heat sink rated for that TDP. So... 100W x2= 200W so you could look for a CPU heat sink with a TDP rating of 200W. It's not exact, but it works for our purposes.

Please note that in my post I specified that these heat sinks are designed for active cooling with a fan. Therefore, the TDP that they are rated for is dependent on the flow rate supplied by the fan. I agree with you that increases in flow rate of the fan will most significantly impact heat dissipation. In practice for CPU coolers, active cooling at full fan speed increases heat dissipation by 3-4x over passively cooled heat sinks. Perhaps my initial post was not clear in that regard.

To the OP: those heat sinks will only come close to dissipating the heat from your COB if they are actively cooled with their fans. Don't expect to cool a COB running at more than 20W passively with those heat sinks. I know that this is outside the scope of your original question, but you'll likely need large (>140mm) pin fin heat sinks to passively cool a COB @ 100W.

 

[nevergoodenuf]

You are forgetting that COB's are designed to run @ 85*c. Tj max is 140 (citizen CLU), so much higher limits on COBs, but you do lose efficacy if running that hard.

 

[13elves]

Off to salvage the day then!! Will upload some pics of the bigger ones when return. In case anyone was considering getting any of the ^^olex (sources allowed?) clu058/clu550 led holders,, don't!!! they suck!!! heres the copper heatsinks was using but am going to trade them now!! I like these sideways type blower fans. The black ones i think are composite but don't know. Just a quick rough draft on the last pic. gotta run....

 

[RyGon]

Hey, I got a box of junked heatsinks today too. Not bad for $5. I'm thinking the pair on the back right should work for some CLU048-1212s, no?

 

[13elves]

that rocks we know same little hidden back alley warehouse! if those were the same ones in those crates, dug all the biggest could find out a few days ago. how come you didn't go for those zalman circular ones? that's awesome!! know the same dude! been workin for over a year with this guy and he still won't let go treasure hunting thru his audio equipment! have you asked him?

 

[13elves]

 

[13elves]

grabbed these hoods for 5 bucks too! not too familiar with cost for a sub- panel but got this two hundred A power box and digital timer for a bill fifty , is that reasonable or was shammed?

 

[RyGon]

View attachment 3823074 View attachment 3823073 View attachment 3823075 View attachment 3823076

LOL, the circular ones I saw didn't have a big enough pad to mount to.

 

[OldMedUser]

I'm a huge DIY fan but you're beating a dead horse here.

 

[13elves]

its all good.. i should've been clear that my reluctant request has been answered already, was just following up.....

rygon: i dug threw both of those crates full and only found these 2!! all the others were half the size though. there were still maybe ten zalman though.. and a bunch of heavier copper, but small size still.

 

[alesh]

You can make comparisons between a heat sink's TDP rating and CPU wattage, you merely have to account for the variables. For a CPU, wattage draw by the processor is equal to the heat dissipation of the processor (for engineering purposes). If a heat sink is rated for 100W TDP then it is designed to cool a processor drawing 100W full time to acceptable operating temperature (what that may be depends on the maximum allowable junction temperature as specified by the processor manufacturer typically 60-70C).

I believe that this is true only for server heat sinks. Home PC CPU cooler rated @100W will have hard time cooling CPU running @100W for a longer period of time.

 

[RyGon]

I'm a huge DIY fan but you're beating a dead horse here.

Dead for passive, but some of these should be fine for active cooling, right? Even for passive couldn't you line up 4 or 5 of those aluminum passive heatsinks on a conductive plate to cool a COB?