03-22-2005, with pieces going back to 2003<br />
<br />

Heatsink Information and more.  <br />
<br />
Passive heatsinks need to be designed to radiate.<br />
<br />
A bunch of parallel fins are just going to radiate into each other, as well as pins.  <br />
<br />
By and far the most effective radiative heatsink I saw had a surface that looked more like a tenderizer, with elongated parts, so the heat could radiate into free space.  I don't remember the numbers, but black anodize/oxidize made quite a difference as compared to a raw machined part, and polishing is one of the worst things you can do.  The more open the heatsink, the more of a difference I have seen between raw and black.<br />
<br />

Then there are convective heatsinks that take advantage of the chimney effect, where the rising air as it gets warm, pulls in cool air in from the bottom.  Never saw this improve much when black anodized/oxidized.<br />
<br />
Then there is forced air heatsink design, never saw black make much difference here either.<br />
<br />
Also, black paints are not by any means created equal, if you are thinking about using that on a heatsink.  Regular Krylon flat black on our black body radiator surfaces acts alot like a thermal blanket.  But Krylon high heat barbaque flat black is nearly as good at radiating as a variety of high end black body coatings (such as 3M Black Velvet at dang near 100% emissivity).<br />
<br />
I'll agree that Aluminum will soak up more heat per weight, <br />
but copper still beats it for size/volume, so per volume, copper will soak up more heat than aluminum, and copper will also have 2-3 times less thermal resistance than alumimum. <br />
<br />
Thermal conductivity (W/m*K): <br />
<br />
(higher is better)<br />
<br />

Titanium(Ti6Al4V) 6.7 (*extremely* poor thermal conductor)<br />
Brass (70Cu-30Zn) 115 <br />
Magnesium alloy ZK60A 117 <br />
Aluminum (7075-T6)130 <br />
Magnesium ....... 170 <br />
Aluminum (6061).. 171 <br />
Aluminum (6063).. 193 <br />
Aluminum Pure ... 247 (rarely ever used in pure form) <br />
Copper .......... 398 <br />
Diamond ......... 2500 <br />
<br />
<br />
<i>Side note on metals:<br />
<br />
In order of electrical conductivity (relative to copper)<br />
<br />
Material IACS % Conductivity<br />
Silver 105%<br />
Copper 100%<br />
Gold 70%<br />
Aluminum 61%<br />
Nickel 22 %<br />
Zinc 27%<br />
Brass 28%<br />
Iron 17%<br />
Tin 15%<br /> 
Phosphor Bronze 15%<br />
Lead 7%<br />
Nickel Alum. Bronze 7%<br />
Steel 3 to 15%<br />
Titanium 1% (extremely poor electrical conductor)<br />
</i>
<br />
<br />

White thermal compound (AOS52022) 0.7 <br />
<br />
Specific Heat, J/gm K: <br />
Aluminum 0.900 <br />
Copper 0.386 <br />
<br />
A ratio of 2.33 (Al):1 (Cu) (by mass) <br />
<br />
But the density (mass per volume) is greater for copper: <br />
<br />
Metal or alloy kg/cu.m <br />

aluminium - melted 2560 - 2640 <br />
aluminium bronze (3-10% Al) 7700 - 8700 <br />
aluminium foil 2700 -2750 <br />
beryllium copper 8100 - 8250 <br />
copper 8930 <br />
<br />
3.31 (Cu) : 1 (Al) <br />
<br />
Pure Aluminum's electrical conductivity is only 62% that of copper, but: <br />
Copper 100% <br />

Aluminum 6063 57 - 65% <br />
Aluminum 6061 47 - 56% <br />
Aluminum 7075 44 - 47.5% <br />
Aluminum 7075 T6 series 30 - 35% <br />
In almost all cases, aluminum with a T after it will have lower conductivity than the base alloy. <br />
<br />
So, for volume: <br />
- Copper will soak up 142% more heat than Aluminum <br />
- it will have half the thermal resistance at <br />

the same time. <br />
- average 40% better electrical conductivity per size (or 40% less electrical resistance.) <br />
<br />
And if you like the feel of heavy things, the copper will be 3 times as heavy as aluminum, for the same machined object.<br />
<br />
<br />
<br />
 <br />
<br />
<a href="http://www.infrared-thermography.com/material.htm" target="_blank">http://www.infrared-thermography.com/material.htm</a> <br />
<br />

Aluminum: highly polished plate, 98.3% pure emissivity 0.039 - 0.057 <br />
Aluminum: polished plate, emissivity 0.04 <br />
Aluminum: polished sheet, emissivity 0.04 <br />
Aluminum: polished and degreased, emissivity 0.027 <br />
Aluminum: rough plate, emissivity 0.055 <br />
Aluminum: sandblasted, emissivity 0.210 <br />
Aluminum: oxidized at 600C, emissivity 0.11-0.19 <br />
<br />
The relatively low emissivity coefficient makes aluminum a suitable product for limiting the radiated heat from a body. <br />

Additional information at various temperatures is found here. <br />
<a href="http://www.engineeringtoolbox.com/26_433.html" target="_blank">http://www.engineeringtoolbox.com/26_433.html</a><br />
</div>
<br />
<br />
Here is another useful link for emissivities:
<a href="http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html" target="_blank">http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html</a><br />	
<br />
<br />

<div>Another little discussed heatsink technique...<br />
<br />
It is interesting to note that many heatpipes have thermal resistances 2,000 times lower than copper and 4,000 times lower than aluminum. They are a great method of rapidly spreading concentrated heat sources from point A to point B, and also to spread the heat around. This is why they are very common in recent laptops. <br />

<br />
<a href="http://www.avc.com.tw/products/oem/index.html#" target="_blank">http://www.avc.com.tw/products/oem/index.html#</a><br />
(click on heatpipe diameter you are interested in) <br />
<br />
<a href="http://www.acktechnology.com/Heat%20Pipe.htm" target="_blank">http://www.acktechnology.com/Heat%20Pipe.htm</a> <br />
<br />
<br />
Some interesting articles: <br />
<a href="http://www.cheresources.com/htpipes.shtml" target="_blank">http://www.cheresources.com/htpipes.shtml</a> <br />
<br />
<a href="http://www.transterm.ro/overview.htm" target="_blank">Heatpipe Basics</a> <br />
<br />

What do they actually look like? Here is a photo of some I purchased a while back. <br />
<a href="http://www.molalla.net/~leeper/heatpipe.jpg" target="_blank">http://www.molalla.net/~leeper/heatpipe.jpg</a> <br />
<br />
It is interesting to note that many heatpipes have thermal resistances 2,000 times lower than copper and 4,000 times lower than aluminum. They are a great method of rapidly spreading concentrated heat sources from point A to point B, and also to spread the heat around. This is why they are very common in recent laptops.<br />
<br />
<br />
<a href="http://www.stanford.edu/group/microheat/hex.html" target="_blank">Other Technologies-Electrokinetic Pumps</a> <br />
<br />
<br />
Going back to the old topic, I'll jump back up on the soap box...<br />
<br />
There is also the ability of the heatsink to transport the heat, there is a thermal resistance in the metal itself. It is also the reason why the tips of the fins of a heatsink are typically much cooler than where the heat source is mounted. A good example is copper vs. aluminum. Copper has half the thermal resistance of aluminum, and makes a wonderful heat spreader.<br />
<br />
An additional factor is the surface finish, especially with heatsinks that are designed to work more as heat radiators. Freshly machined aluminum is a very poor radiator. But if you Hard Anodize III it, the amount it radiates can go up by over a factor of 10, reaching in the 77% range. Copper, oxidized black hits an emissivity in the 88% range. For example, if really good machining is done, such that it has a mirror finish, aluminum can have an emissivity of only 4%. Part way in between is a alodyne finish (chromate conversion), which typically sits in the 40%-60% range. Black paint is a blessing and curse, depending on it's formulation. Many can act as a thermal blanket over the aluminum. Then there are others, such as black body paint, and certain barbaque black (Krylon is a good one), that can be in the 95%-99% emissivity range, with some special paints, like 3M Black Velvet 9560 can hit 100%. Believe it or not, there are even white paints which are heavily loaded with TiO2 that are in the 94% emissivity range, but also reflect nearby heat sources at a 90% range. Keep in mind that these numbers move around alot, depending on the temperature of the heatsink.<br />

<br />
A start as a resource is found here:<br />
<a href="http://www.infrared-thermography.com/material.htm" target="_blank">http://www.infrared-thermography.com/material.htm</a><br />
<br />
Google makes a fine teacher for the curious.<br />
<br />
<br />
<br />
Oh, and we should touch on materials to connect the various pieces together....<br />
<i> Lower numbers are bad for thermal conductivity</i><br />
<br />
Air: <br />
Thermal conductivity 0.025-0.031 W/mK <br />

<br />
Fiberglass: <br />
Thermal conductivity 0.04 W/mK <br />
<br />
Superglue Loctite 382: <br />
Coefficient of thermal conductivity, ASTM C177, 0.11 W.m-1K-1 <br />
Glass transition temperature, ASTM E228, ºC 130 <br />
(*most epoxies transistion around 50-65 ºC) <br />
(some high temperature epoxies transition 90 ºC and above-specialized) <br />
(glass transition temperature is when material gets soft and <br />

bonds get weak) <br />
<br />
<a href="http://www.loctite.se/tds/382.pdf" target="_blank">http://www.loctite.se/tds/382.pdf</a> <br />
<br />
<br />
Picked this as a typical epoxy Loctite Hysol 3450: <br />
Coefficient of thermal conductivity, ASTM C177, 0.28 W.m-1K-1 <br />
Bond strength at temperature is shown on datasheet chart. <br />
<a href="http://www.loctite.at/tds/3450.PDF" target="_blank">http://www.loctite.at/tds/3450.PDF</a> <br />

<br />
Nylon (Polymide): <br />
Thermal conductivity 0.24 W/mK <br />
<br />
Pure Water: <br />
Thermal conductivity 0.58 W/mK <br />
<br />
Wakefield 120 Thermal Grease: <br />
Thermal conductivity 0.735 W/mK <br />
<a href="http://power.ece.uiuc.edu/Balog/images/How%20to%20keep%20your%20cool%20when%20working%20with%20power%20electronics.pdf" target="_blank">http://power.ece.uiuc.edu/Balog/ima...electronics.pdf</a> <br />

<br />
Fused Silicon Dioxide: <br />
Thermal conductivity 1.4 W/mK <br />
<br />


Dow Corning SE4447 CV Thermal RTV: <br />
Thermal conductivity 2.5 W/mK <br />
<a href="http://www.dowcorning.com/DataFiles/090007b58021adab.pdf" target="_blank">http://www.dowcorning.com/DataFiles...7b58021adab.pdf</a> <br />
<br />

<br />
<b>Titanium Alloy Ti6Al4V:</b><br />
Thermal conductivity 6.7 W/mK <br />
<a href="http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641" target="_blank">http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MTP641</a> <br />
<br />

Artic Silver Thermal Epoxy: <br />
Thermal conductivity. Greater than 7.5 W/mK <br />

<a href="http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm" target="_blank">http://www.arcticsilver.com/arctic_...al_adhesive.htm</a> <br />
<br />
Stainless Steel: <br />
Thermal conductivity 15-25 W/mK <br />
<br />
Loctite Thermal Adhesive QMI 5030: <br />
Thermal conductivity, 25 W/mK <br />
<a href="http://www.loctite.com/int_henkel/loctite/binarydata/pdf/lt3758a_ThermMgmt.pdf" target="_blank">http://www.loctite.com/int_henkel/l...a_ThermMgmt.pdf</a> <br />
<a href="http://www.loctite.at/tds/QMI5030.pdf" target="_blank">http://www.loctite.at/tds/QMI5030.pdf</a> <br />

<br />
Alumina (Aluminum Oxide): <br />
Thermal conductivity 30 W/mK <br />
<br />
Lead: <br />
Thermal conductivity 34.7 W/mK <br />
<br />
Carbon Steel: <br />
Thermal conductivity 43-64 W/mK <br />
<br />
Magnesium: <br />
Thermal conductivity 156 W/mK <br />
<br />
<b>Aluminum: </b><br />
Thermal conductivity 190 W/mK <br />
<br />
Aluminum Nitride: <br />
Thermal conductivity 260 W/mk <br />
<br />
Boron Nitride: <br />
Thermal conductivity 250-300 W/mk <br />
<br />
<b>Copper: </b><br />
Thermal conductivity 386 W/mK <br />

<br />
Silver: <br />
Thermal conductivity 406 W/mK <br />
<br />
Diamond: <br />
Thermal conductivity 500- 1000+ W/mK<br />
<br />
<br />
Higher W/mK means it transfers the heat better.<br />
<br />
<br />
<br />
<br />
<div>As far as the folks that keep pulling stuff out of thin air and keep repeating old wives tales, here is an actual study of copper vs. aluminum heatsinks:<br />
<br />
<i>"The thermal performances of the four heatsink combinations under forced convective heat-transfer mode were measured for the concentrated heat source. Measurements are depicted graphically in Fig. 6, with results summarized in Table 2. As expected, the all-copper (Cu base-Cu fin) heatsink had the lowest thermal resistance with a 22% average reduction in thermal resistance as compared to the all-aluminum sink."</i><br />
<br />
<a href="http://powerelectronics.com/mag/power_characterizing_mixedmetal_heatsinks/" target="_blank">http://powerelectronics.com/mag/pow...etal_heatsinks/</a><br />

<br />
<br />
<br />
Now the situation changes a bit with forced convection (forced air):<br />
<br />
<i>"For heat source covering 5% of the base plate area, the all-copper heatsink had the lowest thermal resistance, with up to a 28.7% reduction in source thermal resistance as compared with the all-aluminum sink."</i><br />
<br />
<i>"Up to 15% reduction in thermal resistance was achieved by using a copper base-aluminum fin or aluminum base/copper fin sink."</i><br />
<a href="http://powerelectronics.com/mag/power_tests_compare_forced/" target="_blank">http://powerelectronics.com/mag/pow...compare_forced/</a><br />
<br />
So basically here too, copper fins and copper base pays off bigtime, over all aluminum or aluminum/copper hybrid.</div>
<br />
<br />
<br />
<br />
<div>This is a heatpipe I made at home, it has nothing more than some water inside, which is in a vacuum, and it works surprisingly well.<br />
<br />
<img src="http://www.molalla.net/~leeper/heatpip2.jpg" border="0" alt="" /><br />
<br />
<br />
Here is a set I purchased for only a few dollars, that have the internal wick structure, and work even better.  They even work "upsidedown" and when you bend them in various shapes.<br />
<br />
<img src="http://www.molalla.net/~leeper/heatpipe.jpg" border="0" alt="" /></div>
<br />
<br />

<div>The heatpipes I have are made by Furukawa AVC Electronics (Suzhou), and are 80 times better at transferring heat than copper, and <b>160 times better than aluminum</b>.  The company also produces micro heatpipes with a diameter of 2mm.<br />

<br />
One of the interesting things about heatpipes, is that they are thin walled, and are extemely light, much lighter than the equivalent diameter of aluminum.<br />
<br />
They can be found here, click on the heatpipe pictures at the bottom:<br />
<a href="http://www.avc.com.tw/products/NB-Thermal.htm#" target="_blank">http://www.avc.com.tw/products/NB-Thermal.htm#</a><br />
<br />
You need to locate the distributor in your area to get them.<br />
<br />
However, here is the office in North America to contact:<br />
<br />
AVC North America<br />

<a href="mailto:sales@avcamerica.com">sales@avcamerica.com</a><br />
TEL : +1-310-783-0885<br />
FAX : +1-310-212-3284 <br />
<br />
One of the contacts there, if it is still good:<br />
<br />
<a href="mailto:heather@avcamerica.com">heather@avcamerica.com</a><br />
 <br />
Heather Smith <br />
Regional Sales Manager<br />

AVC America, Inc. <br />
528 Amapola Avenue <br />
Torrance, Ca. 90501 <br />
<a href="http://www.avcamerica.com" target="_blank">www.avcamerica.com</a><br />
PH: 310-783-5472 <br />
CL: 310-999-8534 <br />
FX: 310-783-0875<br />
<br />
<br />
A list of distributors in your area:<br />

<a href="http://www.avcamerica.com/Dist/index.htm" target="_blank">http://www.avcamerica.com/Dist/index.htm</a><br />
<br />
<br />
Sales reps in your area (many of the reps are not even aware they can obtain heatpipes as they are used to only selling AVC heatsinks, but if they inquire, they can easily obtain them):<br />
<br />
Mfg. Rep./Contact Name <br />
 Address <br />
 Phone / Fax <br />
 Territory <br />

 <br />
Clark Sales, LLC <br />
27600 Farmington Road, Suite 209<br />
Farmington Hills, MI 48334 <br />
248-553-0610 <br />
IN, KY,OH, MI <br />
(Jack Adams, Dick Harvey, Heather Devlin) <br />
248-553-7330 F <br />
 <br />

Exis Manufacturers Rep. <br />
631 Riveroaks Parkway<br />
San Jose, CA 95134 <br />
408-944-4600 <br />
N. Ca <br />
(Ralph Voner Har, Nancy Carnathan-Cribbs) <br />
408-321-3200 F <br />
 <br />
Martan Inc.                       <br />

1100 Woodfield Road, Suite 145<br />
Schaumburg, IL 60173 <br />
847-330-3200 <br />
IL,WI, IA,NE, KS, MO <br />
(Bob Tanka, Colette Schaefer, Roman Budek) <br />
847-330-0024 F <br />
(Todd Schwerm, Melanie Abel) <br />
6936 Mount Pleasant Dr.,              <br />
West Bend, WI  53090 <br />

262-241-4955 <br />
262-241-8365 F <br />
(Scott Misbauch) <br />
2846 Dardenne Links Dr.<br />
O'Fallon, MO 63366 <br />
636-294-2310 <br />
636-294-2312 F <br />
 <br />
Mission Technology <br />

16466 Bernardo Center Dr. Ste 188<br />
San Diego, Ca 92128 <br />
858-674-6191 <br />
S. Ca <br />
(Ed Wahlroos, Anne Axelson, Anthony Mitchell) <br />
858-674-6196 F <br />
(Mike Fitch, Shye Nakabayashi) <br />
24422 Avenida De La Carlota<br />
Ste. 265, Laguna Hills, Ca 92653 <br />

949-951-3696 <br />
949-951-3874 F <br />
(Mike Miskinnis) <br />
505 Firecrest Court<br />
Newbury Park, Ca 91320 <br />
805-381-1801 <br />
805-371-9524 F <br />
 <br />
Pipe Thompson <br />

2155 Dunwin Dr.  Unit #7<br />
Mississauga, ON L5L 4M1  <br />
905-607-1850 <br />
Canada <br />
(James Pipe, Dave Cochran, Lorenzo Crupi) <br />
905-607-1858 F <br />
(Sherman Sum) <br />
22020 Cliff Ave<br />
Maple Ridge, BC T2A 6L3 <br />

604-467-4251 <br />
604-467-4351 F <br />
2033 Thorne Avenue<br />
Ottawa, ON  K1H 5X4 <br />
613-723-6494 <br />
613-723-0969 F <br />
 <br />
(J.D. Pipe, Marc LaFontaine, Mark Howell) <br />
25 King's Landing Private<br />

Ottawa, ON K1S 5P8 <br />
613-723-6494 <br />
613-723-6494 F <br />
 <br />
(Michel Leroux, John Rosse) <br />
32 Labrador<br />
Kirkland, QC H9J 3W8 <br />
514-697-6853 <br />
514-697-6863 F <br />

4880 Couture<br />
St. Leonard, QC H1R 1C4 <br />
514-323-9045 <br />
514-323-8957 F <br />
 <br />
RunningBrook Inc. <br />
P.O. Box 161<br />
New Market, Alabama 35761 <br />
256-379-4840 <br />

AL,TN,GA, MS <br />
(Pat Brooks, Harry Brooks) <br />
256-379-4845 F <br />
 <br />
S.J. Associates <br />
500 North Broadway, Ste 159<br />
Jericho, NY 11573 <br />
516-942-3232 <br />
CT,DE, NH,NY, NJ, MA,MD, ME,PA,RI, VA,VT,  <br />

(Mark Wachtel) <br />
516-216-4943 F <br />
(Tom Faherty) <br />
33 Boston Post RD. W., Suite 310<br />
Marlboro, MA 01752 <br />
508-485-2700 <br />
508-485-2702 F <br />
(Shane Erickson <br />
15 Coventry Lane<br />

Naugatuck, CT 06770 <br />
203-723-4707 <br />
203-723-1629 F <br />
(Dan Rysz) <br />
131-D Gaither Drive.<br />
Mt. Laurel, NJ 08054 <br />
856-866-1234 <br />
856-866-8627 F <br />
(Jeffrey Land) <br />

803 West Broad Street, Suite 750<br />
Fall Church, VA 22046 <br />
703-533-2233 <br />
703-533-2236 F <br />
 <br />
Technology Solutions <br />
462 NE Bluefish Pt<br />
Port St. Lucie, FL 34983 <br />
772-834-8553 <br />

FL <br />
(Bill Jette) <br />
772-873-8060 F <br />
(Mike Rada) <br />
4550 47th Street W.  Apt # 917<br />
Bradenton, FL 34210 <br />
941-761-2337 <br />
941-761-2478 F <br />
(Janet Murphy, Paul Murphy) <br />

610 Hampshire Lane<br />
Holmes Beach, FL 34217 <br />
813-690-1838 <br />
941-778-2395 F <br />
(Charlie Bostick) <br />
7340 NW 75th Street<br />
Tamarac, FL 33321 <br />
954-205-9717 <br />
954-720-6111 F <br />

 <br />
Western Technical Sales, Inc  <br />
13400 Northup Way, Suite #20<br />
Bellevue, WA  98005 <br />
425-641-3900 <br />
WA, OR <br />
(Bob Brunjes, Ralph Loesch, Sue Hopper,<br />
Stephanie Labo) <br />
425-641-5829 F <br />

(Jim Wyland) <br />
122 N. Raymond, Suite #5<br />

Spokane, WA  99206 <br />
509-922-7600 <br />
509-922-7603 F <br />
(Pete Thunem, Stanley Crisp, Scott Martin,<br />
Cindy Meyer) <br />
3720 SW 141st Ave Ste # 200<br />
Beaverton, OR 97005 <br />

503-644-8860 <br />
503-644-8200 F</div>
<br />
<br />
<br />
<br />
<br />
Here is a nice flat solution that is more along the lines of what some were dreaming about- it looks more like thick copper tape:<br />
<br />
<i>"A new heat spreader technology from Celsia Technologies uses ultra-thin
chambers of fluid divided by a vaporization zone that are 1.4mm thick, and
boast a thermal conductivity of over 5,000 w/m-K, compared to 386 w/m K for copper or 205 w/m-K for aluminum, two common heat spreader materials. As an example of the price-performance of the Microspreader, George Meyers VP of sales, claims a personal computer design that currently relies on a $4 fan assembly could replace it with a Microspreader with a similar cost that is lighter, smaller and more reliable.</i><br />
<br />
<a href="http://www.edn.com/blog/1470000147/post/230004823.html?nid=2432&amp;rid=1016492294" target="_blank">http://www.edn.com/blog/1470000147/...&amp;rid=1016492294</a></div>
<br />
<br />
Heatpipes come in many forms and construction methods.  Just because one contruction method has issues under a certain environment, does *NOT* mean that all construction methods will have the same problem.<br />
<br />
<br />
You will find that the heatpipes used in laptops, which are used on the go (vibration etc.), and are actually employed in a sideways (horizontal) fashion, bent usually several ways, deformed from round, don't have a condenser on one end and an evaporator on the other.<br />
<br />
With the capillary structure from one end to the other, and all along it's length, you can even put the heatsource (or the cooling area/fins/plate) in the middle, or along a whole portion of it.<br />

<br />
If you buy some of the ones you find in laptops, when you shake it, you will even find there is no sloshing liquid.  The capilary structure is saturated, but no additional liquid is inside.  In fact, the evaporator and condensor structure are one the same in these heatpipes.  It is the capilary structure itself that serves as the evaporator, where the water boils off under the vacuum, in the hot area.  Now, this hot vapor, carrying the heat with it, goes to the cooler area in the heatpipe and condenses on that area.  The structure it actually condenses on, is that the same capillary structure, which- in this type of heatpipe, runs from end to end.  The nifty thing is, that capillary structure that it evaporates from and condenses on, is one and the same, and so it is automatically captured by nature.  <br />
<br />
This prevents this sloshing issue you are talking about in these types of heatpipes.  <br />
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These heatpipes which are used in laptops/heatsinks have *extremely* thin walls, a very fine capillary structure, and are very low mass.  And do get into the under one dollar range, mine cost me 2-3 dollars, depending on which size (diameter and length), due to the fact I only purchased a few.  <br />
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You will find that in laptops, the heatpipe orientation is horizontal...<br />
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Did you know the Space Shuttle uses thousands of heatpipes?  They are found in a wide variety of areas, and not only in the electronics.  <br />
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Heatpipes could be suitable for use on flashlights and work *great* in a horizontal application.  I do have a prototype flashlight I built three years ago which has heatpipes in it, and they do a very awesome job, sideways, upside down, when shaken, and especially work great for transporting the heat from the LED to a human hand.  They also do a great job of spreading the heat down the length of the flashlight, even when I orient it horizontal or upside down.<br />
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Thats why I have recommended them several times since I showed up on CPF in 2003 (I used to have a different account, search for Jarhead).<br />
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Some specs on heatpipes can be found by going here and clicking on the text below the heatpipes of different diameters:<br />
<a href="http://www.avc.com.tw/products/oem/nb%20thermal-products/index--b.html" target="_blank">http://www.avc.com.tw/products/oem/...s/index--b.html</a><br />
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Another manufacturer and specs:<br />
<a href="http://www.acktechnology.com/Heat%20Pipe.htm" target="_blank">http://www.acktechnology.com/Heat%20Pipe.htm</a><br />
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Places to learn more:<br />
<a href="http://www.cheresources.com/htpipes.shtml" target="_blank">http://www.cheresources.com/htpipes.shtml</a><br />
<a href="http://www.lanl.gov/orgs/esa/epe/Heat_Pipe_Site/ancient4.html#Cott_65" target="_blank">http://www.lanl.gov/orgs/esa/epe/He...t4.html#Cott_65</a><br />
<a href="http://www.transterm.ro/overview.htm" target="_blank">http://www.transterm.ro/overview.htm</a><br />
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Other interesting cooling technologies:<br />
<a href="http://www.stanford.edu/group/microheat/hex.html" target="_blank">http://www.stanford.edu/group/microheat/hex.html</a></div>
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