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rparigoris
Joined: 24 Nov 2009
Posts: 796
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 Posted: Mon Sep 17, 2012 2:27 pm Post subject: Blow or suck (on a heat sink)? |
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Hi group
I decided I'm an idiot when it comes to refrigeration.
I made a slick carry tote for a 12 volt 9 pound battery, with holder for the jumper cables and a super powerful flashlight. I will share pics once I complete the project.
During the summer I ruined my 35MM digital camera by leaving it in a "very" hot car. I asked my EE build partner when we got the camera and he assured me, no problem, heat will not kill it.
OK now to my question. I figured I would make an insulated compartment on my carry tote to put my camera in and use a piezo cooler to keep it at less than "nonpassive failure" temperature. My EE build partner gave me a Peltier made for a CPU chip. I fooled with it and was happy enough feeling the cold to install it. What a failure. I could easily "raise" the inside temperature by 15 degrees, and after a lot of fooling was able to get my cooler to only raise the temperature 2 degrees F over ambient.
Going forward and using the mentality to never let a mechanical or electrical device get the better of you, I bought a do it yourself refrigeration kit off of E-Bay. BTW the compartment is now large enough for 2 soda cans or the new camera, and I figure for camera ops, I may be able to electrically series the two Peltier device inputs to lower the power drain (will try it and report). Side note I never knew that you can series stack Peltier devices together in series (hot to cold) to increase both heating and cooling.
Sorry for the rambling, my question:
I purchased this kit:
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=180885684793&ssPageName=ADME:L:OU:US:3160
No instructions. On the hot side heat sink, do I want to blow or suck with the fan? On the cold side heat sink, do I want to blow or suck with the fan?
Thanking you in advance.
Ron Parigoris
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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mrspudandcompany(at)veriz
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| Posted: Mon Sep 17, 2012 5:14 pm Post subject: Blow or suck (on a heat sink)? |
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| Quote: | No instructions. On the hot side heat sink, do I want to blow or suck with
the fan? On the cold side heat sink, do I want to blow or suck with the
fan?
Ron Parigoris
|
It is almost always better to "Suck than to blow". For either a heating
or cooling application. If you are directing a fan to blow on a heat sink,
a larger quantity at a higher velocity makes contact with the sink and more
of the heat is transferred. On the "Suck" side of the fan the air moves in
from a wider area and is not as effective unless you specifically design a
shroud to direct the airflow across the sink.
Roger
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retasker(at)optonline.net
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| Posted: Mon Sep 17, 2012 7:34 pm Post subject: Blow or suck (on a heat sink)? |
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Your description is fine, but the first sentence is opposite of the description. I think you meant to write "better to blow than suck"
Dick Tasker
R. curtis wrote:
| Quote: |
> No instructions. On the hot side heat sink, do I want to blow or suck with the fan? On the cold side heat sink, do I want to blow or suck with the fan?
> Ron Parigoris
It is almost always better to "Suck than to blow". For either a heating or cooling application. If you are directing a fan to blow on a heat sink, a larger quantity at a higher velocity makes
contact with the sink and more of the heat is transferred. On the "Suck" side of the fan the air moves in from a wider area and is not as effective unless you specifically design a shroud to direct
the airflow across the sink.
Roger
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nuckolls.bob(at)aeroelect
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| Posted: Mon Sep 17, 2012 7:34 pm Post subject: Blow or suck (on a heat sink)? |
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At 05:27 PM 9/17/2012, you wrote:
| Quote: |
<rparigor(at)suffolk.lib.ny.us>
Hi group
I decided I'm an idiot when it comes to refrigeration.
I made a slick carry tote for a 12 volt 9 pound battery, with holder
for the jumper cables and a super powerful flashlight. I will share
pics once I complete the project.
During the summer I ruined my 35MM digital camera by leaving it in a
"very" hot car. I asked my EE build partner when we got the camera
and he assured me, no problem, heat will not kill it.
OK now to my question. I figured I would make an insulated
compartment on my carry tote to put my camera in and use a piezo
cooler to keep it at less than "nonpassive failure" temperature. My
EE build partner gave me a Peltier made for a CPU chip. I fooled
with it and was happy enough feeling the cold to install it. What a
failure. I could easily "raise" the inside temperature by 15
degrees, and after a lot of fooling was able to get my cooler to
only raise the temperature 2 degrees F over ambient.
Going forward and using the mentality to never let a mechanical or
electrical device get the better of you, I bought a do it yourself
refrigeration kit off of E-Bay. BTW the compartment is now large
enough for 2 soda cans or the new camera, and I figure for camera
ops, I may be able to electrically series the two Peltier device
inputs to lower the power drain (will try it and report). Side note
I never knew that you can series stack Peltier devices together in
series (hot to cold) to increase both heating and cooling.
Sorry for the rambling, my question:
I purchased this kit:
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=180885684793&ssPageName=ADME:L:OU:US:3160
No instructions. On the hot side heat sink, do I want to blow or
suck with the fan? On the cold side heat sink, do I want to blow or
suck with the fan?
|
Doesn't matter . . . it's MOVEMENT of air over the
warmer/cooler surface that greatly improves the rate of
transfer for thermal energy. Suggest you review the
technical data for TEC parts at:
http://tinyurl.com/9fcv9l4
Particularly the instructions and tutorials. You
might wish to consider some form of temperature
control for the protected space. It may be that
the best choice for protecting the camera will
not secure a pleasantly cooled can of pop.
If you keep the camera too cold (below dew
point for surrounding atmosphere) there
is risk of condensing moisture on the camera's
inner workings when brought out into the warmer,
moist air.
Also, these critters are sorta cool but they
consume significant amounts of energy. Do a
load analysis after satisfactory protection is
achieved . . . then see how long you can let your
vehicle battery support his load and still get
the engine started. This will put DEEP cycles
on the vehicle battery and reduce its service life
considerably.
Passive protection might be more practical. Store
the camera in one of those zippered-lid insulated
carry cases (about a six pack size) along with
those reusable ice bags (not frozen). You're taking
advantage of the container insulation and relative
thermal mass of the freezing medium to maintain
the camera at day-long-average temperature which
will be many degrees cooler than worst case.
Bob . . .
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