TECHNET Archives

March 2005

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Roach, David" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Roach, David
Date:
Mon, 21 Mar 2005 11:32:58 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (155 lines)
The temperature rise also depends on the geometry of the heat sink (which
would be factored into the temperature rise spec on the heat sink) and the
air flow around the heat sink, which is what makes the temperature rise
difficult to calculate.  Often there is only natural convection, where the
only air flow is created by the heat produced by the board.  The amount of
air flow here, and thus the temperature rise, would be highly dependent on
how well the air can circulate around the heat sink.  If there are other
tall components near the heat sink, these will restrict air flow, so there
will be a larger temperature rise.  Likewise, if there is an enclosure that
limits air flow, there would be a higher temperature rise.  If there is
forced convective cooling, as would be produced by a cooling fan, the heat
will be transferred away more quickly, so the temperature rise will be less.
The heat transfer rate is also somewhat dependent on the temperature and
humidity of the air, as these affect the thermal and convective properties
of the air somewhat.

Calculating the heat rise it these cases is difficult.  The geometry is
likely complex enough that numerical methods (i.e. computer simulation)
would be needed to calculate the temperature rise.  It is usually easier,
faster, and probably more accurate to measure the actual temperature rise on
an operating board in its normal environment.  Even if numerical methods
were used to calculate the temperature rise, the results should be verified
by testing an actual board.

Heat sink manufacturers that provide specs for thermal characteristics of
heat sinks must be making some assumptions about the environment (type of
air flow) to provide a spec on heat dissipation.  They likely have this
information somewhere on their spec sheets.

Dave Roach


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair K. Hogg
Sent: Monday, March 21, 2005 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] Temperature conversion

Generally a wattage output is referenced into a temperature rise, e.g. x
Watts will result in y degrees C rise over ambient. Heat sinks are usually
specified in terms of W/deg C as to how well they will cool. The temperature
rise in deg C per W will depend upon the material, e.g., 18 gauge wire will
have more or a rise than 12 gauge (and of course 12 ga will have lower
resistance per foot). But that's about the limit of my knowledge on the
subject.

Blair Hogg
QA Manager, GAI-Tronics Corp.

>>> [log in to unmask] 03/21/05 11:05AM >>>
That's what I was thinking. I like the hp to speed analogy.

Jason Gregory
Manufacturing Engineer
Innova Electronics
(281)653-5593
(281)653-5594 fax
(281)212-0844 cell
[log in to unmask]


-----Original Message-----
From: Blomberg, Rainer (FL51) [mailto:[log in to unmask]]
Sent: Monday, March 21, 2005 9:58 AM
To: TechNet E-Mail Forum; Jason Gregory
Subject: RE: [TN] Temperature conversion


I don't think so.  It would be like converting Horsepower to speed

> Rainer G. Blomberg
> Honeywell -Space Systems Clearwater
> Staff Production Engineer
(727) 539-5534


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jason Gregory
Sent: Monday, March 21, 2005 10:55 AM
To: [log in to unmask]
Subject: [TN] Temperature conversion

Is there any way to effectively convert a wattage output to a known
temperature?

Jason Gregory
Manufacturing Engineer
Innova Electronics
(281)653-5593
(281)653-5594 fax
(281)212-0844 cell
[log in to unmask]

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in the
BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send
e-mail to [log in to unmask]: SET Technet Digest Search the archives of
previous posts at: http://listserv.ipc.org/archives Please visit IPC web
site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

*******************************************************************
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom they
are addressed. If you have received this email in error please notify
the system manager.

This footnote also confirms that this email message has been swept
for the presence of computer viruses.

www.hubbell.com - Hubbell Incorporated

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2