As a retired AC/R tech,that just happens to be a Stanford EE,pls be advised
that by most codes and HVAC standards,you pull the the cooling over the
surface to be cooled.Assuming your refrigerator is functional,take a match
and light it in front of the evaporator fan motor outlet in the freezer:it
best be blowing toward you-if not you have big problem with food
spoliage.(and one big electric bill)
Am running a Jupter on PSK-31,have a big computer fan mounterd on the heat
sink-it pulls the cool air thru the heat sink and exhausts the warm air out
the back.
Basic high school phyiscs folks.
Bill Fulling
w4njf@email.midflorida.com
----- Original Message -----
From: "KE4TEG" <ke4teg@bellsouth.net>
To: <tentec@contesting.com>
Sent: Monday, March 03, 2003 9:44 AM
Subject: Re: [TenTec] Delta II Cooling Fan
> Mitch and Jeff,
>
> I tend to agree with the HVAC companies and Jeff especially for a
commercial
> application. But with HVAC, the fan units have the fan mounted in the top
of
> the unit with the heat source on all four sides as in a residential
heatpump
> or in a cowling built above the heat source with the fan mounted in it.
> These are large commercial fan units that do make there own heat and in
most
> cases are always pulling the air up and out so as again not to fight the
> natural flow of heats tendency to rise. They also only run when the unit
is
> trying to either heat or cool something. They do not care about excess
heat
> once a given temperature is reached. A heatsink is still trying to
dissipate
> heat after you have unkeyed.
>
> What you have is a heatsink with no chamber formed from the condenser fins
> and no cowling to mount the muffin fan in to hold it up off the heatsink.
> This is why I do not care for top mounting the muffin fan. It impedes
> natural heat flow and only helps when it is running. If the muffin fan
dies,
> it will only make your heat problem worse if top mounted. Also with a
bottom
> mounted fan pushing air through the heatsink, the fan is out of the way
for
> short QSOs that the fan does not need to be on for and causes little
affect
> to natural heatsink cooling. Do not get me wrong, even mounting a small
> muffin fan on the bottom does effect the heatsinks normal performance, but
> not as much as top mounting it.
>
> This is also why most fan kits that one can buy for radio equipment have
two
> muffin fans built into a cowling that mounts onto the heatsink covering
the
> minimum heatsink area to get it mounted. Most of these units mount to the
> back of the heatsink and blow air sideways into the heatsink with air
> spilling out the top and bottom of the heatsink. This is done for two
> reasons, one it keeps the amp or radio pack size the same as the original
> unit other then depth. If measurements must stay as close to the original
as
> possible for an application, depth is usually the one that can be cheated
> on. Two, it keeps the fan unit out of the way and gives it some protection
> by the unit it is mounted to. Its not the most inexpensive way to do it or
> the most efficient, but when adding 2 additional fans with a cowling to
> force air over the heatsink one has increased the efficiency of the
heatsink
> so greatly it does not matter about the rest.
>
> I guess all in all its a toss-up. It comes down to what works best for you
> and what is easiest for the unit the muffin fan is going on and where one
> has the equipment located. As long as the fan is always on when the amp is
> on, the heatsink will always be more efficient with a fan mounted
somewhere
> then with no fan at all.
> 73, Keith
> de KE4TEG
>
> ----- Original Message -----
> From: "Jeff Modlin" <kd4znc@arrl.net>
> To: <tentec@contesting.com>
> Sent: Sunday, March 02, 2003 8:29 PM
> Subject: RE: [TenTec] Delta II Cooling Fan
>
>
> > Mitch,
> >
> > HVAC convention is to have cooling fans suck the air over the heat
> > source. The simple reason is that the heat generated by the motor and
> > the friction losses in the machine add energy to air and consequently
> > raise the temperature. So the air being pushed by a fan has slightly
> > more energy in it than air pulled by a fan.
> >
> > All of this being said and referencing KE4TEG's reply, having the fan
> > pulling air over the fins is better as long as the fan is on. If for
> > the sake of noise reduction or any other reason, the fan is switched
> > off; its presence will impede cooling.
> >
> >
> > 73 de Jeffrey Modlin
> > KD4ZNC in Coral Springs, Florida USA
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: tentec-bounces@contesting.com
> > [mailto:tentec-bounces@contesting.com] On Behalf Of Mitch Alexander
> > Sent: Sunday, March 02, 2003 6:34 PM
> > To: tentec@contesting.com
> > Subject: Re: [TenTec] Delta II Cooling Fan
> >
> >
> > Hi, Guys --
> > Just relaxing after the contest weekend. It's not 0:00 yet, but I'm
> > finished. Whew !!
> > I've always wondered which is the correct mounting for a cooling fan --
> > blowing cool air onto the heat sink, or drawing the heat away? In other
> > words, blowing in or blowing out ? I have muffin fans on the top of my
> > amp drawing the air out of the tube chimneys -- same principal for heat
> > sinks, or not?
> > cheers--
> > Mitch Alexander -- KJ4DX
> >
> > Greg Breeden <gbreeden@pivot.net> wrote:List,
> >
> > I am looking for a cooling fan for my Delta II. It looks as though any
> > fan
> > would work, provided it would fit the pre drilled screw holes in the
> > heat
> > sink and was 12 volts.
> >
> > Can anyone direct me to a good source for this fan, or even the factory
> > fan
> > which you would part with at a reasonable cost.
> >
> > Greg, AL0A
> >
> > in Maine where it is snowing again...
> >
> > _______________________________________________
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> > TenTec@contesting.com
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> >
> >
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