[Amps] Fan for SB220

[Adrian]

  On 12/20/2010 08:12 AM, Fuqua, Bill L wrote:
> Adrian,
>      I give up. I think most everyone else gets it. It is like a conversation I had with some old hams, not much older than I am aboiut some large coax.
> They were convinced that since the center conductor was hollow you could run wires up thru it to carry current to lights and rotators without affecting the
> impedance of the coax. Their argument was that current only  flows on the outside of the conductors. But that is not always true.
> Current flows on the surfaces and in the case of a hollow conductor it is true it will flow on the outside as long there is nothing to electric
> create fields on the inside. There are electric/magnetic fields between the outside of the inner conductor and the inside of the outer conductor. But once you put a conductor on the inside of the hollow inner conductor you have created a new bit of transmission line, there are fields now between the new conductors and the inside on the inner conductor. That changes everything.
>
> 73
> Bill wa4lav
>
Bill, after seeing this from http://en.wikipedia.org/wiki/Radiator;


    Radiation and convection

One might expect the term "radiator" to apply to devices that transfer 
heat primarily bythermal radiation 
<http://en.wikipedia.org/wiki/Thermal_radiation>(see:infrared heating 
<http://en.wikipedia.org/wiki/Infrared_heating>), while a device which 
relied primarily on natural or forced convection 
<http://en.wikipedia.org/wiki/Convection>would be called a "convector". 
In practice, the term "radiator" refers to any of a number of devices in 
which a liquid circulates through exposed pipes (often with fins or 
other means of increasing surface area), notwithstanding that such 
devices tend to transfer heat mainly by convection and might logically 
be called convectors. The term "convector" refers to a class of devices 
in which the source of heat is not directly exposed.



    Theory of operation

 From an engineering perspective, a radiator varies from an idealblack 
body <http://en.wikipedia.org/wiki/Black_body>by a factor,?, called 
theemissivity <http://en.wikipedia.org/wiki/Emissivity>, which is a 
spectrum-dependent property of any material. Commonly, a fluidthermal 
mass <http://en.wikipedia.org/wiki/Thermal_mass>, containing the heat to 
be rejected, is pumped from the heat source to the radiator, where it 
conducts to the surface and radiates into the surrounding cooler medium. 
The rate ofheat flow <http://en.wikipedia.org/wiki/Heat_flow>depends on 
the fluid properties, flow rate, conductance to the surface, and the 
surface area of the radiator.Watts 
<http://en.wikipedia.org/wiki/Watt>persquare metre 
<http://en.wikipedia.org/wiki/Square_metre>are the SI units used 
forradiant emittance <http://en.wikipedia.org/wiki/Radiant_emittance>. 
If the system is not limited by theheat capacity 
<http://en.wikipedia.org/wiki/Heat_capacity>of the fluid, or thethermal 
conductivity <http://en.wikipedia.org/wiki/Thermal_conductivity>to the 
surface, then emittance, M is found by a fourth-power relation to 
theabsolute temperature 
<http://en.wikipedia.org/wiki/Absolute_temperature>at the surface. 
TheStefan-Boltzmann 
<http://en.wikipedia.org/wiki/Stefan-Boltzmann>constant is used to 
calculate it, as/M/= ??/T/^4 . Since heat may be absorbed as well as 
emitted, a radiator's ability to reject heat will depend on the 
difference in temperature between the surface and the surrounding 
environment. For particularoperating temperatures 
<http://en.wikipedia.org/wiki/Operating_temperature>, a system's overall 
heat flow may be given inthermal watts 
<http://en.wikipedia.org/wiki/Watt#Electrical_and_thermal_watts>, 
abbreviated W_t .


I see that the word radiate is used to describe heat transfer to "the 
surrounding cooler medium ".

In this case I would see this as convection heat transfer to air, but 
not radiation in the same sense as infra red radiation absorbed by black 
material. The terminology seems a bit loose.

However my point was that black material heated by an 3-500z infra red 
radiation source due to its absorption properties, releases that heat 
mainly by conduction and convection heat transfer within the amplifier 
framework and air flow within.

  If you say that the process of convection is the black radiating heat 
to the surrounding air, then we are on the same page.

Adrian ... vk4tux