Re: Why are ailiners white? Old vs. New

Date:         03 Oct 97 01:18:34 
From:         Steve Lacker <look@the.sig>
Organization: Applied Research Laboratories - The University of Texas at Austin
References:   1 2
Followups:    1 2
Next article
View raw article
  or MIME structure

Bizfixer wrote:
>>This is a major part of why the
>>SR-71 is black- to radiate as much heat as possible. etc.

>True, but not relevant to subsonic aircraft.

True, but we were talking about the Concorde at the time :-)

> <<Why are airliners painted white?>>
> As some posters have hinted, airliner paint has to do with heat issues.
> Early APU's were also inadequate for anything over 45 minutes on the
> ground, and ground units continued to be used to supplement them for longer
> ground stays (overnights, long turn-arounds, etc.).

I came across an interesting claim the other day. I've always assumed
that from the very beginning, jet aircraft airconditioning systems have
operated on the same principle they do today. Ie, take hot bleed air,
cool it while still highly pressurized in a heat exchanger, pass it
through an expander valve so that it expands and gets cold. However, I
was snooping around Carrier's web site (the air conditioning company)
and they claimed the following as one of their "firsts":

1955:   With the advent of jet passenger service, Carrier develops an
        air-turbine-driven centrifugal refrigeration machine to cool the
        Douglas Aircraft Company's DC 8. Although small enough to fit
        inside a small piece of carry-on luggage, it was powerful enough
        to air condition seven average sized homes.

Technically, a "centrifugal refrigeration machine" is basically a
chiller, using refrigerant, a centrifugal compressor, and appropriate
heat exchangers (evaporator and condenser).  This seems ridiculously
complex for an aircraft, when the bleed air is nearly free (although I
realize that JT3's couldn't spare nearly as much bleed air as today's
engines). So I wonder if this is incorrectly described on Carrier's web
page or if it was used briefly then supplanted by the "pack" system we
know today. Anyone familiar with this?

Stephen Lacker
Applied Research Laboratories, The University of Texas at Austin
PO Box 8029, Austin TX 78713-8029
512-835-3286 (Remove the extra 'x' to mail me)