On 11-06-21 11:04 AM, Jed Rothwell wrote:
Stephen A. Lawrence <[email protected] <mailto:[email protected]>> wrote:
Now, most of the energy of the bulb gets lost via convection to
the air, just as most of the energy of the hose gets lost that
way. For simplicity, let's assume the hose and the bulb both lose
*all* their energy that way.
That's fine for this estimate, but in real life a 3 m hose with hot
water or steam flowing through it does not lose all of the energy that
way. As you see in the video it was still plenty hot at the end.
Sorry -- I was not clear!
I meant, let's assume all losses along the line are conductive, with no
loss to radiation. That makes it easy to estimate the surface temp of
the hose, relative to the lightbulb.
In fact, I was ignoring the energy going into the hose in that
calculation, and just assuming it was losing GoatGuy's 150 watts, and I
was assuming the entire loss was via conduction through its skin.
That's about 40 degrees C, or about 104 degrees F. Even if I'm
off by a factor of 1.5 in one of the assumptions it's still not
going to be especially uncomfortable to touch a rubber hose which
is that hot.
My seat-of-the-pants estimate is that it would not be sensibly hotter
than the surroundings, or barely sensible. That is because a hose is
reasonably good insulation and water heated at one end will be nearly
as hot at the other end, at these flow rates.
- Jed
