Factory sound deadener

Topic: Factory sound deadener (Read 5114 times) previous topic - next topic

Factory sound deadener

Reply #30 – February 12, 2008, 08:01:41 PM

ok, right, because temperature transmits slower through the air than the sheetmetal/walls, etc.... right? I guess I'm still confused on what Jeremy was getting at and what would work best for blocking the heat transfer through my floorboards.

Factory sound deadener

Reply #31 – February 12, 2008, 08:51:41 PM

pretty much, insulate for sound and heat the way your planning.
unless you had a way to create an airspace on your floor somehow,
you'll be stuck like the rest of us trying to block heat the best we can.
the foil in the mat will still help
Another way to cut heat would be putting a shield between your exhaust and floor.
or heat insulate your pipes

Factory sound deadener

Reply #32 – February 12, 2008, 09:09:02 PM

LOL, well, I'm glad I don't care if I feel stupid but I have to say, I didn't even think to wrap the pipes! :hick:

Factory sound deadener

Reply #33 – February 12, 2008, 09:16:36 PM

:D Lol

Factory sound deadener

Reply #34 – February 13, 2008, 02:40:07 PM

Heat transfer via radiation between two surfaces is described by the equation:

Q/A = ε*σ*( T^4 -Tc^4)

Where, Q/A=Heat transfer per area (W/m^2)
Where, ε=Emissivity
Where, σ=The Stefan-Boltzmann Constant (5.6703 10-8 (W/m^2K^4)
Where, Th=Temperature of the hot body (K)
Where, Tc=Temperature of the cold body (K)

Q stands for heat transfer, and A stands for area. So Q/A is heat transfer per area.
We'll assume emissivity is 1. The Stefan-Boltzmann constant is a constant, so it doesn't do anything but get multiplied.

The important concept to come away with is that radiation is dominated by temperature to the 4th power.

Another is how radiation heat transfer occurs. Radiation requires a medium (be it air or a vacuum) gap to occur. If you take a hot surface, and then place a radiant barrier directly on it, the radiant barrier isn't stopping any radiative heat transfer. Heat is instead being conducted through the barrier. If you moved the barrier out an inch from the wall, then the barrier would being to reflect the radiant heat coming from the hot surface.

Also, radiation travels in a straight line. It has a line of sight. For example. Say you're outside facing a bonfire on a cold night. The radiant heat of the flames is heating you quite nicely, then somebody puts them self between you and the flames and begins to strike up a conversation. All of a sudden it gets cold. This is because that person's backside is now in the direct line-of-sight with the flames and you aren't- thus they are absorbing all of the radiant heat and you're cold again.

I'm too lazy to look up convection coefficients and thermal conductivities to compare them with radiation, but I'll just show how radiation is really depend on temperature.

On a hot day, the underside of your car (Tc) is 100 degrees. The asphalt (Th) below your car is 130 degrees.
Plugging and chugging into the equation at the beginning of the post gives you Q/A=123.1
Remember to convert Fahrenheit to Kelvin for the formula.

Now let's compare that to the part of car that is exposed to the exhaust downstream of the catalytic converter. Tc is still 100 degrees. Th (Exhaust surface temperature) is 300 degrees.
Q/A=1269.0
Q/A is 10 times greater, even though the temperature difference is only 6.5 times greater.

Assume you have a set of long tube headers (Th) at 500 degrees and an exterior firewall (Tc) firewall temperature of 100 degrees. Q/A=4051.7

Lastly, imagine a race car with the headers (Th) at 1300 degrees, with a firewall (Tc) temperature of 100 degrees.
Q/A=51262

The absolute temperature difference between the first and last case is 40 times. The radiative heat transfer difference is 416 times!
This contrasts with heat transfer via conduction. A temperature difference twice as great will result twice the heat transfer.

Below is a graph illustrating how heat transfer increases as the temperature difference increases. Note that Tc is constant at 100 deg F.

Factory sound deadener

Reply #35 – February 13, 2008, 02:51:29 PM

As daminc said, without an air gap, the aluminum foil is not acting as a radiant barrier. The foil primarily acts as a physical barrier between the gooey butyl and its environment (carpet, feet, spilled coffee).

Factory sound deadener

Reply #36 – February 13, 2008, 03:04:46 PM

[homer simpson] ahhhhh, coffee [/homer simpson]

Ok, so long story short, neither the foil nor the foil backed fatmat is any better without the air gap...? dude, you know to much technical stuff! You got a girlfriend?!? Jk, wish I knew that much! Ha!

Factory sound deadener

Reply #37 – February 13, 2008, 03:23:43 PM

Quote from: booksix;203942

Ok, so long story short, neither the foil nor the foil backed fatmat is any better without the air gap...?

I'm not sure I understand you...
Long story short, applying the foil inside will do a poor job in insulating the cab from outside heat. The foil portion of the fatmat/dynamat/damplifier will do a poor job of insulating the cab from heat, but the butyl portion of those products will insulate your vehicle.
Furthermore, the best way to insulate the cab from radiant heat is to apply a radiant barrier to the exterior firewall, transmission tunnel, and sheet metal directly above the exhaust system.

Quote

dude, you know to much technical stuff! You got a girlfriend?!? Jk, wish I knew that much! Ha!

Factory sound deadener

Reply #38 – February 13, 2008, 04:36:58 PM

Yeah, I get now that I'd really need to use it on the outside, but what I'm trying to determine is whether adding radiant foil to the top of the two layers of fatmat will make any difference. So, long story short, meaning, all your technical crazy stuff applied to my question would give me a no.

Factory sound deadener

Reply #39 – February 13, 2008, 04:40:53 PM

Bingo!

Factory sound deadener

Reply #40 – February 13, 2008, 05:02:23 PM

LOL Thanks!

Factory sound deadener

Reply #41 – February 13, 2008, 05:17:10 PM

So wait now, if I put radiant foil on the bottom of my floor boards (between the exhaust and the floor) how would that thin layer of foil do anything more than the sheet metal floor would to stop radiant heat? It has no more of an air gap than the floor does from the pipes...

Factory sound deadener

Reply #42 – February 13, 2008, 05:35:38 PM

The foil reflects much more of the incoming radiative heat than the painted sheet metal.

Factory sound deadener

Reply #43 – February 13, 2008, 05:42:01 PM

ok, good enough for me! :hick:

Factory sound deadener

Reply #44 – February 13, 2008, 05:51:17 PM

Boy, what did I miss today.

I believe I saw radiant panels for the underneath of a car.
Not sure if it was a magazine or web.
But after reading that college course post, my smaller brain went ding. and remembered seeing it before. I'll let you know if I find it.
JeremyB, what do you do for a living?
Please don't tell me your a mail man. lol