The Physics of Foil

The Color of Money

2009-06-30T19:07:00.000-07:00

Remember the 1986 Pool Hall classic, The Color of Money, starring Paul Newman and Tom Cruise? I sure do. While the movie had many themes woven into the plot, I remember one thing: you can't make a leopard change its spots. Paul Newman's character, Fast Eddie was a retired billards player who had found the perfect protege, Vincent. The plan was for Fast Eddie to coach and Vincent to play. But in the end, Fast Eddie just couldn't stay away from the hustle, and he got right back into competing. Well, I just can't stay way from hustle and bustle of reflective foil insulation.

Pop quiz, kids... Two aluminum cans; one painted black, one painted white. Each filled with boiling water, and then left alone for a half an hour. Which can will lose more heat? The black one, the white one, or neither? The water in the black can will be cooler. Why? Black bodied objects gain and lose radiant heat quicker than lighter colored objects.

So what color is your money? Well, my money is green. And, I'm going green, because I just purchased 8 rolls of Attic Reflective Roil Insulation from INSULATIONSTOP.COM. I'm going to insulate my mom's attic. Hey Fast Eddie, want to make a BET that she's going to SAVE MONEY on her heating bill this winter?

Professor Foil Joins Technorati

2009-06-29T20:24:00.000-07:00

A Physics Simile: Like radiant heat bouncing back after hitting reflective foil, thephysicsoffoil blog will distribute through the Internet when hitting Technorati.

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Now, back to our scheduled blogging!

Radiant Barriers: They can save your life

2009-06-24T18:53:00.000-07:00

Back in 1964, our nations finest minds at NASA developed a material that would eventually end up in everyone's first aid kit: The Space Blanket. The space blanket is made of a lightweight piece of plastic that is usually coated with a very thin layer of aluminum. Once you're snuggled inside the space blanket, Presto! You are enveloped in a radiant barrier that is reflecting back 97% of your own radiant heat. Imagine being on an needing a emergency radiant barrier on an Adirondack mountain hiking trip.... The space blanket proabably saved that guy's life.

Now You See It... No You Didn't!

2009-06-17T20:33:00.000-07:00

Today, I was grilling the old fashioned way--using Kingsford Charcoal. 25 charcoal briskets, 1/2 cup lighter fluid (Butane: C4H10), a wand lighter, and 30 minutes of patience was all I needed to have my hamburgers cooking. While the grill was heating, I saw squiggly lines of air rise out the grill. Uh...professor...I know, I know...THAT is radiant heat, I see it, I see it. Nice try kid, but unless you're from the planet Krypton, your human eyes aren't capable of detecting radiant heat. Radiant heat is electomagnetic energy that travels outside of the visible spectrum. What you saw is a mirage caused by the differential in air density which causes a differential in the refractive index of two air spaces.

So if you're frustrated that you can't see radiant heat, don't despair. Change into your Superman Underroos, unroll a piece of aluminum foil and place your face near the sheet. Can you feel the heat from your face? THIS is Radiant Heat. Congratulations, now you're the man of steel! Well, maybe just aluminum.

Cool Car, Cool House

2009-06-14T19:56:00.000-07:00

Writing the last article regarding aluminum cast block engines sparked up a bit of nostalgia--summer rides home from the waterpark in Dad's Cadillac. The sun would bake the cars for hours while we were sliding down curved sections of fiberglass deluged with water. After a few hours, we would call it quits and head home. After finding the Caddy, Dad would unlock the doors and we would jump right in. Everybody else in the parking lot would open their car doors, roll down the windows, and wait a couple of minutes for the stifling heat to dissipate from the car. Not us, we were half way home, while everyone else was busy burning the underside of their bare legs. What was the Professor Foil Senior's secret? He used a foil sun shade to minimize the amount of radiant heat that could be absorbed into the leather seats.

If a foil backed cardboard sun shade can work for a car, why couldn't it work for a house? It already does. Housewraps are being used in new construction everywhere across the country. The lightweight and reflective radiant barrier properties of this building material make a huge difference in the total amount of heat transfer allowed through the walls of the building structure. In fact 96% of the radiant heat that attempts to traverse through the protected structure is blocked. How can this be professor? Simple, the inert properties of aluminum make this possible.

By the way, the sunshade in Dad's old Cadillac wasn't the only cool accesory item. So was the digital display that calculated our gas mileage (economy) and remaining miles (range)!

Heat Capacity, Specifically?

2009-06-08T14:26:00.000-07:00

Heat Capacity is the capacity of a body to store heat. It is measured in energy units per temperature units, or J/°C. Time out professor.. Please explain. OK, but first let's define specific heat capacity (Cp). Specific heat capacity is defined by how much heat you have to add or remove from an object to change its temperature. Essentially heat capacity can be understood as how well an object can maintain its temperature compared to other objects. Let's look at specific heat capacities (J mol−1 K−1) for different materials.

Aluminum 0.24
Gasoline 2.22
Copper 0.385
Water 4.18

Materials with low specific heat capacities are excellent conductors because they can change temperature quickly. That is why you are using copper pots and I still have that trusty aluminum pot. Materials with high specific heat capacities are excellent insulators because they can't change temperatures quickly.

Whiz kids, let's put this in perspective: if we wanted to equally raise the temperature of the same mass of aluminum and the same mass of water, we would need 17.41 times more heat applied to the water. Ever heard of the liquid cooled engine? While some of the coolant contains antifreeze chemicals, most of its contents are water--a superb insulator. So even though that engine's light weight aluminum (easy to heat) block is heating up fast, it is kept cool because of the water (hard to heat) running through it.

Aluminum (Al): Great Conductor and Great Insulator. How Can This Be?

2009-06-06T10:29:00.000-07:00

The other day, I was boiling corn on the cob for a family cookout using my old college workhorse pot. Its durability and effectiveness is attributed to one thing: Aluminum. Aluminum is a very strong and ductile material that also has a low heat capacity (Cth). Uh….professor, what does that mean? Simple: This pot is rough and tough and when you put it contact with a flame, it is going to heat up—fast!

That same day, I was up it my attic gathering some old family photo albums. The temperature outside was 85°, a little warm for this time of year. Yet, I was relatively comfortable rummaging through the attic. The secret: Aluminum. I have installed an aluminum radiant barrier in my attic. Aluminum has an extremely low level of emissivity (e). Uh…professor, you’re losing me, please explain? Simple: The aluminum foil is reflecting the outside heat, thereby insulating the attic!

So if I use aluminum to cook with, because it heats up fast, why would I dare use it to insulate with? After all, isn’t the point of insulation to NOT allow things to heat up fast?

The answer lies in the fact that heat is transferred in three separate mechanisms: conduction, convection, and radiation. My tasty corn on the cob is quickly warmed because the flame from the stove is in direct contact with the aluminum: A great conductor for conduction of heat. My attic is cool because the radiant heat from the outside is reflected by the aluminum: A great insulator for radiation of heat.