Thermal Considerations 01/17/2008tmurphy/phys121/lectures/04_thermal.pdf · Thermal Considerations...

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Thermal Considerations 01/17/2008 Lecture 4 1 Winter 2012 UCSD: Physics 121; 2012 2 Winter 2012 UCSD: Physics 121; 2012 3 Winter 2012 UCSD: Physics 121; 2012 4 Material κ (W m -1 K -1 ) comments Silver 422 room T metals feel cold Copper 391 great for pulling away heat Gold 295 Aluminum 205 Stainless Steel 10–25 why cookware uses S.S. Glass, Concrete,Wood 0.5–3 buildings Many Plastics ~0.4 room T plastics feel warm G-10 fiberglass 0.29 strongest insulator choice Stagnant Air 0.024 but usually moving… Styrofoam 0.01–0.03 can be better than air!

Transcript of Thermal Considerations 01/17/2008tmurphy/phys121/lectures/04_thermal.pdf · Thermal Considerations...

Page 1: Thermal Considerations 01/17/2008tmurphy/phys121/lectures/04_thermal.pdf · Thermal Considerations 01/17/2008 Lecture 4 1 Winter 2012 UCSD: Physics 121; 2012 2 Winter 2012 UCSD: Physics

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Material κ (W m-1 K-1) comments

Silver 422 room T metals feel cold

Copper 391 great for pulling away heat

Gold 295

Aluminum 205

Stainless Steel 10–25 why cookware uses S.S.

Glass, Concrete,Wood 0.5–3 buildings

Many Plastics ~0.4 room T plastics feel warm

G-10 fiberglass 0.29 strongest insulator choice

Stagnant Air 0.024 but usually moving…

Styrofoam 0.01–0.03 can be better than air!

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•  Note that these examples use the non-SI definition and are per inch. Vacuum insulated panel has the highest R-value of (approximately 45 in English units) for flat, Aerogel has the next highest R-value 10, followed by isocyanurate and phenolic foam insulations with, 8.3 and 7, respectively. They are followed closely by polyurethane and polystyrene insulation at roughly R–6 and R–5. Loose cellulose, fiberglass both blown and in batts, and rock wool both blown and in batts all possess an R-value of roughly 3. Straw bales perform at about R–1.45. Snow is roughly R–1.

•  Absolutely still air has an R-value of about 5 but this has little practical use: Spaces of one centimeter or greater will allow air to circulate, convecting heat and greatly reducing the insulating value to roughly R–1

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