07_Properties_GB_2008

# 07_Properties_GB_2008 - Thermal Properties of Materials...

This preview shows pages 1–10. Sign up to view the full content.

Thermal Properties of Materials Arch 140, Lecture #7 - Tuesday, Feb 12, 2008

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
CONDUCTION T hot T cold Δ T d A Q Q = heat flow (Btu/hr) d = thickness (in) Δ T = temperature (ºF) A = area (ft 2 ) k = conductivity Btu-in hr- ft 2 -ºF k
CONDUCTION T hot T cold Δ T d A Q Q = x A x Δ T k d Q = heat flow (Btu/hr) d = thickness (in) Δ T = temperature (ºF) A = area (ft 2 ) k = conductivity Btu-in hr- ft 2 -ºF k

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Q = x A x Δ T k d CONDUCTION Btu 1 * Btu-in * ft 2 * °F hr in hr-ft 2 -°F = d = thickness (in) Δ T = temperature (ºF) A = area (ft 2 ) k = conductivity (Btu-in/hr- ft 2 -ºF)
Q = x A x Δ T k d CONDUCTION Btu 1 * Btu-in * ft 2 * °F hr in hr-ft 2 -°F = d = thickness (in) Δ T = temperature (ºF) A = area (ft 2 ) k = conductivity (Btu-in/hr- ft 2 -ºF)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
A * 1/rd * Δ T hr-ft 2 -ºF/Btu-in r resistivity A * 1/R * Δ T hr-ft 2 -ºF/Btu R resistance A * C * Δ T Btu/hr-ft 2 -ºF C conductance A * k/d * Δ T Btu-in/hr-ft 2 -ºF k conductivity Heat flow,Q= Units Symbol Property “___ivity” = property of a material (independent of amount) “___ance” = property of an object (depends on amount) C = 1/R = k/d = 1/dr or R = d/k Alternative Measures of Conductive Properties
Conductive Properties of Typical Building Materials 4.26 Water (still) 0.17 Air (still) 1500. Aluminum 310. Steel 1.72 8” concrete block 12. Stone 0.6 3” common brick 5.0 Brick 0.05 ¼” glass 5.4 Glass 4.3 2x4 wood stud 0.8 Wood (soft) 19.0 5-1/2” insulation 0.3 Insulation (hr-ft2-°F/Btu) Resistance, R Component (Btu-in/hr-ft2-°F) Conductivity, k Material See Reader, Appendix 5 for property values NOTE: R = d/k

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Example • 4" thick wall of concrete, k = 12 (Btu-in / hr-ft 2 -ºF) • Find R = d/k = 4 (in) / 12 (Btu-in / hr-ft 2 -ºF) = 0.33 hr-ft 2 -ºF/Btu
• 4" thick wall of concrete, k = 12 (Btu-in / hr-ft 2 -ºF) • Find R = d/k = 4 (in) / 12 (Btu-in / hr-ft 2 -ºF) = 0.33 hr-ft 2 -ºF/Btu • If the wall was 10 ft 2 and had a 5ºF temperature difference across it, how much heat would flow? Q

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 36

07_Properties_GB_2008 - Thermal Properties of Materials...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online