Presentation on theme: "Temperature of a 100 W Light Bulb Filament Joran Booth and Peter Hyatt ME 340 Winter 2009."— Presentation transcript:
Temperature of a 100 W Light Bulb Filament Joran Booth and Peter Hyatt ME 340 Winter 2009
Heat Transfer Problem o Measured the electrical power dissipated o Measured the bulb surface temperature and the ambient temperature o Measured the diameter of the light bulb o Measured the thickness of the glass A SSUMPTIONS : o Near vacuum inside the light bulb o Geometry is a sphere o The radiation is a point source o Filament treated as a sphere o All electrical work converted to heat
Solution Online sources show: T = 2550 ºC T s = 95 ºC T filament = ? k nitrogen = 81 W/m ·K A s, ε q in = 96 W 60 mm Ø 0.5 mm thick Glass Vacuum T avg ρcPcP μνkαPrbeta E E E E E-03 Ø fil = σ =5.67E-08h r1 = R 1 = Ø inner =0.0595Tin =368h r2 = R 2 =7.00E-01 Ø outer =0.06T S =368h =6.56E+00R 3 = k N =2T ∞ =300Nu = R 4 = k glass =81q =96 WRa =8.34E+05R 5 = A fil = ε glass =0.95R total = without R1 A glass =2.97E-03 ε W =0.38T filament =2681K Ts =2681
Conclusions and Recommendations The temperature is between 4500 to 2500˚C. Main contributors to T filament : ◦ Surface Area of Filament ◦ Vacuum v. Conduction thru gas Measure different filament styles Verify/modify assumptions with other measurements
Appendix qid= AAlv437. Fundamentals of Heat and Mass Transfer, Incropera, 6 th Edition.
Additional Graphs Both graphs based on assumption of pure nitrogen inside bulb with no convection