Radiation Advanced Transport Phenomena Peter Hamersma, Faculty of - PowerPoint PPT Presentation

Radiation Advanced Transport Phenomena Peter Hamersma, Faculty of Applied Sciences

Energy loss

Energy loss Radiation Convection Conduction

Cooking

Radiator

Stefan-Boltzmann Black body: Absorbs all incoming radiation φ black = σ AT 4 with σ = 5.6710 − 8 W /( m 2 ⋅ K 4 )

Black body radiation: Parallel plates T 1 T 2

Grey body radiation: Parallel plates T 1 T 2 4 4 4 4 A T ( T ) A T ( T ) σ − σ − 1 2 1 2 φ = φ − φ = ⎛ = 4 4 A T ( T ) = σ − grey net , grey ,12 grey ,21 1 1 1 1 1 1 2 ⎞ ⎛ ⎞ 1 + − + − ⎜ ⎟ ⎜ ⎟ 1 1 e e ⎝ ⎠ ⎝ ⎠ 1 2

Radiation: Free form T 1 T 2

Radiation: Free form T 1 T 2 4 4 ( T T ) − h e 1 2 = σ radiation effective ( T T ) − 1 2

Radiation: Free form 4 4 ( T T ) − T 1 h e 1 2 = σ radiation effective ( T T ) ( T T ) − − 1 2 1 2 T 2

Example: Thermometer T wall T air T wall <T thermo h A T ( T ) φ = − convection convection air thermo T thermo h A T ( T ) φ = − radiation radiation thermo wall T thermo =T air ?

Example: Thermometer T air T wall h A T ( T ) φ = − radiation radiation thermo wall T wall <T therm h A T ( T ) φ = − o convection convection air thermo T T thermo T thermo =T air h A T ( T ) h A T ( T ) ? − = − radiation thermo wall convection air thermo 4 e T 300K = σ 3 ( T T ) T ( T T ) − ≈ − air thermo thermo wall h (T T ) 10K − = convection thermo wall (T T ) 0.5K − = air thermo e 0.05 = 2 h 6W /(m K) = ⋅ convection

Free convection & radiation

Thanks for your attention Advanced Transport Phenomena Peter Hamersma, Faculty of Applied Sciences