Quantitative ThermographyTemperature and Tantrums

Infrared – What is it?

How is it emitted?

E = hvFrequency of radiation, sometimes written as f giving expression E=hf.

Quantum energyof a photon.

H – Planck’s constant = 6.626 x 10 Joule-sec = 4.136 x 10 eV-s-34 -15

The Weird World of Infrared

What is this?

Emitted (Tg)

Reflected (Tr)

Transmitted (Tt)

The Weird World of Infrared – Part 2

AbsorbedBackground (Tb)

Gas “Cloud”

Radiation Laws

Planck’s Law The formula describing the spectral radiation of a perfect blackbody as a function of its

temperature and the wavelength of the emitted radiationWλb = 2π h c2 x 10-6 [ W/m2(µm)]

λ5 (ehc/λkT – 1)h-=Planck’s constantk=Boltzman’s contstant

Stefan-Boltzmann’s Law The formula indicates the total radiation at ALL wavelengths from a perfect blackbody

W[TOTAL] = 5.67 x 10-8 T4 [W/m2]

Convection

For horizontal pipes

WConvection = 1.35 x (Ts – Ta)0.25 / dop [ W/m2]

Ts = Absolute temperature of heat emitting surfaceTa = Absolute temperature of airdop = Outside diameter of pipe/insulation

Camera Selection

Total loss in horizontal pipework

Q = length π dop (WConvection + WRadiation)

= length x π dop x (1.35 x (Ts – Ta)0.25 / dop + 5.67 x 10-8 T4)

Examples

Examples

Examples

Quiz – How much per year?

£10,811 £33,000pa for 25mph wind

Quiz – How much

£21,500 £73,000pa for 25mph wind

Thank you for ListeningAny Questions?