Leak detection feasibility investigation using infrared radiation transfer in absorbing, emitting, and scattering media

A radiation heat transfer model was developed to simulate the transfer of radiative energy in the infrared region 2 ≤ λ ≤ 5μm through an emitting, absorbing, and scattering plume of water vapor. The model makes use of the spectral features of the water vapor absorption coefficients to yield information on the spectral regions more sensitive to the absorption of a known background radiation source. Scattering was incorporated into the model by varying the albedo parameter from 0 to 0.9, representing all possible situations from no scattering to nearly full scattering. The radiation transport model was used to evaluate and estimate the wavelength sensitivity of infrared sensors for detection of hot and cold leak plumes. Experiments were carried out using an IR image recording and processing system to validate the results of the model. The conclusions of this investigation substantiate the use of IR thermal imaging systems to monitor cryogenic and hot gas leaks in systems such as the Space Shuttle Main Engine (SSME).