EFFECTS OF SURFACE-PROPERTIES ON RADIATIVE-TRANSFER IN A CYLINDRICAL TUBE WITH A NONPARTICIPATING MEDIUM

Radiative heat transfer inside a cylindrical tube is modeled using a s tatistical method called the discrete probability function (DPF) metho d. The DPF method involves solution of the equation of radiative heat transfer using Lagrangian simulations of representative photon traject ories on a discrete spatial grid. The DPF method is different from the Markov Chain method in terms of associating a probability with each s tate of the photon rather than a transition from one state to another. The advantages and disadvantages of the DPF method in comparison to t he Markov Chain method ale demonstrated in this paper using two practi cal applications of the cylindrical tube radiative heat transfer probl em. The cylindrical tube has a hot source at one end and a detector at the other end. The cylindrical wall absorbs and reflects (both diffus ely and specularly) the radiation incident on it. The present calculat ions have applications in: (1) intrusive pyrometry with collimating li ght guides, and (2) measurement of the spectral absorption and reflect ion coefficients of coatings using two, coated cylindrical tubes as sp ecimen. The results show that: (1) the effect of light guide surface p roperties on errors in pyrometry must he carefully assessed and (2) th e method can be used for a convenient evaluation of radiative properti es of coatings.