# How to compute view factors between two surfaces

 Given a geometry, how do I compute the view factors without using DO model?For a given geometry, suppose, we have Surfaces 1, 2, ...We want the view factor between 1 and 2: F12. * Turn on Radiation->DO. You might want to increase accuracy by increasing the pixellization. Set the DO iteration frequency to 1. * set the emissivity of all walls to 1.0 * Set the temperature of all walls to ZERO, with the exception for T1 which you can set to any number (300 will work). * Under Solve->Controls->Limits, set the limit of Temperature to ZERO for its lower bound. * Solve the problem to convergence. * Get the radiation heat flux from Surface 2 with Solve->Reports->Radiation Heat flux. Call this Q2. * Get the surface area of wall 1 using Surface integrals->Area. Call this A1. Then, F12 = Q2 / (sigma A1 T1^4) Sigma = 5.67 e-8 W/(m^2 - K^4) The following method gave me agreement to the analytical formula within 1 part in a thousand.

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