= Consider a gas flame inside a burner unit. The gas flame is modelled as a cylinder of radius R1 = 10 mm (surface 1). The burner is surface 2 a cylinder of R2= 40 mm. Surface 1 and surface 2 are concentric cylinders with base surface 3 a disk of R3= 40 mm and surface 4 opposite to the base is open to atmosphere. Given . Determine F23. (Use view factor graphs to find respective view factors.) (4 Points) a A4 AT A2 A3