... into account the nature of the two radiating surfaces; F Gis a factor that takes into account the geometric orientation of the two radiating surfaces and A 1is the area of surface 1.When a heat ... cpg, the specific heat of the gas; mw,themass of the wall of the bulb; cpw, the specific heat of the wall; h f , the heat transfer coefficientbetween the filament and the gas; hg, the heat transfer ... text.Professor Seetharamu acknowledges Professor Ahmed Yusoff Hassan, Associate Profes-sor Zainal Alimuddin and Dr Zaidi Md Ripin of the School of Mechanical Engineering,Universiti Sains Malaysia...