Mass transfer model of halogen doped incandescent lamps with application to the W-O-Br system
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A m a s s t r a n s f e r m o d e l of halogen doped i n c a n d e s c e n t l a m p s i s f o r m u l a t e d . In t h i s m o d e l , the t r a n s p o r t p r o c e s s e s o c c u r r i n g in t h e s e l a m p s a r e r e p r e s e n t e d by diffusion and counter d i f f u s i o n of g a s e o u s s p e c i e s a c r o s s the s t a g n a n t b o u n d a r y l a y e r s u r r o u n d i n g the f i l a m e n t with s i m u l t a n e o u s r e a c t i o n s at the bulb w a l l and t h e f i l a m e n t . The m o d e l i s a p p l i e d to t h e 500 w a t t - 1 2 0 v o t t - T 3 q u a r t z h a l o g e n l a m p g e o m e t r y in which the i n i t i a l g a s p h a s e is a r g o n with s m a l l c o n c e n t r a t i o n s of oxygen and b r o m i n e . The tungsten flux f r o m w a l l to f i l a m e n t and v i c e v e r s a and, thus, the conditions of w a l l b l a c k e n i n g a r e c a l c u l a t e d a s a function of the i n i t i a l b r o m i n e and oxygen content, f i l a m e n t and w a l l t e m p e r a t u r e , t o t a l p r e s s u r e and w a l l condensate, i . e . , W(s), WO2(s), and WO3(s). A n u m b e r of t h e r m o c h e m i c a l a n a l y s e s have b e e n p e r f o r m e d on the m u R i t u d e of r e a c t i o n s that can o c c u r in h a l o g e n - d o p e d i n c a n d e s c e n t l a m p s . 1-S T h e s e a n a l y s e s have p r o v i d e d i m p o r t a n t i n s i g h t s into the c o n d i t i o n s of f a v o r a b l e t u n g s t e n t r a n s p o r t , the t u n g s t e n t r a n s p o r t i n g s p e c i e s , and the r o l e of c o m m o n l a m p i m p u r i t i e s such a s c a r b o n , oxygen, and h y d r o g e n . Howe v e r , t h e s e a n a l y s e s cannot t a k e the following into a c c o u n t : 1) in a c t u a l h a l o g e n doped l a m p s , the i n i t i a l c o n c e n t r a t i o n s of g a s e o u s s p e c i e s a r e p a r t i t i o n e d b e t w e e n s i m u l t a n e o u s r e a c t i o n s at both the bulb w a l l and t h e f i l a m e n t a s w e l l a s to the i n t e r v e n i n g c o n c e n t r a t i o n g r a d i e n t s , and 2) l o c a l e q u i l i b r i u m at the bulb w a l l might not o c c u r b e c a u s e of a slow s u r f a c e r e a c t i o n . In addition, the m a g n i t u d e of the t u n g s t e n flux f r o m f i l a m e n t to w a l l and v i c e v e r s a cannot be c a l c u l a t e d by t h e r m o c h e m i c a l a n a l y s i s . Since t h e s e t h r e e i m p o r t a n t f e a t u r e s of the c y c l i c p r o c e s s e s t h a t o c c u r in h a l o g e n doped i n c a n d e s c e n t l a m p s can only b e obt a i n e d by k i n e t i c a n a l y s i s , a m a s s t r a n s f e r m o d e l of h a l o g e n doped l a m p s would b e d e s i r a b l e . In the p r e s e n t p a p e r , a m a s s t r a n s f e r m o d e l of h a l o gen doped i n c a n d e s c e n t l a m p s is f o r m u l a t e d . T h e m o d e l i s a p p l i e d to the 500 w a t t - 1 2 0 v o l t - T 3 q u a r t z h a l o g e n l a m p g e o
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