Thermal conductivity of liquid metals and alloys

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B. C. MATHUR

The t h e r m a l conductivity data of liquid m e t a l s have b e e n c o r r e l a t e d b a s e d on the c e l l t h e o r y of l i q u i d s . The t e m p e r a t u r e dependence of t h e r m a l conductivity is p r e d i c t e d in the c a s e of t h i r t e e n m e t a l s for which e x p e r i m e n t a l data a r e a v a i l a b l e . The o v e r a l l a v e r a g e absolute d e v i a t i o n of p r e d i c t e d v a l u e s is 4.25 pct. The method has b e e n extended to a l l o y s .

LIQUID

m e t a l s make good heat t r a n s f e r m e d i a b e c a u s e of t h e i r h i g h heat c a p a c i t y , good t h e r m a l c o n d u c t i o n , and high heat t r a n s f e r c o e f f i c i e n t s . The vapor p r e s s u r e of liquid m e t a l s b e i n g v e r y low allows heat t r a n s f e r o p e r a t i o n s to be c a r r i e d out at n o r m a l p r e s s u r e s even at high t e m p e r a t u r e s . The p r e d i c t i o n of heat t r a n s f e r c o e f f i c i e n t s is far f r o m s a t i s f a c t o r y b e c a u s e of the tack of data and d i s c r e p a n c i e s in the a v a i l a b l e data. T h e r e has been so far no s y s t e m a t i c a n a l y s i s of the data and p r a c t i c a l l y no method to p r e d i c t t h e r m a l c o n duetivity of liquid m e t a l s except the c o r r e l a t i o n of Ewing 1 et al. L i t e r a t u r e s u r v e y shows that work on the c o r r e l a t i o n of t h e r m a l conductivity of liquid m e t a l s s t a r t e d as e a r l y as 1920. Rao 2 has shown that the d e c r e a s e in t h e r m a l conductivity of liquid m e t a l s o b s e r v e d n e a r the m e l t i n g point could be explained on the a s s u m p t i o n that the f r e q u e n c y of v i b r a t i o n of m o l e c u l e s c h a n g e s n e a r the m e l t i n g point. He a t t r i b u t e s the d e c r e a s e in t h e r m a l c o n d u c t i v i t y in the liquid phase to the d i s o r d e r e d state in the liquid. P o w e l l 3 has c o m p i l e d and d i s c u s s e d the work of Konno, 4 Bidwell, s and Brown. 6 As the c o e f f i c i e n t s of t h e r m a l conductivity of g a s e s and liquid alloys of m e t a l s a r e of the s a m e o r d e r of m a g n i t u d e , it can be concluded that the m e c h a n i s m s of heat t r a n s f e r in liquid alloys and g a s e s a r e s i m i l a r . Ewing 1 el al. have given a g e n e r a l c o r r e l a t i o n for m e t a l s - s o l i d , liquid, and alloys b a s e d on the concept of e l e c t r o n i c and m o l e c u l a r conduction, a r e l a t i o n s i m i l a r to W i e d e m a n n - F r a n z r e l a t i o n . T h i s r e l a t i o n as s t a t e d by the a u t h o r s p r e d i c t s t h e r m a l conductivity of liquid m e t a l s with • pet d e v i a t i o n . T h e i r r e l a t i o n is K = 2.61 x 10 -8 ( r / p )

- 2 x 10 -'7 ( T / p ) 2 / C p d

+ 97 Cp(d)2/MT

[1]

The u s e of hole theory of liquids in obtaining a s a t i s f a c t o r y c o r r e l a t i o n for t h e r m a l conductivity