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On Kirchhoff's law and its generalized application to absorption and emission by cavities

1965; The National Institute of Standards and Technology; Volume: 69B; Issue: 3 Linguagem: Inglês

10.6028/jres.069b.019

2376-5283

Francis J. Kelly,

Thermal Radiation and Cooling Technologies

Seve ra l a uthurs have ma d e th e ass umption that Kirc hh off's Law hold s fur th e apparent local s pectral e mittan ce and apparent lo ca l s pec tral absorptance of a ny point on th e int e rior s urface of a cav ity.The co rrec tn ess of thi s assumption is d e mo ns trat e d under ce rt ain genera l c unditiun s, and it s pra c ti ca l ap pli cati on to th e ca lc ul a tion of th e tot a l Aux a bso rb ed b y a cav it y or s pacec raft is di sc ussed.A furth er app li ca tion to th e case of a nuni soth e rmal cavity ur spacecra ft is d e riv ed.By thi s d e riv a ti on a n easy methud fur determining th e to tal Au x e mitt ed fru lll s uc h a noni soth e rmal cav ity is found when th e di s tribution of th e appa re nt luca l s pectral e mittance uf th e is uthermal c avity is kn ow n.T he eco nomy and versa tility of thi s methud is s hown by th e ca lc ul at ion of th e total Au x e mitt ed from a noni so lhermal cy lindri ca l cav it y for se veral a rbitra r y cases of te mpe ra ture di s tributi o n o n th e int e rior s urface o f the c avity.Finally, th e int egra l eq uation for a diffu se cav it y whose wall e mittance varies with position on th e wall is tra ns formed to an e quation havi ng a sy mm e tri c kernel.