Empirical Correlations(Contd Horizontal Plate( contd Define the characteristic length, L as L P Upper surface of heated plate, or Lower surface of cooled plate: N=0.54Ra 104≤Rar≤10 0.15Ra 1/3 L 0′≤Rar≤10 Lower surface of heated plate, or Upper surface of cooled plate: Nu1=0.27Ra14(05≤Ra,≤100 Note Use fluid roperties at the pI T+t filmtemperature Heat Transfer Su Yongkang School of Mechanical EngineeringHeat Transfer Su Yongkang School of Mechanical Engineering # 6 Empirical Correlations (Cont’d) Horizontal Plate (Cont’d) • Define the characteristic length, L as • Upper surface of heated plate, or Lower surface of cooled plate : • Lower surface of heated plate, or Upper surface of cooled plate : ( ) ( ) 1/3 7 11 1/ 4 4 7 0.15 10 10 0.54 10 10 =   =   L L L L L L Nu Ra Ra Nu Ra Ra ( ) 1/ 4 5 10 NuL = 0.27 RaL 10  RaL 10 Note: Use fluid properties at the film temperature 2 +  = T T T s f P A L s 