Number of Transfer units Define: Numberof Transfer Units, NTU NTu UA min nTU depends on both the heat exchanger design (UA) and the operating conditions(cmin) Define: Capacity Ratio, Cr r min max Effectiveness is a function of capacity ratio and the ntu E=f(NTU, Cr) Relationships between E, nTU and Cr can be computed Tables 11.3 and 11.4 and Figures 11.14-l1.9 in textbook Heat Transfer Su Yongkang School of Mechanical EngineeringHeat Transfer Su Yongkang School of Mechanical Engineering # 7 Number of Transfer Units Define: Number of Transfer Units, NTU • NTU depends on both the heat exchanger design (UA) and the operating conditions (Cmin). Define: Capacity Ratio, Cr • Effectiveness is a function of capacity ratio and the NTU • Relationships between , NTU and Cr can be computed. Tables 11.3 and 11.4 and Figures 11.14 – 11.19 in textbook C C /C (C 1) r = min max r  ( ) NTU Cr  = f , Cmin UA NTU 