Describe the NTU-effectiveness method and its advantages over LMTD.

The NTU-effectiveness method uses Number of Transfer Units (NTU = UA/C_min) and heat capacity ratio (C_r = C_min/C_max) to determine effectiveness (ε = Q_actual/Q_max). Effectiveness relations depend on heat exchanger configuration. For counterflow: ε = [1-exp(-NTU(1-C_r))]/[1-C_r×exp(-NTU(1-C_r))]. Advantages: works when only inlet temperatures are known (rating problem), handles any exchanger configuration through effectiveness-NTU charts, directly gives performance metrics. LMTD requires iterative solutions when outlets are unknown, making NTU method more practical for rating existing exchangers.