ESDU 98007 describes finite element based numerical and algebraic techniques used to relate effectiveness, number of heat transfer units (NTU) and stream thermal capacity ratio to derive the data presented in ESDU 98004 and 98005 for two-stream heat exchangers in those cases for which no mathematical relationships were derived. The configurations covered included crossflow with mixed/unmixed flow, crossflow with finite numbers of tubes, shell-and-tube with finite numbers of baffles, and plate-type. ESDU 98003 introduces the effectiveness - NTU method, while ESDU 98006 presents case studies illustrating its use.