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.