enter flow on both sides、temperature and heat-transfer coefficient，by log-mean temperature difference(LMTD)estimate heat duty and required heat-transfer area。applicable to air-air、gas-water、water-initial selection of water and plate heat-exchange equipment。
formula：heat duty Q = mass flow × cp ×(hot in−hot out) (kW)；cold out = cold in + Q÷(cold flow×cp)；
LMTD = (ΔT₁−ΔT₂)÷ln(ΔT₁/ΔT₂)；area A = Q×1000 ÷(U×LMTD)。U including fouling，in practice leave 10–20% margin and verify pressure drop。