1. Heat duty: Q = ṁ · cp · ΔT on each side, where ṁ is the mass flow (kg/s), cp the specific heat (kJ/kg·K) and ΔT the temperature change. The hot-side and cold-side duties should match — the average is used for area sizing.
2. LMTD: for counter-current flow, LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂), where ΔT₁ = T_h,in − T_c,out and ΔT₂ = T_h,out − T_c,in. Co-current arrangements swap the cold-side temperatures.
3. Required area: A = Q / (U · LMTD), then multiplied by (1 + fouling margin) to allow for fouling resistance and future performance loss.
4. U-value: the overall heat-transfer coefficient depends on the exchanger construction and the two fluids. Presets above cover the most common water, glycol, oil and steam duties; enter a custom value for gases, refrigerants or two-phase services.

For plate exchangers, the area translates into plate count once a plate model and effective area per plate are chosen. For shell-and-tube, area maps to tube length × tube count × outer diameter × π. Both steps require rating software and are best handled by an engineering team — use the button above to send your data for a formal quotation.

Want to learn more? Read our guides on types of heat exchangers, water-to-water heat exchangers, and plate and frame design.