📖 How to Use This Heat Exchanger Calculator
1
Enter temperatures – Hot and cold fluid inlet/outlet in °C.
2
Select flow configuration – Counter flow or parallel flow.
3
Enter Q and U – Heat transfer rate (kW) and overall coefficient (W/m²·K).
🔥 Understanding LMTD
The Log Mean Temperature Difference (LMTD) is the driving force for heat transfer. Counter flow provides higher LMTD than parallel flow.
🧮 Key Formulas
Counter Flow: ΔT₁ = Th,in - Tc,out | ΔT₂ = Th,out - Tc,in
Parallel Flow: ΔT₁ = Th,in - Tc,in | ΔT₂ = Th,out - Tc,out
LMTD = (ΔT₁ - ΔT₂) / ln(ΔT₁/ΔT₂)
Area = Q / (U × LMTD)
❓ Frequently Asked Questions
What is LMTD?
LMTD is the average temperature difference between hot and cold fluids over the heat exchanger length.
Counter vs parallel flow?
Counter flow gives higher LMTD and is more efficient than parallel flow.
What is U (overall heat transfer coefficient)?
U accounts for all thermal resistances. Typical values: 200-800 W/m²·K for liquid-liquid.