Log Mean Temperature Difference Calculator

Enter value and click on calculate. Result will be displayed.


T1 = Hot Stream Inlet Temperature
T2 = Hot Stream Outlet Temperature
t1 = Cold Stream Inlet Temperature
t2 = Cold Stream Outlet Temperature

Hot Stream Inlet Temperature (T1):
°F
Hot Stream Outlet Temperature (T2):
°F
Cold Stream Inlet Temperature (t1):
°F
Cold Stream Outlet Temperature (t2):
°F
Log Mean Temperature Difference (LMTD):
°F

What is a Log Mean Temperature Difference (LMTD) Calculator?
A Log Mean Temperature Difference (LMTD) calculator is a tool used to determine the average temperature difference between two fluids exchanging heat in a heat exchanger — like in condensers, boilers, and radiators. LMTD provides a more accurate measurement when temperatures change along the heat exchanger’s length.

The LMTD formula is:

Where:

  • ΔT1 = Temperature difference at one end of the exchanger
  • ΔT2 = Temperature difference at the other end

Why use an LMTD Calculator?

  • Accurate heat transfer calculation: Accounts for changing temperature differences along the exchanger.
  • Design efficiency: Helps size heat exchangers by ensuring the right surface area and flow rates.
  • Performance evaluation: Checks if the heat exchanger is working efficiently.
  • Saves time: Automates a complex formula and reduces calculation errors.

How does it work?

  1. Input hot fluid temperatures: Inlet and outlet temperatures (Th1 and Th2).
  2. Input cold fluid temperatures: Inlet and outlet temperatures (Tc1 and Tc2).
  3. Calculate temperature differences: ΔT1=Th1−Tc1,ΔT2=Th2−Tc2
  4. Apply the LMTD formula: Calculate the log mean temperature difference.
  5. Use the result: Apply LMTD in the heat transfer equation Q=UA⋅LMTD, where is heat transfer rate, is heat transfer coefficient, and A is surface area.

When do you use it?

  • Designing heat exchangers: To ensure the right heat transfer capacity.
  • Analyzing system performance: Checking efficiency in HVAC systems, boilers, and radiators.
  • Optimizing industrial processes: In power plants, refineries, and chemical production.
  • Research and engineering: For heat transfer studies and experiments.