`Q = "U" * "A" *(DeltaT_A - DeltaT_B)/(ln(DeltaT_A) - ln(DeltaT_B))`

Enter a value for all fields

The Heat Transfer using LMTD calculator computes the overall heat transfer flow rate through a heat exchanger based on the heat transfer material coefficient, transfer area and the temperature difference at the two ends of the heat exchanger using the Log Mean Termperature Difference (LMTD).

INSTRUCTIONS: Choose units and enter the following:

• (U) Heat Transfer Coefficient. units: W/(m²⋅°C)
• (A) Surface Area
• (ΔT_A)Temperature Change at Heat Exchanger End A
• (ΔT_B)Temperature Change at Heat Exchanger End B

Heat Transfer Flow Rate (Q): The energy flow rate is returned in watts (W).  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The formula for Heat Transfer using LMTD is: 

`Q = U*A *(DeltaT_A - DeltaT_B)/(ln(DeltaT_A) - ln(DeltaT_B))`

where:

• Q = Heat Energy Flow Rate, J/s = W
• U = Heat transfer coefficient, W/(m²⋅C)
• A = Heat Transfer Surface Area, m²
• ΔT_A = Temperature Change at Point A
• ΔT_B = Temperature Change at Point B

Heat Transfer Flow Rate is defined as the transfer of heat by convection or in the phase change (generally between fluid and a solid) across a medium.  The formula for Heat Transfer Flow Rate is:

`Q = U*A*LMTD`

Where,

• Q = Heat Energy Flow Rate, J/s = W
• U = Heat transfer coefficient, W/(m^2⋅C)
• A = Heat Transfer Surface Area, m²
• LMTD = Logarithmic Mean Temperature Difference

The formula for the Logarithmic Mean Temperature Difference is: 

`LMTD = (ΔT_A - ΔT_B)/(lnΔT_A - lnΔT_B)`

where:

• LMTD = Logarithmic Mean Temperature Difference
• ΔT_A = Temperature Change at Point A
• ΔT_B = Temperature Change at Point B

Heat Transfer Calculators

• Arithmetic Mean Temperature Difference (AMTD)
• Logarithmic Mean Temperature Difference (LMTD)
• Conductive Heat Transfer
• Thermal Diffusivity
• Heat Transfer Coefficient
• Heat Energy Transfer Rate
• Heat Transfer using LMTD
• Heat Exchange Area using LMTD