Heat Transfer LMTD

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.

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