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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
- (ΔTA)Temperature Change at Heat Exchanger End A
- (ΔTB)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
- ΔTA = Temperature Change at Point A
- ΔTB = 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/(m2⋅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
- ΔTA = Temperature Change at Point A
- ΔTB = Temperature Change at Point B
