Logarithmic Mean Temperature Difference Calculator

Logarithmic Mean Temperature Difference Formula:

\[ \Delta T_m = \frac{Q}{A \times U_{overall}} \]

Logarithmic Mean Temperature Difference (ΔTm):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Logarithmic Mean Temperature Difference?

The Logarithmic Mean Temperature Difference (ΔTm) is used in heat exchanger design to determine the temperature driving force for heat transfer. It represents the logarithmic average of the temperature difference between the hot and cold fluids at each end of the heat exchanger.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \Delta T_m = \frac{Q}{A \times U_{overall}} \]

Where:

\( \Delta T_m \) — Logarithmic Mean Temperature Difference (K)
\( Q \) — Heat Flow Rate (Watt)
\( A \) — Heat Transfer Area (m²)
\( U_{overall} \) — Overall Heat Transfer Coefficient (W/m²·K)

Explanation: This formula calculates the mean temperature difference that would give the same heat transfer rate as the actual temperature difference in a heat exchanger.

3. Importance of ΔTm Calculation

Details: Accurate ΔTm calculation is crucial for heat exchanger design, performance analysis, and determining the required heat transfer area for a given thermal duty.

4. Using the Calculator

Tips: Enter heat flow rate in watts, area in square meters, and overall heat transfer coefficient in W/m²·K. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: When is LMTD method used?
A: The LMTD method is used for heat exchanger design and analysis when the inlet and outlet temperatures of both fluids are known or can be determined.

Q2: What are the limitations of LMTD method?
A: The LMTD method assumes constant physical properties, constant overall heat transfer coefficient, and no phase change in the heat exchanger.

Q3: How does LMTD differ from arithmetic mean temperature difference?
A: LMTD provides a more accurate representation of the driving force for heat transfer, especially when temperature differences vary significantly along the heat exchanger length.

Q4: What types of heat exchangers use LMTD?
A: LMTD is commonly used for parallel-flow, counter-flow, and cross-flow heat exchangers with appropriate correction factors.

Q5: When should correction factors be applied to LMTD?
A: Correction factors are needed for multi-pass and cross-flow heat exchangers where the flow arrangement is not purely parallel or counter flow.