Overall Heat Transfer Coefficient Given LMTD Calculator

Formula Used:

\[ U = \frac{Q}{f \times A \times \Delta T_m} \]

Heat Exchanged (Q):

Correction Factor (f):

Area (A):

m²

Logarithmic Mean Temperature Difference (ΔTm):

Overall Heat Transfer Coefficient (U):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Overall Heat Transfer Coefficient?

The Overall Heat Transfer Coefficient (U) represents the overall convective heat transfer between a fluid medium and the surface flowed over by the fluid. It quantifies how well heat is transferred through a series of resistances.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ U = \frac{Q}{f \times A \times \Delta T_m} \]

Where:

\( U \) — Overall Heat Transfer Coefficient (W/m²·K)
\( Q \) — Heat exchanged (W)
\( f \) — Correction Factor
\( A \) — Area (m²)
\( \Delta T_m \) — Logarithmic Mean Temperature Difference (K)

Explanation: This formula calculates the overall heat transfer coefficient based on the heat exchanged, correction factor, heat transfer area, and the logarithmic mean temperature difference.

3. Importance of Overall Heat Transfer Coefficient

Details: The overall heat transfer coefficient is crucial for designing and analyzing heat exchangers, determining heat transfer efficiency, and optimizing thermal systems in various engineering applications.

4. Using the Calculator

Tips: Enter heat exchanged in watts, correction factor (dimensionless), area in square meters, and logarithmic mean temperature difference in Kelvin. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range of U values?
A: U values vary widely depending on the fluids and materials involved, typically ranging from 5-5000 W/m²·K for different heat exchanger configurations.

Q2: Why is a correction factor needed?
A: The correction factor accounts for deviations from ideal counterflow conditions in heat exchangers with complex flow arrangements.

Q3: How does U relate to individual heat transfer coefficients?
A: The overall coefficient is related to individual coefficients through the formula: 1/U = 1/h₁ + δ/k + 1/h₂, where h are convective coefficients, δ is thickness, and k is thermal conductivity.

Q4: When should LMTD be used instead of arithmetic mean?
A: LMTD should be used when temperature differences vary significantly along the heat exchanger length, providing a more accurate representation of the driving force for heat transfer.

Q5: What factors affect the overall heat transfer coefficient?
A: U is affected by fluid properties, flow rates, surface conditions, fouling factors, and the materials used in the heat exchanger construction.