Overall Heat Transfer Coefficient Given Convection Coefficient Calculator

Formula Used:

\[ U_{overall} = \frac{h_{ia} \times h_{ie}}{h_{ia} + h_{ie}} \]

Overall Heat Transfer Coefficient (U_overall):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Overall Heat Transfer Coefficient?

The overall heat transfer coefficient (U) represents the total convective heat transfer between a fluid medium and the surface flowed over by the fluid. It quantifies how well heat is transferred through a system and is a crucial parameter in heat exchanger design and thermal analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ U_{overall} = \frac{h_{ia} \times h_{ie}}{h_{ia} + h_{ie}} \]

Where:

\( U_{overall} \) — Overall heat transfer coefficient (W/m²·K)
\( h_{ia} \) — Convection coefficient based on inside area (W/m²·K)
\( h_{ie} \) — Effective convection coefficient on inside (W/m²·K)

Explanation: This formula calculates the combined effect of two convection coefficients acting in series, providing the overall heat transfer capability of the system.

3. Importance of Overall Heat Transfer Coefficient

Details: The overall heat transfer coefficient is essential for designing efficient heat exchangers, calculating heat transfer rates, and optimizing thermal systems in various engineering applications including HVAC, power plants, and chemical processing.

4. Using the Calculator

Tips: Enter both convection coefficients in W/m²·K. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for convection coefficients?
A: Convection coefficients vary widely: natural convection (5-25 W/m²·K), forced convection (25-250 W/m²·K), and boiling/condensation (2500-100,000 W/m²·K).

Q2: How does this relate to thermal resistance?
A: The overall heat transfer coefficient is the reciprocal of the total thermal resistance. Lower U-values indicate better insulation, while higher U-values indicate better heat transfer.

Q3: When is this formula applicable?
A: This formula is specifically for calculating the combined effect of two convection coefficients in series without considering conduction resistance.

Q4: What are the limitations of this calculation?
A: This simplified approach assumes perfect thermal contact and doesn't account for conduction resistance through walls or fouling factors that affect real-world systems.

Q5: How is this used in heat exchanger design?
A: The overall heat transfer coefficient is fundamental in the design equation Q = U×A×ΔT, where Q is heat transfer rate, A is area, and ΔT is temperature difference.