Heat Transfer Coefficient Due To Radiation For Horizontal Tubes Calculator

Heat Transfer Coefficient by Radiation Formula:

\[ h_r = [Stefan-BoltZ] \times \varepsilon \times \frac{(T_{wa}^4 - T_s^4)}{(T_{wa} - T_s)} \]

Heat Transfer Coefficient (h_r):

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1. What is Heat Transfer Coefficient by Radiation?

The Heat Transfer Coefficient by Radiation quantifies the rate of heat transfer through electromagnetic radiation between surfaces. It's particularly important for horizontal tubes where radiation plays a significant role in heat exchange processes.

2. How Does the Calculator Work?

The calculator uses the radiation heat transfer formula:

\[ h_r = [Stefan-BoltZ] \times \varepsilon \times \frac{(T_{wa}^4 - T_s^4)}{(T_{wa} - T_s)} \]

Where:

\( [Stefan-BoltZ] \) — Stefan-Boltzmann Constant (5.670367×10⁻⁸ W/m²·K⁴)
\( \varepsilon \) — Emissivity (0 to 1)
\( T_{wa} \) — Wall Temperature (K)
\( T_s \) — Saturation Temperature (K)

Explanation: The formula calculates the radiative heat transfer coefficient based on temperature difference and material emissivity properties.

3. Importance of Radiation Heat Transfer

Details: Radiation heat transfer is crucial in various engineering applications including heat exchangers, boilers, furnaces, and thermal insulation systems for horizontal tube configurations.

4. Using the Calculator

Tips: Enter emissivity (0-1), wall temperature in Kelvin, and saturation temperature in Kelvin. Ensure temperatures are positive values and wall temperature differs from saturation temperature.

5. Frequently Asked Questions (FAQ)

Q1: What is emissivity and how is it determined?
A: Emissivity is a material's effectiveness in emitting thermal radiation. It ranges from 0 (perfect reflector) to 1 (perfect blackbody). Typical values are 0.8-0.95 for most surfaces.

Q2: Why use Kelvin temperature scale?
A: The Stefan-Boltzmann law requires absolute temperature (Kelvin) since it involves temperature to the fourth power.

Q3: What are typical values for radiation heat transfer coefficient?
A: Values typically range from 5-25 W/m²·K for moderate temperature differences, but can be higher for large temperature differences.

Q4: When is radiation heat transfer significant?
A: Radiation becomes increasingly important at higher temperatures and in vacuum environments where convection is limited.

Q5: How does tube orientation affect radiation heat transfer?
A: Horizontal tube orientation affects view factors and radiation exchange patterns with surrounding surfaces, influencing the overall heat transfer rate.