Radiation Heat Transfer Coefficient Calculator

Radiation Heat Transfer Coefficient Formula:

\[ h_r = \frac{[\text{Stefan-BoltZ}] \times \varepsilon \times (T_w^4 - T_{\text{Sat}}^4)}{T_w - T_{\text{Sat}}} \]

Radiation Heat Transfer Coefficient (h_r):

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1. What is Radiation Heat Transfer Coefficient?

The Radiation Heat Transfer Coefficient quantifies the heat transferred per unit area per kelvin due to thermal radiation. It represents the area over which the transfer of heat takes place and is particularly important in systems where radiative heat transfer is significant.

2. How Does the Calculator Work?

The calculator uses the radiation heat transfer formula:

\[ h_r = \frac{[\text{Stefan-BoltZ}] \times \varepsilon \times (T_w^4 - T_{\text{Sat}}^4)}{T_w - T_{\text{Sat}}} \]

Where:

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

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

3. Importance of Radiation Heat Transfer

Details: Radiation heat transfer plays a crucial role in various engineering applications including thermal systems, electronic cooling, building design, and aerospace engineering where convective heat transfer may be limited.

4. Using the Calculator

Tips: Enter emissivity value between 0-1, plate surface temperature and saturation temperature in Kelvin. Ensure temperatures are positive values and plate temperature is different from saturation temperature.

5. Frequently Asked Questions (FAQ)

Q1: What is emissivity and how is it determined?
A: Emissivity is the ability of a surface to emit thermal radiation relative to a perfect black body. It ranges from 0 (perfect reflector) to 1 (perfect emitter). Values are typically determined experimentally or from material property tables.

Q2: Why use Kelvin temperature scale?
A: The Stefan-Boltzmann law requires absolute temperature (Kelvin) since it involves temperature to the fourth power, and Kelvin is an absolute scale starting from absolute zero.

Q3: When is radiation heat transfer significant?
A: Radiation becomes significant at high temperatures, in vacuum environments, or when dealing with surfaces with high emissivity. It's often the dominant mode of heat transfer in space applications.

Q4: What are typical emissivity values?
A: Most surfaces have emissivity between 0.7-0.95. Polished metals have lower values (0.02-0.2), while oxidized surfaces and non-metals have higher values (0.8-0.95).

Q5: How does this differ from convective heat transfer?
A: Radiation doesn't require a medium and can occur through vacuum, while convection requires fluid movement. Radiation depends on temperature to the fourth power, making it increasingly important at higher temperatures.