By: David Wheeler & William TryonBy: David Wheeler & William Tryon

November 30, 2011November 30, 2011

It is often necessary to know the fraction of

the total emission from a blackbody that is in a certain wavelength interval or band.

A ‘Blackbody Radiation Function’ table can be used to lookup such values to calculate the total emissive power.

The calculations to find the total emissive power are long, quite monotonous, and can introduce errors.

Our object is to make this process quicker, easier, and more accurate.

Introduction

User Friendly Accurate Intuitive (no need for instructions) Easy of Use Universal (able to use on a wide variety of

problems) Visually Appealing Quick Able to accept small changes easily, in order

to gain a better understanding of the material

Main Objectives

Calculator Layout

Define the temperature of

the diffuse surface

Define the temperature of

the diffuse surface

Define up to three

wavelengths of interest

Define up to three

wavelengths of interest

If desired, enter the spectral,

normal emissivity for the specified range

If desired, enter the spectral,

normal emissivity for the specified range

The fraction of the radiation between the

specified wavelengths

The fraction of the radiation between the

specified wavelengths

Total emissivityTotal emissivity

Total emissive power

Total emissive power

Press Run! at any time to update the calculations

Press Run! at any time to update the calculations

Press Reset to erase all entriesPress Reset to

erase all entries

A diffuse surface at 1600K has the following

spectral, hemispherical emissivity:

ε = 0.40 for 0 < λ < 2μmε = 0.80 for 2 < λ < 5μmε = 0 for λ > 5μm

Determine the total hemispherical emissivity

and the total emissive power.

Sample Problem

Enter the following

parameters:• Surface

temperature

• λ1 and λ2

• ε1 and ε2 Push Run! Viola! There’s the

answers!

Sample Problem (cont.)

We wrote a MATLAB script that interpolates

the data from Table 12.1 We then designed and programed a Graphical

User Interface (GUI) to collect the required inputs

Using the interpolated data and the collected inputs, we performed the necessary calculations

We display the fractional radiation distribution, the total emissivity, and total emissive power.

How it Works!

The program is:

User Friendly Accurate Intuitive (no need for instructions) Easy of Use Universal (able to use on a wide variety of

problems) Visually Appealing Quick Able to accept small changes easily, in order to

gain a better understanding of the material

Conclusion

Ability to increase the number of specified

wavelengths. Higher order approximation for the fraction of

the blackbody emission in a spectral band (currently we use a linear fit)

Create a Java applet to improve availability Include additional outputs, such as the

spectral intensity for the specified wavelength.

Future Work

Questions?