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HT Radiation
Heat Transfer Radiation Notes
| Question | Answer |
|---|---|
| ____; is heat transferred by electromagnetic waves. | Thermal Radiation |
| Radiation always occurs from one ____ to another and always flows from high temperature body to a lower temperature body. | Mass |
| The difference between emitted and absorbed radiation for any object is the _______ heat transfer from the object. | Net Radiation |
| Radiation is emitted at many different wavelengths, but all electromagnetic waves travel at the same _____ known as the _____. | Speed, Speed of light |
| ____: is defined as the portion of the electromagnetic spectrum from 0.1 micrometers to 100 micrometers. This includes all of the visible and infrared portion, as well as a portion of the UV spectrum | Thermal Radiation |
| Electromagnetic waves can also be viewed as collections of discrete particles of energy called ____. | Photons |
| ____: occurs from a surface to the surroundings due to oscillations of electrons near the surface and occurs from all surfaces at a finite temp. | Emission |
| ____: occurs as radiation incident to the surface (incident to the surface=striking the surface) is transformed to internal energy. | Absorption |
| ___: occurs as radiation incident to the surface is redirected away without being absorbed. | Reflection |
| ___: occurs when radiation passes through an object without being absorbed. This only occurs with transparent or semi-transparent objects. | Transmission |
| ___: is the incident radiation striking a surface which is what is reflected, absorbed, and transmitted. | Surface Irradiation (G) |
| ___: is the total radiation leaving a surface which is what is emitted and reflected. | Radiosity (J) |
| Two major difficulties associated with radiation are its ___ and ____ nature | Spectral, Directional |
| Surfaces will respond differently to irradiation depending on the distribution of _____, absorbing some and reflecting others. This is how color can be perceived. | Wavelengths |
| ____: emission and reflection are constant for all directions. | Directionally Diffuse |
| Surfaces also emit and absorb radiation to/from different directions and the magnitude depends on the ____, | Direction |
| ___: rate at which radiation is emitted at a particular wavelength and in a particular direction (per unit solid angle, per unit wavelength, per unit surface area). | Radiation Intensity (Ie) |
| Black bodies are ideal surfaces with properties (3): | 1. perfect absorber 2. perfect emitter 3. Diffuse |
| ____: black body spectral emissive power depends on wavelength and temperature. This equation shows that as the temp. increases the wavelength where the maximum black body spectral emissive power decreases. | Wien's Displacement Law |
| ___: a fraction of the total emission from a black body that occurs only in a certain wavelength. | Band-Emission |
| Even for real (non-blackbody) surfaces, radiation heat transfer depends on delta T4. We can make the following qualitative statements (2): | 1. radiation becomes more important as the temps of the participating surfaces increase. 2. radiation becomes more important as temp difference increases. It is often negligible for small delta T and dominant for large delta T. |
| Gray surfaces have no preferred _____ reflection. | Color |
| Kirchoffs Law for gray surfaces states _____. And for real surfaces states ____. | emissivity and absorptivity are equal. emissivity and absorptivity are equal at each particular wavelength and direction. |
| Kirchoffs Law ensures that for any surface radiation exchange, net heat transfer always occurs from _____. | high to low |
| ____: is defined as the fraction of the radiation leaving surface i that is intercepted (incident) to surface j. | View Factor |
| Shape factor, angle factor, and configuration factors are all different names for the ___. | View Factor |
| ____: two (or more) surfaces that possess symmetry about a third surface will have identical view factors from that surface. | Symmetry Rule |
Created by:
jrr409