Gray body radiation pdf

The radiation shields reduce the heat transfer by placing additional resistances in the path of heat flow. The radiation shields should have high reflectivity and low emissivity. The high reflectivity makes the radiation shield to reflect most of the radiation heat and thus decreases the heat transfer to the other surface.

In the same way, the lower the emissivity , the higher the resistance and the lesser the heat transfer. Answer Detailed Solution Below 13 - Concept: Emissive Power: It is the total radiant energy emitted by the body at a certain temperature per unit time and per unit surface area at all wavelengths.

Answer Detailed Solution Below Option 1 : 0. Concept: Shape Factor is defined as the fraction of radiation energy leaving a surface that reaches another surface, for example, F 12 means the fraction of energy leaving the surface 1 reaches surface 2. Conduction Convection Radiation All options are correct. Explanation: The heat from the sun or heat released from the filament of a light bulb is the example of radiation.

Radiation: In radiation, heat transfer occurs through electromagnetic waves without involving particles. The heat transfer mechanism in which no medium is required is called radiation.

It refers to the movement of heat in waves, as it does not need molecules to travel through. The object need not be in direct contact with one another to transmit heat. It is the process of heat transfer from a hot body to a cold body in a straight line without affecting the intervening medium Download Solution PDF Share on Whatsapp.

Answer Detailed Solution Below Option 3 : 0. Concept: Irradiation G : The thermal radiation falling or incident upon a surface per unit time and per unit area is called irradiation Radiosity J : The total radiation energy leaving a surface per unit time per unit area is called radiosity.

Emissive Power E : It is radiation energy leaving a surface. As temperature increases, the peak of the curve shift towards higher wavelength Spectral emissive power varies continuously with the change in wavelength At a given wavelength, as temperature increases, emissive power also increases Total emissive power is proportional to T 4.

Answer Detailed Solution Below Option 1 : As temperature increases, the peak of the curve shift towards higher wavelength. Explanation: Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. Concept: Thermal radiation is the transmission of heat in the form of radiant energy from one body to another body by the thermal motion of charged particles of matter.

The mechanism of radiation is divided into 3 phases Conversion of thermal energy of the hot source into electromagnetic waves Passage of wave motion through intervening medium Transformation of waves into heat Thermal radiation is limited to wavelengths ranging from 0. It includes some portion of UV radiation 0.

Answer Detailed Solution Below Option 4 : intensity of radiation. Irradiation G : The radiation flux incident on a surface from all directions is called irradiation G. Kiran 27 Jul 6 Answers answer.

Ayush 27 Apr a black body is an object that absorbs all the radiant energy reaching its surface from all the direction with all the with all the wavelengths. Gray body: A gray body is defined as a body whose absorptivity of a surface does not vary with variation in temperature and wavelength of the incident radiation.

Read More. View all vote's. No Down Vote. Shubham 14 Jul Black body is an object that absorbs all the radiant energy reaching its surface from all the direction while gray body is a body whose absorptivity of surface does not vary with variation in temperature and wavelength of incident radiation. No Vote. No Up Vote. When energy is incident on any body it can either absorbed,reflected.

Black body is hypothetical object that absorbs all radiations that strikes it. Biren 07 Jul a black body is an object that absorbs all the radiant energy reaching its surface from all the direction with all the with all the wavelengths. Rajat 03 Mar Black body transmitt radiation of discontinuous radiation of energy while gray body does not. Other Related Discussions. New solar energy technology for developing countries like India.

This allows the detection of warm-blooded animals and people at night. The black body radiation from animals is usually in the infrared radiation, and cannot be seen with the naked eye; however, a thermal camera can be used to see the thermal radiation from an animal. The image appears as a glowing object due to the black body radiation, unlike during the day when the person reflects the light falling on them. The hot and warmer objects emit more energetic radiation and cool faster than the cooler objects.

In the absence of a heat source, the objects will eventually reach the same temperature as the surroundings and are said to be in thermal equilibrium. The blackbody radiators for commercial applications almost approach an ideal blackbody and are used for a variety of applications.

The choice of the blackbody radiation sources depends on the temperature, type of the application and environment. The major factors considered include;. The temperature depends on the object under test. For example, a low-temperature blackbody is suitable for applications such as calibrating IR sensor that looks at buildings, vehicles, or human bodies. The blackbody radiation sources are available in three main categories, based on the temperature range.