Radiation Between Two Gray Surfaces Attic

3 1 radiation between two gray surfaces consider the attic of a home located in a hot climate.

Radiation between two gray surfaces attic.

In this article we will discuss about the mechanism of heat exchange between two or more surfaces. Recall that blackbodies are surfaces that absorb as much thermal radiation as the laws of physics allow. The elementary areas are at a distance r apart and the normal to these areas make angles 0 1 and 0 2 with the line joining them. Consider heat exchange between elementary areas da 1 and da 2 of two black radiating bodies having areas a 1 and a 2 respectively.

A gray surface should emit as much as radiation as the real surface it represents at the same temperature. 4 0 t t e t d t b σ ε λ ε λ λ emissivity is a strong function of temperature see fig. The portion of radiation exchanged between two differently oriented surfaces has to be defined by a geometric function known as view factor which is developed for gray diffusely radiating surfaces. A gray surface or graybody is a surface that reflects absorbs a given fraction of the thermal radiation a blackbody surface would absorb.

In general for any two objects in space a given object 1 radiates to object 2 and to other places as well as shown in figure 19 10. 4 radiation heat transfer between black surfaces of arbitrary geometry. Heat transfer between surfaces based on two assumptions. Surface and the medium between the surfaces does not absorb emit or scatter radiation.

Introduce the topic of radiation transfer in a participating medium that absorbs emits and scatters radiation and describe the formulation and application of the radiative transport equation. More importantly the graybody blackbody fraction is independent of radiation wavelength. Heat exchange between black bodies. The floor of the attic is characterized by a width of l1 10 m while the roof makes an angle of 30 from the horizontal direction as shown in the schematic.

That is it will be the case when the surfaces are isothermal and diffuse emitters and reflectors and the surfaces are separated by a non participating medium such as a vacuum or air. Describe radiation exchange among surfaces in which the surfaces can be perfect absorbers of radiation black or diffusely absorbing gray. Radiation analysis of such enclosures becomes very complicated unless some simplifying assumptions are made. Absorptivity reflectivity and transmissivity the radiation energy incident on a surface per unit area per.

The house is 30 m long ls not shown into the page. The view factor f 1 2 between two surfaces a 1 and a 2 can be.