Marks 1
The emissive power of a blackbody is $$P.$$ If its absolute temperature is doubled, the emissive power becomes
Consider the radiation heat exchange inside an annulus between two very long concentric cylinders. The radius of the outer cylinder is $${R_0}$$ and t...
For an opaque surface, the absorptivity $$\left( \alpha \right),$$ transmissivity $$\left( \tau \right)$$ and reflectivity $$\left( \rho \right)$$ ...
The following figure was generated from experimental data relating spectral black body emissive power to wave length at three temperatures $${T_1},{T_...
A plate having $$10\,\,c{m^2}$$ area each side is hanging in the middle of a room of $$100\,\,{m^2}$$ total surface area. The plate temperature and em...
The shape factors with themselves of two infinitely long black body concentric cylinders with a dia ratio of $$3$$ are ....... For the inner and ........
A diffuse radiation surface has
For a glass plate transitivity and reflectivity are specified as $$0.86$$ and $$0.08$$ respectively, the absorptivity of the glass plate is
Marks 2
Two black surfaces, $$AB$$ and $$BC,$$ of lengths $$5m$$ and $$6m,$$ respectively, are oriented as shown. Both surfaces extend infinitely into the thi...
Two large parallel plates having a gap of $$10$$ $$mm$$ in between them are maintained at temperatures $${T_1} = 1000\,\,K$$ and $${T_2} = 400\,\,K$$ ...
An infinitely long furnace of $$0.5m \times 0.4m$$ cross-section is shown in the figure below. Consider all surfaces of the furnace to be black. The t...
A solid sphere $$1$$ of radius $$'r'$$ is placed inside a hollow, closed hemispherical surface $$2$$ of radius $$'4r'.$$ The shape factor $${F_{2 - 1}...
The total emissive power of a surface is $$500$$ $$W/{m^2}$$ at a temperature $${T_1}$$ and $$1200$$ $$W/{m^2}$$ at a
temperature $${T_2}$$, where the...
Two infinite parallel plates are placed at a certain distance apart. An infinite radiation shield is inserted between the plates without touching any ...
A hemispherical furnace of $$1$$ $$m$$ radius has the inner surface (emissivity, $$\varepsilon = 1$$) of its roof maintained at $$800K,$$ while its f...
A solid sphere of radius$${r_1} = 20\,\,mm$$ is placed concentrically inside a hollow sphere of radius $${r_2} = 30\,\,mm$$ as shown in the figure.
...
Two large diffuse gray parallel plates, separated by a small distance, have surface temperatures of $$400$$ $$K$$ and $$300$$ $$K.$$ If the emissiviti...
Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If $${D_1}$$ and $${D_2}$$ are the diameters of t...
Radiative heat transfer is intended between the inner surfaces of two very largen isothermal parallel metal plates. While the upper plate (designated ...
Radiative heat transfer is intended between the inner surfaces of two very largen isothermal parallel metal plates. While the upper plate (designated ...
A hollow enclosure is formed between two infinitely concentric cylinders of radii $$1m$$ and $$2m$$ respectively. Radiative heat exchange takes place ...
A solid cylinder (surface $$2$$) is located at the center of a hollow sphere (surface $$1$$). The diameter of the sphere is $$1m,$$ while the cylinder...
What is the value of the view factor for two inclined flat plates having common edge of equal width, and with an angle of $$20$$ degrees?
For the circular tube of equal length and diameter shown in fig below, the view factor $${F_{13}}$$ is $$0.17.$$ The view factor $${F_{12}}$$ in this...
The radiative heat transfer rate per unit area $$\left( {W/{m^2}} \right)$$ between two plane parallel gray surfaces (emissivity $$=0.9$$) maintained ...
Marks 5
A thin metal plate is exposed to solar radiation. The air and the surroundings are at $${30^ \circ }C\,.$$ The heat transfer coefficient by free conve...
Consider two large parallel plates, one at $${T_1} = {727^ \circ }C$$ with emissivity $${\varepsilon _1} = 0.8$$ and the other at $${T_2} = {227^ \cir...
An object has the shape of cubical box of side $$10cm,$$ with no top cover. The box is placed inside a room whose dimensions are much larger than thos...
Two black plates, each one meter square, are placed parallel to each other in such a way that the radiation shape factor for the system is $$0.4.$$ If...