BENG3 THERMAL & FLUIDS ENGINEERING (THER305)
TUTORIAL EXAMPLES in RADIATION HEAT TRANSFER
1.
A gas turbine has an annular combustion
chamber with surface area 1.5 m², surface temperature 597°C and emissivity
0.18. The engine is run in a large test house with wall temperature 12°C.
Calculate the radiation heat transfer rate. [8.67kW]
2.
A radiant heater that may be considered a
black body has an area of 0.15 m². A grey surface of area 0.1 m² and emissivity
0.8 is 6 m away at 45° to the radiant surface, and parallel to it. It absorbs
2.93 W. Find the normal intensity of radiation from the heater, the rate of
energy emission from the heater and the temperature of the heater. [17.58 kW/m² ster, 8.28 kW, 993 K]
3.
Show
that the geometric factor for a small disc of area dA, and a large disc of
radius R placed parallel to and concentric with the small disc 1ocated a
distance L above the small disc is:
4.
What is the radiation heat transfer rate
per unit length to an oxidised nickel tube 0.1 m outer diameter at 700 K
enclosed in a silica brick chamber at 1255 K?
(i) when the chamber is large [19.96 kW/m]
(ii) when the chamber is 0.2 m diameter [18.79
kW/m]
(iii) when the chamber just fits over the tube. [17.74 kW/m]
For oxidised nickel and silica brick treated as grey bodies the emissivity is
0.5 and 0.8 respectively.
5.
Two very large parallel plane with emissivities
0.3 and 0.8 exchange heat. Find the percentage reduction in heat transfer when
a radiation shield of emissivity 0.04 is placed between them. [93.2%]
6.
Two parallel planes are separated by a
distance of 0.8 m. One plane is at 600°C and has an emissivity of 0.6 and the
other plane is insulated. The planes are 1 m by 0.8 m and are placed in a large
room at 15°C. Calculate the temperature of the insulated plane and the rate of
energy loss by the heated plane. Use the chart below to find the form factors. [271°C.
15.1 kW] The solution is shown on 2 pages: Page1 Page 2