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This quiz contains multiple-choice problems on the concepts of fins, steady heat flow along a rod, performance of fins, design consideration for fins, thermometric well properties and heat dissipation from a long fin and a fin that is insulated at the tip.
The extended surface used for the enhancement of heat dissipation is
In order to achieve maximum heat dissipation, the fin should be designed in such a way that has a
On a heat transfer surface, fins are provided to
The thermometric well is treated as a fin of
The relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures are
α = α{1}, at x = 0, and α = α{2}, at x = infinity
α = α{1}, at x = 1, and α = α{2}, at x = 2L
α = α{1}, at x = infinity, and α = α{2}, at x = 1
α = α{1}, at x = 0, and α = α{2}, at x = L
A long copper rod 20 mm in diameter extends horizontally from a heated plane wall maintained at 100 °C. The rod’s surface is exposed to an environment at 20 °C with a convective heat transfer coefficient of 8.5 W/m^2 degrees. Determine the heat loss if the thermal conductivity of copper is 400 W/m degree.
10.71 W
20.71 W
30.71 W
40.71 W
Typical applications of finned surfaces are with
(i) Electrical motors
(ii) Economizers for steam power plant
(iii) Convectors for steam and cold water heating systems
(iv) Cooling coils
Identify the correct option.
i, ii and iv
i, ii and iii
i, ii, iii and iv
i and ii
It is said that fins can take a variety of forms
(i) Longitudinal fins of rectangular cross-section attached to a wall
(ii) Cylindrical tubes with radial fins
(iii) Conical rod protruding from a wall
Identify the correct statement.
i only
i and ii
ii and iii
i, ii and iii
If the fin is sufficiently thin, the heat flow pertains to
One-dimensional heat conduction
Two-dimensional heat conduction
Three-dimensional heat conduction
No heat flow is there
If heat dissipation for one fin is given by 377.45 k J/hour, what is the heat dissipation for 12 fins?
7529.4 k J/hour
6529.4 k J/hour
5529.4 k J/hour
4529.4 k J/hour
What purpose do thermometric wells serve?
They measure current
They measure resistance
They measure temperature of gas
They stop heat dissipation
Thermometric well apparatus does not include
Thermometer
Pipe line
Oil
Ammeter
The convective coefficient in boilers and condensers is
Low
High
Moderate
Depends on time and temperature
A steel rod (k = 30 W/m degree) of diameter 1 cm and length 5 cm protrudes from a wall maintained at a temperature of 10 °C. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m^2 degree and t{a} = 30 °C. Calculate the heat dissipation rate.
2.658 W
3.658 W
4.658 W
5.658 W
A steel rod (k = 30 W/m degree) of diameter 1 cm and length 5 cm protrudes from a wall maintained at a temperature of 10 °C. The rod is insulated at its tip and is exposed to an environment with h = 50 W/m^2 degree and t{a} = 30 °C. Calculate the fin’s efficiency.
56.57%
66.57%
76.57%
86.57%
