Heat Transfer MCQ’s – Steady Flow of Heat Along a Rod

1 - Question

Which one is true regarding rectangular fin?
a) A C = b δ and P = 2(b + δ)
b) A C = 2 b δ and P = 2(b + δ)
c) A C = 3 b δ and P = 2(b + δ)
d) A C = 4 b δ and P = 2(b + δ)
View Answer Answer: a
Explanation: For rectangle, A = (length) (breadth). Where, b = width and δ = thickness.



2 - Question

Analysis of heat flow from the finned surface is made with the following assumptions (i) Uniform heat transfer coefficient, h over the entire fin surface (ii) No heat generation within the fin generation (iii) Homogenous material Identify the correct option
a) i only
b) i and ii only
c) i, ii and iii
d) ii only
View Answer Answer: c
Explanation: The knowledge of temperature distribution is necessary for their optimum design with regard to size and weight.



3 - Question

If heat conducted into the element at plane x is Q X = – k A C (d t/d x) X. Then heat conducted out of the element at plane (x + d x) is
a) – 2k A C d/d x (t + d t/d x (d x))
b) – k A C d/d x (t + d t/d x (d x))
c) – 3k A C d/d x (t + d t/d x (d x))
d) – 4k A C d/d x (t + d t/d x (d x))
View Answer Answer: b
Explanation: Heat conducted out of the element is – [k A C (d t/d x) X + d x].



4 - Question

A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m2 K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube without fin
a) 98.44 W
b) 88.44 W
c) 78.44 W
d) 68.44 W
View Answer Answer: a
Explanation: Q = h A d t = h (π d 0 H) (t 0 – t INFINITY).



5 - Question

The general solution of linear and homogenous differential equation (second form) is of the form
a) γ = C 1 e 2 m x + C 2 e – m x
b) γ = C 1 e 3m x + C 2 e – m x
c) γ = C 1 e 4 m x + C 2 e – m x
d) γ = C 1 e m x + C 2 e – m x
View Answer Answer: d
Explanation: It should contain m x and – m x term.



6 - Question

For steady flow of heat along a rod, the general equation is d2α/dx 2 – m 2 α = 0 The value of constant m is
a) (h P/k A C)
b) (h P/k A C) 3/2
c) (h P/k A C) 1/2
d) (h P/k A C) 2
View Answer Answer: c
Explanation: This provides a general form of the energy equation for one dimensional heat flow.



7 - Question

In convection from the tip, we introduced a factor known as
a) Fin length
b) Correction length
c) No fin length
d) Radial length
View Answer Answer: b
Explanation: Just for simplicity we replace fin length by correction length.



8 - Question

Find the value of corrected length for rectangular fin? Where, b is width and t is length of the fin
a) L C = L + b t/2 (b + t)
b) L C = L + b t/ (b + t)
c) L C = L + 2 (b + t)
d) L C = L + b t
View Answer Answer: a
Explanation: For rectangle, area = t b.



9 - Question

Which one is true for the spine?
a) A C = π d 2/4 and P = 4 π d
b) A C = π d 2/4 and P = 3 π d
c) A C = π d 2/4 and P = π d
d) A C = π d 2/4 and P = 2 π d
View Answer Answer: c
Explanation: A spine is a pin fin.



10 - Question

In convection from the tip what is the value of correction length?
a) L C = A C/P
b) L C = L + A C
c) L C = L + P
d) L C = L + A C/P
View Answer Answer: d
Explanation: It should contain all the three terms i.e. L, A and P.

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