# Heat Transfer Questions and Answers – Buckingham’s Pi- Method

This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Buckingham’s Pi- Method”.

1. If there are n variables in a dimensionally homogeneous equation and if these variables contain m primary dimensions, then the variables can be grouped into how many non-dimensional parameters?
a) m
b) n-m
c) n-2m
d) n

Explanation: The non-dimensional groups are called pi-terms. If there are n variables in a dimensionally homogenous equation and if these variables contain m primary dimensions, then the variables can be grouped into (n – m) non dimensional parameters.

2. Which of the following is not known as a core group?
a) Time
b) Geometric property
c) Fluid property
d) Flow characteristics

Explanation: These are also known as repeated variables.

3. What is the dimension of resistance?
a) M L T 2
b) M L T
c) M L T -2
d) M L T -1

Explanation: Unit of resistance is N. Resistance is the stopping effect exerted by one material thing to another.

4. The resistance R experienced by a partially submerged body depends upon the velocity V, length of the body l, viscosity of the fluid µ, density of the fluid p and gravitational acceleration g. Establish a relation between involving non-dimensional groups
a) R = p V l 2 function [p V l/ µ, V/ (lg) 1/2].
b) R = p l 2 function [p V l/ µ, V/ (lg) 1/2].
c) R = V 2 l 2 function [p V l/ µ, V/ (lg) 1/2].
d) R = p V 2 l function [p V l/ µ, V/ (lg) 1/2].

Explanation: This can be solved by Buckingham pi theorem.

5. If there are 6 physical quantities and 3 fundamental units, then the number of pi terms are
a) 1
b) 2
c) 3
d) 4

Explanation: It should be 6-3 = 3.
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6. The study of predicting prototype conditions from model observations is known as
a) Similitude
b) Geometrical similarity
c) Prototype
d) Model

Explanation: It prescribes the relationship between a full scale flow and a flow involving smaller but geometrically similar boundaries.

7. S.I unit of heat is
a) J
b) W
c) J s
d) W/K

Explanation: Its unit is Joule. Heat is a form of energy that can be transferred between two objects.

8. S.I unit of the coefficient of volumetric expansion is
a) Degree
b) Per meter
c) Per second
d) Per degree

Explanation: Its unit is per degree. Coefficient of volumetric expansion is defined as increase in volume.

9. S.I unit of specific heat is
a) K kg/J
b) kg/K
c) k J/kg K
d) J/K

Explanation: Its unit is k J/kg K. It is another physical property of matter. All the matter has a temperature associated with it.

10. S.I unit of dynamic viscosity is
a) kg/m
b) kg/m s
c) m/kg
d) m s /kg

Explanation: Its unit is kg/m s. It is the kinematic viscosity per unit density.

Sanfoundry Global Education & Learning Series – Heat Transfer.

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