# Heat Transfer MCQ’s – Buckingham’s Pi- Method

1 - Question

f 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 - Question

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 - Question

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 - Question

he 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 - Question

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.

6 - Question

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 - Question

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 - Question

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 - Question

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 - Question

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