# Dimensional Analysis for Estimation of Convection Heat Transfer Coefficient - 1 - MCQs with Answers

## Dimensional Analysis for Estimation of Convection Heat Transfer Coefficient – 1 – MCQs with Answers

1. What is/are the limitation/s of dimensional analysis for estimation of convection heat transfer coefficient

a. it does not provide any knowledge of the mechanism
b. it is necessary to know theoretically the variables which influence the phenomena
c. both a. and b.
d. none of the above

ANSWER: c. both a. and b.

2. Why is the Buckingham π–Theorem used?

a. to determine number of dependent dimensionless groups which are necessary to represent the phenomenon in a mathematical expression
b. to determine number of independent dimensionless groups which are necessary to represent the phenomenon in a mathematical expression
c. to determine number of dependent groups with their dimensions which are necessary to represent the phenomenon in a mathematical expression
d. to determine number of independent groups with their dimensions which are necessary to represent the phenomenon in a mathematical expression

ANSWER: b. to determine number of independent dimensionless groups which are necessary to represent the phenomenon in a mathematical expression

3. According to the Buckingham π–Theorem, the number of independent dimensionless groups, formed by combining the physical variables of a problem, is equal to

a. [total number of physical quantities (n)] – [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities]
b. [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] – [total number of physical quantities (n)]
c. [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] + [total number of physical quantities (n)]
d. [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] x [total number of physical quantities (n)]

ANSWER: a. [total number of physical quantities (n)] – [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities]

4. Which of the following dimensions is/are primary dimension/s?

a. length (L)
b. time (t)
c. temperature (T)
d. all of the above

ANSWER: d. all of the above

5. What is the dimensional formula for work?

a. [M L t– 3 ]
b. [M L2 t– 2 ]
c. [M L2 t– 3 ]
d. [M L2 T– 3 ]

ANSWER: b. [M L2 t– 2 ]

6. [M L– 1 T–2 ] is the dimensional formula for

a. power
b. force
c. pressure
d. heat

7. What is the formula for Reynolds number (Re)?

a. (Re) = (D v ρ) / μ
b. (Re) = (D ρ μ) / v
c. (Re) = (D v μ) / ρ
d. none of the above

Where,
ρ = density of the fluid
μ = viscosity of the fluid
D = tube diameter through which fluid is flowing
v = velocity of the fluid