Heat and Mass Transfer - Set 01 - ObjectiveBooks
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# Practice Test: Question Set - 01

1. Unit of thermal conductivity in M.K.S. units is
(A) K cal/kg m² °C
(B) K cal m/hr m² °C
(C) K cal/hr m² °C
(D) K calm/hr °C

2. Thermal diffusivity is a
(A) Function of temperature
(B) Physical property of a substance
(C) Dimensionless parameter
(D) All of these

3. Unit of thermal conductivity in S.I. units is
(A) J/m² sec
(B) J/m °K sec
(C) W/m °K
(D) Option (B) and (C) above.

4. Which of the following statement is wrong?
(A) The heat transfer in liquid and gases takes place according to convection
(B) The amount of heat flow through a body is dependent upon the material of the body
(C) The thermal conductivity of solid metals increases with rise in temperature
(D) Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference

5. Thermal conductivity of solid metals with rise in temperature normally
(A) Increases
(B) Decreases
(C) Remain constant
(D) May increase or decrease depending on temperature

6. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
(A) Reynold's number
(B) Grashoff's number
(C) Reynold's number, Grashoff's number
(D) Prandtl number, Grashoff's number

7. Thermal conductivity of non-metallic amorphous solids with decrease in temperature
(A) Increases
(B) Decreases
(C) Remain constant
(D) May increase or decrease depending on temperature

8. According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)
(A) Pb = pa - pv
(B) Pb = pa + pv
(C) Pb = p× pv
(D) Pb = pa/pv

9. Heat transfer takes place as per
(A) Zeroth law of thermodynamics
(B) First law of thermodynamic
(C) Second law of the thermodynamics
(D) Kirchoff's law

10. The heat transfer by conduction through a thick sphere is given by
(A) Q = 2πkr1 r2 (T1 - T2)/ (r2 - r1)
(B) Q = 4πkr1 r2 (T1 - T2)/ (r2 - r1)
(C) Q = 6πkr1 r2 (T1 - T2)/ (r2 - r1)
(D) Q = 8πkr1 r2 (T1 - T2)/ (r2 - r1)

11. When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by
(A) Conduction
(B) Convection
(D) Conduction and convection

12. Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)
(A) k. A. (dT/dx)
(B) k. A. (dx/dT)
(C) k. (dT/dx)
(D) k. (dx/dT)

13. When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by
(A) Conduction
(B) Convection
(D) Conduction and convection

14. Reynolds number (RN) is given by (where h = Film coefficient, l = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, ρ = Density of fluid, cp = Specific heat at constant pressure, and μ = Coefficient of absolute viscosity)
(A) RN = hl/k
(B) RN = μ cp/k
(C) RN = ρ V l /μ
(D) RN = V²/t.c

15. Sensible heat is the heat required to
(A) Change vapour into liquid
(B) Change liquid into vapour
(C) Increase the temperature of a liquid of vapour
(D) Convert water into steam and superheat it

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