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MCQs 1: According to the Buckingham π–Theorem, the number of independent dimensionless groups, formed by combining the physical variables of a problem, is equal to

[total number of physical quantities (n)] – [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantitie [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] – [total number of physical quantities (n [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] + [total number of physical quantities (n)] [the number of primary dimensions (m) needed to express the dimensional formulae of n physical quantities] x [total number of physical quantities (n)]
Answer Explanation

MCQs 2: Which of the following dimensions is/are primary dimension/s?

length (L) time (t) temperature (T) all of the above
Answer Explanation

MCQs 3: What is the formula for Reynolds number (Re)? Where, ρ = density of the fluid μ = viscosity of the fluid D = tube diameter through which fluid is flowing v = velocity of the fluid

(Re) = (D v ρ) / μ (Re) = (D ρ μ) / v (Re) = (D v μ) / ρ none of the above
Answer Explanation

MCQs 4: The principle of similarity or model law states that

if the ratios of linear dimensions, forces, velocities, etc. of two systems are the same, then their behavior will be different as per the dimensions if the ratios of linear dimensions, forces, velocities, etc. of two systems are the same, then their behavior will be similar if the ratios of linear dimensions, forces, velocities, etc. of two systems are the different, then only their behavior will be similar none of the above
Answer Explanation

MCQs 5: Prandtl number is the ratio of

thermal diffusivity (α) to absolute viscosity (μ) absolute viscosity (μ) to thermal diffusivity (α) kinematic viscosity (ν) to thermal diffusivity (α) thermal diffusivity (α) to kinematic viscosity (ν)
Answer Explanation

MCQs 6: Wien's displacement law gives the relationship between

the wavelength of radiation at which total emissive power is maximum and the temperature the wavelength of radiation at which total emissive power is minimum and the temperature the wavelength of radiation at which total emissive power does not change and the temperature none of the above
Answer Explanation

MCQs 7: What is a gray body?

a body of which the monochromatic emissivity (ε) is different wavelengths a body of which the monochromatic emissivity (ε) is constant for the entire wavelength spectrum a body of which the monochromatic emissivity (ε) is maximum for longest wavelength none of the above
Answer Explanation

MCQs 8: The emissive power of gray body is

less than the emissive power of the black body greater than the emissive power of the black body equal to the emissive power of the black body cannot say
Answer Explanation

MCQs 9: What is the intensity of radiation (I)?

rate of heat radiation from a surface per unit area rate of heat radiation from a surface per unit solid angle rate of heat radiation from a surface per unit area per unit solid angle none of the above
Answer Explanation

MCQs 10: What is solid angle?

the ratio of spherical surface enclosed by a cone, with its vertex at the centre of sphere, to the radius of the sphere the ratio of spherical surface enclosed by a cone, with its vertex at the centre of sphere, to the square of the radius of the sphere the ratio of spherical surface enclosed by a cone, with its vertex at the centre of sphere, to the cube of the radius of the sphere the ratio of spherical surface enclosed by a cone, with its vertex at the centre of sphere, to the fourth power of the radius of the sphere
Answer Explanation

MCQs 11: The radiation heat exchange between two bodies depends upon

the views of two surfaces with each other the medium between the two bodies emitting and absorbing characteristics of the bodies all of the above
Answer Explanation

MCQs 12: Shape factor is also called as

view factor geometry factor configuration factor all of the above
Answer Explanation

MCQs 13: How does heat flux change with increasing excess temperature in transition boiling regime of boiling heat transfer process?

heat flux increases with increasing excess temperature heat flux decreases with increasing excess temperature heat flux becomes constant with increasing excess temperature none of the above
Answer Explanation

MCQs 14: Which regime in boiling heat transfer process can represent a transition from nucleate boiling to film boiling?

pure convection regime nucleate boiling regime transition boiling regime stable film boiling regime
Answer Explanation

MCQs 15: The nuclei of bubbles form in nucleate boiling, when there is presence of

superheated vapour superheated liquid dissolved gases un-dissolved gases
Answer Explanation

MCQs 16: When is the condensate flow almost always laminar?

when condensation occurs on a horizontal tube when condensation occurs on a vertical bank of horizontal tubes when condensation occurs on a vertical tube when condensation occurs on a bunch of vertical tubes
Answer Explanation

MCQs 17: In forced convection boiling process, a liquid flows through a tube with

superheated or unsaturated boiling subcooled or saturated boiling subcooled to superheated boiling vapour in boiling
Answer Explanation

MCQs 18: When the layers of a composite wall are in series and the thermal resistance of every individual layer is given then the total thermal resistance of the composite wall is given by

substantiating lower value thermal resistance from higher value thermal resistance adding both the thermal resistances multiplying both the thermal resistances none of the above
Answer Explanation

MCQs 19: What is the formula for the thermal resistance (R) of a hollow cylinder of internal radius Ri, outer radius Ro and the length l ? Thermal conductivity of the cylinder material is k. The heat flows from inner side to outer side.

R = ln (Ro / Ri) / 2πkl R = ln (Ri / Ro) / 2πkl R = (Ro + Ri) / 2πkl R = (RoRi) / 2πkl
Answer Explanation

MCQs 20: A hollow cylinder of length of 1m, inner radius (Ri) 0.01m and outer radius (Ro) 0.05m has a thermal conductivity (k) 20 W/mK. The inside surface temperature is at 500K. What is the outside surface temperature of the cylinder when the rate of radial heat transfer is 3.13 kW?

400 K 360 K 460 K insufficient data
Answer Explanation

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