Heat Transfer Questions and Answers – Correlations for Forced Convection

This set of Heat Transfer Multiple Choice Questions & Answers (MCQs) focuses on “Correlations For Forced Convection”.

1. The convective heat transfer coefficient in laminar flow over a flat plate
a) Increases with distance
b) Increases if a higher viscosity fluid is used
c) Increases if a denser fluid is used
d) Decreases with increase in free stream velocity
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2. For laminar flow over a flat plate, the average value of a Nusselt number is prescribed by the relation
Nu = 0.664 (Re) ^0.5 (Pr) ^0.33
Which of the following is then a false statement?
a) Density has to be increased four times
b) Plate length has to be decreased four times
c) Specific heat has to be increased four times
d) Dynamic viscosity has to be decreased sixteen times
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3. For turbulent flow over a flat plate, the average value of Nusselt number is prescribed by the relation
Nu = 0.664 (Re) ^0.5 (Pr) ^0.33
Which of the following is then a false statement?
The average heat transfer coefficient increases as
a) 1/5 power of plate length
b) 2/3 power of thermal conductivity
c) 1/3 power of specific heat
d) 4/5 power of a free stream velocity
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4. A nuclear reactor with its core constructed of parallel vertical plates 2.25 m high and 1.5 m wide has been designed on free convection heating of liquid bismuth. Metallurgical considerations limit the maximum surface temperature of the plate to 975 degree Celsius and the lowest allowable temperature of bismuth is 325 degree Celsius. Estimate the maximum possible heat dissipation from both sides of each plate. The appropriate correlation for the convection coefficient is
Nu = 0.13 (Gr Pr) ^1/3
a) 143 MW
b) 153 MW
c) 163 MW
d) 173 MV
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5. The Grashoff number for a nuclear reactor’s vertical plates, 2.25 m high and 1.5 m wide, heated by free convection of liquid bismuth, needs to be calculated. The correlation for the convection coefficient is: Nu = 0.13 (Gr Pr)^(1/3). What is the value of the Grashoff number for this system?
a) 101.3 * 10 ¹²
b) 102.3 * 10 ¹²
c) 103.3 * 10 ¹²
d) 104.3 * 10 ¹²
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6. A thin walled duct of 0.5 m diameter has been laid in an atmosphere of quiescent air at 15 degree Celsius and conveys a particular gas at 205 degree Celsius. Base your calculations on one meter length of the duct, estimate the convective coefficient of heat transfer
a) 5.086 W/m² K
b) 6.086 W/m² K
c) 7.086 W/m² K
d) 8.086 W/m² K
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7. Free correction modulus is given by
a) p ² β g c _P/µ
b) p ² β g c _P/k
c) p ² β g c _P/µ k
d) p ² β g c _P
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8. The free convection coefficient is given by
h = C ₁ d t ^m/l ^{1 – 3m}
The value of exponent for laminar flow is
a) 0.5
b) 0.6
c) 0.7
d) 0.8
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9. For inclined plates we multiply Grashoff number with
a) Cos 2 α
b) Sin 2 α
c) Sin α
d) Cos α
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10. The free convection coefficient is given by
h = C ₁ d t ^m/l ^{1 – 3m}
The value of exponent for turbulent flow is
a) 0.43
b) 0.33
c) 0.23
d) 0.13
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Sanfoundry Global Education & Learning Series – Heat Transfer.

To practice all areas of Heat Transfer, here is complete set of 1000+ Multiple Choice Questions and Answers.