chemical engineering heat transfer chemical engineering MCQs – Page 7

Practise multiple-choice questions from chemical engineering heat transfer chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering heat transfer chemical engineering Mcqs

121. In a shell and tube heat exchanger, square pitch compared to triangular pitch__________________?
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A. Gives a higher shell side pressure drop

B. Gives a lower shell side pressure drop

C. Can pack more surface area into a shell of given diameter

D. None of these

122. In SI units, fouling factor is expressed in __________________?
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A. m2K/W

B. m2K

C. W/m2K

D. mK/W

123. A _____________ evaporator employs an annular downtake?
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A. Horizontal

B. Long tube vertical

C. None of these

D. Basket type

124. With increase in temperature, the thermal conductivity of most liquids_________________?
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A. Increases

B. Decreases

C. Remain same

D. First increases upto a certain temperature and then becomes constant

125. Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?
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A. 1/U1 1/U2

B. U2 U1

C. 1/U2 1/U1

D. U1 U2

126. The equation, Nst = f/2, is the _____________ analogy?
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A. Colburn

B. Reynolds

C. None of these

D. Prandtl

127. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows ____________ law?
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A. Logarithmic

B. Parabolic

C. Linear

D. Hyperbolic

128. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is______________?
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A. Nu = 0.023 Re0.8. Pr0.4

B. Nu = (?/2) Gz

C. Nu = (2/?) Gz

D. Nu = 2Gz0.5

129. In case of _______________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?
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A. Nucleate

B. Saturated

C. Local

D. Pool

130. Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is ________________ law?
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A. Wiens

B. Daltons

C. Kirchoffs

D. Stefans

131. The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re)0.8 (Pr)0.4] cannot be used for________________?
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A. Low Reynolds number

B. All A., B. and C.

C. Very low Grashoff number

D. Molten metals

132. Prandtl number for most of dry gases is about________________?
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A. 0.72

B. 70

C. 150

D. 0.001

133. Resistance to heat flow by conduction is proportional to (where, t & ? are thickness & density of the material respectively and A = area normal to the direction of heat flow.) ?
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A. t

B. 1/?

C. All A., B. & C.

D. 1/A

134. Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)?
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A. K/Ax

B. x/KA

C. KA/x

D. A/Kx

135. The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are _______________?
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A. (COP)R = 1.5; (COP)HP = 2.5

B. (COP)R = 2.5; (COP)HP = 1.5

C. (COP)R = (COP)HP = 2.5

D. (COP)R = (COP)HP = 0.6

136. A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300C and allowed to cool in natural air. Which one will cool the slowest ?
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A. Sphere

B. All will cool at the same rate

C. Plate

D. Cube

137. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because__________________?
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A. Total amount of vapor produced per Kg of feed steam in a multiple effect system is much

B. Total heat transfer area of all the effects is -less than that in a single effect evaporator system

C. Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect

D. Boiling point elevation in a single effect system is much higher than that in any effect in a

E. her than in a single effect</strong>

F. tem

138. The unit of conductance in SI unit is_______________?
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A. W/m

B. W/mK

C. W/m2

D. W/K

139. With increase in temperature, the total emissivity of conductors____________________?
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A. Remain same

B. Decreases linearly

C. Decreases

D. Increases

140. Out of the following four assumptions used in the derivation of the equation for LMTD [LMTD = (?t1 ?t2)/ln(?t1/?t2)], which one is subject to the largest deviation in practice ?
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A. Constant specific heat

B. No partial phase change in the system

C. Constant overall heat transfer co-efficient.

D. Constant rate of fluid flow

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