chemical engineering heat transfer chemical engineering MCQs – Page 8

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 Review each marked answer and report any item that may be outdated or unclear.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
141. A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of__________________?
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A. 20.8

B. 2

C. 20.5

D. 20.2

142. Which of the following is the most widely used heat insulating material for pipelines carrying steam ?
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A. 85% magnesia cement and glass wool

B. Tar dolomite bricks followed by asbestos

C. Fireclay refractory followed by aluminium sheet

D. Cotton followed by aluminium foil

143. In SI units, thermal conductivity is expressed in__________________?
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A. Watt/m.K

B. Watt/m2. K

C. Watt/m4. K

D. Watt/m2. K

144. Fqra cold viscous feed, backward feed gives _____________ than forward feed?
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A. Lower economy

B. A higher capacity

C. None of these

D. A lower capacity

145. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ?
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A. Once

B. Four times

C. Thrice

D. Twice
146. At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?
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A. < 0.1

B. > 0.6

C. < 0.5

D. 0.5

147. For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it__________________?
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A. Decreases the pressure drop

B. Increases the overall heat transfer coefficient

C. Decreases the outlet temperature of cooling medium

D. None of these

148. Steam economy in case of a triple effect evaporator will be _________________?
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A. 1

B. Between 0 and 1

C. > 1

D. < 1

149. A composite flat wall of a furnace is made of two materials A and B. The thermal conductivity of A is twice of that of material B, while the thickness of layer of A is half that of B. If the temperature at the two sides of the wall are 400 and 1200K, then the temperature drop (in K) across the layer of material A is________________?
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A. 133

B. 160

C. 150

D. 125

150. Dittus-Boelter equation used for the determination of heat transfer co-efficient is valid ___________________?
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A. When Grashoff number is very important

B. For fluids in turbulent flow

C. For fluids in laminar flow

D. For liquid metals

151. Nusselt number is the ratio of the temperature gradient at the wall to_________________?
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A. That across the entire pipe

B. Heat flux

C. Temperature difference

D. None of these

152. An equipment which converts the latent or sensible heat of one fluid into the latent heat of vaporisation of another, is called a_________________?
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A. Recuperator

B. Heat exchanger

C. Regenerator

D. Boiler

153. Tubes are held between top and bottom tube sheets in Calandria type evaporator by keeping_________________?
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A. Both the tube sheets fixed

B. Both the tube sheets floating

C. The top tube sheet floating and bottom tube sheet fixed

D. The top tube sheet fixed and the bottom tube-sheet floating

154. Solid angle subtended by the finite surface at the radiating element is_________________?
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A. Proportional to the square of the distance between surfaces

B. Called the angle of vision

C. Called the view factor

D. Expressed in terms of radians

155. Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is________________?
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A. Shell and tube heat exchanger with air inside tubes and steam on shell side

B. Shell and tube heat exchanger with air on shell side and steam inside tubes

C. Finned tube heat exchanger with air inside and steam outside

D. Finned tube heat exchanger with air outside and steam inside
156. LMTD cant be used as such without a correction factor for the_________________?
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A. All A. B. and C.

B. Condensation of mixed vapour in a condenser

C. Multipass heat exchanger

D. Baffled heat exchanger

157. When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ?
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A. At high fluid velocity

B. When fluid flows past a smooth surface

C. At low velocity

D. None of these

158. When warm and cold liquids are mixed, the heat transfer is mainly by_______________?
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A. Conduction

B. Convection

C. Radiation

D. Both A. & C.

159. A black body when hot, emits heat radiation of _____________ wavelengths?
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A. One fixed

B. All

C. Small

D. Large

160. Stefan-Boltzmann law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in C T = absolute temperature in K) ?
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A. 1/T4

B. T4

C. 1/t4

D. t4