chemical engineering heat transfer chemical engineering Mcqs
151. Nusselt number is the ratio of the temperature gradient at the wall to_________________?
comments icon0
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_________________?
comments icon0

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_________________?
comments icon0
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_________________?
comments icon0

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________________?
comments icon0

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_________________?
comments icon0
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 ?
comments icon0
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_______________?
comments icon0

A. Conduction

B. Convection

C. Radiation

D. Both A. & C.

159. A black body when hot, emits heat radiation of _____________ wavelengths?
comments icon0

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) ?
comments icon0

A. 1/T4

B. T4

C. 1/t4

D. t4

161. The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?
comments icon0
A. Heat flux

B. Prandtl number

C. Schmidt number

D. Nusselt number

162. Stefan-Boltzmann law applies to _____________ body?
comments icon0
A. Black

B. Any colour

C. Grey

D. White

163. Stefans block body radiation law can also be derived from ______________ law?
comments icon0

A. Fouriers

B. Plancks

C. None of these

D. Kirchoffs

164. Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
comments icon0

A. Grashoff

B. Reynolds

C. Both a & b

D. Prandtl & Grashoff
165. What is the unit of thermal conductivity ?
comments icon0

A. Kcal/hr. C

B. Kcal/hr.m.C

C. Kcal/hr. m2 C

D. Kcal/hr.m

166. In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is______________________?
comments icon0

A. 2000

B. 5000

C. 4000

D. 6000

167. Heat transfer rate per unit area is called_________________?
comments icon0

A. Thermal diffusivity

B. Thermal conductivity

C. Heat transfer co-efficient

D. Heat flux
168. Kg of liquid evaporated per hour in an evaporator is defined as its_________________?
comments icon0
A. Capacity

B. Economy

C. None of these

D. Steam load

169. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?
comments icon0

A. 0.4

B. 0.2

C. 0.6

D. 0.8

170. Terminal point temperature differences between fluids in case of a heat exchanger is termed as__________________?
comments icon0
A. Approach

B. Log mean temperature difference

C. Arithmetic mean temperature difference

D. Geometric mean temperature difference

171. With increase in temperature, the thermal conductivity of fresh lubricating oil ___________________?
comments icon0

A. May increase or decrease; depends on its composition

B. Decreases

C. Remains unchanged

D. Increases

172. The Stefan-Boltzmann constant depends on the_________________?
comments icon0

A. Medium

B. Surface

C. None of these

D. Temperature

173. To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is _______________?
comments icon0
A. 1-1 heat exchanger

B. 3-2 heat exchanger

C. 1-2 heat exchanger

D. 2-4 heat exchanger

174. Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?
comments icon0
A. Falling film

B. Long tube

C. None of these

D. High pressure

175. Evaporation by thermo compression results in the _________________________?
comments icon0

A. Saving of steam

B. Realisation of multiple effect economy in a single effect

C. Both A. and B.

D. None of these

176. It is not preferable to use superheated steam in evaporators, because of its very_________________?
comments icon0

A. High pressure

B. High temperature

C. None of these

D. Low film co-efficient
177. The left face of a one dimensional slab of thickness 0.2 m is maintained at 80C and the right face is exposed to air at 30C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in C is____________________?
comments icon0

A. 77.2

B. 71.2

C. 63.8

D. 48.7
178. Boiling point elevation for a strong and concentrated solution is found by Duhrings rule, which states that at the same pressure, the boiling point of a solution is a linear function of the _______________ of pure water?
comments icon0

A. Kinematic viscosity

B. Boiling point

C. Dynamic viscosity

D. Density

179. The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in K). The units of a in SI system will be________________?
comments icon0

A. W/m

B. None, a is just a number

C. W/m.k

D. W/m.k2
180. A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36C. The temperature difference across the layer A is ______________ C?
comments icon0

A. 24

B. 18

C. 6

D. 12
181. Natural convection is characterised by__________________?
comments icon0
A. Grashoff number

B. Peclet number

C. Reynolds number

D. Prandtl number

182. Which of the following is directly concerned with the heat transfer ?
comments icon0

A. Sherwood number

B. Grashoff number

C. Euler number

D. Strouhal number

183. Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. C respectively are joined together. The temperature outside of A and C are 30C and 100C respectively. The interface between B and C will be at a temperature of ____________ C?
comments icon0
A. 70

B. 50

C. 95

D. 40

184. The heat transfer co-efficient in film type condensation is _______________ that for dropwise condensation?
comments icon0

A. Half

B. Greater than

C. Is same as

D. Lower than
185. Radiator of an automobile engine is a ______________ type of heat exchanger?
comments icon0

A. Cross-current

B. Co-current

C. Direct contact

D. Counter-current

186. Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around _____________ metres/second?
comments icon0

A. 10

B. 20

C. 1

D. 30

187. When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
comments icon0

A. Free convection

B. Entry length problem in laminar forced conduction (developing thermal boundary layer)

C. Mixed convection (both free and forced)

D. Forced convection

188. A BTU/hr.ft.2 F is equal to_________________?
comments icon0

A. None of these

B. 1 kcal/hr. m2.K

C. 4.88 kcal/hr. m.2C

D. 1 kcal/hr. m2C

189. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
comments icon0
A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)

B. Outlet temperature of both the hot and cold fluid are same

C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid

D. None of these

190. A body cools down from 75C to 70C in 10 minutes. It will cool down from 70 C to 65 C in ______________ minutes?
comments icon0

A. < 10

B. 10

C. > 10

D. Either B. or C., depends on the mass of the body

191. In forced convection, the heat transfer depends on _______________?
comments icon0

A. Mainly Gr

B. Re, Pr

C. Re, Gr

D. Re only

192. The Graetz number is concerned with the___________________
comments icon0

A. Absorption with chemical reaction

B. Heat transfer in laminar flow

C. Heat transfer in turbulent flow

D. Mass transfer between a gas and a liquid

193. Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)?
comments icon0

A. 0.5 D

B. 0.2 D

C. 0.66 D

D. 0.80 D

194. The main purpose of providing fins on heat transfer surface is to increase the_________________?
comments icon0

A. Heat transfer co-efficient

B. Temperature gradient

C. Heat transfer area

D. Mechanical strength of the equipment

195. Temperature profile in steady state heat transfer is________________?
comments icon0
A. Linear

B. Parabolic

C. Asymptotic

D. Hyperbolic

196. The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) ?
comments icon0

A. 2K/h0

B. hi/K

C. 2hi/K

D. K/h0
197. Maximum heat transfer rate is achieved in _____________ flow?
comments icon0
A. Turbulent

B. Co-current

C. Counter-current

D. Laminar

198. The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?
comments icon0
A. Less

B. More

C. Same

D. Unpredictable

199. Agitated film evaporator is suitable for concentrating _____________ liquids?
comments icon0

A. Very thin

B. Viscous

C. Corrosive

D. Foaming

200. Tube expansion allowances exist in _____________ heat exchanger?
comments icon0
A. U-tube

B. Single pass fixed tube sheet

C. None of these

D. Multipass fixed tube sheet