chemical engineering Mcqs
4201. A hot body will radiate heat most rapidly, if its surface is___________________?
comments icon0

A. White & polished

B. White & rough

C. Black & rough

D. Black & polished

4202. Harmonic mean temperature difference is given by_________________?
comments icon0
A. 2 (?T1 . ?T2)/(?T1 + ?T2)

B. (?T1 ?T2)/(?T1 . ?T2)

C. 2 (?T1 . ?T2)/(?T1 ?T2)

D. ?(?T1 . ?T2)

4203. Reynolds analogy states that_________________?
comments icon0
A. Nst ? f

B. NNu ? f

C. Nst ? NRe

D. NRe ? f

4204. Prandtl number is the ratio of________________?
comments icon0

A. Mass diffusivity to thermal diffusivity

B. Thermal diffusivity to momentum diffusivity

C. Thermal diffusivity to mass diffusivity

D. Momentum diffusivity to thermal diffusivity
4205. In forced circulation, the heating element is injected_________________?
comments icon0
A. Internally

B. Externally

C. Both A. and A.

D. Neither A. nor B.

4206. During crystallisation, formation of crystal can occur in ______________ solution only?
comments icon0

A. All A., B. and C.

B. Saturated

C. Supersaturated

D. Under-saturated

4207. The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
comments icon0

A. ?T

B. ? 1/T

C. Independent of T

D. ? T4

4208. Grashoff number, which is defined as g . ? (Ts T?) ?2. L3/?2, is proportional to the ratio of buoyancy force to ____________ force?
comments icon0
A. Viscous

B. None of these

C. Elastic

D. Inertial

4209. In forced convection, the heat transfer depends on _______________?
comments icon0

A. Re, Gr

B. Re only

C. Re, Pr

D. Mainly Gr

4210. Heat produced when a steady state current, I passes through an electrical conductor having resistance, R is___________________?
comments icon0
A. I2R

B. IR

C. I2R2

D. IR2

4211. Fouling factor_____________________?
comments icon0

A. Is a dimensionless quantity

B. Accounts for additional resistances to heat flow

C. Does not provide a safety factor for design

D. None of these

4212. The rate of heat transfer through a pipe wall is given by, q = 2? k (Ti T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?
comments icon0
A. q = 2? k (Ti T0)/[(r0 + ri)/2]

B. q = 2? k (Ti T0)/(r0/ri)

C. q = 2? ri k (Ti T0)/(r0/ri)

D. q = [2? k (Ti + T0)/2]/ln (ri/r0)

4213. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by___________________?
comments icon0
A. Newtons law of cooling

B. Ficks law

C. Fouriers law

D. None of these

4214. Heat transfer rate per unit area is called_________________?
comments icon0

A. Heat transfer co-efficient

B. Thermal conductivity

C. Heat flux

D. Thermal diffusivity

4215. A black body when hot, emits heat radiation of _____________ wavelengths?
comments icon0

A. One fixed

B. Large

C. All

D. Small

4216. Agitated film evaporator is suitable for concentrating _____________ liquids?
comments icon0

A. Very thin

B. Foaming

C. Viscous

D. Corrosive

4217. Which of the following situations can be approximated to a steady state heat transfer system ?
comments icon0

A. ntained constant at 180C

B. osed to atmospheric air at 35C</strong>

C. ospheric air at 35C

D. A sub-cooled refrigerant liquid at 8C flowing at the rate of 6 Kg/minute through a copper

E. A red hot steel slab (having outside surface temperature as 1300C) exposed to the

F. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is

4218. Heat transfer by natural convection is enhanced in system with__________________?
comments icon0

A. Low density change with temperature

B. High viscosity

C. Low temperature gradients

D. High co-efficient of thermal expansion
4219. 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________________?
comments icon0

A. 133

B. 160

C. 125

D. 150

4220. What is the logarithmic mean of r1 and r2 ?
comments icon0

A. (r1 r2)/-ln(r1/r2)

B. (r2 r1)/ln(r1/r2)

C. (r1 r2)/ln(r1/r2)

D. (r1 r2)/ln(r2/r1)

4221. What is the thermal conductivity of a perfect heat insulator ?
comments icon0

A. Between 0 and ?

B. One

C. ?

D. Zero
4222. Heat transfer co-efficient (h1) for liquids increases with__________________?
comments icon0

A. Decreasing temperature

B. None of these

C. Increasing temperature

D. Decreasing Reynolds number

4223. For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is_________________?
comments icon0

A. 3

B. 1

C. 1.33

D. 0.33

4224. In a single effect evaporator, the economy is________________?
comments icon0
A. < 1

B. > 1

C. 1

D. None of these

4225. In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is_________________?
comments icon0
A. Infinity

B. None of these

C. Zero

D. Same as average heat transfer co-efficient for tube side

4226. A 10 cm dia steam pipe, carrying steam at 180C, is covered with an insulation (conductivity = 0.6 W/m.C). It losses heat to the surroundings at 30C. Assume a heat transfer co-efficient of 0.8 W/m2.C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?
comments icon0

A. Less than the steam pipe with 5 cms insulation

B. Equal to that of the un-insulated steam pipe

C. Greater than that for un-insulated steam pipe

D. Less than that of the un-insulated steam pipe
4227. Steam is routed through the tube in case of a ______________ evaporator?
comments icon0
A. Horizontal tube

B. Basket type

C. Short tube vertical

D. Long tube vertical

4228. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is______________?
comments icon0

A. Dependent on NRe only

B. 1.66

C. 3.66

D. 88.66

4229. Economy of a multiple effect evaporator depends upon the _____________________?
comments icon0
A. Heat balance consideration

B. Rate of heat transfer

C. Both A. and B.

D. Neither A. nor B.

4230. Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80C and leaves at 50C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20C. The log mean temperature difference in C is approximately ?
comments icon0

A. 50

B. 32

C. 45

D. 37

4231. Trap is used to remove ________________ from steam pipe lines?
comments icon0

A. Steam

B. Non-condensable

C. None of these

D. Condensate
4232. Boiling of milk in an open vessel is an example of ______________ boiling?
comments icon0

A. Sub-cooled

B. None of these

C. Film

D. Saturated nucleate

4233. In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to _____________ the velocity head?
comments icon0

A. Twice

B. Square root of

C. Four times

D. Square of

4234. In the equation Q = UA?t; ?t is_________________________?
comments icon0

A. Arithmetic mean temperature difference

B. Geometric mean temperature difference

C. The difference of average bulk temperatures of hot and cold fluids

D. Logarithmic mean temperature difference
4235. In Joules experiment, an insulated container contains 20 kg of water initially at 25C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in C) is________________?
comments icon0

A. 25

B. 34.4

C. 40.5

D. 26.8

4236. As per Kirchoff?s law, the ratio of the total radiating power to the absorptivity of a body depends on the_______________?
comments icon0
A. Temperature of the body only

B. Wavelength of monochromatic radiation

C. Both A. and B.

D. Nature of material of body

4237. Heat flux through several resistances in series in analogous to the current flowing through several_____________________?
comments icon0

A. Capacitors in series

B. Resistances in series

C. Resistances in parallel

D. None of these

4238. Sensible heat of hot industrial flue gases cannot be recovered by a/an________________?
comments icon0

A. Economiser

B. None of these

C. Ceramic recuperator

D. Regenerator

4239. Which area is used in case of heat flow by conduction through a cylinder ?
comments icon0
A. Logarithmic mean area

B. None of these

C. Arithmetic mean area

D. Geometric mean area

4240. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is_________________?
comments icon0

A. 4

B. 2-Jan

C. 1

D. 2
4241. Radiation heat transfer rates does not depend upon the_________________?
comments icon0

A. Surface area and temperature of the heat source

B. Distance between the heat source and the object receiving the heat

C. None of these

D. Type of absorbing surface

4242. As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient ?
comments icon0

A. Goes through a maximum

B. Continues to increase

C. Continues to decrease

D. Goes through a minimum
4243. The rate of emission of radiation by a body does not depend upon the__________________?
comments icon0

A. Surface temperature of the body

B. Shape and porosity of the body

C. Wavelength of radiation

D. Nature of the surface

4244. The ratio of momentum diffusivity to thermal diffusivity is the ______________ number?
comments icon0

A. Nusselt

B. Grashoff

C. Stanton

D. Prandtl
4245. When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as ___________________ boiling?
comments icon0

A. Transition

B. Nucleate

C. Pool

D. Film
4246. Electromagnetic radiations propagate in vacuum with a velocity of _______________ metre/second?
comments icon0
A. 3 108

B. 3 1012

C. 3 105

D. 3 1010

4247. Which of the following has the minimum absorptivity ?
comments icon0

A. Refractory bricks

B. Iron plates

C. Aluminium foil

D. Coal dust

4248. In case of _____________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid?
comments icon0
A. Pool

B. Nucleate

C. Low pressure

D. None of these

4249. For an ideal black body______________________?
comments icon0

A. Transmissivity = 1

B. Reflectivity = 1

C. Emissivity = 0

D. Absorptivity = 1
4250. Nusselt number (for forced convection heat transfer) is a function of the _____________ number?
comments icon0

A. Prandtl

B. Reynolds

C. Both A. & B.

D. Neither A. nor B.