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MCQOPTIONS
This section includes 640 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
Grashhoff number is given by |
| A. | gD3.β.Δtρ2/μ2 |
| B. | gD2βΔtρ/μ2 |
| C. | gD2βΔtP2μ |
| D. | gD3βΔtP2/μ |
| Answer» B. gD2Œ≤ŒîtœÅ/Œº2 | |
| 252. |
Out of the following four assumptions used in the derivation of the equation for LMTD , which one is subject to the largest deviation in practice ? |
| A. | Constant overall heat transfer co-efficient. |
| B. | Constant rate of fluid flow. |
| C. | Constant specific heat. |
| D. | No partial phase change in the system. |
| Answer» C. Constant specific heat. | |
| 253. |
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) |
| A. | D/5 and D |
| B. | D/2 and 2 D |
| C. | D/4 and 2 D |
| D. | D and 2 D |
| Answer» B. D/2 and 2 D | |
| 254. |
In an extended surface heat exchanger, fluid having lower co-efficient |
| A. | flows through the tube. |
| B. | flows outside the tubes. |
| C. | can flow either inside or outside the tubes. |
| D. | should not be used as it gives very high pressure drop. |
| Answer» C. can flow either inside or outside the tubes. | |
| 255. |
Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. )$ |
| A. | t |
| B. | 1/ρ |
| C. | 1/A |
| D. | all (a), (b) & (c) |
| Answer» E. | |
| 256. |
Double pipe heat exchangers are used |
| A. | when heat transfer area required is very high. |
| B. | when heat transfer area required is very low, i.e (100-200 ft2). |
| C. | because it occupies less floor area. |
| D. | because it is less costly. |
| Answer» C. because it occupies less floor area. | |
| 257. |
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because |
| A. | total heat transfer area of all the effects is -less than that in a single effect evaporator system. |
| B. | total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect. |
| C. | boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system. |
| D. | heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system. |
| Answer» C. boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system. | |
| 258. |
Heat transfer by natural convection is enhanced in system with |
| A. | high viscosity. |
| B. | high co-efficient of thermal expansion. |
| C. | low temperature gradients. |
| D. | low density change with temperature. |
| Answer» C. low temperature gradients. | |
| 259. |
In a boiling curve, the peak heat flux is called the __________ point. |
| A. | Nusselt |
| B. | Leidenfrost |
| C. | boiling |
| D. | burnout |
| Answer» E. | |
| 260. |
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case, |
| A. | the cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant. |
| B. | both the spheres will emit equal amount of radiation per unit time in the beginning. |
| C. | both will absorb equal amount of radiation from the surrounding in the beginning. |
| D. | both(b) & (c). |
| Answer» E. | |
| 261. |
In a backward feed multiple effect evaporator |
| A. | feed is introduced in the first effect. |
| B. | feed flows from low pressure to high pressure. |
| C. | no pumps are required between successive effects. |
| D. | none of these. |
| Answer» C. no pumps are required between successive effects. | |
| 262. |
The units of resistance to heat transfer is |
| A. | J.m-2.K-1 |
| B. | J.m-1.K-1 |
| C. | W.m-2.K-1 |
| D. | W-1m2K |
| Answer» E. | |
| 263. |
Prandtl number for most of dry gases is about |
| A. | 0.001 |
| B. | 0.72 |
| C. | 70 |
| D. | 150 |
| Answer» C. 70 | |
| 264. |
Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low |
| A. | hardness |
| B. | dissolved soilds content |
| C. | suspended solids content |
| D. | all (a), (b) and(c) |
| Answer» E. | |
| 265. |
When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as __________ boiling. |
| A. | pool |
| B. | nucleate |
| C. | transition |
| D. | film |
| Answer» E. | |
| 266. |
At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below :The thermal conductivity of material I |
| A. | is smaller than that of II. |
| B. | is greater than that of II. |
| C. | is equal to that of II. |
| D. | can be greater than or smaller than that of II. |
| Answer» B. is greater than that of II. | |
| 267. |
Peclet number (Pe) is given by |
| A. | Pe = Re.Pr |
| B. | Pe = Re/Pr |
| C. | Pe = Pr/Re |
| D. | Pe = Nu.Re |
| Answer» B. Pe = Re/Pr | |
| 268. |
jH factor for heat transfer depends upon the __________ number. |
| A. | Biot |
| B. | Nusselt |
| C. | Reynolds |
| D. | Prandtl |
| Answer» D. Prandtl | |
| 269. |
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always |
| A. | < 1 |
| B. | > 1 |
| C. | 1 |
| D. | ‚àû |
| Answer» B. > 1 | |
| 270. |
All analogy equations connecting friction factor and heat transfer co-efficient apply only to |
| A. | wall or skin friction |
| B. | form friction |
| C. | both (a) and (b) |
| D. | turbulent flow |
| Answer» B. form friction | |
| 271. |
The main purpose of providing fins on heat transfer surface is to increase the |
| A. | temperature gradient. |
| B. | mechanical strength of the equipment. |
| C. | heat transfer area. |
| D. | heat transfer co-efficient. |
| Answer» D. heat transfer co-efficient. | |
| 272. |
Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called |
| A. | radiation |
| B. | natural convection |
| C. | forced convection |
| D. | conduction |
| Answer» D. conduction | |
| 273. |
Which of the following has the highest thermal conductivity ? |
| A. | Brick |
| B. | Air |
| C. | Water |
| D. | Silver |
| Answer» E. | |
| 274. |
For what value of Prandtl number, St = f/2? |
| A. | 1.5 |
| B. | 1 |
| C. | > 1 |
| D. | < 1 |
| Answer» C. > 1 | |
| 275. |
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m2°C.$ |
| A. | 18537 |
| B. | 100-500 |
| C. | 1000-1500 |
| D. | 5000-15000 |
| Answer» E. | |
| 276. |
Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the |
| A. | maximum resistance in the series. |
| B. | sum of all resistances. |
| C. | average of all resistances. |
| D. | minimum resistance presents in the series. |
| Answer» C. average of all resistances. | |
| 277. |
In a shell and tube heat exchanger, |
| A. | the temperature drops in the two fluids and the wall are proportional to individual resistances. |
| B. | the temperature drop is inversely proportional to the resistance across which the drop occurs. |
| C. | there is no relationship between temperature drop and resistance. |
| D. | the relationship is not generalised. |
| Answer» B. the temperature drop is inversely proportional to the resistance across which the drop occurs. | |
| 278. |
LMTD can't be used as such without a correction factor for the |
| A. | multipass heat exchanger. |
| B. | baffled heat exchanger. |
| C. | condensation of mixed vapour in a condenser. |
| D. | all (a) (b) and (c). |
| Answer» E. | |
| 279. |
Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is |
| A. | 0.4 |
| B. | 0.5 |
| C. | 0.6 |
| D. | 0.7 |
| Answer» E. | |
| 280. |
Forced circulation evaporators are normally used for concentrating liquids having |
| A. | scaling characteristics |
| B. | high viscosity |
| C. | both(a) & (b) |
| D. | neither (a) nor (b) |
| Answer» D. neither (a) nor (b) | |
| 281. |
The ratio of kinematic viscosity to thermal diffusivity is called the __________ number. |
| A. | Peclet |
| B. | Prandtl |
| C. | Stanton |
| D. | Nusselt |
| Answer» C. Stanton | |
| 282. |
For hot feed, forward feeding as compared to backward feeding results in __________ economy. |
| A. | increased |
| B. | decreased |
| C. | no effect on |
| D. | none of these |
| Answer» B. decreased | |
| 283. |
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body) |
| A. | αT |
| B. | α 1/T |
| C. | α T4 |
| D. | independent of T |
| Answer» C. Œ± T4 | |
| 284. |
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 |
| A. | 2000 |
| B. | 4000 |
| C. | 5000 |
| D. | 6000 |
| Answer» D. 6000 | |
| 285. |
Removal of __________ heat is involved in the condensation of a vapor under saturated conditions. |
| A. | super |
| B. | sensible |
| C. | latent |
| D. | both(b) & (c) |
| Answer» C. latent | |
| 286. |
The thermal boundary layer at NPr > 1 |
| A. | is thicker than hydrodynamic boundary layer. |
| B. | is thinner than hydrodynamic boundary layer. |
| C. | and the hydrodynamic boundary layer are identical. |
| D. | disappears. |
| Answer» C. and the hydrodynamic boundary layer are identical. | |
| 287. |
Film condensation is promoted on a/an __________ surface. |
| A. | oily |
| B. | coated |
| C. | clean & smooth |
| D. | dirty |
| Answer» D. dirty | |
| 288. |
Pick out the correct equation. |
| A. | jH = (St)(Pr)2/3 = f/2 |
| B. | jH = (St)(Pr)1/3 = f/2 |
| C. | jH = (St)2/3(Pr) = f/2 |
| D. | jH = (St)1/3(Pr) = f/2 |
| Answer» B. jH = (St)(Pr)1/3 = f/2 | |
| 289. |
Heat transfer rate per unit area is called |
| A. | thermal conductivity |
| B. | heat flux |
| C. | heat transfer co-efficient |
| D. | thermal diffusivity |
| Answer» C. heat transfer co-efficient | |
| 290. |
Which of the following is directly concerned with the heat transfer ? |
| A. | Strouhal number |
| B. | Sherwood number |
| C. | Euler number |
| D. | Grashoff number |
| Answer» E. | |
| 291. |
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is |
| A. | 0.1 |
| B. | >1 |
| C. | < 1 |
| D. | l |
| Answer» B. >1 | |
| 292. |
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 1200°K, then the temperature drop (in °K) across the layer of material 'A' is$ |
| A. | 125 |
| B. | 133 |
| C. | 150 |
| D. | 160 |
| Answer» E. | |
| 293. |
In forced circulation, the heating element is injected |
| A. | internally |
| B. | externally |
| C. | both (a) and (a) |
| D. | neither (a) nor (b) |
| Answer» B. externally | |
| 294. |
In case of a multipass shell and tube heat exchanger, the temperature drop in the fluid |
| A. | is inversely proportional to the resistance across which the drop occurs. |
| B. | and the wall are proportional to individual resistances. |
| C. | and the wall is not related. |
| D. | none of these. |
| Answer» C. and the wall is not related. | |
| 295. |
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m3 and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m2.K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is$ |
| A. | 555 |
| B. | 55.5 |
| C. | 0.55 |
| D. | 0.15 |
| Answer» E. | |
| 296. |
A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an |
| A. | ellipse |
| B. | straight line |
| C. | parabola |
| D. | circular arc |
| Answer» C. parabola | |
| 297. |
Steam trap is used to |
| A. | condense the steam flowing in the pipeline. |
| B. | remove water resulting from partial condensation of steam. |
| C. | stop the supply of steam. |
| D. | none of these. |
| Answer» C. stop the supply of steam. | |
| 298. |
With increase in temperature, the thermal conductivity of most liquids |
| A. | increases |
| B. | decreases |
| C. | remains same |
| D. | first increases upto a certain temperature and then becomes constant |
| Answer» C. remains same | |
| 299. |
The rate of emission of radiation by a body does not depend upon the |
| A. | wavelength of radiation. |
| B. | surface temperature of the body. |
| C. | nature of the surface. |
| D. | shape and porosity of the body. |
| Answer» E. | |
| 300. |
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer |
| A. | decreases |
| B. | increases |
| C. | increases exponentially |
| D. | remains unaffected |
| Answer» B. increases | |