Total Mechanical Engineering questions and answers with explanation for interview, competitive examination and entrance test. Fully solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. What is the difference between isotropic and anisotropic materials ?
2. What are orthotropic materials ?
3. A plain carbon steel has BHN of 180. What are values of Rc, VHN and ultimate strength ?
4. What properties need to be considered for applications calling for following re¬quirements :
5. Explain the effects of alloying chromium and nickel in stainless steel.
6. Mention two types of dislocations.
7. What are the principal constituents of brass?
8. What is Curie point ?
9. Specific strength of materials is very high when they are in fibre size but lower when they are in bar form Why ?
10. What is the percentage of carbon in cast iron ?
11. Which element is added in steel to increase resistance to corrosion ?
12. Whether individual components in composite materials retain their characteristics or not?
13. An elastomer is a polymer when its percentage elongation rate is ?
14. If percentage elongation of a material is more than 200%, it is classed as ?
15. Why is it that the maximum value which the residual stress can reach is the elastic limit of the material ?
16. Why fatigue strength decreases as size of a part increases beyond around 10 mm?
17. Distinguish between creep and fatigue.
18. While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength. Why ?
19. List at least two factors that promote transition from ductile to brittle fracture.
20. Which theories of failure are used for (a) ductile materials, and (b) brittle materials ?
21. The principal stresses at a point are tensile c?i = 250 MPa and compressive a% = 150 MPa. What is the maximum shear stress ? What is the facator of safety based on maxi¬mum shear stress theory, if yield stress of material is 600 MPa ?
22. Describe in brief the ar-rangement of atoms in metals/alloys.
23. What are the three forms of crystal structures for common metals?
24. Which is the common element between brass and bronze ?
25. What does following alloy designation indicate FG 250 ?
26. How is ceramic defined ?
27. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.
28. What is the name of solid solution of carbon in alpha iron and delta iron ?
29. Explain the difference between pearlite and cementile ?
30. Give one example each of the following proportion of materials—dimensional, physical, technological and mechanical.
31. For which parts the Wahl factor and Lewis form factor used ?
32. How oxygen can be removed from steel during melting? What are fully killed steels ?
33. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ?
34. What is allotrope ? In what forms of cubic pattern, iron exists ?
35. What is the difference between alpha iron, delta iron and gamma iron ?
36. Metals, in general are of low strength and do not possess required physiochemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.
37. What is the difference between isotropic material and homogeneous material ?
38. Explain the difference between the points of inflexion and contraflexure.
39. What is the difference between proof resilience and modulus of resilience ?
40. What is the difference between column and strut ?
41. Explain the difference between ferrite, austenite and graphite ?
42. Explain the terms—solid solution, eutectic, eutectoid and peritectic.
43. What do you understand by critical points in iron, iron-carbide diagram ?
44. Explain the difference between grey iron and white iron. What is mottled iron ?
46. What is the percentage of chromium in 18 : 4 : 1IISS ?
47. What is stellite ?
48. Which rays are produced by cobalt-60 in industrial radiography ?
49. What are killed steels and what for these are used ?
50. What is critical temperature in metals ?
51. Car tyres are usually made of ?
52. What is the structure of pure iron and whether it is soft or hard ?
53. Which elements increase the corrosion resistance of steel ?
54. What causes hardness in steel ? How heat treatment alters properties of steel ?
55. Explain the formation of microstructures of pearlite, bainite and martensite in steel.
56. How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?
57. What are the major effects of alloying elements?
58. What is the difference between austenite stabilisers and ferrite stabilisers ?
59. What are the effects of carbon on the properties of steel.
60. What is the role of silicon as alloying element in steels ?
61. Discuss the role of manganese in alloying steels.
62. Define buckling factor.
63. What do you understand by catenary cable ?
64. What is coaxing ?
65. What is difference between conjugate beam and continuous beam ?
66. What is isotropic material ?
67. Explain difference between modulus of resilience and modulus of rigidity ?
68. What is the difference between basic hole and basic shaft ?
69. What for pyranometer is used ?
70. Describe transfer machines in brief.
71. What is burnt-out point ?
72. What do you understand by eutectic ?
73. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ?
75. What is endurance limit and what is its value for steel ?
76. What do you know about metallography ?
77. What do you understand by sulphur print ?
78. What is the different between brass and bronze ?
79. What is the effect of addition of zinc in copper? What is the use of 70/30 brass ?
80. What for admirality brass used ?
81. What is the maximum use of magnesium ?
82. What for zinc finds applications ?
83. Which factors influence the type of fracture in failure of a material ?
84. Group the following into thermosets and thermoplastics :
85. List two effects of manganese in plain carbon steels.
86. Name the strongest and weakest type of atomic bonds.
88. What is temper embrittlement in alloy steels and what are its effects ?
89. What are whiskers ?
90. What is Bauschinger effect ?
91. What is the difference between heat capacity and specific heat of a material ?
92. Explain the rule to find specific heat of aqueous solutions.
93. What do you understand by latent heat ? Give four examples of latent heats.
94. Define the terms free energy and free enthalpy. What is their significance and import-ance ?
95. What do you understand by equation of state ? Write two thermodynamic equa¬tions of state.
98. Out of constant pressure and constant volume lines on TS diagram which line has higher slope ?
99. Whether entropy is intensive property or extensive property ?
100. In which process fluid expands but does no work ?
101. Whether superheated steam can be treated like ideal gas ?
102. Which parameter remains constant in isochoric process ?
103. In which process internal energy remains constant ?
104. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency.
105. For same compression ratio, whether otto or diesel cycle is more efficient ?
106. If cut off ratio of diesel cycle is increased, what happens to its efficiency ?
107. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume ?
108. Why axial flow compressor is preferred in aircraft gas turbines ?
109. How does ratio Cp/Cv behave with increase in temperature ?
110. Under what condition a convergent divergent nozzle required ?
111. Two columns, one of square cross section and other of circular cross section are made from same material, length and equal cross section. Which one will have higher buckling stability and why ?
112. Why PERT is preferred over CPM for evaluation of project ?
113. Which machine will produce continuous work without receiving any energy from other system or surroundeings ?
114. For which type of applications the V type guideway is best suited and for which dove-tail ?
116. In a cycle, air is compressed to a high pressure. Fuel is then injected into air, which is at a temperature above ignition point, and it burns at nearly constant pressure. Isentropic expansion of the products of combustion is followed by exhaust and suction of fresh air. Which is this cycle ?
117. For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these ?
118. Under what condition the extended surface effectively increases the heat transfer to or from a gas ?
119. An engine is visualised as a cylinder with a piston at each end. Between the pistons is a regenerator. The cylinder is assumed to be insulated except for a contact with a hot reservoir at one end and a contact with a cold reservoir at the other end. Which is this engine ?
121. How convective heat transfer is effected and on what factors it depends ?
122. For determination of heat transfer coefficient for convective heat flow for any set of conditions use is made of experimental data and dimensionless numbers are developed. What are these numbers and how they can be interpreted physically ?
123. What does thermal diffusivity of metals signify.
124. What is critical radius for small wires etc. ?
125. Which physical properties affect the film coefficient ? How film coefficient are correlated ?
128. Arrange the following substances, in order of increasing thermal conductivity. Stainless steel, air, silver, wood, water, lead, mild steel.
129. How the gray nature of real surfaces accounted for relating radiation between gray and black bodies ?
130. What is view factor ?
131. What do you understand by the term 'ablation' ?
133. What is mass transfer and state Fick's law ?
134. What do you understand by the term thermal diffusivity ?
137. What do you understand by free convection boundary layer and how does it affect heat transfer ?
138. What is meant by critical radius of insulation ?
139. What is Biot number ?
140. What do you understand by extendent surfaces ?
141. What is the efficiency of a fin ?
142. Why parabolic fins are preferred ?
143. What do you understand by shape factor in multi-dimensional steady state conduction ?
144. Define boundary layer concept.
145. What happens to static pressure, temperature, density and velocity across shock wave ?
149. Which non-dimensional number is associated with heat transfer by natural convection ?
150. What is gray surface in connection with heat transfer by radiation ?
151. What type of surface of a hot body radiates heat rapidly ?
152. What is black body ?
153. What is irradiation ?
154. What is fin ? What is the difference between fin efficiency and fin effectivness ?
157. What is the difference between steady state and unstead state heat transfer ?
158. Why the heat flow at the interface is small compared to main body ?
159. What is critical insulation radius ?
160. If critical insulation for cylinder is k/h, what is its value for sphere.
166. What is Stanton number in forced convection heat transfer and how it is related ?
167. What is significance of Grashof number in free convection ?
168. What is boundary layer thickness in free convection case ?
169. What do you understand by forced convection ?
170. What is boundary layer thickness in turbulent boundary layer ?
171. Whether the boundary layer in case of turbulent boundary layer is uniform in character along the entire length of surface ?
172. What would be the order of boundary layer in pipe flow(i) laminar (ii transition, and (iii) fully turbulent ?
173. In general how the boundary layer and local film coefficient of heat transfer are related ?
174. When the compressibility effects become significant in heat transfer problems in high speed flow ?
175. What is stagnation temperature and when it is encountered ?
176. In high speed flow, two numbers (Mach and Knudsen) are also considered in addition to Reynold number. What is Knudsen number ?
179. How you define the emissivity of a body ?
180. What is gray body ?
181. Rayleigh number is sometimes used in place of Grashof number in free convection heat transfer. How it is defined ?
182. Define fin efficiency for extended heat transfer surfaces.
183. What are the harmful effects of sulphur in coal used for power generation ?
184. What do you understand by microbial desulphurisation ?
186. What are the similarities between heat and work ?
187. Why work is considered as high grade of energy and heat as low grade energy ?
188. What is the difference between triple point and critical point of a substance ?
189. Does the area on PV diagram for a process represent work for both reversible and non-reversible process ?
194. What causes rotation of steam turbine rotor ?
195. What do you understand by the term coagulation ?
196. What is equivalent evaporation in a boiler plant ?
197. What is meant by balanced draft in boiler ?
198. How is dryness fraction of steam measured ?
199. What is the difference between isentropic process and throttlinglprocess ?
200. What is the difference between pyrometer, pyranometer and pyrheliometer.
201. What is the difference between scavanging and supercharging ?
202. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.
Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.
203. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?
204. Why entropy change for a reversible adiabatic process is zero ?
205. What are two essential conditions of perfect gas ?
206. Enthalpy and entropy are functions of one single parameter. Which is that ?
207. Why rate of condensation is higher on a polished surface compared to rusty surface ?
208. How much resistance is offered to heat flow by dropwise condensation ?
209. What is the relationship between COP of heating and cooling ?
210. How much is the work done in isochoric process ?
211. When maximum discharge is obtained in nozzle ?
212. Under what condition the work done in reciprocating compressor will be least ?
213. What is the difference between stalling and surging in rotary compressions ?
214. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition ?
215. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio ?
216. What is the name given to portion of thermal energy to be necessarily rejected to environment ?
217. What is pitting ? How it is caused ?
218. What is caustic embrittlement ?
219. Which impurities form hard scale and which impurities soft scale ?
220. What is the difference between hard water and soft water ?
221. Which two elements in feed water can cause corrosion of tubes and plates in boiler ?
222. What should be done to prevent a safety valve to stick to its seat ?
223. Why large boilers are water tube type ?
224. What type of boiler does not need a steam drum ?
225. Why manholes in vessels are usually elliptical in shape ?
226. Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water condition in boiler drum ?
227. Why boiler is purged every time before starting firing of fuel ?
228. What is the principle of mechanical refrigeration ?
229. Why high latent heat of vaporisation is desirable in a refrigerant ?
230. What is the critical temperature of a refrigerant ?
231. Maximum combustion temperature in gas turbines is of the order of 1100 to 1200°C whereas same is around 2000°C in I.C. engine ? Why ?
232. Why efficiency of gas turbines is lower compared to I.C. engines ?
233. What do you understand by timed cylinder lubrication ?
234. What is IIUCR in relation to petrol engine ?
235. In some engines glycerine is used in place of water for cooling of engine. Why ?
236. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four-stroke cycle petrol engine ?
237. As compression ratio increases, thermal n increases. How is thermal n affected by weak and rich mixture strength ?
238. How engine design needs to be changed to burn lean mixture ?
239. Horse power of I.C. engines can be expressed as RAC rating, SAE rating, or DIN rating. To which countries these standards belong ?
240. What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle ?
241. Why pistons are usually dished at top ?
242. What is the function of thermostat in cooling system of an engine ?
243. What is the value of cyclic integral of dQIT for a reversible cycle ?
242. What is the name given to a system in which mass remains constant but transfer of energy takes place across its boundaries ?
243. What are the causes of failure of boiler tubes ?
244. What are the causes of failure of super heater tubes ?
245. Why supercritical boilers use less amount of steel compared to non-supercritical boilers ?
246. Out of electric heater and heat pump, which is economical in operation ?
247. Which furnace burns low-ash fusion coal and retains most of the coal ash in the slag?
248. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ?
249. What is the effect of friction on flow of steam through a nozzle ?
250. Why gas turbine power plant needs efficient compressor ?
251. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon ?
252. Why axial flow compressor is preferred for gas turbines for aeroplanes ?
253. What is the effect of inter cooling in gas turbines ?
254. Why iso-octane is chosen as reference fuel for S.I. engines and allotted 100 value for its octane number ?
255. Why thermal efficiency of I.C. engines is more than that of gas turbine plant ?
256. Which are the reference fuels for knock rating of S.I. engines ?
257. When effect of variations in specific heats is considered then how do maximum temperature and pressure vary compared to air standard cycle ?
258. Quantities like pressure, temperature, density, viscosity, etc. are independent of mass. What are these called ?
259. The amount of radiation emitted per scm per sec is called .... ?
260. In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ?
261. How you can define coal ?
262. Which pollutant is major greenhouse gas and what is its effect ?
263. In order to increase efficiency and reduce CO2 emissions and other emissions, clear coal technologies are receiving major attention. What are these ?
264. What are the important operational performance parameters in design of fuel firing equipment ?
265. What is the difference between total moisture and inherent moisture in coal ?
266. Proximity analysis of coal provides data for a first, general assessment of a coal's quality and type. What elements it reports ?
267. Ultimate analysis of coal is elementary analysis. What it is concerned with ?
268. Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies.
269. What for Schmidt plot for is used in heat transfer problems ?
270. In which reactor the coolant and moderator are the same ?
271. Which reactor has no moderator ?
272. What are thermal neutrons ?
273. What is big advantage of fast breeder reactor ?
274. What is the purpose of biological shield in nuclear plants ?
275. Which two elements have same percentage in proximate and ultimate analysis of coal?
276. On which analysis is based the Dulong's formula for the heating value of fuel ?
277. Which element causes difference in higher and lower heating values of fuel ?
278. Which heating value is indicated by a calorimeter and why ?
279. State the difference between ultimate and proximate analysis of coal ?
280. What is fuel ratio ?
281. How the analyses and calorific values of fuels can be reported ?
282. What is the difference between nuclear fission and fission chain reaction.
283. Explain difference between fissile and fertile materials.
284. What do you understand by fuel cycle in nuclear plants ?
285. What is heavy water and what is its use in nuclear plants ?
286. What is a converter reactor ?
287. Explain nuclear reactor in brief.
288. What is the difference between conversion and enrichment ?
289. Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off ?.
290. Which nuclear reactor uses water as a coolant, moderator and reflector ?
291. Which reactor produces more fissionable material than it consumes ?
292. Which reactor uses natural uranium as fuel ?
293. Which reactor uses heavy water as moderator ?
294. Which reactor requires no moderator ?
295. Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium ?
296. Why an increase in area is required to produce an increase of velocity in case of supersonic flow ?
297. Under what circumstances would there be an increase in pressure in a divergent nozzle ?
298. Why water can't be used as refrigerant for small refrigerating equipment ?
299. Which parameter remains constant in a throttling process ?
300. How does the velocity of sound in gas varies with change in ratio of specific heats, absolute temperature, and specific gravity ?
1. What is the difference between isotropic and anisotropic materials ?
2. What are orthotropic materials ?
3. A plain carbon steel has BHN of 180. What are values of Rc, VHN and ultimate strength ?
4. What properties need to be considered for applications calling for following re¬quirements :
5. Explain the effects of alloying chromium and nickel in stainless steel.
6. Mention two types of dislocations.
7. What are the principal constituents of brass?
8. What is Curie point ?
9. Specific strength of materials is very high when they are in fibre size but lower when they are in bar form Why ?
10. What is the percentage of carbon in cast iron ?
11. Which element is added in steel to increase resistance to corrosion ?
12. Whether individual components in composite materials retain their characteristics or not?
13. An elastomer is a polymer when its percentage elongation rate is ?
14. If percentage elongation of a material is more than 200%, it is classed as ?
15. Why is it that the maximum value which the residual stress can reach is the elastic limit of the material ?
16. Why fatigue strength decreases as size of a part increases beyond around 10 mm?
17. Distinguish between creep and fatigue.
18. While normal carburising and nitriding surface treatments increase fatigue strength, excessive treatment may decrease the fatigue strength. Why ?
19. List at least two factors that promote transition from ductile to brittle fracture.
20. Which theories of failure are used for (a) ductile materials, and (b) brittle materials ?
21. The principal stresses at a point are tensile c?i = 250 MPa and compressive a% = 150 MPa. What is the maximum shear stress ? What is the facator of safety based on maxi¬mum shear stress theory, if yield stress of material is 600 MPa ?
22. Describe in brief the ar-rangement of atoms in metals/alloys.
23. What are the three forms of crystal structures for common metals?
24. Which is the common element between brass and bronze ?
25. What does following alloy designation indicate FG 250 ?
26. How is ceramic defined ?
27. Give one example of metal classified as per structure as BCC, FCC, HCP and CCP.
28. What is the name of solid solution of carbon in alpha iron and delta iron ?
29. Explain the difference between pearlite and cementile ?
30. Give one example each of the following proportion of materials—dimensional, physical, technological and mechanical.
31. For which parts the Wahl factor and Lewis form factor used ?
32. How oxygen can be removed from steel during melting? What are fully killed steels ?
33. Hydrogen cannot be removed easily from molten steel. What harm hydrogen has on property of steel ?
34. What is allotrope ? In what forms of cubic pattern, iron exists ?
35. What is the difference between alpha iron, delta iron and gamma iron ?
36. Metals, in general are of low strength and do not possess required physiochemical and technological properties for a definite purpose. Alloys are therefore more than metals alone. Discuss the arrangement of atoms and structures of alloys.
37. What is the difference between isotropic material and homogeneous material ?
38. Explain the difference between the points of inflexion and contraflexure.
39. What is the difference between proof resilience and modulus of resilience ?
40. What is the difference between column and strut ?
41. Explain the difference between ferrite, austenite and graphite ?
42. Explain the terms—solid solution, eutectic, eutectoid and peritectic.
43. What do you understand by critical points in iron, iron-carbide diagram ?
44. Explain the difference between grey iron and white iron. What is mottled iron ?
46. What is the percentage of chromium in 18 : 4 : 1IISS ?
47. What is stellite ?
48. Which rays are produced by cobalt-60 in industrial radiography ?
49. What are killed steels and what for these are used ?
50. What is critical temperature in metals ?
51. Car tyres are usually made of ?
52. What is the structure of pure iron and whether it is soft or hard ?
53. Which elements increase the corrosion resistance of steel ?
54. What causes hardness in steel ? How heat treatment alters properties of steel ?
55. Explain the formation of microstructures of pearlite, bainite and martensite in steel.
56. How with alloying of steel it is possible to a achieve properties which can not be achieved with heat treatment ?
57. What are the major effects of alloying elements?
58. What is the difference between austenite stabilisers and ferrite stabilisers ?
59. What are the effects of carbon on the properties of steel.
60. What is the role of silicon as alloying element in steels ?
61. Discuss the role of manganese in alloying steels.
62. Define buckling factor.
63. What do you understand by catenary cable ?
64. What is coaxing ?
65. What is difference between conjugate beam and continuous beam ?
66. What is isotropic material ?
67. Explain difference between modulus of resilience and modulus of rigidity ?
68. What is the difference between basic hole and basic shaft ?
69. What for pyranometer is used ?
70. Describe transfer machines in brief.
71. What is burnt-out point ?
72. What do you understand by eutectic ?
73. The graphite in grey irons exists in the form of flakes which act as stress-raisers under tensile loading and consequently grey irons have relatively low tensile strength and ductility. Still grey iron is extensively used in engineering. Why ?
75. What is endurance limit and what is its value for steel ?
76. What do you know about metallography ?
77. What do you understand by sulphur print ?
78. What is the different between brass and bronze ?
79. What is the effect of addition of zinc in copper? What is the use of 70/30 brass ?
80. What for admirality brass used ?
81. What is the maximum use of magnesium ?
82. What for zinc finds applications ?
83. Which factors influence the type of fracture in failure of a material ?
84. Group the following into thermosets and thermoplastics :
85. List two effects of manganese in plain carbon steels.
86. Name the strongest and weakest type of atomic bonds.
88. What is temper embrittlement in alloy steels and what are its effects ?
89. What are whiskers ?
90. What is Bauschinger effect ?
91. What is the difference between heat capacity and specific heat of a material ?
92. Explain the rule to find specific heat of aqueous solutions.
93. What do you understand by latent heat ? Give four examples of latent heats.
94. Define the terms free energy and free enthalpy. What is their significance and import-ance ?
95. What do you understand by equation of state ? Write two thermodynamic equa¬tions of state.
98. Out of constant pressure and constant volume lines on TS diagram which line has higher slope ?
99. Whether entropy is intensive property or extensive property ?
100. In which process fluid expands but does no work ?
101. Whether superheated steam can be treated like ideal gas ?
102. Which parameter remains constant in isochoric process ?
103. In which process internal energy remains constant ?
104. What is the name given to ratio of actual cycle efficiency and ideal cycle efficiency.
105. For same compression ratio, whether otto or diesel cycle is more efficient ?
106. If cut off ratio of diesel cycle is increased, what happens to its efficiency ?
107. How the net work to drive a compressor and its volumetric efficiency behave with increase in clearance volume ?
108. Why axial flow compressor is preferred in aircraft gas turbines ?
109. How does ratio Cp/Cv behave with increase in temperature ?
110. Under what condition a convergent divergent nozzle required ?
111. Two columns, one of square cross section and other of circular cross section are made from same material, length and equal cross section. Which one will have higher buckling stability and why ?
112. Why PERT is preferred over CPM for evaluation of project ?
113. Which machine will produce continuous work without receiving any energy from other system or surroundeings ?
114. For which type of applications the V type guideway is best suited and for which dove-tail ?
116. In a cycle, air is compressed to a high pressure. Fuel is then injected into air, which is at a temperature above ignition point, and it burns at nearly constant pressure. Isentropic expansion of the products of combustion is followed by exhaust and suction of fresh air. Which is this cycle ?
117. For conduction of heat, the instantaneous rate of heat flow is product of three factors. What are these ?
118. Under what condition the extended surface effectively increases the heat transfer to or from a gas ?
119. An engine is visualised as a cylinder with a piston at each end. Between the pistons is a regenerator. The cylinder is assumed to be insulated except for a contact with a hot reservoir at one end and a contact with a cold reservoir at the other end. Which is this engine ?
121. How convective heat transfer is effected and on what factors it depends ?
122. For determination of heat transfer coefficient for convective heat flow for any set of conditions use is made of experimental data and dimensionless numbers are developed. What are these numbers and how they can be interpreted physically ?
123. What does thermal diffusivity of metals signify.
124. What is critical radius for small wires etc. ?
125. Which physical properties affect the film coefficient ? How film coefficient are correlated ?
128. Arrange the following substances, in order of increasing thermal conductivity. Stainless steel, air, silver, wood, water, lead, mild steel.
129. How the gray nature of real surfaces accounted for relating radiation between gray and black bodies ?
130. What is view factor ?
131. What do you understand by the term 'ablation' ?
133. What is mass transfer and state Fick's law ?
134. What do you understand by the term thermal diffusivity ?
137. What do you understand by free convection boundary layer and how does it affect heat transfer ?
138. What is meant by critical radius of insulation ?
139. What is Biot number ?
140. What do you understand by extendent surfaces ?
141. What is the efficiency of a fin ?
142. Why parabolic fins are preferred ?
143. What do you understand by shape factor in multi-dimensional steady state conduction ?
144. Define boundary layer concept.
145. What happens to static pressure, temperature, density and velocity across shock wave ?
149. Which non-dimensional number is associated with heat transfer by natural convection ?
150. What is gray surface in connection with heat transfer by radiation ?
151. What type of surface of a hot body radiates heat rapidly ?
152. What is black body ?
153. What is irradiation ?
154. What is fin ? What is the difference between fin efficiency and fin effectivness ?
157. What is the difference between steady state and unstead state heat transfer ?
158. Why the heat flow at the interface is small compared to main body ?
159. What is critical insulation radius ?
160. If critical insulation for cylinder is k/h, what is its value for sphere.
166. What is Stanton number in forced convection heat transfer and how it is related ?
167. What is significance of Grashof number in free convection ?
168. What is boundary layer thickness in free convection case ?
169. What do you understand by forced convection ?
170. What is boundary layer thickness in turbulent boundary layer ?
171. Whether the boundary layer in case of turbulent boundary layer is uniform in character along the entire length of surface ?
172. What would be the order of boundary layer in pipe flow(i) laminar (ii transition, and (iii) fully turbulent ?
173. In general how the boundary layer and local film coefficient of heat transfer are related ?
174. When the compressibility effects become significant in heat transfer problems in high speed flow ?
175. What is stagnation temperature and when it is encountered ?
176. In high speed flow, two numbers (Mach and Knudsen) are also considered in addition to Reynold number. What is Knudsen number ?
179. How you define the emissivity of a body ?
180. What is gray body ?
181. Rayleigh number is sometimes used in place of Grashof number in free convection heat transfer. How it is defined ?
182. Define fin efficiency for extended heat transfer surfaces.
183. What are the harmful effects of sulphur in coal used for power generation ?
184. What do you understand by microbial desulphurisation ?
186. What are the similarities between heat and work ?
187. Why work is considered as high grade of energy and heat as low grade energy ?
188. What is the difference between triple point and critical point of a substance ?
189. Does the area on PV diagram for a process represent work for both reversible and non-reversible process ?
194. What causes rotation of steam turbine rotor ?
195. What do you understand by the term coagulation ?
196. What is equivalent evaporation in a boiler plant ?
197. What is meant by balanced draft in boiler ?
198. How is dryness fraction of steam measured ?
199. What is the difference between isentropic process and throttlinglprocess ?
200. What is the difference between pyrometer, pyranometer and pyrheliometer.
201. What is the difference between scavanging and supercharging ?
202. What are the names given to constant temperature, constant pressure, constant volume, constant internal energy, constant enthalpy, and constant entropy processes.
Isothermal, isochroic, isobaric, free expression, throttling and adiabatic processes respectively.
203. In a Rankine cycle if maximum steam pressure is increased keeping steam temperature and condenser pressure same, what will happen to dryness fraction of steam after expansion ?
204. Why entropy change for a reversible adiabatic process is zero ?
205. What are two essential conditions of perfect gas ?
206. Enthalpy and entropy are functions of one single parameter. Which is that ?
207. Why rate of condensation is higher on a polished surface compared to rusty surface ?
208. How much resistance is offered to heat flow by dropwise condensation ?
209. What is the relationship between COP of heating and cooling ?
210. How much is the work done in isochoric process ?
211. When maximum discharge is obtained in nozzle ?
212. Under what condition the work done in reciprocating compressor will be least ?
213. What is the difference between stalling and surging in rotary compressions ?
214. Why the electric motor of a fan with backward curved blades is never got overloaded under any condition ?
215. Why the work per kg of air flow in axial flow compressor is less compared to centrifugal compressor for same pressure ratio ?
216. What is the name given to portion of thermal energy to be necessarily rejected to environment ?
217. What is pitting ? How it is caused ?
218. What is caustic embrittlement ?
219. Which impurities form hard scale and which impurities soft scale ?
220. What is the difference between hard water and soft water ?
221. Which two elements in feed water can cause corrosion of tubes and plates in boiler ?
222. What should be done to prevent a safety valve to stick to its seat ?
223. Why large boilers are water tube type ?
224. What type of boiler does not need a steam drum ?
225. Why manholes in vessels are usually elliptical in shape ?
226. Low water in boiler drum is unsafe because it may result in overheating of water tubes in furnace. Why it is unsafe to have high water condition in boiler drum ?
227. Why boiler is purged every time before starting firing of fuel ?
228. What is the principle of mechanical refrigeration ?
229. Why high latent heat of vaporisation is desirable in a refrigerant ?
230. What is the critical temperature of a refrigerant ?
231. Maximum combustion temperature in gas turbines is of the order of 1100 to 1200°C whereas same is around 2000°C in I.C. engine ? Why ?
232. Why efficiency of gas turbines is lower compared to I.C. engines ?
233. What do you understand by timed cylinder lubrication ?
234. What is IIUCR in relation to petrol engine ?
235. In some engines glycerine is used in place of water for cooling of engine. Why ?
236. Why consumption of lubricating oil is more in two-stroke cycle petrol engine than four-stroke cycle petrol engine ?
237. As compression ratio increases, thermal n increases. How is thermal n affected by weak and rich mixture strength ?
238. How engine design needs to be changed to burn lean mixture ?
239. Horse power of I.C. engines can be expressed as RAC rating, SAE rating, or DIN rating. To which countries these standards belong ?
240. What is the use of flash chamber in a vapour compression refrigeration cycle to improve the COP of refrigeration cycle ?
241. Why pistons are usually dished at top ?
242. What is the function of thermostat in cooling system of an engine ?
243. What is the value of cyclic integral of dQIT for a reversible cycle ?
242. What is the name given to a system in which mass remains constant but transfer of energy takes place across its boundaries ?
243. What are the causes of failure of boiler tubes ?
244. What are the causes of failure of super heater tubes ?
245. Why supercritical boilers use less amount of steel compared to non-supercritical boilers ?
246. Out of electric heater and heat pump, which is economical in operation ?
247. Which furnace burns low-ash fusion coal and retains most of the coal ash in the slag?
248. How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ?
249. What is the effect of friction on flow of steam through a nozzle ?
250. Why gas turbine power plant needs efficient compressor ?
251. Why rockets using liquid hydrogen have higher specific impulse compared to liquid hydrocarbon ?
252. Why axial flow compressor is preferred for gas turbines for aeroplanes ?
253. What is the effect of inter cooling in gas turbines ?
254. Why iso-octane is chosen as reference fuel for S.I. engines and allotted 100 value for its octane number ?
255. Why thermal efficiency of I.C. engines is more than that of gas turbine plant ?
256. Which are the reference fuels for knock rating of S.I. engines ?
257. When effect of variations in specific heats is considered then how do maximum temperature and pressure vary compared to air standard cycle ?
258. Quantities like pressure, temperature, density, viscosity, etc. are independent of mass. What are these called ?
259. The amount of radiation emitted per scm per sec is called .... ?
260. In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ?
261. How you can define coal ?
262. Which pollutant is major greenhouse gas and what is its effect ?
263. In order to increase efficiency and reduce CO2 emissions and other emissions, clear coal technologies are receiving major attention. What are these ?
264. What are the important operational performance parameters in design of fuel firing equipment ?
265. What is the difference between total moisture and inherent moisture in coal ?
266. Proximity analysis of coal provides data for a first, general assessment of a coal's quality and type. What elements it reports ?
267. Ultimate analysis of coal is elementary analysis. What it is concerned with ?
268. Explain the difference between AFBC, BFBC, PFBC and PCFB in regard to fluidised bed technologies.
269. What for Schmidt plot for is used in heat transfer problems ?
270. In which reactor the coolant and moderator are the same ?
271. Which reactor has no moderator ?
272. What are thermal neutrons ?
273. What is big advantage of fast breeder reactor ?
274. What is the purpose of biological shield in nuclear plants ?
275. Which two elements have same percentage in proximate and ultimate analysis of coal?
276. On which analysis is based the Dulong's formula for the heating value of fuel ?
277. Which element causes difference in higher and lower heating values of fuel ?
278. Which heating value is indicated by a calorimeter and why ?
279. State the difference between ultimate and proximate analysis of coal ?
280. What is fuel ratio ?
281. How the analyses and calorific values of fuels can be reported ?
282. What is the difference between nuclear fission and fission chain reaction.
283. Explain difference between fissile and fertile materials.
284. What do you understand by fuel cycle in nuclear plants ?
285. What is heavy water and what is its use in nuclear plants ?
286. What is a converter reactor ?
287. Explain nuclear reactor in brief.
288. What is the difference between conversion and enrichment ?
289. Disposal of radioactive waste materials and spent fuel is a major and important technology. How the waste radioactive material is disposed off ?.
290. Which nuclear reactor uses water as a coolant, moderator and reflector ?
291. Which reactor produces more fissionable material than it consumes ?
292. Which reactor uses natural uranium as fuel ?
293. Which reactor uses heavy water as moderator ?
294. Which reactor requires no moderator ?
295. Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium ?
296. Why an increase in area is required to produce an increase of velocity in case of supersonic flow ?
297. Under what circumstances would there be an increase in pressure in a divergent nozzle ?
298. Why water can't be used as refrigerant for small refrigerating equipment ?
299. Which parameter remains constant in a throttling process ?
300. How does the velocity of sound in gas varies with change in ratio of specific heats, absolute temperature, and specific gravity ?
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