McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 101. |
In the expansion process, which of the following remains constant? |
| A. | work done |
| B. | heat supplied |
| C. | internal energy |
| D. | enthalpy |
| Answer» D. enthalpy | |
| Explanation: the expansion is an adiabatic throttling process in which enthalpy remains unchanged. | |
| 102. |
The COP of cycle is given by(Q2=heat absorbed by evaporator and Wc=work done by compressor) |
| A. | 1- (q2/wc) |
| B. | 1- (wc/q2) |
| C. | q2/wc |
| D. | wc/q2 |
| Answer» C. q2/wc | |
| Explanation: this is the cop of vapour refrigeration cycle. | |
| 103. |
Which of the following is recommended in a refrigeration cycle? |
| A. | superheating of vapour |
| B. | subcooling of liquid |
| C. | both of the mentioned |
| D. | none of the mentioned |
| Answer» C. both of the mentioned | |
| Explanation: the superheating of vapour is done at evaporator outlet and subcooling of liquid occurs at condenser outlet. | |
| 104. |
A condenser must and then the compressed refrigerant. |
| A. | superheat, evaporate |
| B. | desuperheat, evaporate |
| C. | superheat, condense |
| D. | desuperheat, condense |
| Answer» D. desuperheat, condense | |
| Explanation: this is the function of a condenser. | |
| 105. |
In absorption refrigeration cycle, which of the following is used? |
| A. | refrigerant |
| B. | absorbent |
| C. | both of the mentioned |
| D. | none of the mentioned |
| Answer» C. both of the mentioned | |
| Explanation: both refrigerant and absorbent are used in absorption refrigeration cycle. | |
| 106. |
In absorption system, compressor in vapour compression cycle is replaced by absorber- generator assembly. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: the absorber-generator assembly involves less mechanical work. | |
| 107. |
In the aqua-ammonia absorption system, |
| A. | water is the refrigerant and ammonia is the absorbent |
| B. | ammonia is the refrigerant and water is the absorbent |
| C. | both ammonia and water can be used as refrigerant or absorbent |
| D. | none of the mentioned |
| Answer» B. ammonia is the refrigerant and water is the absorbent | |
| Explanation: this is the basic absorption refrigeration cycle. | |
| 108. |
Which of the following statement is true? |
| A. | ammonia vapour is absorbed in water |
| B. | boiling point of ammonia is more than that of water |
| C. | both of the mentioned |
| D. | none of the mentioned |
| Answer» A. ammonia vapour is absorbed in water | |
| Explanation: the boiling point of ammonia is less than that of water. | |
| 109. |
Which of the following condenses first? |
| A. | ammonia vapour |
| B. | water vapour |
| C. | both condense at same temperature |
| D. | none of the mentioned |
| Answer» B. water vapour | |
| Explanation: the saturation temperature of water is higher than ammonia at any given pressure. | |
| 110. |
The vapour going to condenser is in temperature and in ammonia. |
| A. | higher, less |
| B. | higher, richer |
| C. | lower, less |
| D. | lower, richer |
| Answer» D. lower, richer | |
| Explanation: when passing through analyser, the vapour is cooled and enriched by ammonia. | |
| 111. |
Lithium bromide-water vapour is another absorption refrigeration system. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in this, water is the refrigerant and solution of lithium bromide in water is the absorbent. | |
| 112. |
Water is used as a in air conditioning units. |
| A. | absorbent |
| B. | refrigerant |
| C. | absorbent and refrigerant |
| D. | none of the mentioned |
| Answer» B. refrigerant | |
| Explanation: the reason is that water cannot be cooled below 0 degree celsius. | |
| 113. |
Room air conditioners and packaged units are examples of |
| A. | direct expansion systems |
| B. | indirect expansion systems |
| C. | chilled water systems |
| D. | indirect contraction systems |
| Answer» A. direct expansion systems | |
| Explanation: air conditioning systems are classified into two categories. these are direct expansion systems and chilled water | |
| 114. |
Which of the following is not a component of packaged air conditioners? |
| A. | compressor |
| B. | condenser |
| C. | chiller |
| D. | evaporator |
| Answer» C. chiller | |
| Explanation: packaged air conditioners consist of a compressor, condenser, evaporator and a fan. unlike packaged air | |
| 115. |
In a chilled water system, the refrigerant is used to cool the air directly while in the direct expansion system, a secondary medium like water is used to cool the air. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: in the direct expansion system, the refrigerant is used to cool the air directly while in the chilled water system, a secondary medium like water is used to cool the air. in the chilled water system, the refrigerant first cools the water and then the water cools the air. | |
| 116. |
In which component of the chilled water system, the return air and the fresh air mixture is filtered? |
| A. | fan coil unit |
| B. | ducting grill |
| C. | compressor |
| D. | evaporator |
| Answer» A. fan coil unit | |
| Explanation: in the chilled water system, the return air and the fresh air mixture is filtered in the fan coil unit. here, in addition to filtration, the mixture is cooled and dehumidified. after this, it is distributed to the conditioned space through ducting and grills. | |
| 117. |
Which of the following qualities is not possessed by the filters in the air conditioning system? |
| A. | they should be capable of removing dust particles from the incoming air |
| B. | they should afford easy cleaning |
| C. | they should offer low frictional resistance to the airflow |
| D. | they should offer high frictional resistance to the airflow |
| Answer» D. they should offer high frictional resistance to the airflow | |
| Explanation: the filters in the air conditioning system should be capable of removing dust particles from the incoming air. they should afford easy cleaning and should offer low frictional resistance to the airflow. | |
| 118. |
Viscous type filters are made of screens of spilt wire and coated with non-drying viscous oil in order to catch and remove the dust particles from the incoming air. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: viscous type filters are made of screens of spilt wire and coated with non- drying viscous oil in order to catch and remove the dust particles from the incoming air. they can be of two types – unit type or automatic type. | |
| 119. |
Which of the following statements about electric precipitators is false? |
| A. | they are used to remove dust by providing a strong electric field |
| B. | their initial installation cost is high |
| C. | their operational cost is low |
| D. | dust particles get attached to the positive electrode |
| Answer» D. dust particles get attached to the positive electrode | |
| Explanation: electric precipitators are used to remove dust by providing a strong electric field. in an electric precipitator, the dust particles get attached to the negative | |
| 120. |
The process of extraction of the certain required amount of water from air is known as |
| A. | heating |
| B. | cooling |
| C. | humidification |
| D. | dehumidification |
| Answer» D. dehumidification | |
| Explanation: the process of extraction of a certain required amount of water from air is known as dehumidification. this can be achieved by condensation or desiccation. | |
| 121. |
Which of the following is capable of absorbing excess moisture from the air? |
| A. | silica gel |
| B. | charcoal |
| C. | salts of calcium or ammonia |
| D. | activated alumina |
| Answer» C. salts of calcium or ammonia | |
| Explanation: absorbents like salts of calcium or ammonia are capable of absorbing excess moisture from the air. however, the adsorbents like silica gel and activated alumina allow moisture to stay only at the surface. | |
| 122. |
Open cooling system is also called as |
| A. | parallel system |
| B. | once through system |
| C. | air based system |
| D. | non-reversible system |
| Answer» B. once through system | |
| Explanation: open system is also called as once through system, in this system the water is drawn directly from the upstream side of the river pumped through the condenser and discharged to the downstream side of the river at temperature 5 to 10°c in excess of inlet temperature. | |
| 123. |
How many number of spray nozzle does each module on spray pond cooling system contains? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» D. 4 | |
| Explanation: modules in spray pond cooling system contain 4 spray nozzles. the surface area of contact of water is increased when it is sprayed in air. cooling occurs due to the evaporation of water vapours as the spray propels upwards and falls down to the surface. | |
| 124. |
Which of the following is the simplest method of cooling the condenser water? |
| A. | spray cooling pond |
| B. | cooling tower |
| C. | indirect air cooling |
| D. | hyperbolic cooling tower |
| Answer» A. spray cooling pond | |
| Explanation: spray cooling pond is the simplest method of all. the hot water coming out of the condenser is sprayed through the nozzles to expose maximum surface area of water to air for effective cooling. the spray ponds are surrounded with wooden walls to prevent the wind from carrying the water particles. | |
| 125. |
In which type of cooling system are nozzles arranged on different elevation? |
| A. | single deck system |
| B. | double deck system |
| C. | natural flow system |
| D. | direct flow system |
| Answer» B. double deck system | |
| Explanation: in double system of cooling ponds the spray nozzles are arranged at different elevations. cooling effect is more than single deck cooling system as water comes in contact with air at lower temperatures. | |
| 126. |
What are used in the direct flow system to transverse the pond before uniting at intake? |
| A. | separators |
| B. | filters |
| C. | baffle walls |
| D. | porous pipes |
| Answer» C. baffle walls | |
| Explanation: in direct flow system the hot water coming out of the condenser enters the middle channel. on reaching the far end it is divided into two currents being directed by the baffle walls so as to transverse the pond several times before uniting at intake point. | |
| 127. |
What type of cooling system is used in the large power plants? |
| A. | cooling ponds |
| B. | natural flow system |
| C. | cooling towers |
| D. | single deck system |
| Answer» C. cooling towers | |
| Explanation: in large power plants cooling towers are used in the place of cooling ponds. a cooling tower is a wooden or metallic rectangular structure, with packed baffling devices. the hot water is delivered to the top of tower and is made to fall down the tower and is broken into small particles while passing over the baffling devices. | |
| 128. |
How does outside air enter into the wet cooling system? |
| A. | air vents |
| B. | louvers |
| C. | tuyeres |
| D. | vacuum |
| Answer» B. louvers | |
| Explanation: air and water are thoroughly mixed by fill as water splashes down from | |
| 129. |
Why is exhaust steam coming out of turbine is admitted to a steam header? |
| A. | to increase the pressure |
| B. | to decrease the velocity |
| C. | to decrease the pressure drop |
| D. | to control the pollution |
| Answer» C. to decrease the pressure drop | |
| Explanation: exhaust steam from turbine is admitted to a steam header in order to minimize the pressure drop. steam gets condensed as it passes down through the finned tubes arranged in parallel rows. | |
| 130. |
In which system is Cooling of hot water is done on tray as step by? |
| A. | mechanical draught cooling system |
| B. | hyperbolic cooling tower |
| C. | atmospheric cooling tower |
| D. | wet cooling tower |
| Answer» C. atmospheric cooling tower | |
| Explanation: in atmospheric cooling tower, the hot water is delivered at the top most trays and it falls down from one tray to another until it reaches the tank below the tower. the water is cooled by air flowing across the tower. | |
| 131. |
How is air produced in mechanical draught cooling tower? |
| A. | air tuyeres |
| B. | propeller fans |
| C. | air blowers |
| D. | louvre |
| Answer» B. propeller fans | |
| Explanation: in mechanical draught cooling tower the draught of air id produced mechanically by means of propeller fans. | |
| 132. |
Why is induced draught considered better than the forced draught? |
| A. | because power requirement is high for forced draught |
| B. | maintenance of induced draught fan is costlier |
| C. | forced draught is less efficient |
| D. | forced draught produces less amount of speed of air |
| Answer» A. because power requirement is high for forced draught | |
| Explanation: induced draught is considered to be better than forced draught because, the | |
| 133. |
Nozzles are used to control the ___________ |
| A. | temperature |
| B. | rate of flow |
| C. | mass flow rate |
| D. | none of the mentioned |
| Answer» B. rate of flow | |
| 134. |
A nozzle used to send fluid in coherent stream is called as ________ |
| A. | jet |
| B. | high velocity nozzle |
| C. | every nozzle sends fluid in coherent stream |
| D. | none of the mentioned |
| Answer» A. jet | |
| 135. |
In fountains the type of nozzle used is _______ |
| A. | none of the mentioned |
| B. | turbulent jet |
| C. | high speed nozzle |
| D. | laminar jet |
| Answer» D. laminar jet | |
| 136. |
Nozzles used in blast furnaces are called as _______ |
| A. | jet |
| B. | hot blast |
| C. | tuyeres |
| D. | none of the mentioned |
| Answer» C. tuyeres | |
| 137. |
If mach number is less than one then its flow is ______________ |
| A. | subsonic flow |
| B. | turbulent flow |
| C. | laminar flow |
| D. | none of the mentioned |
| Answer» A. subsonic flow | |
| 138. |
Nozzle used in rocket engine is __________ |
| A. | convergent nozzle |
| B. | divergent nozzle |
| C. | convergent – divergent nozzle |
| D. | none of the mentioned |
| Answer» C. convergent – divergent nozzle | |
| 139. |
In rocket engine the flow in the throat of the nozzle is __________ |
| A. | subsonic |
| B. | laminar |
| C. | turbulent |
| D. | none of the mentioned |
| Answer» A. subsonic | |
| 140. |
When mach number is greater than one the flow is ________ |
| A. | subsonic |
| B. | supersonic |
| C. | laminar |
| D. | none of the mentioned |
| Answer» B. supersonic | |
| 141. |
In rocket engines the amount of expansion in Nozzle determines the __________ |
| A. | exit temperature |
| B. | exit pressure |
| C. | exit temperature & pressure |
| D. | none of the mentioned |
| Answer» C. exit temperature & pressure | |
| 142. |
Pressure ratios below 20 are used in _____________ engines. |
| A. | steam turbine |
| B. | aero derivative engines |
| C. | heavy frame engines |
| D. | none of the mentioned |
| Answer» C. heavy frame engines | |
| 143. |
Aeroderivative engines have pressure ratios ___________ |
| A. | greater than 30 |
| B. | lesser than 30 and greater than 20 |
| C. | greater than 50 |
| D. | none of the mentioned |
| Answer» A. greater than 30 | |
| 144. |
Aeroderivative engines are used where ____________ power units are required. |
| A. | larger |
| B. | smaller |
| C. | optimum |
| D. | none of the mentioned |
| Answer» B. smaller | |
| 145. |
Gas turbines operate at pressures ________ than critical pressure ratio. |
| A. | higher |
| B. | lesser |
| C. | does not depend on pressure ratio |
| D. | none of the mentioned |
| Answer» B. lesser | |
| 146. |
Critical pressure ratio is ratios of pressures at _________ discharge. |
| A. | minimum |
| B. | none of the mentioned |
| C. | optimum |
| D. | maximum |
| Answer» D. maximum | |
| 147. |
Coefficient of velocity of nozzle is _______________ |
| A. | theoretical velocity/actual velocity |
| B. | actual velocity/theoretical velocity |
| C. | it is an experimental value |
| D. | none of the mentioned |
| Answer» B. actual velocity/theoretical velocity | |
| 148. |
Coefficient of discharge of Nozzle is _______ |
| A. | cd = cc/cv |
| B. | cd = cc*cv |
| C. | cd = cv/cc |
| D. | none of the mentioned |
| Answer» B. cd = cc*cv | |
| 149. |
Coefficient of contraction is the__________ |
| A. | ratio of actual cross sectional area to geometric cross sectional area |
| B. | ratio of geometric cross sectional area to actual cross sectional area |
| C. | ratio of pressure exerted to cross sectional area |
| D. | none of the mentioned |
| Answer» A. ratio of actual cross sectional area to geometric cross sectional area | |
| 150. |
Pressure loss occurs in nozzle due to __________ |
| A. | due to viscous force |
| B. | when fluid flows from convergent to divergent |
| C. | frictional forces |
| D. | none of the mentioned |
| Answer» C. frictional forces | |
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