In a furnace employing forced draught as compared to induced draught,
(A) Air is sucked in, so air leaks are more and hence the furnace efficiency is
reduced
(B) The fan operates hot and hence blades are liable to corrosion and erosion
(C) Positive pressure exists in the furnace
(D) None of these

1 Answer

Answer :

(C) Positive pressure exists in the furnace

Related questions

Description : Differentiate induced draft and forced draft cooling towers based on (i) Location of fan (ii) Corrosion of blades (iii) Efficiency (iv) Fan size

Last Answer : Differentiate induced draft and forced draft cooling towers based on (i) Location of fan (ii) Corrosion of blades (iii) Efficiency (iv) Fan size

Description : Artificial draught produced by a fan in the furnace can be controlled by the (A) Speed of the fan (B) Damper (C) Variation in the pitch of fan blades (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Ingress of cold air in the furnaces through cracks, charging doors, openings etc (A) Reduces the flue gas temperature and makes the furnace atmosphere oxidising (B) Increases the load on the induced draft fan (C) Reduces the furnace draught (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Pick out the wrong statement pertaining to the cooling towers. (A) In case of induced draft cooling tower, the fan is placed at the top of the tower (B) Effectiveness of ... Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature

Last Answer : (D) Effectiveness of a mechanical draft cooling tower is reduced with increase in air wet-bulb temperature

Description : 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

Last Answer : Because power requirement is high for forced draught

Description : Which of the following is used to produce draught in the locomotive boilers? (A) Chimney (B) Induced draught fan (C) Forced draught fan (D) Steam jet arrangement

Last Answer : Option D

Description : Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly ash discharge from the stack (C) Higher power consumption in its transportation (D) Erosion of induced draft fan blades

Last Answer : (A) Ash disposal problem

Description : Which of the following is the most important deterrents to an extended use of pulverised coal in boiler firing? (A) Ash disposal problem (B) Excessive fly-ash discharge from the stack (C) High power consumption in its transportation (D) Erosion of induced draft fan blades

Last Answer : (A) Ash disposal problem

Description : Power required in case of forced draught as compared to induced draught (for the same draught produced) is (A) Same (B) Less (C) More (D) Either more or less; depends on the flue gas density

Last Answer : (B) Less

Description : Furnace oil consumption in a furnace for a given duty employing preheated combination air (at 300°) may be reduced by about __________ percent as compared to the use of atmospheric combustion air. (A) 5 (B) 10 (C) 20 (D) 35

Last Answer : (C) 20

Description : Artificial draught produced by a fan can be controlled by the (A) Speed of the fan (B) Damper (C) Variation in the pitch of the fan blades (D) All (A), (B) and (C

Last Answer : (D) All (A), (B) and (C

Description : Which of the following accentuates clinkering trouble on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportions of iron & sulphur (B) Low forced draught and fuel bed temperature (C) Thick fire bed and preheated primary air (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Which one is not an induced draught furnace? (A) Blast furnace stove (B) Sintering furnace (C) High pressure boiler (D) None of these

Last Answer : (A) Blast furnace stove

Description : Noise produced by cooling fans (employed in air cooled heat exchangers or cooling tower) is mainly caused due to the turbulence created by blade passage through air. It can be reduced by use of a slower fan (A) With greater ... (B) Of increased diameter (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

Description : Define natural, mechanical, forced and induced draught systems.

Last Answer : Natural draught system: - When the fuel is burnt (combustion) in the furnace due to natural circulation of air, the draught is called natural draught. Mechanical draught system: -  In a mechanical ... combustion. OR If fan/blower is placed after the furnace then it is called as induced draught

Description : Thermal efficiency of furnaces can be improved by (A) Waste heat recovery from flue gas (B) Minimising heat losses from furnace walls (C) Maintaining proper draught (D) All (A), (B) and (C

Last Answer : (D) All (A), (B) and (C

Description : Ferric stainless steels compared to austenitic stainless steels (A) Have lower corrosion resistance (B) Are harder to fabricate (C) Are less ductile and hence less suitable for cold pressing (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Flue gas from the heating chamber of byproduct coke ovens is removed by (A) Forced draft fan (B) Induced draft fan (C) Steam ejector (D) Natural draft

Last Answer : (D) Natural draft

Description : Test specimen for determination of refractoriness under load (RUL) of a refractory is heated in a (A) Furnace employing neutral atmosphere (B) Carbon resistance furnace (C) Reducing atmosphere (D) Furnace employing negative pressure

Last Answer : (B) Carbon resistance furnace

Description : Combustion of pulverised coal compared to the lumpy coal (A) Provides better control of furnace temperature (B) Facilitates combustion with lower excess air (C) Provides higher thermal efficiency & flame temperature (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

Description : In a heat treatment shop, steel components are heat-treated in batches of 80 Tons. The  heat treatment cycle is as follows;  Increase temperature from 30 OC to 850 OC in 3 hours.  ... efficiency of 80%, for same requirement. The investment towards installation of  the new furnace is Rs. 50

Last Answer : Quantity of steel treated per batch - 80 Tons a. Efficiency of Furnace: Useful heat supplied to steel - 80000 x 0.12 x (850 - 30)   = 7872000 kcal/batch .1 mark Total heat ... = Rs. 64400/batch Efficiency of new LPG furnace - 80% Heat supplied in new LPG furnace - 7872000/0.8

Description : The following heat engine produces power of 100,000 kW. The heat engine operates between 800 K and 300 K. It has a thermal efficiency equal to 50% of that of the Carnot engine for the same temperature. The rate at which heat is ... is (A) 100,000 kW (B) 160,000 kW (C) 200,000 kW (D) 320,000 kW

Last Answer : (D) 320,000 kW

Description : A coal having high ratio of volatile matter to fixed carbon as compared to a coal having low ratio of volatile matter to fixed carbon (A) Is less liable to spontaneous combustion on storage (B) ... a shorter flame (C) Requires smaller combustion space and less secondary air (D) None of these

Last Answer : (D) None of these

Description : Furnace pressure is normally controlled by regulating the (A) Air pressure (B) Fuel gas pressure (C) Speed of I.D. fan (D) Damper

Last Answer : (D) Damper

Description : Wrought iron is (A) High carbon iron (B) Highly resistance to acid corrosion (C) Malleable & ductile; and hence is used for chain links, hooks & couplings (D) An alloy of iron, chromium & carbon

Last Answer : (C) Malleable & ductile; and hence is used for chain links, hooks & couplings

Description : During the manufacture of sulphuric acid, the temperature of molten sulphur is not increased beyond 160°C, as (A) It is very corrosive at elevated temperature (B) Its viscosity is not reduced on ... be further reduced) (C) It decomposes on further increasing the temperature (D) None of these

Last Answer : (B) Its viscosity is not reduced on further heating (hence pressure drop on pumping it, cannot be further reduced)

Description : Pick out the wrong statement. (A) Dry process is used for the manufacture of cement, when the raw material is blast furnace slag (B) Portland cement is made employing wet process (C) Gypsum is added to Portland cement to lengthen its setting time (D) None of these

Last Answer : (D) None of these

Description : What Are The Advantages Of Forced Draught System?

Last Answer :  Since the fan handles cold air, the fan size and the power required are less.  No need of water cooled bearings because the air being handled is cold air,  Pressure throughout the system is above atmospheric pressure so the air leakage into the furnace is reduced.

Description : Write About Forced Draught System?

Last Answer : In this system, the blower (forced draft fan) is located at the base of the boiler near the grate. Air is forced to the furnace by forced fan and the flue gases are forced to chimney through economizer and air preheater.

Description : Differentiate between natural draught and forced draught cooling tower.

Last Answer : Sr. No. Natural draught Forced draught 1 The air flows naturally without fan through tower and provides required cooling Fan is located at the top of the tower and enters the ... from tower cannot be controlled. The temp. of water coming out from tower can be controlled.

Description : Write the elements of forced draught cooling tower.

Last Answer : Following are the elements of forced draught cooling tower; a) Forced draught fan b) Eliminator c) Spray header d) Spray nozzle e) Circulating pump

Description : How The Induced Draught Is Working?

Last Answer : In an induced draught system, a blower (induced draft fan) is placed near (or) at the base of the chimney. The fan sucks the flue gas from the furnace creating a partial vacuum inside the ... aid the combustion of fuel. The flue gases drawn by the fan passes through chimney, to the atmosphere.

Description : When the temperature and humidity of air is low, we usually use __________ draft cooling tower. (A) Natural (B) Forced (C) Induced (D) None of these

Last Answer : (A) Natural

Description : The draught may be produced by a_________ a) Chimney b) Mechanical fan c) Steam jet d) All of the above

Last Answer : d) All of the above

Description : The draught in locomotive boilers is produced by a ___________ a) Chimney b) Centrifugal fan c) Steam jet d) All of the above

Last Answer : c) Steam jet

Last Answer : In a ceiling fan employing capacitor run motor secondary winding surrounds the primary winding.

Description : Which of the following accentuates clinkering troubles on furnace grate burning coal? (A) Low reactivity of carbonised residue containing high proportion of iron & sulphur (B) Low forced draft & fuel bed temperature (C) Thick firebed and preheated primary air (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Dust content in raw blast furnace gas is about __________ gm/Nm3 ; hence it is cleaned to the dust level of about < 10 mg /Nm3 before use. (A) 15-30 (B) 1-2 (C) 70-100 (D) 150-200

Last Answer : (A) 15-30

Description : Moist atmospheric air at high temperature (e.g., in summer) having high concentration of sulphur dioxide causes (A) Fading of dyes on textiles (B) Corrosion, tarnishing & soiling of metals (C) Reduced strength of textiles (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Induced draft fans provided in large thermal power plant boilers have __________ blades. (A) Forward curved (B) Backward curved (C) Double curved (D) Radial or straight

Last Answer : (B) Backward curved

Description : For maximum discharge through a chimney, its height should be (A) 200 meters (B) Infinitely long (C) More than 105.7 metres (D) Equal to the height of the hot gas column producing draught

Last Answer : (D) Equal to the height of the hot gas column producing draught

Description : Find false statement about effect of sulphur in fuel? (A) It has heating value (B) It helps in electrostatic precipitation of ash in flue gases (C) It leads to corrosion of air heaters, ducting, etc. if flue gas exit temperature is low (D) It erodes furnace walls

Last Answer : (D) It erodes furnace walls

Description : Which furnace employs an I.D. fan for the removal of flue gases from the furnace? (A) Coke oven (B) Blast furnace stoves (C) Beehive coke oven (D) High pressure boiler

Last Answer : (D) High pressure boiler

Description : Why the electric motor of a fan with backward curved blades is never got overloaded under any condition ?

Last Answer : The maximum power is consumed at about 70% of maximum flow in case’of fan with backward blades. For higher flow, power consumption gets lower.

Description : Corrosion is (A) A physical phenomenon (B) A chemical phenomenon (C) Same as erosion (D) An uncontrollable phenomenon

Last Answer : Option B

Description : Damage to metal surface by mechanical action is called (A) Pitting (B) Corrosion (C) Erosion (D) None of these

Last Answer : Option C

Description : An automobile tire has a gauge pressure of 200 kpa at 0°C assuming no air leaks and no change of volume of the tire, what is the gauge pressure at 35ºC.  a. 298.645  b. 398.109  c. 291.167  d. 281.333 Pg = Pabs - Patm

Last Answer : 298.645

Description : The efficiency of the plant _____ with the mechanical draught a) Increases b) Decreases c) Remain constant d) None of the above

Last Answer : a) Increases

Description : If Apple Computers measured and evaluated the quality of its goods, services, and processes as compared with those of the best -performing companies in the computer industry, it would be employing A)uniform commitment to quality marketing. B)external marketing. C)quality marketing. D)benchmarking.

Last Answer : D)benchmarking.

Description : The most efficient cooling tower out of the following is (A) Induced draft (B) Forced draft (C) Natural draft (D) Atmospheric

Last Answer : (A) Induced draft