Forced recirculation of furnace gases is practised (A) To increase heat transfer by convection (B) To ensure uniform temperature (C) In furnaces, operating below 750°C (D) All (A), (B) and (C)

Forced recirculation of furnace gases is practised
(A) To increase heat transfer by convection
(B) To ensure uniform temperature
(C) In furnaces, operating below 750°C
(D) All (A), (B) and (C)
by

1 Answer

Answer :

(D) All (A), (B) and (C)
by

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reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity (C) Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

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Pick out the wrong statement. (A) Different solids have different equilibrium moisture curves (B) Total condenser or reboiler is considered equivalent to one theoretical plate in McCabe-Thiele method of theoretical plate calculation for distillation column (C) Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column (D) Even a forced draft cooling tower cannot cool water below the wet bulb temperature

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Oxygen enrichment of combustion air does not result in increase of the (A) Flame temperature (B) Oxygen in the flue gas (C) Stack loss (D) Heat transfer rate in the furnace

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LSHS is a type of furnace oil, which (A) Is more viscous than high viscosity furnace oil (HVFO) (B) Stands for low sulphur heavy stock (C) Is an ideal fuel for metallurgical furnaces due to its lower sulphur content (< 1%(D) All (A), (B) and (C))

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Which of the following furnaces will have maximum thermal efficiency? (A) Soaking pits (B) Walking beam reheating furnace (C) Boiler furnace (D) Rotary kilns

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In reverberatory furnace, charge is heated mainly by (A) Conduction (B) Natural convection (C) Radiation of heat from the roof of the combustion chamber (D) None of these

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In salt bath furnace, heat is transferred to the charge mainly by (A) Conduction (B) Convection (C) Radiation (D) None of these

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The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as (A) (ΔT) 1/4 (B) (ΔT) 1/2 (C) (ΔT) 5/4 (D) (ΔT) 3/4

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Heat transfer occurs by natural convection because change in temperature causes difference in (A) Viscosity (B) Density (C) Thermal conductivity (D) Heat capacity

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Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the (A) Existence of thermal boundary layer (B) Temperature gradient produced due to density difference (C) Buoyancy of the bubbles produced at active nucleation site (D) None of these

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Last Answer : (D) None of these

Means for giving direction to the circulation of gases in furnaces are (A) Fans (B) Arrangement of heating stock in the furnaces (C) Location of outlet ports and heating & combustion devices (D) All (A), (B) and (C)

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

Design of waste heat boiler for recovery of waste heat from furnace gases depends upon the(A) Quantity & temperature of waste gas(B) Dust concentration & nature of dust in waste gas(C) Corrosive nature of the waste gas(D) All (A), (B) and (C)

Description : Design of waste heat boiler for recovery of waste heat from furnace gases depends upon the (A) Quantity & temperature of waste gas (B) Dust concentration & nature of dust in waste gas (C) Corrosive nature of the waste gas (D) All (A), (B) and (C)

Last Answer : (B) Dust concentration & nature of dust in waste gas

Which is not accomplished in an underfired furnace? (A) Increase in heating capacity/m2 of floor space (B) Elimination of cold spot at the bottom of the charge (C) Reduction in the temperature of furnace gases (D) Protection of the periphery of the charge from excessive radiation

Description : Which is not accomplished in an underfired furnace? (A) Increase in heating capacity/m2 of floor space (B) Elimination of cold spot at the bottom of the charge (C) Reduction in the temperature of furnace gases (D) Protection of the periphery of the charge from excessive radiation

Last Answer : (A) Increase in heating capacity/m2 of floor space

The type of pump used for the recirculation of molten sodium coolant in liquid metal cooled reactor is a/an __________ pump. (A) Electromagnetic (B) Reciprocating (C) Centrifugal (D) Volute

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Last Answer : (A) Electromagnetic

In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ?

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Last Answer : Get doubled.

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)

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

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)

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

. The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C-1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2 .°C-1 . The rate of heat loss from the outer surface in W.m-2 is (A) 165.4 (B) 167.5 (C) 172.5 (D) 175

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Heat transfer rate to the charge/stock in a furnace does not depend upon the (A) Type of fuels viz. solid, liquid or gaseous (B) Flue gas temperature (C) Emissivity of refractory walls (D) Initial temperature of the charged stock

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In a muffle furnace, the muffle (A) Retards the heat transfer (B) Assists in temperature equalisation in the charge (C) Permits the use of controlled atmosphere for the protection of stock (D) All (A), (B) and (C)

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