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 of the above
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The amount of combustible escaping uncon-sumed from the furnace, depends upon the
A. Air supplied and furnace temperature
B. Burner design (thoroughness of mixing versus stratification)
C. Air preheat and the flow of gases in the furnace (mixing by induction, by acceleration or by change of direction)
D. All of the above
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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
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Which is the most thermally efficient furnace?
A. Reheating furnace
B. Reverberatory furnace
C. Rotary kilns
D. Boiler furnace
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In a heating process, a heat flow diagram in which the quantities of heat in the various items of a heat balance are represented by the width of a band is called the
A. Ostwald chart
B. Cox chart
C. Sankey diagram
D. None of these
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An improved and fuel efficient version of the pusher type reheating furnace is the __________ furnace.
A. Walking beam
B. Shaft
C. Tunnel
D. Rotary hearth
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Which of the following variables affects the furnace capacity?
A. Temperature of flue gas
B. Thermal conductivity of stock
C. Thickness of heating stock
D. All of the above
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Air filtration in a furnace
A. Reduces its thermal efficiency
B. Is indicated by flame sting out
C. Increases the flue gas temperature
D. None of these
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In case of pulverised coal fired steam boiler, the secondary air serves the main purpose of
A. Transportation of coal
B. Drying of coal
C. Combustion of coal by supplying it around the burner
D. Preheating the primary air
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If the flame is produced under the hearth and then sweeps up into the heating chamber, this is called a/an __________ furnace.
A. Sidefired
B. Underfired
C. Covered
D. Recirculating
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Oxygen percentage in the flue gas coming out of a gaseous fuel fired furnace should be ideally about __________ percent.
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Hearth furnaces are not used for
A. Roasting
B. Melting
C. Reheating
D. None of these
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The thermal efficiency of an air/fuel gas preheating recuperator may be as high as __________ percent.
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The heating capacity of continuous reheating furnace depends upon the
A. Hearth area and furnace temperature
B. Emissivity of the stock
C. Ratio of wall surface to stock surface
D. All of the above
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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 of the above
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If fuel and air are mixed ahead of the burner, it is called a/an __________ burner.
A. Premix
B. Outside mixing type
C. Rotary
D. Diffusion
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Out of the following fuels used in a furnace exhausting flue gas at a temperature of 600°C, the percentage stack loss will be maximum in case of complete combustion of
A. Furnace oil with air
B. Furnace oil with oxygen
C. Blast furnace gas with air
D. Blast furnace gas with oxygen
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Protective gas used in the annealing furnace for steel coil comprises of
A. 95% N2 + 5% H2
B. 5% H2 + 95% N2
C. 100% CO
D. 100% H2
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__________ furnace is not an electric furnace.
A. Arc
B. Induction
C. Pot
D. Resistance
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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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