A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness __________ metre.
0.01
0.1
0.25
0.5
Correct Answer :
B. 0.1
Related Questions
The thickness of oxide film is y at time t. If 
are the temperature dependent constants, the parabolic law of oxidation is given by
__________ is used for tying the steel columns to concrete foundation.
Grouting
Eyebolt
Anchor bolts
Refractory castables
Pick out the wrong statement.
Seam welding, projection welding & spot welding are the classification of electrical resistance welding
Electrode tip in spot welding is of copper and the tip diameter should be equal to t (where, t = plate thickness to be welded)
In spot welding, two pieces to be joined are overlapped and placed between two electrodes
Mild steel sheet cannot be spot welded
To improve the machinability of steel, it is generally subjected to
Spheroidising
Tempering
Normalising
Annealing
As per the Indian boiler regulation (IBR), the type of joint preferred for the circumferential joint is the __________ joint.
Butt
Lap
Welded
None of these
__________ is a non volatile film forming constituent of a paint.
Thinner
Dryer
Drying oil
None of these
Eutectic reaction for iron-carbon system occurs at a temperature of __________ °C.
723
959
1147
1493
Materials having __________ lattice structure are usually the most ductile.
Body centred cubic (bcc)
Hexagonal close packed (hcp)
Face centred cubic (fcc)
None of these
The most economical channel section for the fluid flow is the one for which the discharge is maximum for a given cross-sectional area. Vertical velocity distribution in an open channel for laminar flow can be assumed to be
Parabolic
Hyperbolic
Straight line
None of these
The product of a commercial direct reduction process is
Liquid iron
Solid iron
Sponge iron
Iron saturated with carbon
Principal alloying element in Elinvar (used for making hair springs for watches) is
Copper
Aluminium
Nickel
Zinc
In __________ process, there is an increase in entropy with no degradation of energy.
Isothermal expansion
Isochoric heat addition
Polytropic expansion
Isobaric heat addition
The co-ordination number in simple cubic structure is
4
6
8
12
Hooke's law
Applies to elastic deformation
Applies beyond limit of proportionality in stress-strain curve
States that stress is inversely proportional to strain upto elastic limit
None of these
An atom bomb works on the principle of
Nuclear fission
Nuclear fusion
Both the nuclear fission & fusion
Ionisation
What is the pH of distilled water?
0
1
7
14
__________ is not a heat treatment process.
Cyaniding
Parkerizing
Austempering
Martempering
Hot extrusion of aluminium is done in the temperature range of __________ °C.
550-600
450-500
350-400
250-300
__________ is the most suitable lubricant for drawing mild steel wires?
Kerosene
Water
Sodium stearate
Lime water
Use of flux during soldering is done to
Increase fluidity of solder by lowering its melting temperature
Prevent oxide formation
Wash away surplus solder
Full up the joint gap
The stress at which extension of the material takes place more rapidly as compared to the increase in load is termed as the __________ point of the material.
Elastic
Ultimate
Yielding
Breaking
Reynolds number of a fluid flowing in a circular pipe is 10,000. What will be the Reynolds number when the fluid velocity is decreased by 30% & the pipe diameter is increased by 30%?
9,100
13,000
7,000
2,550
Which of the following is the most wear resistant grade of carbide used for the cutting tools?
Aluminium carbide
Tungsten carbide
Nickel carbide
Iron carbide
When the wet steam is throttled but still remains wet at the exit of the throttle valve, then its temperature & dryness fraction respectively
Decreases & increases
Increases & increases
Increases & decreases
Decreases & decreases
The noble metals
Are exemplified by Na, K and Li
Do not resist corrosion very strongly
Are the lowermost in the electro-chemical series of metals
None of these
Which of the following is not an ore of copper?
Cryolite
Azurite
Chalcopyrite
Malachite
Minimum thermal efficiency of a steam boiler may be around __________ percent
25
45
65
20
Vibration upto 100 kilo hertz can be most accurately measured by a __________ type accelerometer.
Preloaded spring
Piezoelectric
Bonded strain gauge
None of these
Metalloids
Are good conductor of heat & electricity
Act as electron donors with metals & as electron acceptor with non-metals
Are not necessarily solids at room temperature
Are compounds that exhibit both metallic & non-metallic properties to some extent and are exemplified by elements like germanium, silicon & boron
Transformation range for ferrous material is the temperature interval during which __________ is formed during its heating.
Cementite
Austenite
Martensite
Pearlite