In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C.
20
60
120
∞
Correct Answer :
D. ∞
Related Questions
Ferromagnetic materials owe their properties to __________ inner sub-shells.
Completely filled
Partially filled
Equally filled
Vacant
__________ are normally subjected to sub-zero treatment.
Highly stressed parts
Gauges or precision parts
Cold rolled sheets
Non machinable materials
Increasing the carbon content of steel
Reduces the upper shelf energy
Increasing the ductility transition temperature
Decreases brittleness
Decreases hardness
Powder metallurgy technique is used in the production of __________ tools.
Tungsten carbide
High carbon steel
High speed steel
Drilling
Material of construction of the electrode used in the electric resistance welding is
Stainless steel
Graphite
Copper
Steel
Natural water contains approximately __________ percent of heavy water.
0.015
0.71
1.2
3.5
Which of the following is prone to cup and cone fracture?
Cast iron
Soft brass
Round specimen of ductile metal
Flat tensile specimen of ductile metal
Babbitt lining is used on brass/bronze bearings to increase the
Antifriction properties
Compressive strength
Bearing resistance
Wear resistance
Circular cross section machine parts which are symmetrical about the axis of rotation are made by hot
Piercing
Spinning
Drawing
Extrusion
A dummy activity is used in PERT network to describe the
Precedence relationship
Resource idleness
Resource restriction
Necessary time delay
Function of gear box is to
Reduce the speed
Obtain variable speed
Increase the speed
Produce high torque
Which of the following terminology is used for the temperature at which new grains are formed in a metal?
Eutectic temperature
Lower critical temperature
Recrystallisation temperature
Upper critical temperature
Even though heat transfer co-efficient in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling.
Film
Nucleate
Transition
All modes of
Plants produce carbohydrates from the CO2 present in the atmosphere by
Polymerisation
Photochemical reaction
Oxidation
None of these
Specific gravity of a metal, which weighs 5 kg in air and 4 kg when submerged in water, will be
5
1.25
2.5
3.75
__________ is not used as a material of construction in thermocouples.
Alumel
Rhodium
Constantan
Duralumin
Cold cracking in the heat affected zone of a high strength steel weld can take place because of the
Retained austenite
Martensite formation
Relatively high sulphur content in the base metal
Sufficient hydrogen present in the welding arc
The most prominent single cause of corrosion in boiler-tubes, drums, economisers and steam superheaters in a thermal power plant boiler is the
Water alkalinity & leakage
Hydrazine addition during feed water treatment
Release of non-condensable gas from water in the boiler
Scale formation
The usual energy consumption in electric arc furnace steel making is __________ KWh/ton of steel.
60 - 100
400 - 700
1200 -1500
2000 - 2300
Otto cycle used in spark ignition petrol engines is also known as the constant __________ cycle.
Volume
Pressure
Heat
None of these
Which of the following pairs is not correctly matched?
Uranium - 233 : Fertile material
Binding energy : Mass defect
Scattering: Absorption cross-section
Number of nucleons : Mass number
The starting of a car takes time in winter, because the
Octane number of fuel is decreased
Fuel supply for ignition is not sufficient
Vaporisation of the fuel is decreased
Pour point of fuel decreases
In a forced draft cooling tower, water is cooled from 95 to 80°F by exposure to air with a wet bulb temperature of 70°F. In this case, the
Range is 15°F
Approach is 10°F
Both (A) & (B)
Neither (A) nor (B)
The 'laughing gas' is
Nitrous oxide
Nitric oxide
Nitrogen trioxide
Nitrogen pentoxide
Young's modulus of a material is the measure of its
Stiffness
Malleability
Creep resistance
Tensile strength
Large diameter reinforced cement concrete (RCC) pipes are generally joined by __________ joint.
Flanged iron
Collar
Flexible
Expansion
Which of the following hardness tests does not measure the indentation hardness of metals and alloys?
Vickers hardness test
Shore scleroscope test
Brinell hardness test
Rockwell hardness test
Normalising of a casting does not
Induce stresses in it
Refine its grain structure
Reduce segregation
Improve its mechanical properties
Carbon supply in pack carburising process is in the form of
Charcoal
Calcium carbide
Hydrocarbon oil
Graphite
Name the safety device used to protect the boiler, when the water level falls below a minimum level.
Blow down valve
Blow off cock
Fusible plug
Safety valve