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Absorptivity and reflectivity of a perfect black body are respectively _______________?
Related MCQs
Water is normally used as a coolant in the heat exchange equipments mainly because of its__________?
Stefan-Boltzmann law applies to __________ body?
A BTU/hr.ft.2 °F is equal to__________?
A __________ evaporator employs an annular downtake?
With increase in temperature, the thermal conductivity of fresh lubricating oil __________?
To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is __________?
In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?
For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone?
Terminal point temperature differences between fluids in case of a heat exchanger is termed as__________?
A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when__________?
Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then__________?
Maximum heat transfer rate is achieved in __________ flow?
Radiator of an automobile engine is a __________ type of heat exchanger?
In forced convection, the Nusselt number is a function of __________?
In a shell and tube type heat exchanger, the floating tube bundle heat arrangement is used__________?
The Stefan-Boltzmann constant depends on the__________?
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it__________?
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes?
Electro-magnetic spectrum range, which is important for radiation varies from __________ microns?
In a gas-liquid shell and tube heat exchanger, the__________?
In a shell and tube heat exchanger, square pitch compared to triangular pitch__________?
Planck’s distribution law is valid for __________ bodies?
Steam trap is used to__________?
LMTD for counter-flow and parallel flow heat exchanger will be the same, when the__________?
Vent pipes are provided in a condenser to __________?
The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is__________?
The equation, Nst = (f/2)/[1 + 5 (Npr – 1) √(f/2)], corresponds to __________ analogy?
Open pan evaporators are preferred to be used, when the solution to be concentrated is__________?
When warm and cold liquids are mixed, the heat transfer is mainly by__________?
At constant temperature, the thermal conductivities of gases __________ with rise in pressure?
A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of__________?
It is not preferable to use superheated steam in evaporators, because of its very__________?
__________ heat exchanger is used for chilling oil to be dewaxed?
If heat transfer rate varies with the time, it is termed as__________?
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-2is__________?
The absorptivity of a body is equal to its emissivity __________?
A perfect black body is a perfect __________ of radiation?
jH factor for heat transfer depends upon the __________ number?
The actual temperature drop across the heating surface of an evaporator depends on the__________?
Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is__________?
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because__________?
Which of the following has the lowest overall heat transfer co-efficient ?
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator ?
The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation?
In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used to calculate the heat transfer rate?
The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are__________?
One kilogram of water at 0°C is changed to superheated steam of one atm pressure and 300° C. The major heat consumption in the process will be to__________?
A sphere of radius ‘R1’ is enclosed in a sphere of radius ‘R2’. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is __________?
Solid angle subtended by the finite surface at the radiating element is__________?
Corrosiveness of steam condensate is due to the presence of__________?
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)?
Absorptivity and reflectivity of a perfect black body are respectively _______________?
A. 1 and 0
B. 0 and 1
C. 1 and ∞
D. 0 and 0.5
Correct Answer:
1 and 0
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Last Updated:
March 03, 2019