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.Management Sciences
Category: Heat Transfer
In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by ________________?
A. hr (time)
B. sqm (area)
C. °C (temperature)
D. cm (thickness)
E. kcal (heat).
The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as ________________?
A. emissivity
B. transmissivity
C. reflectivity
D. intensity of radiation
E. absorptivity
Moisture would find its way into insulation by vapour pressure unless it is prevented by __________________ ?
A. high thickness of insulation
B. high vapour pressure
C. less thermal conductivity insulator
D. a vapour seal
E. all of the above
Which of the following has least value of conductivity_________________?
A. glass
B. water
C. plastic
D. rubber
E. air
Thermal conductivity of solid metals with rise in temperature normally___________________?
A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. unpredictable
The value of the wavelength for maximum emissive power is given by ___________________?
A. Wien’s law
B. Planck’s law
C. Stefan’s law
D. Fourier’s law
E. Kirchhoff’s law
Absorptivity of a body will be equal to its emissivity___________________?
A. at all temperatures
B. at one particular temperature
C. when system is under thermal equi-librium
D. at critical temperature
E. for a polished body
The concept of overall coefficient of heat transfer is used in case of heat transfer by________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation
Unit of thermal diffusivity is_________________?
A. m2/hr
B. m2/hr°C
C. kcal/m2 hr
D. kcal/m.hr°C
E. kcal/m2 hr°C
Metals are good conductors of heat because________________?
A. their atoms collide frequently
B. their atoms-are relatively far apart
C. they contain free electrons
D. they have high density
E. all of the above
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