In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by___________________?
(A) convection
(B) radiation
(C) conduction
(D) both convection and conduction
(D) none of the above
Total emissivity of polished silver compared to black body is___________________?
(A) same
(B) higher
(C) more or less same
(D) very much lower
(D) very much higher
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
(D) Kirchhoff’s law
The unit of overall coefficient of heat transfer is___________________?
(A) kcal/m2
(B) kcal/hr °C
(C) kcal/m2 hr °C
(D) kacl/m hr °C
(D) kcal/m3 hr °C
All radiations in a black body are___________________?
(A) reflected
(B) refracted
(C) transmitted
(D) absorbed
(D) partly reflected and partly absorbed
According to Kirchoff’s law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a _________________?
(A) grey body
(B) brilliant white polished body
(C) red hot body
(D) black body
(D) none of the above
Joule sec is the unit of_________________?
(A) universal gas constant
(B) kinematic viscosity
(C) thermal conductivity
(D) Planck’s constant
(D) none of the above
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
(D) convection and radiation
In counter flow heat exchangers_________________?
(A) both the fluids at inlet (of heat ex¬changer where hot fluid enters) are in their coldest state
(B) both the fluids at inlet are in their hot¬test state
(C) both the fluids .at exit are in their hottest state
(D) one fluid is in hottest state and other in coldest state at inlet
(D) any combination is possible depending on design of heat exchanger
Fourier’s law of heat conduction is valid for_________________?
(A) one dimensional cases only
(B) two dimensional cases only
(C) three dimensional cases only
(D) regular surfaces having non-uniform temperature gradients
(D) irregular surfaces