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.Management Sciences
Category: Chemical Heat Transfer
The Stefan-Boltzmann constant depends on the_________________?
0
A. Medium
B. Temperature
C. Surface
D. None of these
Thermal conductivity of a gas at low density, ___________ with increase in temperature ?
A. Decreases
B. Increases
C. Remains unchanged
D. May increase or decrease; depends on the gas
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) _________________?
A. ∝ t
B. ∝ 1/t
C. ∝ √t
D. Independent of ‘t’
The film co-efficient between condensing vapour and metal wall increases with _____________________?
A. Increasing temperature of the vapour
B. Decreasing temperature of the vapour
C. Increasing viscosity of the film of condensate
D. Increasing temperature drop
Grashoff number, which is defined as g . β (Ts – T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to ____________ force?
A. Viscous
B. Elastic
C. Inertial
D. None of these
When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is _______________?
A. Free convection
B. Entry length problem in laminar forced conduction (developing thermal boundary layer)
C. Mixed convection (both free and forced)
D. Forced convection
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) ?
A. (ΔT)2
B. (ΔT)4
C. (ΔT)3
D. √(ΔT)
Loss of heat from untagged steam pipe to the ambient air is by __________________?
A. Conduction
B. Convection
C. Radiation
D. All A., B. & C.
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