Practice Test: Question Set - 25
1. If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length
- (A) ha = hl
- (B) ha = 2hl
- (C) ha = 0.5 hl
- (D) ha = 0.75 hl
2. In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
- (A) Minimum
- (B) Maximum
- (C) Zero
- (D) Infinity
3. Harmonic mean temperature difference is given by
- (A) √(ΔT1 . ΔT2)
- (B) 2 (ΔT1 . ΔT2)/(ΔT1 + ΔT2)
- (C) 2 (ΔT1 . ΔT2)/(ΔT1 - ΔT2)
- (D) (ΔT1 - ΔT2)/(ΔT1 . ΔT2)
4. Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is
- (A) In the central core
of the fluid
- (B) Uniformly distributed
throughout the fluid
- (C) Mainly confined to a
thin film of fluid near the surface
- (D) None of these
5. 200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 × 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid).
- (A) 0.5
- (B) 0.05
- (C) 0.1
- (D) 0.15
6. If Prandtl number is greater than the Schmidt number, then the
- (A) Thermal boundary
layer lies inside the concentration boundary layer
- (B) Concentration
boundary layer lies inside the thermal boundary layer
- (C) Thermal &
concentration boundary layers are of equal thickness
- (D) Hydrodynamic (i.e.,
momentum) boundary layer is thicker than the other two
7. Fourier's law of heat conduction applies to __________ surfaces.
- (A) Isothermal
- (B) Non-isothermal
- (C) Both (a) and (b)
- (D) Neither (a) and (b)
8. Thermal diffusivity is the most important in heat transfer by
- (A) Conduction
- (B) Radiation
- (C) Condensation
- (D) Natural
convection
9. Which of the following is generally considered as opaque surface towards radiations?
- (A) Gases
- (B) Solids
- (C) Liquids
- (D) Both (b) and (c)
10. LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is
- (A) 0
- (B) 1
- (C) > 1
- (D) < 1
11. Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is
- (A) Vertical heat
exchanger with steam on tube side
- (B) Vertical heat
exchanger with steam on shell side
- (C) Horizontal heat
exchanger with steam on tube side
- (D) Horizontal heat
exchanger with steam on shell side
12. The statement that "maximum wavelength of radiation is inversely proportional to the temperature" is __________ law.
- (A) Stefan-Boltzmann’s
- (B) Planck's
- (C) Wien's displacement
- (D) None of these
13. The steam ejector is used to
- (A) Remove condensate from
the steam pipelines
- (B) Create vacuum
- (C) Superheat the steam
- (D) None of these
14. Among liquids, water has a comparatively high value of thermal conductivity, due to its
- (A) Low density
- (B) High viscosity
- (C) Partial ionization
- (D) Dense structure
15. Heat flux is the time rate of heat transfer per unit
- (A) Length
- (B) Area
- (C) Volume
- (D) None of these
Next Tests: