|
1) For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it__________________? a. Decreases the pressure drop b. Decreases the outlet temperature of cooling medium c. Increases the overall heat transfer coefficient d. None of these
|
||||
|
2) Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ? a. 35.5 b. 43.75 c. 81.25 d. 48.25
|
||||
|
3) A graph between _____________ is called Wilson plot? a. (1/U) Vs. (1/v0.8) b. (1/v0.8) Vs. U c. v0.8 Vs . U d. (1/U) Vs. (1/V)
|
||||
|
4) For a laminar flow of fluid in a circular tube, ‘h1’ is the convective heat transfer co-efficient at velocity ‘V1’. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is________________? a. 1.26 h1 b. 0.794 h1 c. 0.574 h1 d. 1.741 h1
|
||||
|
5) Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ? a. U1 – U2 b. 1/U1 – 1/U2 c. 1/U2 – 1/U1 d. U2 – U1
|
||||
|
6) All analogy equations connecting friction factor and heat transfer co-efficient apply only to ___________________? a. Wall or skin friction b. Form friction c. Both A. and B. d. Turbulent flow
|
||||
|
7) Reason for operating an evaporator in multiple effects is to secure ___________________? a. Increased steam economy b. Decreased steam consumption c. Both A. and B. d. Increased capacity
|
||||
|
8) Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the_________________? a. Existence of thermal boundary layer b. Temperature gradient produced due to density difference c. Buoyancy of the bubbles produced at active nucleation site d. None of these
|
||||
|
9) Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer? a. Grashoff b. Reynolds c. Both ‘a’ & ‘b’ d. Prandtl & Grashoff
|
||||
|
10) In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is _____________ the outlet temperature of the cold fluid? a. Equal to b. More than c. Less than d. Either more or less than (depending upon the fluid)
|
||||
|
11) Evaporator tubes are generally_____________________? a. Horizontal b. Vertical c. Inclined d. Random
|
||||
|
12) Which of the following is the most widely used heat insulating material for pipelines carrying steam ? a. Tar dolomite bricks followed by asbestos b. Fireclay refractory followed by aluminium sheet c. Cotton followed by aluminium foil d. 85% magnesia cement and glass wool
|
||||
|
13) If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows _____________ law? a. Parabolic b. Hyperbolic c. Linear d. Logarithmic
|
||||
|
14) Grashoff number is given by________________? a. gD3.β.Δtρ2/μ2 b. gD2βΔtρ/μ2 c. gD2βΔtP2μ d. gD3βΔtP2/μ
|
||||
|
15) In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid___________________? a. Varies directly as the area and the LMTD b. Directly proportional to LMTD and inversely proportional to the area c. Varies as square of the area d. None of these
|
||||
|
16) For what value of Prandtl number, St = f/2 ? a. 1.5 b. 1 c. > 1 d. < 1
|
||||
|
17) Heat sensitive materials can be concentrated in an evaporator employing_______________? a. Vacuum b. High pressure c. High residence time d. None of these
|
||||
|
18) LMTD can’t be used as such without a correction factor for the_________________? a. Multipass heat exchanger b. Baffled heat exchanger c. Condensation of mixed vapour in a condenser d. All A. B. and C.
|
||||
|
19) Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.)? a. x/KA b. KA/x c. K/Ax d. A/Kx
|
||||
|
20) Heat flux, as defined in heat flow is analogous to _______________ in electricity flow? a. Current b. Voltage c. Resistance d. None of these
|
||||
|
21) The driving potential for the crystal growth during crystallisation is the _______________ of the solution? a. Concentration b. Viscosity c. Super-saturation d. Density
|
||||
|
22) In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ? a. Once b. Twice c. Thrice d. Four times
|
||||
|
23) With increase in temperature, the thermal conductivity of most liquids_________________? a. Increases b. Decreases c. Remain same d. First increases upto a certain temperature and then becomes constant
|
||||
|
24) 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
|
||||
|
25) The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________? a. Heat flux b. Nusselt number c. Prandtl number d. Schmidt number
|
||||
|
26) For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is______________? a. Nu = 0.023 Re0.8. Pr0.4 b. Nu = (π/2) Gz c. Nu = (2/π) Gz d. Nu = 2Gz0.5
|
||||
|
27) In a forward feed multiple effect evaporator, the pressure is ____________________? a. Highest in last effect b. Lowest in last effect c. Same in all effects d. Dependent on the number of effects
|
||||
|
28) “The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium”. This is ______________ law? a. Kirchoff’s b. Planck’s c. Wien’s displacement d. Stefan-Boltzmann
|
||||
|
29) Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ? a. Square pitch b. Triangular pitch c. Diagonal square pitch d. None of these
|
||||
|
30) A multiple effect evaporator as compared to a single effect evaporator of the same capacity has _________________? a. Lower heat transfer area b. Lower steam economy c. Higher steam economy d. Higher solute concentration in the product
|
||||
