Thursday, January 28, 2021

GATE Chemical Engineering Questions and Answers-Fluid Mechanics

Match the following for a centrifugal pump with impeller speed n

P Capacity             (1) proportional to n

Q Head                 (2) proportional to n2

(3) proportional to n3

(A)       P-2, Q-1

(B)       P-1, Q-3

(C)       P-2, Q-3

(D)       P-1, Q-2

                                                                                                                  GATE 2006

            Answer:          (D)

 

The magnitude of the force (in N) required to hold a body of volume 0.05 m3 and mass 40 kg in water (density 1000 kg/m3) at a depth of 0.1 m is (g = 9.81 m/s2)

(A)       Zero

(B)       98.1

(C)       490.5

(D)       882.9

                                                                                                                  GATE 2006

            Answer:          (B)

 

A liquid is pumped at the flow rate Q through a pipe of length L. The pressure drop of the fluid across the pipe is ΔP. Now a leak develops at the mid-point of the length of the pipe and the fluid leaks at the rate of Q/2. Assuming that the friction factor in the pipe remains unchanged, the new pressure drop across the pipe for the same inlet flow rate (Q) will be

(A)       (1/2) ΔP

(B)       (5/8) ΔP

(C)       (3/4) ΔP

(D)       ΔP

                                                                                                                  GATE 2006

            Answer:          (B)

 

In a laminar flow through a pipe of radius R, the fraction of the total fluid flowing through a circular cross-section of radius R/2 centered at the pipe axis is

(A)       3/8

(B)       7/16

(C)       1/2

(D)       ¾

                                                                                                                  GATE 2006

            Answer:          (B)

 

A fluid obeying the constitutive equation

GATE 2006

is held between two parallel plates a distance d apart. If the stress applied to the top plate is 3τ0, then the velocity with which the top plate moves relative to the bottom plate would be

GATE 2006

                                                                                                            GATE 2006

            Answer:          (C)

 

A bed fluidized by water is used for cleaning sand contaminated with salt. The particles of sand and salt have the same shape and size but different densities (ρsand = 2500 kg/m3 and ρsalt  = 2000 kg/m3). If the initial volume fraction of the salt in the mixture is 0.3 and if the initial value of the minimum fluidization velocity (Umf) is 0.9 m/s, find the final value of the Umf (in m/s) when the sand is washed free of the salt Assume that the bed characteristics (bed porosity and solid surface area per unit volume) do not change during the operation and that the pressure drop per unit length is directly proportional to the fluid velocity

(A)       0.70

(B)       0.90

(C)       1.00

(D)       1.46

                                                                                                            GATE 2006

        Answer:    (C)

 

Two spherical particles have the same outer diameter but are made of different materials The first one (with material density ρ1) is solid, whereas the second (with material density ρ2) is a hollow sphere with the inner shell diameter equal to half the outer diameter. If both the spheres have the same terminal velocity in any fluid, then the ratio of their material densities, ρ21, is

(A)       1

(B)       8/7

(C)       2

(D)       8

                                                                                                            GATE 2006

    Answer:    (B)

 

The mixing of rubber latex solution was studied in an unbaffled mixer in the laboratory. The mixer was equipped with a six blade turbine impeller. A tyre company scales this process up using a baffled tank. The baffled tank has 3 times the diameter of the lab scale mixer. It uses the same type of impeller operated at the same speed. The relevant shape factors are also the same. Assuming that laminar conditions prevail in both cases, the power requirement in the industrial scale mixer

(A)       is 3 times that of the lab scale mixer

(B)       is 9 times that of the lab scale mixer

(C)       is 27 times that of the lab scale mixer

(D)       cannot be estimated reliably due to the presence of baffles

                                                                                                GATE 2006

Answer:          (C)

 

Let dh be the hydrodynamic entrance length for mercury in laminar flow in a pipe under isothermal conditions. Let dt, be its thermal entrance length under fully developed hydrodynamic conditions. Which ONE of the following is TRUE?

            (A)       dh > dt

            (B)       dh < dt

            (C)       dh = dt

            (D)       dh < dt  only if the pipe is vertical

                                                                                                                        GATE 2006

Answer:          (A)

 

The Boussinesq approximation for the fluid density in the gravitational force term is given by ONE of the following (ρref is the fluid density at the reference temperature Tref, and β is the thermal coefficient of volume expansion at Tref)

            (A)             ρ = ρref + Tref β(ρ - ρref)

            (B)              ρ = ρref - Tref β(ρ - ρref)

            (C)              ρ = ρref - Tref β(T - Tref)

            (D)             ρ = ρref - Tref (ρ - ρref)+ ρref(T - Tref)/ Tref

                                                                                                                  GATE 2006

Answer:          (C)

 

If the frequency of the stirrer in a mixing tank is increased by a factor of 2 while all other parameters are kept constant, by what factor is the power requirement increased at high Reynolds number?

(A)             4

(B)              8

(C)              16

(D)             32

                                                                                                      GATE 2005

Answer:          (B)

 

Match the following types of fluid (in group I) with their respective constitutive relations (in group II), where τ is the stress and ϒ is the strain rate

GATE 2005

(A)             P-I, Q-IV

(B)              P-IV, B-I

(C)              P-II, Q-III

(D)             P-III, Q-II

                                                                                                      GATE 2005

Answer:          (D)

 

For turbulent flow past a flat plate, when no form drag is present, the friction factor and the Chilton-colburn factor JD are related as

(A)             f and JD cannot be related

(B)              f is equal to JD

(C)              f is greater than JD

(D)             f is less than JD

                                                                                                      GATE 2005

Answer:          (C)

 

A dam of width 50 m is used to hold water in a reservoir. If the water height is 10 m from the bottom of the dam, what is the total force F acting on the dam due to the water? Assume g = 10 m/s2 and the fluid density is 1000 kg/m3

(A)             F = 12.5×106 N

(B)              F = 25×106 N

(C)              F = 50×106 N

(D)             F = 5×106 N

                                                                                                      GATE 2005

Answer:          (B)

 

The relation between the stress and the strain rate (dux/dy) for the rapid flow of granular material is given by τ = B (dux/dy)2 where B is a constant. If M, L, and T are the mass, length and time dimension respectively, what is the dimension of the constant B?

(A)             ML-1T-1

(B)              ML-2T-2

(C)              MT-1

(D)             ML-1

                                                                                                      GATE 2005

Answer:          (D)

 

Common statement for the next two questions

Two tanks A and B of cross sectional area 1 m2 each, contain a fluid of density 1000 kg/m3 and viscosity 1 kg/(m.S). The tanks are connected by a pipe of diameter 0.02 m and length 1 m, and check valve at the bottom. Assume that the flow is laminar and there is no friction in the check valve. In the initial state, the height of the fluid in the tank A is 6 m and the height of the fluid in tank B is 2 m (as shown in the figure below). The check valve is opened and the fluid flows from tank A to tank B till the levels in the two tanks are equal in the final state. Assume g = 10 m/s2 in the calculations.

GATE 2005

What is the average fluid velocity in the pipe as soon as the valve is opened?

(A)             0.25 m/s

(B)              0.5 m/s

(C)              1 m/s

(D)             2 m/s

                                                                                                      GATE 2005

Answer:          (B)

 

What is the total energy loss between the initial and final states due to the fluid flow?

(A)             2×104 J

(B)              16×104 J

(C)              8×104 J

(D)             4×104 J

                                                                                                      GATE 2005

Answer:          (D)

 

What is terminal velocity in m/s, calculated from stokes law for a particle of diameter 0.1×10-3 m, density 2800 kg/m3 settling in water of density 1000 kg/m3 and viscosity 10-3 kg/(m.s)? (Assume g =10 m/s2)

(A)             2×10-2

(B)              4×10-3

(C)              10-2

(D)             8×10-3

                                                                                                      GATE 2005

Answer:          (C)

 

Common statement for the next two questions

A balloon of mass 0.01 kg is charged with hydrogen to a pressure of 102 KPa and released from the ground level. During its noise the hydrogen is permitted to escape from the balloon in order to maintain a constant differential pressure of 2 KPa under which condition the diameter of the balloon remains at 0.4 m. As this balloon rises it is assumed that the temperature in and around the balloon remains constant at 273 K. Further, the inertia of the balloon and the air resistance due to the rising balloon may be neglected. Assume that the density of air at 273 K is 1.2733 kg/m3, the average molecular weight of air is 28.9, the atmospheric pressure is 100 KPa and the acceleration due to gravity is 10 m/s2.

 

Select the correct value of the upward thrust (in N) expressed in terms of outside pressure P which is expressed in Pa

(A)             10.06×107 P – 0.0122

(B)              3.97×10-6 P – 0.1006

(C)              15.03×10-7 P – 0.0534

(D)             8.08×10-6 P – 0.1362

                                                                                                      GATE 2005

Answer:          (B)

 

Select the value of the outside pressure P in Pa for which there will be no force on the balloon?

(A)             25340

(B)              35530

(C)              12130

(D)             16860

                                                                                                      GATE 2005

Answer:          (A)


Prev        Next

No comments:

Post a Comment