Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/µ) 0.8 (CP .µ/k) 0.4 . This is valid for the value of NRe equal to (A) < 2100 (B) 2100-4000 (C) > 4000 (D) > 10000

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is

given by

h = 0.023 (K/D) (DVρ/µ)

0.8

(CP

.µ/k)

0.4

. This is valid for the value of NRe equal

to

(A) < 2100

(B) 2100-4000

(C) > 4000

(D) > 10000

by

1 Answer

Answer :

(D) > 10000

by

Related questions

Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8 . Pr n , is not valid, if the value of (A) n = 0.4 is used for heating (B) n = 0.3 is used for cooling (C) Reynolds number for the flow involved is > 10000 (D) Reynolds number for the flow involved is < 2100

Description : Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8 . Pr n , is not valid, if the value of (A) n = 0.4 is used for heating (B) n = 0.3 is used for cooling (C) Reynolds number for the flow involved is > 10000 (D) Reynolds number for the flow involved is < 2100

Last Answer : (D) Reynolds number for the flow involved is < 2100

A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Description : A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Last Answer : (A) 7

Prandtl number is given by (A) CP µ/a (B) hD/k (C) CP µ/k (D) µ/h CP

Description : Prandtl number is given by (A) CP µ/a (B) hD/k (C) CP µ/k (D) µ/h CP

Last Answer : (C) CP µ/k

The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

Description : The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Description : The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient ... pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Last Answer : (B) D-0.2

A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co￾efficient for turbulent flow conditions is proportional to (A) d 0.8 (B) d -0.2 (C) d -1 (D) d -1.8

Description : A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co￾efficient for turbulent flow conditions is proportional to (A) d 0.8 (B) d -0.2 (C) d -1 (D) d -1.8

Last Answer : (B) d -0.2

What is Nusselt number? (A) CP . µ/k (B) hD/k (C) h. CP /µ (D) CP . µ/h

Description : What is Nusselt number? (A) CP . µ/k (B) hD/k (C) h. CP /µ (D) CP . µ/h

Last Answer : (B) hD/k

Friction factor for a hydraulically smooth pipe at NRe = 2100 is f1 . If the pipe is further smoothened (i.e., roughness is reduced), the friction factor at the same value of NRe , will (A) Increase (B) Decrease (C) Remain unchanged (D) Increase or decrease depending on the pipe material

Description : Friction factor for a hydraulically smooth pipe at NRe = 2100 is f1 . If the pipe is further smoothened (i.e., roughness is reduced), the friction factor at the same value of NRe , will (A) Increase (B) Decrease (C) Remain unchanged (D) Increase or decrease depending on the pipe material

Last Answer : (A) Increase

Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8

Description : Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is (A) 0.2 (B) 0.4 (C) 0.6 (D) 0.8

Last Answer : (C) 0.6

Stoke's law is valid, when NRe, p is less than (A) 2 (B) 100 (C) 2100 (D) 700

Description : Stoke's law is valid, when NRe, p is less than (A) 2 (B) 100 (C) 2100 (D) 700

Last Answer : (A) 2

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Description : Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Last Answer : (D) Highly turbulent

Pick out the wrong statement. (A) The shear stress at the pipe (dia = D, length = L) wall in case of laminar flow of Newtonian fluids is (D/4L). ∆p (B) In the equation, T. gc = k. (du/dy) n the value of 'n' for pseudoplastic and Dilatant fluid are < 1 and >1 respectively (C) Shear stress for Newtonian fluid is proportional to the rate of shear in the direction perpendicular to motion (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

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Last Answer : (D) With increase in the Mach number >0.6, the drag co-efficient decreases in case of compressible fluids

Joule-Thomson co-efficient which is defined as, η = (∂T/∂P)H = 1/Cp (∂H/∂T)P, changes sign at a temperature known as inversion temperature. The value of Joule-Thomson co-efficient at inversion temperature is (A) 0 (B) ∞ (C) +ve (D) -ve

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Last Answer : (A) 0

(∂T/∂P)H is the mathematical expression for (A) Specific heat at constant pressure (Cp) (B) Specific heat at constant volume (Cv) (C) Joule-Thompson co-efficient (D) None of these

Description : (∂T/∂P)H is the mathematical expression for (A) Specific heat at constant pressure (Cp) (B) Specific heat at constant volume (Cv) (C) Joule-Thompson co-efficient (D) None of these

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Joule-Thomson co-efficient is defined as (A) µ = (∂P/∂T)H (B) µ = (∂T/∂P)H (C) µ = (∂E/∂T)H (D) µ = (∂E/∂P)H

Description : Joule-Thomson co-efficient is defined as (A) µ = (∂P/∂T)H (B) µ = (∂T/∂P)H (C) µ = (∂E/∂T)H (D) µ = (∂E/∂P)H

Last Answer : (B) µ = (∂T/∂P)H

Drag co-efficient for motion of spherical particles in a stationary fluid in the stoke's law range is (A) 24/NRe,P (B) 16/NRe,P (C) 64/NRe,P (D) 48/NRe,P

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Pick out the wrong statement. (A) Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection (B) The ratio NNu /NRe . Npr is called the Stanton number (C) The Peclet number is a measure of the ratio of energy transport by convection to that by conduction (D) The Colburn jH factor for heat transfer is given by Nst Npr

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The overall heat transfer co-efficient for a shell and tube heat exchangerfor clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year ofoperation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co￾efficient at this time is(A) 1200 W/m2.K(B) 894 W/m2.K(C) 333 W/m2.K(D) 287 W/m2.K

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Last Answer : (C) 333 W/m2 .K

The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are (A) Re.Gz (B) Nu, Pr (C) Nu, Pr, Re (D) Nu, Gz

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Last Answer : (D) Nu, Gz

Laminar flow of a Newtonian fluid ceases to exist, when the Reynolds number exceeds (A) 4000 (B) 2100 (C) 1500 (D) 3000

Description : Laminar flow of a Newtonian fluid ceases to exist, when the Reynolds number exceeds (A) 4000 (B) 2100 (C) 1500 (D) 3000

Last Answer : (B) 2100

The Reynolds number for an ideal fluid flow is (A) 4 (B) 2100-4000 (C) 4000 (D) ∞

Description : The Reynolds number for an ideal fluid flow is (A) 4 (B) 2100-4000 (C) 4000 (D) ∞

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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 co-efficient 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

Description : 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 co-efficient is 3k/l'. If the wall temperature ... wall temperature in degree centigrade? (A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Last Answer : (C) 81.25

The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2 .K. At steady state, the temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Description : The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the ... temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Last Answer : (D) 48.7

The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Description : The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by __________ times, when the number of tube passes is increased to 8. (A) 2 0.8 (B) 4 0.8 (C) 4 0.4 (D) 2 0.4

Last Answer : (B) 4 0.8

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

Description : 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

Last Answer : (B) 1/U1 - 1/U2

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

Description : 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

Last Answer : (B) 0.794 h1

Double pipe heat exchangers are preferably useful, when (A) High viscosity liquid is to be cooled (B) Requirement of heat transfer area is low (C) Overall heat transfer co-efficient is very high (D) A corrosive liquid is to be heated

Description : Double pipe heat exchangers are preferably useful, when (A) High viscosity liquid is to be cooled (B) Requirement of heat transfer area is low (C) Overall heat transfer co-efficient is very high (D) A corrosive liquid is to be heated

Last Answer : (B) Requirement of heat transfer area is low

(1/V) (∂V/∂T)Pis the mathematical expression (A) Joule-Thomson co-efficient (B) Specific heat at constant pressure (Cp) (C) co-efficient of thermal expansion (D) Specific heat at constant volume (CV)

Description : (1/V) (∂V/∂T)Pis the mathematical expression (A) Joule-Thomson co-efficient (B) Specific heat at constant pressure (Cp) (C) co-efficient of thermal expansion (D) Specific heat at constant volume (CV)

Last Answer : (C) co-efficient of thermal expansion

Which of the following situations can be approximated to a steady state heat transfer system? (A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at 35°C (B) 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C (C) Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C (D) A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Description : Which of the following situations can be approximated to a steady state heat transfer system? (A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmospheric air at ... flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Last Answer : (B) 10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C

At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe? (A) 0.5 (B) < 0.5 (C) > 0.6 (D) < 0.1

Description : At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe? (A) 0.5 (B) < 0.5 (C) > 0.6 (D) < 0.1

Last Answer : (C) > 0.6

Pick out the wrong statement. (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient (B) In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles (C) S.I. unit of fouling factor is Watt/m2 .°K (D) Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Description : Pick out the wrong statement. (A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient (B) In a shell and tube heat exchanger ... surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

Last Answer : (C) S.I. unit of fouling factor is Watt/m2 .°K

Out of the following four assumptions used in the derivation of theequation for LMTD[LMTD = (∆t1- ∆t2)/ln(∆t1/∆t2)], which one is subject to the largest deviationin practice ?(A) Constant overall heat transfer co-efficient.(B) Constant rate of fluid flow(C) Constant specific heat(D) No partial phase change in the system

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Last Answer : (B) Constant rate of fluid flow

essure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as (A) V1.8 (B) V-0.2 (C) V2.7 (D) V

Description : essure drop (Δp) for a fluid flowing in turbulent flow through a pipe is a function of velocity (V) as (A) V1.8 (B) V-0.2 (C) V2.7 (D) V

Last Answer : (D) V

What is the value of Fanning friction factor f ' for smooth pipe at NRe = 10 6 approximately? (A) 0.003 (B) 0.01 (C) 0.1(D) 0.3

Description : What is the value of Fanning friction factor f ' for smooth pipe at NRe = 10 6 approximately? (A) 0.003 (B) 0.01 (C) 0.1 (D) 0.3

Last Answer : (A) 0.003

Incorrect statement for co-efficient of friction could be that A. The coefficient of friction is denoted by the Greek letter µ. B. The coefficient of friction is directly proportional to the force of friction C. The coefficient of friction is constant even in the conditions of fast slipping and high contact pressure D. The coefficient of friction is inversely proportional to the force pressing the surfaces together

Description : Incorrect statement for co-efficient of friction could be that A. The coefficient of friction is denoted by the Greek letter µ. B. The coefficient of friction is directly proportional to ... D. The coefficient of friction is inversely proportional to the force pressing the surfaces together

Last Answer : The coefficient of friction is constant even in the conditions of fast slipping and high contact pressure

In an extended surface heat exchanger, fluid having lower co-efficient (A) Flows through the tube (B) Flows outside the tubes (C) Can flow either inside or outside the tubes (D) Should not be used as it gives very high pressure drop

Description : In an extended surface heat exchanger, fluid having lower co-efficient (A) Flows through the tube (B) Flows outside the tubes (C) Can flow either inside or outside the tubes (D) Should not be used as it gives very high pressure drop

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The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is(A) 2.36(B) 4.36(C) 120.36(D) Dependent on NRe only

Description : The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is (A) 2.36 (B) 4.36 (C) 120.36 (D) Dependent on NRe only

Last Answer : (B) 4.36

Work required for compression of a gas contained in a cylinder is 7000 kJ. During compression, heat interaction of 3000 kJ causes the surroundings to be heated. Internal energy change of the gas during the compression is __________ kJ. (A) +4000 (B) -4000 (C) 10000 (D) -10000

Description : Work required for compression of a gas contained in a cylinder is 7000 kJ. During compression, heat interaction of 3000 kJ causes the surroundings to be heated. Internal energy change of the gas during the compression is __________ kJ. (A) +4000 (B) -4000 (C) 10000 (D) -10000

Last Answer : (A) +4000

The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) (A) K/h0 (B) 2K/h0 (C) hi /K (D) 2hi /K

Description : The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe) (A) K/h0 (B) 2K/h0 (C) hi /K (D) 2hi /K

Last Answer : (A) K/h0

Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by (A) Eddies current (B) Conduction (C) Convection (D) None of these

Description : Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by (A) Eddies current (B) Conduction (C) Convection (D) None of these

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Pick out the wrong statement. (A) Aromatics have higher specific gravity than paraffins (B) Gross calorific value (GCV) of petrofuels is equal to (12400 - 2100 ρ 2 ) where, ρ is the specific gravity of the fuel at 15.5°C (C) Heavier petrofuels have higher GCV on weight basis (i.e., Kcal/kg) but lower GCV on volume basis (i.e., Kcal/litre) (D) Higher specific gravity of petrofuels means higher C/H ratio

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Last Answer : (C) Heavier petrofuels have higher GCV on weight basis (i.e., Kcal/kg) but lower GCV on volume basis (i.e., Kcal/litre)

Calorific value of coke even gas produced by low temperature carbonisation of coal is about __________ Kcal/Nm3 . (A) 4000 (B) 2500 (C) 6500 (D) 10000

Description : Calorific value of coke even gas produced by low temperature carbonisation of coal is about __________ Kcal/Nm3 . (A) 4000 (B) 2500 (C) 6500 (D) 10000

Last Answer : (C) 6500

Colebrook equation for friction factor in turbulent flow is given by, f -0.5 = -4 loge [(ε/D) + (1.26/NRe √F). It reduces to Nikuradse equation for a value of (ϵ/D) equal to (A) 0(B) 1 (C) ∞ (D) 0.5

Description : Colebrook equation for friction factor in turbulent flow is given by, f -0.5 = -4 loge [(ε/D) + (1.26/NRe √F). It reduces to Nikuradse equation for a value of (ϵ/D) equal to (A) 0 (B) 1 (C) ∞ (D) 0.5

Last Answer : (B) 1

What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Last Answer : (A) 2

Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is (A) 0.1 (B) > 1 (C) < 1 (D) 1

Description : Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is (A) 0.1 (B) > 1 (C) < 1 (D) 1

Last Answer : (A) 0.1

For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are (A) Same (B) Different (C) Never different (D) Linearly related

Description : For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are (A) Same (B) Different (C) Never different (D) Linearly related

Last Answer : (B) Different

Bulk of the convective heat transfer resistance from a hot tube surfaceto 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

Description : Bulk of the convective heat transfer resistance from a hot tube surfaceto 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

Last Answer : (C) Mainly confined to a thin film of fluid near the surface

The co-efficient of discharge of an orificemeter is a function of (A) Reynolds number at the orifice (B) Ratio of orifice dia to pipe dia (C) Both (A) and (B) (D) None of the above parameters, and has a constant value of 0.61

Description : The co-efficient of discharge of an orificemeter is a function of (A) Reynolds number at the orifice (B) Ratio of orifice dia to pipe dia (C) Both (A) and (B) (D) None of the above parameters, and has a constant value of 0.61

Last Answer : (C) Both (A) and (B)