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In natural convection, the fluid motion ...

In natural convection, the fluid motion is caused due to density difference produced by temperature gradient.
Statement II: In forced convection, the fluid is forced to flow along the solid surface by means of fans or pumps.

A

(a)Statement I is true, Statement II is true and Statement II is the correct explanation for statement I.

B

(b)Statement I is true, statement II is true and statement II NOT the correct explanation for Statement I

C

(c)Statement I is true, Statement II is false.

D

(d)Statement I is false, statement II is true.

Text Solution

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The correct Answer is:
To solve the question, we need to analyze both statements regarding natural convection and forced convection. ### Step 1: Understand Statement I **Statement I:** In natural convection, the fluid motion is caused due to density difference produced by temperature gradient. - **Explanation:** Natural convection occurs when a fluid is heated, causing it to become less dense and rise, while cooler, denser fluid sinks. This creates a circulation pattern driven by the temperature gradient. ### Step 2: Understand Statement II **Statement II:** In forced convection, the fluid is forced to flow along the solid surface by means of fans or pumps. - **Explanation:** Forced convection involves external forces (like fans or pumps) that move the fluid over a surface, enhancing heat transfer. This does not rely on density differences but rather on mechanical means to induce fluid motion. ### Step 3: Determine the Truth of Each Statement - **Truth of Statement I:** True. This is a correct definition of natural convection. - **Truth of Statement II:** True. This is a correct definition of forced convection. ### Step 4: Analyze the Relationship Between the Statements - **Explanation of Relationship:** While both statements are true, they describe different phenomena. Statement II does not explain Statement I; they are independent definitions of natural and forced convection. ### Step 5: Conclusion - Both statements are true, but Statement II is not a correct explanation for Statement I. Therefore, the answer is that both statements are true, but Statement II does not explain Statement I. ### Final Answer - Both statements are true, but Statement II is not a correct explanation for Statement I.
To solve the question, we need to analyze both statements regarding natural convection and forced convection. ### Step 1: Understand Statement I **Statement I:** In natural convection, the fluid motion is caused due to density difference produced by temperature gradient. - **Explanation:** Natural convection occurs when a fluid is heated, causing it to become less dense and rise, while cooler, denser fluid sinks. This creates a circulation pattern driven by the temperature gradient. ### Step 2: Understand Statement II ...
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The word fluid means a substance having particles which readily of its magnitude (a small shear stress, which may appear to be of negligible will cause deformation in the fluid). Fluids are charactrised by such properties as density. Specific weight, specific gravity, viscosity etc. Density of a substance is defined as mass per unit volume and it is denoted by. The specific gravity represents a numerical ratio of two densities, and water is commonly taken as a reference substance. Specific gravity of a substance in written as the ratio of density of substance to the density of water. Specific weight represents the force exerted by gravity on a unit volume of fluid. It is related to the density as the product of density of a fluid and acceleration due to gravity. Viscosity is the most important and is recognized as the only single property which influences the fluid motion to a great extent. The viscosity is the property by virtue of which a fluid offers resistance to deformation under the influenece if shear force. The force between the layers opposing relative motion between them are known as forces of viscosity. When a boat moves slowly on the river remains at rest. Velocities of different layers are different. Let v be the velocity of the level at a distance y from the bed and V+dv be the velocity at a distance y+dy . The velocity differs by dv in going through a distance by perpendicular to it. The quantity (dv)/(dy) is called velocity gradient. The force of viscosity between two layers of a fluid is proportional to velocity gradient and Area of the layer. F prop A & F prop (dv)/(dy) F= -etaA(dv)/(dy) ( -ve sign shown the force is frictional in nature and opposes relative motion. eta coefficient of dynamic viscosity Shear stress (F)/(A)= -eta(dv)/(dy) and simultaneously kinematic viscosity is defined as the dynamic viscosity divided by the density. If is denoted as v . The viscosity of a fluid depends upon its intermolecular structure. In gases, the molecules are widely spaced resulting in a negligible intermolecular cohesion, while in liquids the molecules being very close to each other, the cohesion is much larger with the increases of temperature, the cohesive force decreases rapidly resulting in the decreases of viscosity. In case of gases, the viscosity is mainly due to transfer of molecular momentum in the transerve direction brought about by the molecular agitation. Molecular agitation increases with rise in temperature. Thus we conclude that viscosity of a fluid may thus be considered to be composed of two parts, first due to intermolecuar cohesion and second due to transfer of molecular momentum. If the velocity profile is given by v=(2)/(3)y-y^(2)v is velocity in m//sec y is in meter above the bad. Determine shear stress at y=0.15m , & eta=0.863 Ns//m^(2)

The word fluid means a substance having particles which readily of its magnitude (a small shear stress, which may appear to be of negligible will cause deformation in the fluid). Fluids are charactrised by such properties as density. Specific weight, specific gravity, viscosity etc. Density of a substance is defined as mass per unit volume and it is denoted by. The specific gravity represents a numerical ratio of two densities, and water is commonly taken as a reference substance. Specific gravity of a substance in written as the ratio of density of substance to the density of water. Specific weight represents the force exerted by gravity on a unit volume of fluid. It is related to the density as the product of density of a fluid and acceleration due to gravity. Viscosity is the most important and is recognized as the only single property which influences the fluid motion to a great extent. The viscosity is the property by virtue of which a fluid offers resistance to deformation under the influenece if shear force. The force between the layers opposing relative motion between them are known as forces of viscosity. When a boat moves slowly on the river remains at rest. Velocities of different layers are different. Let v be the velocity of the level at a distance y from the bed and V+dv be the velocity at a distance y+dy . The velocity differs by dv in going through a distance by perpendicular to it. The quantity (dv)/(dy) is called velocity gradient. The force of viscosity between two layers of a fluid is proportional to velocity gradient and Area of the layer. F prop A & F prop (dv)/(dy) F= -etaA(dv)/(dy) ( -ve sign shown the force is frictional in nature and opposes relative motion. eta coefficient of dynamic viscosity Shear stress (F)/(A)= -eta(dv)/(dy) and simultaneously kinematic viscosity is defined as the dynamic viscosity divided by the density. If is denoted as v . The viscosity of a fluid depends upon its intermolecular structure. In gases, the molecules are widely spaced resulting in a negligible intermolecular cohesion, while in liquids the molecules being very close to each other, the cohesion is much larger with the increases of temperature, the cohesive force decreases rapidly resulting in the decreases of viscosity. In case of gases, the viscosity is mainly due to transfer of molecular momentum in the transerve direction brought about by the molecular agitation. Molecular agitation increases with rise in temperature. Thus we conclude that viscosity of a fluid may thus be considered to be composed of two parts, first due to intermolecuar cohesion and second due to transfer of molecular momentum. Viscosity of liquids

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