Transport of Heat, Mass and Momentum

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Questions and Answers

What property of a gas is the kinematic viscosity (ν) a function of?

Mass

Pressure

Density (correct)

Temperature

In the context of momentum transfer, what is the coefficient of dynamic viscosity (μ) defined as?

Molecular energy flux

Velocity gradient times mean free path

Kinematic viscosity divided by mean density (correct)

Density divided by velocity

What determines the direction of the flux of momentum in relation to a surface?

Pressure gradient

Temperature gradient

Density gradient

Velocity gradient (correct)

What property of air is the thermal diffusivity (κ) related to?

Viscosity Signup and view all the answers

In heat transfer, what does the rate of transfer of heat depend on?

Gradient of heat content per unit volume Signup and view all the answers

What is the average distance a molecule travels between collisions known as?

Mean free path Signup and view all the answers

Which process is responsible for the transfer of heat in micrometeorology?

Conduction Signup and view all the answers

What is the phenomenon of viscosity in moving air due to?

Shearing stress Signup and view all the answers

Which factor is responsible for increasing velocity of air flow over a solid surface?

Bulk motion Signup and view all the answers

What does the kinetic theory of gases help determine?

Mean free path Signup and view all the answers

Which process in micrometeorology involves the diffusion of water vapor and other gases?

Mass transfer Signup and view all the answers

What is the symbol used to represent the vertical gradient of a property in the context of the general transfer equation?

dP/dz Signup and view all the answers

The downward flux of a property P in the general transfer equation depends on which of the following factors?

All of the above Signup and view all the answers

The mean square velocity of molecular motion in an ideal gas is given by which formula according to the information provided?

$v^{2} = 3p/\rho$ Signup and view all the answers

What property is represented by P in the general transfer equation?

Pressure Signup and view all the answers

In the context of momentum transfer, what does viscosity represent?

Resistance to momentum flow Signup and view all the answers

What factor determines the number of carriers moving towards one face of a cube at any instant in the general transfer equation?

Velocity v Signup and view all the answers

Study Notes

Gas Properties and Viscosity

Kinematic viscosity (ν) is dependent on the dynamic viscosity (μ) and density (ρ) of a gas, expressed as ν = μ/ρ.
The coefficient of dynamic viscosity (μ) defines the internal resistance of a fluid to flow and is a measure of momentum transfer relative to the velocity gradient in the fluid.

Momentum Transfer

The direction of the flux of momentum relative to a surface is determined by the momentum gradient which indicates the flow direction.

Thermal Properties

Thermal diffusivity (κ) is related to the thermal conductivity of air, heat capacity, and density, signifying how rapidly heat spreads through the material.
The rate of heat transfer in heat transfer processes depends on the temperature gradient, area of transfer, and thermal conductivity of the material.

Molecular Motion

The average distance a molecule travels between collisions is known as the mean free path.
Viscosity in moving air arises from intermolecular friction and the interactions among air particles during movement.

Air Flow Dynamics

Increased velocity of air flow over a solid surface is caused by a decrease in surface roughness or obstacles that disrupt airflow, leading to laminar flow conditions.

Kinetic Theory and Transfer Processes

The kinetic theory of gases is significant in determining properties like pressure, temperature, and volume of gases based on molecular behavior.
In micrometeorology, the process that involves the diffusion of water vapor and other gases is related to turbulent exchange in the boundary layer.

General Transfer Equation

The symbol used to represent the vertical gradient of a property in the general transfer equation is typically denoted as ∂P/∂z.
The downward flux of a property P in the general transfer equation depends on the gradient of that property, the diffusion coefficient, and the velocity field in the surrounding area.
The mean square velocity of molecular motion in an ideal gas can be expressed using the formula: ( \langle v^2 \rangle = \frac{3kT}{m} ), where ( k ) is the Boltzmann constant, ( T ) is the temperature, and ( m ) is the mass of the gas molecules.

Momentum Transfer Representation

In the context of momentum transfer, viscosity represents the resistance that materials experience when subjected to shear stress.
The number of carriers moving towards one face of a cube at any instant in the general transfer equation is determined by the concentration gradient and the diffusion coefficient of the property in question.

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Description

This quiz covers topics related to the transport of heat, mass, and momentum in APHY 140 Lecture 5. It includes the general transfer equation, molecular transfer processes (momentum, viscosity, heat, thermal conductivity, mass transfer, and diffusivity), diffusion coefficients, and diffusion of particles through Brownian motion.