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Heat Transfer > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Cf Definition and Equation

A

Local friction coefficient and τs/ρuinf^2/2

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2
Q

Equation for shear stress

A

τs=µ*du/dy @y=0

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3
Q

qs’’ defintion and formula

A

surface heat flux and -kfdT/dy @Y=0

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4
Q

Newtons law of cooling

A

qs’‘=h(Ts-T∞)

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5
Q

μ name and meaning

A

mu and dynamics viscosity

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6
Q

Where is the velocity boundry layer located.

A

Underneath the free stream

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7
Q

what is delta in terms of the free stream.

A

The y distance from the surface where the free stream is located

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8
Q

kF

A

conductivity of fluid at surface ie no velocity still due to no slip condition

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9
Q

surface heat flux formula

A

qs’’=-kf*dT/dy @y=0

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10
Q

What is the driving force for conduction and convection

A

Temperature Difference

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11
Q

Thermal Boundry Layer

A

Layer of the fluid flow were Temperature Gradient exists

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12
Q

Analogy between shear stress and surface flux.

A

Both happen @y=0, and a coefficient time the derivative they have respect too

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13
Q

Equation for heat flux due to convection

A

qs’‘=h*(Ts-Tinf)

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14
Q

Equation for h

A

-KfdT/dy/(Ts-Tinf)

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15
Q

Are the thicknesses of the thermal boundary layer and the velocity boundary layer the same

A

no

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16
Q

How is heat transferred inside the boundary layer and outside the boundary layer?

A

The heat is transferred inside the boundary layer by conduction due to low velocity and by convection outside the boundary layer by convection.

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17
Q

Driving force of mass transfer?

A

Delta C aka Difference in concentration

18
Q

NA’’ meaning and units aka

A

molar Flux kmol/m^2*s Ficks Law

19
Q

NA’’ formula

A

-DAB dCA/dy

20
Q

C

A

molar concentration

21
Q

D term and meaning

A

Binary Diffusion coefficient

22
Q

hm

A

convection mass transfer coefficient

23
Q

n’’ and units

A

mass flux kg/s*m^2

24
Q

h definition and equation

A

heat transfer coefficient h=-kfdT/dy/Ts-Tinf

25
Q

hm definition and equation

A

convection mass transfer coefficient -DAB dCA/dy/CAs-CAinf

26
Q

Reynolds number definition and equation

A

dimensionless parameer which defines were turbulent flow beigns. ρu(inf)x/μ

27
Q

Mach number definition and equation

A

M= v

28
Q

Prandt Number

A

Ratio of momentum and thermal diffusivity-Pr=v/α The kinematic viscosity of a fluid in correlation with the thermal conductivity

29
Q

μ meaning and definition

A

dymanic viscocity -This represents the ratio between shear stress to shear strain.

30
Q

v

A

kinematic viscocity-This represents the ratio between dynamic viscosities to density. mu/rho

31
Q

On a isothermal flat plate as the distance of x increases what happens to the gradient? and why?

A

It must decrease. The gradient is classified as Dt/dy. As x increase the height of the free stream increase while Dt is constant so the numerator becomes larger hence the gradient becomes smaller.

32
Q

Nusselt Number equation and meaning

A

hL/kf, ratio of convection to conduction heat transfer

33
Q

ν

A

kinematic viscocity

34
Q

hm equation

A

(-Dab dCA/dy)/(Cas-Cainf)

35
Q

viscous sublayer meaning and mode of heat transfer

A

flow just above the plate were flow is nearly linear and dominated by diffusion turbulent region

36
Q

incompresable meaning

A

constant density

37
Q

Schmidt Number formula and meaning

A

v/DAB ratio of momentum and mass diffusivities

38
Q

Sherwood Number

A

hmL/DAB and ratio of convective mass transfer to the diffusive mass transfer

39
Q

Lewis Number Definition and formula.

A

Provides the measure of the convection mass transfer occurring at the surface. Ratio of thermal and mass diffusivities. α/Dab

40
Q

Two formulas for NA’’ s

A

-DAB*dCa/dy @y=o

hm*(Ca,S-Ca,∞)

41
Q

formula for hm

A

(-DABdCa/dy)/(hm(Ca,S-Ca,∞)

Heat Transfer (8 decks)

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