Chapter 6 Flashcards
Cf Definition and Equation
Local friction coefficient and τs/ρuinf^2/2
Equation for shear stress
τs=µ*du/dy @y=0
qs’’ defintion and formula
surface heat flux and -kfdT/dy @Y=0
Newtons law of cooling
qs’‘=h(Ts-T∞)
μ name and meaning
mu and dynamics viscosity
Where is the velocity boundry layer located.
Underneath the free stream
what is delta in terms of the free stream.
The y distance from the surface where the free stream is located
kF
conductivity of fluid at surface ie no velocity still due to no slip condition
surface heat flux formula
qs’’=-kf*dT/dy @y=0
What is the driving force for conduction and convection
Temperature Difference
Thermal Boundry Layer
Layer of the fluid flow were Temperature Gradient exists
Analogy between shear stress and surface flux.
Both happen @y=0, and a coefficient time the derivative they have respect too
Equation for heat flux due to convection
qs’‘=h*(Ts-Tinf)
Equation for h
-KfdT/dy/(Ts-Tinf)
Are the thicknesses of the thermal boundary layer and the velocity boundary layer the same
no
How is heat transferred inside the boundary layer and outside the boundary layer?
The heat is transferred inside the boundary layer by conduction due to low velocity and by convection outside the boundary layer by convection.
Driving force of mass transfer?
Delta C aka Difference in concentration
NA’’ meaning and units aka
molar Flux kmol/m^2*s Ficks Law
NA’’ formula
-DAB dCA/dy
C
molar concentration
D term and meaning
Binary Diffusion coefficient
hm
convection mass transfer coefficient
n’’ and units
mass flux kg/s*m^2
h definition and equation
heat transfer coefficient h=-kfdT/dy/Ts-Tinf
hm definition and equation
convection mass transfer coefficient -DAB dCA/dy/CAs-CAinf
Reynolds number definition and equation
dimensionless parameer which defines were turbulent flow beigns. ρu(inf)x/μ
Mach number definition and equation
M= v
Prandt Number
Ratio of momentum and thermal diffusivity-Pr=v/α The kinematic viscosity of a fluid in correlation with the thermal conductivity
μ meaning and definition
dymanic viscocity -This represents the ratio between shear stress to shear strain.
v
kinematic viscocity-This represents the ratio between dynamic viscosities to density. mu/rho
On a isothermal flat plate as the distance of x increases what happens to the gradient? and why?
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.
Nusselt Number equation and meaning
hL/kf, ratio of convection to conduction heat transfer
ν
kinematic viscocity
hm equation
(-Dab dCA/dy)/(Cas-Cainf)
viscous sublayer meaning and mode of heat transfer
flow just above the plate were flow is nearly linear and dominated by diffusion turbulent region
incompresable meaning
constant density
Schmidt Number formula and meaning
v/DAB ratio of momentum and mass diffusivities
Sherwood Number
hmL/DAB and ratio of convective mass transfer to the diffusive mass transfer
Lewis Number Definition and formula.
Provides the measure of the convection mass transfer occurring at the surface. Ratio of thermal and mass diffusivities. α/Dab
Two formulas for NA’’ s
-DAB*dCa/dy @y=o
hm*(Ca,S-Ca,∞)
formula for hm
(-DABdCa/dy)/(hm(Ca,S-Ca,∞)
