Chapter 7

Question 1

Thickness of boundary layer equation incompressible SS over flat surface laminar BL

Answer 1

5.0x/√Rex

Question 2

equation for kinematic viscocity

Answer 2

μ/ρ

Question 3

What parameters does h depend on?

Answer 3

properties of fluid, velocity of flow, temp of fluid

Question 4

alpha

Answer 4

k/ρcp

Question 5

What is the meaning of the nusselt number

Answer 5

measure of the convection heat transfer occurring at the surface

Question 6

Definition of a streamline

Answer 6

family of curves that are instantaneously tangent to the velocity vector of the flow

Question 7

T* formula

Answer 7

T-Ts/Tinf-Ts

Question 8

What is external flow?

Answer 8

Flow where the boundary layers develop freely.

Question 9

What is an empirical heat or mass transfer coefficient? (How is it obtained?)

Answer 9

Experimentally through lab procedures.

Question 10

What are the dimensionless parameters for forced convection?

Answer 10

Nu, Re, Pr

Sh, Re, Sc

Question 11

As x and ν increase, 𝛿 _______.

Answer 11

Increases : 𝛿=5/√(u∞/νx)

Question 12

As u∞ increase, 𝛿 _______.

Answer 12

Decreases : 𝛿=5/√(u∞/νx)

Question 13

Film Temperature, Tf equation

Answer 13

Tf= (Ts+T∞)/2

Question 14

How do local heat and mass convection coefficients with distance from the leading edge?

Answer 14

Decreases: hₓ=Nuₓk/x

Question 15

What assumptions about the flow are made in chapter 7?

Answer 15

Low-speed
Forced convection
No phase change within the fluid
Steady
Incompressible 
Laminar Flow 
Constant Fluid Properties
Negligible Viscous Dissipation

Question 16

How is local heat transfer from the surface affected by an unheated starting length?

Answer 16

The heat transfer increases:
Nuₓ=(Nuₓ|ξ=0)/[1-(ξ/x)⁹/¹⁰]¹/⁹
denominator gets smaller, Nuₓ gets bigger, hₓ gets bigger, so q gets bigger.

Question 17

Compared to laminar flow, the turbulent boundary layer growth is ________.

Answer 17

Faster.

Question 18

After the forward stagnation point of a cylinder, the pressure _______ with increasing x.
(Fig. 7.6)

Answer 18

Decreases.