ME 322 Lecture

Review the thermal form of the steady flow energy equation. Define enthalpy and density of moist air.

Define humidity ratio and relative humidity. Consider a thought experiment on liquid-vapor equilibrium of saturated pure substances. Consider another thought experiment on the meaning of the saturated conditions for a moist air mixture. Define enthalpy of the moist air mixture.

Begin discussion of properties of moist air. Handed out a worksheet on calculation of humidity ratio when relative humidity is given.

Finish discussion of Kay's Rule. Present formulas for internal energy and enthalpy of mixtures (both extensive and specific).

p-v-T behavior of gas mixtures. Dalton's Law of additive pressures. Amagat's Law of additive volumes. Kay's rule for generalized compressibility

Begin discussion of gas mixtures, following the notation and order of presentation in the textbook.

Presented solution to problem 11.47 from the textbook

Resumed presentation of isentropic flow in ducts with varying area. Presented Example 11.5 and 11.6 from the textbook

Introduction to compressible flow: Speed of sound of an ideal gas, Mach number, ideal gas relationships for compressible isentropic flow.

Introduction to compressible flow: review ideal gas properties, isentropic processes of ideal gases

Class discussion involved discussion of blower designs. I also worked halfway through the lecture slides that can be downloaded from web page for the lecture notes.

The first class period focused on discussion of a simple model of pump performance. This follows the discussion in section 12.3 and 12.4 of the textbook.

Lecture continued with a discussion of the pump curve calculation exercise. Using the data from the exercise we reasoned about the general shape of the pump curve. I presented my solution to the exercise and discussed the shape of the pump curves.

Lecture began with a discussion of differences between positive displacement pumps and turbo-machine pumps. The class then worked on an exercise to convert measurements of pump performance to a pump curve h = f(Q)

I announced the midterm and discussed the content. Check the "Exams" web page and the "Notes" web page for more information. I described boundary layers in the presence of external pressure gradients.

Lecture 9, part b, in ME 322, Portland State University, Winter 2007

Finish solution to problem 9.13 from the book. Describe features of turbulent boundary layer. Present tables and graphs for viscous shear on flat plate boundary layers.

Hand back Quiz 1 and discuss it. Finish discussion of von Karman Momentum Integral. Present overall results of exact solution by Blasius. Begin presenting solution to Problem 9.13 from the book.

Begin derivation of von Karman integral equation for the boundary layer.

Introduce in-class exercise involving boundary layer calculations for a sheet of plywood attached to the roof of a car.

Comments on Quiz 1. Define boundary layer thickness and derive the formula for displacement thickness. Scale analysis of boundary to determine the consequences "thin-ness".

Derivation of equations for calculating head loss in non-circular ducts. Description of the three basic types of pipe flow calculation: head loss, flow rate, and pipe sizing. We also worked through an example problem involving flow between two tanks.

Calculation of head loss in straight sections of round pipes

Review of conditions for pipe flow analysis: laminar versus turbulent flow; fully-developed versus developing flow; viscous flow in straight sections versus loss in fittings. Derive and solve the ODE for the velocity profile in fully-developed laminar flow in a round pipe. Obtain the formula for average velocity and the formula relating flow rate to pressure drop. Generalize the results to turbulent flow with dimensional analysis and an overview of the physics of the turbulent velocity profile. Introduce the Darcy friction factor and the Moody chart.