Notes on Chapter 5: Mass and Energy - Analysis of Control Volumes (copy)

Conservation of Mass

States that mass cannot be created or destroyed during a process.

Steady-Flow Process

A process in which properties within the boundary of the system remain constant over time.

Unit-Mass Basis Energy Balance Equation

e_{in} - e_{out} = \Delta e_{sys},\, kJ/kg where inputs and outputs refer to energy on a per unit mass basis.

Unit-Time Basis Mass Balance Equation

m_{in} - m_{out} = \Delta m_{sys},\, kg/s representing the change in mass per time.

Flow Work

The work required to push mass into or out of a control volume necessary for continuous flow.

Mass Flow Rate Definition

\dot{m} = \frac{m}{t},\, kg/s which represents the mass of fluid passing through a section per unit time.

Relationship Between Mass & Volume Flow Rate

V = \frac{m}{\nu} where \nu is the specific volume.

Incompressible Flow

A flow in which the density remains constant, simplifying mass conservation relations.

Total Energy of a Flowing Fluid

E = \frac{h}{m} which includes internal and flow energy components.

Energy Balance for Nozzles

\Delta h + \Delta ke = 0, indicating that work and heat transfer are negligible.

Purpose of Turbines

Used to produce work by converting fluid energy into mechanical energy.

Ideal Gas Equation

u = RT where R is the gas constant and T is the temperature.

Heat Exchangers

Devices that facilitate heat transfer between two fluid systems without mixing.

Mixing Chambers

Locations where different fluid streams, like hot and cold water, combine.

Conservation of Energy Principle

States that energy input minus energy output results in a change in energy within a system.

Energy Transport by Mass

Process defining the movement of energy through the flow of mass in a system.

Assumptions for Steady-Flow Devices

Include no losses, nearly incompressible fluid, and steady flow conditions.

Example of Mass Balance

If a system has 10 kg entering and 4 kg exiting, the change in mass is 6 kg.

Energy Balance General Equation

\Delta E_{sys} = \sum Q_{in} - \sum Q_{out} + \sum \dot{m}{in} - \sum \dot{m}{out} which represents the overall energy accounting.